JP5068230B2 - OFDM digital signal equalization apparatus, equalization method, and relay apparatus - Google Patents

Description

  The present invention relates to an OFDM (Orthogonal Frequency Division Multiplexing) digital signal equalization apparatus, equalization method, and relay apparatus, and particularly occurs due to a frequency shift of a reference signal used for frequency conversion of transmission and reception. The present invention relates to a technique for correcting a phase change of a filter coefficient.

  As one of methods for transmitting digital signals, a method called OFDM is used. This OFDM scheme is a scheme in which a number of orthogonal subcarriers are provided in a transmission band, data is allocated to the amplitude and phase of each subcarrier, and digital modulation is performed by QAM (Quadrature Amplitude Modulation) or the like.

  The OFDM signal digitally modulated by such a method is digitally transmitted from the transmitting station. Then, the OFDM digital signal relay apparatus installed in the relay station receives the digitally transmitted OFDM signal, and the equalizer distorts the signal distorted by the influence of the transmission path between the transmission station and the relay station. Multipath is equalized to restore the original signal. Then, the OFDM digital signal relay device amplifies the equalized signal and retransmits it. Such equalization processing is performed by a FIR (Finite Impulse Response) filter circuit provided in the equalization apparatus, and the characteristics of the FIR filter circuit are determined by filter coefficients generated by the filter coefficient generation circuit.

  FIG. 6 is a block diagram showing a configuration of a filter coefficient generation circuit in a conventional equalization apparatus. The filter coefficient generation circuit 150 is a circuit that generates filter coefficients of the FIR filter circuit 14 that performs the above-described equalization processing. The filter coefficient generation circuit 150 includes an FFT (Fast Fourier Transform) calculation circuit 20, an SP (scattered pilot) extraction circuit 21, and a calculation. A circuit 22 and an IFFT (Inverse Fast Fourier Transform) arithmetic circuit 23 are provided.

  The received OFDM signal is frequency-converted and AD-converted based on a predetermined reference signal, is input to the orthogonal demodulation circuit 13 provided in the previous stage of the filter coefficient generation circuit 150, and is orthogonally demodulated by the orthogonal demodulation circuit 13. . When the signal demodulated by the orthogonal demodulation circuit 13 is input to the filter coefficient generation circuit 150, the FFT operation circuit 20 converts the orthogonally demodulated time domain signal into the frequency domain by FFT (Fast Fourier Transform). The signal is converted into a signal, and the SP extraction circuit 21 extracts the SP signal to generate a channel response H (n). The arithmetic circuit 22 calculates the reciprocal of the channel response H (n), and the IFFT arithmetic circuit 23 converts the frequency domain signal that is the reciprocal of the channel response H (n) into the time domain by IFFT (Inverse Fast Fourier Transform). To generate a filter coefficient W (k). The filter coefficient W (k) generated by the filter coefficient generation circuit 150 is output to the subsequent FIR filter circuit 14. Here, n indicates a carrier number, and k indicates a filter coefficient number (tap number).

  As described above, the OFDM signal that is equalized by the FIR filter circuit 14 is frequency-converted based on a predetermined reference signal before the filter coefficient generation circuit 150. Here, it is desirable that the reference signal used for converting the transmission / reception frequency has no frequency shift. A reference signal oscillation circuit (not shown) is adjusted by AFC (Automatic Frequency Control) so that there is no frequency shift between transmission and reception. However, in practice, there is a slight frequency shift between the two signals, and it is difficult to eliminate this frequency shift. When there is a frequency shift in the reference signal used for transmission / reception frequency conversion, the entire filter coefficient generated by the filter coefficient generation circuit 150 is rotated in phase, and the FIR filter circuit 14 performs equalization using the filter coefficient. Therefore, the frequency of the input signal and the output signal of the FIR filter circuit 14 is shifted, and a phase change occurs.

  In order to solve such a problem, an OFDM demodulator described in Patent Document 1 is known. This OFDM demodulator extracts an SP signal from an FFT-processed OFDM signal, detects a phase rotation component amount using the phase of the SP signal and a preset phase of the SP carrier, averages the phase rotation component amount, An averaged phase rotation component amount is removed from the FFTed OFDM signal. As a result, even if there is a frequency shift in the reference signal used for frequency conversion of transmission and reception, phase rotation caused by it can be removed, and the equalization characteristics can be improved.

JP 2006-148696 A

  However, in the above-described OFDM demodulator of Patent Document 1, since the amount of phase rotation component is averaged, when the frequency of the reference signal used for frequency conversion of transmission and reception varies, the variation is converted into the phase rotation component. It cannot be reflected in the average value of the amounts, and the phase rotation component amount cannot be completely removed from the OFDM signal. This cannot improve the equalization characteristics.

