JP2003078839A - Digital broadcasting receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a digital broadcasting receiver capable of receiving both television broadcasting and voice broadcasting while suppressing a circuit scale. SOLUTION: This digital broadcasting receiver makes a band of an output signal of a frequency conversion part 1010 to be a boundary frequency of a passband of an IF filter 1012 and makes a TMCC decoding part 1210 detect which voice broadcasting signal is between one-segment broadcasting and three- segment broadcasting in receiving the voice broadcasting signal. The frequency conversion part 1010 and a filter for voice are controlled so as to perform Fourier transformation in an FFT part 1208 about a bandwidth corresponding to a detected broadcasting method among bandwidths for one segment or three segments in accordance with detection results of the TMCC decoding part 1210.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital broadcast receiving apparatus, and more particularly, to a terrestrial digital broadcast receiving apparatus for receiving a signal modulated by an orthogonal frequency division multiplexing (OFDM) transmission system.

[0002]

2. Description of the Related Art In recent years, in a system for transmitting a video signal or an audio signal, an orthogonal frequency division multiplexing (OFD) has been proposed as a method excellent in high quality transmission and improvement in frequency effective rate.
M: Orthogonal Frequency Division Multiplex) system has been proposed.

The OFDM system is a modulation system in which a large number of subcarriers are set up within the band of one channel. For example,
MPE after converting analog TV signal to digital signal
G compresses the data. Byte interleaving and bit interleaving are performed to disperse the cause of error occurrence in the transmission line such as noise in this data signal.
(Quadrature Phase Shift Keying),
16QAM (Quadrature Amplitude Mod)
mapping according to the modulation method such as ulation).

The mapped data is subjected to time interleaving and frequency interleaving to disperse the cause of error occurrence in the transmission path such as fading, and then inverse Fourier transform (IFFT) is performed. Are frequency-converted to and transmitted.

On the receiving side, the operation opposite to that on the transmitting side is performed. FIG. 21 is a schematic block diagram showing the configuration of a conventional digital television receiver 8000.

Referring to FIG. 21, an antenna (not shown)
The high-frequency signal input (RF signal input) input from is input to the frequency conversion unit 8010. Frequency converter 801
At 0, the RF signal is down-converted to an intermediate frequency (IF frequency), a desired frequency is extracted by the IF filter 8012, then converted to a baseband signal by the down converter 8015, and input to the analog / digital conversion unit 8016. .

In the analog / digital converter 8016,
A signal of the real axis (hereinafter referred to as “I axis”) component (in-phase detection axis signal) and an imaginary axis (hereinafter referred to as “Q axis”) are used by converting the analog signal into a digital signal and using Hilbert transform or the like.
Signal) (a quadrature detection axis signal) is output to a fast Fourier transform unit (hereinafter referred to as “FFT unit”) 8017.

The FFT section 8017 performs a fast Fourier transform on the input signal, converts the time axis data into frequency axis data, and outputs the frequency axis data to the frequency deinterleave section 8018.

The frequency deinterleaving unit 8018 performs a process of restoring the frequency interleaving performed to compensate for the loss of the signal of the specific frequency due to the reflection of radio waves.

The output of the frequency deinterleave unit 8018 is given to the time deinterleave unit 8019, and the time deinterleave unit 8019 performs a process of restoring the time interleave applied for fading or the like.

The I-axis component signal and the Q-axis component signal subjected to the time deinterleaving are demapped by the demapping unit 802.
At 0, it is converted into a signal of 2 bits (in the case of QPSK), 4 bits (in the case of 16 QAM) or 6 bits (in the case of 64 QAM).

The demapped signal is subjected to Viterbi decoding using a convolutional code performed on the transmitting side after debiting the bit interleaving performed for the purpose of increasing error resilience in a bit deinterleaving unit 8021. Error correction is performed by the unit 8022.

The signal subjected to Viterbi decoding is subjected to byte interleaving performed for the purpose of increasing error tolerance, as in the bit interleaving unit.
After canceling in 23, Reed-Solomon decoding (hereinafter,
"RS decoding") is performed in the RS decoding unit 8024 to perform error correction.

The error-corrected signal is decompressed by the MPEG decoding unit 8025, converted into analog video and analog audio signals by the digital / analog conversion unit 8026, and then output.

On the other hand, terrestrial digital audio broadcasting is also OFDM
It is transmitted by the method. Since the basic configuration is received by a receiver similar to that of the terrestrial digital television device 8000, most of the receivers for receiving such terrestrial digital audio broadcasts are the same as the terrestrial digital television receiver and its configuration. It will be possible to share.

FIG. 22 shows a television / radio shared receiver 81 in which the configuration of the terrestrial digital television apparatus 8000 is modified so as to be compatible with terrestrial digital audio broadcasting.
It is a schematic block diagram which shows the structure of 00.

In the television / radio shared receiver 8100 shown in FIG. 22, audio IF filters 8013 and 8014 are added to the configuration of the digital broadcast television receiver 8000 shown in FIG. 21, and the outputs of these IF filters are added. Is provided to the down converter 8015.

In terrestrial digital audio broadcasting, this is 1
This is because 1-segment broadcasting and 3-segment broadcasting will be performed as described in the "Technical conditions for terrestrial digital audio broadcasting" published by the Ministry of Posts and Telecommunications on November 29, 999, which was announced by the Telecommunications Technology Council. .

