JP2003318857A - Digital broadcast receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a digital broadcast receiver effectively using a guard interval signal in surface wave digital television broadcast and a surface wave digital sound broadcast system. <P>SOLUTION: Two output signals with different FFT (fast Fourier transform) fetch starting points are provided to first and second FFT parts 4, 7, conversion to frequency areas are performed in the respective parts, after that, phase difference in a frequency area between both output signals is eliminated by a phase compensation circuit 8 and both output signals are synthesized by a synthesizing circuit 9. For the signal after synthesis, power of the signal is increased for time difference of the FFT fetch starting point and signal power to noise power is increased. As a result, a C/N (carrier to noise) ratio is enhanced and error-proof performance is improved. Namely, the guard interval signal is effectively used, a time diversity effect is obtained and demodulation performance is enhanced. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a terrestrial digital television broadcast receiver and a terrestrial digital audio broadcast receiver.

[0002]

2. Description of the Related Art Broadcasting systems for terrestrial digital television broadcasting and terrestrial digital audio broadcasting are described in "Technical conditions for terrestrial digital television broadcasting system" in the report of the Digital Broadcasting System Committee of the Telecommunications Technology Council. It is common to comply with the "Technical conditions for terrestrial digital audio broadcasting system" reported by the Telecommunications Technology Council. Therefore, it follows that here as well.

FIG. 17 is a diagram showing an example of a terrestrial digital television broadcast receiver that satisfies the above conditions. In addition, this block diagram is for example
Vol.54, No.6, p.905 OFDM (Orthogonal Freq
uency Division Multiplex) This corresponds to a detailed configuration of the receiver.

In FIG. 17, a tuner 1 for digital television broadcasting is in a VHF band (about 90 MHz to about 200 MHz).
And, the band of the broadcast channel desired by the user is received from the UHF band (about 470 MHz to about 770 MHz). Then, the received wave is an IF (Intermediat) whose center frequency is 57 MHz, for example.
e Frequency).

Tuner 1 for digital television broadcasting
Is converted into a digital signal by the AD (Analog → Digital) converter 2 and input to the time domain processing unit 40.

The time domain processing unit 40 is a block that performs signal processing on the received wave expressed in the time domain, performs filter processing and recovery processing such as carrier clock on time axis data, and further F as described in
The fetching position of the FT (Fast Fourier Transform) unit 4 is determined, and processing such as transferring data to the FFT unit 4 is performed.

The output of the time domain processing unit 40 is given to the FFT unit 4 and is subjected to a fast Fourier transform process for calculating the frequencies and signal intensities of a plurality of carriers (carrier waves) included in the output thereof and subjected to frequency domain processing. Become a signal. In this fast Fourier transform, for example, in the case of terrestrial digital television broadcasting, 2048 (2k), 4096 (4k), 8192
(8k) Conversion is performed in a transmission mode of any number of subcarriers (= number of data points [points / symbol]) of [book / symbol]. That is, in transmission mode 1, 2048 pieces of data are fetched, 2kFFT is executed, and converted into frequency domain data. In transmission mode 2, 4096 pieces of data are fetched and 4kFFT is executed, and in transmission mode 3, 8192 pieces of data are fetched and 8kFFT is executed. The number of effective subcarriers in each number of subcarriers is 1405,
It is 2809 and 5617. In the case of 3-segment 1-channel transmission of terrestrial digital audio broadcasting, 0.5
The conversion is performed with k, 1k, and 2k data points.

The output of the FFT section 4 is given to the frequency domain processing / synchronization / differential demodulation section 5. In the frequency domain processing / synchronization / differential demodulation unit 5, the TMCC (Tr) of the carrier in the received wave converted into the frequency domain is used.
Data processing of an ansmission and multiplex configuration control (Signal) signal and correction processing are performed using a PLL (Phase Locked Loop) circuit or the like by detecting a shift in carrier frequency. Further, depending on the modulation method of each subcarrier, differential demodulation of OFDM or synchronous demodulation by transmission path estimation correction is also performed.

Frequency domain processing / synchronization / differential demodulation unit 5
Is given to the error correction processing unit 6, where the signal is subjected to error correction processing. The error correction processing unit 6 also performs deinterleaving processing. Under the above conditions for digital television broadcasting, up to three layers can be set as a transmission mode, and the depth of deinterleave processing, the convolutional coding rate in error correction processing, and the like can be changed according to layers. It is possible. The output of the error correction processing unit 6 is output from a signal processing unit (not shown) at a subsequent stage, for example, MPEG (Moving Picture Exp).
erts Group) Output to system decoder.

Each of the above-mentioned units is a CPU (Central Pr
It is controlled by a controller (not shown) composed of an ocessing unit).

FIG. 18 is a diagram showing a part of the signal in the time domain of the terrestrial digital television broadcast and the terrestrial digital audio broadcast and the data fetch period of the FFT section 4. The terrestrial digital television broadcast and the terrestrial digital audio broadcast are transmitted in frame units, and each frame is composed of 204 symbols as shown in FIG.

Now, in one symbol, FIG.
As shown in, the main signal SG in each symbol starts with O
A guard interval GI is provided to eliminate interference in FDM transmission. This guard interval GI
Has the same data content as the latter half portion SG1 of the main signal SG. That is, in other words, this guard interval GI and a part SG1 of the main signal SG are
The same content is transmitted twice.

By providing the guard interval GI, it is possible to accurately demodulate the data of the portion of the main signal SG at the receiver side even if intersymbol interference due to the delayed wave occurs. The guard interval GI
Has the same data content as part SG1 in the main signal, the receiver side can synchronize the transmission / reception timing by calculating the correlation between the guard interval GI and part SG1 in the main signal. Use only non-overlapping data.

The data length of the guard interval GI is 1/32, 1/16, 1 / with respect to the data length of the main signal SG.
It is selected to be 8 or 1/4 and transmitted. In addition, the transmission mode that defines the modulation method of digital broadcasting,
The data length of the guard interval GI is TMC.
It is not changed during transmission unless the information of “change notification” is transmitted as the C signal. The information on these modes and the information on the guard interval length are detected by the time domain processing unit 40 at the beginning of reception.

In the time domain processing unit 40, the correlation between the guard interval GI shown in FIG. 18 and a part SG1 in the main signal is calculated, and the reproduction processing of the clock, the carrier frequency and the like is performed. Further, in the same section, the same number of data as in the transmission mode is started from the FFT acquisition point within the guard interval GI determined by the receiver side.

Here, the FFT acquisition start point is determined by the receiver so as to optimize its interference elimination capability and the like based on the correlation information using the guard interval and other information.

[0017]

In conventional digital broadcast receivers for terrestrial digital television broadcasting or terrestrial digital audio broadcasting, the guard interval signal portion is used only as a guard area for transmission / reception synchronization and interference elimination. I wasn't using it. That is, 1/32, 1/16, 1/8, 1/4 of the power of the main signal SG is used only as a guard area for interference rejection, and the power is not used for effective performance improvement. There was a problem.

Therefore, an object of the present invention is to provide a digital broadcast receiver that effectively uses a guard interval signal in a terrestrial digital television broadcast and a terrestrial digital audio broadcast system.