  Therefore, the present invention has been made to solve the above-described problems, and an object of the present invention is to provide a filter coefficient caused by a frequency deviation even when a frequency shift occurs in a reference signal used for frequency conversion of transmission and reception. An OFDM digital signal equalization apparatus, an equalization method, and a relay apparatus capable of correcting the phase change of the signal and capable of dealing with the frequency fluctuation of the reference signal used for frequency conversion of transmission and reception It is in.

In order to solve the above problem, an OFDM digital signal equalization apparatus according to claim 1 according to the present invention includes a first conversion circuit that performs frequency conversion and AD conversion of an OFDM signal based on a predetermined reference signal, and the converted OFDM signal. Using a quadrature demodulation circuit that performs quadrature demodulation of a signal, a filter coefficient generation circuit that generates a filter coefficient based on a signal that is quadrature demodulated by the quadrature demodulation circuit, and a filter coefficient generated by the filter coefficient generation circuit, An FIR filter circuit for equalizing a signal demodulated by the orthogonal demodulation circuit, an orthogonal modulation circuit for orthogonally modulating the signal equalized by the FIR filter circuit, and an OFDM signal orthogonally modulated by the orthogonal modulation circuit. An OFDM digital signal comprising a second conversion circuit that performs DA conversion and frequency conversion based on the predetermined reference signal In the conversion apparatus, the filter coefficient generation circuit performs FFT processing on the time domain signal orthogonally demodulated by the orthogonal demodulation circuit, and converts the FFT processing circuit into a carrier symbol that is a frequency domain signal, and the FFT An SP signal is extracted from the carrier symbol converted by the arithmetic circuit, a channel response is calculated based on the extracted SP signal, and a channel response frequency domain signal calculated by the SP extraction circuit is extracted. IFFT processing circuit that performs IFFT processing calculation and converts it to filter coefficients that are time domain signals, and the filter of the main wave among the filter coefficients of all filter coefficient numbers for the filter coefficients converted by the IFFT calculation circuit The phase rotation amount is calculated using the filter coefficient of the coefficient number, and the phase rotation amount And a filter coefficient correction circuit that corrects phase rotation in the filter coefficients of all filter coefficient numbers and generates new filter coefficients, and the FIR filter circuit is controlled by the filter coefficient correction circuit of the filter coefficient generation circuit. Equalization is performed using the generated new filter coefficient.

The OFDM digital signal equalization apparatus according to claim 2 of the present invention is the OFDM digital signal equalization apparatus according to claim 1, wherein the filter coefficient correction circuit includes all the filter coefficients converted by the IFFT operation circuit. Among the filter coefficients of the filter coefficient number, the data storage unit for storing the filter coefficient of the filter coefficient number of the main wave , and the filter coefficient stored in the data storage unit is complex-divided by the absolute value of the filter coefficient And an arithmetic unit that calculates a correction amount and corrects the filter coefficients of all the filter coefficient numbers based on the correction amount to generate new filter coefficients.

An OFDM digital signal equalization apparatus according to a third aspect of the present invention is the OFDM digital signal equalization apparatus according to the first aspect, wherein the filter coefficient correction circuit includes all the filter coefficients converted by the IFFT operation circuit. Among the filter coefficients of the filter coefficient number, the data storage unit for storing the filter coefficient of the filter coefficient number of the main wave , and the real axis value and the imaginary axis value in the complex plane of the filter coefficient stored in the data storage unit And an arithmetic unit that generates new filter coefficients by correcting the filter coefficients of all the filter coefficient numbers based on the angles.

According to a fourth aspect of the present invention, there is provided the OFDM digital signal equalization method according to the present invention, wherein the OFDM signal is frequency-converted and AD-converted based on a predetermined reference signal, the converted OFDM signal is orthogonally demodulated, and A filter coefficient is generated based on the signal, the orthogonal demodulated signal is equalized using the filter coefficient, the equalized signal is orthogonally modulated, the orthogonally modulated OFDM signal is DA-converted, and the predetermined reference signal In the OFDM digital signal equalization method for frequency conversion based on the above, a step of performing FFT processing on the orthogonally demodulated time domain signal and converting it to a carrier symbol which is a frequency domain signal, and from the converted carrier symbol Extracting an SP signal and calculating a channel response based on the extracted SP signal; A step of performing IFFT processing on the frequency domain signal of the channel response and converting it to a filter coefficient which is a time domain signal, and a main wave filter among the filter coefficients of all filter coefficient numbers in the converted filter coefficient Calculating a phase rotation amount using the filter coefficient of the coefficient number, and correcting a phase rotation in the filter coefficients of all the filter coefficient numbers based on the calculated phase rotation amount, and generating a new filter coefficient It is characterized by having.

