JP2017173114A - Distance measuring system and distance measuring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a distance measuring system and a distance measuring method that can reliably detect an unauthorized communication with a simple configuration.SOLUTION: A communication master 15 transmits a first ultrabroadband radio wave S1 and a second ultrabroadband radio wave S2 having different frequencies from each other to a terminal 13, and causes both of the transmission side (the communication master 15) and the reception side (the terminal 13) to generate a beat signal Be. The terminal 13 then transmits information on the beat signal Be generated by itself to the communication mater 15 at a different frequency (in UHF band) from that of ultrabroadband communication. A CPU 45 compares the beat signal Be1 at the communication master 15 side with the beat signal Be1 at the terminal 13 side to thereby calculate distance d2 from the terminal 13.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a distance measuring system and a distance measuring method for measuring a distance between a communication master and a terminal.

  Conventionally, a technique for transmitting a radio wave from a communication master (base station) to a terminal, retransmitting the radio wave from the terminal receiving the radio wave to the base station, and measuring a distance between the two from a signal received by the communication master is well known. (See Patent Documents 1 to 5). This is because, for example, unauthorized communication using a repeater, so-called “relay”, is detected and communication is not permitted in this case. In this type of technology, it is generally known to use an ultra-wideband radio wave (UWB radio wave) for transmitting and receiving radio waves. The ultra-wideband radio wave is composed of, for example, an extremely short pulse radio wave.

JP-A-9-170364 Japanese Patent Laid-Open No. 2003-13644 JP 2006-512515 A Special table 2008-515315 gazette JP 2012-088141 A

In this type of technology, there is a need to reliably detect unauthorized communication (relay) with a simple configuration.
An object of the present invention is to provide a distance measuring system and a distance measuring method capable of reliably detecting unauthorized communication with a simple configuration.

  A distance measurement system that solves the above problem generates a beat signal based on a plurality of radio waves in the communication master, and a radio wave transmission unit that transmits radio waves of a plurality of different frequencies within the ultra-wideband radio wave band from the communication master. A first signal generation unit, a second signal generation unit that receives a plurality of the radio waves transmitted from the communication master at a terminal, and generates a beat signal at the terminal, and a beat generated by the second signal generation unit Beat information related to a signal, an information notifying unit that transmits the signal from the terminal to the communication master at a different frequency, the beat signal generated by the first signal generating unit, and the beat signal information acquired from the terminal And a distance measuring unit for measuring the distance between the communication master and the terminal.

  According to this configuration, a plurality of radio waves having different frequencies within the same band are transmitted from the communication master, a beat signal is generated on each of the transmission side and the reception side, and these beat signals are compared, thereby comparing the communication master and the terminal. When measuring the distance between them, the radio waves are set to different frequencies for communication from the communication master to the terminal and for communication from the terminal to the communication master. Therefore, unauthorized communication can be reliably detected with a simple configuration.

  In the distance measurement system, the beat signal information is preferably phase information related to the beat signal or the beat signal itself. According to this configuration, it is advantageous to acquire the beat signal on the terminal side more correctly.

  In the distance measurement system, the radio wave transmission unit can transmit a plurality of radio waves transmitted from the communication master by changing a combination of frequencies, and the distance measurement unit can transmit the radio waves in a first combination. The distance of the terminal calculated with the wavelength of the beat signal sometimes obtained as the measurement range and the distance of the terminal calculated with the wavelength of the beat signal obtained when the second combination different from the first combination as the measurement range And the distance between the communication master and the terminal is preferably specified from the least common multiple of these distances. According to this configuration, the terminal position calculated at the time of measurement appears with repetition of the wavelength of the beat signal determined from the combination of radio waves, but the terminal position is determined by taking the least common multiple of the wavelength of the distance for each combination. Since it is specified, it is advantageous to correctly specify the position of the terminal.

  In the distance measurement system, it is preferable that the first signal generation unit, the second signal generation unit, and the information notification unit include a beat extraction circuit having a detector. According to this configuration, it is advantageous to correctly extract the beat signal by the detector.

  In the distance measurement system, the communication master includes a radar device that reflects a transmitted radio wave to a target and receives the reflected radio wave, and measures a distance from the target based on the reflected radio wave, The radio wave transmission unit preferably transmits at least one of the radio waves using the radar device when transmitting a plurality of radio waves having different frequencies. According to this configuration, since the radar apparatus can be shared when measuring the distance between the communication master and the terminal, it is further advantageous to correctly detect unauthorized communication with a simple configuration.

  In the distance measurement system, the radar device may measure the distance between the communication master and the terminal by a stepped FM communication method that performs distance measurement based on the phase difference between the transmitted and received beat signals. preferable. According to this configuration, the distance between the communication master and the terminal can be measured through the stepped FM that has a simple configuration and high noise resistance.

  In the distance measurement system, it is preferable that the radar apparatus measures a distance between the communication master and the terminal by a fast chirp communication method that performs distance measurement based on a frequency difference between the transmitted and received beat signals. . According to this configuration, it is possible to measure the distance between the communication master and the terminal through fast chirp with a simple configuration and strong noise resistance.

  In the distance measurement system, the terminal includes a low-frequency oscillator that can output a signal having a frequency lower than the frequency of the beat signal, and the information notification unit transmits the beat signal information to the communication master. It is preferable to use existing hardware in the terminal by enabling transmission of a signal modulated by the frequency of the low-frequency oscillator. According to this configuration, it is possible to transmit radio waves from the terminal to the communication master using the radar device already installed in the terminal, so that the configuration of the terminal is not complicated.

  In the distance measurement system, the radio wave transmission unit generates a frequency signal based on an output from a synthesizer capable of generating a plurality of frequencies, and transmits the frequency signal as a first ultra wideband radio wave from the communication master. It is preferable that a signal is generated by synthesizing outputs of an oscillator capable of generating only a frequency and the synthesizer, and this is transmitted from the communication master as a second ultra wideband radio wave. According to this configuration, since only one synthesizer is required for the radio wave transmission unit, it is further advantageous to correctly detect unauthorized communication with a simple configuration.

