JP2010050834A - Ofdm digital signal equalizer, equalization method, and repeater device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To normally perform equalization even if phase rotation occurs in a filter coefficient within filter coefficient generation time when an FIR filter circuit inputs a signal for equalization and the filter coefficient delayed by filter coefficient generation time and uses the filter coefficient for equalization. <P>SOLUTION: A filter coefficient correction circuit 24-1 calculates the phase rotation of the filter coefficient occurring within the filter coefficient generation time, based on a filter coefficient W(k, x) of a symbol number (x) and a filter coefficient W(k, x-1) of a symbol number x-1 to estimate a new filter coefficient W'(k, x+y) of filter coefficient generation time (y symbol) ahead. An FIR filter circuit 14 uses a new filter coefficient W'(k, x+y) for equalization. As a result, the estimated filter coefficient W'(k, x+y) is corrected in terms of phase rotation and corresponds to a signal for equalization, thus normally performing equalization in the FIR filter circuit 14. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an OFDM (Orthogonal Frequency Division Multiplexing) digital signal equalization apparatus, an equalization method, and a relay apparatus, and in particular, a phase change of a filter coefficient caused by the generation time of a filter coefficient is already detected. The present invention relates to a technique for correcting using a calculated 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. For example, Patent Document 1 describes a technique in which an FIR filter improves characteristic deterioration of a received signal using a filter coefficient.

  FIG. 8 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.

  When the filter coefficient generation circuit 150 inputs the signal demodulated by the orthogonal demodulation circuit 13 in the previous stage, the FFT operation circuit 20 converts the orthogonally demodulated time domain signal into a frequency domain signal by FFT (Fast Fourier Transform). Then, the SP extraction circuit 21 extracts the SP signal and generates a channel response H (n). Then, 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).

  The filter coefficient W (k) is generated by the filter coefficient generation circuit 150, and it takes about several milliseconds (filter coefficient generation time) before the filter coefficient W (k) is generated. For this reason, in the FIR filter circuit 14, the timing for inputting the signal for equalization is different from the timing for inputting the filter coefficient W (k) corresponding to the signal for equalization. Deviation occurs.

  Originally, when the FIR filter circuit 14 inputs a signal to be equalized, a delay circuit is provided in the preceding stage, and the input timing of the signal to be equalized by the delay circuit is equal to the generation time of the filter coefficient W (k). The input timing of both data should be matched by delaying. However, since delaying the signal for equalization results in an overall processing delay and is not appropriate, such a delay circuit is not provided.

JP 2002-158632 A

  By the way, when receiving a multipath which is a radio wave reflected on topography or a building or the like, the received signal does not change greatly within the generation time of the filter coefficient W (k). Even if the input timing of the signal to be equalized differs from the input timing of the filter coefficient W (k), the multipath can be normally equalized without affecting the equalization performance. This is because the value of the filter coefficient W (k) does not change significantly within the generation time of the filter coefficient W (k), and the influence of multipath does not become a problem.

  However, when receiving a radio wave (SFN wave) from an SFN (Single Frequency Network) station, the received signal changes due to a difference in transmission frequency between a desired wave from the transmitting station and an SFN wave from the SFN station, In particular, when the transmission frequency difference increases, the change in the received signal also increases. For this reason, in the FIR filter circuit 14, when the input timing of the signal to be equalized and the input timing of the filter coefficient W (k) are different, the equalization performance is affected and the SFN wave can be normally equalized. Can not. This is because the influence of the SFN wave becomes a problem because the value of the filter coefficient W (k) changes within the generation time of the filter coefficient W (k).

  FIG. 9 is a diagram schematically illustrating filter coefficients in the case of receiving a multipath (a) and the case of receiving an SFN wave (b). As shown in FIG. 9A, when receiving a multipath, the phase of the multipath filter coefficient is constant with respect to the phase of the filter coefficient of the main wave, so that it does not rotate. On the other hand, as shown in FIG. 9B, when the SFN wave is received, the phase of the filter coefficient of the SFN wave rotates because it is not constant with respect to the phase of the filter coefficient of the main wave. This is because the difference between the transmission frequency of the desired wave, which is the main wave, and the transmission frequency of the SFN wave is within 1 Hz for management purposes, and is not necessarily the same frequency, and is a difference of 1 Hz or more. This is because it is possible.

  As described above, when the SFN wave is received, when the input timing of the signal to be equalized and the input timing of the filter coefficient W (k) are different in the FIR filter circuit 14, transmission between the desired wave and the SFN wave is performed. The phase of the filter coefficient of the SFN wave rotates due to the difference in frequency. This phase rotation becomes faster as the difference in transmission frequency is larger. For this reason, equalization performance falls and it cannot equalize a SFN wave normally.

