Reception and equalisation of multicarrier signals

[0001] The present invention relates to an OFDM receiver and a data demodulation method for receiving a transmission signal by an OFDM (Orthogonal Frequency Division Multiplex) modulation method, and in particular, FFT in OFDM demodulation. (Fast Fourier transform) Related to window position optimization technology.

PROBLEM TO BE SOLVED: To put into practical use a digital transmission method using a transmission signal by an OFDM modulation method, particularly in the field of terrestrial digital broadcasting. In terrestrial digital broadcasting, broadcasting by a single frequency network is being studied by utilizing the feature of the OFDM modulation method that is resistant to multipath interference. In this case, multipath interference with a very long delay time occurs, so it is necessary to accurately control the window position of the FFT in OFDM demodulation.

[0003] On the other hand, the applicant has proposed a technique for controlling the FFT window position using the S / N value (dispersion value) of the demodulated signal (see Patent Document 1). According to the technique described in Patent Document 1, the window position control of the FFT in OFDM demodulation is accurately performed even in the presence of multipath interference having a long delay time such as when a single frequency network is implemented. Can be done.

[0004] FIG. 7 is a schematic block diagram showing a typical configuration example of an OFDM receiver including an FFT window position control unit, and FIG. 8 is a schematic block diagram of an OFDM signal received by the OFDM receiver shown in FIG. 7. It is a figure for demonstrating a format example.

As shown in FIG. 7, the OFDM signal received by the antenna 111 is input to the tuner 112, and the tuner 112 selects the OFDM signal of a predetermined channel and converts it into an IF (intermediate frequency) band. The output of the tuner 112 is converted into a digital signal by the analog / digital converter (A / D converter) 113.

[0006] The output of the A / D converter 113 is converted into a complex baseband signal by the IQ demodulation unit 114 and supplied to the FFT (Fast Fourier Transform) unit 115. The FFT unit 115 performs an FFT (Fast Fourier Transform) operation based on the FFT window, and converts the complex baseband signal from the data on the time axis to the data on the frequency axis. That is, the output of the FFT unit 115 has a signal arrangement as shown in FIG. 8, and is supplied to the equalization unit 116.

[0007] Further, in the output of the FFT unit 115, the distributed pilot (SP) signal 4 shown in FIG. 8 is interpolated in the time direction and the frequency direction by the SP memory 121 and the interpolation unit 122. The equalization unit 116 estimates the transmission line response at all times and all frequencies using the SP signal 4 interpolated by the interpolation unit 122, and equalizes the amplitude of the information symbol 1 by a demodulation method according to the transmission line response. And phase equalization. The output of the equalization unit 116 is supplied to the error correction unit 117, and the error correction unit 117 corrects the error correction decoding process, that is, the error generated during transmission and outputs it as received data.

[0008] Further, in the output of the FFT unit 115, the additional information (TMCC / AC) signal 2 and the continuous pilot (CP) signal 3 are continuously arranged at specific frequencies as shown in FIG. Since it is BPSK modulated, it can be equalized by the equalization unit 124 with reference to the signal one symbol before, which is the output of the one symbol delay unit 123. The output of the equalization unit 124 is supplied to the AC / TMCC detection unit 125, and the TMCC / AC signal 2 is detected / decoded by the TMCC detection unit 125 and output.

[0009] Further, the output of the equalization unit 124 is branched and supplied to the S / N detection unit 127, and the received S / N value is detected by obtaining and averaging the variance from the BPSK reference signal point.

The output of the S / N detection unit 127 is supplied to the FFT window control unit 128, and the FFT window control unit 128 sets the optimum FFT window position based on the received S / N value. For example, when a multipath interference wave with a long delay time as shown in FIG. 9 is received, it can be demolished at the FFT window position shown in FIG. 9 (a) without intersymbol interference due to the delay wave. At the FFT window position shown in b), the received S / N deteriorates due to intersymbol interference due to delayed waves. Therefore, the FFT window control unit 128 compares the received S / N values when the FFT window position is changed, and sets the FFT window position at the position where the received S / N value is the best.

[Patent Document 1] Japanese Unexamined Patent Publication No. 2001-345775 [0012] [Problems to be Solved by the Invention] As described above, in the OFDM receiving device illustrated in FIG. 6, the signal one symbol before is transmitted. As a reference, BPSK-modulated TMCC / AC carrier 2 and CP carrier 3 are equalized, and the received S / N value is detected from this equalized output. The detection of the S / N value using the BPSK carrier has an advantage that the detection range is wider than the case of detecting the S / N value using the equalized output of the information data 1.