According to the OFDM digital signal equalization method of claim 5 of the present invention, the OFDM signal is frequency-converted and AD-converted based on a predetermined reference signal, the converted OFDM signal is orthogonally demodulated, and the orthogonally demodulated signal is converted to the orthogonally demodulated signal. A filter coefficient is generated based on the signal, the orthogonal demodulated signal is equalized using the filter coefficient, the equalized signal is orthogonally modulated, the orthogonally modulated OFDM signal is DA-converted, and the predetermined reference signal In the OFDM digital signal equalization method for frequency conversion based on the above, a step of performing FFT processing on the orthogonally demodulated time domain signal and converting it to a carrier symbol which is a frequency domain signal, and from the converted carrier symbol Extracting an SP signal and calculating a channel response based on the extracted SP signal; Performs calculation of the IFFT processing on the frequency domain signal Yaneru response, and converting the filter coefficients are time-domain signals, among the filter coefficients of all the filter coefficients numbers in the transform filter coefficients, a main wave filter A step of storing a filter coefficient of a coefficient number; a step of complex-dividing the stored filter coefficient by an absolute value of the filter coefficient to obtain a correction amount; and a filter coefficient of all filter coefficient numbers based on the correction amount And a step of generating a new filter coefficient.

In the OFDM digital signal equalization method according to claim 6 of the present invention, the OFDM signal is frequency-converted and AD-converted based on a predetermined reference signal, the converted OFDM signal is orthogonally demodulated, and the orthogonally demodulated signal is converted to the orthogonally demodulated signal. A filter coefficient is generated based on the signal, the orthogonal demodulated signal is equalized using the filter coefficient, the equalized signal is orthogonally modulated, the orthogonally modulated OFDM signal is DA-converted, and the predetermined reference signal In the OFDM digital signal equalization method for frequency conversion based on the above, a step of performing FFT processing on the orthogonally demodulated time domain signal and converting it to a carrier symbol which is a frequency domain signal, and from the converted carrier symbol Extracting an SP signal and calculating a channel response based on the extracted SP signal; Performs calculation of the IFFT processing on the frequency domain signal Yaneru response, and converting the filter coefficients are time-domain signals, among the filter coefficients of all the filter coefficients numbers in the transform filter coefficients, a main wave filter Storing filter coefficients of coefficient numbers; calculating angles from real and imaginary axis values in the complex plane of the stored filter coefficients; and filter coefficients of all filter coefficient numbers based on the angles And a step of generating a new filter coefficient.

An OFDM digital signal relay apparatus according to a seventh aspect of the present invention uses the OFDM digital signal equalization apparatus according to any one of the first to third aspects.

  As described above, according to the present invention, the phase change of the filter coefficient is obtained using the filter coefficient of the predetermined filter coefficient number, and the new filter coefficient is generated by correcting the phase change. Thereby, even if a frequency shift occurs in the reference signal used for frequency conversion of transmission and reception, it is possible to correct the phase change of the filter coefficient caused by the frequency shift. In addition, since the phase change of the filter coefficient is obtained directly from the filter coefficient of the predetermined filter coefficient number without performing the averaging process, the frequency of the reference signal used for frequency conversion of transmission / reception varies. However, the phase change corresponding to the fluctuation can be obtained, and the phase change can be corrected.

The best mode for carrying out the present invention will be described below in detail with reference to the drawings.
[Equalizer]
First, the equalizer is described. FIG. 1 is a block diagram showing a configuration of an equalization apparatus according to an embodiment of the present invention. The equalization apparatus 1 includes a reference signal oscillation circuit 10, a frequency conversion circuit 11, an AD conversion circuit 12, an orthogonal demodulation circuit 13, an FIR filter circuit 14, a filter coefficient generation circuit 15, an orthogonal modulation circuit 16, a DA conversion circuit 17, and a frequency. A conversion circuit 18 is provided.

  The reference signal oscillation circuit 10 oscillates a reference signal for frequency conversion of the signal in the frequency conversion circuits 11 and 18 and outputs the reference signal to the frequency conversion circuits 11 and 18.