[0019]

According to a first aspect of the present invention, there is provided a receiving section capable of receiving a digital broadcast signal including a main signal and a guard interval having the same data content as a part of the main signal in a time domain. The digital broadcast signal received by the receiving unit from the point within the guard interval for a predetermined period from the point within the period is used as the first signal, and further, the time is before or after the point within the guard interval. The digital broadcast signal received from one point for the predetermined period is defined as a second signal, and the first and second digital broadcast signals are
A time domain-frequency domain signal converter that individually converts the signals into a frequency domain and outputs the first and second output signals, respectively, and the first or first output from the time domain-frequency domain signal converter. Receiving one of the two output signals,
The first or second output signal so as to eliminate the phase difference in the frequency domain between the first and second output signals according to the time difference between the one point and the other point within the guard interval period. Of the first or second output signal output from the phase correction circuit and the first or second output output from the time domain-frequency domain signal section. It is a digital broadcast receiver including a combining circuit that combines the other of the signals.

The invention according to a second aspect is the digital broadcast receiver according to the first aspect, wherein the time domain-frequency domain signal conversion section includes first and second Fourier transform circuits, and The first Fourier transform circuit is a digital broadcast receiver that transforms the first signal into the frequency domain, and the second Fourier transform circuit transforms the second signal into the frequency domain.

The invention according to claim 3 is the digital broadcast receiver according to claim 1, wherein the time domain-frequency domain signal transforming section includes a Fourier transform circuit, and the Fourier transform circuit comprises the Fourier transform circuit. The digital broadcast receiver performs time-division conversion of a first signal into a frequency domain and conversion of the second signal into a frequency domain.

The invention according to a fourth aspect is the digital broadcast receiver according to the first aspect, wherein the time domain-frequency domain signal converting section is provided for one of the first and second signals. A modulator that performs modulation so that the frequency bands of both signals do not overlap, a delay unit that matches the signal start timing of the other one of the first and second signals to the one signal start timing, and the signal modulated by the modulator And a signal output from the delay unit, and a Fourier transform circuit. The Fourier transform circuit transforms the output of the adder into a frequency domain, and has a different frequency band. The digital broadcast receiver converts the first and second signals into frequency domains and outputs the converted signals.

The invention described in claim 5 is the digital broadcast receiver according to claim 1, wherein the time domain-frequency domain signal conversion section includes a time domain processing section, and the time domain processing section is A digital broadcast receiver that changes the other point at which the second signal starts in accordance with information about a transmission mode that defines the number of data points of the digital broadcast signal and information about the data length of the guard interval. .

The invention according to claim 6 is the digital broadcast receiver according to claim 1, wherein the time domain-frequency domain signal conversion section includes a time domain processing section, and the time domain processing section is A digital broadcast receiver for calculating the correlation between the digital broadcast signal and a delayed signal obtained by delaying the digital broadcast signal, and changing the other point at which the second signal starts in accordance with the result.

The invention described in claim 7 is the digital broadcast receiver according to claim 1, wherein the digital broadcast signal includes a pilot signal, and the digital signal is detected by detecting the pilot signal. A detection circuit for detecting a phase error of the broadcast signal is further provided, the time domain-frequency domain signal conversion section includes a time domain processing section, and the time domain processing section is configured to detect the second signal according to the phase error. It is a digital broadcast receiver that can change the other one point starting from.

The invention according to claim 8 is the digital broadcast receiver according to claim 1, wherein the digital broadcast signal includes a pilot signal, and the time domain-
A first detection circuit that detects the pilot signal from one of the first and second output signals output from the frequency domain signal converter, and the other of the first and second output signals output from the phase correction circuit Detection circuit that detects the pilot signal from the subtractor, a subtractor that subtracts the detection results of the first and second detection circuits from each other, and a power calculator that calculates the power of the pilot signal from the calculation result of the subtractor The combining circuit further includes, according to a calculation result of the power calculator, one of the first and second output signals output from the time domain-frequency domain signal conversion unit and the phase correction circuit. It is a digital broadcast receiver that changes a ratio of combining the first and second output signals with the other output signal.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION <Embodiment 1> In the present embodiment, two time domain output signals having different FFT acquisition start points are given to the first and second FFT sections, and conversion into the frequency domain is performed respectively. After performing the above, the digital broadcast receiver is configured to eliminate the phase difference in the frequency domain between both output signals and combine both output signals.

The power of the combined signal increases by the time difference between the FFT acquisition start points, and the signal power relative to the noise power can be increased. As a result, the C / N ratio is improved and the error resistance performance is improved. That is, a digital broadcast receiver that effectively uses the guard interval signal can be obtained. Further, by generating the first and second output signals, a time diversity effect can be obtained and demodulation performance can be improved.

FIG. 1 is a diagram showing a digital broadcast receiver according to this embodiment. Among the blocks shown in FIG. 1,
Elements having the same functions as those in FIG. 17 are designated by the same reference numerals.

As shown in FIG. 1, the digital broadcast receiver according to the present embodiment has a time domain processing section 40 shown in FIG.
Instead of the above, a time domain processing unit 3 that sets two different FFT acquisition start points and supplies signals to the two subsequent FFTs is provided. And further,
First and second FFT units 4 and 7 that receive the output of the time domain processing unit 3 respectively, and a phase correction circuit 8 that corrects the phase of the signal output in the frequency domain of the second FFT unit 7 according to each carrier. And a combining circuit 9 that combines the output of the first FFT unit 4 and the output of the phase correction circuit 8 into a signal in one frequency region.

The other structure is similar to that of the digital broadcast receiver shown in FIG. 17, and therefore its explanation is omitted. Note that FIG.
The FFT unit 4 shown in (1) is shown as the first FFT unit 4 in this embodiment in order to distinguish it from the second FFT unit 7. In addition, in the present embodiment, the time domain processing unit 3 and the first and second FFT units 4 and 7 can be regarded as a time domain-frequency domain signal conversion unit.

Next, the operation will be described with reference to FIG. FIG. 2 is a diagram showing a part of a signal in the time domain of terrestrial digital television broadcasting and terrestrial digital audio broadcasting, and a data acquisition period of the first and second FFT units 4 and 7.

The signal from the tuner 1 is converted into a digital signal by the AD converter 2 and input to the time domain processing section 3. The time domain processing unit 3 performs a filtering process, a recovery process such as a carrier clock, etc. on the digital broadcast data, and a period from the first FFT acquisition start point within the guard interval GI period to the first FFT acquisition period within one symbol. The received digital broadcast signal is output as the first output signal. Further, the time domain processing unit 3 further includes the first FF by the time difference X.
The received digital broadcast signal is output as the second output signal for the second FFT acquisition period from the second FFT acquisition start point within the guard interval GI period delayed from the T acquisition start point.

As the first and second output signals from the time domain processing unit 3, time domain signals having a predetermined number of FFT data points are output according to the transmission mode of the received digital broadcast signal. In addition, the first in FIG.
The second FFT acquisition period has the same length as the period of the main signal SG.

