JP2006217399A - Receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a receiver capable of suppressing multipath distortion and improving reception quality. <P>SOLUTION: The receiver comprises a plurality of antennas; a plurality of synthesizers which generate weighting factors for controlling the amplitude and phase of baseband signals by the number of the baseband signals, by using different band components respectively out of individual baseband signals obtained via the plurality of antennas, multiply individual baseband signals, and individual weighting factors respectively and then add these; a plurality of demodulator circuits which generate amplitude and phase data by respectively applying fast Fourier transformation to synthetic signals output from individual synthesizers, and performing demodulation processing based on orthogonal frequency division multiplexing for each subcarrier; and a carrier synthesizer for composing data output from individual demodulator circuits for each subcarrier. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a receiving apparatus.

  In recent years, a multi-carrier modulation system called an OFDM (Orthogonal Frequency Division Multiplexing) system has been developed as a system for transmitting digital signals.

  The OFDM scheme generates a large number of subcarriers (carriers) that are orthogonal to each other (that is, has a property of not interfering), and divides the transmission signal and assigns it to each subcarrier. This is a method of multiplexing and transmitting after performing modulation processing to change the amplitude and phase of the subcarrier.

  The plurality of symbol signals obtained by dividing the transmission signal is slower than the original transmission signal. For this reason, if the OFDM method is adopted as the transmission method, the original signal is reflected on a building or the like and arrives through a plurality of paths, thereby reducing multipath distortion that causes deterioration in reception quality.

  By the way, in terrestrial digital broadcasting, it is desired to receive high-definition broadcasting for fixed reception at home or the like with a mobile body such as an automobile. As described above, when terrestrial digital broadcasting is received while moving by a moving body such as an automobile, multipath distortion occurs, which significantly deteriorates reception quality.

  Therefore, the terrestrial digital broadcast mobile communication employs the OFDM method as a transmission method in order to reduce multipath distortion.

  Further, mobile reception of terrestrial digital broadcasting employs a diversity reception system as a technique for improving reception quality. In the diversity reception method, an operation for controlling the directivity of the antenna is performed by arranging a plurality of antennas at different positions of the moving body and executing signal processing for combining a plurality of reception signals received by the respective antennas. Realized by signal processing.

  Here, a receiving apparatus that performs diversity reception in the OFDM scheme will be described. In this receiving apparatus, a plurality of antennas are arranged at different positions on the moving body, and a plurality of received signals received by these antennas are divided into three bands, respectively.

  Then, the receiving device synthesizes the desired wave component in each band by synthesizing while controlling (changing) the amplitude and phase of each received signal according to the difference in amplitude and phase of each received signal for each divided band. Perform processing to enhance and improve reception quality.

  After synthesizing the received signal divided into three bands, the receiving apparatus performs FFT (Fast Fourier Transform) and performs demodulation processing for each subcarrier, thereby obtaining amplitude and phase data. Obtain a digital signal (see Non-Patent Document 1).

  However, even if the amplitude and phase are controlled within a wide band obtained by dividing the received signal into three bands as in such a receiving apparatus, if there are multipaths with a long delay time, the phases are matched. As a result, the multipath distortion cannot be reduced and the reception quality deteriorates.

The following is a list of literature names related to diversity reception.
IPSJ Research Report, 2003-ITS-15

  An object of the present invention is to provide a receiving apparatus capable of improving reception quality by suppressing multipath distortion.

According to the receiving device of one aspect of the present invention,
Multiple antennas,
Of the baseband signals obtained via the plurality of antennas, using different band components, the weighting coefficients for controlling the amplitude and phase of the baseband signal are generated by the number of the baseband signals. A plurality of combining units for multiplying each baseband signal and each weighting factor and adding them,
A plurality of amplitude and phase data are generated by performing fast Fourier transform on the combined signal output from each combining unit and performing demodulation processing based on the orthogonal frequency division multiplexing method for each subcarrier. A demodulation circuit;
And a carrier synthesis unit that synthesizes data output from each demodulation circuit for each subcarrier.

  According to the receiving apparatus of the present invention, multipath distortion can be suppressed and reception quality can be improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(1) First Embodiment FIG. 1 shows the configuration of a receiving apparatus 10 according to the first embodiment of the present invention. The receiving device 10 is mounted on a moving body such as an automobile, and a plurality of antennas 20A to 20D are arranged at different positions.

