JP6163052B2 - OFDM wave measuring apparatus and program - Google Patents

Description

  The present invention relates to a technique for detecting and measuring signals such as terrestrial digital broadcasting, terrestrial digital audio broadcasting, and multimedia broadcasting, and in particular, reception power of an OFDM (Orthogonal Frequency Division Multiplexing) signal including a pilot signal, and the like. The present invention relates to an OFDM wave measuring apparatus and a program for measuring the frequency.

  2. Description of the Related Art Conventionally, in fields such as terrestrial digital broadcasting, terrestrial digital audio broadcasting, and multimedia broadcasting, apparatuses that extract a pilot signal from an OFDM signal and measure received power, spectrum, delay profile, and the like are known. For example, Patent Document 1 detects a transmission mode and GI (Guard Interval) from a received OFDM signal, performs local frequency correction and sampling frequency correction, and extracts a pilot signal without capturing frame synchronization. An OFDM signal analyzing apparatus for calculating a delay profile is described. Further, Patent Document 2 discloses a delay profile measuring device that extracts a SP (Scattered Pilot) signal from a received OFDM signal and calculates a delay profile based on the SP signal with a larger number of FFT points than before. Is described.

  On the other hand, institutionalization of services and systems utilizing white space is being promoted, and research and development are being actively conducted to promote business development. White space refers to radio waves in a frequency region that is not used geographically and temporally among frequency regions assigned to a specific radio wave service. In a service utilizing this white space, the allowable level of interference from the white space using station to the broadcast wave needs to be equal to or less than thermal noise. For example, the allowable level of interference is I (Interference) / N (Noise) = − 10 dB. As described above, there is a need for a technique for measuring a low level signal equal to or lower than thermal noise.

  Therefore, an OFDM wave measuring apparatus disclosed in Patent Document 3 is known as an apparatus for measuring a low level signal equal to or lower than thermal noise. This OFDM wave measuring apparatus detects the position of an effective symbol by guard interval correlation after performing loop filter processing or moving average processing in a predetermined number of symbol units on the time axis, and then performs FFT (Fast Fourier Transform: A pilot symbol is extracted by synchronously adding carrier symbols obtained by performing (Fast Fourier Transform) every predetermined number of symbols, and received power and the like are calculated. On the other hand, since this OFDM wave measuring apparatus performs loop filter processing or moving average processing and synchronous addition processing on the time axis, if there is a clock error or frequency error between the transceivers, the received power etc. It cannot be calculated with high accuracy. Therefore, in Patent Document 3, as a rough correction, the clock error is calculated from the value of the guard interval correlation, and in order to further improve the accuracy, the number of calculation symbols in which the power of the SP signal after synchronous addition becomes a peak value on the time axis is disclosed. An example is shown in which received power and the like are calculated using a table or a calculation formula for converting a frequency error from.

JP 2002-335226 A JP 2007-28367 A JP 2012-253553 A

  In the above-mentioned patent document 3, addition in symbol units on the time axis is performed to calculate a clock error and a frequency error from the value of the guard interval correlation, and further, a calculated symbol in which the power of the SP signal has a peak value on the frequency axis A technique for calculating a frequency error from a number is shown. In this method, the absolute value of the frequency error is calculated, but the direction (positive or negative) of the frequency error is not determined.

  In order to determine the direction of the frequency error, the number of calculated symbols at which the SP signal power has a peak value when the frequency error is reflected in the positive direction or the negative direction is calculated, and the direction in which the number of calculated symbols at the peak value is large Is determined as the direction of frequency error.

  However, the method for determining the direction of the frequency error has a problem that the amount of calculation increases and the processing load increases. For this reason, it has been desired that a highly accurate frequency error including positive and negative directions can be calculated with a small amount of calculation and a low load.

  Also, in the above-mentioned Patent Document 3, the frequency error is calculated from the number of calculated symbols where the power of the SP signal has a peak value on the frequency axis, and the received power and the like are calculated using a table for converting the absolute value of the frequency error and the received power. A method for obtaining the value is also shown. With this method, it is not necessary to determine the direction of the frequency error.

  Further, the clock error can be calculated by adding symbol units on the time axis and using the value of the guard interval correlation, but there is a problem that the accuracy is insufficient when the signal power is low.

  As described above, in the conventional OFDM wave measuring apparatus, the accuracy of the calculated frequency error and clock error is insufficient. Therefore, by improving the detection accuracy of the frequency error and clock error, the OFDM wave signal is further improved. It has been desired to measure with high accuracy.

  Therefore, the present invention has been made to solve the above-mentioned problems, and the object of the present invention is to calculate a highly accurate frequency error and clock error even when the signal power is at a low level, and to generate an OFDM wave signal. It is an object to provide an OFDM wave measuring apparatus and program capable of accurately measuring the frequency.

  To achieve the above object, an OFDM wave measuring apparatus according to the present invention receives an OFDM wave including a pilot signal, extracts the pilot signal, and measures the signal of the OFDM wave. The orthogonal demodulation unit that generates the baseband signal by performing orthogonal demodulation on the OFDM wave signal, and the baseband signal generated by the orthogonal demodulation unit, adds in units of a predetermined number of symbols on the time axis, A first error detection unit that detects a symbol head position, a frequency error, and a clock error by guard correlation, and a frequency error detected by the first error detection unit with respect to the baseband signal generated by the orthogonal demodulation unit A first frequency error correction unit that corrects the frequency error, and a baseband signal whose frequency error is corrected by the first frequency error correction unit. Then, based on the symbol head position detected by the first error detection unit, a first symbol cut-out unit that cuts off a GI and cuts out an effective symbol, and an effective cut-out by the first symbol cut-out unit A first FFT unit that performs symbol FFT to generate a carrier symbol and a carrier symbol generated by the first FFT unit are synchronously added for each predetermined symbol to generate a synchronous addition result. A pattern for calculating a correlation value between a symbol addition unit, a synchronous addition result generated by the first symbol addition unit, and a plurality of preset patterns, and detecting a pattern having the maximum correlation value A first clock that corrects a clock error detected by the first error detection unit with respect to the carrier symbol generated by the detection unit and the first FFT unit. An error correction unit, a second symbol addition unit that synchronously adds the carrier symbols whose clock error has been corrected by the first clock error correction unit for each predetermined symbol, and generates a synchronous addition result; and the pattern Based on the pattern detected by the detection unit, a first pilot extraction unit that extracts a pilot signal from the carrier symbol of the synchronous addition result generated by the second symbol addition unit, and the first pilot extraction unit A second error detector that calculates a deviation angle of the extracted pilot signal and detects a frequency error and a clock error based on the variation of the deviation angle, and a frequency error is generated by the first frequency error correction unit. A second frequency error correction unit that corrects the frequency error detected by the second error detection unit with respect to the corrected baseband signal; A second band that removes the GI and cuts out an effective symbol based on the symbol head position detected by the first error detector for the baseband signal whose frequency error has been corrected by the second frequency error corrector. FFT on the symbol cutout unit, the effective symbol cut out by the second symbol cutout unit, and a carrier symbol generated by the second FFT unit that generates a carrier symbol. A second clock error correction unit that corrects the clock error detected by the second error detection unit, and a carrier symbol whose clock error has been corrected by the second clock error correction unit, for each predetermined symbol. Based on the pattern detected by the pattern detection unit, and a third symbol addition unit that generates a synchronous addition result. A second pilot extraction unit for extracting a pilot signal from the carrier symbol of the synchronous addition result generated by the third symbol addition unit, and based on the pilot signal extracted by the second pilot extraction unit The OFDM wave signal is measured.

  In the OFDM wave measuring apparatus according to the present invention, the second symbol adder further counts the number of times of synchronous addition for each symbol as the number of calculated symbols, and the second error detector A predetermined first symbol number and a predetermined second symbol number larger than the first symbol number are determined based on the number of calculated symbols counted by the symbol adding unit of the first symbol number, and the first symbol number And, based on the pilot signal extracted by the first pilot extraction unit at the second symbol number, the deflection angle of the pilot signal is calculated, and based on the amount of change of the deflection angle on the time axis, A frequency error and a clock error are detected.

