JP2010268274A - Semiconductor integrated circuit and reception signal processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To precisely calculate a Doppler frequency. <P>SOLUTION: An inverse Fourier transforming unit 12 calculates a first impulse response from a pilot signal, and an inverse Fourier transforming unit 21 calculates a second impulse response from a transmission line response value found from a data signal, and the pilot signal. When a multipath decision unit 24 decides a multipath which is equal to or longer than a predetermined length in the second impulse response, a main wave position specifying unit 25 specifies a main wave position in the first impulse response based upon the position of a maximum value of the second impulse response. A phase difference correction unit 16 corrects a phase difference due to a difference in frequency of the pilot signal between symbols based upon a delay amount between the main wave position and a Fourier transform window position. A phase deviation calculation unit 17 calculates a phase rotation amount between the corrected first impulse response and a first impulse response of a different symbol, and a Doppler frequency calculation unit 18 calculates a Doppler frequency based upon the phase rotation amount. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a semiconductor integrated circuit and a received signal processing method.

In digital terrestrial broadcasting, demodulation processing is performed in consideration of the influence of Doppler shift in which the carrier frequency shifts during mobile reception.
SP (Scattered Pilot) signals, which are pilot signals, are inserted at regular intervals in OFDM (Orthogonal Frequency Division Multiplexing) frames of the terrestrial digital broadcasting standard ISDB-T (Integrated Services Digital Broadcasting-Terrestrial). Conventionally, a technique for estimating a frequency (Doppler frequency) added to a carrier frequency by mobile reception using a pilot signal extracted from a received signal after Fourier transform is known.

JP 2004-274722 A JP 2005-286636 A

Mikawa et al., “Highly accurate Doppler frequency estimation method suitable for OFDM”, IEICE General Conference, B-5-77, P564, 2004

However, conventionally, there has been a problem that the Doppler frequency cannot be accurately obtained from the pilot signal.
In view of the above points, an object of the present invention is to provide a semiconductor integrated circuit and a received signal processing method capable of accurately obtaining a Doppler frequency.

In order to achieve the above object, the following semiconductor integrated circuit is provided.
The semiconductor integrated circuit includes: a first inverse Fourier transform unit that calculates a first impulse response by performing inverse Fourier transform on a pilot signal included in a received signal after Fourier transform; and a data signal included in the received signal. Based on the second inverse Fourier transform unit that calculates a second impulse response by performing inverse Fourier transform on the obtained transmission path response value and the pilot signal, and based on the second impulse response. A multipath determination unit that determines whether or not a multipath longer than the predetermined length has occurred, and when the occurrence of the multipath longer than the predetermined length is detected, the maximum value of the second impulse response Based on the position of the first wave, the main wave position specifying unit for specifying the main wave position in the first impulse response and the first impulse response specifying the main wave position are used to Alternatively, a phase difference correction unit that corrects a phase difference of the first impulse response caused by a difference in frequency of the pilot signal between symbols based on a delay amount with respect to a delayed wave, and the phase difference correction unit A phase deviation calculation unit that calculates a phase rotation amount between the first impulse response corrected by the above and the first impulse response in a different symbol, and calculates a Doppler frequency based on the phase rotation amount A Doppler frequency calculation unit.

  According to the disclosed semiconductor integrated circuit and received signal processing method, the Doppler frequency can be obtained with high accuracy.

It is a figure which shows the structure of the principal part of the semiconductor integrated circuit of this Embodiment. It is a figure which shows the structure of the OFDM frame in terrestrial digital broadcasting. It is a figure which shows an example of an impulse response. It is a figure which shows an example of the phase difference of the impulse response between different symbols. It is a figure which shows the example of the calculated amount of phase rotations. It is a figure which shows a mode that an impulse response turns back. It is a figure which shows a mode that a main wave position is specified. It is a flowchart which shows the received signal processing method by the semiconductor integrated circuit of this Embodiment. It is a figure which shows the schematic structure of the principal part of an OFDM receiving system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments as aspects of a semiconductor integrated circuit and a received signal processing method of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing a configuration of a main part of the semiconductor integrated circuit according to the present embodiment.