  For example, the receiving device 10 performs diversity reception by receiving broadcast waves, which are transmitted after being subjected to modulation processing based on the OFDM scheme at a broadcast station, by the plurality of antennas 20A to 20D, respectively.

  An RF (Radio Frequency) signal S10A received by the antenna 20A is input to the tuner 30A, and similarly, RF signals S10B to S10D received by the antennas 20B to 20D are input to the tuners 30B to 30D. .

  The tuner 30A converts the frequency of the RF signal S10A into an IF (Intermediate Frequency) signal S20A, and outputs this to the A / D converter 40A. Similarly, tuners 30B to 30D frequency-convert RF signals S10B to S10D into IF signals S20B to S20D and output the signals to A / D converters 40B to 40D.

  The A / D converter 40A converts the IF signal S20A from analog to digital, and outputs the digitized IF signal S30A to an IQ (In-phase / Quadrature-phase) demodulator 50A. Similarly, the A / D converters 40B to 40D convert the IF signals S20B to S20D from analog to digital, and output the digitized IF signals S30B to S30D to the IQ demodulators 50B to 50D.

  The IQ demodulator 50A generates a baseband signal S40A by orthogonally demodulating the digitized IF signal S30A, and outputs this to the synthesis circuits 60A to 60D. Similarly, the IQ demodulators 50B to 50D generate baseband signals S40B to S40D by orthogonal demodulation of the digitized IF signals S30B to S30D, and output them to the synthesis circuits 60B to 60D. The baseband signals S40A to S40D are complex signals each consisting of an I channel (real axis component) and a Q channel (imaginary axis component).

  The synthesis circuits 60A to 60D synthesize the baseband signals S40A to S40D so as to enhance the desired wave components in different bands.

  The synthesis circuit 60A inputs the baseband signals S40A to S40D to a BPF (bandpass filter) 70, further inputs the baseband signal S40A to the multiplier 80A, and inputs the baseband signal S40B to the multiplier 80B. Signal S40C is input to multiplier 80C, and baseband signal S40D is input to multiplier 80D.

  Further, the baseband signal S50A generated by combining the baseband signals S40A to S40D is given to the BPF 70 from the adder 90.

  The BPF 70 divides the baseband signals S40A to S40D having a bandwidth of about 6 MHz into four bands, and passes only the band allocated to the synthesis circuit 60A among the four divided bands. is there. That is, the BPF 70 passes only the frequency components of the band assigned to the synthesis circuit 60A among the baseband signals S40A to S40D and the baseband signal S50A given from the adder 90, thereby allowing the baseband signals S60A to S60A to pass. S60E is obtained, and these are output to the coefficient control circuit 100.

The coefficient control circuit 100 uses the baseband signal S60E given from the adder 90 via the BPF 70 as a reference, and the amplitude and phase of the baseband signals S60A to S60D given from the IQ demodulators 50A to 50D via the BPF 70. By detecting the shift, the baseband signals S60A to S60D are matched in phase, and weight coefficients S70A to S70D made up of complex numbers Ae ^jθ are generated so as to enhance the desired wave component, and these are applied to corresponding multipliers 80A to 80D. Respectively.

  Multiplier 80A multiplies baseband signal S40A and weighting coefficient S70A to adjust the amplitude and phase of baseband signal S40A, and outputs the obtained baseband signal S80A to adder 90. Similarly, the multipliers 80B to 80D multiply the baseband signals S40B to S40D and the weighting factors S70B to S70D to adjust the amplitude and phase of the baseband signals S40B to S40D, and obtain the obtained baseband signal S80B. To S80D are output to the adder 90.

  The adder 90 generates a baseband signal S50A by adding and synthesizing the baseband signals S80A to S80D, and outputs this to the BPF 70 and the FFT circuit 110A.

  In this way, the synthesis circuit 60A controls the amplitude and phase of each of the baseband signals S40A to S40D according to the amplitude and phase shift of the band allocated to the synthesis circuit 60A among the baseband signals S40A to S40D ( The baseband signal S50A in which the desired wave component in the band assigned to the synthesis circuit 60A is strengthened is synthesized by synthesizing them while adjusting).