  Further, in the OFDM wave measuring apparatus according to the present invention, the second error detecting unit applies a plurality of pilot signals arranged at predetermined different frequency positions among pilot signals extracted by the first pilot extracting unit. Based on each of the plurality of pilot signals, calculating a deviation amount per symbol, converting the deviation amount into a deviation amount of a center frequency of the pilot signal, and the plurality of pilot signals A frequency error and a clock error are detected by using the shift amount of each center frequency in.

  The OFDM wave measuring apparatus according to the present invention is characterized in that the plurality of pilot signals are an SP signal having the lowest frequency and a CP (Continual Pilot) signal having the highest frequency.

  In the OFDM wave measuring apparatus according to the present invention, the second error detection unit has the largest amplitude in each of a plurality of predetermined ranges on the frequency axis among pilot signals extracted by the first pilot extraction unit. A pilot signal having a high value is selected, a variation amount of the deflection angle per symbol is calculated for each of the plurality of pilot signals based on the plurality of selected pilot signals, and the variation amount of the deflection angle is calculated as the pilot amount. The frequency error and the clock error are detected by using the shift amounts of the center frequencies of the plurality of pilot signals, which are converted into shift amounts of the center frequency of the signals.

  The OFDM wave measuring apparatus according to the present invention is characterized in that the plurality of predetermined ranges on the frequency axis are a range including an SP signal having the lowest frequency and a range including a CP signal having the highest frequency. .

  Further, the program according to the present invention extracts the pilot signal from the OFDM wave signal including the pilot signal, and orthogonally demodulates the OFDM wave signal to a computer that measures the OFDM wave signal to generate a baseband signal. The function of the orthogonal demodulator and the baseband signal generated by the orthogonal demodulator are added in units of a predetermined number of symbols on the time axis, and the symbol head position, frequency error and clock error are calculated by guard correlation. The function of the first error detection unit to detect and the first frequency error correction unit that corrects the frequency error detected by the first error detection unit with respect to the baseband signal generated by the quadrature demodulation unit For the function and the baseband signal whose frequency error has been corrected by the first frequency error correction unit, the first error detection unit Based on the detected symbol head position, the function of the first symbol cutout unit that removes the GI and cuts out the effective symbol, and the effective symbol cut out by the first symbol cutout unit are subjected to FFT to obtain a carrier symbol The function of the first FFT unit that generates the synchronous addition of the carrier symbol generated by the first FFT unit for each predetermined symbol, and the function of the first FFT unit that generates the synchronous addition result A correlation value between the synchronous addition result generated by the first symbol addition unit and a plurality of preset patterns, and a pattern detection unit for detecting a pattern having the maximum correlation value Function and a first clock error that corrects the clock error detected by the first error detector for the carrier symbol generated by the first FFT unit. A function of a correction unit, and a function of a second symbol addition unit that synchronously adds a carrier symbol whose clock error has been corrected by the first clock error correction unit for each predetermined symbol and generates a synchronous addition result; A function of a first pilot extraction unit that extracts a pilot signal from a carrier symbol of a synchronous addition result generated by the second symbol addition unit based on the pattern detected by the pattern detection unit; A function of a second error detector that calculates a deviation of the pilot signal extracted by the pilot extractor and detects a frequency error and a clock error based on the variation of the deviation, and the first frequency A second error correction unit that corrects the frequency error detected by the second error detection unit with respect to the baseband signal whose frequency error has been corrected by the error correction unit. Based on the function of the frequency error correction unit and the baseband signal whose frequency error has been corrected by the second frequency error correction unit, the GI is removed based on the symbol head position detected by the first error detection unit. And a function of a second symbol cutout unit that cuts out an effective symbol, a function of a second FFT unit that generates a carrier symbol by performing FFT on the effective symbol cut out by the second symbol cutout unit, A function of a second clock error correction unit that corrects a clock error detected by the second error detection unit with respect to the carrier symbol generated by two FFT units, and a clock generated by the second clock error correction unit. A function of a third symbol addition unit that synchronously adds the carrier symbol with the error corrected for each predetermined symbol and generates a synchronous addition result; Realizing a function of a second pilot extraction unit that extracts a pilot signal from a carrier symbol of a synchronous addition result generated by the third symbol addition unit, based on the pattern detected by the turn detection unit. Features.

  As described above, according to the present invention, even when the signal power is at a low level, the pilot signal is extracted by synchronous addition of symbols on the frequency axis, and the deviation angle is observed on the time axis. The frequency error and clock error were calculated. As a result, a highly accurate frequency error including positive and negative directions can be calculated, and a highly accurate clock error can be calculated. Therefore, it is possible to measure an OFDM wave signal with high accuracy.

It is a block diagram which shows the structure of the OFDM wave measuring apparatus by Example 1. FIG. It is a figure which shows the transition image of SP signal which the error detection part input from SP extraction part. It is a figure which shows the relationship between the frequency error and clock error between transmitter / receivers, and the center frequency of a pilot carrier. (1) is a figure which shows the example of a transition on the IQ axis in SP signal (left end SP signal) with the lowest frequency of the left end of an OFDM wave, (2) is CP signal with the highest frequency of the right end of an OFDM wave. It is a figure which shows the transition example on IQ axis in (right end CP signal), (3) is a figure which shows the transition example of variation | change_quantity (theta) of the deflection angle in a left end SP signal. It is a figure explaining the left end SP signal and right end CP signal used as an observation object in Example 1. FIG. 6 is a flowchart illustrating processing of an error detection unit according to the first embodiment. It is a figure explaining SP1 signal and SP2 signal selected in Example 2. FIG. 10 is a flowchart illustrating processing of an error detection unit according to the second embodiment.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. The OFDM wave measuring apparatus according to the first embodiment extracts a pilot signal by synchronous addition of symbols on the frequency axis, observes the deflection angle of the extracted pilot signal on the time axis, and includes positive and negative directions from the amount of change. A frequency error and a clock error are calculated. As a result, even when the signal power is at a low level, highly accurate frequency and clock errors can be obtained, and by correcting these frequency and clock errors, the OFDM wave signal can be measured with high accuracy. can do. Further, the OFDM wave measuring apparatus according to the second embodiment extracts a pilot signal by synchronous addition of symbols on the frequency axis, selects a pilot signal having a high amplitude value from the extracted pilot signals, and biases the selected pilot signal. An angle is observed on a time axis, and a frequency error and a clock error including positive and negative directions are calculated from the amount of change. Accordingly, even when an OFDM wave including a so-called multipath or the like having a low carrier amplitude value at a specific frequency is received, the signal of the OFDM wave can be measured with high accuracy.

[Example 1]
First, Example 1 will be described. In the first embodiment, as described above, a pilot signal is extracted by synchronous addition of symbols on the frequency axis, the deviation angle of the extracted pilot signal is observed on the time axis, and the frequency including the positive and negative directions is determined from the amount of change. An error and a clock error are calculated.

  FIG. 1 is a block diagram illustrating a configuration of an OFDM wave measurement apparatus according to the first embodiment. This OFDM wave measuring apparatus 1 includes a frequency conversion unit 11, an A / D (Analog / Digital) conversion unit 12, an orthogonal demodulation unit 13, an error detection unit 14, frequency error correction units 15-1 and 15-2, and a symbol cutout. Units 16-1, 16-2, 16-3, FFT units 17-1, 17-2, 17-3, symbol addition units 18-1, 18-2, 18-3, SP pattern detection unit (pattern detection unit) ) 19, clock error correction units 20-1, 20-2, SP extraction units (pilot extraction units) 21-1, 21-2, error detection unit 22, received power calculation unit 23, spectrum calculation unit 24, and delay profile calculation The unit 25 is provided.