  The frequency conversion circuit 11 inputs the received OFDM signal, receives a reference signal from the reference signal oscillation circuit 10, performs frequency conversion of the OFDM signal based on the reference signal, and outputs an IF signal to the AD conversion circuit 12. The AD conversion circuit 12 receives the IF signal from the frequency conversion circuit 11, AD converts the analog IF signal into a digital IF signal, and outputs the digital IF signal to the quadrature demodulation circuit 13.

  The orthogonal demodulation circuit 13 receives the digital IF signal from the AD conversion circuit 12, performs orthogonal demodulation processing, converts it into a complex baseband signal, and outputs it to the FIR filter circuit 14 and the filter coefficient generation circuit 15.

  The filter coefficient generation circuit 15 receives the quadrature demodulated signal from the quadrature demodulation circuit 13, generates a filter coefficient W (k), corrects the phase, and converts the phase corrected filter coefficient W ′ (k) to the FIR filter circuit 14. Output to. If there is a frequency shift between transmission and reception in the reference signal used for frequency conversion in the frequency conversion circuit 11 (reference signal input from the reference signal oscillation circuit 10), the filter coefficient W (generated by the filter coefficient generation circuit 15) Phase rotation occurs in k). Since this phase rotation is the same for the filter coefficients W (k) of all filter coefficient numbers, the phase rotation amount is calculated by paying attention to the filter coefficient W (k) of any filter coefficient number. In Examples 1 and 2 described later, attention is focused on the filter coefficient W (k) of the filter coefficient number of the main wave. Then, a new filter coefficient W ′ (k) is generated by correcting this phase rotation. Details of processing for generating the filter coefficient W (k) and processing for generating a new filter coefficient W ′ (k) by correcting the phase of the filter coefficient W (k) will be described later.

  The FIR filter circuit 14 receives the signal demodulated from the quadrature demodulation circuit 13 and the filter coefficient W ′ (k) from the filter coefficient generation circuit 15 and inputs it using the filter coefficient W ′ (k). The signal is equalized and the equalized signal is output to the quadrature modulation circuit 16.

  The quadrature modulation circuit 16 receives a complex baseband signal that is equalized by the FIR filter circuit 14, performs quadrature modulation processing, converts the signal into a digital IF signal, and outputs the digital IF signal to the DA conversion circuit 17.

  The DA conversion circuit 17 receives the digital IF signal from the quadrature modulation circuit 16, DA converts the digital IF signal into an analog IF signal, and outputs the analog IF signal to the frequency conversion circuit 18. The frequency conversion circuit 18 inputs an analog IF signal from the DA conversion circuit 17 and also receives a reference signal from the reference signal oscillation circuit 10, converts the frequency of the analog IF signal based on the reference signal, and outputs an OFDM signal.

[Filter coefficient generation circuit]
Next, the filter coefficient generation circuit 15 shown in FIG. 1 will be described. FIG. 2 is a block diagram showing a configuration of the filter coefficient generation circuit 15. The filter coefficient generation circuit 15 includes an FFT operation circuit 20, an SP extraction circuit 21, an operation circuit 22, an IFFT operation circuit 23, and a filter coefficient correction circuit 24. The filter coefficient generation circuit 15 receives an orthogonally demodulated signal from the orthogonal demodulation circuit 13. The filter coefficient W (k) is generated, the filter coefficient W (k) is phase-corrected to generate a new filter coefficient W ′ (k), and the new filter coefficient W ′ (k) is generated as the FIR filter circuit 14. Output to.

  The FFT operation circuit 20 receives the orthogonal demodulated signal from the orthogonal demodulation circuit 13, performs FFT processing on the time domain signal, converts it to a carrier symbol which is a frequency domain signal, and converts the carrier symbol into an SP extraction circuit To 21.

  The SP extraction circuit 21 inputs a carrier symbol from the FFT operation circuit 20, extracts an SP signal from the input carrier symbol, divides the extracted SP signal by a transmission SP signal having a preset amplitude and phase, A channel response H (n) is calculated. Then, the channel response H (n) calculated for the SP signal is used for interpolation in the frequency direction and the symbol direction, and the channel responses H (n) of all carrier symbols are output to the arithmetic circuit 22.

  The arithmetic circuit 22 receives the channel response H (n) from the SP extraction circuit 21, calculates 1 / H (n), and outputs the inverse 1 / H (n) of the channel response to the IFFT arithmetic circuit 23. The IFFT arithmetic circuit 23 receives the inverse 1 / H (n) of the channel response from the arithmetic circuit 22, performs IFFT processing on the frequency domain signal, and converts it into a filter coefficient W (k) which is a time domain signal. The filter coefficient W (k) is output to the filter coefficient correction circuit 24. The filter coefficient W (k) output by the IFFT arithmetic circuit 23 is caused by a frequency shift between transmission and reception of a reference signal (reference signal input from the reference signal oscillation circuit 10) used for frequency conversion in the frequency conversion circuit 11. This is a coefficient that causes phase rotation.