  Therefore, the present invention has been made to solve the above-mentioned problems, and an object of the present invention is to input a signal for equalization by the FIR filter circuit and a filter coefficient delayed by a filter coefficient generation time, When performing equalization using the filter coefficient, even if phase rotation occurs in the filter coefficient within the filter coefficient generation time, an OFDM digital signal equalization apparatus and equalization method that can perform normalization normally And providing a relay device.

  In order to solve the above problems, an OFDM digital signal equalization apparatus according to claim 1 of the present invention includes a first conversion circuit that performs frequency conversion and AD conversion on an OFDM signal, and orthogonal demodulation that performs orthogonal demodulation on the converted OFDM signal. A quadrature demodulation circuit using a quadrature demodulation circuit, a filter coefficient generation circuit that generates a filter coefficient based on a signal demodulated by the quadrature demodulation circuit, and a filter coefficient generated by the filter coefficient generation circuit FIR filter circuit for equalizing the modulated signal, quadrature modulation circuit for quadrature modulating the signal equalized by the FIR filter circuit, and DA conversion and frequency conversion of the OFDM signal quadrature modulated by the quadrature modulation circuit In the OFDM digital signal equalization apparatus comprising two conversion circuits, the filter coefficient generation circuit includes the An FFT processing circuit that performs FFT processing on the time domain signal orthogonally demodulated by the demodulating circuit and converts it to a carrier symbol that is a frequency domain signal, and an SP signal from the carrier symbol converted by the FFT operating circuit. An SP extraction circuit that extracts and calculates a channel response based on the extracted SP signal, and performs an IFFT process operation on the frequency domain signal of the channel response calculated by the SP extraction circuit, Based on the IFFT operation circuit for converting to a certain filter coefficient, the current filter coefficient converted by the IFFT operation circuit and the past filter coefficient, the current filter coefficient is corrected, and the conversion process by the FFT operation circuit A new filter coefficient generation time ahead until a new filter coefficient is generated A filter coefficient correction circuit for estimating a filter coefficient, wherein the FIR filter circuit performs equalization using the new filter coefficient estimated by the filter coefficient correction circuit of the filter coefficient generation circuit. To do.

  An OFDM digital signal equalization apparatus according to a second aspect of the present invention is the OFDM digital signal equalization apparatus according to the first aspect, wherein the filter coefficient correction circuit includes a current filter coefficient and one symbol before the present. A correction amount between symbols is calculated using a data storage unit that stores the filter coefficients of the current filter coefficient, a current filter coefficient stored in the data storage unit, and a filter coefficient that is one symbol before the current one, and And a calculation unit that calculates a correction amount in the filter coefficient generation time based on an inter-symbol correction amount and corrects the current filter coefficient to estimate a new filter coefficient.

  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 a current filter coefficient and a filter coefficient that is greater than a current filter coefficient. A data storage unit for storing a filter coefficient before the generation time, a current filter coefficient stored in the data storage unit and a filter coefficient before the filter coefficient generation time, and a correction amount at the filter coefficient generation time. A calculation unit that calculates and corrects the current filter coefficient to estimate a new filter coefficient.

  An OFDM digital signal equalization apparatus according to a fourth aspect of the present invention is the OFDM digital signal equalization apparatus according to the first aspect, wherein the filter coefficient correction circuit includes a filter coefficient from before the filter coefficient generation time to the present time. Is calculated for each symbol from the time before the filter coefficient generation time to the present time, using a data storage unit for storing each symbol, and a filter coefficient stored in the data storage unit. A calculation unit that calculates a correction amount in the filter coefficient generation time based on each correction amount between symbols, and corrects the current filter coefficient to estimate a new filter coefficient; To do.

  An OFDM digital signal equalization apparatus according to claim 5 according to the present invention is the OFDM digital signal equalization apparatus according to any one of claims 1 to 4, wherein the estimation of the new filter coefficient is preset. It is characterized by being performed at a specified time interval.

  An OFDM digital signal equalization apparatus according to claim 6 of the present invention is the OFDM digital signal equalization apparatus according to claim 3, wherein the new filter coefficient is estimated every time the filter coefficient is generated. It is characterized by.

  Also, the OFDM digital signal equalization method according to claim 7 of the present invention performs frequency conversion and AD conversion on the OFDM signal, orthogonally demodulates the converted OFDM signal, and generates a filter coefficient based on the orthogonally demodulated signal. In the OFDM digital signal equalization method, the orthogonal demodulated signal is equalized using the filter coefficient, the equalized signal is orthogonally modulated, and the orthogonally modulated OFDM signal is DA-converted and frequency-converted. An operation of FFT processing is performed on the demodulated time domain signal to convert it to a carrier symbol that is a frequency domain signal, an SP signal is extracted from the converted carrier symbol, and a channel is determined based on the extracted SP signal. A step of calculating a response, and performing IFFT processing on the frequency domain signal of the calculated channel response Performing calculation and converting to a filter coefficient which is a time domain signal; storing the converted filter coefficient as a current filter coefficient; and continuously storing a filter coefficient one symbol before the current stored coefficient Calculating a correction amount between one symbol using the stored current filter coefficient and the filter coefficient one symbol before the current, and generating the filter coefficient based on the correction amount between the one symbol Calculating a correction amount in time; and correcting the current filter coefficient to estimate a new filter coefficient.