The semiconductor integrated circuit 10 is, for example, an LSI (Large Scale Integrated circuit) for demodulating OFDM signals for digital terrestrial broadcasting.
The semiconductor integrated circuit 10 includes a pilot signal storage unit 11, an inverse Fourier transform unit 12, an impulse response holding unit 13, an impulse response delay unit 14, a maximum value position detection unit 15, a phase difference correction unit 16, and a phase difference correction unit 16. A deviation calculating unit 17 and a Doppler frequency calculating unit 18 are provided.

  In addition, the semiconductor integrated circuit 10 includes a subcarrier group storage unit 19, a transmission path response value generation unit 20, an inverse Fourier transform unit 21, an impulse response holding unit 22, a maximum value position detection unit 23, and a multipath determination. Part 24 and a main wave position specifying part 25.

The pilot signal storage unit 11 holds a pilot signal among subcarrier groups included in a received signal after Fourier transform (for example, FFT (Fast Fourier Transform)).
FIG. 2 is a diagram showing a configuration of an OFDM frame in digital terrestrial broadcasting.

  The horizontal axis is the subcarrier number and represents the frequency direction. The vertical axis is the symbol number and represents the time direction. In the figure, black circles are SP signals Ds that are pilot signals, and white circles are data signals Da.

  The SP signal Ds, which is a pilot signal used in terrestrial digital broadcasting, is inserted every 12 carriers in the frequency direction and every 4 symbols in the time direction.

  The inverse Fourier transform unit 12 calculates an impulse response by performing an inverse Fourier transform (for example, IFFT (Inverse FFT)) on the pilot signal held in the pilot signal storage unit 11.

FIG. 3 is a diagram illustrating an example of an impulse response.
FIG. 3A shows an example of an impulse response in the (n−2) th symbol, and FIG. 3 (B) shows an example of an impulse response in the nth symbol. In FIG. 3, the horizontal axis represents time, and the vertical axis represents power.

The impulse response obtained here is called a delay profile because it indicates the multipath response of the transmission path.
When mobile reception is performed, phase rotation occurs due to fading, and impulse responses obtained between different symbols have different values. The amount of phase rotation at this time is proportional to the Doppler frequency received by the carrier wave. Therefore, the Doppler frequency can be calculated from the phase rotation amount of the impulse response between symbols in a certain period.

FIG. 4 is a diagram illustrating an example of a phase difference of an impulse response between different symbols.
Here, the maximum value I _n-2 of the impulse response of (n-2) th symbol, indicates the phase difference between the maximum value I _n of the impulse response of the n th symbol. In FIG. 4, ΔΘ indicates the amount of phase rotation due to fading. Furthermore, when the frequency of the SP signal is shifted for each symbol as shown in FIG. 2, a phase difference ΔΦ due to the difference in the frequency of the SP signal is added. Therefore, a maximum value I _n-2 of the impulse response, the phase difference between the maximum value I _n of the impulse response becomes .DELTA..theta + .DELTA..PHI.

  The impulse response holding unit 13 is, for example, a memory, holds the impulse response calculated by the inverse Fourier transform unit 12, and outputs the impulse response to the impulse response delay unit 14. Further, the impulse response holding unit 13 sends the impulse response to the maximum value position detecting unit 15, inputs the position of the maximum value of the impulse response detected by the maximum value position detecting unit 15, and sets the maximum value of the impulse response to the phase. Output to the deviation calculator 17.

  The impulse response delay unit 14 is, for example, a memory, and holds and delays the impulse response output from the impulse response holding unit 13. The impulse response delay unit 14 acquires the position of the maximum value of the input impulse response from the maximum value position detection unit 15 and holds it.

