TWI463846B - Orthogonal Frequency Division Multiple Modulation (OFDM) Receiver - Google Patents

Description

Orthogonal frequency division multiplexing modulation (OFDM) receiving device

Embodiments of the present invention relate to estimation of a transmission path response in an OFDM receiving apparatus.

In the terrestrial wave digital broadcasting, an orthogonal frequency division multiplexing method (hereinafter referred to as an OFDM method) using complex carriers orthogonal to each other is used as the modulation method.

In general, the signal format of the OFDM system is multiplexed with a scattered pilot signal (hereinafter referred to as an SP signal) in addition to the data signal, and is interpolated in the time direction and the frequency direction. The inserted SP signal estimates the transmission path response, and equalizes the multipath distortion and the like.

In the state of being transmitted from the broadcast station, the SP signal is intermittently inserted in the transmission signal by the predetermined number of symbols in the time direction and the frequency direction. On the receiving device, the SP signal is extracted from the transmitted transmission signal, and all symbols of the data signal are interpolated using the interpolation filter for the SP signal in the time direction and the frequency direction, and the interpolated signal is used. All SP signals are used to estimate the transmission path response.

The interpolation filter of the SP signal is preferable because a large number of delayed wave components of a delayed wave (referred to as a long delayed wave) having a long delay time due to multiple paths can be passed, and noise components can be removed.

The object of the present invention is to provide an interpolation filter for SP signals in a multipath path, which allows a delayed wave component containing a long delay wave to pass, and improves noise removal performance to improve reception performance. OFDM receiving device.

An OFDM receiving apparatus according to an embodiment includes a filter unit that limits a channel estimation signal in a frequency direction using a complex filter characteristic, and an equalization unit that uses an output of a pre-filter unit The receiving signal is equalized; and the quality detecting department detects the receiving quality of the output of the preamplifier; and the determining unit uses the detected receiving quality to learn from the complex filter characteristics Determining the best one; the pre-complex filter characteristic has a filter characteristic of a predetermined bandwidth and a complex filter characteristic that allows one of the predetermined bandwidths to be transparent; the complex filter characteristic of the pre-recorded partial pass contains two The above passband.

According to the OFDM receiving apparatus configured as above, the interpolation signal of the SP signal in the multipath can be passed through the delay wave component containing the long delay wave, and the noise removal performance can be improved to improve the reception performance. .

Hereinafter, embodiments will be described in detail with reference to the drawings.

[First Embodiment]

Fig. 1 is a block diagram of an OFDM receiving apparatus according to a first embodiment.

In FIG. 1, the OFDM receiving apparatus 100 includes an antenna 1, a selector 2, an A/D converter 3, an IQ demodulation circuit 4, an FFT circuit 5, an FFT window control circuit 6, and a first equalization circuit. 7. The first SP time interpolation filter 8, the first SP frequency interpolation filter 9, the error correction circuit 10, the first coefficient switching circuit 11, and the coefficient decision circuit 12.

The OFDM receiving apparatus 100 transmits, for example, a transmission signal (hereinafter referred to as an OFDM signal) according to the OFDM method through a wireless transmission path. In addition, it can also be received via a wired transmission path.

The selector 2 converts the RF signal received by the antenna 1 into an IF signal, and outputs the IF signal to the A/D conversion circuit 3. The A/D conversion circuit 3 performs A/D conversion on the IF signal supplied from the selector 2, and outputs the digital IF signal to the IQ demodulation circuit 4.

The IQ demodulation circuit 4 obtains the time domain OFDM signal from the IF signal supplied from the A/D conversion circuit 3 by performing quadrature demodulation. The IQ demodulation circuit 4 outputs the time domain OFDM signal to the FFT circuit 5 and the FFT window control circuit 6.

The FFT circuit 5 extracts a signal of a range of effective symbol lengths from signals of one OFDM symbol based on the FFT window control signal supplied from the FFT window control circuit 6. Further, the FFT circuit 5 generates an OFDM signal in the frequency domain by performing FFT calculation on the OFDM signal of the extracted time domain, and outputs it to the first equalizing circuit 7 and the first SP time interpolation filter 8.