  Also, the OFDM digital signal equalization method according to claim 8 of the present invention performs frequency conversion and AD conversion on the OFDM signal, orthogonally demodulates the converted OFDM signal, and generates a filter coefficient based on the orthogonally demodulated signal. In the OFDM digital signal equalization method, the orthogonal demodulated signal is equalized using the filter coefficient, the equalized signal is orthogonally modulated, and the orthogonally modulated OFDM signal is DA-converted and frequency-converted. An operation of FFT processing is performed on the demodulated time domain signal to convert it to a carrier symbol that is a frequency domain signal, an SP signal is extracted from the converted carrier symbol, and a channel is determined based on the extracted SP signal. A step of calculating a response, and performing IFFT processing on the frequency domain signal of the calculated channel response Performing a calculation and converting to a filter coefficient which is a time domain signal; storing the converted filter coefficient as a current filter coefficient; and continuously storing the filter coefficient before the filter coefficient generation time already stored Calculating a correction amount at the filter coefficient generation time using the stored current filter coefficient and the filter coefficient before the filter coefficient generation time; and correcting the current filter coefficient to obtain a new filter coefficient And a step of estimating.

  The OFDM digital signal equalization method according to claim 9 of the present invention performs frequency conversion and AD conversion on an OFDM signal, orthogonally demodulates the converted OFDM signal, and generates a filter coefficient based on the orthogonally demodulated signal. In the OFDM digital signal equalization method, the orthogonal demodulated signal is equalized using the filter coefficient, the equalized signal is orthogonally modulated, and the orthogonally modulated OFDM signal is DA-converted and frequency-converted. An operation of FFT processing is performed on the demodulated time domain signal to convert it to a carrier symbol that is a frequency domain signal, an SP signal is extracted from the converted carrier symbol, and a channel is determined based on the extracted SP signal. A step of calculating a response, and performing IFFT processing on the frequency domain signal of the calculated channel response A step of calculating and converting to a filter coefficient which is a time domain signal, and a filter between the filter coefficient generation time and the present time including the converted filter coefficient by shifting the already stored filter coefficient Storing a coefficient for each symbol, using the stored filter coefficient, calculating a correction amount between one symbol from before the filter coefficient generation time to the present, and each between the one symbol And calculating a correction amount in the filter coefficient generation time based on the correction amount, and estimating the new filter coefficient by correcting the current filter coefficient.

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

  As described above, according to the present invention, the phase rotation of the filter coefficient generated within the filter coefficient generation time is calculated based on past data, and a new filter coefficient for correcting the phase rotation is estimated. did. As a result, when the FIR filter circuit inputs the signal to be equalized and the filter coefficient delayed by the filter coefficient generation time, and performs equalization using the filter coefficient, the phase is within the filter coefficient generation time. Even if the rotation occurs, the filter coefficient temporally corresponds to the signal to be equalized, so that equalization can be normally performed.

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 signal serving as a reference for frequency-converting the OFDM signal in the frequency conversion circuits 11 and 18 and outputs the signal to the frequency conversion circuits 11 and 18 as a reference signal.

  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. Details of the process of generating the filter coefficient W (k) and the process of generating the 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 configuration diagram in which the FIR filter circuit 14 and the filter coefficient generation circuit 15 are extracted from the components of the equalization apparatus 1 shown in FIG. 1, and the delay time of the filter coefficient generation circuit 15 in the equalization apparatus 1 is described. It is a figure to do. FIG. 3 is a block diagram showing the 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.

  Referring to FIG. 2, filter coefficient generation circuit 15 receives a signal demodulated by orthogonal demodulation circuit 13 and generates filter coefficient W ′ (k) for a predetermined time (filter coefficient generation time). ). Therefore, the FIR filter circuit 14 receives the quadrature demodulated signal from the quadrature demodulation circuit 13 and generates a filter coefficient for the signal to be equalized when equalization is performed using the filter coefficient W ′ (k). The equalization is performed using the filter coefficient W ′ (k) delayed by the time.