  The maximum value position detection unit 15 detects the position of the maximum value (maximum power) of the impulse response held by the impulse response holding unit 13 and outputs it to the impulse response holding unit 13 and the impulse response delay unit 14. The one with the highest power is likely to be the main wave with the best C / N ratio (Carrier to Noise Ratio).

  The phase difference correction unit 16 corrects the phase difference ΔΦ due to the difference in the frequency of the SP signal between symbols as shown in FIG. 4 with respect to the maximum value of the impulse response output from the impulse response delay unit 14. The phase difference ΔΦ is a value corresponding to the amount of delay between the preceding wave (or delayed wave) and the main wave.

The phase difference correction unit 16 calculates the phase difference ΔΦ according to the delay amount or holds it in advance as a table, calculates the delay amount from the input impulse response, and reverses the phase difference ΔΦ according to the delay amount. The phase (e ⁻ ΔΦ) is multiplied by the maximum value of the impulse response. As a result, the phase difference ΔΦ due to the difference in the frequency of the SP signal between symbols is canceled.

  The phase deviation calculation unit 17 obtains the phase rotation amount ΔΘ from the impulse response holding unit 13 from the maximum value of the impulse response of the current symbol and the maximum value of the impulse response of the previous symbol corrected by the phase difference correction unit 16. calculate.

FIG. 5 is a diagram illustrating an example of the calculated phase rotation amount.
Shown here is the maximum value I _n-2 of the impulse response of (n-2) th symbols shown in FIG. 4, the maximum value I _n of the impulse response of the n th symbol, the manner for obtaining the phase difference.

Since the phase difference ΔΦ due to the frequency difference between the SP signal symbols is canceled by the phase difference correction unit 16, the phase deviation calculation unit 17 calculates only the phase rotation amount ΔΘ due to fading. Phase deviation calculation unit 17, the phase rotation amount .DELTA..theta, or calculated by calculating the difference in the maximum value I _n-2 and the phase of the maximum value I _n, is calculated by using the inner product operation.

  The phase rotation amount ΔΘ obtained by the phase deviation calculation unit 17 is proportional to the Doppler frequency fd. Therefore, the Doppler frequency calculation unit 18 calculates the Doppler frequency fd by multiplying the phase rotation amount ΔΘ by a predetermined value.

  By the way, as described above, in the OFDM frame of the digital terrestrial broadcasting standard ISDB-T, SP signals are inserted at intervals of 12 in each symbol. Therefore, if a multipath having a length of 1/24 symbol or more exists, the impulse response output from the inverse Fourier transform unit 12 may be folded.

FIG. 6 is a diagram illustrating a state in which the impulse response is folded.
The horizontal axis represents time, and the vertical axis represents power.
FIG. 6 shows a state in which the preceding wave Ip, the main wave Im, and the delay wave Idx appear in this order, but the delay wave Idx is obtained by folding the delay wave Id. In the mobile reception environment, since the power fluctuates with time, a situation occurs in which the power of the delayed wave Id temporarily becomes larger than the power of the main wave Im. For this reason, when the delayed wave Id larger than the power of the main wave Im is turned back, the maximum value position detection unit 15 detects the position of the delayed wave Idx as the position of the main wave Im. In that case, the phase deviation calculation unit 17 cannot calculate an accurate phase rotation amount ΔΘ, and the Doppler frequency calculation unit 18 cannot calculate an accurate Doppler frequency fd.

Therefore, the semiconductor integrated circuit 10 of the present embodiment shown in FIG. 1 further has the following functions.
The subcarrier group storage unit 19 holds a subcarrier group including a pilot signal and a data signal included in a received signal after Fourier transform (for example, FFT). The subcarrier group storage unit 19 may hold all subcarriers of each symbol or may hold subcarriers of some segments.