First FFT section 4 and second FFT section 7
Performs fast Fourier transform after completely acquiring the first and second output signals, respectively. The first FFT unit 4
A buffer or the like is provided in the first and second FFT units 4 and 7 so that the output of the FFT unit 7 and the output of the second FFT unit 7 are synchronized with each other, and the timing is adjusted. The second output signal of the first and second output signals which have been subjected to the fast Fourier transform and whose timing has been adjusted is supplied to the phase correction circuit 8.

Here, the first output signal is expressed by the equation of Fourier transform as follows.

[0037]

[Equation 1]

In Equation 1, t is time and g (t)
Is a signal in the time domain, f is the frequency of each subcarrier, G
(F) represents a signal in the frequency domain, and ⇒ represents a Fourier transform.

Next, the second output signal which is delayed by the time difference X from the first output signal in the time domain is expressed as follows.

[0040]

[Equation 2]

In Expression 2, the same symbols as in Expression 1 have the same meanings as described above, e is an exponential function, and j is an imaginary number.

As can be seen from equations (1) and (2), there is a phase difference (that is, exp) between the first output signal and the second output signal, which is proportional to each subcarrier frequency f and the time difference X.
(The exponential part of (-2πjfX)) exists. Since the information of the time difference X and the information of each subcarrier frequency f are known in the receiver, it is possible to perform the phase correction for each subcarrier on the second output signal represented by the equation 2. is there.

That is, the exp (2πjf
By multiplying by X), the term of exp (−2πjfX) can be canceled, and the frequency domain signal G (f) similar to the first output signal can be obtained for the second output signal. This increases the signal power by the amount of the second output signal.

The phase correction circuit 8 is provided on the basis of the above principle, receives the second output signal output from the second FFT section 7, and receives the second output signal between the first and second output signals according to the time difference X. The second output signal is corrected so as to eliminate the phase difference in the frequency domain. Regarding the specific configuration of the phase correction circuit 8,
For example, Numerical Controlled Oscilla
tor) and a phase rotation circuit (complex operation circuit) may be combined. After the FFT processing, since each subcarrier is continuous by an integral multiple, the phase proportional to the time difference X may be accumulated and corrected by the numerically controlled oscillator and the phase rotation circuit.

By performing the phase correction on the second output signal, the first and second output signals become the same signal after the phase correction. Therefore, if the first output signal from the first FFT unit 4 and the second output signal after the phase correction are combined, the signal power of the digital broadcast signal increases. The synthesis circuit 9 is provided for this purpose.

As a signal synthesizing method, an equal gain synthesizing method for adding a plurality of signals with equal gain, a maximum ratio synthesizing method for synthesizing according to the envelope ratio of the signals, etc. are known. A method suitable for the circuit configuration required for the circuit 9 may be adopted. For example, in the case of equal gain combination, since only the first and second output signals are added, only one adder is required, and the combining circuit 9 can be easily configured.

In the synthesized output signal in the frequency domain,
Since the signal power is increased by the time difference X, the C / N ratio is improved and the error resistance performance is improved as compared with the case where the original first or second output signals are individually taken out. this is,
This is because the signal component of the SG1a portion of the main signal SG in FIG. 2 increases.

That is, according to the digital broadcast receiver of the present embodiment, the phase correction circuit 8 outputs the second output so as to eliminate the phase difference in the frequency domain of the first and second output signals according to the time difference X. Correct the signal. Then, the synthesis circuit 9
Combines the output of the phase correction circuit 8 and the output from the first FFT unit 4. Therefore, in the combined signal, the signal power increases by the time difference X, and the signal power with respect to the noise power can be increased. As a result, the C / N ratio is improved,
The error resistance performance is improved. That is, a digital broadcast receiver that effectively uses the guard interval signal can be obtained. Also, by generating the first and second output signals,
A time diversity effect can be obtained and demodulation performance can be improved.

Further, in this embodiment, the first and second FFT sections 4 and 7 are provided. Therefore, the load of signal processing is smaller than that in the case where one Fourier transform circuit performs both signal processing of the first and second output signals.

In the present embodiment, the phase correction circuit 8 is provided at the subsequent stage of the second FFT section 7. However, since the phase correction may be performed on the first output signal, in that case, the phase correction circuit 8 may be used. 8 may be provided in the subsequent stage of the first FFT unit 4.

<Second Preferred Embodiment> In the first preferred embodiment, time diversity utilizing a guard interval is realized by using two FFT units, but in the present preferred embodiment, one symbol having a storage capacity equal to or shorter than the symbol length is used. Memory and
An example in which a similar effect is obtained by using a double speed FFT unit that operates at double speed will be described.

FIG. 3 is a diagram showing a digital broadcast receiver according to this embodiment. Of the blocks shown in FIG. 3,
Elements having the same functions as those in FIG. 1 are designated by the same reference numerals. However, instead of outputting the above-mentioned first and second output signals, the time domain processing unit 3 outputs a period from an earlier one to a later one of the first and second output signals (for example, in FIG. Period from the FFT acquisition start point to the end of the second FFT acquisition period),
The received digital broadcast signal is output as the third output signal.

As shown in FIG. 3, the digital broadcast receiver according to the present embodiment has a symbol memory 10 having a storage capacity equal to or less than the symbol length, a double speed FFT section 11 for receiving the output of the symbol memory 10, and a double speed FFT. 2 from part 11
First and second memories 12 for storing two output signals
a and 12b.

The symbol memory 10 takes in the data of each symbol of the third output signal output from the time domain processing unit 3, reads it at the double speed at the time of reading, and outputs it to the double speed FFT 11 in the subsequent stage.

The double-speed FFT 11 time-divisionally transforms the portion of the third output signal corresponding to the first output signal into the frequency domain and the portion of the third output signal corresponding to the second output signal into the frequency domain. It is performed at the double speed of the first and second FFT units 4 and 7, and is output as the first and second output signals in the frequency domain, respectively.

The first memory 12a stores the first output signal from the double speed FFT 11 and the second memory 12b stores the double speed F.
The second output signal from FT11 is stored. And the first
The output of the memory 12a is given to the synthesis circuit 9, and the output of the second memory 12b is given to the phase correction circuit 9. Then, the synthesis circuit 9 synthesizes the output of the first memory 12a and the output of the phase correction circuit 9.

The other structure is similar to that of the digital broadcast receiver shown in FIG. In the present embodiment, the time domain processing unit 3, the symbol memory 10, the double speed FFT unit 11, and the first and second memories 12a and 12b can be regarded as a time domain-frequency domain signal conversion unit. .

Next, the operation will be described with reference to FIG. FIG. 4 is a diagram showing a part of a signal in the time domain of terrestrial digital television broadcasting and terrestrial digital audio broadcasting, the operation of the symbol memory 10, and the data acquisition period of the double speed FFT unit 11.

As shown in FIG. 4, the time domain processed digital broadcast signal is input to the symbol memory 10 from a time point corresponding to the first FFT acquisition start point in the first FFT section 4 of the first embodiment. It And
Second FFT in second FFT section 7 of the first embodiment
Signal acquisition is maintained until a point corresponding to the end of the acquisition period.

Here, the storage capacity of the symbol memory 10 is
The data length of 1 symbol is not necessarily required. That is, the symbol memory 10 may have a storage capacity such that the data length of the total period of the time difference X and the main signal SG can be stored as in the symbol memory operation period in FIG.