  The frequency converter 11 receives an RF (Radio Frequency) signal of the OFDM signal received by the receiving antenna, generates a IF (Intermediate Frequency) signal by frequency conversion, and an A / D converter 12 is output. The A / D converter 12 receives the IF signal from the frequency converter 11, converts the analog IF signal into a digital IF signal, and outputs the digital IF signal to the quadrature demodulator 13. The quadrature demodulator 13 receives the digital IF signal from the A / D converter 12 and performs quadrature demodulation to generate baseband signals of I (In-phase) and Q (Quadrature), and generates an error. It outputs to the detection part 14 and the frequency error correction | amendment part 15-1.

  The error detection unit 14 receives the IQ baseband signal from the quadrature demodulation unit 13, sequentially performs addition in units of four symbols with reference to a predetermined data head position on the time axis, and applies a guard phase to the addition result. A guard correlation value is calculated, and a symbol head position, a clock error, and a frequency error are detected based on the guard correlation value. Here, the predetermined data head position indicates an arbitrary position on the time axis of the IQ baseband signal. Then, the error detection unit 14 outputs the detected symbol head position to the symbol cutout units 16-1, 16-2, 16-3, and detects the detected clock error (the clock error detected by the symbol addition on the time axis). ) Is output to the clock error correction unit 20-1, and the detected frequency error (frequency error detected by symbol addition on the time axis) is output to the frequency error correction unit 15-1. Here, the detection processing of the symbol head position, the clock error, and the frequency error by the error detection unit 14 is already known. For details, refer to Patent Document 3 described above.

  The frequency error correction unit 15-1 receives the IQ baseband signal from the quadrature demodulation unit 13 and the frequency error from the error detection unit 14, and based on the input frequency error, the baseband signal (IQ signal) Correct the frequency error at. Then, the frequency error correction unit 15-1 converts the baseband signal obtained by correcting the frequency error (frequency error detected by symbol addition on the time axis) into the frequency error correction unit 15-2 and the symbol cutout unit 16-1. , 16-2.

  The symbol cutout unit 16-1 receives the baseband signal in which the frequency error (frequency error detected by symbol addition on the time axis) is corrected from the frequency error correction unit 15-1 and the error detection unit 14. Enter the symbol start position from. The symbol cutout unit 16-1 then removes the GI from the baseband signal based on the position shifted by the symbol start position from the data start position as the reference for addition in units of four symbols in the error detection unit 14, and is effective. Cut out the signal of the symbol. Then, the symbol cutout unit 16-1 outputs an effective symbol signal to the FFT unit 17-1.

  The FFT unit 17-1 receives the effective symbol signal from the symbol cutout unit 16-1, performs FFT to generate a carrier symbol, and outputs the carrier symbol FFT output signal to the symbol adder 18-1. In this case, the FFT unit 17-1 divides into four groups of a symbol number of 4nth carrier symbol, a symbol number of 4n + 1th carrier symbol, a symbol number of 4n + 2nd carrier symbol, and a symbol number of 4n + 3rd carrier symbol. The FFT output signal is output to the symbol adder 18-1 for each group. n is an integer of 0 or more.

  The symbol adder 18-1 includes four groups of carrier symbols (symbol number is 4nth carrier symbol, symbol number is 4n + 1th carrier symbol, symbol number is 4n + 2nd carrier) that is an FFT output signal from the FFT unit 17-1. Symbol and symbol number 4n + 3rd carrier symbol) are input, and carrier symbols are synchronously added for each group. That is, the symbol addition unit 18-1 performs vector addition for each subcarrier for each group. Then, the symbol addition unit 18-1 performs the synchronous addition result of the 4nth carrier symbol whose symbol number is the synchronous addition result for each group, the synchronous addition result of the 4n + 1th carrier symbol, and the symbol number of 4n + 2th. The synchronous addition result of the carrier symbol and the synchronous addition result of the 4n + 3rd carrier symbol with the symbol number are output to the SP pattern detection unit 19. Specifically, the symbol addition unit 18-1 performs an addition process using a loop filter or an addition process using a moving average as the synchronous addition process. Here, the addition processing by the symbol addition unit 18-1 is known, and for details, refer to Patent Document 3 described above.

  The SP pattern detection unit 19 obtains four groups of synchronous addition results from the symbol addition unit 18-1 (synchronization addition result of the 4nth carrier symbol with the symbol number, the synchronous addition result of the 4n + 1th carrier symbol with the symbol number of the symbol number). 4n + 2nd carrier symbol synchronous addition result and 4n + 3rd carrier symbol synchronous addition result). Then, the SP pattern detection unit 19 calculates correlation values between these synchronous addition results and four preset SP patterns, and whether or not SP can be extracted based on the four correlation values. Is generated, a signal indicating whether or not SP extraction is possible is generated, and an SP pattern having the maximum correlation value when SP extraction is possible is detected. If the SP pattern detection unit 19 determines that SP extraction is impossible, the SP pattern detection unit 19 outputs a signal indicating that SP extraction is impossible to the SP extraction units 21-1 and 21-2, and determines that SP extraction is possible. The SP extractable signal and the SP pattern are output to the SP extraction units 21-1 and 21-2. Here, the SP pattern detection processing by the SP pattern detection unit 19 is known, and for details, refer to Patent Document 3 described above.

  Here, in the SP pattern detection unit 19, when the power of the received signal is low, immediately after the start of the SP pattern detection process, there is not much difference in the correlation value between the synchronous addition result and the four SP patterns. This is because when the power of the received signal is low, four different types of SP signals (SP signals having different amplitudes and phases) existing in one symbol cannot be clearly distinguished. As the number of symbols to be synchronously added increases and the SP pattern detection process proceeds, one of the four correlation values becomes larger than the other three correlation values. That is, the synchronous addition result becomes closer to one of the four SP patterns as the synchronous addition process proceeds. This is because even if the power of the received signal is low, the four different types of SP signals existing in one symbol can be clearly distinguished by the progress of the synchronous addition process. Based on the difference between the correlation values, it is determined whether the SP can be extracted and the SP pattern, or the SP cannot be extracted.

  The symbol cutout unit 16-2 and the FFT unit 17-2 perform the same processes as those of the symbol cutout unit 16-1 and the FFT unit 17-1, respectively.

The clock error correction unit 20-1 receives four groups of carrier symbols as FFT output signals from the FFT unit 17-2, and receives a clock error (clock detected by symbol addition on the time axis) from the error detection unit 14. Error) is input, and for each group, a difference τ indicating the number of clocks corresponding to the time difference between the current symbol position and the ideal symbol position is calculated based on the clock error, and the phase of the SP signal is set to 2πf. _The clock error is corrected by reversely rotating kτ, and four groups of carrier symbols with the corrected clock error are output to the symbol adder 18-2. Here, f _k represents the center carrier frequency of the SP signal at subcarrier number k. The clock error correction processing by the clock error correction unit 20-1 is already known. For details, refer to Patent Document 3 described above.

  The symbol adder 18-2 receives four groups of carrier symbols in which the clock error (clock error detected by symbol addition on the time axis) is corrected from the clock error corrector 20-1, and the symbol adder 18 -1 is performed, the symbol number is the 4nth carrier symbol synchronous addition result, the symbol number is the 4n + 1 carrier symbol synchronous addition result, the symbol number is the 4n + 2nd carrier symbol synchronous addition result, and the symbol number Outputs the synchronous addition result of the 4n + 3rd carrier symbol to the SP extraction unit 21-1. The symbol adder 18-2 counts the number of times of synchronous addition, and outputs this to the error detector 22 as the number of calculated symbols.

  The SP extraction unit 21-1 receives the four groups of synchronous addition results from the symbol addition unit 18-2, and inputs the SP extraction impossibility or SP extraction enabled and the SP pattern from the SP pattern detection unit 19. And SP extraction part 21-1 does not perform SP extraction processing, when SP extraction impossible is inputted. On the other hand, when SP extraction possible is input, the SP extraction unit 21-1 extracts the SP signal from the four groups of synchronous addition results based on the SP pattern, extracts the CP signal, and extracts the extracted SP signal and CP signal. Is output to the error detection unit 22.

