KR20080000337A - Apparatus for receiving broadcasting signal and method thereof - Google Patents

Abstract

An apparatus and a method for receiving a broadcasting signal are provided to reduce the amount of power consumed through a sampling procedure of the received signal. An apparatus for receiving a broadcasting signal includes a tuner(110), an oscillating part(135), and an analog-digital converter(130). The tuner(110) converts a received broadcasting signal into a signal having an intermediate frequency. The oscillation part(135) outputs a signal oscillating to the second harmonics. The analog-digital converter(130) converts a signal having the intermediate frequency output by the tuner(110) into a digital signal by using the oscillating signal. The intermediate frequency is in the range of 36MHz and 36.175MHz. The received signal is transmitted at the symbol rate of 7.56MHz. The oscillation part(135) outputs an oscillating signal oscillating in the range of 20MHz to 21.25MHz.

Description

Apparatus for receiving broadcasting signal and method

1 is a block diagram illustrating an example of a broadcast signal transmission apparatus capable of transmitting a broadcast signal of a DMB-T method in order to easily explain the present invention.

2 is a diagram illustrating a structure of a frame having a guard interval of 1/9 among frames of a broadcast signal of a DMB-T method;

3 is a view showing an embodiment of a broadcast signal receiving apparatus according to the present invention

4A and 4B show a spectrum of a signal input to an A / D converter and an output spectrum of a signal output from the A / D converter 130, respectively.

5 is a diagram illustrating an embodiment of an A / D converter of a broadcast signal receiving apparatus according to the present invention.

6A and 6B are diagrams illustrating spectra input and output to an A / D converter when sampling a received signal at a frequency of second harmonics using a DMB-T broadcast signal receiving apparatus according to the present invention.

<Description of the code of the main part of drawing>

10: channel encoding unit 15: TPS generation unit

20 modulator 30 reverse DFT

40: PN generator 50: multiplexer

60: filter unit 70: RF transmission unit

110: tuner 120: automatic gain controller (AGC)

130: analog to digital converter

135: oscillation unit 140: phase splitter

145: multiplier 160: filter unit

171: PN Correlator

172: Acquisition unit

174: signal tracking unit

177: automatic frequency control unit

180, 182: DFT section 190: equalizer

The present invention relates to a broadcast signal receiving apparatus and a broadcast signal receiving method, and more particularly, to a broadcast signal receiving apparatus and a broadcast signal receiving method capable of reducing power consumption.

New standards are being drafted for terrestrial digital television (“Terrestrial DTV”) broadcasting to China. The proposed standard is related to a broadcasting standard called Terrestrial Digital Multimedia / Television Broadcasting (DMB-T). In DMB-T, a new signal modulation scheme called Time Domain Synchronous OFDM (hereinafter referred to as TDS-OFDM) is used.

A signal transmitted after being modulated at the transmitting end of the TDS-OFDM is applied with an Inverse Discrete Fourier Transform (IDFT) as in the cyclic prefix OFDM (CP-OFDM) scheme.

However, the transmitted signal is used as a training signal by inserting a pseudonoise (PN) in place of the CP in the guard interval.

The above-described method can reduce overhead when transmitting a broadcast signal, improve channel usage efficiency, and improve performance of a synchronizer and a channel estimator of a broadcast signal receiver.

1 is a block diagram illustrating an example of a broadcast signal transmission apparatus capable of transmitting a DMB-T type broadcast signal in order to easily explain the present invention. An operation of an example of a broadcast signal transmission apparatus will be described with reference to FIG. 1.

The channel encoder 10 outputs a bitstream encoded by the channel in order to detect an error at the receiving end.

The TPS generation unit 15 includes a TPS (transmission variable parameter signal) including channel encoding or modulation information such as a frame group number, a forward error correction (FEC) code error ratio, and a time-deinterleaver mode. TPS) generates and outputs the data.

The modulator 20 receives the encoded bit stream and modulates the bit stream by quadrature amplitude modulation (QAM), such as 4-, 16-, or 64-values.

The inverse DFT unit 30 modulates a signal modulated by the OFDM scheme in the frequency domain into an OFDM signal in the time domain. In the DMB-T method, the inverse DFT unit 30 may simultaneously convert a frequency domain signal for 3780 points of transmission data into a time domain signal.