The FFT window control circuit 6 detects the timing of the main wave from the received signal, and uses the FFT output as the reference to determine the FFT window position. The FFT circuit 5 converts the OFDM signal of the time axis into a signal on the frequency axis in accordance with the FFT window position. The output of the FFT circuit 5 is the signal wave configuration shown in the signal format of FIG.

In the signal format example of the OFDM signal shown in FIG. 2, the information symbol S1, the TMCC/AC symbol S2 indicating the transmission mode of the OFDM signal, the CP symbol S3 indicating the end of the OFDM signal, and the symbol belonging to the SP signal are included. Each symbol of the SP symbol S4. The SP symbol S4 is inserted, for example, at a ratio of 1/3 in the frequency direction and 1/4 in the time direction.

In the first SP time interpolation filter 8, the SP signal is extracted from the OFDM signal in the frequency domain, and the SP signal is interpolated in the time direction, and is output to the first SP frequency interpolation filter 9. The first SP frequency interpolation filter 9 is an SP signal that has been interpolated in the time direction, and then interpolated in the frequency direction, by the SP signal that is interpolated in the time direction and the frequency direction, A transmission path response corresponding to all the data is obtained.

The first time SP is inserted into the filter 8, as shown in FIG. 2, the SP signal exists in a ratio of one out of every four symbols, so the other three symbols are, for example, linearly interpolated (between SPs) The time difference is equally divided and the value is placed.

The SP frequency interpolation filter 9 of the first embodiment limits the frequency band of the SP signal to each symbol by using an optimum filter coefficient determined according to the signal quality detection result of the OFDM signal, as will be described later. The SP signal is interpolated in the frequency direction.

Here, the SP signal is a known signal whose phase or power is predetermined, and is used as a transmission path estimation symbol in order to obtain a transmission path response required for estimating transmission signal distortion.

The first equalization circuit 7 uses the transmission path estimation signal caused by the SP signal to equalize the OFDM signal in the frequency domain. The output of the first-class equalization circuit 7 is supplied to the error correction circuit 10, and the error correction processing is performed to decode the reception data.

The first coefficient switching circuit 11 that switches the filter coefficients of the first SP frequency interpolation filter 9 includes a pass band shifting portion that is set by sequentially switching the complex translation modes of FIG. 3(a) 11a and the pass band mode selecting unit 11b which is set by sequentially switching the complex numbers of FIG. 3(b) through the band mode.

The coefficient determination circuit 12 includes a second SP frequency interpolation filter 125, a second coefficient switching circuit 124, a second equalization circuit 121, a signal quality detecting circuit 122, and a control unit 123.

The second coefficient switching circuit 124 that switches the filter coefficients of the second SP frequency interpolation filter 125 includes a pass band that is set by sequentially switching the same complex mode as that of FIG. 3(a) The translating portion 124a and the pass band mode selecting unit 124b which are set in the same manner as in Fig. 3(b) by the band mode are sequentially switched.

Fig. 3 is an explanatory diagram showing an example of filter coefficient control in the first embodiment.

The first coefficient switching circuit 11 is a complex filter characteristic obtained by shifting a center frequency based on a main wave position as a reference, and a filter characteristic from which the filter has been translated. The complex filter characteristic of one of the main wave positions is partially switchable, and can be switched; it is actuated in accordance with the amount of translation supplied from the coefficient decision circuit 12 and the pass band mode.

The coefficient determination circuit 12 sequentially generates the filter coefficients (filter modes) shown in FIG. 3, and detects the modulation error ratio (hereinafter referred to as MER) of the equalized output using the interpolation of each frequency. The reception quality is determined, and the filter coefficient having the best reception quality is determined, and the translation result and the determination result of the pass band mode are supplied to the first coefficient switching circuit 11.

In addition, in FIGS. 3(a) and 3(b), the main wave and the delayed wave (and the preceding wave) on the time axis are shown (the horizontal axis represents the delay time and the vertical axis represents the power). It indicates the result of the actual detection delay profile, but the main wave with the largest signal level, for example, setting the threshold. If the actual detection exceeds the threshold, the actual detection becomes the main wave level, then it can be considered centered on the main wave position. There are pre- or delayed waves in the position before and after. Therefore, in a predetermined bandwidth including a narrow band (hereinafter referred to as a main wave band) in which a main wave exists, for example, a case where a delayed wave exists is also assumed to be imaginarily illustrated on the time axis. Since the existence of the delayed wave is easier to distinguish with respect to the main wave, it becomes a graph similar to the delayed side write, but in the embodiment, the delay side write detection is not performed at all, and the many filter modes that can be conceived are borrowed. It is set by changing the filter coefficients one by one, and the action will determine the filter mode (filter characteristic) with the best reception quality. This is also the same in FIGS. 6 and 8 which will be described later.