  The error detection unit 22 receives the SP signal and the CP signal from the SP extraction unit 21-1, and also receives the number of calculation symbols indicating the number of synchronous additions from the symbol addition unit 18-2. The SP signal having the lowest frequency and the CP signal having the highest frequency at the right end are observed, and when the amount of change in the deflection angle per symbol of these SP signal and CP signal is equal to or greater than the number of calculated symbols, these SP signals For the CP signal, the declination is calculated on the time axis, and the frequency error and the clock error are detected. Then, the error detection unit 22 outputs the detected frequency error (frequency error detected by symbol addition on the frequency axis and calculation of the deviation angle on the time axis) to the frequency error correction unit 15-2 and the detected clock. The error (clock error detected by symbol addition on the frequency axis and calculation of declination on the time axis) is output to the clock error correction unit 20-2. Details of the processing of the frequency error detection unit 22 will be described later.

  The frequency error correction unit 15-2 receives the baseband signal in which the frequency error (frequency error detected by symbol addition on the time axis) is corrected from the frequency error correction unit 15-1, and the error detection unit 22 Frequency error (frequency error detected by symbol addition on the frequency axis and declination calculation on the time axis) is input, and based on the input frequency error, the same as the frequency error correction unit 15-1 is performed again. Processing is performed to correct a frequency error in the input baseband signal. Then, the frequency error correction unit 15-2 converts the baseband signal obtained by correcting the frequency error (frequency error detected by symbol addition on the frequency axis and calculation of the deviation angle on the time axis) to the symbol cutout unit 16-3. Output to.

  The symbol cutout unit 16-3 and the FFT unit 17-3 perform the same processing as the symbol cutout unit 16-1 and the FFT unit 17-1. The clock error correction unit 20-2 receives four groups of carrier symbols, which are FFT output signals, from the FFT unit 17-3, and receives a clock error (symbol addition on the frequency axis and deviation on the time axis) from the error detection unit 22. The clock error detected by the angle calculation) is input, and the same processing as that of the clock error correction unit 20-1 is performed to correct the carrier symbol clock error for each group. Then, the clock error correction unit 20-2 corrects the clock error (clock error detected by adding the symbol on the frequency axis and calculating the deviation angle on the time axis) to the four groups of carrier symbols as the symbol addition unit 18-3. Output to.

  The symbol adder 18-3 and the SP extractor 21-2 perform the same processing as the symbol adder 18-1 and the SP extractor 21-1. The received power calculation unit 23, the spectrum calculation unit 24, and the delay profile calculation unit 25 receive the SP signal from the SP extraction unit 21-2, and calculate the received power, spectrum, and delay profile of the OFDM signal, respectively. In addition, since the calculation method of the received power, spectrum, and delay profile of the OFDM signal is known, detailed description is omitted here. Further, the SP extraction unit 21-2 extracts a pilot signal other than the SP signal, and the reception power calculation unit 23, the spectrum calculation unit 24, and the delay profile calculation unit 25 use the pilot signal to receive the reception power, the spectrum, and Each delay profile may be calculated.

(Error detection unit)
Next, the error detection unit 22 shown in FIG. 1 will be described in detail. As described above, the error detection unit 22 receives the SP signal and the CP signal from the SP extraction unit 21-1, and also receives the number of calculation symbols indicating the number of synchronous additions from the symbol addition unit 18-2. When the SP signal with the lowest frequency at the left end and the CP signal with the highest frequency at the right end are observed, and the amount of change in deflection angle per symbol of these SP signal and CP signal is equal to or greater than the number of calculated symbols, Deviations are calculated on the time axis for these SP signal and CP signal, and a frequency error and a clock error are detected.

  FIG. 2 shows a transition image of the SP signal input by the error detection unit 22 from the SP extraction unit 21-1. Specifically, for the SP signal input from the SP extraction unit 21-1, the error detection unit 22 observes the SP signal at the same carrier position in time series and plots the image on the IQ axis (SP in the Mth symbol). The position of the signal and the position of the SP signal in the Nth symbol) are shown. Let N> M. (1) shows a case where there is no frequency error and clock error (hereinafter collectively referred to as an error), and (2) shows a case where there is an error.

  As shown in FIG. 2 (1), when there is no error, the SP signal is plotted on a straight line passing through the origin of the IQ axis, and the deflection angle α1 of the SP signal changes at any time (symbol). Absent. On the other hand, as shown in FIG. 2B, when there is an error, the SP signal is not plotted on a straight line, and the deflection angles α1 and α2 of the SP signal change with the passage of time. In this case, the amount of change in the declination of the SP signal (the amount of declination changing between one OFDM symbol) varies depending on the carrier symbol.

  FIG. 3 is a diagram showing the relationship between the frequency error and clock error between the transceiver and the center frequency of the pilot carrier. The vertical solid line in (1) and the vertical dotted line in (2) to (4) indicate the position of the center frequency in each OFDM carrier. As shown in (2), when the OFDM carrier includes only the frequency error Δfc, the center frequencies of all carrier symbols are uniformly shifted by Δfc. For this reason, the amount of change in declination is the same for all carrier symbols. As shown in (3), when the OFDM carrier includes only the clock error Δfclk, the carrier symbol clock error Δfclk increases as the frequency position moves away from the carrier symbol at the center position (0). Therefore, as shown in (4), when the OFDM carrier includes a frequency error and a clock error, the error is the sum of the frequency error Δfc and the clock error Δfclk. For this reason, the amount of change in the deviation angle of the carrier symbol differs depending on the frequency position of the carrier symbol. Therefore, the error detection unit 22 calculates a change amount of each declination for a plurality of carrier symbols, and detects a frequency error and a clock error from the change amount.

  FIG. 4 (1) is a diagram showing a transition example on the IQ axis of the SP signal having the lowest frequency at the left end of the OFDM wave (left end SP signal), and FIG. 4 (2) is the frequency at the right end of the OFDM wave. FIG. 4C is a diagram showing a transition example on the IQ axis of a high CP signal (right end CP signal), and FIG. 4C is a diagram showing a transition example of the change amount θ of the deflection angle in the left end SP signal. As shown in FIGS. 4 (1) and (2), both the left-end SP signal and the right-end CP signal are rotated by error as the symbol advances. It rotates on the circumference around the origin on the axis. Also, as shown in FIG. 4 (3), when the left end SP signal becomes a calculation symbol of a predetermined symbol or more, the variation amount θ of the declination per symbol becomes stable. The same applies to the right end CP signal. Therefore, the error detection unit 22 determines that the amount of change in the deflection angle used for error detection is 1 symbol when the variation amount θ of the deflection angle per symbol is stable (when the number of calculation symbols is equal to or greater than the predetermined number of calculation symbols). What is necessary is just to obtain | require the variation | change_quantity (theta) of a perclination.

  FIG. 5 is a diagram for explaining the left end SP signal and the right end CP signal to be observed in the first embodiment. As shown in FIG. 5, the leftmost SP signal is a signal at the 2808th carrier position in the direction of lower frequency from the position of the center carrier on the frequency axis, and is the SP signal with the lowest frequency. The rightmost CP signal is a signal at the 2808th carrier position in the direction of higher frequency from the position of the center carrier on the frequency axis, and is the CP signal with the highest frequency. The error detection unit 22 observes the left end SP signal and the right end CP signal at the position shown in FIG. 5 among the SP signal and the CP signal input from the SP extraction unit 21-1, and as shown in FIG. When the amount of change in declination per symbol of the SP signal and right end CP signal is stabilized, the amount of change in declination is calculated, and the frequency error and clock error are detected from these amounts of change.