  Similar to the synthesis circuit 60A, the synthesis circuits 60B to 60D each baseband signal S40A according to the amplitude and phase shift of the band assigned to each of the synthesis circuits 60B to 60D among the baseband signals S40A to S40D. By combining these while controlling (adjusting) the amplitude and phase of S40D, baseband signals S50B to S50D in which the desired wave components of the bands assigned to the respective synthesis circuits 60B to 60D are strengthened are generated, These are output to the corresponding FFT circuits 110B to 110D.

  The FFT circuit (OFDM demodulation circuit) 110A performs FFT to convert the baseband signal S50A from a time domain signal to a frequency domain signal, and performs demodulation processing based on the OFDM method for each subcarrier, thereby obtaining the amplitude and Phase data is obtained and output to the carrier synthesis circuit 120 as amplitude phase data S90A.

  Similar to the FFT circuit 110A, the FFT circuits 110B to 110D perform FFT to convert the baseband signals S50B to S50D from time domain signals to frequency domain signals, and perform demodulation processing based on the OFDM scheme for each subcarrier. As a result, amplitude and phase data are obtained and output to the carrier synthesizing circuit 120 as amplitude phase data S90B to S90D.

  The carrier synthesizing circuit 120 generates amplitude phase data S100 in which the desired wave component is strengthened by synthesizing each subcarrier while performing weighting according to the amplitude shift of the amplitude phase data S90A to S90D. This is output to the error correction circuit 130.

  The error correction circuit 130 performs data determination on the amplitude / phase data S100 to obtain a digital signal, performs predetermined error correction processing, and outputs the received data S110 obtained to a subsequent circuit (not shown).

  As described above, according to the present embodiment, it is possible to suppress multipath distortion for each of four bands before performing FFT, and to further suppress multipath distortion for each subcarrier after performing FFT. As a result, the reception quality can be improved.

(2) Second Embodiment FIG. 2 shows the configuration of a receiving apparatus 200 according to the second embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the same element as the element shown by FIG. 1, and description is abbreviate | omitted.

  In the case of this receiving device 200, the A / D converter 40A outputs the digitized IF signal S30A to the IQ demodulator 50A and also outputs it to the AGC (automatic gain control) circuit 210A. Similarly, the A / D converters 40B to 40D output the digitized IF signals S30B to S30D to the IQ demodulators 50B to 50D and also to the AGC circuits 210B to 210D.

  The AGC circuit 210A generates a gain control signal S200A based on the IF signal S30A, and outputs the gain control signal S200A to the tuner 30A, thereby controlling the signal level of the IF signal S20A output from the tuner 30A to a predetermined level. .

  Similarly, the AGC circuits 210B to 210D generate gain control signals S200B to S200D based on the IF signals S30B to S30D, and output them to the tuners 30B to 30D, whereby the IF signals output from the tuners 30B to 30D. Control is performed so that the signal level of S20B to S20D becomes a predetermined level.

  The reception apparatus 200 includes a reception level determination circuit 220 included in a reception quality determination unit that determines reception quality of each reception signal. The reception level determination circuit 220 includes gain control signals S200A to S200A to AGC circuits 210A to 210D. S200D is given. Reception level determination circuit 220 determines the reception level of each antenna 20A to 20D based on gain control signals S200A to S200D, and outputs the determination result to synthesis circuits 230A to 230D as reception level information S210.

  The synthesis circuit 230A inputs the reception level information S210 to the coefficient control circuit 240. The coefficient control circuit 240 uses the reception level information S210 to relatively increase the weight (that is, the amplitude A) of the baseband signals S40A to S40D obtained from the reception signal having a high reception level (high reception quality), Weight coefficients S70A to S70D are generated so as to relatively reduce the weights of the baseband signals S40A to S40D obtained from the reception signal having a low reception level (reception quality is low), and these are applied to the corresponding multipliers 80A to 80A. Output to 80D respectively.

  Similarly, the synthesis circuits 230B to 230D input the reception level information S210 to an internal coefficient control circuit (not shown), and perform the same processing as the coefficient control circuit 240 of the synthesis circuit 320A.

  As described above, according to the present embodiment, before performing FFT, according to the reception level of each antenna 20A to 20D, multipath distortion is suppressed for each of the four bands, and after performing FFT, Multipath distortion can be suppressed finely every time, and thereby the reception quality can be improved.