  In the distance measuring system, based on the distance calculated by the distance measuring unit, it is determined whether the established communication is correct or not, and if the distance is less than a specified value, the communication is normal. If is equal to or greater than a specified value, it is preferable to include a communication correctness determination unit that processes that communication is illegal. According to this configuration, it is possible to determine whether the communication that is currently established is normal or illegal.

  A distance measurement method that solves the above problem includes a radio wave transmission step of transmitting radio waves of a plurality of different frequencies within the ultra-wideband radio wave band from a communication master, and generating a beat signal based on the plurality of radio waves in the communication master. A first signal generation step; a second signal generation step of receiving a plurality of radio waves transmitted from the communication master at the terminal; and generating a beat signal at the terminal; and the beat generated at the second signal generation step An information notification step of transmitting beat signal information related to a signal from the terminal to the communication master at a different frequency, the beat signal generated in the first signal generation step, and the beat signal information acquired from the terminal And a distance measuring step for measuring a distance between the communication master and the terminal.

  According to the present invention, unauthorized communication can be reliably detected with a simple configuration.

The lineblock diagram of the distance measuring system of a 1st embodiment. Explanatory drawing which shows the specific example of the communication aspect of stepped FM. The wave form diagram which shows the output change of a 1st synthesizer and a 2nd synthesizer. Radar mode operation diagram. Operation diagram of transponder mode. (A)-(d) is a signal waveform figure in each point of "A"-"D" of a terminal. The wave form diagram of a 1st beat signal and a 2nd beat signal. The wave form diagram which shows the illustration of the frequency of a beat signal. A table summarizing various parameters of beat signals in each combination. The block diagram of the distance measurement system of 2nd Embodiment. Radar mode operation diagram. Operation diagram of transponder mode. Explanatory drawing which shows the method of the distance measurement in radar mode. The block diagram of the terminal of another example.

(First embodiment)
Hereinafter, a first embodiment of a distance measurement system and a distance measurement method will be described with reference to FIGS.

  As shown in FIG. 1, the vehicle 1 includes a radar device 2 that searches for an object (target) existing around the vehicle 1. The radar apparatus 2 of this example is based on a stepped FM communication method capable of measuring a distance based on a phase difference between transmission and reception radio waves as disclosed in Patent Document 5 cited in “Background Art”, for example. An object around the vehicle 1 is detected. The stepped FM transmits a transmission radio wave (in this example, the first ultra-wideband radio wave S1) from the vehicle 1 while changing the frequency stepwise, receives the reflected radio wave S1 ′ reflected by the target, and receives the reflected radio wave S1 ′. This is a method of calculating the distance d1 between the target by sweeping the frequency over a wide band and collecting the phase difference between the transmitted radio wave and the reflected radio wave S1 ′ for each frequency.

  Note that the measurement of the distance d1 is not an essential constituent element of this example, and the idea of this example is a distance measurement method that uses the function of the radar apparatus 2 that measures the distance d1. That is, in the technical idea, since the distance d1 is measured using reflection of an ultra wide band (UWB) radio wave, a measurement system for the distance d1 is not necessarily required. However, in the case of this example, an example will be described in which the measured distance d1 is used for determination of unauthorized communication.

  In the case of this example, the radar apparatus 2 includes a CPU 3, a first synthesizer 4, a phase modulator 5, a circulator 6, a transmission / reception antenna 7, a phase detector 8, an AD converter 9, and a batch synthesis processing unit 10. The CPU 3 controls the operation of the radar apparatus 2 and controls the frequency of the radio wave transmitted from the radar apparatus 2. The first synthesizer 4 is an oscillator and outputs a first frequency signal D1 that is the source of an ultra-wideband radio wave. The phase modulator 5 superimposes a carrier wave on the pulsed first frequency signal D1 input from the first synthesizer 4. The circulator 6 outputs an input in only one direction between the terminals. The transmission / reception antenna 7 can transmit and receive radio waves for ultra-wideband communication, and can transmit radio waves according to the first frequency signal D1 (first ultra-wideband radio wave S1) to the outside. The first ultra-wideband radio wave S1 is reflected by a target existing around the vehicle 1 and reaches the transmitting / receiving antenna 7 as a reflected radio wave S1 '.

  The transmission / reception antenna 7 outputs the radar reception signal D1 'to the phase detector 8 through the circulator 6 when receiving the reflected radio wave S1' from the target. The phase detector 8 performs phase detection between the first frequency signal D1 and the radar reception signal D1 '. The AD converter 9 performs A / D conversion on the signal input from the phase detector 8. The batch synthesis processing unit 10 performs batch synthesis processing such as inverse discrete Fourier transform on the signal after A / D conversion. The radar apparatus 2 measures the distance d1 from the target to be searched based on the signal after the batch conversion process.

  The vehicle 1 includes a distance measuring system 14 that measures a distance d2 between the terminal 13 and the terminal 13 that can communicate with the vehicle 1. The distance measurement system 14 of this example transmits radio waves of two frequencies (in this example, the first ultra wideband radio wave S1 and the second ultra wideband radio wave S2) from the communication master 15 (in this example, the vehicle 1), Each receiving side generates a beat signal Be and compares the beat signals Be to measure the distance d2 between the vehicle 1 and the terminal 13. Based on the distance d2 obtained by the distance measurement system 14, the vehicle 1 permits communication with the terminal 13 if the distance d2 is less than the specified value, and relays communication if the distance d2 is equal to or greater than the specified value. Therefore, communication with the terminal 13 is not permitted.

  The distance measurement system 14 of this example has a device configuration using the radar device 2. That is, the distance d2 between the vehicle 1 and the terminal 13 is calculated using the hardware of the radar device 2.