Here, "1 segment broadcasting" means 6 /
This is a form in which one OFDM segment having a bandwidth of 14 MHz (about 429 kHz) is used for broadcasting, and "three-segment broadcasting" is a form in which broadcasting is performed using three adjacent OFDM segments.

Referring to FIG. 22, when television / radio shared receiver 8100 operates as an audio receiver, first, a signal of one segment is extracted by IF audio filter 8013, down converter 8015, analog The processes in the digital / digital conversion unit 8016 and the FFT unit 8017 are performed.

In the terrestrial digital video and audio, TMCC (Transmission and
Multiplexing Configuration Control) is included therein, and information about whether the audio broadcast has one segment or three segments is described therein. Here, this TMCC information is included in the central segment in the case of 3-segment broadcasting.

If it is determined by the TMCC decoding section 8028 that the TMCC information is extracted and the audio broadcast is one-segment broadcast, the IF audio filter 801.
When the subsequent processing is performed while 3 is still selected, and when it is determined that it is a three-segment audio broadcast,
The switch circuit 8030 is switched to the IF audio filter 8014 side to transmit the signal to the down converter 8015. After the down converter 015, reception is performed by almost the same processing as in the case of television broadcasting.

The different processing in video, 1 segment audio broadcasting and 3 segment audio broadcasting is mainly the speed of data processing.

FIG. 23 is a conceptual diagram showing a transmission frequency band of audio broadcasting. As an example, as shown in FIG. 23, consider a case where audio broadcasting is performed on a VHF channel and audio broadcasting 4-2 therein is received. Here, each of the VHF channels VHF4, VHF5, and VHF6 corresponds to one channel of television broadcasting.

FIG. 24 is a conceptual diagram showing an audio signal to be finally extracted by the IF filter.

Since the audio broadcast 4-2 is a three-segment broadcast, it is necessary to extract the signal in the band shown in FIG. 24 by an IF filter. However, at the beginning of reception, the receiver side has a three-segment broadcast. Cannot be recognized as For this reason, the receiver first receives as one-segment broadcasting.

At this time, the IF audio filter 8013 is selected as the IF filter. FIG. 25 is a diagram showing the output of the IF audio filter 8013.

As shown in FIG. 22, this signal is digitally converted by the analog / digital converter 8016, and the FFT unit 8017, TM is applied to the converted signal.
Corresponding signal processing is performed in CC decoding section 8028.

TMCC in TMCC decoding section 8028
As a result of the decoding, the television / radio shared receiver 8100 recognizes that the received audio signal is a 3-segment broadcast, and
The F audio filter is switched from the IF audio filter 8013 to the IF audio filter 8014.

FIG. 26 is a diagram showing the output of the IF audio filter 8014.

[0031]

[Problems to be Solved by the Invention] As described above,
In the terrestrial digital television broadcast / terrestrial digital audio broadcast shared receiver 8100, a total of three analog IF filters for video and audio are required as IF filters.

Therefore, there is a problem that the cost of the analog filter increases. In particular, in general,
These analog IF filters use external discrete components and require a circuit for switching such analog IF filters, which causes not only cost but also increase in circuit scale. It will also result.

The present invention has been made to solve the above problems, and its purpose is to provide an analog IF.
As a filter, it is to provide a digital broadcast receiving apparatus capable of receiving both a television broadcast and an audio broadcast by using only an IF filter for receiving a video broadcast.

[0034]

A digital broadcast receiving apparatus according to claim 1, wherein the digital broadcast receiving apparatus receives a video / audio broadcast signal and an audio broadcast signal modulated by an orthogonal frequency division multiplex transmission system, The audio broadcast signal is transmitted by using a predetermined number of carriers within a predetermined bandwidth as a unit and at least with N1 times and N2 times (N1, N2: natural numbers) bandwidths of the units, respectively. Frequency conversion means for converting the frequency of the received signal on the basis of the tuning instruction signal transmitted by any of the above broadcasting systems, and a pass band width for one channel of the video / audio signal, and the output of the frequency conversion means. Based on the first filter means for receiving and passing and the output of the first filter means,
An orthogonal frequency division multiplex transmission demodulation means for performing Fourier transform on a signal converted into a digital signal to demodulate an audio broadcasting signal is provided, and the orthogonal frequency division multiplex transmission demodulation means varies a band through which the digital signal is passed. And a decoding detection unit for detecting whether the audio broadcast signal is transmitted by the first or second broadcasting system. The control means further includes a control means for controlling, i) when receiving the audio broadcast signal, the decoding detection means sets the band of the output signal of the frequency conversion means as the boundary frequency of the pass band of the first filter means. Either the 1st or 2nd broadcasting system is detected, and ii) It is detected from the bandwidth of N1 times and N2 times the unit according to the detection result of the decoding detecting means. For bandwidth corresponding to the transmission system,
The tuning instruction signal and the second filter means are controlled so that the Fourier transform is performed.

A digital broadcast receiving apparatus according to claim 2 is
In addition to the configuration of the digital broadcast receiving apparatus according to claim 1,
The orthogonal frequency division multiplex transmission demodulation means includes an analog / digital conversion means for outputting a signal converted into a digital signal based on the analog signal output from the first filter means,
Further comprising Fourier transform means for receiving the output of the second filter means and performing a Fourier transform, wherein the second filter means receives the output of the analog-digital converter means,
The control means controls the second filter means so that a signal having a bandwidth corresponding to the detected broadcasting system passes through.