Regarding the main wave, among all the signal waves including the main wave, the delayed wave, and the preceding wave in the same broadcast channel, the signal wave having the highest power level is defined as the main wave.

Further, after shifting the translation mode of the predetermined bandwidth in the frequency direction as shown in FIG. 3(a), one of the predetermined bandwidths is allowed to pass through two or more passbands as shown in FIG. 3(b). The optimum filter characteristic is generated by a mode in which a passband mode having a narrow bandwidth similar to the main wave band is a complex number (two in FIG. 3(b)), and the main wave band is used. The mode in which the band mode is centered and the other overlapped band modes are successively moved away, in other words, the filter coefficients are controlled to overlap the other pass band mode from the main band of the pass band mode. The center is separated from each other to generate filter characteristics with two passbands (eg, by band mode 6). That is, an attempt is made to determine all filter modes including a mode in which a filter band of a complex narrow bandwidth is sequentially expanded one by one as a filter mode in the frequency direction by coefficient control, and it is determined that The main mode and the delayed wave pass through the filter through the frequency band to obtain a good signal quality result filter mode. This is also the same in FIGS. 6(b) and 8(b) which will be described later.

Next, the operation of the coefficient determination circuit 12 will be described with reference to Fig. 3 . 3(a) and 3(b) are explanatory views showing an example of filter coefficient control in the first embodiment. Fig. 3(a) shows the action of changing the translation amount successively to try the complex translational mode, and Fig. 3(b) shows the translation mode 1 after the translation mode 1 is selected in Fig. 3(a). Within the determined bandwidth, the pass band mode is successively changed from the subsequent pass band, and the operation until the pass band mode of the two independent pass bands is attempted.

In the coefficient determination circuit 12, the control unit 123 controls the filter characteristics of the filter modes 1 to 7 in which the center frequency shown in Fig. 3(a) is first shifted by the filter coefficient control. Produced sequentially. When the two-wave multiple path of the delay difference between the main wave and the delayed wave shown in FIG. 3 is input, when the two waves are converged in the translation mode 1 in the filter pass band, the MER on the signal quality detecting circuit 122 is the minimum. And was judged to have the best reception quality. Next, with respect to the translation mode 1, as shown in FIG. 3(b), the filter characteristics of the complex passband modes 1 to 6 for allowing the main wave and other partial bands to pass through are sequentially generated. When the two-wave multipath is as shown in Fig. 3(b), the noise removal capability of the passband mode 6 that allows only the vicinity of the main wave and the delayed wave to pass through is compared to the translation mode 1 in which the entire band is transparent. Therefore, the MER on the signal quality detecting circuit 122 is small, and finally it is determined that the receiving quality is the best.

4 is an explanatory diagram of a wide-band filter that allows a delay wave component (referred to as a long-delayed delayed wave component) having a large delay difference with respect to a main wave to be transmitted, and FIG. 5 is a view on the allowable relative An explanatory diagram of a filter of a narrow band in which a delayed wave component (referred to as a short-delay delayed wave component) having a small delay difference is transmitted through a main wave.

4(a) shows the relationship of the delayed wave having a large delay difference with respect to the main wave, and FIG. 4(b) shows the frequency of the transmission signal having the delayed wave component of the long delay as shown in FIG. 4(a). characteristic. The frequency characteristic at this time is a characteristic in which the interval between beats is short and changes with a relatively fast cycle. Therefore, in order to support such a long delay delayed wave, it is necessary to have a wide-band filter including a high frequency band. However, if a wide-band filter is used alone, there is a problem that the noise component increases.

Fig. 5(a) is a diagram showing a delayed wave component (referred to as a short delay delayed wave component) having a small delay difference with respect to the main wave, and Fig. 5(b) is a diagram showing a short delay as shown in Fig. 5(a). The frequency characteristic of the transmitted signal of the delayed wave component. The frequency characteristic at this time is a characteristic in which the interval between beats is long and varies with a slow cycle. Therefore, at this time, it can be supported by a filter corresponding to a narrow frequency band of a low frequency band.