The symbol memory 10 is a double speed FFT section 11
First, in the first FFT unit 4 of the first embodiment,
The data of the number of FFT points corresponding to the FFT acquisition period of is supplied from the top in terms of time. Then, the double-speed FFT unit 11 performs the FFT processing at double speed during the operation period PD1 and outputs the first output signal in the frequency domain to the first memory 12a.

Next, the symbol memory 10 has a double speed FFT section 11 and a second FFT section 7 of the first embodiment.
Data of the number of FFT points corresponding to the FFT fetch period of is supplied from the position where the start address is offset by the time difference X. Then, the double speed FFT unit 11 performs the FFT process at double speed in the operation period PD2 subsequent to the operation period PD1, and outputs the second output signal in the frequency domain to the second memory 12b.

Then, the first and second memories 12a, 12a,
12b outputs the first and second output signals in synchronization with each other. Then, the phase correction circuit 8 performs phase correction on the second output signal, and the combining circuit 9 combines the first and second output signals.

According to the digital broadcast receiver of this embodiment, the double speed FFT section 11 makes the first output signal of the third output signal
The conversion of the part corresponding to the output signal into the frequency domain, and the second
The conversion to the frequency domain of the portion corresponding to the output signal is performed in time division, and the signals are output as the first and second output signals, respectively. Therefore, the time domain-frequency domain signal converter can be configured with one Fourier transform circuit, and the circuit configuration of the time domain-frequency domain signal converter can be reduced.

It is also possible to change the offset value of the time difference X in the symbol memory 10 to change the effect of time diversity.

<Third Embodiment> This embodiment is also a modification of the first embodiment, in which the second output signal output from the time domain processing unit 3 after being delayed by the time difference X is frequency-modulated to produce the first output. It is a digital broadcast receiver that superimposes on a signal and collectively performs FFT processing on both signals.

FIG. 5 is a diagram showing a digital broadcast receiver according to this embodiment. Among the blocks shown in FIG. 5,
Elements having the same functions as those in FIG. 1 are designated by the same reference numerals.

As shown in FIG. 5, in the digital broadcast receiver according to the present embodiment, the frequency bands of the first and second output signals are different from the second output signal output from the time domain processing unit 3. A modulator 13 that performs modulation so that they do not overlap,
And a delay unit 14 for adjusting the signal start timing of the first output signal output from the time domain processing unit 3 to the signal start timing of the second output signal.

Furthermore, the digital broadcast receiver according to the present embodiment is provided with the signal modulated by the modulator 13 and the delay unit 1.
And an output of the adder 15 is converted into the frequency domain, and the first and second output signals having different frequency bands are converted into the frequency domain. A double-length FFT unit 16 capable of processing the number of data that is doubled in the transmission mode is output. In this embodiment, the time domain processing unit 3 and the modulation unit 1
3, delay unit 14, adder 15, and double-length FFT unit 1
6 can be regarded as a time domain-frequency domain signal converter.

Next, the operation will be described with reference to FIGS. 6 and 7. FIG. 6 is a diagram showing a part of a signal in the time domain of terrestrial digital television broadcasting and terrestrial digital audio broadcasting, and a data acquisition period of double-length FFT section 16. FIG. 7 is a diagram showing the arrangement of the second output signal modulated by the modulator 13 and the first output signal in the frequency domain.

As in the case of the first embodiment, the time domain processing section 3 acquires data from the first FFT acquisition start point, outputs the first output signal, and outputs the second FF.
Data is acquired from the T capture start point and a second output signal is output. Of these signals, the first output signal is delayed by the delay unit 14 by the time difference X, and
The signal start timing of the output signal is matched with the signal start timing of the second output signal.

For the second output signal, the modulator 13
However, it is arranged at a frequency position where the frequency band does not overlap with the first output signal. Then, the adder 15 adds the delayed first output signal and the modulated second output signal. Since the frequency region is expanded, the data after this addition has double the number of data including both the first and second output signals.

A specific method for arranging the second output signal in the frequency domain is, for example, when the first output signal is located in the frequency band whose center frequency is fL1 as shown in FIG. The second output signal may be arranged in the frequency band having fL2 as the center frequency so as to be line-symmetric in the frequency domain with the frequency fLc as the axis of symmetry.

The frequency bands of the first and second output signals are
5.6M for digital terrestrial television broadcasting
Since it is Hz, in this case, for example, fL1 = 4 MHz,
It may be set as fLc = 8 MHz and fL2 = 12 MHz.

The first and second output signals after the addition have a double length F capable of processing the number of data double that of the transmission mode.
It is input to the FT unit 16. The double-length FFT unit 16 transforms the output of the adder 15 into the frequency domain, transforms the first and second output signals having different frequency bands into the frequency domain, and outputs them.

The first and second output signals are output from the double length FFT section 16 in synchronization with each other, and
The phase correction circuit 8 performs phase correction on the output signal, and the combining circuit 9 combines the first and second output signals.

According to the digital broadcast receiver of this embodiment, the adder 15 adds the second output signal modulated by the modulator 13 and the first output signal output from the delay unit 14, The double-length FFT unit 16 transforms the output of the adder 15 into the frequency domain, and transforms the first and second output signals having different frequency bands into the frequency domain and outputs them.

Therefore, it becomes possible to collectively perform the Fourier transform on the first and second output signals having different signal start timings in the time domain. If batch processing is possible, DSP
When the FFT processing is performed using (Digital Signal Processor) or the like, the control of the FFT unit becomes simple. Further, the time domain-frequency domain signal conversion section can be configured by one Fourier transform circuit, and the circuit configuration of the time domain-frequency domain signal conversion section can be reduced.

<Embodiment 4> In the present embodiment, in the time domain processing unit 3 in the digital broadcast receivers of Embodiments 1 to 3, a first FFT acquisition start point and a second FFT acquisition start point are set. Is to explain how to determine.

That is, the digital broadcast receiver according to the present embodiment has the first and second transmission modes according to the information on the transmission mode which defines the number of data points of the digital broadcast signal and the information on the data length of the guard interval. At least one of the FFT acquisition start points is changed. This makes it possible to maximize the time diversity effect according to the broadcasting system of the digital broadcasting signal.

FIG. 8 is a diagram showing a part of the configuration of the time domain processing unit 3 in the digital broadcast receiver according to the present embodiment. As shown in FIG. 8, the time domain processing unit 3
A table 17 in which the time difference X preset and optimized is recorded according to the transmission mode that defines the number of data points of the digital broadcast signal and the data length of the guard interval.
Equipped with. Furthermore, the time domain processing unit 3 performs logic when the adder 18, the symbol counter 19 that outputs the data position in the symbol, and the value of the symbol counter 19 and the first FFT acquisition start point value match. It is provided with a first equal comparator 20b for outputting and a second equal comparator 20a for outputting a logic when the value of the symbol counter 19 and the second FFT acquisition start point match. The information of the time difference X output from the table 17 is the information of the first to third embodiments.
It is also given to the phase correction circuit 8 in the digital broadcast receiver.

