JP2001196981A - Distortion estimation device - Google Patents

Abstract

(57) Abstract: There is provided a distortion estimating apparatus capable of appropriately performing distortion estimation based on a differential phase modulation signal or a phase modulation signal. SOLUTION: A phase difference signal generation unit 42 receives a predetermined subcarrier component included in an OFDM signal from an FFT. This subcarrier component is a DQPSK signal, and the phase difference signal generation unit 42 generates a phase difference signal based on this signal. Such a phase difference signal is a continuous DQPSK
It has a phase corresponding to the phase difference of the signal. Then, the quadruple multiplier 46 performs an operation to quadruple the phase of the phase difference signal to generate a pseudo pilot signal.
The distortion information is generated based on the pseudo pilot signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a distortion estimating apparatus, and more particularly, to a phase shift keying (PSK) signal and a differentially encoded signal (DPSK).
The present invention relates to a distortion estimating apparatus for estimating phase distortion and amplitude distortion of a PSK signal.

[0002]

2. Description of the Related Art As a method of expanding a service area of a terrestrial television or the like, there is a broadcast wave relay system for receiving a broadcast wave, amplifying the power thereof, and retransmitting the amplified broadcast wave. In a conventional analog television broadcast, a broadcast wave is received by a reception antenna of a wireless relay device (relay station), power is amplified, and then the broadcast wave is retransmitted from a transmission antenna at a frequency different from the reception broadcast wave. However, digital television broadcasting, which is currently under development, is based on OFDM (Orthogonal
Since the frequency division multiplexing (orthogonal frequency division multiplexing) system is adopted, a so-called SFN (reception of a broadcast wave at the same frequency as a received broadcast wave) is performed after a broadcast wave is received by a wireless relay device, and power is amplified. Single Frequ
ency Network (single frequency network). According to the SFN, the frequency can be effectively used.

[0003] However, if an attempt is made to realize SFN, the effect of a so-called wraparound wave, in which a transmission wave from a transmission antenna wraps around a reception antenna of the same radio relay apparatus, cannot be ignored. That is, in the SFN, since the same frequency is used for the transmission wave and the reception wave, spatial feedback occurs due to the loop phenomenon, and when the feedback ratio is large, even the oscillation state occurs. In this case, the relay signal is deteriorated.

[0004] In this regard, “Study of loop-back canceller for broadcast wave relay for terrestrial digital broadcasting SFN” published in Technical Report of the Institute of Electronics, Information and Communication Engineers (EMCJ98-111) includes an SP (Scattered Pilot) signal. A technique for canceling a wraparound component using a known signal is disclosed. FIG. 4 is a diagram for explaining the operation principle of the loop interference canceller described in the document.
As shown in FIG. 1, the interference canceller 100 includes a distortion estimating device 102 and a distortion compensating unit 104. The distortion estimating device 102 performs FFT (Fast Fourie
r Transform) 106, a distortion estimating unit 108, and a two-dimensional filter 110. The received signal here is a signal modulated by the OFDM method, is converted into a baseband signal by a frequency conversion unit (not shown), and is supplied to the FFT 106. In the FFT 106, each subcarrier component is generated from the baseband-converted received signal. A known SP signal (reference signal) is supplied to the distortion estimating unit 108 together with each subcarrier component, and distortion information is generated for the SP signal included in a part of each subcarrier.

That is, as shown in FIG. 5, the SP signals are distributed in each subcarrier, and distortion estimating section 108 compares the received SP signal with the reference signal for the symbol in which the SP signal is allocated. The distortion information can be directly generated. Note that, in the same figure, a black square represents an SP signal, and a white square represents other data signals. The distortion information is supplied to the two-dimensional filter 110. Here, even for a symbol on which no SP signal is arranged, the distortion information on the SP signal generated by the distortion estimating unit 108 is converted into the carrier direction (frequency direction) and the symbol direction ( By performing interpolation in the time direction), distortion information is generated. The two-dimensional filter 110 generates distortion information relating to other symbols, for example, by averaging the distortion information relating to the SP signal generated by the distortion estimating unit 108. The distortion information generated in this way is supplied to the distortion compensation unit 104, where it is converted into a time signal. Then, distortion compensation using the time signal is performed.