However, as in the example shown in FIG. 9B, if the FFT window position shifts, the delay time of both the main wave and the delay wave increases in the output of the FFT unit 115, so that the symbol In addition to deterioration due to inter-interference, an error occurs in the interpolation of the SP signal 4 in the interpolation unit 122. However, since the S / N detection unit 127 cannot detect the interpolation error of the SP signal 4, it cannot detect the received S / N value including the deterioration due to the interpolation error of the SP signal 4, and as a result, the FFT window control unit 128 cannot detect the reception S / N value. There is a problem that the detection accuracy of the FFT window position deteriorates.

[0014] The present invention has been made in view of the above problems, and even if an interpolation error of the distributed pilot signal occurs, the received S / N value including the influence of deterioration due to the interpolation error can be detected. It is an object of the present invention to provide an OFDM receiving device and a data demodulation method capable of accurately detecting the optimum value of the FFT window position based on the detected received S / N value.

[Means for Solving the Problems] In order to achieve the above object, the OFDM receiving device according to the present invention comprises an additional information signal transmitted at a predetermined frequency and a continuous pilot signal transmitted at a predetermined frequency. In a device for receiving an OFDM (Orthogonal Frequency Divided Multiplex) signal including either one or both and a distributed pilot signal distributed and transmitted in the frequency direction and the time direction, (a) the received OFDM signal is input. A fast Fourier transform unit that performs a fast Fourier transform based on the FFT window that defines the range on the time axis to perform a fast Fourier transform and converts the data on the time axis to the data on the frequency axis, and (b) fast Fourier transform. Either or both of the interpolation unit that interpolates the distributed pilot signal output from the conversion unit and (c) the additional information signal and continuous pilot signal output from the fast Fourier transform unit were interpolated and output from the interpolation unit. An equalization unit that equalizes based on the distributed pilot signal, (d) a reception quality signal detection unit that detects a reception quality signal indicating reception quality using the equalization output of the equalization unit, and (e) a reception quality signal. It is characterized by including an FFT window control unit that controls the position of the FFT window so that the reception quality is improved based on the reception quality signal detected by the detection unit.

[0016] Further, in the data demodulation method according to the present invention, one or both of an additional information signal transmitted at a predetermined frequency and a continuous pilot signal transmitted at a predetermined frequency are dispersed in the frequency direction and the time direction. A data demodulation method used in a device for receiving an OFDM signal including a distributed pilot signal transmitted by (a) defining a range on the time axis in which the received OFDM signal is input and a fast Fourier transform is performed. A step of performing a fast Fourier transform based on the FFT window to convert data on the time axis to data on the frequency axis, and (b) a step of interpolating the distributed pilot signal output from the fast Fourier transform unit, and ( c) The stage of equalizing either or both of the additional information signal output from the fast Fourier transform unit and the continuous pilot signal with reference to the distributed pilot signal interpolated and output from the interpolation unit, and (d), etc. The stage of detecting the reception quality signal indicating the reception quality using the equalized output of the equalization unit, and (e) the position of the FFT window so that the reception quality is improved based on the reception quality signal detected by the reception quality signal detection unit. It is characterized by including a step of controlling.

That is, the additional information signal and the continuous pilot signal output from the fast Fourier transform unit are equalized with reference to the interpolated output of the distributed pilot signal which is the equalization reference signal of the information symbol, and the dispersion of the equalized output is performed. Since the reception quality signal is detected from, even if an interpolation error of the distributed pilot signal occurs, the reception quality signal including the influence of deterioration due to the interpolation error can be detected, and the detected reception quality signal can be used to detect the FFT window position. The optimum value can be detected with high accuracy.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0019] In the drawings, the same or equivalent parts and components are designated by the same or equivalent reference numerals, and the description thereof will be omitted or simplified.

[0020] The OFDM receiving device in each of the following examples will be described as receiving the OFDM signal of the signal format illustrated in FIG. 8, but the signal format is not limited to this.