Next, the operation will be described with reference to FIG. FIG. 9 shows a combination of the number of signal data and guard intervals in each transmission mode and each time difference X at that time.
3 is a timing chart showing an example of the above.

The standards for terrestrial digital television broadcasting and terrestrial digital audio broadcasting both specify three transmission modes and four guard interval data lengths. Regarding the transmission mode, the number of data points is 2k (2048), 4k (4096), 8k
(8192) is defined, and the data length of the guard interval is 1/32 or 1/1 of the data length of the main signal.
Four are defined: 6, 1/8 and 1/4. Therefore, there are 3 × 4 = 12 combinations.

For example, FIG. 9 is a timing chart in the case of terrestrial digital television broadcasting. In the case of a 2k mode signal, the data length of the guard interval GI2k is 1/16 (= 128 points) of the data length of the main signal SG2k. )
In the case of a 4k mode signal, the data length of the guard interval GI4k is 1/8 of the data length of the main signal SG4k.
(= 512 points), in the case of the 8k mode signal, the data length of the guard interval GI8k is 1/4 (= 2048 points) of the data length of the main signal SG8k. The combination of the transmission mode and the data length of the guard interval is not changed during reception unless previously notified by the TMCC signal or the like. In each transmission mode, the time difference is X2k, X4k, X8.
different from k.

First FFT acquisition start point, second
It is possible to variously set the FFT acquisition start point of and the time difference between them.
A difference appears in the time diversity effect depending on the setting method. Of course, it is desirable to maximize the time diversity effect. Therefore, in the present embodiment, information on the time difference for each transmission mode and each guard interval data length, which has been optimized by performing experiments or the like, is recorded in the table 17 in advance. Then, the second FFT acquisition start point is set by referring to the information in the table 17. It should be noted that the first FFT acquisition start point is appropriately set from the calculation result of the correlation between the guard interval and the main signal on the time axis in the known time domain correlation circuit, as described in the following embodiments. Since this is done, we will not describe how to generate it here.

The information on the transmission mode and the information on the data length of the guard interval can be easily discriminated by the receiver itself, or are known by the storage means or the like provided in the receiver. Therefore, in order to optimize the effect of time diversity, the time difference X between the first FFT acquisition start point and the second FFT acquisition start point is varied according to the transmission mode and the data length of the guard interval.

The table 17 obtains the transmission mode information and the data length of the guard interval and selects and outputs the information of the time difference suitable for each transmission mode and each guard interval data length. The output time difference information is given to the phase correction circuit 8 and also to the adder 18.

The adder 18 adds the first FFT acquisition start point value signal and the time difference output from the table 17 to generate a second FFT acquisition start point value signal. The signal of the second FFT acquisition start point value is given to one end of the second equal comparator 20a.

The second equal comparator 20a compares the output value of the symbol counter 19 with the second FFT fetching start point value, and outputs a logic when they match.

Further, the signal of the first FFT acquisition start point value is given to one end of the first equal comparator 20b, and the first equal comparator 20b outputs the output value of the symbol counter 19 and the first FFT acquisition start point value. And are compared with each other, and if they match each other, the logic is output.

According to the digital broadcast receiver of the present embodiment, the time domain processing unit 3 of the digital broadcast receiver according to the information of the transmission mode and the data length of the guard interval,
The second FFT acquisition start point is changed. Therefore, it is possible to maximize the time diversity effect according to the broadcasting system of the digital broadcasting signal.
Further, even when the combination of the transmission modes of the terrestrial digital television broadcasting and the terrestrial digital audio broadcasting and the data length of the guard interval changes, the optimum time diversity can be realized.

In this embodiment, the hardware configuration using the table 17 in order to output the information on the time difference from the information on the data length of the guard interval and the information on the transmission mode has been exemplified. It is also possible to perform the same function as above by using a CPU (Central Processing Unit) for controlling the above to perform software processing so as to calculate the time difference from the information on the data length of the guard interval and the information on the transmission mode.

<Embodiment 5> This embodiment is a modification of the digital broadcast receiver according to Embodiment 4, and a part of the configuration of the time domain processing unit 3 shown in Embodiment 4 includes It further comprises a mechanism for varying the first FFT acquisition start point and the second FFT acquisition start point by using the delay profile obtained by the correlation between the guard interval and the original data of the latter half of the main signal. .

FIG. 10 is a diagram showing a part of the configuration of the time domain processing unit 3 in the digital broadcast receiver according to the present embodiment. As shown in FIG. 10, in addition to the configuration of FIG. 8, the time domain processing unit 3 further includes a time domain correlation circuit 2
1, a correction value creation circuit 22 and a multiplier 23.

The time domain correlation circuit 21 is a known circuit for detecting the correlation between a digital broadcast received signal and a delayed signal obtained by delaying the received signal by the period of the main signal SG. The correction value creation circuit 22 is, as described in detail below, a correlation signal output from the time domain correlation circuit 21, information on the first FFT acquisition start point, and the symbol counter 19.
Of the second FF by detecting the delay profile by receiving the information of
The correction value of the T capture start point is output. Multiplier 2
3 multiplies the correction value output from the correction value creation circuit 22 by the time difference data output from the table 17, and outputs the result to the adder 18.

FIG. 11 is a diagram showing the detailed structure of the correction value generating circuit 22. The correction value creation circuit 22 receives the correlation signal output from the time domain correlation circuit 21 and detects the peak thereof, and a peak detection circuit 22a, and receives the correlation signal and the detection result of the peak detection circuit 22a to determine the peak level. The level determining unit 22b, which receives the correlation signal and the detection result of the peak detection circuit 22a, detects the ratio of the peak value between a certain peak and the next peak of the correlation signal, D / U (Desire / Undesire). ) A delay detection unit 22d is provided which receives the determination results of the detection unit 22c and the level determination unit 22b and detects how much delay period exists from the peak of the correlation signal to the next peak. The peak detection circuit 22a, the level determination unit 22b, the D / U detection unit 22c, and the delay detection unit 22d as a whole have a function of specifying the waveform shape of the correlation signal output from the time domain correlation circuit 21.

Further, the correction value generation circuit 22 further outputs the detection result of the peak detection circuit 22a, the output of the delay detection unit 22d, the detection result of the D / U detection unit 22c, the first FFT acquisition start point value and the symbol counter signal. It also includes a numerical value calculation unit 22e that calculates the delay profile of the correlation signal and calculates the correction value of the time difference X.

Next, the operation will be described with reference to FIG. FIG. 12 shows a part of signals in the time domain of terrestrial digital television broadcasting and terrestrial digital audio broadcasting, a delayed signal obtained by delaying the received signal by the period of the main signal SG, and output from the time domain correlation circuit 21. Correlation signal, and
FIG. 6 is a diagram showing a data acquisition period of the first and second FFT units 4 and 7.