[0006]

The above description relates to distortion compensation for a received signal in a synchronous modulation system.
However, for example, in the above digital broadcasting, OFDM
The subcarriers are grouped by a predetermined number (13 groups per channel), and the modulation scheme may be different for each group (hereinafter, these subcarrier groups are referred to as segments). In this case, for example, a segment in which a differential phase modulation signal (DQPSK) is used may appear depending on a line condition. As described above, when a differential phase modulation signal is transmitted in a certain segment, as shown in FIG.
A symbol carrying a P (Continual Pilot) signal only exists on a specific subcarrier (in the figure, a black square represents a CP signal, and a white square represents other data signals). In such a case, for example, when there is only a differential modulation segment, distortion in the frequency direction cannot be estimated, and even if a synchronous modulation segment exists in an adjacent segment, the SP signal is separated by the segment width. The distortion estimation accuracy is degraded.

FIG. 7 shows a signal obtained by combining a reflected wave (one wave) and a wraparound wave (one wave) with a direct wave, and a differential phase modulation method is applied to some of the segments (here, FIG. 7). For example, it is assumed that this is applied to # 2, 6, 7, and 12), and the case where a synchronous modulation scheme is applied to other segments is input to the interference canceller 100 according to the related art. The output waveform is shown. The horizontal axis indicates frequency, and the vertical axis indicates amplitude. As shown in the figure, in this case, for the segments other than # 2, 6, 7, and 12, the interference canceller 100 according to the related art is used.
, The amplitude is within a certain range, but the SP of the segments # 2, 6, 7, and 12 does not exist, so that the interference canceller 100 according to the related art cannot be applied. Amplitude fluctuations remain severe. If the output waveform as shown in the figure is left unchecked, the distortion of the segment to which the differential phase modulation method is applied increases as the number of relay stages overlaps.

On the other hand, a segment (differential phase modulation segment) to which the differential phase modulation system is applied to a segment to which the synchronous modulation system is applied (synchronous modulation segment).
, The compensation signal for the differential phase modulation segment may be generated, for example, by interpolating the compensation signal for the synchronous modulation segment. However, there is no guarantee that synchronous modulation segments always exist, and if all segments are differential phase modulation segments, no distortion compensation can be performed.

Therefore, if it becomes possible to generate distortion information relating to the differential phase modulation signal based on the differential phase modulation signal, it is possible to generate distortion information for the differential phase modulation segment regardless of the presence or absence of the synchronous modulation segment. It is meaningful because it can generate information. Further, if it becomes possible to generate distortion information related to the phase modulation signal based on the phase modulation signal, for example, the two-dimensional filter 11
This is also significant because it is not necessary to perform the interpolation processing of the distortion information by 0.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a distortion estimating apparatus capable of appropriately performing distortion estimation based on a differential phase modulation signal or a phase modulation signal. It is in.

[0011]

In order to solve the above-mentioned problems, a distortion estimating apparatus according to the present invention provides a pseudo pilot signal generating means for generating a pseudo pilot signal by performing a phase multiplication operation on a phase modulated signal. And distortion estimating means for generating distortion information based on the pseudo pilot signal.

According to the present invention, a pseudo pilot signal having a phase independent of a modulation component is generated by performing a phase multiplication operation on a phase modulation signal. For example, a pseudo pilot signal in which phase modulation is canceled can be generated by performing an operation of doubling the phase of a phase modulated signal according to the BPSK (Binary PSK) method. By performing an operation to quadruple the phase of the modulated signal, it is possible to generate a pseudo pilot signal in which the phase modulation is canceled. Then, based on the pseudo pilot signal thus generated, distortion information is generated, for example, by comparing the pseudo pilot signal with a pseudo pilot signal to be originally obtained (a pseudo pilot reference signal).
By doing so, regardless of the known signal such as the SP signal,
It is possible to preferably generate distortion information based on the phase modulation signal. Note that the phase modulation signal here includes a differential phase modulation signal.