  By the way, when the multipath is received, the phase of the multipath filter coefficient does not rotate within the filter coefficient generation time, and is therefore constant with respect to the phase of the main wave filter coefficient. Therefore, even if the FIR filter circuit 14 performs equalization on the signal to be equalized using the filter coefficient W ′ (k) delayed by the filter coefficient generation time, the filter coefficient is within the filter coefficient generation time. Since W ′ (k) does not change much, equalization can be performed normally.

  However, when an SFN wave is received, the transmission frequency of the main wave, which is the desired wave, and the transmission frequency of the SFN wave are different within the filter coefficient generation time, and therefore the phase of the filter coefficient of the SFN wave is rotated. Therefore, in the embodiment of the present invention, the filter coefficient generation circuit 15 calculates the rotation phase based on the generated current filter coefficient W (k) and the past filter coefficient, and sets the current filter coefficient W (k). On the other hand, a correction for the calculated phase rotation is added to generate a new filter coefficient W ′ (k). Then, the FIR filter circuit 14 performs equalization using the new filter coefficient W ′ (k). As a result, the filter coefficient W ′ (k) becomes a filter coefficient corresponding to the signal to be equalized, so that the FIR filter circuit 14 delays the signal to be equalized by the filter coefficient generation time. Even if equalization is performed using '(k)', equalization can be performed normally.

  Referring to FIG. 3, an FFT operation circuit 20 receives an orthogonal demodulated signal from the orthogonal demodulation circuit 13, performs an FFT process on the time domain signal, converts it to a carrier symbol which is a frequency domain signal, The carrier symbol is output to the SP extraction circuit 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 correction circuit 24 receives the filter coefficient W (k) from the IFFT arithmetic circuit 23, and uses the input filter coefficient W (k) and the filter coefficient input in the past, the filter coefficient W after the filter coefficient generation time. '(K) is estimated, and the filter coefficient W' (k) is output to the FIR filter circuit 14. In this case, the FIR filter circuit 14 can perform equalization using the filter coefficient W ′ (k) corresponding to the signal to be equalized (in terms of time).

[Example 1]
Next, the filter coefficient correction circuit 24 shown in FIGS. 2 and 3 will be described. First, the filter coefficient correction circuit 24-1 of the first embodiment will be described. FIG. 4 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 to 33. The filter coefficient correction circuit 24-1 receives the filter coefficient W (k, x) from the IFFT calculation circuit 23, and the current filter coefficient W (k, k, x) and the filter coefficient W (k, x−1) one symbol before are used to calculate the correction amount of the phase rotation of the filter coefficient W (k, x), and the filter coefficient W ′ (k, x, y symbol ahead) x + y) is estimated. Then, the estimated filter coefficient W ′ (k, x + y) is output to the FIR filter circuit 14. The filter coefficient W ′ (k, x + y) y symbols ahead of the current output as described above is a filter coefficient corresponding to the signal to be equalized in the FIR filter circuit 14. Here, x indicates a symbol number. Note that y is a preset value (the same applies to Examples 2 and 3). Also, it is assumed that the amplitude of the filter coefficient does not change within the filter coefficient generation time (the same applies to the second and third embodiments).

  The data storage unit 30 stores a first storage unit that stores a filter coefficient W (k, x) of the current symbol number x, and a filter coefficient W (one symbol number x−1 immediately before the current symbol number x). k, x-1). Each time the symbol number advances with the passage of time, the filter coefficient W (k, x) stored in the first storage unit is shifted to the second storage unit, and the filter coefficient W is stored in the second storage unit. Stored as (k, x-1). Then, the filter coefficient W (k, x) of the new symbol number x is stored in the first storage unit.

The calculation unit 31 reads the filter coefficient W (k, x) and the filter coefficient W (k, x−1) from the data storage unit 30, calculates the correction amount C by the following complex calculation formula, and calculates the correction amount C. To the unit 32.
C = W (k, x) / W (k, x-1)
Here, the correction amount C is a phase rotation with respect to the filter coefficient W (k, x) of the symbol number x with reference to the filter coefficient W (k, x-1) of the symbol number x-1 in the filter coefficient number k. The degree (angle shift amount) is shown. That is, the degree of phase rotation of one symbol that is a period from symbol number x-1 to symbol number x is shown.

The calculation unit 32 receives the correction amount C from the calculation unit 31, calculates the correction amount C ′ of the y symbol that is the filter coefficient generation time by the following formula, and outputs the correction amount C ′ to the calculation unit 33. .
C ′ = C ^y
Here, the correction amount C ′ is a phase with respect to the filter coefficient W (k, x) of the symbol number x with reference to the filter coefficient W (k, x−1) of the symbol number x−1 in the filter coefficient number k. The degree of rotation of the y symbol is shown by expanding the degree of rotation (the degree of phase rotation of one symbol) to the y symbol.