  The filter coefficient correction circuit 24 receives the filter coefficient W (k) from the IFFT arithmetic circuit 23, calculates the phase rotation amount for the main-wave filter coefficient W (k) of the input filter coefficient W (k), Using this as a correction amount, the phase of all filter coefficients W (k) is corrected, and a new filter coefficient W ′ (k) is generated and output to the FIR filter circuit 14. Thereby, the FIR filter circuit 14 can perform equalization using the filter coefficient W ′ (k) whose phase rotation is corrected with reference to the main wave. That is, it is possible to cancel the phase rotation caused by the frequency shift of the reference signal used for frequency conversion of transmission / reception.

[Example 1]
Next, the filter coefficient correction circuit 24 shown in FIG. 2 will be described. First, the filter coefficient correction circuit 24-1 of the first embodiment will be described. FIG. 3 is a block diagram illustrating a configuration of the filter coefficient correction circuit 24-1 according to the first embodiment. The filter coefficient correction circuit 24-1 includes a data storage unit 30 and calculation units 31 and 32. The filter coefficient W (k, x) is input from the IFFT calculation circuit 23, and the filter coefficient W (M) of the main wave is input. , X) is used to calculate the phase rotation amount, all the filter coefficients W (k, x) are corrected using the phase rotation amount of the main wave as a correction amount, and a new filter coefficient W ′ (k, x) is calculated. Generate. Then, the generated filter coefficient W ′ (k, x) is output to the FIR filter circuit 14. Here, x indicates a symbol number, and M indicates a filter coefficient number of the main wave (the same applies to the second embodiment).

The data storage unit 30 stores the filter coefficient W (M, x) of the main wave among the filter coefficients W (k). The calculation unit 31 reads the main wave filter coefficient W (M, x) from the data storage unit 30, calculates the correction amount C by the following complex calculation formula, and outputs the correction amount C to the calculation unit 32.
C = W (M, x) / | W (M, x) |
Here, since the correction amount C is a value obtained by dividing the main wave filter coefficient by the absolute value of the main wave filter coefficient, the correction amount C indicates the phase when the amplitude of the main wave filter coefficient is 1. That is, the correction amount C represents the amount of phase rotation caused by the frequency shift of the reference signal used for frequency conversion of transmission and reception as the amount of phase rotation when the amplitude of the filter coefficient of the main wave is 1. Is.

The calculation unit 32 inputs the correction amount C from the calculation unit 31 and the filter coefficient W (k, x) from the IFFT calculation circuit 23, and the filter coefficients W (k, k) of all the filter coefficient numbers according to the following equations. , X) is phase-corrected to generate a new filter coefficient W ′ (k). The filter coefficient W ′ (k) generated in this way is output to the FIR filter circuit 14.
W ′ (k, x) = W (k, x) / C

  As described above, according to the equalizing apparatus 1 including the filter coefficient generation circuit 15 including the filter coefficient correction circuit 24-1 of the first embodiment, the amplitude is focused on the filter coefficient W (M, x) of the main wave. Is calculated as a correction amount C, the filter coefficients W (k, x) of all filter coefficient numbers are corrected, and a new filter coefficient W ′ (k, x) is calculated. Was generated. Then, the FIR filter circuit 14 performs equalization using the new filter coefficient W ′ (k) whose phase rotation is corrected. Thereby, even if a frequency shift occurs in the reference signal used for frequency conversion of transmission / reception, the phase change of the filter coefficient caused by the frequency shift can be corrected. In addition, since it is not necessary to perform the averaging process as in the prior art, even if the frequency of the reference signal used for frequency conversion of transmission and reception varies, the phase rotation corresponding to the variation is obtained and the phase rotation is corrected. be able to.

  Further, according to the equalizer 1, the phase rotation amount is calculated for the filter coefficient W (M, x) of the main wave, the phase correction is performed for all the filter coefficients W (k, x), and the new Filter coefficient W ′ (k, x) is generated. Since the filter coefficient W (M, x) of the main wave has a larger amplitude than the filter coefficient W (k, x) other than the main wave, the correction amount C with higher accuracy can be calculated. Therefore, a filter coefficient W (k, x) other than the main wave is generated by generating a new filter coefficient W ′ (k, x) based on the filter coefficient W (M, x) of the main wave and performing equalization. Equalization performance is better than generating new filter coefficients W ′ (k, x) based on the above and performing equalization.