Fig. 6 is an explanatory diagram showing another example of filter coefficient control in the first embodiment.

In the coefficient determination circuit 12, the control unit 123 firstly generates filter characteristics of the filter modes 1 to 7 in which the center frequency shown in Fig. 6(a) is translated. When the three-wave multiple path of the difference between the preceding wave, the main wave, and the delayed wave shown in FIG. 6 is input, the three waves are converged in the translation mode 4 in the filter pass band, and the signal quality detecting circuit 122 The MER is the smallest and is judged to be the best reception quality. Next, with respect to the translation mode 4, as shown in FIG. 6(b), filter characteristics of the complex passband modes 1 to 6 for allowing the main wave and other partial bands to pass through are sequentially generated. When the three-wave multipath is as shown in Fig. 6(b), only the forward wave, the main wave, and the vicinity of the delayed wave are transmitted with three passbands compared to the translation mode 4 that allows the entire band to pass through. The noise removal capability by the band mode 6 is high, so the MER on the signal quality detecting circuit 122 is small, and finally it is determined that the receiving quality is the best.

As described above, by using filter characteristics with one or a plurality of passbands in a predetermined frequency band to search for filter characteristics that have the best reception quality, even if the delay difference of the multipath wave is large, the delayed wave In the case where the filter passes through the entire band, the noise outside the band is cut off, so that the SP signal, that is, the noise of the transmission path estimation signal can be removed to improve the reception performance.

According to the first embodiment, when the multipath delay time range that can be equalized is expanded, even if the delay difference of the multiple paths is large, the delayed wave is not widened to the entire filter transmission band, and can be removed. The noise of the SP signal improves the reception performance.

[Second Embodiment]

Fig. 7 is a block diagram of an OFDM receiving apparatus according to a second embodiment. The same portions as those in the first embodiment of Fig. 1 are denoted by the same reference numerals and will not be described.

In the second embodiment of FIG. 7, the difference from the first embodiment of FIG. 1 is that the first coefficient switching circuit 11A includes the pass band shifting unit 11a and the pass band mode selecting unit 11b. The bandwidth switching unit 11c and the second coefficient switching circuit 124A which are provided by sequentially switching the plurality of bandwidths of FIG. 8(a) are provided with a passband shifting unit 124a and a passband mode selecting unit 124b. The bandwidth switching unit 124c which is set in the same manner as the complex bandwidth of FIG. 8(a) is sequentially switched. Therefore, the control unit 123A also controls the configuration of the bandwidth switching unit 11c and the bandwidth switching unit 124c. The other components are the same as those in Fig. 1.

Fig. 8 is an explanatory diagram showing an example of filter coefficient control in the second embodiment.

The first coefficient switching circuit 11A of FIG. 7 has the filter characteristics of bandwidth 1, bandwidth 2, and bandwidth 3 from the narrow bandwidth as shown in FIG. 8(a), and has the widest bandwidth 3 A complex filter characteristic in which the main wave position is a reference and the center frequency is translated. Further, with respect to the filter characteristic of the bandwidth 3, the complex filter characteristic that allows the partial band of the main wave position to be transparent is switched from among the filter characteristics that have been translated, in accordance with the bandwidth supplied from the coefficient decision circuit 12A. , the amount of translation, the action through the band mode.

The coefficient determination circuit 12A of FIG. 7 includes a second SP frequency interpolation filter 125, a second coefficient switching circuit 124A, a second equalization circuit 121, a signal quality detecting circuit 122, and a control unit 123A, and generates a map. The filter coefficient (filter mode) shown in Fig. 8 detects the reception quality from the MER using the equalized output of each frequency interpolation, determines the filter coefficient with the best reception quality, and supplies the determination result to The first coefficient switching circuit 11A.

Next, the operation of the coefficient determination circuit 12A will be described with reference to Fig. 8 .