The calculation unit 33 reads the filter coefficient W (k, x) of the symbol number x from the data storage unit 30 and inputs the correction amount C ′ from the calculation unit 32, and the filter coefficient W (k, x) by the following equation. , And a new filter coefficient W ′ (k, x + y) ahead of y symbols is estimated. The filter coefficient W ′ (k) estimated in this way is output to the FIR filter circuit 14.
W ′ (k, x + y) = W (k, x) · C ′
= W (k, x) · C ^y

  As described above, according to the equalization apparatus 1 including the filter coefficient generation circuit 15 including the filter coefficient correction circuit 24-1 of the first embodiment, the phase rotation of the filter coefficient generated within the filter coefficient generation time is Is calculated based on the filter coefficient W (k, x) of the symbol number x and the filter coefficient W (k, x-1) of the past symbol number x-1, and the phase rotation is corrected to generate the filter coefficient generation time ( A new filter coefficient W ′ (k, x + y) ahead of (y symbols) is estimated. The FIR filter circuit 14 receives the equalization signal and the filter coefficient W ′ (k, x + y) ahead of the filter coefficient generation time, and performs equalization. As a result, even if phase rotation occurs in the filter coefficient within the filter coefficient generation time, the estimated filter coefficient W ′ (k, x + y) is corrected for phase rotation and corresponds to the signal to be equalized. Therefore, normalization can be performed normally in the FIR filter circuit 14.

  For example, when an SFN wave is received, the phase rotation of the filter coefficient may occur within the filter coefficient generation time, and the equalization apparatus 1 can perform equalization normally by the processing described above. When multipath is received, phase rotation of the filter coefficient does not occur within the filter coefficient generation time, but the correction amount becomes zero in the filter coefficient correction circuit 24-1. Can be equalized correctly. Therefore, according to the equalizer 1, it is possible to perform equalization normally even when the SFN wave and the multipath are received simultaneously.

  Further, according to the equalizer 1, the data storage unit 30 only needs to store two filter coefficients W (k, x) and filter coefficients W (k, x-1), so that y + 1 filter coefficients. Compared to the second and third embodiments (details will be described later), the storage amount is small.

[Example 2]
Next, the filter coefficient correction circuit 24-2 of the second embodiment will be described. FIG. 5 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 and 42. The filter coefficient W (k, x) is input from the IFFT calculation circuit 23 and the current filter coefficient W (k, k, x) is input. The correction amount of the phase rotation of the filter coefficient W (k, x) is calculated using the filter coefficient W (k, xy) before x) and y symbols (filter coefficient generation time), and the filter after y symbols The coefficient W ′ (k, x + y) is estimated. Then, the estimated filter coefficient W ′ (k, x + y) is output to the FIR filter circuit 14. The filter coefficient W ′ (k, x + y) ahead of y symbols output in this way as a reference is a filter coefficient corresponding to the signal to be equalized in the FIR filter circuit 14.

  The data storage unit 40 stores a first storage unit that stores a filter coefficient W (k, x) of the current symbol number x, and a filter coefficient W ( In the same manner as the second storage unit storing k, x−1), the y + 1th storing the filter coefficient W (k, xy) of the symbol number xy preceding the current symbol number by y symbols. Storage unit. That is, the data storage unit 40 stores y + 1 filter coefficients from the symbol number x to the symbol number xy. Each time the symbol number advances with the passage of time, the filter coefficient W (k, x) stored in the first storage unit shifts to the second storage unit, and the filter coefficient W ( k, x-1). Further, the filter coefficient W (k, x−1) stored in the second storage unit is shifted to the third storage unit, and is stored as the filter coefficient W (k, x−2) in the third storage unit. The Similarly, the filter coefficient W (k, xy + 1) stored in the yth storage unit is shifted to the y + 1th storage unit, and the filter coefficient W (k, xy) is stored in the y + 1th storage unit. Remembered. Then, the filter coefficient W (k, x) of the new symbol number x is stored in the first storage unit.

The calculation unit 41 reads the filter coefficient W (k, x) and the filter coefficient W (k, xy) from the data storage unit 40, calculates the correction amount C by the following complex calculation formula, and calculates the correction amount C. To the unit 42.
C = W (k, x) / W (k, xy)
Here, the correction amount C is a phase rotation with respect to the filter coefficient W (k, x) of the symbol number x with reference to the filter coefficient W (k, xy) of the symbol number xy at the filter coefficient number k. The degree (angle shift amount) is shown. That is, the correction amount C indicates the degree of phase rotation of the y symbol that is the period from the symbol number xy to the symbol number x.