[Example 2]
Next, the filter coefficient correction circuit 24-2 of the second embodiment will be described. FIG. 4 is a block diagram illustrating a configuration of the filter coefficient correction circuit 24-2 of the second embodiment. The filter coefficient correction circuit 24-2 includes a data storage unit 40 and calculation units 41 to 43. The filter coefficient W (k, x) is input from the IFFT calculation circuit 23, and the filter coefficient W (M) of the main wave is input. , X), the phase rotation amount is calculated from the real axis value and the imaginary axis value in the complex plane, and all the filter coefficients W (k, x) are corrected using the phase rotation amount of the main wave as a correction amount, A new filter coefficient W ′ (k, x) is generated. Then, the generated filter coefficient W ′ (k, x) is output to the FIR filter circuit 14.

The data storage unit 40 stores the filter coefficient W (M, x) of the main wave among the filter coefficients W (k). The calculation unit 41 reads the filter coefficient W (M, x) of the main wave from the data storage unit 40, and the real axis value Re [W (M, x)] of the filter coefficient W (M, x) in the complex plane and From the imaginary axis value Im [W (M, x)], the angle θ is obtained by the following equation, and the angle θ is output to the computing unit 42.

The calculation unit 42 receives the angle θ from the calculation unit 41, calculates cos θ and sin θ, and outputs them to the calculation unit 43. The calculation unit 43 inputs cos θ and sin θ from the calculation unit 42 and also inputs the filter coefficient W (k, x) from the IFFT calculation circuit 23, and the filter coefficients W of all filter coefficient numbers according to the following complex calculation expression. (K, x) is phase-corrected to generate a new filter coefficient W ′ (k). The filter coefficient W ′ (k) generated in this way is output to the FIR filter circuit 14.
W ′ (k, x) = W (k, x) e ^−jθ = W (k, x) · (cos θ−j sin θ)

  As described above, according to the equalizer 1 including the filter coefficient generation circuit 15 including the filter coefficient correction circuit 24-2 of the second embodiment, paying attention to the filter coefficient W (M, x) of the main wave, The phase rotation amount is calculated using the real axis value and the imaginary axis value of the filter coefficient of the main wave in the complex plane, correction is performed to restore the phase rotation, and a new filter coefficient W ′ (k, x) is generated. The FIR filter circuit 14 performs equalization using the new filter coefficient W ′ (k, x) whose phase rotation is corrected. Thereby, even if a frequency shift occurs in the reference signal used for frequency conversion of transmission / reception, the phase change of the filter coefficient caused by the frequency shift can be corrected. In addition, since it is not necessary to perform the averaging process as in the prior art, even if the frequency of the reference signal used for frequency conversion of transmission and reception varies, the phase rotation corresponding to the variation is obtained and the phase rotation is corrected. be able to.

  Further, according to the equalizer 1, the phase rotation amount is calculated for the filter coefficient W (M, x) of the main wave, the phase correction is performed for all the filter coefficients W (k, x), and the new Filter coefficient W (k, x) is generated. Accordingly, as in the first embodiment, compared to the case where a new filter coefficient W ′ (k, x) is generated based on the filter coefficient W (k, x) other than the main wave and equalization is performed, etc. Performance is improved.

[Repeater]
Next, a relay device using the equalization device 1 will be described. FIG. 5 is a block diagram illustrating a configuration of the relay apparatus. The relay device 2 includes a reception antenna 3, a frequency conversion unit 4, an equalization device 1 including any one of the filter coefficient correction circuits 24 of the first and second embodiments, a power amplification unit 5, and a transmission antenna 6.

The desired wave transmitted from the higher-level transmitting station is received by the receiving antenna 3 in the relay device 2 of the broadcast wave relay station. The frequency converter 4 receives a received signal from the receiving antenna 3 through the feeder line, removes an unnecessary signal component outside the frequency band of the desired wave, and amplifies the AGC (Automatic Gain Control) so that the output level becomes constant. Thereafter, the frequency is converted and an IF signal of the OFDM signal is output. The IF signal of the OFDM signal frequency-converted by the frequency converter 4 is output to the equalization apparatus 1.

  The equalization apparatus 1 receives the OFDM signal from the frequency conversion unit 4, performs frequency conversion, AD conversion, orthogonal demodulation, equalization, orthogonal modulation, DA conversion, and frequency conversion, and converts the IF signal of the OFDM signal. Output to the power amplifier 5.