In terrestrial digital television broadcasting or terrestrial digital audio broadcasting, as described above, data having the same contents as the latter half of the main signal is added as a guard interval before the main signal to improve the interference correction capability. ing. Since the guard interval signal and the latter half of the main signal have the same content, the time domain correlation circuit 21 detects the break between the guard interval and the main signal by obtaining the correlation by the autocorrelation calculation (complex conjugate calculation). You can

In the signal shown as "correlation when there are few external factors" among the correlation signals in FIG. 12, the peak PK1 of the correlation signal appears at the break between the guard interval GI of the delay signal and the main signal SG. On the other hand, when multipaths occur in the transmission line and "leading waves" and "delayed waves" occur, this peak appears twice like PK2 and PK3, and the guard interval GI and the main signal SG It will be difficult to clearly identify the breaks in. The peak of the correlation signal can be detected by performing an autocorrelation calculation on a moving average for an appropriate period (a period having a maximum guard interval length).

The correlation detection in the time domain correlation circuit 21 is used to determine the first FFT acquisition start point. The first FFT acquisition start point is usually fixed when the receiver detects signal synchronization.

In this embodiment, the correlation detection in the time domain correlation circuit 21 is also used to determine the second FFT acquisition start point.

The output of moving average of the correlation signal output from the time domain correlation circuit 21 is the spread of WD or WA (the spread of this spread is delayed due to the influence of the multipath of the transmission line) as in the correlation signal shown in FIG. (Referred to as profile). Therefore, by analyzing the delay profile, it is possible to determine whether the multipath due to the delayed wave or the multipath due to the preceding wave has occurred in the transmission path.

When multipaths due to delayed waves occur,
In the time domain, signal interference is more likely to occur on the guard interval part side than the main signal part, so
It is desirable to set the second FFT acquisition start point late. On the other hand, when the multipath due to the preceding wave occurs, there is a high possibility that signal interference occurs on the main signal part side rather than the guard interval part in the time domain, so the second FFT acquisition start point should be set earlier. It is desirable to set. The arrow in FIG. 12 indicates this.

Utilizing this principle, the correction value creating circuit 22
Then, the direction and size of the delay profile are obtained from the output of the time domain correlation circuit 21, and the shape of the peak waveform of the correlation is specified. Then, the relationship between the shape and the second FFT acquisition start point is obtained based on the information of the first FFT acquisition start point and the symbol counter signal,
A correction value for moving the second FFT acquisition start point is generated.

This correction value is applied to the table 17 in the multiplier 23.
By multiplying the time difference X output from the second FF
The T capture start point can be controlled. Further, the result of multiplying this correction value may be given to the phase correction circuit 8 and used for phase correction.

That is, in the present embodiment, the time domain processing unit 3 determines the influence of multipath of the digital broadcast signal by calculating the correlation between the digital broadcast signal and the delayed signal obtained by delaying the digital broadcast signal, The second FFT acquisition start point is changed according to the influence of multipath.

Therefore, it is possible to maximize the time diversity effect according to the transmission path state of the digital broadcast signal without setting the time difference X in advance in anticipation of the transmission path state.

<Embodiment 6> This embodiment is a modification of the digital broadcast receiver according to Embodiment 1, in which the channel state is estimated from the pilot signal in the frequency domain, and based on this estimation information. The second FFT acquisition start point is changed.

FIG. 13 is a diagram showing a part of the configuration of the digital broadcast receiver according to the present embodiment. As shown in FIG. 13, in addition to the configuration of FIG. 1, this digital broadcast receiver further includes a pilot signal detection circuit 24 and a phase detection circuit 2.
5, delay circuit 26, phase error detection circuit 27, integration circuit 2
8. A phase correction value creation circuit 29 is provided.

The pilot carrier detection circuit 24 detects a specific pilot carrier from the frequency domain signal output from the synthesis circuit 9. The phase detection circuit 25 detects phase information from the pilot carrier detected by the pilot carrier detection circuit 24. The delay circuit 26 delays the phase information detected by the phase detection circuit 25. The phase error detection circuit 27 detects a phase error from the delayed phase information and the current phase information. The integrating circuit 28 integrates the phase error in the carrier direction and the symbol direction. Then, the phase correction value creation circuit 29 converts the value of the integration circuit 28 into a correction value.

Since the other structure is the same as that of the digital broadcast receiver according to the first embodiment, the description thereof will be omitted.

Next, the operation will be described. In terrestrial digital television broadcasting and terrestrial digital audio broadcasting, a TMCC pilot carrier for transmitting necessary data to a receiver and an AC (Auxiliary Channe) for a broadcasting station.
l) Pilot carriers and pilot carriers such as SP (Scattered Pilot) carriers used for channel estimation during synchronous modulation are transmitted at known positions.

This pilot carrier is DBPSK.
(Differential Binary Phase Shift Keying) is modulated, and one symbol conveys one bit of information. Further, the phase is multiplied by ± π depending on the position. Therefore, if the pilot signal at a known position is used and the phase is corrected and then compared with the neighboring signal, the phase error can be easily obtained.

Since the multipath signal is the delayed wave or the preceding wave added on both the gain and phase on the time axis, it can be detected as phase rotation on the frequency axis. That is, the transmission path state can be estimated by detecting the phase error between the pilot carriers, and the second FFT acquisition start point in the time domain can be controlled based on this estimation. Then, the optimum time diversity according to the transmission path condition can be realized.

Therefore, first, a known specific pilot carrier is detected by the pilot carrier detection circuit 24, and phase information is detected by the phase detector 25 from the detected pilot carrier. Then, the phase error detection circuit 27 detects a phase error from the phase information of the immediately preceding pilot carrier delayed by the delay circuit 26 and the current phase information. Then, the integration circuit 28 integrates in both the subcarrier direction and the symbol direction to detect an average phase error.

The phase correction value creating circuit 29 is composed of the integrating circuit 28.
A correction value for the second FFT acquisition start point is generated based on the signal from the multiplier 23, and the multiplier 23 shown in the fifth embodiment is used.
To enter.

That is, the digital broadcast receiver according to the present embodiment is provided with the phase error detection circuit 27 which detects the pilot signal to detect the phase error of the digital broadcast signal. Then, based on the information on the detected phase error, the time domain processing unit 3 changes the second FFT acquisition start point.

Therefore, it is possible to maximize the time diversity effect in accordance with the transmission path condition of the digital broadcast signal.

The digital broadcast receiver shown in FIG. 14 is a modification of this embodiment. In FIG.
A detection circuit for detecting a pilot signal to detect a phase error of a digital broadcast signal is provided with a transmission path estimation filter 30 in the frequency domain processing / synchronization / differential demodulation unit 5 or a power calculator 31 of each carrier and an inverse FFT It is configured by the circuit 33.

The transmission line estimation filter 30 is a filter for estimating the state of the transmission line by using the SP pilot carrier used in the synchronous demodulation. In addition, the power calculator 31
Is an arithmetic unit that determines the state of the transmission path by obtaining the power of each carrier during differential demodulation. The switch 32 selects whether the path to the inverse FFT circuit 33 is the transmission path estimation filter 30 or the power calculator 31 depending on whether synchronous demodulation or differential demodulation is performed.

Since the SP pilot signal is periodically inserted at a known position, it is possible to estimate the transmission path information by performing time filter processing and carrier filter processing in the frequency domain in synchronous demodulation. Also, at the time of differential demodulation, the SP carrier is not inserted, but DQPSK (Di
Since the quadrature phase shift keying (fferential quadrature) is used, the power is always constant, so the state of the transmission path can be estimated by calculating the power of each carrier.