The calculation unit 42 reads out the filter coefficient W (k, x) of the symbol number x from the data storage unit 40 and inputs the correction amount C from the calculation unit 41, and calculates the filter coefficient W (k, x) by the following equation. The phase is corrected, and a new filter coefficient W ′ (k, x + y) ahead of y symbols is estimated. The filter coefficient W ′ (k) estimated in this way is output to the FIR filter circuit 14.
W ′ (k, x + y) = 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 24-2 of the second embodiment, the phase rotation of the filter coefficient generated within the filter coefficient generation time is Is calculated based on the filter coefficient W (k, x) of the symbol number x and the filter coefficient W (k, xy) of the past symbol number xy, and the phase rotation is corrected to generate the filter coefficient generation time ( A new filter coefficient W ′ (k, x + y) ahead of (y symbols) is estimated. The FIR filter circuit 14 receives the equalization signal and the filter coefficient W ′ (k, x + y) ahead of the filter coefficient generation time, and performs equalization. As a result, even if a phase rotation occurs in the filter coefficient within the filter coefficient generation time, the estimated filter coefficient W ′ (k, x + y) is corrected for the phase rotation and corresponds to the signal to be equalized. Therefore, normalization can be performed normally in the FIR filter circuit 14. As in the first embodiment, it is effective when, for example, an SFN wave is received. As in the first embodiment, the equalization apparatus 1 can perform equalization normally even when multipath is received and when the SFN wave and multipath are received simultaneously. .

Example 3
Next, the filter coefficient correction circuit 24-3 of Example 3 will be described. FIG. 6 is a block diagram illustrating a configuration of the filter coefficient correction circuit 24-3 of the third embodiment. The filter coefficient correction circuit 24-3 includes a data storage unit 50 and calculation units 51 and 52. The filter coefficient correction circuit 24-3 receives the filter coefficient W (k, x) from the IFFT calculation circuit 23, and the current filter coefficient W (k, x, x) Using the filter coefficient W (k, x−1) one symbol before and the filter coefficient W (k, xy) before y symbol (filter coefficient generation time), that is, y symbol from the present. Using the previous y + 1 filter coefficients, the correction amount of the phase rotation of the filter coefficient W (k, x) is calculated, and the filter coefficient W ′ (k, x + y) ahead of the y symbol is estimated. Then, the estimated filter coefficient W ′ (k, x + y) is output to the FIR filter circuit 14. The filter coefficient W ′ (k, x + y) ahead of y symbols output in this way as a reference is a filter coefficient corresponding to the signal to be equalized in the FIR filter circuit 14.

  Similar to the data storage unit 40 of the second embodiment, the data storage unit 50 includes a filter coefficient W (k, x) of the current symbol number x and a filter of the symbol number x-1 one before the current symbol number x. Store y + 1 filter coefficients such as coefficient W (k, x-1). Each time the symbol number advances with time, the stored filter coefficient shifts.

The calculation unit 51 reads the filter coefficient W (k, xy + 1) from the yth storage unit in the data storage unit 50, and also reads the filter coefficient W (k, xy) from the y + 1th storage unit. The correction amount W ′ _y−1 is calculated using the complex arithmetic expression of
W ′ _y−1 = W (k, xy + 1) / W (k, xy)
Here, the correction amount W ′ _y−1 is the filter coefficient W (k) of the symbol number xy + 1 based on the filter coefficient W (k, xy) of the symbol number xy in the filter coefficient number k. , Xy + 1) shows the degree of phase rotation (angle deviation). That is, the correction amount W ′ _y−1 indicates the degree of phase rotation of one symbol that is a period from the symbol number xy to the symbol number xy + 1.

The calculation unit 51 reads the filter coefficient W (k, xy + 2) from the y−1th storage unit in the data storage unit 50 and reads the filter coefficient W (k, xy + 1) from the yth storage unit. The correction amount W ′ _y−2 is calculated by the following complex arithmetic expression.
W ′ _y−2 = (W (k, xy + 2) / W (k, xy + 1)) · W ′ _y−1
Here, the correction amount W _'y-2, in the filter coefficient number k, the filter coefficient W (k, x-y) of the symbol number x-y to a reference, symbol number x-y + 2 of the filter coefficient W (k , Xy + 2) shows the degree of phase rotation (angle shift amount). That is, the correction amount W ′ _y−2 indicates the degree of phase rotation of two symbols that is the period from the symbol number xy to the symbol number xy + 2.

The calculation unit 51 repeats the same processing to read out the filter coefficient W (k, x−1) from the second storage unit in the data storage unit 50 and the filter coefficient W (k, x−) from the third storage unit. 2) is read, and the correction amount W ′ ₁ is calculated by the following complex arithmetic expression.
W ′ ₁ = (W (k, x−1) / W (k, x−2)) · W ′ ₂
Here, the correction amount W ′ ₁ is the filter coefficient W (k, x) of the symbol number x−1 with reference to the filter coefficient W (k, xy) of the symbol number xy in the filter coefficient number k. -1) shows the degree of phase rotation (angle shift amount). That is, the correction amount W ′ ₁ indicates the degree of phase rotation of the y−1 symbol that is the period from the symbol number xy to the symbol number x−1.