In the coefficient determination circuit 12A, the control unit 123A firstly causes the center frequency to be shifted based on the main wave position with respect to the bandwidth 1, the bandwidth 2, and the bandwidth 3 as shown in FIG. 8(a). Complex filter characteristics. When the two-wave multipath with the delay difference shown in Fig. 8 is input, the two waves are converged in the bandwidth 3 + translation mode 1 in the filter pass band, the MER is the smallest, and it is judged that the reception quality is the best. .

Next, with respect to the bandwidth of the bandwidth 3+ translation mode 1, as shown in FIG. 8(b), the filter characteristics of the complex passband mode for allowing the main wave and other partial bands to pass through are sequentially generated. In FIG. 8(b), since the pass band below the bandwidth 2 has been determined in FIG. 8(a), only the case where the pass band exceeding the bandwidth 2 is searched is searched. When the two-wave multipath is as shown in FIG. 8, the noise removal capability of the passband mode 4 that allows only the main wave and the delayed wave to pass through is compared to the bandwidth 3+ translation mode 1 in which the entire band is transparent. It is higher, so the MER is smaller, and it is finally judged that the reception quality is the best.

In the determination of FIG. 8(a), when the multipath delay wave converges at the bandwidth 1, the bandwidth 1 is the minimum MER, and when the multipath delay wave exceeds the bandwidth 1 but the bandwidth 2, the bandwidth 2 is the minimum MER. When the filter characteristics of the bandwidth 1 or the bandwidth 2 are selected, the noise of the filter is well removed, so that it is not necessary to perform the process of searching for the partial pass band, and thus it can be omitted.

As described above, the determination is made by the filter characteristics of the complex bandwidth, and when the wideband filter is selected, the determination of the filter characteristics with 1 or a complex passband in the frequency band is performed, whereby the multipath is performed. When the delay difference is small, it is not necessary to search for all filter modes, thereby reducing power consumption. Further, even when the delay difference is large, the delay signal is not widened to the entire filter transmission band, and the noise of the SP signal can be removed to improve the reception performance.

According to the second embodiment, when the delay difference of the multiple paths is small, the amount of calculation can be reduced to suppress the power consumption, and even if the delay difference of the multiple paths is large, the delay wave is not broad enough to the entire filter pass band. In this case, the SP signal, that is, the noise of the transmission path estimation signal can be removed to improve the reception performance.

[Third embodiment]

Fig. 9 is a block diagram showing another embodiment of the coefficient determination circuit in the OFDM reception device of the third embodiment. The same portions as those of the coefficient decision circuit of Fig. 1 are denoted by the same reference numerals.

In the coefficient determination circuit 12 of FIG. 1, although the filter coefficients are sequentially switched to detect the reception quality, when the state of the reception signal such as the mobile reception or the like is changed, the difference in the reception quality is exactly It is caused by the change of the receiving status or the difference of the filter coefficients, which sometimes causes misjudgment.

The coefficient determination circuit 12B shown in FIG. 9 includes a second SP frequency interpolation filter 125, a second coefficient switching circuit 124, a second equalization circuit 121, and a first signal quality detection circuit 122. In addition to the same set of circuit sections, a third SP frequency interpolation filter 14, a third coefficient switching circuit 16, a third equalizing circuit 13, and a second signal quality detecting circuit 15 are newly provided. A group of circuits.

The third coefficient switching circuit 16 includes a pass band shifting unit 16a similar to the pass band shifting unit 124a and a pass band mode selecting unit 16b similar to the passing band mode selecting unit 124b. Therefore, the control unit 123B controls the configuration of the third coefficient switching circuit 16 in addition to the first coefficient switching circuit 11 and the second coefficient switching circuit 124 shown in FIG. The other configuration is the same as the coefficient decision circuit of Fig. 1.

In FIG. 9, the circuit components of the SP frequency interpolation filter, the coefficient switching circuit, the equalization circuit, and the signal quality detecting circuit are set in two groups, and the same received signal is based on two filter coefficients. The first and second signal quality detecting circuits 122 and 15 respectively detect the reception quality, and the control unit 123B selects the better reception quality. The optimum filter coefficients are finally determined by sequentially comparing the quality of the selected filter characteristics with the quality of the next filter characteristic.

According to the above configuration, even when the state of the received signal such as mobile reception is changed, the optimum filter coefficient can be determined. The same configuration can be applied to the OFDM receiving apparatus of the second embodiment.