  The transmission path response value generation unit 20 tentatively determines a data signal in the subcarrier group, obtains a tentative determination value of the transmission signal point, and then divides the received data signal by the tentative determination value. A transmission line response value indicating the influence of the path is generated. In the temporary determination, for example, a temporary determination value is generated by hard-determining the data signal according to a modulation scheme such as QPSK (Quadrature Phase Shift Keying), 16QAM (Quadrature Amplitude Modulation), or 64QAM.

  The inverse Fourier transform unit 21 performs an inverse Fourier transform (for example, IFFT) by combining the pilot signal held in the subcarrier group storage unit 19 and the transmission path response value obtained from the data signal, thereby obtaining an impulse response. calculate.

The impulse response holding unit 22 holds the impulse response calculated by the inverse Fourier transform unit 21 and outputs the impulse response to the maximum value position detection unit 23.
The maximum value position detection unit 23 detects the position of the maximum value of the input impulse response and outputs it to the multipath determination unit 24 together with the information of the impulse response. If the impulse response obtained from the subcarrier group including the data signal is a multipath having a delay amount within a ½ symbol length, unlike the impulse response obtained only from the pilot signal, signal folding does not occur. Therefore, the impulse response detected by the maximum value position detection unit 23 is not affected by aliasing.

  The multipath determination unit 24 determines whether or not a multipath having a predetermined length or more has occurred from the input impulse response and the position of the maximum value (main wave position). Specifically, the multipath determination unit 24 determines the length of the multipath by detecting how far the preceding wave (delayed wave) is away from the main wave. Then, the multipath determination unit 24 has a multipath that is longer than a length that may cause aliasing (for example, a 1/24 symbol length or more when receiving an OFDM frame of the terrestrial digital broadcasting standard ISDB-T). It is determined whether or not there is.

Thereby, the multipath determination unit 24 can determine whether or not aliasing occurs in the impulse response obtained only from the pilot signal.
Then, the multipath determination unit 24 outputs the determination result to the main wave position specifying unit 25. Further, when the multipath determination unit 24 detects a multipath having a predetermined length or longer, the multipath determination unit 24 sends the position of the maximum value of the impulse response detected by the maximum value position detection unit 23 to the main wave position specification unit 25. The multipath determination unit 24 may send the impulse response data itself to the main wave position specifying unit 25. The multipath determination unit 24 disables the function of the main wave position specifying unit 25 when a multipath longer than a predetermined length is not detected.

  When receiving a determination result indicating that a multipath of a predetermined length or longer has been detected, the main wave position specifying unit 25 determines an impulse response based on the position of the maximum value detected by the maximum value position detecting unit 23. The main wave position in the impulse response obtained from the pilot signal output from the delay unit 14 is specified.

FIG. 7 is a diagram illustrating how the main wave position is specified.
FIG. 7A shows the position Ax of the maximum value of the impulse response obtained from the subcarrier group including the data signal. The vertical axis is power, and the horizontal axis is X (time). The horizontal axis is actually represented by IFFT points. First, the main wave position specifying unit 25 performs conversion for matching the time axis (horizontal axis X) with the time axis (horizontal axis Y) of the impulse response obtained only from the pilot signal, as shown in FIG. The position Ay is obtained as follows. Thereby, it is possible to compare with the impulse response obtained only from the pilot signal.

  For example, when the OFDM standard of 1 seg and Mode 3 is used, the conversion formula is as follows. In the following formula, for example, the number of IFFT points of impulse response obtained from a subcarrier group including a data signal is 256, and the number of IFFT points of impulse response obtained only from a pilot signal is 64.

Ay = (Ax-256 / 2) × 3-64 / 2
Here, Ax-256 / 2 represents the deviation (number of points) of the main wave from the FFT window position. Since the FFT shift is performed, the FFT window position is assumed to be 256/2.

  In the example in the lower diagram of FIG. 7B, the FFT window position is aligned with the position B1 where the impulse response of the preceding wave exists. Further, it is shown that the impulse response at the position B2 is obtained by folding the impulse response at the position B4.