The switch 32 switches between synchronous modulation and differential modulation, and the inverse FFT circuit 33 outputs the inverse FFT to the output of the transmission path estimation filter 30 or the power calculator 31 in units of symbols.
By applying the processing, the channel impulse response can be easily obtained. Therefore, this information is supplied to the phase correction value creation circuit 29
Then, the correction value of the time diversity can be obtained by performing the same processing as in FIG.

<Embodiment 7> This embodiment is a modification of the digital broadcast receiver according to Embodiment 1, and uses the pilot carrier signal to output the first output signal and the second output signal from the combining circuit 9. The ratio of synthesis of output signals is changed.

FIG. 15 is a diagram showing a part of the configuration of the digital broadcast receiver according to the present embodiment. As shown in FIG. 15, this digital broadcast receiver further includes pilot signal detection circuits 34a and 34b, a subtractor 35, a power calculator 36, and an integration circuit 37 in addition to the configuration of FIG.

The pilot carrier detection circuit 34a detects all pilot carriers from the frequency domain signal output from the first FFT section 4. The pilot carrier detection circuit 34b detects all pilot carriers from the frequency domain signal output from the phase correction circuit 8.
The subtractor 35 includes pilot carrier detection circuits 34a, 3a.
Both pilot carriers 4b are subtracted from each other. The power calculator 36 detects the power of the noise vector obtained by the subtraction. The integrating circuit 37 integrates the noise component contained in the pilot carrier in one symbol.

Since the other structure is the same as that of the digital broadcast receiver according to the first embodiment, the description thereof will be omitted.

Next, the operation will be described. First FF
The first output signal output from the T section 4 after conversion into the frequency domain and the second output signal output from the phase correction circuit 8 after conversion into the frequency domain have the same phase. .

If there is a difference between the two, it is the difference in the noise amount of each signal and the difference in the transmission line characteristics. Therefore, the vector of the difference between the two signals is obtained by obtaining the difference between the two by the subtractor 35. Considering that most of the vector components are noise vectors, the power of this signal is obtained by the power calculator 36.

Then, the signal power for one symbol is integrated by the integrator 37 to obtain the noise power, and when the noise power is large, the ratio of the synthesis of the first output signal and the second output signal in the synthesis circuit 9 is calculated. Change. Specifically, for example, the synthesis of the first and second output signals is interrupted and only the first output signal is selected.

With the above-described configuration, in the digital broadcast receiver of the present invention, the second FFT acquisition period may exceed one symbol period due to the state of the transmission path, the influence of the clock recovery circuit of the receiver, and the like. Because there is. In particular,
As shown in FIG. 16, a second FFT acquisition period has entered an adjacent symbol that precedes (x in the upper part of FIG. 16), or a second FFT acquisition period has entered an adjacent symbol that continues (( 16) in the middle part of FIG.

When these phenomena occur, intersymbol interference with adjacent symbols occurs, and the interfering portion becomes noise. This may deteriorate the reception performance.

However, as in the present embodiment, by observing the noise component of the difference between the first and second output signals, the synthesizing circuit can be adjusted so that the maximum performance can always be exhibited.

According to the digital broadcast receiver of this embodiment, the power calculator 36 calculates the power of the difference between the pilot signals of the first and second output signals, and the synthesis circuit 9
The ratio of combining the second output signal output from the phase correction circuit 8 and the first output signal output from the first FFT unit 4 is changed according to the calculation result of the power calculator 36.

Therefore, by detecting the difference in noise power between the first and second output signals and changing the combination ratio of the first and second output signals according to the magnitude of the noise, the transmission path state of the digital broadcast signal is changed. It is possible to maximize the time diversity effect according to the influence of clock reproduction in the receiver.

[0136]

According to the first aspect of the present invention, the phase correction circuit causes the frequency regions of the first and second output signals according to the time difference between one point and another point within the guard interval period. One of the first and second output signals is corrected so as to eliminate the phase difference at. Then, the combining circuit combines the output of the phase correction circuit and the output from the time domain-frequency domain signal section. Therefore, in the combined signal, the power of the signal increases by the time difference within the guard interval, and the signal power with respect to the noise power can be increased. As a result, C /
The N ratio is improved and the error resistance performance is improved. That is, a digital broadcast receiver that effectively uses the guard interval signal can be obtained. Further, by generating the first and second output signals, a time diversity effect can be obtained and demodulation performance can be improved.

According to the second aspect of the present invention, the first Fourier transform circuit transforms the first signal into the frequency domain, and the second Fourier transform circuit transforms the second signal into the frequency domain. Therefore, as compared with the case where the signal processing of both the first and second signals is performed by one Fourier transform circuit,
The load of signal processing in the frequency domain signal converter is small.

According to the invention described in claim 3, the time domain-frequency domain signal transforming section includes a Fourier transform circuit,
The Fourier transform circuit time-divisionally transforms the first signal into the frequency domain and the second signal into the frequency domain.
Therefore, the time domain-frequency domain signal converter can be configured with one Fourier transform circuit, and the circuit configuration of the time domain-frequency domain signal converter can be reduced.

According to the fourth aspect of the invention, the adder adds the signal modulated by the modulator and the signal output from the delay section, and the Fourier transform circuit adds to the output of the adder. The conversion into the frequency domain is performed, and the first and second signals having different frequency bands are converted into the frequency domain and output. Therefore, it is possible to collectively perform the Fourier transform on the first and second signals having different signal start timings in the time domain. Further, the time domain-frequency domain signal conversion section can be configured by one Fourier transform circuit, and the circuit configuration of the time domain-frequency domain signal conversion section can be reduced.

According to the invention described in claim 5, the time domain processing section changes another point at which the second signal starts in accordance with the information on the transmission mode and the information on the data length of the guard interval. Therefore, it is possible to maximize the time diversity effect according to the broadcasting system of the digital broadcasting signal.

According to the sixth aspect of the invention, the time domain processing section starts another point of the second signal in accordance with the calculation result of the correlation between the digital broadcast signal and the delayed signal obtained by delaying the digital broadcast signal. To change. Therefore, it is possible to maximize the time diversity effect according to the transmission path state of the digital broadcast signal.

According to the invention described in claim 7, the time domain processing section changes another point at which the second signal starts in accordance with the phase error detected by the detection circuit by the pilot signal in the frequency domain. . Therefore, it is possible to maximize the time diversity effect according to the transmission path state of the digital broadcast signal.

According to the invention described in claim 8, the power calculator calculates the power of the difference between the pilot signals of the first and second output signals, and the synthesizing circuit responds to the calculation result of the power calculator. , And changes the ratio of combining one of the first and second output signals output from the time domain-frequency domain signal converter and the other of the first and second output signals output from the phase correction circuit. Therefore, by detecting the difference in noise power between the first and second output signals and changing the combination ratio of the first and second output signals according to the magnitude of the noise, the transmission path state of the digital broadcast signal and the receiver It is possible to maximize the time diversity effect according to the influence of the clock reproduction in.

[Brief description of drawings]

FIG. 1 is a diagram showing a digital broadcast receiver according to a first embodiment.