  The distance measuring system 14 transmits a radio wave transmitter 18 (a first ultra-wideband radio wave S1 and a second ultra-wideband radio wave S2) having a plurality of different frequencies within the ultra-wideband radio wave band from the communication master 15 (vehicle 1). Radio wave transmission step), and a first signal generation unit 19 (first signal generation step) that generates a beat signal Be based on a plurality of radio waves (first ultra wideband radio wave S1 and second ultra wideband radio wave S2) in the communication master 15; The terminal 13 receives a plurality of radio waves (first ultra wideband radio wave S1 and second ultra wideband radio wave S2) transmitted from the communication master 15 and generates a beat signal Be at the terminal 13 ( A second signal generation step). Further, the distance measurement system 14 transmits the beat signal information Sbe of the beat signal Be generated by the second signal generation unit 20 from the terminal 13 to the communication master 15 at another frequency (for example, UHF (Ultra High Frequency) band). A notification unit 21 (information notification step) and a distance measurement unit 22 (distance measurement step) that measures the distance d2 between the communication master 15 and the terminal 13 are provided. The beat signal information Sbe may be either the phase information Dφ of the received beat signal Be1 '(second beat signal Be2) or the beat signal Be1' itself. The distance measuring unit 22 is based on the beat signal Be (first beat signal Be1) generated by the first signal generating unit 19 and the beat signal Be (second beat signal Be2) obtained via the terminal 13. Then, the distance d2 between the communication master 15 and the terminal 13 is measured.

  The distance measurement system 14 includes a communication correctness determination unit 23 that determines whether communication is correct based on the distance d2 calculated by the distance measurement unit 22. The communication correctness determination unit 23 of this example is now established by comparing the distance d2 calculated by the distance measurement unit 22 with a predetermined specified value that is a criterion for determining whether the communication is performed by the repeater. Judge whether communication is right or wrong. That is, the communication correctness determination unit 23 determines that the communication is normal if the distance d2 calculated by the distance measurement unit 22 is less than the specified value, and the communication is invalid if the distance d2 is equal to or greater than the specified value. Process if there is.

  The radio wave transmission unit 18 is provided in the communication master 15 and has a configuration using the radar device 2. More specifically, the radio wave transmission unit 18 includes a first synthesizer 4, phase modulators 5 and 25, a circulator 6, a transmission / reception antenna 7, a second synthesizer 26, and a transmission antenna 27. The second synthesizer 26 is an oscillator and outputs a second frequency signal D2 having a frequency and phase different from those of the first frequency signal D1. The phase modulator 25 superimposes a carrier wave on the pulsed second frequency signal D2 input from the second synthesizer 26. The transmission antenna 27 can transmit an ultra-wideband radio wave (second ultra-wideband radio wave S2) and can transmit a radio wave according to the second frequency signal D2 to the outside.

  The first signal generator 19 is provided in the communication master 15 and includes an adder 30 and a beat extraction circuit 31. The adder 30 is a circuit that adds the first frequency signal D1 and the second frequency signal D2. The beat extraction circuit 31 includes a circuit group such as a detector and a bandpass filter. The beat extraction circuit 31 extracts the beat signal Be (first beat signal Be1) from the sum signal of the first frequency signal D1 and the second frequency signal D2 input via the adder 30, and supplies this to the distance measurement unit 22 in the subsequent stage. Output.

  The second signal generation unit 20 is provided in the terminal 13 and includes a reception antenna 32 and a beat extraction circuit 33. The reception antenna 32 can receive the ultra-wideband radio waves (the first ultra-wideband radio wave S1 and the second ultra-wideband radio wave S2) transmitted from the transmission / reception antenna 7 and the transmission antenna 27. The beat extraction circuit 33 extracts the beat signal Be (reception beat signal Be1 ') from the ultra-wideband radio wave received by the reception antenna 32, and outputs this to the information notification unit 21 at the subsequent stage.

  The information notification unit 21 includes an information notification unit 21 a provided in the terminal 13 and an information notification unit 21 b provided in the communication master 15. The information notification unit 21a includes an amplitude modulator 36, a low frequency oscillator 37, a pulse modulator 38, and a transmission antenna 39. The amplitude modulator 36 converts the amplitude of the received beat signal Be1 'based on the low frequency fLo output from the low frequency oscillator 37. The pulse modulator 38 modulates the signal (amplitude modulation signal Ss1) input from the amplitude modulator 36 into a pulse shape. The transmission antenna 39 can transmit, for example, UHF radio waves, and transmits radio waves (information on the received beat signal Be1 ') according to the amplitude modulation signal Ss1 to the outside.

  The information notification unit 21 b includes a reception antenna 40, an amplifier 41, and a beat extraction circuit 42. The receiving antenna 40 can receive a radio wave having a frequency different from that of the ultra-wideband communication (in this example, a UHF radio wave), and receives the radio wave transmitted from the terminal 13. The amplifier 41 is composed of, for example, an LNA (low noise amplifier). The beat extraction circuit 42 extracts the beat signal Be (second beat signal Be2) from the reception signal of the reception antenna 40, and outputs this to the distance measurement unit 22 at the subsequent stage.

  The distance measuring unit 22 is provided in the communication master 15 and includes a CPU 45 and an AD converter 46. The CPU 45 takes in the first beat signal Be 1 output from the beat extraction circuit 31 through the AD converter 46 and takes in the second beat signal Be 2 output from the beat extraction circuit 42 through the AD converter 46. Then, the CPU 45 calculates a distance d2 between the communication master 15 and the terminal 13 based on the first beat signal Be1 and the second beat signal Be2 after AD conversion.

Next, the operation of the distance measurement system 14 will be described with reference to FIGS.
[Radar mode]
FIG. 2 shows a communication mode of radio waves transmitted from the transmission / reception antenna 7 in a stepped FM format. As shown in the figure, in the case of stepped FM communication, the radio wave transmitted from the transmission / reception antenna 7 is an unmodulated wave (CW wave), and the frequency of the radio wave is switched step by step in the course of communication. . In the example of the figure, the frequency of the radio wave transmitted by the stepped FM is switched in the order of f ₁ , f ₂ ... F _n (n is an integer). The advantage of the stepped FM is that a frequency band that is not used can be arbitrarily set. For example, when noise is detected in a communication environment, it is possible to secure anti-jamming wave characteristics by setting the frequency of this noise to a band not used for communication.

  As shown in FIG. 4, when it is time to measure the distance d1 with the target outside the vehicle, the CPU 3 follows the stepped FM communication format from the first synthesizer 4 with the frequency “f1” and the phase “ The first frequency signal D1 of “φ1” is output. The first frequency signal D1 is transmitted from the transmission / reception antenna 7 to the outside of the vehicle as a first ultra-wideband radio wave S1 having a frequency “f1” and a phase “φ1”. The first frequency signal D1 is input to the phase detector 8.