[0021] In FIG. 8, the information symbol 1 transmits information data such as video and audio, and is modulated by, for example, 64QAM. Additional information (TMCC: Transmission and Multiplexing Configuration Control / AC: Auxiliary Channel) signal 2 transmits transmission parameter information such as modulation method and interleaving, and additional information, and is differential BPSK (Binary Phase Shift keying). : Two-phase phase modulation) is transmitted on a specific carrier (frequency slot). The continuous pilot (CP) signal 3 is an unmodulated signal transmitted by a specific carrier (frequency slot). The distributed pilot (SP: Scattered Pilot) signal 4 is an unmodulated signal that is distributed and transmitted in the frequency and time directions, and is used for transmission line characteristic estimation and synchronous reproduction in a receiving device.

[First Example] FIG. 1 is a schematic block diagram showing a configuration example of an OFDM receiving device in the first embodiment. The OFDM receiving device in the first embodiment inputs the received OFDM signal, performs the fast Fourier transform based on the FFT window that defines the range on the time axis for performing the fast Fourier transform, and performs the fast Fourier transform from the data on the time axis. The FFT (Fast Fourier Transform) unit 15 that converts data on the frequency axis, the interpolation unit 22 that interpolates the distributed pilot (SP) signal 4 output from the FFT unit 15, and the additional information output from the FFT unit 15 ( The equalization unit 26a, the equalization unit 26a, etc. that equalize the AC / TMCC) signal 2 and the continuous pilot (CP) signal 3 with reference to the distributed pilot (SP) signal 4 interpolated and output from the interpolation unit 22. The S / N detection unit (reception quality signal detection unit) 27a that detects the reception S / N value (reception quality signal) indicating the reception quality using the transform output, and the reception S / N detected by the S / N detection unit 27a. It is provided with an FFT window control unit 28 or the like that controls the position of the FFT window so that the reception quality is improved based on the value.

As shown in FIG. 1, the OFDM signal received by the antenna 11 is input to the tuner 12, and the OFDM signal of a predetermined channel is selected by the tuner 12 and converted into an IF (intermediate frequency) band. The output of the tuner 12 is converted into a digital signal by the analog / digital converter (A / D converter) 13. The output of the A / D converter 13 is supplied to the IQ demodulation unit 14, is quasi-synchronously orthogonally detected, and is converted into a complex baseband signal. The output of the IQ demodulation unit 14 is supplied to the FFT (Fast Fourier Transfer) unit 15.

[0024] The FFT unit 15 performs a fast Fourier transform operation based on the FFT window that defines the range on the time axis for performing the fast Fourier transform, and changes the complex baseband signal from the data on the time axis to the data on the frequency axis. Convert. That is, the output of the FFT unit 15 has a signal arrangement as shown in FIG. 8, and the output of the FFT unit 15 is supplied to the equalization unit 16.

[0025] In the output of the FFT unit 15, the distributed pilot (SP) signal 4, which is the equalization reference signal of the information symbol 1, is stored in the SP memory 21 for a predetermined number of symbols, and is stored in the SP memory 21 for a predetermined number of symbols. It is filtered in the direction and the frequency direction and interpolated so as to have the desired discrete arrangement.

[0026] The equalization unit 16 estimates the transmission line response at all times and all frequencies using the SP signal 4 interpolated and output by the interpolation unit 22, and the information symbol 1 is demodulated according to the transmission line response. Amplitude equalization and phase equalization are performed. The output of the equalization unit 16 is supplied to the error correction unit 17, and the error correction unit 17 corrects the error correction decoding process, that is, the error generated during transmission and outputs it as received data.

[0027] In the output of the FFT unit 15, the additional information (TMCC / AC) signal 2 is supplied to the delay detection unit 33a including the one-symbol delay unit 23a and the equalization unit 24a. As shown in FIG. 8, the additional information (TMCC / AC) signal 2 is continuously arranged at a specific frequency and is BPSK-modulated, so that the additional information (TMCC / AC) signal 2 is added one symbol before the output of the one-symbol delay unit 23a. Based on the information (TMCC / AC) signal 2, it is equalized by the equalization unit 24a. The output of the equalization unit 24a is supplied to the AC / TMCC detection unit 25a, decoded, and output as TMCC data and AC data. The output TMCC data is supplied to each part of the receiving device and used for setting carrier modulation parameters, error correction parameters, etc. in each part of the receiving device.