The calculation unit 51 reads the filter coefficient W (k, x) from the first storage unit in the data storage unit 50 and reads the filter coefficient W (k, x−1) from the second storage unit. The correction amount C is calculated using an arithmetic expression.
C = (W (k, x) / W (k, x−1)) · W ′ ₁
Here, the correction amount C is a phase rotation with respect to the filter coefficient W (k, x) of the symbol number x with reference to the filter coefficient W (k, xy) of the symbol number xy at the filter coefficient number k. The degree (angle shift amount) is shown. That is, the correction amount C indicates the degree of phase rotation of the y symbol that is the period from the symbol number xy to the symbol number x.

The calculation unit 52 reads out the filter coefficient W (k, x) of the symbol number x from the data storage unit 50 and also reads out the correction amount C from the calculation unit 51, and calculates the phase of the filter coefficient W (k, x) by the following equation Correction is performed, and a new filter coefficient W ′ (k, x + y) ahead of y symbols is estimated. The filter coefficient W ′ (k) estimated in this way is output to the FIR filter circuit 14.
W ′ (k, x + y) = 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 24-3 of the third embodiment, the phase rotation of the filter coefficient generated within the filter coefficient generation time is Is calculated based on the filter coefficient between the filter coefficient W (k, x) of the symbol number x of the first symbol and the filter coefficient W (k, xy) of the symbol number xy before the y symbol, and its phase rotation Is corrected and a new filter coefficient W ′ (k, x + y) ahead of the filter coefficient generation time (y symbol) is estimated. The FIR filter circuit 14 receives the equalization signal and the filter coefficient W ′ (k, x + y) ahead of the filter coefficient generation time, and performs equalization. As a result, even if a phase rotation occurs in the filter coefficient within the filter coefficient generation time, the estimated filter coefficient W ′ (k, x + y) is corrected for the phase rotation and corresponds to the signal to be equalized. Therefore, normalization can be performed normally in the FIR filter circuit 14. As in the first and second embodiments, this is effective when, for example, an SFN wave is received. Further, as in the first and second embodiments, the equalization apparatus 1 can perform equalization normally even when multipath is received and when the SFN wave and multipath are received simultaneously. It becomes.

  Further, according to the equalizing apparatus 1, from the filter coefficient W (k, x) of the current symbol number x to the filter coefficient W (k, xy) of the symbol number xy before the y symbol. The correction amount C is calculated based on the respective filter coefficients. Accordingly, it is possible to estimate the filter coefficient W ′ (k, x + y) with higher accuracy than in the first and second embodiments in which the correction amount is calculated based on the filter coefficient of 2 symbols. For example, when receiving an SFN wave, even if the frequency changes within the filter coefficient generation time, the filter coefficient correction circuit 24-3 calculates the correction amount C based on the filter coefficient for each symbol. The filter coefficient W ′ (k, x + y) corresponding to the frequency change can be estimated.

[Repeater]
Next, a relay apparatus using the equalization apparatus 1 including any one of the filter coefficient correction circuits 24 according to the first to third embodiments will be described. FIG. 7 is a block diagram illustrating a configuration of the relay device. The relay device 2 includes a reception antenna 3, a frequency conversion unit 4, an equalization device 1, 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 to 24-3 of the first to third embodiments, a correction amount is calculated for each symbol and a new filter coefficient W ′ (k, x + y) is estimated. Is not limited to this. For example, a correction amount may be calculated for each of two or more symbols, and a new filter coefficient W ′ (k, x + y) may be estimated. For example, by setting every y symbol, the data storage unit 40 in the filter coefficient correction circuit 24-2 of the second embodiment causes two filter coefficients W (k, x) and W (k, xy) for each y symbol. ) Need only be stored, so that the storage amount is small.

It is a block diagram which shows the structure of the equalization apparatus by embodiment of this invention. It is a figure explaining the delay time of the filter coefficient production | generation circuit in an equalization apparatus. 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. FIG. 10 is a block diagram illustrating a configuration of a filter coefficient correction circuit according to a third 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. It is a figure which shows typically the filter coefficient in the case of receiving a multipath and the case of receiving an SFN wave.