(3) Third Embodiment FIG. 3 shows the configuration of a receiving apparatus 300 according to the third embodiment of the present invention. The same elements as those shown in FIG. 2 are denoted by the same reference numerals and description thereof is omitted.

  The receiving apparatus 300 includes a guard correlation determination circuit 310 included in a reception quality determination unit that determines the reception quality of each reception signal. The guard correlation determination circuit 310 includes baseband signals S40A from IQ demodulation circuits 50A to 50D. ~ S40D is given.

  By the way, in the OFDM system, in order to reduce the influence of multipath, a signal period called a guard period in which a rear part of the transmission symbol is copied is added to the head of each transmission symbol. The correlation level during the guard period corresponds to the reception level of the antenna. When the correlation level during the guard period is high, the reception level is high, and when the correlation level is low, the reception level is low.

  The guard correlation determination circuit 310 determines the correlation level of the guard period in each of the baseband signals S40A to S40D obtained from the antennas 20A to 20D, and outputs the determination result to the synthesis circuits 320A to 320D as correlation level information S310. .

  The synthesis circuit 320A inputs the correlation level information S310 to the coefficient control circuit 330. The coefficient control circuit 330 uses the correlation level information S310 to weight the baseband signals S40A to S40D (that is, the amplitude A) obtained from the reception signal having a low correlation level (reception quality is low). Coefficients S70A to S70D are generated and output to corresponding multipliers 80A to 80D, respectively.

  Similarly, the synthesis circuits 320B to 320D input the correlation level information S310 to an internal coefficient control circuit (not shown), and perform the same processing as the coefficient control circuit 330 of the synthesis circuit 320A.

  As described above, according to the present embodiment, before performing FFT, multipath distortion is suppressed for each of the four bands according to the correlation levels of the baseband signals S40A to S40D obtained from the antennas 20A to 20D. Further, after further performing FFT, multipath distortion can be finely suppressed for each subcarrier, thereby improving the reception quality.

(4) Fourth Embodiment FIG. 4 shows the configuration of a receiving apparatus 400 according to the fourth embodiment of the present invention. The same elements as those shown in FIG. 2 are denoted by the same reference numerals and description thereof is omitted.

  The receiving apparatus 400 includes an S / N (signal-to-noise ratio) determination circuit 410 included in a reception quality determination unit that determines the reception quality of each received signal. The S / N determination circuit 410 includes an IQ demodulation circuit. Baseband signals S40A to S40D are provided from 50A to 50D.

  The S / N determination circuit 410 determines S / N by demodulating some of the baseband signals S40A to S40D obtained from the antennas 20A to 20D, and determines the determination result as S / N. The information S410 is output to the synthesis circuits 420A to 420D.

  In addition, as a signal used for S / N determination, additional information such as AC (Auxiliary Channel), TMCC (Transmission and Multiplexing Configuration Control) subjected to BPSK modulation (Binary Phase Shift Keying), for example, is used. There is a signal to transmit.

  The combining circuit 420A inputs the S / N information S410 to the coefficient control circuit 430. The coefficient control circuit 430 uses the S / N information S410 so that the weight (that is, the amplitude A) of the baseband signals S40A to S40D obtained from the received signal with a small S / N (reception quality is low) becomes small. , Weight coefficients S70A to S70D are generated and output to the corresponding multipliers 80A to 80D, respectively.

  Similarly, the synthesis circuits 420B to 420D input S / N information S410 to an internal coefficient control circuit (not shown), and perform the same processing as the coefficient control circuit 430 of the synthesis circuit 420A.

  As described above, according to the present embodiment, before performing FFT, multipath distortion is suppressed for each of the four bands according to the S / N of the baseband signals S40A to S40D obtained from the antennas 20A to 20D. In addition, after performing FFT, multipath distortion can be finely suppressed for each subcarrier, thereby improving reception quality.

(5) Fifth Embodiment FIG. 5 shows the configuration of a receiving apparatus 500 according to the fifth embodiment of the present invention. The same elements as those shown in FIG. 2 are denoted by the same reference numerals and description thereof is omitted.

  The receiving apparatus 500 includes an analog interference determination circuit 510 included in a reception quality determination unit that determines the reception quality of each received signal. The analog interference determination circuit 510 includes baseband signals S40A from IQ demodulation circuits 50A to 50D. ~ S40D is given.