  The power amplifying unit 5 receives the IF signal of the OFDM signal from the equalizer 1, converts the frequency of the IF signal to the RF band, amplifies the power to a constant level, and then converts the signal component outside the necessary frequency band. Remove. The signal supplied to the transmission antenna 6 through the feeder line is radiated as a radio wave.

  The present invention has been described with reference to the embodiments. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the technical idea thereof. In the filter coefficient correction circuits 24-1 and 24-2 of the first and second embodiments, paying attention to the main wave, calculation is performed on the filter coefficient W (M, x) of the filter coefficient number of the main wave, and the phase A new filter coefficient W ′ (k, x) whose rotation is corrected is generated. The present invention is not limited to using the filter coefficient W (M, x) of the filter coefficient number of the main wave, and the calculation is performed on the filter coefficients W (k, x) of other filter coefficient numbers. And a new filter coefficient W ′ (k, x) may be generated.

  In the filter coefficient correction circuits 24-1 and 24-2 of the first and second embodiments, a new filter coefficient W ′ (k, x) is generated for each symbol. However, the present invention is not limited to this. Instead, a new filter coefficient W ′ (k, x) may be generated for a predetermined symbol interval, for example, every two or more symbols.

It is a block diagram which shows the structure of the equalization apparatus by embodiment of this invention. It is a block diagram which shows the structure of the filter coefficient generation circuit in an equalization apparatus. FIG. 3 is a block diagram illustrating a configuration of a filter coefficient correction circuit according to the first embodiment. FIG. 6 is a block diagram illustrating a configuration of a filter coefficient correction circuit according to a second embodiment. It is a block diagram which shows the structure of the relay apparatus using the equalization apparatus by embodiment of this invention. It is a block diagram which shows the structure of the filter coefficient generation circuit in the conventional equalization apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Equalizer 2 Relay apparatus 3 Reception antenna 4 Frequency conversion part 5 Power amplification part 6 Transmission antenna 10 Reference signal oscillation circuit 11 Frequency conversion circuit 12 AD conversion circuit 13 Orthogonal demodulation circuit 14 FIR filter circuit 15, 150 Filter coefficient generation circuit 16 Quadrature modulation circuit 17 DA conversion circuit 18 Frequency conversion circuit 20 FFT calculation circuit 21 SP extraction circuit 22 calculation circuit 23 IFFT calculation circuit 24 Filter coefficient correction circuit 30, 40 Data storage unit 31, 32, 41, 42, 43 calculation unit

Claims (7)