Further, the distortion estimating apparatus according to the present invention provides a phase difference signal generating means for generating a phase difference signal having a phase corresponding to a phase difference between successive differential phase modulation signals based on the differential phase modulation signal. A pseudo pilot signal generating means for generating a pseudo pilot signal by performing a phase multiplication operation on the phase difference signal, and a distortion estimating means for generating distortion information based on the pseudo pilot signal. Features.

According to the present invention, a phase difference signal is generated based on a differential phase modulation signal. This phase difference signal has a phase corresponding to the phase difference between successive differential phase modulation signals. Then, a pseudo pilot signal is generated by performing a phase multiplication operation on the phase difference signal. For example, DB
In the case of the differential phase modulation signal based on the PSK method, a phase difference signal having a phase of about 0 or π is generated based on the differential phase modulation signal, and a pseudo pilot signal is generated by doubling the phase. . Also, for example, DQPSK
In the case of the differential phase modulation signal by the system, a phase difference signal having phases of about 0, ± π / 4, and π is generated based on the differential phase modulation signal, and the pseudo pilot signal is generated by quadrupling this phase. Is generated. Then, based on the pseudo pilot signal thus generated, distortion information is generated, for example, by comparing the pseudo pilot signal with a pseudo pilot signal to be originally obtained (a pseudo pilot reference signal). By doing so, it is possible to suitably generate distortion information based on the differential phase modulation signal without using a known signal such as the SP signal.

In one aspect of the present invention, in the distortion estimating apparatus, the distortion estimating means generates the distortion information based on distortion information obtained for a signal transmitted by a carrier having a close frequency. It is characterized by doing. As described later, a pseudo pilot signal is generated by performing a phase multiplication operation on a phase modulation signal, or a pseudo pilot signal is generated by performing a phase multiplication operation on a phase difference signal based on a differential phase modulation signal. Is generated, uncertainty inevitably occurs even if an attempt is made to generate distortion information based on these pseudo pilot signals. Therefore, in this embodiment, distortion information is considered in consideration of the empirical rule that distortion of a signal transmitted by a carrier having a close frequency is highly correlated with distortion of a phase modulation signal or a differential phase modulation signal to be processed. Generate
In this way, the influence of the uncertainty can be eliminated, and the distortion information can be preferably generated deterministically.

Further, in one aspect of the present invention, the distortion estimating means adds a restriction corresponding to the phase multiplying operation,
The method is characterized in that the distortion information is generated. The pseudo pilot signal is generated by performing a phase multiplication operation, and this operation also multiplies the phase distortion. In this aspect, since the distortion information is generated with the restriction corresponding to the phase multiplying operation, it is possible to avoid a problem that the phase distortion is multiplied.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a diagram showing a configuration of a distortion estimating apparatus according to an embodiment of the present invention. A distortion estimating device 12 shown in FIG. 1 is provided in a wireless relay device 10 used in a digital broadcasting system,
Represents a receiving antenna 16, amplifiers 18 and 28, frequency converters 20 and 26, an A / D converter 22, a distortion estimating device 12,
It is configured to include a distortion compensator 14, a D / A converter 24, and a transmission antenna 30. Here, the distortion estimation device 1
2 and the distortion compensator 14 function as an interference canceller. The distortion estimating device 12 includes an FFT 32, a synchronous modulation distortion estimating unit 34, a differential modulation distortion estimating unit 36, a two-dimensional filter 38, and a distortion compensating unit 14.

The signals received by the receiving antenna 16 include:
Synchronous modulation methods such as QPSK, 16QAM and 64QAM as the primary modulation, and differential phase modulation method (DQPSK)
Modulation is performed. Also, OF as the secondary modulation
Modulation by the DM method is performed. After the received signal is once amplified by the amplifier 18, it is converted into a baseband signal by the frequency converter 20. The baseband signal (complex signal) is converted into a digital signal by the A / D converter 22 and then supplied to the distortion estimator 12 and the distortion compensator 14. The sampling frequency in the A / D converter 22 is designed to ensure the speed required for demodulating the digital broadcast wave, and the number of samples is a power of 2 for one effective symbol period, as requested by the FFT 32. It is set as follows.