The PN generator 40 generates a PN sequence to be used as a training signal of a broadcast signal to be transmitted.

The multiplexer 50 distributes the generated PN sequence and the OFDM signal converted by the inverse DFT unit 30 in a time domain, and multiplexes the same.

The filter unit 60 outputs the bandwidth of the multiplexed DMB-T signal by limiting the bandwidth. A SRRC (Square Root Rasied Cosine) filter may be used as the filter of the filter unit. In general, a roll-off factor (α) used for the bandwidth limit is 0.05.

The RF transmitter 70 up-converts the output signal with the limited bandwidth to an RF (Radio Frequency) transmission band of a predetermined frequency fc to transmit a broadcast signal.

2 shows a structure of a frame having a guard interval of 1/9 of a frame of a DMB-T broadcast signal. A transmission frame structure having a guard interval of 1/9 will be described with reference to FIG. 2.

The frame includes frame sync and frame body. The frame body is a place where data to be transmitted is a DFT block to which a Discrete Fourier Transform (DFT) is applied, and the DFT block generally includes 3780 stream data.

The frame sync consists of a PN sequence, and the PN sequence used for the frame sync may use a sequence having an order of 8 (m = 8). When m = 8, 255 different sequences can be generated. The sequences are extended to preambles and postambles for use in guard intervals.

The preamble and the postamble are repetition intervals of the PN sequence for cyclic extension of the PN sequence.

Of the 255 PN sequences of the frame sync, the first 115 PNs of the PN sequence are added as a postamble to the end of the 255 PN sequence, and the last 50 PNs of the PN sequence are added as preambles before the 255 PN sequence. To expand.

The polynomial of the PN sequence is P (x) = x ⁸ + x ⁶ + x ⁵ + x + 1, and the generated phase may vary from 0 to 254 according to the initial state of the PN sequence.

If the guard interval is 1/9, the preamble and the postamble are added to the 255 PN sequences before and after, and the section to which the added PN sequence belongs is a frame sink including 420 data. In other words, 420 data, which is 1/9 of 3780 data of the DFT block, may be used for frame sync. One OFDM frame includes a frame sink of 420 data and a frame body of 3780 data.

The structure of the data frame may vary depending on the protection period, and the number of data distributed in each frame may also be distributed differently.

In addition, the guard interval may be defined as 1/4 or 1/9, in addition to that 1/6 guard interval may be used, and thus, the length of the guard interval may be formed differently depending on the method of forming the system.

The apparatus for receiving a broadcast signal as shown in FIG. 2 processes a digital signal obtained by sampling an analog signal into a digital signal. To this end, the broadcast signal receiving apparatus includes an analog-to-digital converter (hereinafter referred to as A / D) and can reduce sampling error according to a sampling rate through symbol timing recovery.

The above-mentioned terrestrial digital broadcasting is transmitted for the purpose of mobile reception, and there is a problem in that power consumption is high in converting and processing analog into a digital signal.

The present invention has been made to solve the above problems, and an object of the present invention relates to a broadcast signal receiving apparatus and a broadcast signal receiving method capable of reducing power consumption from a sampling process of a received signal.

In order to achieve the above object, the present invention provides a tuner for converting a received broadcast signal into an intermediate frequency band; An oscillator for outputting a signal oscillating at second harmonics of a sampleable frequency of the signal output from the tuner; And an analog-to-digital converter for converting a signal of the intermediate frequency band output by the tuner into a digital signal by using the oscillation signal output from the oscillator.

The intermediate frequency is 36MHz or more, preferably in the frequency range of 36.175MHz or less.

The received signal may be transmitted at a symbol rate of 7.56 MHz.

The oscillation unit preferably outputs an oscillation signal oscillating at a frequency in the range of 20 MHz or more and 21.25 MHz or less.

The present invention also provides a tuner for receiving a Terrestrial Digital Multimedia / Television Broadcasting (DMB-T) broadcast signal; An oscillator for oscillating a frequency of a second harmonic among sampleable frequencies of a signal output from the tuner; And an analog-to-digital converter for converting the signal output by the tuner into a digital signal using the oscillation signal output from the oscillator.