  The first ultra wideband radio wave S1 transmitted from the transmission / reception antenna 7 is reflected by the target, becomes a reflected radio wave S1 'having a frequency of "f1" and a phase of "φ2", and is received by the transmission / reception antenna 7. That is, the transmission / reception antenna 7 captures the reflected radio wave S1 'reflected from the target as a radar reception signal D1' having the same frequency as the first ultra-wideband radio wave S1, but having a different phase. A radar reception signal D <b> 1 ′ captured through the transmission / reception antenna 7 is input to the phase detector 8 via the circulator 6.

  The phase detector 8 compares the phase of the first frequency signal D1 and the radar reception signal D1 ′, and performs a batch synthesis process on the obtained phase difference φd, that is, (φdi, φdg) of orthogonal I / Q signals through the AD converter 9. To the unit 10. This phase difference calculation is performed for each frequency of radio waves transmitted and received. Then, based on the acquired phase difference φd of each frequency, the batch synthesis processing unit 10 performs an operation such as inverse discrete Fourier transform, and calculates a distance d1 from the target. In this way, by sweeping the frequency of radio waves to be transmitted and received in a wide band and collecting the phase difference for each frequency, it is possible to provide the radar apparatus 2 that has pseudo-wide band radio waves transmitted.

[Transponder mode]
As shown in FIG. 5, when it is time to measure the distance d <b> 2 with the terminal 13, the CPU 3 outputs the first frequency signal D <b> 1 having the frequency “f1” and the phase “φ1” from the first synthesizer 4. Let The first frequency signal D1 output from the first synthesizer 4 at this time is the same as the first frequency signal D1 in the radar mode for convenience, but it is changed to a signal having another frequency and phase. May be. The transmitting / receiving antenna 7 transmits the first frequency signal D1 as the first ultra-wideband radio wave S1 having the frequency “f1” and the phase “φ1”.

  Further, the second synthesizer 26 outputs the second frequency signal D2 having the frequency “f2” and the phase “φ2” to the transmitting antenna 27 through the phase modulator 25. Note that the frequency and phase of the second frequency signal D2 can be appropriately changed to other values. The transmitting antenna 27 transmits the second frequency signal D2 as the second ultra wideband radio wave S2 having the frequency “f2” and the phase “φ3”.

  As shown in FIG. 3, the first synthesizer 4 and the second synthesizer 26 change in the same manner as the stepped FM. Therefore, the waveform changes with the frequency gradually changing stepwise while synchronizing the change timing. Take. At this time, the outputs of the first synthesizer 4 and the second synthesizer 26 change stepwise while the shift amount of the frequency Δf between the first beat signal Be1 and the second beat signal Be2 is maintained.

  Returning to FIG. 5, the first frequency signal D1 and the second frequency signal D2 are added by the adder 30 in the communication master 15, and the added signal is passed through the beat extraction circuit 31 to the beat signal Be on the communication master 15 side. It is extracted as a certain first beat signal Be1. The first beat signal Be1 extracted from the beat extraction circuit 31 is output to the CPU 45 through the AD converter 46.

  The terminal 13 receives the first ultra wideband radio wave S1 transmitted from the transmission / reception antenna 7 and the second ultra wideband radio wave S2 transmitted from the transmission antenna 27 by the reception antenna 32. Since the first ultra-wideband radio wave S1 and the second ultra-wideband radio wave S2 have different frequencies, they do not interfere with each other. Since the terminal 13 receives the first ultra-wideband radio wave S1 and the second ultra-wideband radio wave S2 at the same time, the terminal 13 receives the beat signal Be (received beat) obtained by adding the first ultra-wideband radio wave S1 and the second ultra-wideband radio wave S2. The signal Be1 ′) is automatically generated.

  FIGS. 6A to 6D show the signals “point A”, “point B”, “point C”, and “point D” in FIG. At “point A” shown in FIG. 6A, a signal in which the frequency f1 of the first ultra-wideband radio wave S1 and the frequency f2 of the second ultra-wideband radio wave S2 are combined appears. A waveform obtained by detecting this synthesized wave corresponds to the frequency Δf of the beat signal Be in the terminal 13.

  At “point B” shown in FIG. 6B, a combined beat of the first ultra-wideband radio wave S1 and the second ultra-wideband radio wave S2 is passed through the beat extraction circuit 33, thereby generating a received beat signal Be1 ′. . The received beat signal Be1 'is input to the amplitude modulator 36.

  At “point C” shown in FIG. 6C, the amplitude modulator 36 superimposes the frequency fLo of the low-frequency oscillator 37 on the received beat signal Be1 ′ in the amplitude modulator 36, thereby generating the amplitude modulation signal Ss1. This is because when the frequency of the reception beat signal Be1 'is notified from the terminal 13 to the communication master 15, the terminal 13 sends it back on a frequency that can be originally transmitted (for example, 315 MHz or 433 MHz). Specifically, for example, when the terminal 13 is an electronic key, the electronic key is already provided with hardware for transmitting UHF radio waves, and the frequency of the reception beat signal Be1 ′ is returned to the communication master 15 using the hardware. Like that.

  At “point D” shown in FIG. 6D, the amplitude modulation signal Ss1 is passed through the pulse modulator 38, whereby the phase information Dφ is generated. Then, this phase information Dφ is UHF transmitted from the transmission antenna 39 of the terminal 13 to the communication master 15. Note that the phase information Dφ may be a signal representing the phase of the received beat signal Be1 '. Further, the information of the reception beat signal Be1 'generated by the terminal 13 is not limited to the phase information Dφ but may be, for example, the reception beat signal Be1' itself.

  Returning to FIG. 5, the communication master 15 receives the phase information Dφ transmitted from the terminal 13 by UHF with the receiving antenna 40 already installed in the communication master 15. The phase information Dφ received by the receiving antenna 40 is input to the beat extraction circuit 42 via the amplifier 41, and the beat extraction circuit 42 extracts the beat signal Be (second beat signal Be2) from the phase information Dφ. The second beat signal Be2 extracted by the beat extraction circuit 42 is output to the CPU 45 through the AD converter 46.

