JP2007251729A - Digital broadcast receiving apparatus and digital broadcast receiving method - Google Patents

Abstract

The present invention provides a digital broadcast receiving apparatus and a digital broadcast receiving method capable of simplifying the configuration and thus reducing power consumption and cost.
A frequency transition detection unit detects a degree of frequency transition of a received signal based on a transition amount from a specified value of a guard band frequency corresponding to one channel band including a segment to be received. The frequency correction unit 102 corrects the frequency of the received signal using the detection value obtained by the frequency transition detection unit.
[Selection] Figure 4

Description

The present invention relates to a mobile digital broadcast receiving apparatus and a digital broadcast receiving method having, for example, a digital television broadcast receiving function, and more particularly, to a digital broadcast receiving apparatus and a digital having improved means for correcting a shift in reception frequency. It relates to a broadcast receiving method.

In ISDB-T (Integrated Services Digital Broadcasting-Terrestrial), each broadcast channel band is divided into a plurality of (14) segments, and one of the plurality of segments is guarded between the broadcast channel bands. Broadcasting performed using a partial segment (1 segment) of 13 segments other than the guard band among the plurality of segments allocated as a band (no signal band portion between channels: the same in the following description) So-called One Seg (registered trademark) is also showing signs of widespread use. The outline of such broadcasting will be described next.

FIG. 5 is a diagram showing a frequency allocation situation in digital terrestrial broadcasting. 90MHz-7
Each channel exists in units of 6 MHz in the 70 MHz band. Among them, terrestrial digital broadcasting is
Basically, a UHF band channel is allocated. In addition, digital radio broadcasting (terrestrial digital audio broadcasting) is considered to be assigned to an empty channel in the VHF band. Therefore, when developing an LSI so that it can be commonly applied to terrestrial digital audio broadcasting that adopts a common system with terrestrial digital television broadcasting, the frequency band to be supported by the LSI is 90 MHz to 7 MHz.
It becomes the whole area of 70MHz.

FIG. 6 is a diagram illustrating frequency allocation related to a digital broadcast channel in the UHF band. One channel is allocated every 6 MHz, and OFDM (Orthogonal Frequency Division)
Multiplex) modulated channels are divided into 13 segments on the frequency axis. A segment that can be used for a mobile television receiver (portable television) is an area of about 432 KHz that is hatched in the figure and is located at the center of these 13 segments. In order to receive a mobile television service of one segment, it is necessary to extract this segment that exists every 6 MHz in the UHF band.

FIG. 7 is a channel layout diagram including the frequency allocation described with reference to FIG. As shown in the figure, digital radio broadcasting is performed using the central three segments in the other bands adjacent to each other with the guard band sandwiched by the band of the television broadcasting of one channel in which the central one segment is applied to the portable television. .

FIG. 8 is a diagram illustrating a band used for frequency correction in reception of a mobile TV service. Usually, the center three segments as shown in the figure used for broadcasting services are filtered, a known specific carrier signal is decoded, and a frequency shift is detected by detecting the boundary of each segment. Correction is performed.

FIG. 9 is a block diagram showing a general configuration of a portable television receiver. R received
RF signal processing is performed on the F input by the tuner unit 901, and the signal subjected to this processing is converted into a digital signal by the AD conversion unit 902. The converted signal (which is digital data but is referred to as appropriate in the following description) is an OFDM-modulated broadcast signal. This broadcast signal is demodulated by the OFDM demodulator 903 and restored to the original signal. To do.

Stable reception is achieved by feeding back the AGC control amount to the tuner unit 901 from the state of the received signal. The data after OFDM demodulation described above is subjected to error correction processing through a Viterbi decoding unit 904 and an error correction unit 905, and an MPEG transport stream (TS
Output to the image processing unit. A system controller 906 centrally manages the operations of the above-described units.

FIG. 10 is a block diagram of components related to frequency correction in OFDM demodulation section 903 in FIG. 10, an FIR filter (Finite-Duration Im, which is a digital filter) is applied to the digital signal (digital video data) supplied from the AD conversion unit 902 in FIG.
(Pulse Response Filter) 1001 removes noise, and then corrects frequency deviation through a frequency offset canceling unit 1002.

Also, the GI correlation processing unit 1 provided on the output side of the frequency offset canceling unit 1002
The output of 010 is the mode determination unit 1011, the synchronization adjustment unit 1012, and the frequency density estimation unit 1.
The frequency dense estimation unit 1013 generates a frequency dense estimation signal.