In another aspect, the present invention provides a method for processing a broadcast signal including receiving a broadcast signal; Converting the received signal into a signal of an intermediate frequency band; And sampling the received signal using an oscillation signal oscillating at a frequency of a second harmonic of a frequency at which sampling of the received signal is possible.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention that can specifically realize the above object will be described with reference to the accompanying drawings.

3 is a diagram illustrating an embodiment of a broadcast signal receiving apparatus according to the present invention. Referring to FIG. 3, an operation of an embodiment of a broadcast signal receiving apparatus according to the present invention will be described.

The tuner 110 of the broadcast signal receiving apparatus according to the present invention converts a signal of an RF transmission band into a base band signal and outputs it.

The automatic gain controller (AGC) 120 may output power by normalizing power of the output signal.

The analog to digital converter 130 converts the output signal into an analog signal and outputs the digital signal.

The phase splitter 140 divides an inphase component signal (hereinafter referred to as I signal) and a quadrature component signal (hereinafter referred to as Q signal) from the signal output from the A / D converter 130. Print separately.

The automatic frequency control (FCC) unit 177 compensates the estimated frequency error of the separated I and Q signals, and the filter unit 160 controls the bandwidth of the received signal as in the transmitter. Can act as a filter to limit

The frame synchronization unit may be divided into three parts. First, the AFC unit 177 calculates the frequency error of the received signal as described above, and calculates the product of the received signal and the signal from which the frequency error is calculated through the multiplier 145. It is possible to compensate for the frequency error of the received signal.

The signal acquisition unit 172 synchronizes the PN sequence sent by the transmitter. Finally, the signal tracking unit 174 compensates for the symbol error using the captured PN sequence.

The frame synchronizer of the received signal may use a result of correlation between the received signal and the PN sequence in the PN correlator 171.

Data output as a result of the frame synchronization unit is transformed into the frequency domain through the fast fourier transform (FFT) process in the DFT units 180 and 182, and the channel is compensated through the equalizer 190.

The broadcast signal receiving apparatus according to the present invention may reduce power consumption by minimizing the sampling clock of the A / D converter 130.

Hereinafter, a DMB-T broadcast signal receiving apparatus capable of receiving a broadcast signal according to DMB-T, which is a Chinese television standard, will be described.

4A and 4B are diagrams illustrating a spectrum of a signal input to an A / D converter and an output spectrum of a signal output from the A / D converter 130 according to the present invention.

The sampling frequency may be determined according to the algorithm of the receiving apparatus. In the case of the DMB-T signal receiving apparatus, symbol timing error recovery may operate at twice the symbol rate. Sampling at a frequency equal to three times the symbol rate of the received signal can be complex after sampling, so sampling at twice the minimum frequency is desirable.

Therefore, since the symbol rate of the broadcast signal of the DMB-T is 7.56 MHz, a sampling frequency of the A / D converter is sufficient to be larger than 7.56 MHz x 2 (= 15.12 MHz).

FIG. 4A illustrates a case in which a tuner outputs a received signal for frequency downconverting in a spectrum in which an intermediate frequency is 36 MHz and a bandwidth is 8 MHz. Considering the symbol rate, the frequencies that can be sampled at the frequencies of the first harmonics range from 30.4 MHz (fs) to 45.6 MHz (= 3/2 fs), where 30.4 MHz is 30.24 MHz (= 4 times the symbol rate). Sampling frequency more often than 7.56 MHz × 4).

Therefore, the signal having the spectrum of FIG. 4A can sample the sampling clock at 30.4 MHz, which is a frequency four times larger than the symbol rate (7.56 MHz) (30.24 MHz = 7.56 MHz × 4), and sampled at 30.4 MHz. The spectrum of the signal is shown in Figure 4b.

The spectrum of the signal output from the A / D converter may vary depending on the sampling clock of the A / D converter.

4B is a spectrum of the signal output from the A / D converter. Since the input signal is sampled at a frequency of 30.4 MHz, the center frequency of the output signal spectrum is 5.6 MHz, which is 36 MHz to 30.4 MHz (fs), and the lowest frequency is 32 MHz. -1.6 MHz, which is 30.4 (fs).

An embodiment of the broadcast signal receiving apparatus according to the present invention may reduce power consumption by converting a digital signal by sampling the second harmonic of a sampling frequency when receiving a DMB-T signal.