A first conversion circuit that performs frequency conversion and AD conversion of an OFDM signal based on a predetermined reference signal, an orthogonal demodulation circuit that orthogonally demodulates the converted OFDM signal, and a signal that is orthogonally demodulated by the orthogonal demodulation circuit A filter coefficient generation circuit for generating a filter coefficient, an FIR filter circuit for equalizing a signal demodulated by the orthogonal demodulation circuit using the filter coefficient generated by the filter coefficient generation circuit, and the FIR filter An orthogonal modulation circuit that orthogonally modulates the signal equalized by the circuit, and a second conversion circuit that performs DA conversion on the OFDM signal orthogonally modulated by the orthogonal modulation circuit and performs frequency conversion based on the predetermined reference signal In the OFDM digital signal equalizer provided,
The filter coefficient generation circuit includes:
An FFT operation circuit that performs an FFT process on the time domain signal orthogonally demodulated by the orthogonal demodulation circuit and converts the signal into a carrier symbol that is a frequency domain signal;
An SP extraction circuit for extracting an SP signal from the carrier symbol converted by the FFT operation circuit, and calculating a channel response based on the extracted SP signal;
An IFFT operation circuit that performs an IFFT process operation on the frequency domain signal of the channel response calculated by the SP extraction circuit, and converts it into a filter coefficient that is a time domain signal;
For the filter coefficients converted by the IFFT arithmetic circuit, the phase rotation amount is calculated using the filter coefficients of the main filter coefficient number among the filter coefficients of all the filter coefficient numbers, and all the values are calculated based on the phase rotation amount. A filter coefficient correction circuit that corrects the phase rotation in the filter coefficient of the filter coefficient number and generates a new filter coefficient,
The FIR filter circuit is
An OFDM digital signal equalization apparatus, wherein equalization is performed using a new filter coefficient generated by a filter coefficient correction circuit of the filter coefficient generation circuit. The OFDM digital signal equalizer according to claim 1,
The filter coefficient correction circuit includes:
A data storage unit that stores the filter coefficient of the filter coefficient number of the main wave among the filter coefficients of all filter coefficient numbers in the filter coefficient converted by the IFFT arithmetic circuit;
A filter coefficient stored in the data storage unit is complex-divided by the absolute value of the filter coefficient to obtain a correction amount, and the filter coefficients of all filter coefficient numbers are corrected based on the correction amount to obtain new filter coefficients. An arithmetic unit for generating
An OFDM digital signal equalizer characterized by comprising: The OFDM digital signal equalizer according to claim 1,
The filter coefficient correction circuit includes:
A data storage unit that stores the filter coefficient of the filter coefficient number of the main wave among the filter coefficients of all filter coefficient numbers in the filter coefficient converted by the IFFT arithmetic circuit;
An angle is calculated from the real axis value and the imaginary axis value in the complex plane of the filter coefficient stored in the data storage unit, and the filter coefficient of all filter coefficient numbers is corrected based on the angle to obtain a new filter coefficient. An arithmetic unit for generating
An OFDM digital signal equalizer characterized by comprising: The OFDM signal is frequency-converted and AD-converted based on a predetermined reference signal, the converted OFDM signal is orthogonally demodulated, a filter coefficient is generated based on the orthogonally demodulated signal, and the orthogonally demodulated signal is converted to the filter In an OFDM digital signal equalization method that equalizes using a coefficient, orthogonally modulates the equalized signal, DA-converts the orthogonally modulated OFDM signal, and performs frequency conversion based on the predetermined reference signal,
Performing an FFT process on the orthogonal demodulated time domain signal and converting it to a carrier symbol that is a frequency domain signal;
Extracting an SP signal from the converted carrier symbol and calculating a channel response based on the extracted SP signal;
Performing IFFT processing on the calculated frequency response signal of the channel response and converting it to a filter coefficient that is a time domain signal;
Calculating the amount of phase rotation using the filter coefficient of the filter coefficient number of the main wave among the filter coefficients of all filter coefficient numbers in the converted filter coefficient;
Correcting the phase rotation in the filter coefficients of all filter coefficient numbers based on the calculated phase rotation amount, and generating new filter coefficients;
An OFDM digital signal equalization method comprising: The OFDM signal is frequency-converted and AD-converted based on a predetermined reference signal, the converted OFDM signal is orthogonally demodulated, a filter coefficient is generated based on the orthogonally demodulated signal, and the orthogonally demodulated signal is converted to the filter In an OFDM digital signal equalization method that equalizes using a coefficient, orthogonally modulates the equalized signal, DA-converts the orthogonally modulated OFDM signal, and performs frequency conversion based on the predetermined reference signal,
Performing an FFT process on the orthogonal demodulated time domain signal and converting it to a carrier symbol that is a frequency domain signal;
Extracting an SP signal from the converted carrier symbol and calculating a channel response based on the extracted SP signal;
Performing IFFT processing on the calculated frequency response signal of the channel response and converting it to a filter coefficient that is a time domain signal;
Storing the filter coefficient of the main filter coefficient number among the filter coefficients of all filter coefficient numbers in the converted filter coefficient;
Obtaining a correction amount by complex-dividing the stored filter coefficient by an absolute value of the filter coefficient;
Correcting the filter coefficients of all filter coefficient numbers based on the correction amount to generate new filter coefficients;
An OFDM digital signal equalization method comprising: The OFDM signal is frequency-converted and AD-converted based on a predetermined reference signal, the converted OFDM signal is orthogonally demodulated, a filter coefficient is generated based on the orthogonally demodulated signal, and the orthogonally demodulated signal is converted to the filter In an OFDM digital signal equalization method that equalizes using a coefficient, orthogonally modulates the equalized signal, DA-converts the orthogonally modulated OFDM signal, and performs frequency conversion based on the predetermined reference signal,
Performing an FFT process on the orthogonal demodulated time domain signal and converting it to a carrier symbol that is a frequency domain signal;
Extracting an SP signal from the converted carrier symbol and calculating a channel response based on the extracted SP signal;
Performing IFFT processing on the calculated frequency response signal of the channel response and converting it to a filter coefficient that is a time domain signal;
Storing the filter coefficient of the main filter coefficient number among the filter coefficients of all filter coefficient numbers in the converted filter coefficient;
Calculating an angle from a real axis value and an imaginary axis value in a complex plane of the stored filter coefficients;
Correcting the filter coefficients of all filter coefficient numbers based on the angle to generate new filter coefficients;
An OFDM digital signal equalization method comprising: The OFDM digital signal relay apparatus using the OFDM digital signal equalization apparatus as described in any one of Claim 1 to 3 .

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