That is, since the correlation value is obtained from the processing result of the GI correlation unit 1010, the synchronization adjustment unit 1012 detects the position of the correlation peak in synchronization with the peak value of the correlation value, and then the frequency fine estimation unit 10
In step 13, the correlation peak positions are averaged to estimate the OFDM symbol boundary of the received signal (to obtain a frequency dense estimation signal).
The interval of the correlation value peak corresponds to the OFDM symbol length, and the mode determination unit 1011 can determine the mode because the symbol length and the mode that is the transmission signal parameter are associated with each other in the standard.

FFT in FFT processing unit 1003 subsequent to frequency offset canceling unit 1002
After demodulating the OFDM-modulated signal by the processing, the equivalent processing unit 1004 performs equalization processing. Thereafter, a differential demodulator 1005 is used to extract a known specific carrier signal that has been differentially modulated.
To perform differential demodulation. In this process, data of a known specific signal is also extracted. Using the extracted data of the known specific signal, the frequency rough estimation unit 1020 performs rough estimation, which is frequency estimation for each frame, to obtain a frequency rough estimation signal. The frequency coarse estimation signal and the frequency dense estimation signal described above are used to obtain a frequency. The frequency shift amount is fed back to the offset cancel unit 1002.

The frequency offset canceling unit 1002 executes frequency correction processing according to the frequency shift amount fed back as described above. Finally, the data separation unit 1006 separates the control signal and the video data, and the process proceeds to the next stage.
The above is an outline of reception frequency correction in so-called partial reception using a general partial segment.

As described above, the OFDM system is also adopted in partial reception, and when a frequency shift occurs due to fading or the like in the transmission path, the signal must be demodulated after correcting the frequency shift.
In an OFDM transmission apparatus having a TMCC (Transmission and Multiplexing Configuration Control) carrier, the TMCC carrier is demodulated from a received signal received, a relative carrier position of the demodulated TMCC carrier is detected, and a carrier based on the detected TMCC carrier position is detected. A specific technique for detecting the shift amount, that is, the above-described frequency shift has also been proposed (see, for example, Patent Document 1).

This proposal corresponds to a broadcasting system having a main data carrier for sending main data and a sub data carrier arranged at a predetermined random position for sending sub data. As data, CP (Continual Pilot) arranged for every 8 carriers
Carrier and TMCC (Transmission and Multiplex
ng Configuration Control) and AC (Auxilia) placed at a predetermined random position
ry Channel) carrier.

A received signal is converted to an IF signal, and then converted to a baseband signal.
/ D conversion, quadrature demodulated to I-axis signal and Q-axis signal, and FF of the orthogonally demodulated I-axis and Q-axis signals to FF
T (Fast Fourier Transform) processing, and the I-axis and Q-axis signals Fourier-transformed by the processing are TM
DQPSK (Dif
ferential quadrature phase shift keying) demodulation.

With respect to the TMCC carrier demodulated signal differentially demodulated as described above, the values obtained by sampling the demodulated data in one symbol period with a predetermined random arrangement position pattern of the TMCC carrier are all added. For each arrangement position pattern shifted by one carrier within a range of ± M carriers (for example, M = 20) from the carrier position,
The above addition processing is performed, and the carrier deviation amount is determined based on the result. However, the characteristic here is also characterized, and the frequency deviation received on the transmission line or the like is more than ± 2 carrier deviations. In this case, it is possible to correct normally and to improve the transmission tolerance.
JP 2005-130480 A (paragraphs 0013 to 0017, paragraphs 0025 to 0026, FIGS. 1 and 4)

In the general configuration described with reference to FIG. 10, a correlation value of a specific carrier signal must be stored and an averaging process must be performed, so that a large number of elements such as registers are required. Therefore, there is a problem that the circuit scale becomes large and power consumption increases.
Further, even the technique described in the above-mentioned Patent Document 1 complicates the configuration for detecting the frequency shift, increases the circuit scale as a whole, increases costs, and prevents power saving.

The present invention has been made in view of the above situation, and provides a digital broadcast receiving apparatus and a digital broadcast receiving method that can be simplified in configuration, and thus can save power and reduce costs. The purpose is that.

In order to solve the above-described problems, the present application proposes the following techniques.
(1) The channel band of each broadcast in the digital broadcast service is divided into a plurality of segments, and one segment of the plurality of segments is assigned as a guard band between the broadcast channel bands, and a part of the plurality of segments A digital broadcast receiving apparatus that receives a broadcast of a method using a segment, and receives a signal depending on a transition amount from a specified value of a guard band frequency corresponding to one channel band including a segment to be received. A digital broadcast receiving apparatus comprising: a frequency transition detecting unit that detects a degree of frequency transition of the signal; and a frequency correcting unit that performs frequency correction of a received signal using a detection value obtained by the frequency transition detecting unit. .