FIG. 2 is a block diagram showing a part of signals in the time domain of terrestrial digital television broadcasting and terrestrial digital audio broadcasting, and first and second FFT sections 4 and 7 in the digital broadcasting receiver according to the first embodiment. It is a figure showing the data acquisition period of.

FIG. 3 is a diagram showing a digital broadcast receiver according to a second embodiment.

FIG. 4 is a diagram showing a part of a signal in a time domain of a terrestrial digital television broadcast and a terrestrial digital audio broadcast, an operation of a symbol memory 10, and a double speed FFT section 11 in the digital broadcast receiver according to the second embodiment. It is a figure showing the data acquisition period of.

FIG. 5 is a diagram showing a digital broadcast receiver according to a third embodiment.

FIG. 6 shows a part of a signal in the time domain of terrestrial digital television broadcasting and terrestrial digital audio broadcasting in the digital broadcasting receiver according to the third embodiment, and a data acquisition period of double length FFT section 16. It is the figure shown.

FIG. 7 is a diagram showing an arrangement in the frequency domain of a second output signal modulated by a modulator 13 and a first output signal in the digital broadcast receiver according to the third embodiment.

FIG. 8 is a diagram showing a part of the configuration of a time domain processing unit 3 in the digital broadcast receiver according to the fourth embodiment.

FIG. 9 is a timing chart showing an example of a combination of the number of signal data and guard intervals in each transmission mode and each time difference X at that time.

FIG. 10 is a diagram showing a part of the configuration of a time domain processing unit 3 in the digital broadcast receiver according to the fifth embodiment.

11 is a diagram showing a detailed configuration of a correction value creation circuit 22. FIG.

FIG. 12 In the digital broadcast receiver according to the fifth embodiment, a part of the signals in the time domain of the terrestrial digital television broadcast and the terrestrial digital audio broadcast, the received signal is delayed by the period of the main signal SG. FIG. 6 is a diagram showing a delay signal, a correlation signal output from the time domain correlation circuit 21, and a data acquisition period of the first and second FFT units 4 and 7.

FIG. 13 is a diagram showing a digital broadcast receiver according to a sixth embodiment.

FIG. 14 is a diagram showing another configuration example of the digital broadcast receiver according to the sixth embodiment.

FIG. 15 is a diagram showing a digital broadcast receiver according to a seventh embodiment.

FIG. 16 is a diagram showing a case where the second FFT acquisition period exceeds one symbol period.

FIG. 17 is a diagram showing a conventional digital broadcast receiver.

FIG. 18 is a diagram showing a part of a signal in a time domain of terrestrial digital television broadcasting and terrestrial digital audio broadcasting.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 tuner, 2 AD converter, 3 time domain processing section, 4 first FFT section, 5 frequency domain processing / synchronous / differential demodulation section, 6 error correction processing section, 7 2nd FF
T section, 8 phase correction circuit, 9 synthesis circuit, 10 symbol memory, 11x speed FFT section, 13 modulator, 14 delay circuit, 15 and 18 adder, 16x length FFT section, 17
Table, 19 symbol counter, 20a, 20b
Equal comparator, 21 time domain correlation circuit, 2
2 correction value creation circuit, 23 multiplier, 24, 34a, 34
b pilot signal detection circuit, 29 phase correction value generation circuit, 30 transmission path estimation filter, 31 each carrier power calculation circuit.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yasuo Matsunami             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. F term (reference) 5C025 DA01                 5K022 DD01 DD33

Claims (8)

[Claims] 1. A receiving unit capable of receiving a digital broadcast signal including a main signal and a guard interval having the same data content as a part of the main signal in a time domain, and a period of the guard interval receiving an output of the receiving unit. The digital broadcast signal received from one of the points is used as the first signal for a predetermined period, and the digital broadcast signal is received from the other point which is before or after the one point within the period of the guard interval for the predetermined period. As a second signal, and the time domain-frequency domain signal converter that individually converts the first and second signals into a frequency domain and outputs the first and second output signals, respectively, the time domain-frequency domain One of the first and second output signals output from the signal conversion unit is received, and the one point and the other point within the guard interval period A phase correction circuit that corrects the one of the first and second output signals so as to eliminate the phase difference in the frequency domain between the first and second output signals according to the time difference of A digital broadcasting receiver comprising: a synthesizing circuit for synthesizing the one of the first or second output signals and the other of the first or second output signals output from the time domain-frequency domain signal section. 2. The digital broadcast receiver according to claim 1, wherein the time domain-frequency domain signal transforming unit includes first and second Fourier transform circuits, and the first Fourier transform circuit is A digital broadcast receiver for converting the first signal into a frequency domain, and the second Fourier transform circuit converting the second signal into a frequency domain. 3. The digital broadcast receiver according to claim 1, wherein the time domain-frequency domain signal transforming unit includes a Fourier transform circuit, and the Fourier transform circuit shifts to a frequency domain of the first signal. And a conversion of the second signal into a frequency domain in a time division manner. 4. The digital broadcast receiver according to claim 1, wherein the time domain-frequency domain signal conversion section has a frequency band of both signals overlapping with one of the first and second signals. And a delay unit that adjusts the other signal start timing of the first and second signals to the one signal start timing, a signal modulated by the modulator, and output from the delay unit. A Fourier transform circuit, the Fourier transform circuit transforms an output of the adder into a frequency domain, and the Fourier transform circuit converts the output of the adder into a frequency domain.
And a digital broadcast receiver that converts the second signal into the frequency domain and outputs the converted signal. 5. The digital broadcast receiver according to claim 1, wherein the time domain-frequency domain signal conversion section includes a time domain processing section, and the time domain processing section is data of the digital broadcast signal. According to the information of the transmission mode that defines the number of points and the information of the data length of the guard interval, the second
A digital broadcast receiver that changes the other point at which a signal starts. 6. The digital broadcast receiver according to claim 1, wherein the time domain-frequency domain signal conversion unit includes a time domain processing unit, and the time domain processing unit includes the digital broadcast signal and the digital broadcast signal. A digital broadcast receiver that calculates a correlation with a delayed signal obtained by delaying, and changes the other point at which the second signal starts in accordance with the result. 7. The digital broadcast receiver according to claim 1, wherein the digital broadcast signal includes a pilot signal, and the pilot signal is detected to detect a phase error of the digital broadcast signal. Further comprising a detecting circuit, wherein the time domain-frequency domain signal converting section includes a time domain processing section, and the time domain processing section, in accordance with the phase error, the another point at which the second signal starts. A digital broadcast receiver that can be changed. 8. The digital broadcast receiver according to claim 1, wherein the digital broadcast signal includes a pilot signal, and the first domain output from the time domain-frequency domain signal converter. And a first detection circuit that detects the pilot signal from one of the second output signal, and a second detection circuit that detects the pilot signal from the other of the first and second output signals output from the phase correction circuit. Further comprising: a subtractor that subtracts the detection results of the first and second detection circuits, and a power calculator that calculates the power of the pilot signal from the calculation result of the subtractor, Depending on the calculation result of the calculator,
Changing a ratio of combining one of the first and second output signals output from the time domain-frequency domain signal converter and the other of the first and second output signals output from the phase correction circuit. Digital broadcast receiver.