A digital broadcast receiving apparatus according to claim 3 is
In addition to the configuration of the digital broadcast receiving apparatus according to claim 1,
The control unit sets the lower limit of the band of the output signal of the frequency conversion unit to the lower limit frequency of the pass band of the first filter unit when receiving the audio broadcast signal.

A digital broadcast receiving apparatus according to a fourth aspect is
A digital broadcast receiving apparatus for receiving a video / audio broadcast signal and an audio broadcast signal modulated by an orthogonal frequency division multiplex transmission system, wherein the audio broadcast signal has a predetermined number of carriers within a predetermined bandwidth as a unit, And at least the unit N1
Double and N2 times larger than N1 (N1, N2: natural numbers)
A first filter means that is transmitted by either of the first and second broadcasting systems that respectively transmit in the bandwidth of 1), has a pass bandwidth of one channel of the video and audio signal, and passes the received signal; , Orthogonal frequency division multiplex transmission for performing Fourier transform on the signal converted into the digital signal based on the output of the first filter means to demodulate the audio broadcast signal, and orthogonal frequency division multiplex transmission The demodulation means includes a second filter means for varying a band for passing a digital signal and a first broadcast audio signal.
And a second broadcast system, the decoding detection means for detecting which is being transmitted, further comprising a control means for controlling the operation of the digital broadcast receiving apparatus, wherein the control means is i) audio broadcasting At the time of signal reception, the pass band width of the second filter means is set as the band width of the first broadcasting system,
The decoding detection means is caused to detect which one of the first and second broadcasting methods is used, and ii) the detected broadcasting method out of the bandwidth of N1 times and N2 times the unit according to the detection result of the decoding detection means. The second filter means is controlled so that the Fourier transform is performed for the bandwidth corresponding to.

A digital broadcast receiving apparatus according to a fifth aspect is
In addition to the configuration of the digital broadcast receiving apparatus according to claim 4,
The orthogonal frequency division multiplex transmission demodulation means includes an analog / digital conversion means for outputting a signal converted into a digital signal based on the analog signal output from the first filter means,
It further includes a Fourier transform unit for receiving the output of the second filter unit and performing a Fourier transform, and a frequency transform unit for transforming the output of the Fourier transform unit into a predetermined frequency band.

[0039]

BEST MODE FOR CARRYING OUT THE INVENTION [First Embodiment] FIG. 1 is a digital broadcast receiving apparatus 1 according to a first embodiment of the present invention, which can be used for both terrestrial digital television broadcasting and terrestrial digital audio broadcasting.
000 is a schematic block diagram for explaining the configuration of 000.

Referring to FIG. 1, digital broadcast receiving apparatus 1
At 000, the RF signal received from the antenna (not shown) is tuned by the tuner 100, and the
It is given to each demodulation section 102.

The demodulated signal from the OFDM demodulator 102 is
The MPEG decoding unit 11 is provided to the transport stream decoder (hereinafter, referred to as TS decoder) 104.
Given to 0. That is, in the TS decoder 104,
The baseband signal is extracted from the selected channel.

The MPEG decoding unit 110 receives the data stream supplied from the TS decoder 104, and uses a random access memory (hereinafter referred to as RAM) 112 as a buffer for temporarily storing data, thereby making a video signal and an audio signal. Convert to.

Digital broadcast receiving apparatus 1000 further has a built-in storage device 1 for receiving and storing a signal from TS decoder 104 via data bus BS1.
48 and the receiving operation of the digital broadcast receiving apparatus 1000 according to a user's instruction from the outside, and performs a predetermined process on the data stored in the built-in storage device 148 via the data bus BS1. An arithmetic processing unit 144 for outputting, a ROM 140 for recording a program in the arithmetic processing of the arithmetic processing unit 144, and a RAM providing a memory area for the operation of the arithmetic processing unit 144.
142 and a high-speed digital interface 146 for inputting / outputting data between the data bus BS1 and the outside.
With. Built-in storage device 1 is not particularly limited.
As the 48 and the ROM 140, for example, a flash memory capable of electrically writing / reading data can be used.

After the arithmetic processing unit 144 processes the data stored in the built-in storage device 148 in accordance with an instruction given from the outside, the data is combined from the on-screen display processing unit 130. To the vessel 160.2.

The synthesizer 160.2 synthesizes the output from the MPEG decoding unit 110 and the output from the on-screen display processing unit 130, and then outputs the video output terminal 16
Give to 4. The output from the video output terminal 164 is given to the display unit 1004.

The digital broadcast receiving apparatus 1000 further receives the result data processed by the arithmetic processing unit 144 based on the data stored in the built-in storage device 148, and outputs the sound effect to the video output on the display unit. Etc. and receives the data processed by the arithmetic processing unit 144 based on the data accumulated in the built-in storage device 148 and the additional sound generator 120 for giving to the synthesizer 160.1. A PCM decoder 122 is provided which is generated and provided to the combiner 160.1.

The synthesizer 160.1 outputs the output from the MPEG decoding unit 110, the additional sound generator 120 and the PCM.
Upon receiving the output from the decoder 122, the synthesis result is given to the audio output terminal 162. The audio signal given to the audio output terminal 162 is output from the audio output unit 1002 as an audio signal.