FIG. 6 is a flowchart illustrating the processing of the error detection unit 22 according to the first embodiment. First, the error detection unit 22 receives the SP signal and the CP signal from the SP extraction unit 21-1, and also receives the number of calculation symbols indicating the number of synchronous additions from the symbol addition unit 18-2 (step S601). When the error detection unit 22 determines the M-th symbol (M-th symbol) set in advance from the number of input calculation symbols, the IQ value in the left end SP signal of the SP signal and CP signal of the M-th symbol ( I _SP (M), Q _SP (M)) and the IQ value (I _CP (M), Q _CP (M)) in the right end CP signal are stored in the memory (step S602). Here, M is the number of symbols at the stage where the amount of deviation change per symbol is equal to or greater than the number of calculated symbols in the left end SP signal and the right end CP signal, and the left end SP signal and the right end CP signal are arranged. A preset value for designating a symbol is used. The same applies to Example 2 described later.

When the error detection unit 22 determines a preset N (> M) th symbol (Nth symbol) from the number of input calculation symbols, the IQ in the left end SP signal of the Nth symbol SP signal and CP signal is determined. The value (I _SP (N), Q _SP (N)) and the IQ value (I _CP (N), Q _CP (N)) in the right end CP signal are stored in the memory (step S603). Here, N is the number of symbols larger than M at the stage where the amount of change in the deflection angle per symbol is equal to or more than the number of calculated symbols in the left end SP signal and the right end CP signal, and the left end SP signal and the right end CP A preset value for designating the symbol in which the signal is arranged is used. The same applies to Example 2 described later.

  Note that the error detection unit 22 determines whether the deviation change amount per symbol of the left-end SP signal and the right-end CP signal is equal to or greater than the number of calculation symbols that are stable in steps S602 and S603. Although the Mth and Nth symbols set in advance are determined, as shown in FIG. 4, it is determined the stage where the amount of deviation change per symbol of the left end SP signal and the right end CP signal is stable, and thereafter The symbol in which the left end SP signal and the right end CP signal are arranged may be determined as the Mth symbol, and the symbol that is larger than M and in which the left end SP signal and the right end CP signal are arranged may be determined as the Nth symbol. For example, the error detection unit 22 calculates a deviation change amount per symbol of the left end SP signal and the right end CP signal for each predetermined number of symbols, and the change in the deviation change amount is equal to or less than a certain threshold value. When it becomes, it may be determined that the above-mentioned stable stage is reached. Further, the error detection unit 22 calculates the amplitude values of the left end SP signal and the right end CP signal for each predetermined number of symbols using the input number of calculated symbols, and the change in the average value of the amplitude values is constant. You may determine with the above-mentioned stable stage when it becomes below a threshold. The same applies to Example 2 described later.

The error detection unit 22 reads the IQ value (I _SP (M), Q _SP (M)) of the left end SP signal of the Mth symbol and the IQ value (I _CP (M), Q _CP (M) of the right end CP signal from the memory. )), And the IQ value (I _SP (N), Q _SP (N)) of the left end SP signal of the Nth symbol and the IQ value (I _CP (N), Q _CP (N)) of the right end CP signal are read out. Using these IQ values, the deviation change amount (rotation amount) θ _SP per symbol in the left end SP signal and the deviation change amount θ _CP per symbol in the right end CP signal are calculated using the IQ values below. (Step S604).
[Formula 1]
θ _SP = {atan (Q _SP (N) / I _SP (N)) − atan (Q _SP (M) / I _SP (M))} / (N−M) (1)
[Formula 2]
θ _CP = {atan (Q _CP (N) / I _CP (N)) − atan (Q _CP (M) / I _CP (M))} / (N−M) (2)

Error detecting unit 22, a polarization angle variation theta _CP polarization angle variation theta _SP and right CP signal left SP signals calculated in step S604, the by the following equation, the deviation amount ΔF of the center frequency of the left SP signals The center frequency of the _SP and right end CP signal is converted into a shift amount ΔF _CP (step S605).
[Formula 3]
ΔF _SP = θ _SP /1.008e ⁻³ / 2 / π (3)
[Formula 4]
ΔF _CP = θ _CP /1.008e ⁻³ / 2 / π (4)
Here, 1.008e ⁻³ indicates the OFDM symbol length (sec).

The error detection unit 22 uses the following equation to calculate the frequency error Δfc and the clock error using the shift amount ΔF _SP of the center frequency of the left end SP signal and the shift amount ΔF _CP of the center frequency of the right end CP signal converted in step S605. Δfclk is calculated, the frequency error Δfc is output to the frequency error correction unit 15-2, and the clock error Δfclk is output to the clock error correction unit 20-2 (step S606).
[Formula 5]
Δfc = (ΔF _CP + ΔF _SP ) / 2 (5)
[Formula 6]
Δfclk = (ΔF _CP −ΔF _SP ) × 8192/5616 (6)
Here, the FFT size is 8192, and the number of subcarriers is 5617. Thereby, the frequency error Δfc and the clock error Δfclk are calculated simultaneously.

The mathematical formulas (5) and (6) in step S606 will be described in detail. The shift amount ΔF _CP of the center frequency of the right end CP signal is determined by a constant frequency error Δfc in all carriers and a clock error component at the time of FFT. At the time of FFT, the clock is aligned with the center carrier, and the right end CP signal is located at the 2808th carrier position in the direction of higher frequency from the position of the center carrier. Therefore, the clock error component of the right end CP signal is Δfclk × 2808 / 8192. Therefore, the shift amount ΔF _CP of the center frequency of the right end CP signal is expressed by the following equation.
[Formula 7]
ΔF _CP = Δfc + Δfclk × 2808/8192 (7)

Similarly to the right end CP signal, the shift amount ΔF _SP of the center frequency of the left end SP signal is also determined by a constant frequency error Δfc in all carriers and a clock error component at the time of FFT. Further, since the left end SP signal is located at the 2808th carrier position in the direction of lower frequency from the position of the center carrier, the clock error component of the left end SP signal is a negative value unlike the right end CP signal, and Δfclk × ( -2808) / 8192. Therefore, the shift amount ΔF _SP of the center frequency of the left end SP signal is expressed by the following equation.
[Formula 8]
ΔF _SP = Δfc + Δfclk × (−2808) / 8192 (8)
Thereby, the formulas (5) and (6) are derived from the formulas (7) and (8).

  As described above, according to the OFDM wave measuring apparatus 1 of the first embodiment, the symbol adder 18-2 performs synchronous addition of four groups of carrier symbols and counts the number of calculated symbols indicating the number of synchronous additions. The SP extraction unit 21-1 extracts the SP signal and the CP signal based on the SP pattern detected by the SP pattern detection unit 19 from the synchronous addition result of the four groups of carrier symbols. . Then, the error detection unit 22 observes the left end SP signal and the right end CP signal among the SP signal and CP signal extracted by the SP extraction unit 21-1, and at the stage when the number of calculation symbols is equal to or greater than the predetermined number. The deviation angle was calculated on the time axis for the SP signal and the CP signal, and the frequency error and the clock error were detected. The frequency error correction unit 15-2 corrects the frequency error detected by the error detection unit 22, and the clock error correction unit 20-2 corrects the clock error detected by the error detection unit 22, and adds a symbol. The unit 18-3 synchronously adds the SP signal in the carrier symbol after correcting the clock error, and the SP extraction unit 21-2 extracts the SP signal from the synchronous addition result, and the received power calculation unit 23, the spectrum calculation The unit 24 and the delay profile calculation unit 25 measure the OFDM wave signal based on the extracted SP signal.

  Conventionally, in order to determine the direction of the frequency error after detecting the frequency error of the absolute value, complicated processing such as obtaining the number of calculation symbols at which the SP signal power reaches the peak value has been required. On the other hand, in the first embodiment, the deviation angle of the SP signal or the like is observed on the time axis, and the frequency error including the positive and negative directions is calculated from the amount of change. A highly accurate frequency error can be calculated with a simple method. Conventionally, the clock error is calculated by the addition processing on the time axis and the guard correlation processing, whereas in the first embodiment, the pilot signal is extracted by symbol addition on the frequency axis, and the extracted pilot signal The declination was observed on the time axis, and the clock error was calculated from the amount of change. This makes it possible to calculate a clock error with higher accuracy than in the past. Therefore, even when the received power is at a low level, a highly accurate frequency error and clock error are calculated, and these errors are corrected. Therefore, it is possible to measure an OFDM wave signal with high accuracy. That is, the received power, spectrum, and delay profile can be measured with high accuracy.