  As shown in FIG. 7, the CPU 45 calculates the phase difference Δφ between the first beat signal Be1 generated on the communication master 15 side and the second beat signal Be2 acquired from the terminal 13, and from this phase difference Δφ The distance d2 between the communication master 15 and the terminal 13 is obtained. Note that the phase difference Δφ in this example corresponds to a value required for a round trip from when the radio wave is transmitted from the communication master 15 to when it is returned from the terminal 13. Therefore, in calculating the distance d2 between the communication master 15 and the terminal 13, the distance d2 may be obtained in consideration of this point.

  Here, the wavelength λ of the beat signal Be will be considered with reference to FIG. Note that the beat signal Be refers to a composite wave in which the frequency difference between f1 and f2, that is, two waves having slightly different frequencies interfere with each other and the amplitude slowly and periodically changes. FIG. 8 illustrates the waveform of the beat signal Be when the frequency f1 of the first ultra-wideband radio wave S1 is “1” and the frequency f2 of the second ultra-wideband radio wave S2 is “0.9”.

  As illustrated in FIG. 8, when the frequency difference between the first ultra-wideband radio wave S1 and the second ultra-wideband radio wave S2 is small and the frequency f1 of the first ultra-wideband radio wave S1 is “1”, the second ultra-wideband radio wave When the frequency f2 of S2 is set to a slightly small frequency (such as x0.99), the wavelength λ of the beat signal Be can be set to about 10 to 1000 times the frequency f1 of the first ultra wideband radio wave S1. In broadband communication, since a frequency of about 7 GHz is used, the wavelength is assumed to be about 43 mm. Then, the beat signal Be changes from 4.3 m (a set of f1: 7.00 GHz and f2: 6.93 GHz) to 6.1 m (a set of f1: 7.00 GHz and f2: 6.951 GHz).

  When the measurement is performed a plurality of times by changing the combination of the frequencies f1 and f2, a plurality of results are obtained in which an advance is made by an amount obtained by adding Δφ to the N period (N: integer). In one measurement, the value of the cycle “N” is not known, but if the measurement is repeated a plurality of times by changing the combination of the frequencies f1 and f2, the cycle “N” can be estimated. For example, the beat signal Be is set so that the wavelength λ is “10 cm”, Δφ is “0”, the wavelength λ is “12 cm”, Δφ is “1 / 3λ”, and the wavelength λ Is set to be “15 cm”, and Δφ is “3 / 4λ”, the distance d2 is an integral multiple of “100 cm”. Similarly, the wavelength λ of the beat signal Be is set to “10 m”, Δφ is set to “1 / 10λ”, the wavelength λ is set to “12 m”, and Δφ is set to “1 / 12λ”. When the wavelength λ is set to be “15 m” and Δφ is “1 / 15λ”, the wavelength λ is an integral multiple of 1 m + (the least common multiple of 10, 12, 15 = 60) m.

  As described above, the radio wave transmission unit 18 can transmit a plurality of radio waves (first ultra wideband radio wave S1 and second ultra wideband radio wave S2) transmitted from the vehicle 1 by changing the combination of frequencies. The distance measurement unit 22 then calculates the distance d2 of the terminal 13 calculated using the wavelength λ of the beat signal Be obtained when the ultra-wideband radio wave is the first combination as a measurement range, and a second combination different from the first combination The distance d2 of the terminal 13 calculated with the wavelength λ of the beat signal Be obtained at the time as the measurement range is obtained, and the final distance d2 is specified from the least common multiple of these distances d2.

  For example, as shown in FIG. 9, when the first ultra-wideband radio wave S1 and the second ultra-wideband radio wave S2 are in the first combination in the figure, the frequency Δf of the beat signal Be is 600 KHz, and the wavelength λ of the beat signal Be is 500 m. It becomes. In this case, for example, when communication is normally performed in the vicinity of the vehicle, the measured distance d2 is a considerably short distance such as 1 m, and even if there is an error of ± 10 m, a relay that is 10 to 490 m away can be detected. However, since 501 m and 1 m are separated by one wavelength and cannot be distinguished, the distance d <b> 2 is measured in the same manner with the second combination in the figure in which the frequency value is changed. Then, the final distance d2 is specified from the least common multiple “1500” of the wavelength λ of the beat signal Be in the first combination and the wavelength λ of the beat signal Be in the second combination. The least common multiple at this time is “1500”, that is, it becomes possible to detect a relay of 1.5 km. The CPU 45 calculates the distance d2 between the communication master 15 and the terminal 13 from the difference between the first beat signal Be1 and the second beat signal Be2 in accordance with the above concept.

  If it is confirmed that the distance d2 is less than the specified value, the communication correctness determination unit 23 processes communication (smart communication) with the terminal 13 as established. On the other hand, if the communication correctness determination unit 23 confirms that the distance d2 is equal to or greater than the specified value, the communication may be relayed, and the communication (smart communication) with the terminal 13 is processed as not established. . As a result, even if a third party attempts to establish communication illegally using a repeater or the like, it is not necessary to shift this to establishment.

  Note that the distance d1 may be measured in the previous radar mode, and the distance d2 may be further measured in the transponder mode when there is an object near the threshold. The distance d2 may be measured in the transponder mode regardless of the distance d1, but when associated with the distance d1, the radar mode is normally operated at a high frequency for monitoring whether or not an object is nearby. When an object approaches, the transponder mode can be continuously activated for a certain period of time to start the measurement of the distance d2. Therefore, such mode switching can be realized.

According to the configuration of the present embodiment, the following effects can be obtained.
(1) A plurality of radio waves (first ultra wideband radio wave S1 and second ultra wideband radio wave S2) having different frequencies within the same band are transmitted from the communication master 15, and a beat signal Be is generated on each of the transmission side and the reception side. In measuring the distance d2 between the communication master 15 and the terminal 13 by comparing these beat signals Be, the communication from the communication master 15 to the terminal 13 and the communication from the terminal 13 to the communication master 15 are respectively performed. Set the radio wave to another frequency. Therefore, it is advantageous to accurately detect unauthorized communication (relay) using a repeater. In addition, since it is possible to make the communication circuit of one side of the radio wave transmission / reception (in this example, the terminal 13) simple, unauthorized communication can be reliably detected with a simple configuration.