[0028] In the output of the FFT unit 15, the additional information (TMCC / AC) signal 2 and the continuous pilot (CP) signal 3 are used as a reference by using the SP signal 4 interpolated and output by the interpolation unit 22. It is equalized by the conversion part 26a. The additional information (TMCC / AC) signal 2 is modulated by the differential BPSK in order to simplify the demodulation processing of the receiving device, and is originally equalized by the signal one symbol before. However, as shown in FIG. 1, the signal point of BPSK can be demodulated even if the TMCC / AC signal 2 and the CP signal 3 are equalized by using the interpolated output of the SP signal 4 which is the equalization reference signal of the information symbol 1. Therefore, it is possible to detect the received S / N using this equalized output. The equalization output of the equalization unit 26a is supplied to the S / N detection unit 27a.

[0029] The S / N detection unit 27a uses the dispersion detection unit 31 and the averaging unit 32 as illustrated in FIG. 2 to obtain a predetermined reference signal point (for example, a BPSK reference signal point) for the equalization output of the equalization unit 26a. ), And the detected dispersion values are averaged in either one or both directions of the frequency direction and the time axis direction, and the S / N value (reception quality signal) indicating the reception quality of the received signal. To generate.

[0030] More specifically, for the TMCC carrier and the AC carrier, the dispersion detection unit 31 determines the equalization output to obtain the reference signal point of the BPSK, and then obtains the equalization output I signal and the reference I. Obtain the squared value (I variance value) of the difference from the signal and the squared value (Q variance value) of the difference between the equalized output Q signal and the reference Q signal. For CP carriers, the squared value of the difference between the equalized output I signal and the known reference I signal (I variance value) and the squared value of the difference between the equalized output Q signal and the known reference Q signal (Q). Dispersion value) is calculated.

The output (I dispersion value and Q dispersion value) of the dispersion detection unit 31 is supplied to the average unit 32. The averaging unit 32 averages the I-dispersion value and the Q-dispersion value of each of the TMCC carrier, AC carrier, and CP carrier supplied serially in the frequency direction (between multiple carriers) and the time direction (between multiple symbols) and receives them. Output as the S / N value (dispersion value) of the signal. In the mean section 32, the mean value based on the I variance value and the mean value based on the Q variance value may be combined to form the S / N value, only the mean value based on the I variance value, or only the mean value based on the Q variance value. May be used as the S / N value.

The S / N value, which is the output of the S / N detection unit 27a, is supplied to the FFT window control unit 28, and can also be used as a monitor for adjusting the antenna 11, for example.

Returning to FIG. 1, the FFT window control unit 28 compares the optimum FFT window position, that is, the received S / N value when the FFT window position is changed, based on the received S / N value. Then, set the FFT window position at the position where the received S / N value is the best. Then, the FFT unit 15 performs the FFT (Fast Fourier Transform) operation based on the set FFT window position.

[0034] With the above configuration, in the OFDM receiving device according to the first embodiment, the additional information (TMCC / AC) signal 2 and the continuous pilot (CP) signal 3 among the outputs of the FFT unit 15 are set to the information symbol 1 and the like. The distributed pilot (SP) signal 4 is equalized based on the interpolated output of the standardized signal, and the S / N value (reception quality signal) is detected from the dispersion of the equalized output. SP) Even if an interpolation error of signal 4 occurs, the S / N value including the influence of deterioration due to the interpolation error can be detected, and the optimum value of the FFT window position can be detected accurately from the detected S / N value. ..

Further, using data having a multi-level modulation level lower than that of the information symbol 1 (64QAM), that is, TMCC / AC carrier 2 and CP carrier 3 (differential BPSK), the S / N value (dispersion value) of the received signal is used. ) Is being detected. Therefore, a wide range of S / N values can be detected. Moreover, since the average of the dispersion of a plurality of carriers (TMCC / AC carrier 2, CP carrier 3) dispersed in the transmission band is calculated, the S / N value corresponding to the reception quality of the entire reception data can be detected.

[Second Example] FIG. 3 is a schematic block diagram showing a configuration example of the OFDM receiving device in the second embodiment.

[0037] In the first embodiment, of the output of the FFT unit 15, the additional information (TMCC / AC) signal 2 is supplied to the delay detection unit 33a and equalized with reference to the TMCC / AC signal 2 one symbol before. Although an example of supplying the AC / TMCC detection unit 25a is shown, the TMCC signal of the additional information (TMCC / AC) signal 2 needs to be decoded because it is used for parameter setting of each part of the receiving device. The AC signal does not necessarily need to be decoded because it may not be used in a normal receiving device.