[Example 2]
Next, Example 2 will be described. In the second embodiment, a pilot signal is extracted by synchronous addition of symbols on the frequency axis in order to accurately measure an OFDM wave signal including a so-called multipath having a low carrier amplitude value at a specific frequency. Select a pilot signal with a high amplitude value from the selected pilot signals, observe the declination of the selected pilot signal on the time axis, and calculate the frequency error and clock error including positive and negative directions from the amount of change. It is characterized by.

  The OFDM wave measuring apparatus 1 according to the second embodiment has the same configuration as the OFDM wave measuring apparatus 1 according to the first embodiment shown in FIG. 1, but performs processing different from that of the error detection unit 22 according to the first embodiment. Frequency converter 11, A / D converter 12, orthogonal demodulator 13, error detector 14, frequency error correctors 15-1, 15-2, symbol extractors 16-1, 16-2, 16-3, FFT units 17-1, 17-2, 17-3, symbol addition units 18-1, 18-2, 18-3, SP pattern detection unit 19, clock error correction units 20-1, 20-2, SP extraction unit 21-1, 21-2, the received power calculation unit 23, the spectrum calculation unit 24, and the delay profile calculation unit 25 are the same as those in the first embodiment, and thus the description thereof is omitted here.

  The error detection unit 22 according to the second embodiment inputs the SP signal and the CP signal from the SP extraction unit 21-1, and also receives the number of calculation symbols indicating the number of synchronous additions from the symbol addition unit 18-2. SP1 signal and SP2 signal having the highest amplitude values in the ranges A and B are selected, respectively, and the selection is made when the amount of deviation change per symbol of the SP1 signal and SP2 signal is equal to or greater than the number of calculated symbols. The declination on the time axis is calculated for the SP1 signal and SP2 signal, and a frequency error and a clock error are detected.

(Error detection unit)
Next, the error detection unit 22 according to the second embodiment will be described in detail. FIG. 7 is a diagram illustrating the SP1 signal and the SP2 signal selected in the second embodiment. As shown in FIG. 7, a range A in which the SP1 signal is selected and a range B in which the SP2 signal is selected are set in advance on the frequency axis. Here, it is assumed that the center frequency of the SP1 signal is lower than the center frequency of the SP2 signal. The SP1 signal is selected as the SP signal having the highest amplitude value among the plurality of SP signals within the range A, and the SP2 signal is selected as the SP signal having the highest amplitude value among the plurality of SP signals within the range B. . The selected SP1 signal is the signal at the a-th carrier position in the direction of lower frequency from the position of the center carrier on the frequency axis, and the SP2 signal is b in the direction of higher frequency from the position of the center carrier on the frequency axis. Assuming that the signal is at the first carrier position, the SP1 signal is at a position away from the center carrier by a × Δf (Hz) in the direction of lower frequency, and the SP2 signal is at the position of b × Δf in the direction of higher frequency from the center carrier. (Hz) away. Here, Δf represents the frequency of the carrier interval.

  For example, in the frequency region in which carriers are arranged on the frequency axis, the range A in which the SP1 signal is selected is a range including the SP signal having the lowest frequency and is ¼ from the carrier position having the lowest frequency. As the range B in which the range is preset and the SP2 signal is selected, a range including the SP signal with the highest frequency and a range of ¼ from the carrier position with the highest frequency is preset. As a result, the center frequency of the SP1 signal and the center frequency of the SP2 signal are separated from each other as compared with the case where the ranges A and B where the frequencies are close to each other, and the difference in the declination becomes large. Errors and clock errors can be calculated.

  FIG. 8 is a flowchart illustrating the processing of the error detection unit 22 according to the second embodiment. First, the error detection unit 22 receives the SP signal and the CP signal from the SP extraction unit 21-1, and calculates the number of synchronous additions from the symbol addition unit 18-2, similarly to step S601 shown in FIG. The number of symbols is input (step S801).

  When the error detection unit 22 determines the Mth symbol set in advance from the number of input calculation symbols, the error detection unit 22 calculates the amplitude value for each of the plurality of SP signals in the preset range A at the Mth symbol, The SP1 signal (a carrier from the center carrier, see FIG. 7) is selected as the SP signal having a high value, and amplitude values are calculated for a plurality of SP signals within a preset range B, respectively. The SP2 signal (the bth carrier from the center carrier) is selected as the SP signal having a high (step S802).

  Note that the error detection unit 22 may select the SP1 signal and the SP2 signal by a process similar to the above for the symbols before the preset Mth symbol.

In the Mth symbol, the error detection unit 22 performs the IQ value (I _SP1 (M), Q _SP1 (M)) of the SP1 signal selected in Step S802 and the IQ value (I _SP2 (M), Q _SP2 ) of the SP2 signal. (M)) is stored in the memory (step S803). When the error detection unit 22 determines the preset N (> M) symbol from the number of input calculation symbols, the IQ value (I _SP1 (N) of the SP1 signal at the same carrier position selected in step S802 is selected. , Q _SP1 (N)) and the IQ value (I _SP2 (N), Q _SP2 (N)) of the SP2 signal at the same carrier position are stored in the memory (step S804).

The error detection unit 22 reads the IQ value (I _SP1 (M), Q _SP1 (M)) of the _SP1 signal and the IQ value (I _SP2 (M), Q _SP2 (M)) of the SP2 signal from the memory. And the IQ value (I _SP1 (N), Q _SP1 (N)) of the SP1 signal of the Nth symbol and the IQ value (I _SP2 (N), Q _SP2 (N)) of the SP2 signal are read out, and Thus, using these IQ values, the deflection change amount (rotation amount) θ _SP1 per symbol in the _SP1 signal and the deflection change amount θ _SP2 per symbol in the SP2 signal are calculated (step S805).
[Formula 9]
θ _SP1 = {atan (Q _SP1 (N) / I _SP1 (N)) − atan (Q _SP1 (M) / I _SP1 (M))} / (N−M) (9)
[Formula 10]
θ _SP2 = {atan (Q _SP2 (N) / I _SP2 (N)) − atan (Q _SP2 (M) / I _SP2 (M))} / (N−M) (10)

The error detection unit 22 calculates the deviation angle variation θ _{SP1 of the SP1} signal and the deviation variation θ _SP2 of the SP2 signal calculated in step S805 by using the following equations, and the deviation amounts ΔF _SP1 and SP2 of the center frequency of the SP1 signal. The signal is converted into a shift amount ΔF _SP2 of the center frequency of the signal (step S806).
[Formula 11]
ΔF _SP1 = θ _SP1 /1.008e ⁻³ / 2 / π (11)
[Formula 12]
ΔF _SP2 = θ _SP2 /1.008e ⁻³ / 2 / π (12)
Here, 1.008e ⁻³ indicates the OFDM symbol length (sec).

The error detection unit 22 calculates the frequency error Δfc and the clock error Δfclk using the following formula using the shift amount ΔF _SP1 of the center frequency of the SP1 signal and the shift amount ΔF _SP2 of the center frequency of the SP2 signal converted in step S806. The frequency error Δfc is calculated and output to the frequency error correction unit 15-2, and the clock error Δfclk is output to the clock error correction unit 20-2 (step S807).
[Formula 13]
Δfc = (a × ΔF _SP2 + b × ΔF _SP1 ) / (a + b) (13)
[Formula 14]
Δfclk = (ΔF _SP2 −ΔF _SP1 ) × 8192 / (a + b) (14)
Here, the FFT size is 8192, and the number of subcarriers is 5617. Thereby, the frequency error Δfc and the clock error Δfclk are calculated simultaneously.