[Fourth embodiment]

Fig. 10 is a block diagram showing still another embodiment of the coefficient determination circuit in the OFDM reception device of the third embodiment.

The coefficient determination circuit 12C shown in FIG. 10 is provided with a memory in each of the front stages of the second equalization circuit 121 and the second SP frequency interpolation filter 125 in the coefficient determination circuit 12 of FIG. 126 and 127. The other configuration is the same as the coefficient decision circuit of Fig. 1.

In FIG. 10, the FFT output signal and the time-interpolated SP signal are respectively held in the memories 126 and 127, and the filter coefficients are sequentially switched for the same signal to detect the reception quality, and the optimal filter is determined.

According to the above configuration, even when the state of the received signal such as mobile reception is changed, the optimum filter coefficient can be determined. The same configuration can be applied to the OFDM receiving apparatus of the second embodiment.

According to the OFDM receiving apparatus according to the embodiment of the present invention, the SP signal dispersed in the time direction and the frequency direction is interpolated by the SP signal interpolation filter in the time direction and the frequency direction, and the interpolated SP is used. When the signal is used to estimate the transmission path response necessary for equalization, the SP signal interpolation filter uses the filter characteristics of two or more passbands in a predetermined frequency band to sequentially switch the complex number through the mode. Attempts have been made to determine the passband of the filter characteristics that will optimize the quality of the reception, thereby enabling good interpolation of the SP signals. When there is a long-delayed delay wave component in the transmission signal and a filter is applied to the wide-band, the influence of the noise can be removed to improve the reception performance in the multipath.

In addition, although the several embodiments of the present invention have been described, these embodiments are merely illustrative and are not intended to limit the scope of the invention. The present invention may be embodied in various other forms, and various omissions, substitutions and changes may be made without departing from the scope of the invention. The invention or its modifications are intended to be included within the scope of the invention and the scope of the invention.

1. . . antenna

2. . . Selector

3. . . A/D conversion circuit

4. . . IQ demodulation circuit

5. . . FFT circuit

6. . . FFT window control circuit

7. . . First equal circuit

8. . . 1st SP time interpolation filter

9. . . The first SP frequency interpolation filter

10. . . Error correction circuit

11. . . First coefficient switching circuit

11a. . . Band shifting

11b. . . Band mode selection

11c. . . Bandwidth switching unit

12. . . Coefficient determination circuit

13. . . Third equalization circuit

14. . . 3rd SP frequency interpolation filter

15. . . 2nd signal quality detection circuit

16. . . Third coefficient switching circuit

100. . . OFDM receiving device

121. . . Second equalization circuit

122. . . Signal quality detection circuit

123. . . Control department

124. . . Second coefficient switching circuit

125. . . 2nd SP frequency interpolation filter

126 and 127. . . Memory

123A. . . Control department

123B. . . Control department

124a. . . Band shifting

124b. . . Band mode selection

124c. . . Bandwidth switching unit

12A. . . Coefficient determination circuit

12B. . . Coefficient determination circuit

12C. . . Coefficient determination circuit

16a. . . Band shifting

16b. . . Band mode selection

Fig. 1 is a block diagram of an OFDM reception device according to a first embodiment.

[Fig. 2] An explanatory diagram of a transmission format of an OFDM signal.

Fig. 3 is an explanatory diagram showing an example of filter coefficient control in the first embodiment.

FIG. 4 is an explanatory diagram of a wide-band filter that can correspond to a delayed-wave component of a long delay.

FIG. 5 is an explanatory diagram of a filter capable of responding to a narrow band of a short-delay delayed wave component.

Fig. 6 is an explanatory diagram showing another example of filter coefficient control in the first embodiment.

Fig. 7 is a block diagram of an OFDM receiving apparatus according to a second embodiment.

Fig. 8 is an explanatory diagram showing an example of filter coefficient control in the second embodiment.

[Fig. 9] A block diagram of another embodiment of the coefficient decision circuit.

[Fig. 10] A block diagram of still another embodiment of the coefficient decision circuit.