In the distortion estimating device 12, the received baseband signal is input to the FFT 32, where each subcarrier component (complex signal) is output. The subcarrier component is output from the synchronous modulation distortion estimator 34 or the differential modulation distortion estimator 36.
Supplied to In a digital broadcasting system, 13 segments are set for one channel, and the modulation scheme used in each segment is a transmission and multiplex configuration (TMCC) included in the segment.
Control) information. The control unit (not shown) sets the modulation method of each segment to FF
Judgment is made based on the output of T32, and if the synchronous modulation scheme is used, the FFT3
2 to supply the subcarrier component output from on the other hand,
When the differential phase modulation method is used, the subcarrier component output from the FFT 32 is supplied to the differential modulation distortion estimating unit 36.

The synchronous modulation distortion estimating section 34 performs distortion estimation on a segment using the synchronous modulation method. In the synchronous modulation method, as shown in FIG. 5, SP signals are distributed in the symbol direction and the carrier direction. The synchronous modulation distortion estimating unit 34 generates distortion information for each SP signal using the prepared SP signal (reference signal) and the SP signal included in the received signal. This distortion information is supplied to the two-dimensional filter 38. The two-dimensional filter 38 interpolates the distortion information for each SP signal to obtain the SP signal.
Distortion information is generated for symbols other than the symbol on which the signal is carried. Then, the distortion information is transmitted to the distortion compensator 1.
4 where distortion compensation is performed on the received baseband signal based on the distortion information.

On the other hand, the differential modulation distortion estimating unit 36 performs distortion estimation on a segment using the differential phase modulation method. In the differential phase modulation method, as shown in FIG.
Signals are not distributed and CP
Only the signals are located. As will be described later, the specific subcarrier is used as a reference subcarrier in the differential modulation distortion estimator 36. Differential modulation distortion estimating section 36 performs differential phase modulation (DQPSK, DB) on subcarriers other than the subcarriers on which CP signals are allocated.
PSK) signal and generates a phase difference signal having a phase corresponding to the phase difference between successive differential phase modulation signals.
Then, a pseudo pilot signal is generated by performing a phase multiplication operation on these phase difference signals. For example, DQ
An operation to quadruple the phase is performed on the PSK signal, and DB
An operation of doubling the phase is performed on the PSK signal. As a result, the phase modulation component is removed. The differential modulation distortion estimating unit 36 generates distortion information for each pseudo pilot signal from a comparison between the pseudo pilot signal thus obtained and the pseudo pilot signal without distortion (pseudo pilot reference signal). . At this time, even if an attempt is made to generate distortion information simply by using a pseudo pilot signal, it is not always possible to generate a correct one. That is, the problem of phase uncertainty remains.

FIG. 2 is a signal point arrangement diagram for explaining this problem. This figure shows the symbol arrangement of the phase difference signal with respect to the DBPSK signal. Here, the DBPSK signal will be described, but the DQPSK signal has a similar problem. In BPSK, signal points of a phase difference signal are arranged at 0 [rad] indicated by “A” and π [rad] indicated by “B” in FIG. When there is no distortion, both signal points A and B are operated to double the phase by A
Move to the point. Therefore, by doubling the phase of the phase difference signal and using it as a pseudo pilot signal, and using the signal at point A as a pseudo pilot reference signal, distortion information can be obtained by comparing both signals. However, doubling the phase of the phase difference signal into a pseudo pilot signal and estimating the phase distortion included in the pseudo pilot signal results in estimating twice the phase distortion of the original phase difference signal. Become. For this reason, the differential modulation distortion estimating unit 36 estimates the phase distortion included in the pseudo pilot signal, and halves the estimation result to include it in the distortion information. In addition,
The amplitude distortion can be obtained by comparing the power of the pseudo pilot signal and the power of the pseudo pilot reference signal.