In the digital broadcast receiver of (1) above, the frequency transition detection unit relies on the amount of transition from the specified value of the guard band frequency corresponding to one channel band including the segment to be received, and the frequency of the received signal The degree of transition is detected, and the frequency correction unit performs frequency correction of the received signal using the detection value of the frequency transition detection unit. For this reason, simplification of a structure is achieved.

(2) The frequency transition detection unit includes a filter unit that extracts a carrier wave in a fixed band including a guard band of the one channel band and its adjacent channel band, and the fixed limit extracted by the filter unit. A guard band position detector that detects the position of the guard band on the frequency axis from the state of the carrier in the target band, the position of the guard band on the frequency axis detected by the guard band position detector, and the definition The digital broadcast receiving apparatus according to (1), comprising: a shift amount detection unit that detects a degree of frequency transition of the received signal based on a comparison with the value.

In the above (2) digital broadcast receiver, in the digital broadcast receiver of (1),
In the frequency transition detection unit, the filter means extracts a carrier wave in a fixed band including a guard band of one channel band responsible for broadcasting and its adjacent channel band, and extracts by the filter means by the guard band position detection unit. The position of the guard band on the frequency axis is detected from the state of the carrier wave in the certain limited band, and
The position on the frequency axis (actual position) detected by the guard band position detector by the deviation amount detector and the specified value (position on the frequency axis where the guard band should be originally)
Based on the comparison, the degree of frequency transition of the received signal is detected.

(3) The guard band position detection unit performs an FFT process on a carrier wave in a certain limited band extracted by the filter unit, and performs a detection process on the output of the FFT process unit A digital broadcast receiver according to (2), characterized in that the digital broadcast receiver is configured to include a detector.
In the digital broadcast receiver of the above (3), particularly in the digital broadcast receiver of (2), in the guard band position detector, with respect to the carrier wave in a certain limited band extracted by the filter means by the FFT processor. FFT processing is performed, and the detection unit performs FFT
A detection process is performed on the output of the processing unit.

(4) The digital broadcast receiver according to (2), wherein the certain limited band is set as a band corresponding to three segments.
In the digital broadcast receiver of (4) above, in particular, in the digital broadcast receiver of (2), a certain limited band is set as a band corresponding to three segments.

(5) The digital broadcast receiver according to (3), wherein the FFT processing unit is common to the FFT processing unit used for demodulating the received broadcast signal.
In the digital broadcast receiver of (5) above, the FFT processor is common to the FFT processor used to demodulate the received broadcast signal (for example, OFDM demodulation), particularly in the digital broadcast receiver of (3). Therefore, the configuration is further simplified.

(6) The channel band of each broadcast in the digital broadcasting service is divided into a plurality of segments, and one segment of the plurality of segments is assigned as a guard band between the broadcast channel bands, and a part of the plurality of segments When receiving a broadcast of a method using a segment, a transition amount from a specified value of a guard band frequency corresponding to one channel band including the segment to be received is detected, and depends on the detected transition amount. And correcting the frequency of the received signal.

In the digital broadcast receiving method of (6) above, the frequency of the received signal depends on the transition amount from the specified value of the guard band frequency (actual value) corresponding to one channel band including the segment to be received. The degree of transition is detected, and the frequency of the received signal is corrected using the detected value.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings to be referred to below, for the sake of convenience, the main part that is the subject of the description is exaggerated as appropriate, and other than the main part is appropriately simplified or omitted.

FIG. 1 is a block diagram showing a configuration of a main part of a digital broadcast receiving apparatus as an embodiment of the present invention. The block diagram shown in FIG. 1 is the same as that described with reference to FIG. 9 in the overall schematic configuration, and its OF in the digital broadcast receiving apparatus as an embodiment of the present invention.
2 shows a configuration of a DM demodulator.

In FIG. 1, an FIR filter (Finite-Duration Impu) which is a digital filter is applied to a digital signal (digital video data) similar to that supplied from the AD converter 902 of FIG.
lse Response Filter) 101, after removing noise, the frequency offset canceling unit 10
2 is used to correct the frequency shift.
Further, the output of the GI correlation processing unit 110 provided on the output side of the frequency offset canceling unit 102 as the frequency correction unit is supplied to the mode determination unit 111, the synchronization adjustment unit 112, and the frequency density estimation unit 113, and this A frequency density estimation signal is generated from the frequency density estimation unit 113.