1. . . antenna

2. . . Selector

3. . . A/D conversion circuit

4. . . IQ demodulation circuit

5. . . FFT circuit

6. . . FFT window control circuit

7. . . First equal circuit

8. . . 1st SP time interpolation filter

9. . . The first SP frequency interpolation filter

10. . . Error correction circuit

11. . . First coefficient switching circuit

11a. . . Band shifting

11b. . . Band mode selection

12. . . Coefficient determination circuit

100. . . OFDM receiving device

121. . . Second equalization circuit

122. . . Signal quality detection circuit

123. . . Control department

124. . . Second coefficient switching circuit

124a. . . Band shifting

124b. . . Band mode selection

125. . . 2nd SP frequency interpolation filter

Claims (8)

An OFDM receiving apparatus characterized by comprising: a filter unit that limits a channel estimation signal in a frequency direction using a complex filter characteristic; and an equalization unit that uses an output of a pre-filter unit The reception signal is equalized; and the quality detection department detects the reception quality of the output of the pre-processing unit; and the determination unit uses the detected reception quality to record the complex filter characteristics from the foregoing. The optimum filter characteristics are determined; the pre-complex filter characteristics have: a filter characteristic of a predetermined bandwidth, and a complex filter characteristic that allows a portion of the bandwidth defined by the preamble to pass through; Contains filter characteristics with two or more passbands. The OFDM receiving apparatus according to claim 1, wherein the pre-complex filter characteristic includes a pass band of the main wave and at least one pass band other than the predetermined bandwidth. The OFDM receiving apparatus according to claim 1 or 2, wherein the pre-complex filter characteristic has a complex filter characteristic having a different center frequency in a predetermined bandwidth, and each of different characteristics for a preamble center frequency. The filter characteristics are partially transparent to the complex filter characteristics; the complex filter characteristics of the pre-recorded partial pass include filter characteristics with two or more passbands; the pre-determination section is a filter from the complex center frequency Among the characteristics, the optimal filter characteristics are determined, and the optimal filter is determined from the next determined filter characteristics and the complex filter characteristics that partially pass through one of the determined filter characteristics. characteristic. The OFDM receiving apparatus according to claim 1 or 2, wherein the pre-complex filter characteristic has a complex filter characteristic having a different bandwidth and a center frequency, and a predetermined bandwidth among the complex multi-bandwidths. The filter characteristics of the above bandwidth allow a part of the bandwidth to pass through the complex filter characteristics; the complex filter characteristics of the pre-recorded partial pass include filter characteristics with two or more passbands; The filter characteristics of the optimal bandwidth are determined from the characteristics of the complex filter having different bandwidth and center frequency, and the filter characteristics are determined when the filter characteristics of the predetermined bandwidth are determined. The optimum filter characteristics are determined among the complex filter characteristics that partially pass through one of the determined filter characteristics. The OFDM receiving apparatus according to the first or second aspect of the invention, wherein the pre-determination determining unit is configured to: set the multi-translation mode by sequentially switching the band shifting unit; and pass the band mode The selection unit is set in the bandwidth in any translation mode of the complex translation mode, and the complex number is sequentially switched by the band mode. The OFDM receiving apparatus according to claim 3, wherein the pre-complex filter characteristic has a complex filter characteristic having a different bandwidth and a center frequency, and a bandwidth of a predetermined bandwidth or more among the complex bandwidths. a filter filter characteristic that allows a part of the bandwidth to be transparent to the complex filter characteristics; the complex filter characteristic of the pre-recorded partial pass contains filter characteristics with two or more passbands; the pre-determination section is from the bandwidth and Among the complex filter characteristics with different center frequencies, the filter characteristics of the optimal bandwidth are determined, and when the filter characteristics of the predetermined bandwidth are determined, the filter characteristics have been determined, and Among the complex filter characteristics in which one of the determined filter characteristics is partially transparent, the optimum filter characteristics are determined. The OFDM receiving apparatus according to claim 3, wherein the pre-determination determining unit is configured to: the pass band shifting unit is configured to sequentially switch between the plurality of translation modes; and the pass band mode selecting unit Within the bandwidth of any translational mode of the complex-translational mode, the complex number is set by sequential switching of the band modes. The OFDM receiving apparatus according to claim 4, wherein the pre-determination unit is configured to: set a multi-translation mode by sequentially switching the band shifting unit; and pass the band mode selecting unit. Within the bandwidth of any translational mode of the complex-translational mode, the complex number is set by sequential switching of the band modes.