5 is a diagram illustrating an embodiment of an A / D converter of a broadcast signal receiving apparatus according to the present invention. The operation of the A / D converter included in the broadcast signal receiving apparatus according to the present invention will be described with reference to FIG. 5 as follows.

The oscillator 135 may output an oscillation signal oscillating at a predetermined frequency. The oscillator 135 may output an oscillation signal at a frequency of a second harmonic among the frequencies capable of sampling the received signal.

The analog-to-digital converter 130 may sample the received signal using the oscillation signal of the oscillator 135 oscillating at a frequency of the second high frequency.

FIG. 6A illustrates an example of a spectrum input to an A / D converter when a DMB-T received signal is sampled using a frequency of second harmonics.

The received signal of the A / D converter illustrated in FIG. 6A is a signal having a center frequency of 36 MHz and a bandwidth of 8 MHz. The frequency that can be sampled with the frequency of the second harmonic of the received signal is from 20.48 MHz (fs) to 40.96 MHz (2fs).

6B illustrates an example of a spectrum of an output signal of an A / D converter in which the signal of FIG. 6A is sampled at a second harmonic. Sampled at 20.48 MHz (fs), the center frequency of the spectrum is 4.96 MHz (= 40.96 MHz (2fs)-36 MHz) and the lowest frequency of the spectrum is 0.96 MHz. Thus, no aliasing occurs and the signal can be sampled.

In the description of the above embodiment, since the intermediate frequency converted by the tuner is 36 MHz, a case where 20.48 MHz is used as the second harmonic is taken as an example.

In DMB-T, the tuner can use 36.125 MHz or 36.175 MHz as its center frequency when converting the received signal to an intermediate frequency. Therefore, the second harmonic of the sampling frequency can be used from 20 MHz to 21.25 MHz.

By using the second harmonic instead of the first harmonic of the sampling frequency, a lower sampling clock can be used. In the above example, when sampling the DMB-T received signal with the first harmonic, sampling is performed at 30.4 MHz, but when sampling with the second harmonic, the sampling clock is lowered because the sampling is performed at 20.48 MHz. If the sampling clock is low, the power consumption of the components processing the digital signal region can be reduced.

Therefore, in the example of the broadcast signal receiving apparatus of the DMB-T method, the A / D converter 130, the phase separator 140, the multiplier 145, and the resampler 150, which process the digital signal in FIG. 3, have a digital signal region. In order to reduce power consumption.

It is easy for a person skilled in the art to change or modify the present invention from the present specification. Thus, although an embodiment of the present invention has been described above clearly, various modifications thereof should be made without departing from the spirit and the scope of the invention.

The effects of the apparatus for receiving broadcast signals and the method for receiving broadcast signals according to the present invention described above are as follows. According to the broadcast signal receiving apparatus and the broadcast signal receiving method according to the present invention, power consumption can be reduced from a sampling process of a received signal.

Claims (7)

A tuner for converting the received broadcast signal into an intermediate frequency band; An oscillator for outputting a signal oscillating at second harmonics of a sampleable frequency of the signal output from the tuner; And And an analog-to-digital converter for converting an intermediate frequency band signal output by the tuner into a digital signal using the oscillation signal output from the oscillator. The method of claim 1, The intermediate frequency is 36MHz or more, broadcast signal receiving apparatus, characterized in that included in the frequency range of 36.175MHz or less. The method of claim 1, And the received signal is transmitted at a symbol rate of 7.56 MHz. The method of claim 1, And an oscillator is configured to output an oscillation signal oscillating at a frequency in a range of 20 MHz or more and 21.25 MHz or less. A tuner for receiving a Terrestrial Digital Multimedia / Television Broadcasting (DMB-T) broadcast signal; An oscillator for oscillating a frequency of a second harmonic among sampleable frequencies of a signal output from the tuner; And And an analog-to-digital converter for converting the signal output by the tuner into a digital signal by using the oscillation signal output by the oscillator. The method of claim 5, And a frequency of the second harmonic is 20 MHz or more and included in a frequency of 21.25 MHz or less. Receiving a broadcast signal; Converting the received signal into a signal of an intermediate frequency band; And And sampling the received signal using an oscillating signal oscillating at a frequency of a second harmonic of a frequency at which sampling of the received signal is possible.

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