That is, since the correlation value is obtained from the processing result of the GI correlation unit 110, the synchronization adjustment unit 112 synchronizes with the peak part of the correlation value to detect the position of the correlation peak, and then the frequency fine estimation unit 113 detects the correlation peak. The position is averaged and the OFDM symbol boundary of the received signal is estimated (a frequency dense estimation signal representing this estimated value is obtained).
The interval of the correlation value peak corresponds to the OFDM symbol length, and the mode determination unit 111 can determine the mode because the symbol length and the mode that is the transmission signal parameter are associated in the standard.

After demodulating the OFDM-modulated signal by the FFT processing in the FFT processing unit 103 at the subsequent stage of the frequency offset canceling unit 102, the equalization processing unit 104 performs equalization processing. Thereafter, the differential demodulation unit 105 performs differential demodulation processing in order to extract a known specific carrier signal that has been differentially modulated. The signal subjected to the differential demodulation process is separated into a control signal and video data by the data separation unit 106, and the process proceeds to the next stage.

In the conventional example described with reference to FIG. 10, the frequency rough estimation unit 1020 performs rough estimation, which is frequency estimation for each frame, using the extracted known data to obtain a frequency rough estimation signal. Although the frequency offset amount is fed back to the frequency offset canceling unit 1002 by the above-described frequency dense estimation signal, the frequency coarse estimating unit 1020 is complicated in such a configuration. Estimator 102
Regardless of 0, a rough frequency estimation signal is obtained by the frequency transition detection unit 120 having a simple configuration as will be described later with reference to FIG.

FIG. 2 is a block diagram showing the configuration of the frequency transition detection unit 120 in FIG. In FIG. 2, for a digital signal (digital video data) similar to that supplied to the FIR filter 101, a guard band between one channel band received by the digital broadcast receiving apparatus by the filter 121 and its adjacent channel band is obtained. A carrier wave in a certain limited band is extracted.

FIG. 3 is a diagram showing a certain limited band extracted by the filter 121 in FIG.
As shown in the figure, as a certain limited band, it is a band for three segments including the guard band region GI at the center, and on the time axis where the center frequency of the guard band should be originally located in the broadcasting service regulations. The position on the frequency axis is set so that the position of is coincident with the center of the band.

Returning to the description of FIG. The frequency transition detection unit 120 detects the position of the guard band on the frequency axis from the state of the carrier in a certain limited band extracted by the filter 121 having the characteristics described with reference to FIG. Based on a comparison between the position detection unit 122 and the actual position on the frequency axis of the guard band detected by the guard band position detection unit 122 and the position as a prescribed value in the regulations, the frequency transition of the received signal And a deviation amount detection unit 123 that detects the degree.
The guard band position detection unit 122 described above includes an FFT processing unit 124 that performs FFT processing on a carrier wave in the above-described certain limited band extracted by the filter 121, and FFT.
And a detection unit 125 that performs a detection process on the output of the processing unit 124.

FIG. 4 is a diagram illustrating a state of signal processing in the guard band position detection unit 122 in FIG. FIG. 6A is a diagram showing a state where the FFT processing unit 124 performs FFT processing on a carrier wave in a certain limited band extracted by the filter 121 of FIG.
) Is a diagram illustrating a state in which the detection unit 125 performs detection on a carrier standing by FFT processing.

In the present invention, if the waveform detected by the detection unit 125 with respect to the carrier in this way occupies an equal width (band) from both sides in the above-mentioned fixed band (FIG. 3). There is no frequency shift in the reception frequency of the broadcast, and if it is biased to any one side, this bias corresponds to the degree of transition of the frequency of the received signal. Is output as a rough frequency estimation signal from the frequency transition detection unit 120, the entirety of which is shown in FIG.

This frequency coarse estimation signal is supplied to the frequency offset cancellation unit 102 in FIG. 1, and the frequency offset cancellation unit 102 relies on the frequency coarse estimation signal supplied in this way and the frequency fine estimation signal described above to correct the frequency. To do.
As described above, the present invention does not use a dedicated complex circuit that uses a known specific carrier signal as an example of TMCC, but only a general process such as filter, FFT, and detection, which is the basis of frequency correction. Since the data representing the amount of transition can be obtained, it is possible to realize a digital broadcast receiving apparatus with a low cost and low power consumption with a small circuit configuration.

Especially in the above, the FFT process part 1 of the frequency transition detection part 120 demonstrated with reference to FIG.
24 can be configured in common with the FFT processing unit 103 used for demodulating (for example, OFDM demodulating) the received broadcast signal as described with reference to FIG. 1, and thus configured. In some cases, further simplification is achieved.