  When the 13seg, Mode3 OFDM standard is used, the conversion formula is as follows. In the following formula, for example, the number of IFFT points of impulse response obtained from the subcarrier group including the data signal is 256, and the number of IFFT points of impulse response obtained from the pilot signal alone is also 256.

Ay = (Ax−256 / 2) × 12−256 / 2
The main wave position specifying unit 25 specifies, as the main wave position, the position of the impulse response obtained only from the pilot signal, which is at a position substantially equal to the position Ay obtained as described above. Specifically, as shown in FIG. 7B, the main wave position specifying unit 25 detects whether or not there is an impulse response obtained only from a pilot signal existing within a predetermined range (± α) from the position Ay. To do. α is, for example, about 10 points or less in IFFT points. In the example of FIG. 7B, among the impulse response positions B1, B2, and B3 obtained from only the pilot signal, the impulse response at the position B2 is within the above range. Therefore, the main wave position specifying unit 25 specifies the impulse response existing at the position B2 as the main wave.

The main wave position specifying unit 25 notifies the phase difference correcting unit 16 of the specified main wave position.
For example, when an impulse response as shown in the lower side of FIG. 7B is input, the phase difference correction unit 16 is notified from the main wave position specifying unit 25 instead of the position B3 where the impulse response is the maximum value. The position B2 is used as the main wave position.

As a result, signals other than the main wave at the position B3 that temporarily has the maximum power due to the influence of mobile reception are prevented from being recognized as the main wave.
The phase difference correction unit 16 obtains the phase difference ΔΦ according to the delay amount d between the position B1 of the preceding wave and the position B4 from which the identified main wave position B2 is turned back, and obtains the opposite phase of the phase difference ΔΦ. (E ⁻ ΔΦ) is multiplied by the value of the main wave of the impulse response. As a result, the phase difference ΔΦ due to the difference in the frequency of the SP signal between symbols is correctly canceled.

  Thereafter, as described above, the phase deviation calculation unit 17 outputs the maximum value of the impulse response of the current symbol from the impulse response holding unit 13 and the maximum value of the impulse response of the previous symbol corrected by the phase difference correction unit 16. From this, the phase rotation amount ΔΘ is calculated.

Then, the Doppler frequency calculation unit 18 calculates the Doppler frequency fd based on the phase rotation amount ΔΘ.
Thus, in the semiconductor integrated circuit 10 of the present embodiment, an impulse response that is not affected by signal folding is calculated using a subcarrier group including a data signal and a pilot signal, and the position of the maximum value is obtained. In addition, the correct main wave position is specified. As a result, the Doppler frequency can be accurately obtained even when a multipath having a predetermined length or more that may cause a return of the impulse response occurs.

Hereinafter, the received signal processing method by the semiconductor integrated circuit 10 according to the present embodiment is summarized by a flowchart.
FIG. 8 is a flowchart showing a received signal processing method by the semiconductor integrated circuit of the present embodiment.

  The inverse Fourier transform unit 12 performs an inverse Fourier transform on the pilot signal included in the received signal after the Fourier transform, and calculates an impulse response (step S1). The maximum value position detector 15 detects the position of the maximum value of the impulse response (step S2). The impulse response delay unit 14 holds and delays the impulse response output from the impulse response holding unit 13 (step S3).

  On the other hand, the inverse Fourier transform unit 21 calculates an impulse response by performing an inverse Fourier transform on the pilot signal and the transmission path response value obtained from the data signal (step S4). The maximum value position detector 23 detects the position of the maximum value of the input impulse response (step S5). Thereafter, the multipath determination unit 24 determines whether or not a multipath having a predetermined length or more has occurred from the input impulse response and the main wave position (steps S6 and S7). When there is a multipath longer than a predetermined length, the main wave position specifying unit 25 outputs the impulse response output from the impulse response delay unit 14 based on the position of the maximum value detected by the maximum value position detecting unit 23. The main wave position at is identified (step S8).