The mathematical formulas (13) and (14) in step S807 will be described in detail. The shift amount ΔF _SP1 of the center frequency of the SP1 signal is determined by a constant frequency error Δfc in all carriers and a clock error component at the time of FFT. At the time of FFT, the clock is aligned with the center carrier, and since the SP1 signal is located at the a-th carrier position in the direction of lower frequency from the position of the center carrier, the clock error component of the SP1 signal is Δfclk × (−a). / 8192. Therefore, the shift amount ΔF _SP1 of the center frequency of the SP1 signal is expressed by the following equation.
[Formula 15]
ΔF _SP1 = Δfc + Δfclk × (−a) / 8192 (15)

Similarly to the SP1 signal, the shift amount ΔF _SP2 of the center frequency of the SP2 signal is also determined by a constant frequency error Δfc in all carriers and a clock error component at the time of FFT. Further, since the SP2 signal is located at the b-th carrier position in the direction of higher frequency from the position of the center carrier, the component of the clock error of the SP2 signal is a positive value unlike the SP1 signal, and Δfclk × b / 8192. Become. Therefore, the shift amount ΔF _SP2 of the center frequency of the SP2 signal is expressed by the following equation.
[Formula 16]
ΔF _SP2 = Δfc + Δfclk × b / 8192 (16)
Thereby, the formulas (13) and (14) are derived from the formulas (15) and (16).

  As described above, according to the OFDM wave measuring apparatus 1 of the second embodiment, the symbol adder 18-2 performs synchronous addition of four groups of carrier symbols and counts the number of calculation symbols indicating the number of synchronous additions. The SP extraction unit 21-1 extracts the SP signal and the CP signal based on the SP pattern detected by the SP pattern detection unit 19 from the synchronous addition result of the four groups of carrier symbols. . Then, the error detection unit 22 selects the SP1 signal and the SP2 signal having the highest amplitude value among the SP signals within the predetermined ranges A and B, which are SP signals extracted by the SP extraction unit 21-1. Observe the selected SP1 signal and SP2 signal, and calculate the declination on the time axis for these SP1 signal and SP2 signal when the number of calculated symbols is equal to or greater than the predetermined number of symbols, and detect the frequency error and clock error. I made it. The frequency error correction unit 15-2 corrects the frequency error detected by the error detection unit 22, and the clock error correction unit 20-2 corrects the clock error detected by the error detection unit 22, and adds a symbol. The unit 18-3 synchronously adds the SP signal in the carrier symbol after correcting the clock error, and the SP extraction unit 21-2 extracts the SP signal from the synchronous addition result, and the received power calculation unit 23, the spectrum calculation The unit 24 and the delay profile calculation unit 25 measure the OFDM wave signal based on the extracted SP signal.

  As a result, the frequency error and the clock error are calculated using the SP1 signal and the SP2 signal in good reception state, so that in addition to the effects of the first embodiment, the received OFDM signal has a carrier amplitude value at a specific frequency. Even when a so-called multipath or the like is included, an OFDM wave signal can be measured with high accuracy. That is, the received power, spectrum, and delay profile can be measured with high accuracy.

  The present invention has been described with reference to the first and second embodiments. However, the present invention is not limited to the first and second embodiments, and various modifications can be made without departing from the technical idea thereof. For example, in the error detection unit 22 according to the first and second embodiments, the frequency error and the clock error are detected using the SP signal and the CP signal or the SP signal, but pilot signals other than the SP signal and the CP signal are detected. You may make it use. For example, the error detection unit 22 according to the second embodiment selects an SP signal having the highest amplitude value from a plurality of SP signals within a preset range A (low frequency region), and sets the preset range B (frequency). The SP signal having the highest amplitude value is selected from a plurality of SP signals within the range (B), but the SP signal or CP signal having the highest amplitude value is selected from the plurality of SP signals and CP signals within the range B. You may make it do.

  Further, the error detection unit 22 according to the first embodiment detects a frequency error and a clock error using two different SP signals and CP signals, but may use two different SP signals. Three or more different SP signals may be used. Further, the error detection unit 22 according to the second embodiment detects the frequency error and the clock error using two different SP signals, but may use three or more different SP signals. For example, the error detection unit 22 according to the first and second embodiments detects a first frequency error and a clock error by a combination of two SP signals, and a second frequency error and a clock error by a combination of the other two SP signals. A clock error is detected, a median value is obtained from the detected first frequency error, clock error, and second frequency error and clock error, and a median value of the frequency error is output to the frequency error correction unit 15-2. The median value of the clock error may be output to the clock error correction unit 20-2. Further, the frequency error and clock error of each of the three or more combinations of the two SP signals are detected, and an average value thereof is obtained to obtain the frequency error correction unit 15-2 and the clock error correction unit 20-2. Each may be output.

  As a hardware configuration of the OFDM wave measuring apparatus 1, a normal computer can be used. The OFDM wave measuring apparatus 1 is configured by a computer including a volatile storage medium such as a CPU and a RAM, a non-volatile storage medium such as a ROM, an interface, and the like. Orthogonal demodulation unit 13, error detection unit 14, frequency error correction units 15-1 and 15-2, symbol cutout units 16-1, 16-2 and 16-3, and FFT unit 17-included in the OFDM wave measuring apparatus 1. 1, 17-2, 17-3, symbol adders 18-1, 18-2, 18-3, SP pattern detector 19, clock error correctors 20-1, 20-2, SP extractor 21-1, The functions 21-2, the error detection unit 22, the received power calculation unit 23, the spectrum calculation unit 24, and the delay profile calculation unit 25 are realized by causing the CPU to execute a program describing these functions.

  Further, components other than the frequency conversion unit 11 and the A / D conversion unit 12 included in the OFDM wave measuring apparatus 1 of FIG. 1, that is, an orthogonal demodulation unit 13, an error detection unit 14, and frequency error correction units 15-1 and 15- 2, symbol extraction units 16-1, 16-2, 16-3, FFT units 17-1, 17-2, 17-3, symbol addition units 18-1, 18-2, 18-3, SP pattern detection Unit 19, clock error correction units 20-1 and 20-2, SP extraction units 21-1 and 21-2, error detection unit 22, received power calculation unit 23, spectrum calculation unit 24, and delay profile calculation unit 25. A measuring device can be configured. This measuring apparatus can also use a normal computer. Like the OFDM wave measuring apparatus 1 described above, a volatile storage medium such as a CPU and a RAM, a non-volatile storage medium such as a ROM, an interface, etc. Consists of a computer equipped. Each function of the quadrature demodulator 13 and the like provided in this measuring apparatus is realized by causing the CPU to execute a program describing these functions.

  In this case, the reception apparatus including the frequency conversion unit 11 and the A / D conversion unit 12 illustrated in FIG. 1 receives the OFDM signal by the reception antenna, and converts the digital IF signal converted by the A / D conversion unit 12. The received OFDM signal data is stored in the memory. Then, the measurement device stores the received OFDM signal data in the memory by downloading the received OFDM signal data stored in the memory of the receiving device or reading it through the storage device. Then, the measurement apparatus reads the received OFDM data from the memory, and executes a program describing the functions of the orthogonal demodulation unit 13 and the like. As a result, the OFDM signal received by the receiving device can be processed by the measuring device, and the received power and the like can be calculated.

  These programs can also be stored and distributed in a storage medium such as a magnetic disk (floppy (registered trademark) disk, hard disk, etc.), optical disk (CD-ROM, DVD, etc.), semiconductor memory, etc. You can also send and receive.