The digital broadcast receiving apparatus 1000 is
A modem 150 for exchanging data with the outside and an IC card interface 152 for receiving information from an IC card may be provided as necessary.

Through the high-speed digital interface 146, for example, an external storage device 180 such as a HDD device for a home server and a remote controller (or keyboard or the like) 182 which is an external input device are connected to the data bus BS1.
Connected with.

Further, the digital broadcast receiving apparatus 1000 is
Display unit 100 that receives a video output and displays it on a display
4 or a voice output unit 1002 such as a speaker that receives a voice output signal and outputs a voice may be integrated.

FIG. 2 shows the tuner 100, O in FIG.
FDM demodulator 102, TS decoder 104 and MPE
3 is a block diagram showing a configuration of a code unit 110 in G. FIG.

Referring to FIG. 2, the tuner 100 has an RF
A frequency conversion unit 1010 that down-converts the RF signal input from the antenna into an intermediate frequency (IF frequency) according to the tuning instruction signal from the arithmetic processing unit 144.
And an IF filter 1012 for extracting a signal of a desired frequency from the output of the frequency conversion unit 1010, and a down converter 1014 for converting the output of the IF filter 1012 into a baseband signal.

The OFDM demodulation section 102 includes a tuner 100.
An analog-to-digital conversion unit 120 that receives an input signal that has become a baseband signal and converts it into a digital signal
2 is provided.

The OFDM demodulation unit 102 receives the output of the analog-to-digital conversion unit 1202, and in the case of receiving processing of digital audio broadcasting, an audio filter 1204 which is a digital filter for performing filtering processing as described later. , The output of the analog-to-digital converter 1202 and the output of the audio filter 1204,
A switch circuit 1206 that selectively outputs one of them based on C, an FFT unit 1208 that receives the output of the switch circuit 1206 and performs a fast Fourier transform, and an FFT.
The TMCC decoding unit 1210 that extracts TMCC information based on the output of the unit 1208, the frequency deinterleaving unit 1212 that receives the output of the FFT unit 1208, and performs the frequency deinterleaving process, and the frequency deinterleaving unit 12
And a time deinterleave unit 1214 which receives the output of 12 and performs a time deinterleave process.

The analog-to-digital converter 1202 converts the analog signal into a digital signal and separates the I signal and the Q signal by using the Hilbert conversion or the like and outputs them. The FFT unit 1208 performs a fast Fourier transform on the input signal, decomposes the data multiplexed on the time axis into frequency components, and outputs the data as frequency axis data to the frequency deinterleave unit 1212. The frequency deinterleave unit 1212 restores the frequency interleave performed to compensate for the loss of the specific frequency signal due to the reflection of radio waves.

The time deinterleave unit 1214 receives the output signal of the frequency deinterleave unit 1212 and restores the time interleave applied for fading resistance and the like.

OFDM demodulation section 102 further receives a demapping section 1220 receiving the output of time deinterleaving section 1214, a bit deinterleaving section 1221 receiving the output of demapping section 1220, and an output of bit deinterleaving section 1221. A Viterbi decoding unit 1222,
It includes a byte deinterleave unit 1223 that receives the output of the Viterbi decoding unit 1222 and an RS decoding unit 1224 that receives the output of the byte deinterleave unit 1223.

In demapping section 1220, the time-deinterleaved I and Q signals are combined with a data accuracy signal (distance between adjacent data in the I-axis direction and Q-axis direction). Converted to mapping data.

The demapping data is deinterleaved in the bit deinterleaving unit 1221 for the purpose of increasing error tolerance, and then the demapping data is decoded by the convolutional coding process performed on the transmission side. Is performed by the Viterbi decoding unit 1222 according to the soft decision. The signal subjected to Viterbi decoding is input to the byte deinterleave unit 1223, and the byte interleave performed for the purpose of increasing error tolerance is canceled as in the bit interleave. Then, the signal from which the byte interleaving has been canceled is input to the RS decoding unit 1224. The RS decoding unit 1224 performs Reed-Solomon (RS) decoding and error correction.

The error-corrected signal is then input to the MPEG decoding unit 110 via the TS decoder 104, the compressed signal is expanded by the MPEG decoder 1025, and converted into analog by the digital / analog conversion unit 1026. Finally, it is converted into analog video and analog audio signals.

FIG. 3 is a conceptual diagram for explaining the operation of digital broadcast receiving apparatus 1000 shown in FIGS. 1 and 2.

Hereinafter, with reference to FIG. 3, a case of listening to the audio broadcast 4-2 of the three-segment broadcast according to an instruction from the user will be described.

First, since it is unclear whether the audio broadcast is the 1-segment broadcast or the 3-segment broadcast, the digital broadcast receiving apparatus 1000 assumes that the audio broadcast is the 1-segment broadcast and the RF including the audio broadcast 4-2. In the frequency conversion unit 1010, the input is frequency-converted so that it becomes the lower limit frequency of the pass frequency band of the IF filter.

FIG. 4 is a diagram showing the frequency dependence of the pass characteristic of the IF filter 1012. As shown in FIG.
The F filter 1012 has a pass band width for one channel of television broadcasting.

FIG. 5 is a diagram showing the frequency spectrum of the signal after passing through the IF filter 1012.