Therefore, as shown in FIG. 3, in the OFDM receiving device of the second embodiment, only the TMCC signal used for parameter setting or the like is used among the additional information (TMCC / AC) signals 2 output from the FFT unit 15. , Delayed detection is performed by the delayed detection unit 33b, and this detection output is decoded by the TMCC detection unit 25b and output as TMCC data.

[0039] The equalization unit 26b includes an AC signal excluding the TMCC signal for delayed detection from the additional information (TMCC / AC) signal 2 output from the FFT unit 15 and a continuous pilot (TMCC / AC) output from the FFT unit 15. The CP) signal 3 is equalized with reference to the distributed pilot (SP) signal 4 interpolated and output from the interpolation unit 22. Then, the reception S / N detection unit 27b uses the detection output of the delay detection unit 33b in addition to the equalization output of the equalization unit 26b to obtain and average the variance from the BPSK reference signal point, thereby receiving S. Detect the / N value.

[0040] As described above, the reception S / N detection unit 27b in the OFDM receiving device of the second embodiment is the TMCC required for parameter setting of the additional information (TMCC / AC) signal 2 output from the FFT unit 15. For the signal, the detection output by the delay detection unit 33b was used, and the CP signal and AC signal 3 of the additional information (TMCC / AC) signal 2 that do not require data decoding were based on the equalized output of the SP signal 4. The received S / N is detected using the equalized output. According to such a configuration, deterioration of the receiving S / N due to the deviation of the FFT window position can be detected more accurately than in the conventional case, and the calculation of the equalization process is performed as compared with the OFDM receiving device in the first embodiment. The amount can be reduced.

[Third Example] FIG. 4 is a schematic block diagram showing a configuration example of the OFDM receiving device in the second embodiment.

[0042] In the first embodiment, of the outputs of the FFT unit 15, the additional information (TMCC / AC) signal 2 and the continuous pilot (CP) signal 3 are referred to the interpolated distributed pilot (SP) signal 4. An example is shown in which the equalization unit 26a equalizes the signal, and the S / N detection unit 27a detects the S / N value (reception quality signal) from the variance of the equalized output.

On the other hand, as shown in FIG. 4, the equalization unit 26c in the OFDM receiving device of the third embodiment has a continuous pilot (CP) signal 3, additional information (TMCC / AC) output from the FFT unit 15. ) In addition to the signal 2, the distributed pilot (SP) signal 4 output from the FFT unit 15 is equalized with reference to the distributed pilot (SP) signal 4 interpolated and output from the interpolation unit 22. Then, the S / N detection unit 27c detects the S / N value (reception quality signal) from the variance of the output of the equalization unit 26c.

[0044] As described above, in the OFDM receiving device of the third embodiment, not only the TMCC / AC signal 2 and the SP signal 4 output from the FFT unit 15 but also the SP signal 4 which is the output of the FFT unit 15 is interpolated. The received S / N value is calculated using the result of equalization based on the SP signal 4 of. If there is no interpolation error in the SP signal 4, the variance of the SP signal 4 after equalization by the equalization unit 26c is almost "0", but if there is an interpolation error in the SP signal 4, the equalization unit 26c An error also occurs in the SP signal 4 after equalization by. Therefore, by detecting the received S / N using the equalized output of the SP signal 4, the received S / N due to the deviation of the FFT window position is compared with the OFDM receiving devices illustrated in the first embodiment and the second embodiment. Deterioration of N can be detected with higher accuracy.

[Other Examples] Although the first to third embodiments have been described in detail above, the present invention is carried out in various other forms without departing from the spirit or main characteristics thereof. can do.

[0046] For example, the OFDM receiving device illustrated in FIG. 5 is a modification of the OFDM receiving device illustrated in the second embodiment, and delay detection of the additional information (TMCC / AC) signal 2 output from the FFT unit 15. Delay detection is performed in unit 33a, and this detection output is decoded by TMCC detection unit 25b and output as TMCC data. Then, the equalization unit 26d equalizes only the continuous pilot (CP) signal 3 output from the FFT unit 15 with reference to the distributed pilot (SP) signal 4 interpolated and output from the interpolation unit 22. The receiving S / N detection unit 27d uses the equalization output of the CP signal 3 of the equalization unit 26d and the detection output of the TMCC / AC signal 2 by the delay detection unit 33a to obtain the variance from the BPSK reference signal point. It is also possible to detect the received S / N value by averaging the signals.