Here, as shown in FIG. 2B, the signal point of the received signal is located at point C although it should be originally located at point A due to distortion caused by interference or the like. Let's consider the case. By doubling the phase of the signal at point C, the signal point moves to point B. In this case,
Although the phase distortion is correctly π / 2, the signal point similarly moves to the point B when the operation of doubling the phase of the signal at the point C ′ (the phase is −π / 2) is performed. Even if the signal at point B is simply compared with the signal at point A, which is a pseudo pilot reference signal, as a pseudo pilot signal, the phase distortion is + π /
It is not possible to determine which of 2 and -π / 2.

The differential modulation distortion estimating section 36 solves the problem of the phase uncertainty as follows. That is, the OFDM signal to be signal-relayed by radio relay apparatus 10 according to the present embodiment is composed of a plurality of subcarrier components, but empirically, distortions related to adjacent subcarriers have a high correlation. The frequency correlation of the distortion caused by the multipath phenomenon and the wraparound phenomenon in the SFN configuration is as follows.
It is known that the delay time is inversely proportional to the delay time. The delay time is relatively small with respect to the OFDM symbol rate. Therefore, the frequency correlation of distortion between adjacent subcarriers is high. Therefore, the differential modulation distortion estimating unit 36 removes the phase uncertainty by using the correlation of the distortion with the adjacent subcarrier. That is, distortion information for a signal transmitted by a carrier having a close frequency is acquired, and the phase is determined using the distortion information. Specifically, the differential modulation distortion estimating unit 36 uses, as a reference subcarrier, a subcarrier in which CP signals are arranged among subcarriers included in the same segment. Then, distortion information is generated for the CP signal by a conventional method. On the other hand, when distortion information is generated for subcarriers adjacent to the reference subcarrier, distortion information candidates are generated by comparing the pseudo pilot signal and the pseudo pilot reference signal as described above. Information close to the obtained distortion information is defined as true distortion information. Similarly, when distortion information is generated for a subcarrier further adjacent to the subcarrier, distortion information candidates are generated by comparing the pseudo pilot signal and the pseudo pilot reference signal as described above, and the adjacent subcarrier ( Those that are close to the distortion information already obtained for the non-reference subcarrier) are regarded as true distortion information. With respect to other adjacent carriers, distortion information candidates are sequentially generated in a direction away from the reference subcarrier, and one of them is selected as true distortion information based on the distortion information of the previously determined previous subcarrier.

Here, the phase uncertainty is removed by using the reference subcarriers of the same segment, but the phase uncertainty may be removed by using the reference subcarriers of the adjacent segment. For example, when generating distortion information about a certain subcarrier, in order to remove the phase uncertainty, a reference subcarrier of the same segment and a reference subcarrier of an adjacent segment are used as sub-carriers to be processed. It is preferable to use the closer one.

Here, a configuration example of the differential modulation distortion estimating unit 36 will be described. FIG. 3 is a diagram illustrating an example of the configuration of the differential modulation distortion estimation unit 36. The differential modulation distortion estimating unit 36 shown in the figure includes distortion estimating units 48, 50, 56, phase difference signal generating units 40, 42, a phase doubling unit 44, and a phase quadrupling unit 4.
6, a distortion 1/2 times section 52, a 1/4 times distortion section 54, and an estimated distortion adjustment section 58. The distortion estimating units 48, 50, and 56 are configured using, for example, a conventional general distortion estimating technique, and compare an input pseudo pilot signal with a pseudo pilot reference signal to determine the phase distortion and amplitude of the input signal. This is to generate distortion information representing distortion. The distortion estimating unit 56 outputs C
The P signal is input, and distortion information for the CP signal is generated by comparison with a predetermined reference signal. The pseudo pilot signals output from the phase doubling unit 44 and the phase quadrupling unit 46 are input to the distortion estimating units 48 and 50. By comparing the pseudo pilot signals with a predetermined pseudo pilot reference signal, candidates for distortion information for the pseudo pilot signals are obtained. (Distortion information that cannot be determined anyway due to the problem of phase uncertainty) is generated.