Referring to FIGS. 3 and 4, the frequency conversion unit 10
In the spectrum after frequency conversion by 10, as shown in FIG. 5, the lowest frequency segment of the three segments is the lower limit frequency of the IF filter. For this reason,
For the lowest frequency segment, the IF filter 10
Due to the suppression by 12, the signal waveform is not perfect.

The signal after passing through the IF filter 1012 is processed in the down converter 1014 and the analog / digital converter 1202.

FIG. 6 shows the analog / digital converter 120.
It is a figure which shows the spectrum after digital conversion in FIG.

FIG. 7 is a diagram showing the frequency dependence of the pass characteristic of the audio filter 1204 shown in FIG.

The analog / digital converter 1 shown in FIG.
Of the signals after digital conversion in 202, the desired signal is the audio broadcast 4-2 of one segment.

Therefore, the audio filter 1204 having the characteristics shown in FIG. 7 extracts a signal for one segment.

FIG. 8 is a diagram showing a spectrum waveform as a result extracted by the audio filter 1204.

The FFT unit 1208 performs a fast Fourier transform process on this signal. Here, the signal extracted by the audio filter 1204 corresponds to the TV /
In the shared radio receiver 8100, the signal that has passed through the IF audio filter 8013 has the same frequency array as the signal input to the FFT unit 8017, so the subsequent processing is the same as when the audio IF filter 8013 is used. It will be.

When the audio broadcast 4-2 is a 1-segment broadcast, the reception may be continued as it is.

However, as described above, in the TMCC decoding unit 1210, the voice filter 1204 and the FFT unit 1
By performing a predetermined decoding process on the signal that has passed through 208, it is possible to identify that the received signal for audio broadcast 4-2 is a 3-segment signal.

According to the identification result of the TMCC decoding unit 1210, the arithmetic processing unit 144 instructs the frequency conversion unit 1010 and the voice filter 1204 to change to the 3-segment reception mode.

The processing after such an instruction is given will be described below. FIG. 9 is a conceptual diagram showing frequency characteristics of a signal output from the frequency conversion unit 1010 to the IF filter 1012.

The frequency converter 1010 converts the RF input into a “frequency for receiving three-segment broadcasting” which is higher than the frequency shown in FIG. Give to.

On the other hand, the frequency dependence of the pass characteristic of the IF filter 1012 is the same as in the case of FIG.

FIG. 10 is a diagram showing the output spectrum of the IF filter 1012. IF compared to the case of FIG.
Since the frequency of the signal input to the filter 1012 is high by one segment, the influence of the filtering does not appear on the signal waveform of the lowest frequency segment of the three-segment broadcast even after passing through the IF filter 1012.

The output signal of IF filter 1012 is processed in down converter 1014 and analog / digital conversion unit 1202.

FIG. 11 shows the analog / digital converter 12
It is a figure which shows the spectrum after the digital conversion in 02.

FIG. 12 shows the voice filter 1204 after being changed based on the instruction from the TMCC decoding section 1210.
It is a figure which shows the frequency dependence of the passage characteristic of.

As compared with the case shown in FIG. 7, in FIG. 12, the frequency dependence of the pass characteristic of the audio filter 1204 is such that the signal passes by one segment to a higher frequency side.

FIG. 13 is a diagram showing a spectrum waveform as a result extracted by the audio filter 1204.

As shown in FIG. 13, the audio filter 1204 whose characteristics are changed as shown in FIG. 12 extracts the signal of three segments from the desired signal of the three-segment audio broadcast 4-2. Be done.

The FFT unit 1208 performs a fast Fourier transform process on the signal that has passed through the voice filter 1204.

Here, the signal extracted by the audio filter 1204 has the same frequency array as the signal that has passed through the IF audio filter 8014 in the television / radio shared receiver 8100 of FIG. 22 and is input to the FFT unit 8017. Therefore, the subsequent processing is performed by the audio IF filter 8
The same processing as in the case of using 014 will be performed.

FIG. 14 is a schematic block diagram showing the structure of the audio filter 1204. As described above, the audio filter 1204 needs to change the pass band depending on whether the broadcast is one segment or three segments.

Therefore, the FI of a general-purpose digital filter is
R (Finite Impulse Response) bandpass filter 1
The arithmetic processing unit 144 calculates the coefficients of the filters 301 and 1303 based on the decoding result of the TMCC decoding unit 1210.
A desired frequency characteristic is obtained by operating as a low-pass filter by switching according to a signal given from.

Referring to FIG. 14, audio filter 120
4 includes two general-purpose FIR band pass filters 1301 and 1303 for the I axis and the Q axis. The audio filter 1204 further includes the bandpass filter 1
It is provided with filter coefficient ROMs 1302 and 1304 that respectively provide the coefficients of the filters 301 and 1303. Filter coefficient ROMs 1302 and 1304 are used for general-purpose FIR bandpass filters 1301 and 130.
The coefficient given to 3 is switched based on the decoding result of the TMCC decoding unit 1210.

In the above description, in order to facilitate the description, in the description of FIGS. 3 to 13, the description of the negative frequency is omitted.

In normal OFDM decoding, since sampling is performed at a predetermined sampling frequency, aliasing occurs and a negative frequency occurs. In such a case, however,
Basically, the processing can be performed with the same configuration as that of the present invention.