The present invention described above divides a channel band of each broadcast in a digital broadcast service into a plurality of segments, assigns one of the plurality of segments as a guard band between the broadcast channel bands, and When receiving a broadcast of a method performed using a partial segment, the amount of transition from the specified value of the guard band frequency corresponding to one channel band including the segment to be received is detected, and the detected It is no doubt that this is a technical idea that is also considered as a digital broadcast receiving method characterized by correcting the frequency of the received signal depending on the amount of transition.

It is a block diagram showing the structure of the principal part of the digital broadcast receiver as embodiment of this invention. It is a block diagram showing the structure of the frequency transition detection part in FIG. FIG. 3 is a diagram illustrating a certain limited band extracted by a filter in FIG. 2. It is a figure showing the condition of the signal processing in the guard band position detection part in FIG. It is a figure showing the allocation condition of the frequency in terrestrial digital broadcasting. It is a figure showing the frequency allocation regarding the digital broadcast channel of a UHF band. FIG. 7 is a channel layout diagram including the frequency allocation of FIG. 6. It is a figure showing the zone | band used in order to perform frequency correction in reception of a portable television service. It is a block diagram showing the general structure of a portable television receiver. FIG. 10 is a block diagram of components related to frequency correction in the OFDM demodulator in FIG. 9.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 ... FIR filter 102 ... Frequency offset cancellation part 103 ... FFT processing part 104 ... Equivalent processing part 105 ... Differential demodulation part 106 ... Data separation part 110 ... GI correlation processing part 111 ... Mode determination part 112 ... Synchronization adjustment part 113 ... Frequency Dense estimation unit 12
0 ... frequency transition detection unit 121 ... filter 122 ... guard band position detection unit 123 ...
Deviation detector 124 ... FFT processor 125 ... detector 901 ... tuner 902 ...
AD converter 903 ... OFDM demodulator 904 ... Viterbi decoder 905 ... Error corrector 9
06 ... System controller 1001 ... FIR filter 1002 ... Frequency offset cancellation unit 1003 ... FFT processing unit 1004 ... Equivalent processing unit 1005 ... Differential demodulation unit 1006 ... Data separation unit 1010 ... GI correlation unit 1011 ... Mode determination unit 1012
... Synchronization adjustment unit 1013 ... Dense frequency estimation unit 1020 ... Rough frequency estimation unit

Claims (6)

Dividing the channel band of each broadcast in the digital broadcast service into a plurality of segments, assigning one of the segments as a guard band between the broadcast channel bands, and using a partial segment of the plurality of segments Digital broadcast receiving apparatus that receives a broadcast of a method performed in accordance with the frequency of the received signal depending on a transition amount from a specified value of a guard band frequency corresponding to one channel band including a segment to be received. A digital broadcast receiving apparatus comprising: a frequency transition detection unit that detects a degree of transition; and a frequency correction unit that performs frequency correction of a received signal using a detection value obtained by the frequency transition detection unit. The frequency transition detection unit includes a filter unit that extracts a carrier wave in a certain limited band including a guard band of the one channel band and the adjacent channel band, and a frequency band detection unit that is in the certain limited band extracted by the filter unit. A guard band position detection unit that detects a position on the frequency axis of the guard band from the state of the carrier wave, a position on the frequency axis of the guard band detected by the guard band position detection unit, and the specified value The digital broadcast receiving apparatus according to claim 1, comprising: a deviation amount detecting unit that detects a degree of frequency transition of the received signal based on the comparison. The guard band position detection unit includes an FFT processing unit that performs FFT processing on a carrier wave in a certain limited band extracted by the filter unit, and a detection unit that performs detection processing on the output of the FFT processing unit; The digital broadcast receiving apparatus according to claim 2, comprising: 3. The digital broadcast receiving apparatus according to claim 2, wherein the certain limited band is set as a band corresponding to three segments. 4. The digital broadcast receiving apparatus according to claim 3, wherein the FFT processing unit is common to the FFT processing unit used for demodulating the received broadcast signal. Dividing the channel band of each broadcast in the digital broadcast service into a plurality of segments, assigning one of the segments as a guard band between the broadcast channel bands, and using a partial segment of the plurality of segments When receiving a broadcast of a method performed in this manner, a transition amount from a specified value of a guard band frequency corresponding to one channel band including a segment to be received is detected, and reception is performed based on the detected transition amount. A digital broadcast receiving method characterized by correcting a signal frequency.

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