The phase difference signal generator 40 is configured to receive, from among the subcarrier components output from the FFT 32, those related to control information to which DBPSK is applied. On the other hand, the phase difference signal generation unit 42 is configured to receive a subcarrier component output from the FFT 32 relating to a data signal to which DQPSK is applied. The phase difference signal generators 40 and 42 can temporarily hold the input signal. Based on two consecutive input signals (differential phase modulation signals), the phase difference signal generators 40 and 42 determine the phase difference between the input signals. Are output as a phase difference signal. The amplitude of the phase difference signal may be equal to one of the amplitudes of two consecutive input signals, or may be equal to the average of these amplitudes. In any case, the amplitude may be determined based on at least one of the two amplitudes.

The phase doubling section 44 performs an operation of doubling the phase of the phase difference signal output from the phase difference signal generation section 40. D for subcarriers related to control information
Since BPSK is used, the modulation component can be removed by doubling the phase here. The phase doubling unit 44 calculates a phase amount and an amplitude from, for example, a phase difference signal (complex signal), and doubles only the phase (with the power unchanged) to generate a pseudo pilot signal.

On the other hand, the phase quadrupler 46 changes the phase of the phase difference signal output from the phase difference signal generator 42 by four.
Perform the doubling operation. Since DQPSK is used for the subcarrier related to the data signal, the modulation component can be removed by quadrupling the phase here. The phase quadrupling section 46 calculates a phase amount and an amplitude from the phase difference signal, for example, and quadruples only the phase (power is kept as it is) to generate a pseudo pilot signal.

The distortion information candidates generated by the distortion estimating unit 48 are temporarily input to the phase 倍 doubling unit 52. Here, the phase distortion of the distortion information is halved. On the other hand, the distortion information candidates generated by the distortion
It is input to the quadruple unit 54. Here, phase distortion of the distortion information is multiplied by １ ／.

The estimated distortion adjusting unit 58 includes a distortion estimating unit 56
And the distortion information is supplied from the
All candidates of the corrected distortion information are supplied from the 2 and distortion 1/4 times section 54. Distortion 1/2 times section 52 and distortion 1/4
The corrected distortion information output from the multiplier 54 includes a sine component and a cosine component of the phase distortion. Further, the estimated distortion adjustment unit 58 can acquire distortion information on an adjacent segment, and selects one of the distortion information candidates based on this information. The distortion information obtained for all symbols in this way is supplied to the distortion compensator 14 via, for example, a two-dimensional filter 38, where distortion compensation is performed on the received baseband signal. Alternatively, it may be directly reflected on a received signal delayed by a predetermined time. When the two-dimensional filter 38 receives the distortion information for the SP signal from the synchronous modulation distortion estimating unit 34, it generates distortion information for other symbols by interpolation processing and supplies it to the distortion compensating unit 14. When the distortion information for all the symbols is received from the modulation distortion estimating unit 36, the interpolation processing is omitted and the distortion information is directly transferred to the distortion compensating unit 14.

According to the distortion estimating apparatus 12 described above,
Even when the synchronous modulation segment is not adjacent to the differential modulation segment, distortion information can be appropriately estimated. For this reason, distortion compensation using the distortion information can be performed on the differential modulation segment, and the fluctuation of the phase and the amplitude can be suppressed similarly to the synchronous modulation segment. Thus, the oscillation phenomenon in the wireless relay device can be prevented. Further, it is possible to prevent a situation in which a remarkable amplitude fluctuation occurs in the differential modulation segment and an unnecessary wave is generated.

The distortion estimating device 12 described above can be implemented in various modifications.

For example, when a large dip occurs in amplitude in a certain subcarrier of a certain segment due to interference, the generation of distortion information by the above procedure is not appropriate for the subcarrier in which the dip occurs. For this reason, a threshold value determined by a test is set in advance so as not to deteriorate the estimation performance, and when the amplitude of the subcarrier is lower than the threshold value, the subcarrier having the closest frequency is set. The generated distortion information may be diverted. This subcarrier may belong to the synchronous modulation segment,
It may belong to a differential modulation segment.