In the above description, the lower cutoff frequency of the IF filter is used, but the upper cutoff frequency can be used in the same configuration.

With such a configuration, it is possible to reduce the number of analog IF filters in the configuration of a digital broadcast receiving apparatus capable of receiving both normal digital television broadcast and digital audio broadcast. Become. Therefore, it is possible to reduce the cost of the receiver.

[Second Embodiment] FIG. 15 shows a tuner 100, O of a digital broadcast receiving apparatus according to a second embodiment of the present invention.
FDM demodulator 102, TS decoder 104 and MPE
FIG. 3 is a block diagram showing a configuration of a code unit 110 in G,
FIG. 3 is a diagram to be compared with FIG. 2 of the first embodiment.

The difference from the configuration of the digital broadcast receiving apparatus of the first embodiment shown in FIG. 2 is that in the first embodiment,
When receiving the audio broadcast, the frequency conversion unit 1010 first converts the band of the audio signal into the lower limit frequency or the upper limit frequency of the pass band of the IF filter 1012 according to the tuning instruction signal. In FIG. 15, the frequency converter 1010 is used even when receiving the audio broadcast.
The point is that the received RF audio signal is converted according to the tuning instruction signal so that the band corresponding to the band of each channel at the time of normal television broadcast reception becomes the pass band of the IF filter 1012.

Therefore, even when receiving an audio broadcast, a signal corresponding to one channel in the case of a television signal is input to the IF filter 1012.

Second, the audio filter 1204 is
The point is that it operates as a bandpass filter for passing an audio signal to be received according to the decoding result of the MCC decoding unit 1210.

Thirdly, a frequency axis converter 1230 for receiving the output of the FFT unit 1208 and performing a frequency changing process as described later is added.

Since the other parts of the structure shown in FIG. 15 are basically the same as those shown in FIG. 2, the same parts are designated by the same reference characters and the description thereof will not be repeated.

The operation will be described below. Also in the second embodiment, as in the first embodiment, the audio broadcast 4
Consider the case of listening to -2.

In the second embodiment, the IF filter 1
012 operates as a filter similar to that at the time of receiving a television broadcast. Therefore, the output of the IF filter 1012 is shown in FIG.
Is the same as. The down converter 1014 down-converts the signal that has passed through the IF filter 1012. For the output of the down converter 1014,
The analog-digital converter 16 performs digital conversion.

FIG. 16 shows the analog-digital converter 120.
It is a figure which shows the frequency spectrum of the signal after the process of 2 is completed.

Since the desired signal is the audio broadcast 4-2,
First, the audio filter 1204 extracts a signal for one segment. At this stage, the audio broadcast 4-2 is 1
Since the receiver does not know whether it is a segment broadcast or a three-segment broadcast, the signal for one central segment is extracted in this way initially.

FIG. 17 is a diagram showing the spectrum of the result extracted by the audio filter 1204.

This signal is subjected to fast Fourier transform in the same band as the television signal in the FFT section 1208, and then in the frequency axis transforming section 1230.
For example, the conversion is performed so that the lower limit frequency becomes 0.

FIG. 18 shows the frequency-axis converter 12 as described above.
FIG. 30 is a diagram showing a frequency spectrum of the signal after the frequency is changed in 30.

In this way, the frequency axis converter 1230
The signal converted in step S1 has the same frequency array as in the case of FIG. 8 of the first embodiment.

When the audio broadcast 4-2 is a 1-segment broadcast, the reception may be continued as it is.

However, in this case, the TMCC decoding unit 121
At 0, the received signal can be recognized as a 3-segment signal, and therefore an instruction is issued to the voice filter 1204 to widen its pass band width and the coefficient is changed to the 3-segment filter.

Such an audio filter 1204 may basically have the structure shown in FIG. However, the filter coefficients stored in the filter coefficient ROMs 1302 and 1304 are different from those in the first embodiment.

FIG. 19 is a diagram showing the frequency spectrum of the passing signal after the filter coefficient of the audio filter 1204 is changed.

In this way, according to the instruction from the TMCC decoding unit 1210, when the coefficient is changed so that the voice filter 1204 becomes a filter for three segments, the spectrum of the signal after passing through the voice filter 38. , As shown in FIG. 19, all the signals for three segments pass without being suppressed by the filter.

After this signal is subjected to fast Fourier transform in the same band as the television signal in the FFT section 1208, it is converted into a desired frequency in the frequency axis conversion section 1230.

FIG. 20 shows the frequency-axis converter 12 as described above.
FIG. 30 is a diagram showing a frequency spectrum of the signal after the frequency is changed in 30.

18 and 20, due to the difference between the one-segment broadcasting and the three-segment broadcasting, the frequency in FIG. 20 is shifted toward the higher side by one segment.

The signal converted by frequency axis converting section 1230 has the same frequency array as that shown in FIG. 13 in the first embodiment. Therefore, the subsequent processing may be the same as the case described in the first embodiment.

The audio filter 1204 needs to change the pass band according to 1-segment broadcasting / 3-segment broadcasting or a desired frequency. Therefore, a general-purpose FIR filter is used, and this can be realized with the same configuration as in the first embodiment.

In the above description, as in the first embodiment, the description of the case where a negative frequency exists is omitted. However, when such a negative frequency is generated, the band of the audio filter may be adapted to such a negative frequency as well, and the basic configuration uses the one described above. Is possible.