  (2) Since it is possible to measure the distance d2 of the terminal 13 simply by obtaining the phase difference of the radio wave, a circuit (clock) for accurately measuring the reception time of the radio wave is not required. This is even more advantageous for simplification.

  (3) Since the distance d2 is measured by changing the frequency used for distance measurement with time, even if a strong noise of one wave exists in the communication environment, the distance d2 is not affected by this. Can be measured. Therefore, the distance d2 can be measured in a manner with high noise resistance.

  (4) The terminal 13 is an electronic key that is wirelessly authenticated by the communication master 15. Therefore, it is possible to measure how far the electronic key is located from the communication master 15 at the distance d2 in a manner strong against noise.

  (5) The distance measurement unit 22 calculates the distance d2 calculated using the wavelength λ of the beat signal Be obtained when the radio waves (the first ultra wideband radio wave S1 and the second ultra wideband radio wave S2) are in the first combination as a measurement range; The distance d2 calculated using the wavelength λ of the beat signal Be obtained when the radio wave is the second combination as a measurement range is obtained, and the final distance d2 is specified from the least common multiple of these distances d2. Therefore, although the position of the terminal 13 calculated at the time of measurement appears with repetition of the wavelength λ of the beat signal Be determined from the combination of radio waves, the terminal is calculated by taking the least common multiple of the wavelength λ of the distance for each radio wave combination. Since the position of 13 is determined, it is advantageous to correctly specify the position of the terminal 13.

  (6) The first signal generation unit 19, the second signal generation unit 20, and the information notification unit 21b include beat extraction circuits 31, 33, and 42 each having a detector. Therefore, it is advantageous for correctly taking out the beat signal Be by the detector.

  (7) The distance measurement system 14 calculates the distance d2 between the communication master 15 and the terminal 13 by using the radar device 2 that is mounted in the communication master 15 in advance. Therefore, since the radar apparatus 2 can be shared, it is more advantageous to correctly detect unauthorized communication with a simple configuration.

  (8) The distance measurement system 14 calculates the distance d2 to the terminal 13 using the radar device 2 that measures the distance d1 to the target by the stepped FM communication method. Therefore, the distance d2 between the communication master 15 and the terminal 13 can be measured through the communication of the stepped FM having a simple configuration and strong noise resistance.

  (9) The terminal 13 includes a low frequency oscillator 37 that can output a signal having a frequency fLo lower than the frequency Δf of the beat signal Be. The information notification unit 21a enables transmission of a signal modulated by the frequency fLo of the low-frequency oscillator 37 when transmitting the phase information Dφ or the received beat signal Be1 ′ itself to the communication master 15, so that the information notification unit 21a is already installed in the terminal 13. Use hard. Therefore, since it is not necessary to provide a new communication function in the terminal 13, the configuration of the terminal 13 is not complicated.

(Second Embodiment)
Next, a second embodiment will be described with reference to FIGS. In addition, 2nd Embodiment is an Example which changed the communication system of the electromagnetic wave in 1st Embodiment. Therefore, the same parts as those in the first embodiment are denoted by the same reference numerals, description thereof is omitted, and only different parts are described in detail.

  As shown in FIG. 10, the radar apparatus 2 of this example detects objects around the vehicle 1 by a Fast Chirp communication method capable of measuring a distance based on a frequency difference between transmitted and received radio waves. To do. The fast chirp receives a reflected radio wave S1 ′ that is transmitted from the vehicle 1 while continuously changing the frequency (in this example, the first ultra-wideband radio wave S1) and is reflected by the target, and the signal and the reflected radio wave are reflected. In this method, the distance d1 between the target and the target is calculated by acquiring the mixer output by mixing with the signal of the radio wave S1 ′.

  The radar apparatus 2 mixes the first frequency signal D1 output from the synthesizer 4 and the radar received signal D1 ′ received from the terminal 13 by the mixer 50, and the mixer output (signal phase difference) is converted to an AD converter. 9 to the inverse discrete Fourier transform unit 51. The inverse discrete Fourier transform unit 51 calculates the distance d1 between the communication master 15 and the terminal 13 based on the mixer output after AD conversion.

  The radio wave transmission unit 18 of this example includes a synthesizer 4, a circulator 6, a transmission / reception antenna 7, a transmission antenna 27, an oscillator (CW Generator) 52, a mixer 53, and a bandpass filter 54. As described above, the radio wave transmission unit 18 of the present example has a configuration including only one synthesizer 4, and the apparatus cost is reduced compared to the case where a plurality of synthesizers 4 are included. The oscillator 52 outputs a frequency signal D2 'required for generating the second ultra-wideband radio wave S2 to the mixer 53, and generates a signal that is the source of the second ultra-wideband radio wave S2. In the case of this example, the frequency of the frequency signal D2 'is, for example, "f2."

Next, operation | movement of the distance measurement system 14 is demonstrated using FIGS. 11-13.
[Radar mode]
As shown in FIG. 11, when it is time to measure the distance d1 with the target outside the vehicle, the CPU 3 follows the Fast Chirp communication format and the frequency is “f” and the phase is “φ1” from the synthesizer 4. The first frequency signal D1 is output. The first frequency signal D1 is transmitted from the transmission / reception antenna 7 to the outside of the vehicle as a first ultra-wideband radio wave S1 having a frequency “f1” and a phase “φ1”. The first frequency signal D1 is input to the mixer 50.

  The first ultra-wideband radio wave S1 transmitted from the transmission / reception antenna 7 is reflected by the target, becomes a reflected radio wave S1 'having a frequency of “f + Δf” and a phase of “φ2”, and is received by the transmission / reception antenna 7. That is, the transmitting / receiving antenna 7 captures the reflected radio wave S1 'reflected from the target as a radar reception signal D1' having a frequency and phase different from those of the first ultra wideband radio wave S1. A radar reception signal D <b> 1 ′ captured through the transmission / reception antenna 7 is input to the mixer 50 via the circulator 6.