The distortion information to be supplied to the two-dimensional filter 38 for the differential modulation segment need not be for all symbols of all carriers, but is only for a part of the symbol as in the case of the synchronous modulation segment. You may make it supply. In this case, the two-dimensional filter 38 processes the output of the synchronous modulation distortion estimator 34 and the output of the differential modulation distortion estimator 36 in the same manner.

Also in the synchronous modulation segment, as in the case of the differential modulation segment, it is possible to generate distortion information based on a data signal other than the SP signal.
The distortion estimation device in this case may have a configuration in which the phase difference signal generation units 40 and 42 are removed from FIG. This eliminates the need for the two-dimensional filter 38 to interpolate the distortion information for the SP signal. Further, the number of SP signals can be reduced, and transmission efficiency can be improved.

Further, for the differential modulation segment,
A configuration in which the phase difference signal generation units 40 and 42 are removed from FIG. 3 may be applied. Even in this case, if the differential phase modulation signal has not undergone a large phase rotation due to a transmission line or the like,
The distortion information can be generated with a certain degree of accuracy.

The modulation method is π / 4-DQPSK.
, The output of the FFT 32 in each subcarrier can be multiplied by 8, but the S /
In consideration of the deterioration of the N ratio, for example, it is more advantageous to return the phase of the output of the FFT 32 related to each subcarrier by π / 4 for each symbol and to quadruple the signal points after the same signal point arrangement as DQPSK.

[Brief description of the drawings]

FIG. 1 is a diagram showing a distortion estimation device according to an embodiment of the present invention, together with a wireless relay device.

FIG. 2 is a signal point arrangement diagram illustrating a problem of phase uncertainty that occurs when distortion information is generated based on a pseudo pilot signal.

FIG. 3 is a diagram illustrating a configuration of a differential modulation distortion estimating unit.

FIG. 4 is a diagram illustrating the principle of a distortion estimating apparatus according to a conventional technique.

[FIG. 5] SP is used for a segment where the synchronous modulation method is used.
FIG. 3 is a diagram illustrating a state where signals are distributed and arranged.

FIG. 6 is a diagram illustrating a state where CP signals are arranged in a segment using the differential phase modulation scheme.

FIG. 7 shows a case where a differential phase modulation scheme is used for the second, sixth, seventh, and twelfth segments of the thirteen segments in the digital broadcasting system.
FIG. 4 is a diagram illustrating an output of an interference canceller.

[Explanation of symbols]

Reference Signs List 10 wireless relay device, 12 distortion estimating device, 14 distortion compensating unit, 16 receiving antenna, 18, 28 amplifier, 2
0,26 frequency converter, 22 AD converter, 24 D
A conversion unit, 30 transmitting antenna, 32 FFT, 34
Synchronous modulation distortion estimator, 36 Differential modulation distortion estimator, 38
Two-dimensional filter, 40, 42 phase difference signal generator, 4
4 phase doubling unit, 46 phase doubling unit, 48, 50,
56 distortion estimation section, 52 distortion 1/2 times section, 54 distortion 1/4 times section, 58 estimated distortion adjustment section.

Claims (4)

[Claims] 1. A pseudo pilot signal generating means for generating a pseudo pilot signal by performing a phase multiplying operation on a phase modulation signal, and a distortion estimating means for generating distortion information based on the pseudo pilot signal. A distortion estimating device characterized by the above-mentioned. 2. A phase difference signal generating means for generating a phase difference signal having a phase corresponding to a phase difference between successive differential phase modulation signals based on the differential phase modulation signal; A distortion estimating apparatus comprising: a pseudo pilot signal generating unit that generates a pseudo pilot signal by performing a phase multiplication operation; and a distortion estimating unit that generates distortion information based on the pseudo pilot signal. 3. The distortion estimation device according to claim 1, wherein the distortion estimation unit generates the distortion information based on distortion information obtained for a signal transmitted by a carrier having a close frequency. A distortion estimating apparatus. 4. The distortion estimating apparatus according to claim 1, wherein the distortion estimating unit generates the distortion information by applying a restriction corresponding to the phase multiplying operation. Distortion estimating device.