When there is no multipath longer than the predetermined length, or after specifying the main wave position, a phase difference correction process by the phase difference correction unit 16 is performed (step S9).
When there is no multipath longer than the predetermined length, the phase difference correction unit 16 employs the position of the maximum value of the impulse response output from the impulse response delay unit 14 as the main wave position.

On the other hand, when there is a multipath having a predetermined length or more, the phase difference correction unit 16 employs the position notified from the main wave position specifying unit 25 as the main wave position.
Then, the phase difference correction unit 16 obtains the phase difference ΔΦ according to the amount of delay between the position of the preceding wave or delay wave and the position of the main wave, and obtains the opposite phase (e ⁻ ΔΦ) of the phase difference ΔΦ as an impulse response. Multiply the value of the main wave of. As a result, the phase difference ΔΦ due to the difference in the frequency of the SP signal between symbols is canceled.

  Thereafter, the phase deviation calculation unit 17 calculates the phase from the maximum value of the impulse response of the current symbol output from the impulse response holding unit 13 and the maximum value of the impulse response of the previous symbol corrected by the phase difference correction unit 16. A rotation amount ΔΘ is calculated (step S10). Then, the Doppler frequency calculation unit 18 calculates the Doppler frequency fd based on the phase rotation amount ΔΘ (step S11).

  Thus, in the received signal processing method of this embodiment, an impulse response that is not affected by signal folding is calculated using a subcarrier group including a data signal and a pilot signal, and the position of the maximum value is obtained. In addition, the correct main wave position is specified. As a result, the Doppler frequency can be accurately obtained even when a multipath that may cause aliasing occurs.

The semiconductor integrated circuit 10 as described above is applied to, for example, the following OFDM reception system.
FIG. 9 is a diagram illustrating a schematic configuration of a main part of the OFDM reception system.

  The OFDM reception system 30 includes a tuner 31, an orthogonal demodulation unit 32, a Fourier transform unit 33, a transmission path equalization unit 35, a Doppler frequency estimation unit 34, a demapping unit 36, and an error correction unit 37. ing. The OFDM receiving system 30 includes an MPEG-2 (Moving Picture Experts Group phase 2) decoder (or H.264 decoder) 38 and an output unit 39.

The tuner 31 receives a selected RF (Radio Frequency) signal via the antenna 31a.
The orthogonal demodulator 32 performs orthogonal demodulation on the received modulated wave.

The Fourier transform unit 33 performs Fourier transform (for example, FFT) on the orthogonally demodulated reception signal to convert it into a frequency domain signal.
The Doppler frequency estimation unit 34 includes the components shown in FIG. 1, and calculates the Doppler frequency from the received signal that has been subjected to Fourier transform.

  The transmission line equalization unit 35 equalizes the received signal subjected to Fourier transform according to the Doppler frequency calculated by the Doppler frequency estimation unit 34. Thereby, the transmission signal from which disturbance due to the transmission path is removed is reproduced. Specifically, when equalizing the received signal, the transmission path equalization unit 35 obtains a transmission path estimation value from the pilot signal, and changes the coefficient of the filter used at this time according to the Doppler frequency. Since the Doppler frequency is proportional to the moving speed of the receiver, by changing the filter coefficient according to the Doppler frequency, it is possible to obtain a transmission path estimation value according to the moving speed, and the transmission signal can be accurately reproduced. .

The demapping unit 36 determines the signal point position of the transmission signal from which the disturbance has been removed, and derives the bit pattern of the transmission signal.
The error correction unit 37 corrects the data error using, for example, a Reed-Solomon code or a convolutional code with respect to the output of the demapping unit 36.

The MPEG-2 decoder 38 decodes the data encoded in the MPEG-2 format output from the error correction unit 37.
The output unit 39 is, for example, a display or a speaker, and outputs decoded video data or audio data.

  In the OFDM receiving system 30 as described above, for example, as shown in FIG. 9, each component from the orthogonal demodulation unit 32 to the error correction unit 37 is provided as a semiconductor integrated circuit 40. The semiconductor integrated circuit 40 may include an MPEG-2 decoder 38.