  As shown in FIG. 12, when the communication master 15 combines the first frequency signal D1 and the radar reception signal D1 ′ with the mixer 50, the mixer output Mout takes a trapezoidal waveform as shown in FIG. . In fast chirp communication, the maximum amplitude Mout-max of the mixer output Mout is determined according to the distance d1 between the communication master 15 and the terminal 13. That is, if the maximum amplitude Mout-max of the mixer output Mout (frequency difference) is obtained, the distance d1 between the communication master 15 and the target can be specified. Therefore, the radar apparatus 2 (inverse discrete Fourier transform unit 51) calculates the distance d1 based on the mixer output Mout.

[Transponder mode]
As shown in FIG. 13, when it is time to measure the distance d <b> 2 with the terminal 13, the CPU 3 outputs a first frequency signal D <b> 1 having a frequency “f1” and a phase “φ1” from the first synthesizer 4. Let The first frequency signal D1 is output to the circulator 6 and the mixer 53. The first frequency signal D1 output from the first synthesizer 4 at this time is the same as the first frequency signal D1 in the radar mode for convenience, but it is changed to a signal having another frequency and phase. May be. The transmitting / receiving antenna 7 transmits the first frequency signal D1 as the first ultra-wideband radio wave S1 having the frequency “f1” and the phase “φ1”.

  Further, the oscillator 52 outputs a frequency signal D <b> 2 ′ having a frequency “f2” to the mixer 53. The mixer 53 mixes the first frequency signal D1 input from the synthesizer 4 and the frequency signal D2 'input from the oscillator 52, thereby generating a signal that is the source of the second ultra-wideband radio wave S2. Then, the mixer 53 outputs this mixer output to the transmission antenna 27 through the band pass filter 54. Thereby, the transmitting antenna 27 transmits the second ultra wideband radio wave S2 having the frequency “f2” and the phase “φ3”.

  The first frequency signal D1 output from the synthesizer 4 and the second frequency signal D2 generated by passing through the band pass filter 54 are added by the adder 30 in the communication master 15, and the added signal is beaten. The signal is extracted as a beat signal Be (first beat signal Be1) through the extraction circuit 31. The first beat signal Be1 extracted from the beat extraction circuit 31 is output to the CPU 45 through the AD converter 46.

  The terminal 13 receives the first ultra wideband radio wave S1 transmitted from the transmission / reception antenna 7 and the second ultra wideband radio wave S2 transmitted from the transmission antenna 27 by the reception antenna 32. Since the terminal 13 receives the first ultra-wideband radio wave S1 and the second ultra-wideband radio wave S2 at the same time, the terminal 13 receives the beat signal Be (received beat) obtained by adding the first ultra-wideband radio wave S1 and the second ultra-wideband radio wave S2. The signal Be1 ′) is automatically generated. Then, the terminal 13 UHF transmits phase information Dφ based on the received beat signal Be1 ′ from the transmission antenna 39 to the communication master 15.

  The communication master 15 receives the phase information Dφ transmitted from the terminal 13 by UHF with the receiving antenna 40 already installed in the communication master 15. The phase information Dφ is input to the beat extraction circuit 42 via the amplifier 41, and the beat extraction circuit 42 extracts the beat signal Be (second beat signal Be2) from the phase information Dφ. The second beat signal Be2 is output to the CPU 45 through the AD converter 46. Then, the CPU 45 calculates a phase difference Δφ between the first beat signal Be1 generated on the communication master 15 side and the second beat signal Be2 acquired from the terminal 13, and from the phase difference Δφ, the communication master 15 and The distance d2 between the terminals 13 is calculated.

According to the configuration of the present embodiment, in addition to (1) to (7) and (9) described in the first embodiment, the following effects can be obtained.
(10) The distance measurement system 14 calculates the distance d2 to the terminal 13 using the radar device 2 that measures the distance d1 to the target by the fast chirp communication method. Therefore, the distance d2 between the communication master 15 and the terminal 13 can be measured through fast chirp communication having a simple configuration and strong noise resistance.

  (11) The radio wave transmission unit 18 generates the first frequency signal D1 based on the output from the synthesizer 4 capable of generating a plurality of frequencies, and transmits the first frequency signal D1 from the communication master 15 as the first ultra wideband radio wave S1. A signal (second frequency signal D2) is generated by synthesizing the outputs of the oscillator 52 and the synthesizer 4 capable of generating only different frequencies, and this is transmitted from the communication master 15 as the second ultra-wideband radio wave S2. In this case, since only one synthesizer 4 is required for the radio wave transmission unit 18 (communication master 15), it is further advantageous to correctly detect unauthorized communication with a simple configuration.

Note that the embodiment is not limited to the configuration described so far, and may be modified as follows.
In each embodiment, as shown in FIG. 14, the terminal 13 may have a structure without the amplitude modulator 36 and the low-frequency oscillator 37. In the case of this example, a pulse modulator 38 is provided, and it is preferable to apply ASK modulation instead of a non-modulated wave (CW) when assigning the ID (electronic key ID) of the terminal 13 during communication. In this case, it is advantageous to simplify the configuration (circuit configuration) of the terminal 13.

In each embodiment, the configuration with one synthesizer 4 may be adopted in the first embodiment.
In each embodiment, the radar apparatus 2 can be changed to an apparatus that uses a method other than stepped FM or fast chirp.

In each embodiment, the frequencies of the first ultra-wideband radio wave S1 and the second ultra-wideband radio wave S2 can be set to various values according to the radio law or specifications.
In each embodiment, the frequency at which the terminal 13 transmits radio waves to the communication master 15 is not limited to the UHF band, and may be changed to another frequency. That is, the “different frequency” may be a frequency different from the frequency at which the communication master 15 transmits radio waves.

  In each embodiment, the configurations of the radio wave transmission unit 18, the first signal generation unit 19, the second signal generation unit 20, the information notification unit 21, and the distance measurement unit 22 can be appropriately adopted configurations other than those described in the embodiment. .

In each embodiment, the beat signal information Sbe may be information that can be used to derive the second beat signal Be.
In each embodiment, the distance measurement system 14 is not limited to the configuration using the existing radar device 2, and a dedicated transmitter may be newly provided in the communication master 15 to measure the distance d <b> 2 using this. .