Further, in each of the OFDM receiving devices exemplified in the first to second embodiments, the received S / N value is detected by using the continuous pilot (CP) signal 3 and the additional information (TMCC / AC) signal 2. However, it is also possible to detect the received S / N value by using only some of these signals.

[0048] For example, in the OFDM receiving device illustrated in FIG. 6, the equalizing unit 26e interpolates and outputs only the additional information (TMCC / AC) signal 2 output from the FFT unit 15 as a distributed pilot. (SP) Equalize with reference to signal 4. Then, the receiving S / N detection unit 27d obtains the variance from the BPSK reference signal point and averages the received S / N value by using the equalized output of the TMCC / AC signal 2 of the equalizing unit 26d. It can also be configured to detect.

Further, in the third embodiment illustrated in FIG. 4, an example in which the SP signal 4 is further added to the TMCC / AC signal 2 and the CP signal 3 as inputs to the equalization unit 26c is shown in FIG. Although the example configured based on the OFDM receiving device of the first embodiment of 1 is shown, the configuration may be based on the OFDM receiving device of the second embodiment of FIG.

[0050] Furthermore, a part or all of each component of the OFDM receiving device shown in each of the above embodiments can be implemented by computer software.

[0051] As described above, each of the above-described embodiments is merely an example in all respects and should not be construed in a limited manner. The scope of the present invention is shown by the scope of claims and is not bound by the text of the specification. Furthermore, all modifications and modifications that fall within the equivalent scope of the claims are within the scope of the present invention.

[Effect of the Invention] According to the present invention, the received S / N value including the influence of deterioration due to the interpolation error of the distributed pilot signal can be detected, and the optimum value of the FFT window position can be determined by the detected received S / N value. It is possible to provide an OFDM receiver and a data demodulation method that can be detected with high accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS [Fig. 1] Fig. 1 is a schematic block diagram showing a configuration example of an OFDM receiver in the first embodiment.

FIG. 2 is a schematic block diagram showing a configuration example of an equalization unit for TMCC / AC signals and CP signals in the OFDM receiving device shown in FIG.

FIG. 3 is a schematic block diagram showing a configuration example of an OFDM receiving device in a second embodiment.

FIG. 4 is a schematic block diagram showing a configuration example of an OFDM receiving device according to a third embodiment.

FIG. 5 is a schematic block diagram showing a configuration example of an OFDM receiving device in another embodiment.

FIG. 6 is a schematic block diagram showing a configuration example of another OFDM receiver in another embodiment.

FIG. 7 is a schematic block diagram showing a configuration example of a typical OFDM receiver.

FIG. 8 is a schematic diagram showing a format example of a transmission signal by the OFDM modulation method.

FIG. 9 is an explanatory diagram for explaining the deviation of the FFT window position when a multipath interference wave having a long delay time is received.

[Code description] 1 ... Information symbol 2 ... Additional information (AC / TMCC) signal 3 ... Continuous pilot (CP) signal 4 ... Distributed pilot (SP) signal 11 ... Antenna 12. .. Tuner 13 ... A / D converter 14 ... IQ demodulator 15 ... FFT section 16 ... equalization section 17 ... error correction section 21 ... SP memory 22 ... interpolation Part 23a ... 1 Symbol delay part 24a ... Equalization part 25a ... AC / TMCC detection part 25b ... TMCC detection part 26a, 26b, 26c, 26d, 26e ... Equalization part 27a, 27b , 27c, 27d ... Receive S / N detection unit 28 ... FFT window control unit 31 ... Dispersion detection unit 32 ... Average unit 33a, 33b ... Delay detection unit 111 ... Antenna 112. .. Tuner 113 ... A / D converter 114 ... IQ demodulator 115 ... FFT section 116 ... equalization section 117 ... error correction section 121 ... SP memory 122 ... interpolation Part 123 ... 1 Symbol delay part 124 ... Equalization part 125 ... AC / TMCC detection part 127 ... Receive S / N detection part 128 ... FFT window control part