DESCRIPTION OF SYMBOLS 1 OFDM wave measuring device 11 Frequency conversion part 12 A / D conversion part 13 Orthogonal demodulation part 14 Error detection part 15 Frequency error correction part 16 Symbol extraction part 17 FFT part 18 Symbol addition part 19 SP pattern detection part 20 Clock error correction part 21 SP extractor 22 Error detector 23 Received power calculator 24 Spectrum calculator 25 Delay profile calculator

Claims (7)

In an OFDM wave measuring apparatus that receives an OFDM wave including a pilot signal, extracts the pilot signal, and measures the signal of the OFDM wave,
A quadrature demodulator for demodulating the received OFDM wave signal to generate a baseband signal;
A first error detection unit that adds a predetermined number of symbols on the time axis to the baseband signal generated by the orthogonal demodulation unit and detects a symbol head position, a frequency error, and a clock error by guard correlation When,
A first frequency error correction unit that corrects a frequency error detected by the first error detection unit with respect to the baseband signal generated by the orthogonal demodulation unit;
A baseband signal whose frequency error is corrected by the first frequency error correction unit is a first band for removing an GI and cutting out an effective symbol based on the symbol head position detected by the first error detection unit. A symbol cut-out section;
A first FFT unit that performs FFT on the effective symbols cut out by the first symbol cutout unit to generate carrier symbols;
A first symbol adding unit that synchronously adds the carrier symbols generated by the first FFT unit for each predetermined symbol and generates a synchronous addition result;
A pattern detection unit for calculating a correlation value between a synchronous addition result generated by the first symbol addition unit and a plurality of preset patterns, and detecting a pattern having the maximum correlation value;
A first clock error correction unit that corrects a clock error detected by the first error detection unit with respect to the carrier symbol generated by the first FFT unit;
A carrier symbol whose clock error has been corrected by the first clock error correction unit, a second symbol addition unit that synchronously adds the carrier symbols for each predetermined symbol, and generates a synchronous addition result;
A first pilot extraction unit that extracts a pilot signal from a carrier symbol of a synchronous addition result generated by the second symbol addition unit based on the pattern detected by the pattern detection unit;
A second error detection unit that calculates a deviation angle of the pilot signal extracted by the first pilot extraction unit and detects a frequency error and a clock error based on a change amount of the deviation angle;
A second frequency error correction unit that corrects the frequency error detected by the second error detection unit with respect to the baseband signal whose frequency error has been corrected by the first frequency error correction unit;
A second band that removes the GI and cuts out an effective symbol based on the symbol head position detected by the first error detector for the baseband signal whose frequency error has been corrected by the second frequency error corrector. A symbol cut-out section;
A second FFT unit that performs FFT on the effective symbols cut out by the second symbol cutout unit to generate carrier symbols;
A second clock error correction unit that corrects a clock error detected by the second error detection unit with respect to the carrier symbol generated by the second FFT unit;
A carrier symbol whose clock error is corrected by the second clock error correction unit, a third symbol addition unit that synchronously adds the carrier symbols for each predetermined symbol, and generates a synchronous addition result;
A second pilot extraction unit that extracts a pilot signal from a carrier symbol of a synchronous addition result generated by the third symbol addition unit based on the pattern detected by the pattern detection unit;
An OFDM wave measuring apparatus, wherein the OFDM wave signal is measured based on a pilot signal extracted by the second pilot extracting unit. In the OFDM wave measuring device according to claim 1,
The second symbol adder is
Further, the number of synchronous additions for each symbol is counted as the number of calculated symbols,
The second error detector is
Based on the number of calculated symbols counted by the second symbol adding unit, a predetermined first symbol number and a predetermined second symbol number larger than the first symbol number are determined, and the first symbol number is determined. Based on the pilot signal extracted by the first pilot extraction unit at the symbol number and the second symbol number, the deviation angle of the pilot signal is calculated, and the variation amount of the deviation angle on the time axis is calculated. An OFDM wave measuring apparatus, wherein a frequency error and a clock error are detected based on the error. In the OFDM wave measuring device according to claim 1 or 2,
The second error detector is
Based on a plurality of pilot signals arranged at predetermined different frequency positions from among the pilot signals extracted by the first pilot extraction unit, a change in declination per symbol for each of the plurality of pilot signals The amount of deviation is calculated and converted into the amount of deviation of the center frequency of the pilot signal, and the frequency error and clock error are detected using the amount of deviation of the center frequency in the plurality of pilot signals. An OFDM wave measuring apparatus characterized by that. In the OFDM wave measuring device according to claim 3,
An OFDM wave measuring apparatus, wherein the plurality of pilot signals are an SP signal having a lowest frequency and a CP signal having a highest frequency. In the OFDM wave measuring device according to claim 1 or 2,
The second error detector is
Among pilot signals extracted by the first pilot extraction unit, select a pilot signal having the highest amplitude value in each of a plurality of predetermined ranges on the frequency axis, and based on the selected plurality of pilot signals, A variation amount of a deviation angle per symbol is calculated for each of the plurality of pilot signals, the variation amount of the deviation angle is converted into a deviation amount of a center frequency of the pilot signal, and each center in the plurality of pilot signals is calculated. An OFDM wave measuring apparatus, wherein a frequency error and a clock error are detected using a frequency shift amount. In the OFDM wave measuring device according to claim 5,
The OFDM wave measuring apparatus characterized in that the plurality of predetermined ranges on the frequency axis are a range including an SP signal having the lowest frequency and a range including a CP signal having the highest frequency. Extracting the pilot signal from an OFDM wave signal including a pilot signal and measuring the OFDM wave signal;
A function of an orthogonal demodulator that orthogonally demodulates the signal of the OFDM wave and generates a baseband signal;
A first error detection unit that adds a predetermined number of symbols on the time axis to the baseband signal generated by the orthogonal demodulation unit and detects a symbol head position, a frequency error, and a clock error by guard correlation Functions and
A function of a first frequency error correction unit that corrects a frequency error detected by the first error detection unit with respect to the baseband signal generated by the orthogonal demodulation unit;
A baseband signal whose frequency error is corrected by the first frequency error correction unit is a first band for removing an GI and cutting out an effective symbol based on the symbol head position detected by the first error detection unit. The function of the symbol cutout part,
A function of a first FFT unit that performs an FFT on the effective symbol cut out by the first symbol cutout unit and generates a carrier symbol;
A function of a first symbol addition unit that synchronously adds the carrier symbols generated by the first FFT unit for each predetermined symbol and generates a synchronous addition result;
A function of a pattern detection unit that calculates a correlation value between a synchronous addition result generated by the first symbol addition unit and a plurality of preset patterns and detects a pattern having the maximum correlation value; ,
A function of a first clock error correction unit that corrects a clock error detected by the first error detection unit with respect to the carrier symbol generated by the first FFT unit;
A function of a second symbol addition unit that synchronously adds the carrier symbols whose clock error is corrected by the first clock error correction unit for each predetermined symbol, and generates a synchronous addition result;
A function of a first pilot extraction unit that extracts a pilot signal from a carrier symbol of a synchronous addition result generated by the second symbol addition unit based on the pattern detected by the pattern detection unit;
A function of a second error detection unit that calculates a deviation angle of the pilot signal extracted by the first pilot extraction unit and detects a frequency error and a clock error based on a variation amount of the deviation angle;
A function of a second frequency error correction unit for correcting the frequency error detected by the second error detection unit with respect to the baseband signal whose frequency error has been corrected by the first frequency error correction unit;
A second band that removes the GI and cuts out an effective symbol based on the symbol head position detected by the first error detector for the baseband signal whose frequency error has been corrected by the second frequency error corrector. The function of the symbol cutout part,
A function of a second FFT unit that performs FFT on the effective symbols cut out by the second symbol cutout unit to generate carrier symbols;
A function of a second clock error correction unit that corrects a clock error detected by the second error detection unit with respect to the carrier symbol generated by the second FFT unit;
A function of a third symbol addition unit that synchronously adds the carrier symbol whose clock error is corrected by the second clock error correction unit for each predetermined symbol, and generates a synchronous addition result;
A function of a second pilot extraction unit that extracts a pilot signal from a carrier symbol of a synchronous addition result generated by the third symbol addition unit based on the pattern detected by the pattern detection unit;
A program to realize

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