In the above description, in the "terrestrial digital television broadcasting", the video signal and the audio signal are broadcast,
In "Terrestrial digital audio broadcasting", the explanation has been made assuming that audio signals are broadcast, but for example, as signals transmitted in "Terrestrial digital TV broadcasting", in addition to video signals and audio signals, Data signals for so-called "data broadcasting" are also included. Similarly, the "terrestrial digital audio broadcast" may include a data signal for "data broadcast" in addition to the audio signal. Therefore, in the present invention, the "video / audio broadcast signal" is a term that can include such a data signal, and the "audio broadcast signal" is also a term that can include a data signal.

Furthermore, in the above description, terrestrial digital audio broadcasting in Japan is taken as an example, and "one segment broadcasting" means a mode in which one OFDM segment having a bandwidth of 6/14 MHz (about 429 kHz) is used for broadcasting. However, the present invention is not limited to such a case, and the number of carriers in a predetermined bandwidth within a predetermined number of O
The present invention can be applied to a broadcasting form in which FDM transmission is performed.

Therefore, more generally, if such "broadcast in which a predetermined number of carriers within a predetermined bandwidth are OFDM-transmitted" is defined as "one segment broadcast", such "predetermined band" is obtained. A "broadcast in which OFDM transmission is performed with a bandwidth of N times (N: natural number) with a predetermined number of carriers in the width as a unit" can be defined as "N segment broadcasting".
According to the present invention, in such a more general “N segment broadcasting”, at least two kinds of segment broadcasting for N are performed, and information corresponding to TMCC information is included in a segment other than the end segment. It is also applicable when

The embodiments disclosed this time are to be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and is intended to include meanings equivalent to the claims and all modifications within the scope.

[0125]

As described above, according to the present invention,
As an analog IF filter, an IF for receiving a video broadcast is used.
Both the television broadcast and the audio broadcast can be received by using only the filter, and a digital broadcast receiving apparatus with reduced cost and circuit scale can be realized.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a digital broadcast receiving apparatus 1000 according to a first embodiment of the present invention.

2 is a block diagram showing a configuration of a tuner 100, an OFDM demodulation unit 102, a TS decoder 104, and an MPEG code unit 110 in FIG.

FIG. 3 is a conceptual diagram for explaining an operation of digital broadcast receiving apparatus 1000 shown in FIGS. 1 and 2.

FIG. 4 is a diagram showing frequency dependence of the pass characteristic of the IF filter 1012.

FIG. 5 is a diagram showing a frequency spectrum of a signal after passing through an IF filter 1012.

FIG. 6 is a diagram showing a spectrum after digital conversion in an analog / digital conversion unit 1202.

7 is a diagram showing the frequency dependence of the pass characteristic of the audio filter 1204 shown in FIG.

FIG. 8 is a diagram showing a spectrum waveform of a result extracted by the audio filter 1204.

FIG. 9 illustrates a frequency conversion unit 1010 to an IF filter 10.
12 is a conceptual diagram showing frequency characteristics of a signal output to 12.

FIG. 10 is a diagram showing an output spectrum of an IF filter 1012.

11 is a diagram showing a spectrum after digital conversion in the analog / digital conversion unit 1202. FIG.

FIG. 12 is a diagram showing frequency dependence of the pass characteristic of the audio filter 1204 after being changed based on an instruction from the TMCC decoding unit 1210.

FIG. 13 is a diagram showing a spectrum waveform of a result extracted by the audio filter 1204.

FIG. 14 is a schematic block diagram showing the configuration of an audio filter 1204.

FIG. 15 is a block diagram showing a configuration of a tuner 100, an OFDM demodulation unit 102, a TS decoder 104, and an MPEG code unit 110 of a digital broadcast receiving apparatus according to a second embodiment of the present invention.

FIG. 16 is a diagram showing a frequency spectrum of a signal after the processing of the analog-digital conversion unit 1202 is completed.

FIG. 17 is a diagram showing a spectrum of a result extracted by the audio filter 1204.

FIG. 18 is a diagram showing a frequency spectrum of a signal whose frequency has been changed in the frequency axis conversion unit 1230.

FIG. 19 is a diagram showing a frequency spectrum of a passing signal after the filter coefficient of the audio filter 1204 is changed.

FIG. 20 is a diagram showing a frequency spectrum of a signal after the frequency is changed in the frequency axis conversion unit 1230.

FIG. 21 is a schematic block diagram showing the configuration of a conventional digital television receiver 8000.

FIG. 22 is a schematic block diagram showing the structure of a television / radio shared receiver 8100.

FIG. 23 is a conceptual diagram showing a transmission frequency band of audio broadcasting.

FIG. 24 is a conceptual diagram showing an audio signal to be finally extracted by the IF filter.

FIG. 25 is a diagram showing an output of the IF audio filter 8013.

FIG. 26 is a diagram showing an output of the IF audio filter 8014.