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 Orthogonal 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 circuits 30, 40, 50 Data storage units 31, 32, 33, 41, 42, 51 , 52 Calculation unit

Claims (10)

A filter coefficient is generated based on a first conversion circuit that performs frequency conversion and AD conversion on an OFDM signal, an orthogonal demodulation circuit that orthogonally demodulates the converted OFDM signal, and a signal orthogonally demodulated by the orthogonal demodulation circuit A filter coefficient generation circuit, 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 a signal equalized by the FIR filter circuit An OFDM digital signal equalization apparatus comprising: a quadrature modulation circuit that performs quadrature modulation; and a second conversion circuit that performs DA conversion and frequency conversion on an OFDM signal orthogonally modulated by the orthogonal modulation circuit,
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;
Based on the current filter coefficient and the past filter coefficient converted by the IFFT arithmetic circuit, the current filter coefficient is corrected, and the process from the conversion process by the FFT arithmetic circuit to the generation of the new filter coefficient A filter coefficient correction circuit that estimates a new filter coefficient ahead of the filter coefficient generation time, and
The FIR filter circuit is
An OFDM digital signal equalization apparatus, wherein equalization is performed using a new filter coefficient estimated 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 for storing the current filter coefficient and the filter coefficient one symbol before the current;
Using the current filter coefficient stored in the data storage unit and the filter coefficient one symbol before the current, a correction amount between one symbol is calculated, and based on the correction amount between the one symbol, the filter coefficient A calculation unit that calculates a correction amount in the generation time, corrects the current filter coefficient, and estimates a new filter coefficient;
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 for storing a current filter coefficient and a filter coefficient before the filter coefficient generation time from the current time;
Using the current filter coefficient stored in the data storage unit and the filter coefficient before the filter coefficient generation time, a correction amount at the filter coefficient generation time is calculated, and the current filter coefficient is corrected to obtain a new filter. An arithmetic unit for estimating a coefficient;
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, for each symbol, filter coefficients from before the filter coefficient generation time to the present time;
Using the filter coefficient stored in the data storage unit, the correction amount between one symbol is calculated from before the filter coefficient generation time to the present time, and based on the respective correction amount between the one symbol, A calculation unit that calculates a correction amount in the filter coefficient generation time, corrects the current filter coefficient, and estimates a new filter coefficient;
An OFDM digital signal equalizer characterized by comprising: In the OFDM digital signal equalizer according to any one of claims 1 to 4,
An OFDM digital signal equalization apparatus, wherein the new filter coefficient is estimated at a preset time interval. The OFDM digital signal equalization apparatus according to claim 3,
An OFDM digital signal equalizing apparatus, wherein the new filter coefficient is estimated every filter coefficient generation time. Frequency-converting and AD-converting an OFDM signal, orthogonally demodulating the converted OFDM signal, generating a filter coefficient based on the orthogonally demodulated signal, equalizing the orthogonally demodulated signal using the filter coefficient, In the OFDM digital signal equalization method of orthogonally modulating the equalized signal and performing DA conversion and frequency conversion on the orthogonally modulated OFDM 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 converted filter coefficient as a current filter coefficient, and continuing to store the filter coefficient one symbol before the current stored coefficient;
Calculating a correction amount between one symbol using the stored current filter coefficient and the filter coefficient one symbol before the current;
Calculating a correction amount in the filter coefficient generation time based on the correction amount between the one symbol;
Correcting the current filter coefficients to estimate new filter coefficients;
An OFDM digital signal equalization method comprising: Frequency-converting and AD-converting an OFDM signal, orthogonally demodulating the converted OFDM signal, generating a filter coefficient based on the orthogonally demodulated signal, equalizing the orthogonally demodulated signal using the filter coefficient, In the OFDM digital signal equalization method of orthogonally modulating the equalized signal and performing DA conversion and frequency conversion on the orthogonally modulated OFDM 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 converted filter coefficient as a current filter coefficient, and continuing to store the already stored filter coefficient before the filter coefficient generation time;
Calculating a correction amount in the filter coefficient generation time using the stored current filter coefficient and the filter coefficient before the filter coefficient generation time;
Correcting the current filter coefficients to estimate new filter coefficients;
An OFDM digital signal equalization method comprising: Frequency-converting and AD-converting an OFDM signal, orthogonally demodulating the converted OFDM signal, generating a filter coefficient based on the orthogonally demodulated signal, equalizing the orthogonally demodulated signal using the filter coefficient, In the OFDM digital signal equalization method of orthogonally modulating the equalized signal and performing DA conversion and frequency conversion on the orthogonally modulated OFDM 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;
Shifting the already stored filter coefficients, including the converted filter coefficients, and storing the filter coefficients from before the filter coefficient generation time to the present for each symbol;
Using the stored filter coefficients, respectively, calculating a correction amount between one symbol from before the filter coefficient generation time to the present time;
Calculating a correction amount in the filter coefficient generation time based on each correction amount between the one symbol, correcting the current filter coefficient, and estimating a new filter coefficient;
An OFDM digital signal equalization method comprising:   An OFDM digital signal relay device using the OFDM digital signal equalization device according to any one of claims 1 to 6.

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