In each embodiment, the terminal 13 is not limited to the electronic key, and various terminals such as a high-function mobile phone may be applied.
-In each embodiment, the communication master 15 can employ | adopt various apparatuses and apparatus.

Next, technical ideas that can be grasped from the above-described embodiment and other examples will be described below together with their effects.
(A) In the distance measuring system, the radar device transmits a transmission radio wave from the communication master while changing the frequency stepwise, receives a reflected radio wave reflected by the target, and widens the frequency of the reflected radio wave. The distance between the communication master and the terminal is measured by a stepped FM communication method that sweeps and collects the phase difference between the transmitted radio wave and the reflected radio wave for each frequency. According to this configuration, it is possible to measure the distance to the target through stepped FM communication with high noise resistance.

  (B) In the distance measurement system, the radar device transmits a transmission radio wave from the master while continuously changing the frequency, receives a reflected radio wave reflected by the target, and transmits the signal of the transmission radio wave and the reflected radio wave. The distance between the communication master and the terminal is measured based on the amplitude of the mixer output by a fast chirp communication method in which the mixer output is obtained by mixing with the above signal. According to this configuration, it is possible to measure the distance to the target through fast chirp communication with high noise resistance.

  DESCRIPTION OF SYMBOLS 1 ... Vehicle which is an example of a communication master, 2 ... Radar apparatus, 4 ... Synthesizer (1st synthesizer), 13 ... Terminal, 14 ... Distance measuring system, 15 ... Communication master, 18 ... Radio wave transmission part, 19 ... 1st signal Generation unit, 20 ... second signal generation unit, 21 (21a, 21b) ... information notification unit, 22 ... distance measurement unit, 23 ... communication correctness determination unit, 31, 33,42 ... beat extraction circuit, 37 ... low frequency oscillator 52 ... Oscillator, S1 ... Radio wave transmitted from the communication master (first ultra wideband radio wave), S2 ... Radio wave transmitted from the communication master (second ultra wideband radio wave), Be ... Beat signal, Be1 ... First beat signal , Be2 ... second beat signal, Dφ ... phase information, Be1 '... received beat signal, λ ... beat signal wavelength, d ... distance to target, d2 ... distance to terminal, S1' ... reflected radio wave, Δφ ... phase , Frequency of fLo ... low-frequency oscillator.

Claims (11)

A radio wave transmitter that transmits radio waves of different frequencies within the ultra-wideband radio wave band from the communication master;
A first signal generation unit that generates a beat signal based on the plurality of radio waves in the communication master;
A second signal generator that receives a plurality of the radio waves transmitted from the communication master at a terminal and generates a beat signal at the terminal;
An information notification unit for transmitting beat signal information related to the beat signal generated by the second signal generation unit from the terminal to the communication master at a different frequency;
A distance measuring unit configured to measure a distance between the communication master and the terminal based on the beat signal generated by the first signal generating unit and the beat signal information acquired from the terminal; Distance measuring system. The distance measurement system according to claim 1, wherein the beat signal information is phase information related to a beat signal or the beat signal itself. The radio wave transmission unit can transmit a plurality of the radio waves transmitted from the communication master by changing a combination of frequencies,
The distance measuring unit obtains the distance of the terminal calculated using the wavelength of the beat signal obtained when the radio wave is the first combination as a measurement range, and the beat signal obtained when the second combination is different from the first combination. The distance measurement system according to claim 1 or 2, wherein a distance between the terminal and the distance calculated by using the wavelength of the terminal as a measurement range is determined, and a distance between the communication master and the terminal is specified from a least common multiple of the distances. The distance measurement system according to any one of claims 1 to 3, wherein the first signal generation unit, the second signal generation unit, and the information notification unit each include a beat extraction circuit having a detector. The communication master includes a radar device that reflects a transmitted radio wave to a target to receive a reflected radio wave and can measure a distance from the target based on the reflected radio wave,
The distance measurement system according to any one of claims 1 to 4, wherein the radio wave transmission unit transmits at least one of the radio waves using the radar device when transmitting a plurality of radio waves having different frequencies. The distance measurement according to claim 5, wherein the radar apparatus measures a distance between the communication master and the terminal by a stepped FM communication method that measures a distance based on a phase difference between the transmitted and received beat signals. system. 6. The distance measuring system according to claim 5, wherein the radar apparatus measures a distance between the communication master and the terminal by a fast chirp communication method that measures a distance based on a frequency difference between the transmitted and received beat signals. . The terminal includes a low frequency oscillator capable of outputting a signal having a frequency lower than the frequency of the beat signal,
The information notification unit, when transmitting the beat signal information to the communication master, by using a hardware that is already installed in the terminal by enabling transmission of a signal modulated by the frequency of the low-frequency oscillator. The distance measuring system according to any one of 1 to 7. The radio wave transmission unit generates a frequency signal based on an output from a synthesizer capable of generating a plurality of frequencies, and transmits the signal as a first ultra wideband radio wave from the communication master, and can generate only one type of frequency. The distance measurement system according to any one of claims 1 to 8, wherein a signal is generated by synthesizing outputs of an oscillator and the synthesizer, and the signal is transmitted from the communication master as a second ultra-wideband radio wave. Based on the distance calculated by the distance measuring unit, it determines whether the established communication is correct or not. If the distance is less than a specified value, it is determined that the communication is normal. 10. The distance measurement system according to claim 1, further comprising a communication correctness determination unit that processes that communication is illegal. A radio wave transmission step for transmitting radio waves of a plurality of different frequencies within the ultra-wideband radio wave band from the communication master;
A first signal generation step of generating a beat signal based on the plurality of radio waves in the communication master;
A second signal generation step of receiving at the terminal a plurality of the radio waves transmitted from the communication master and generating a beat signal at the terminal;
An information notification step of transmitting beat signal information related to the beat signal generated in the second signal generation step from the terminal to the communication master at a different frequency;
A distance measuring step of measuring a distance between the communication master and the terminal based on the beat signal generated in the first signal generating step and the beat signal information acquired from the terminal; Distance measuring method.

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