  Such an OFDM receiving system 30 can be applied to, for example, a terrestrial digital broadcast receiving apparatus or a portable terminal capable of viewing terrestrial digital broadcasts. As described above, the semiconductor integrated circuit according to the present embodiment can calculate the Doppler frequency with high accuracy, and thus is particularly useful for application in a portable terminal.

  As described above, one aspect of the semiconductor integrated circuit and the received signal processing method of the present invention has been described based on the embodiments. However, these are merely examples, and the present invention is not limited to the above description.

DESCRIPTION OF SYMBOLS 10 Semiconductor integrated circuit 11 Pilot signal memory | storage part 12,21 Inverse Fourier transform part 13,22 Impulse response holding part 14 Impulse response delay part 15,23 Maximum value position detection part 16 Phase difference correction part 17 Phase deviation calculation part 18 Doppler frequency calculation Unit 19 Subcarrier group storage unit 20 Transmission path response value generation unit 24 Multipath determination unit 25 Main wave position specifying unit

Claims (5)

A first inverse Fourier transform unit that calculates a first impulse response by performing an inverse Fourier transform on the pilot signal included in the received signal after the Fourier transform;
A second inverse Fourier transform unit that calculates a second impulse response by performing an inverse Fourier transform on the transmission line response value obtained from the data signal included in the received signal and the pilot signal;
A multipath determination unit that determines whether or not a multipath of a predetermined length or more has occurred based on the second impulse response;
A main wave position that specifies a main wave position in the first impulse response based on the position of the maximum value of the second impulse response when occurrence of the multipath of the predetermined length or more is detected A specific part,
Using the first impulse response that specifies the main wave position, based on the delay amount between the main wave and the preceding wave or the delayed wave, the difference due to the difference in the frequency of the pilot signal between symbols A phase difference correction unit for correcting the phase difference of the first impulse response;
A phase deviation calculation unit that calculates a phase rotation amount between the first impulse response corrected by the phase difference correction unit and the first impulse response in a different symbol;
Based on the amount of phase rotation, a Doppler frequency calculation unit that calculates a Doppler frequency;
A semiconductor integrated circuit comprising:   2. The semiconductor integrated circuit according to claim 1, wherein the multipath determination unit determines, from the second impulse response, the multipath that is longer than a length at which aliasing occurs in the first impulse response. .   3. The semiconductor integrated circuit according to claim 1, wherein the multipath determination unit determines whether or not the multipath having a length of 1/24 symbol or more is generated from the second impulse response. 4. circuit.   The said main wave position specific | specification part converts the time axis of the said 2nd impulse response according to the time axis of the said 1st impulse response, The one of Claim 1 thru | or 3 characterized by the above-mentioned. Semiconductor integrated circuit. The first inverse Fourier transform unit performs inverse Fourier transform on the pilot signal included in the received signal after the Fourier transform, and calculates a first impulse response,
A second inverse Fourier transform unit combining the transmission line response value obtained from the data signal included in the received signal and the pilot signal to perform an inverse Fourier transform to calculate a second impulse response;
The multipath determination unit determines whether or not a multipath of a predetermined length or more has occurred based on the second impulse response,
The main wave position specifying unit detects the main wave in the first impulse response based on the position of the maximum value of the second impulse response when the occurrence of the multipath having the predetermined length or more is detected. Identify the location,
The phase difference correction unit uses the first impulse response specifying the main wave position, and based on the delay amount between the main wave and the preceding wave or the delayed wave, the frequency of the pilot signal between symbols Correcting the phase difference of the first impulse response due to the difference of
A phase deviation calculator calculates a phase rotation amount between the first impulse response corrected by the phase difference correction unit and the first impulse response in a different symbol;
A received signal processing method, wherein the Doppler frequency calculation unit calculates a Doppler frequency based on the phase rotation amount.

Images