[Explanation of symbols]

100 tuner, 102 OFDM demodulator, 104
TS decoder, 110 MPEG decoding unit, 120 additional sound generator, 122 PCM decoder, 130 on-screen display processing unit, 140 ROM, 142
RAM, 144 arithmetic processing unit, 146 high-speed digital interface, 148 built-in storage device, 150
Modem, 152 card interface, 160.
1,160.2 synthesizer, 162 audio output terminal, 16
4 video output terminal, 180 external storage device, 100
0 digital broadcasting receiver, 1002 audio output unit, 1
004 display unit, 1010 frequency conversion unit, 1012
IF filter, 1014 down converter, 1202
Analog / digital conversion unit, 1202 audio filter, 1206 switch unit, 1208 FFT unit, 12
10 TMCC decoding unit, 1212 frequency deinterleaving unit, 1214 time deinterleaving unit, 1220
Demapping section, 1221 bit deinterleave section, 1222 Viterbi decoding section, 1223 byte deinterleave section, 1224 RS decoding section, 1025 MP
EG decoder, 1026 digital-analog converter, 1
230 Frequency axis converter.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04N 5/455 H04N 5/455 (72) Inventor Masayuki Yoshinaga 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Denki Co., Ltd. (72) Inventor Seiji Suzuki 2-5-5 Keihan Hondori, Moriguchi City, Osaka Prefecture Sanyo Denki Co., Ltd. F-term (reference) 5C025 AA23 AA25 AA29 AA30 BA25 DA01 DA05 5C026 DA21 5K022 DD01 DD33 5K061 BB06 BB07 BB17 CC45 CD08

Claims (5)

[Claims] 1. A digital broadcast receiving apparatus for receiving a video / audio broadcast signal and an audio broadcast signal modulated by an orthogonal frequency division multiplex transmission system, wherein the audio broadcast signal is a predetermined number within a predetermined bandwidth. The carrier is used as a unit, and the tuning instruction signal is transmitted by any one of the first and second broadcasting methods in which the bandwidth is at least N1 times and N2 times (N1, N2: a natural number) times as large as the unit, respectively. Frequency conversion means for converting the frequency of the received signal based on, and having a pass band width for one channel of the audiovisual signal,
First filter means for receiving and passing the output of the frequency converting means, and Fourier transforming a signal converted into a digital signal based on the output of the first filter means to demodulate the audio broadcast signal. An orthogonal frequency division multiplex transmission demodulation means for performing the orthogonal frequency division multiplex transmission demodulation means, wherein the orthogonal frequency division multiplex transmission demodulation means includes second filter means for varying a band through which the digital signal is passed, and the audio broadcast signal is Decoding detection means for detecting which of the first and second broadcasting schemes is being transmitted, further comprising control means for controlling the operation of the digital broadcast receiving apparatus, wherein the control means I) When the audio broadcast signal is received, the band of the output signal of the frequency conversion unit is set as the boundary frequency of the pass band of the first filter unit, and Decoding detection means is made to detect which of the first and second broadcasting systems is used, and ii) Depending on the detection result of the decoding detection means, one of N1 times and N2 times the unit bandwidth is detected. The tuning instruction signal and the second signal so that the Fourier transform is performed for the bandwidth corresponding to the broadcast system.
Digital broadcast receiving apparatus for controlling the filter means of the. 2. The orthogonal frequency division multiplexing transmission demodulation means outputs an analog signal converted into a digital signal based on the analog signal output from the first filter means.
The digital filter further includes a Fourier transform unit for receiving the output of the second filter unit and performing a Fourier transform, wherein the second filter unit receives the output of the analog-digital converter, The digital broadcast receiving apparatus according to claim 1, wherein the control unit controls the second filter unit so that a signal having a bandwidth corresponding to the detected broadcasting system passes. 3. The control means sets the lower limit of the band of the output signal of the frequency conversion means to the lower limit frequency of the pass band of the first filter means when the audio broadcast signal is received. Digital broadcasting receiver. 4. A digital broadcast receiving apparatus for receiving a video / audio broadcast signal and an audio broadcast signal modulated by an orthogonal frequency division multiplexing transmission system, wherein the audio broadcast signal is a predetermined number within a predetermined bandwidth. Is transmitted by any one of the first and second broadcasting methods in which the carrier is used as a unit, and at least N1 times as large as the unit and N2 times larger than N1 (N1, N2: natural number) are respectively transmitted, Has a pass band width for one channel of the audiovisual signal,
First filter means for passing a received signal, and an orthogonal frequency for demodulating the audio broadcast signal by performing a Fourier transform on the signal converted into a digital signal based on the output of the first filter means. Division multiplexing transmission demodulation means, the orthogonal frequency division multiplexing transmission demodulation means includes second filter means for varying a band for passing the digital signal, and the audio broadcast signal includes the first and the second. Decoding detection means for detecting which of the two broadcasting systems is being transmitted, further comprising control means for controlling the operation of the digital broadcast receiving apparatus, wherein the control means is: i) the audio When a broadcast signal is received, the passband width of the second filter means is set as the bandwidth of the first broadcast method, and the decoding detection means receives the first and second broadcasts. Ii) the bandwidth corresponding to the detected broadcasting format out of the bandwidth of N1 times and N2 times the unit, according to the detection result of the decoding detecting means, A digital broadcast receiving device for controlling the second filter means so that conversion is performed. 5. The orthogonal frequency division multiplexing transmission demodulation means outputs an analog signal converted into a digital signal based on the analog signal output from the first filter means.
It further includes digital converting means, Fourier transforming means for receiving the output of the second filter means and performing Fourier transform, and frequency converting means for transforming the output of the Fourier transforming means into a predetermined frequency band. The digital broadcast receiving apparatus according to claim 4.