  The analog interference determination circuit 510 analyzes, for example, a frequency component corresponding to the carrier frequency of a broadcast wave by analog television broadcasting from among the baseband signals S40A to S40D obtained from the antennas 20A to 20D, thereby preventing analog interference. The level is determined, and the determination result is output to the combining circuits 520A to 520D as analog interference information S510.

  The synthesis circuit 520A inputs the analog interference information S510 to the coefficient control circuit 530. The coefficient control circuit 530 uses the analog interference information S510 so that the weight (that is, the amplitude A) of the baseband signals S40A to S40D obtained from the reception signal having a high analog interference level (reception quality is low) is reduced. Weight coefficients S70A to S70D are generated and output to corresponding multipliers 80A to 80D, respectively.

  Similarly, the synthesis circuits 520B to 520D input the analog interference level S510 to an internal coefficient control circuit (not shown), and perform the same processing as the coefficient control circuit 530 of the synthesis circuit 520A.

  As described above, according to the present embodiment, before performing FFT, multipath distortion is suppressed for each of the four bands according to the analog interference level of the baseband signals S40A to S40D obtained from the antennas 20A to 20D. In addition, after performing FFT, multipath distortion can be finely suppressed for each subcarrier, thereby improving reception quality.

  The above-described embodiment is an example and does not limit the present invention. For example, two synthesis circuits and two FFT circuits may be provided for four antennas. In short, a plurality of antennas are arranged, and a plurality of synthesis circuits are provided regardless of the number of antennas. It is sufficient to provide the same number of FFT circuits as the circuits.

It is a block diagram which shows the structure of the receiver by the 1st Embodiment of this invention. It is a block diagram which shows the structure of the receiver by the 2nd Embodiment of this invention. It is a block diagram which shows the structure of the receiver by the 3rd Embodiment of this invention. It is a block diagram which shows the structure of the receiver by the 4th Embodiment of this invention. It is a block diagram which shows the structure of the receiver by the 5th Embodiment of this invention.

Explanation of symbols

10, 200, 300, 400, 500 Receiver 20 Antenna 30 Tuner 40 A / D converter 50 IQ demodulator 60, 230, 320, 420, 520 Synthesis circuit 70 BPF
80 multiplier 90 adder 100, 240, 330, 430, 530 coefficient control circuit 110 FFT circuit 120 carrier synthesis circuit 210 AGC circuit 220 reception level determination circuit 310 guard correlation determination circuit 410 S / N determination circuit 510 analog interference determination circuit

Claims (5)

Multiple antennas,
Of the baseband signals obtained via the plurality of antennas, different band components are used to generate weighting coefficients for controlling the amplitude and phase of the baseband signals by the number of baseband signals. A plurality of combining units for multiplying each baseband signal and each weighting factor and adding them,
A plurality of amplitude and phase data are generated by performing fast Fourier transform on the combined signal output from each combining unit and performing demodulation processing based on the orthogonal frequency division multiplexing method for each subcarrier. A demodulation circuit;
A receiving apparatus comprising: a carrier synthesizing unit that synthesizes data output from each demodulation circuit for each subcarrier. A reception quality determination unit that determines reception quality of each reception signal received by the plurality of antennas;
The combining unit, based on the determination result of the reception quality determination unit, calculates the weighting factor for multiplying the baseband signal obtained from the reception signal having the first reception quality from the first reception quality. The receiving apparatus according to claim 1, wherein the weighting coefficient is set to be relatively larger than the weighting factor by which the baseband signal obtained from the received signal having a low second reception quality is multiplied. A plurality of gain control units for outputting a gain control signal for controlling the gain so that a signal output from the tuner connected to the antenna has a predetermined level, to the tuner and the reception quality determination unit;
The receiving apparatus according to claim 2, wherein the reception quality determination unit determines a reception level of each antenna based on each gain control signal given from the plurality of gain control units.   The reception apparatus according to claim 2, wherein the reception quality determination unit determines a correlation level of a guard period in each of the baseband signals obtained via the plurality of antennas.   The reception quality determination unit determines a signal-to-noise ratio by demodulating a part of each of the baseband signals obtained via the plurality of antennas. 2. The receiving device according to 2.

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