JP4740011B2 - OFDM receiver, terrestrial digital broadcast receiver, and terrestrial digital broadcast receiver tuner - Google Patents

Description

  The present invention relates to an OFDM receiver, a digital terrestrial broadcast receiver, and a digital terrestrial broadcast receiver tuner that receive digital terrestrial broadcast signals transmitted by an orthogonal frequency division multiplex (OFDM) transmission method.

  In recent years, OFDM transmission systems have attracted attention in digital audio broadcasting for mobiles and terrestrial digital television broadcasting. In this OFDM transmission system, on the transmitting side, digital data to be transmitted is modulated by a number of subcarriers (hereinafter referred to as “subcarriers”) orthogonal to each other, and inverse fast Fourier transform (IFFT) processing is performed to change the frequency domain to the time domain. This is a transmission method in which the signal is converted from the time domain to the frequency domain signal by fast Fourier transform (FFT) processing on the receiving side. When the number of subcarriers to be used is increased to several hundred to several thousand, the symbol period of each modulated wave becomes extremely long, so that the OFDM transmission system has a feature that it is hardly affected by multipath interference.

  ISDB-T (Integrated Services Digital Broadcasting-Terrestrial), a domestic terrestrial digital broadcast, employs hierarchical transmission that divides the 6 MHz bandwidth into 13 segments and allows the carrier modulation method to be changed for each segment. (See, for example, Non-Patent Document 1). Hierarchical transmission makes it possible to simultaneously provide a broadcast service for fixed devices and a broadcast service for portable devices. In terrestrial digital broadcasting, one segment located in the center of 13 segments is used for broadcasting for portable devices.

  On the other hand, in ISDB-TSB (integrated services digital broadcasting terrestrial for sound broadcasting), which is a domestic terrestrial digital audio broadcasting, broadcasting is performed in 8 or 13 segments depending on the channel to be used. A method called “concatenated transmission” is adopted in which a plurality of broadcast services are multiplexed to form 8 or 13 segments and broadcast (see, for example, Non-Patent Document 2). In the three-segment method, one service in the center and two segments on both sides have different hierarchical configurations and provide different services. Even in the three-segment system, the central one segment has a system specification that can be received by a receiver dedicated to one segment.

Furthermore, 8-segment digital audio broadcasting using two 1-segment broadcast services and two 3-segment broadcast services has been proposed (see Non-Patent Document 3, for example). With this method, various broadcasting services can be realized on the same channel.
The Institute of Image Information and Television Engineers Vol.52, No.11, pp1562-1566 (1998) The Journal of the Institute of Image Information and Television Engineers Vol.53, No.11, pp1467-1471 (1999) Summary Report (draft) of the “Discussion on the Future of Radio Broadcasting in the Digital Age”, Ministry of Internal Affairs and Communications, May 2005

 In the three-segment method, transmission is performed using 1297 carriers per symbol. However, when performing digital audio broadcast concatenation transmission, one IFFT corresponding to the number of carriers included in the segment to be concatenated is transmitted on the transmission side. Used to convert from a frequency domain to a time domain transmission signal.

 On the other hand, on the receiving side, in order to receive a multicarrier, the received signal is converted from the time domain to the frequency domain by using FFT to perform demodulation processing. In FFT, calculation processing is performed in units of 2 multipliers. Therefore, the minimum number of FFT points necessary for FFT processing of 1,297 subcarriers is 2048 points. Therefore, the processing efficiency is 1297/2048 = 63%, and there is a problem that redundant processing of nearly 40% is included.

  In addition, when performing 1-segment reception with a conventional 3-segment receiving terminal, it is possible to reduce power consumption by operating only the portion used for signal processing for one segment of the signal processing circuit for three segments. It is necessary to finely control the circuit. Since the circuit is finely controlled, the circuit configuration becomes complicated and the circuit scale and the like increase.

  As described above, when the conventional three-segment receiving terminal receives three segments, a redundant part is included in the FFT processing in the receiving apparatus due to the number of transmission carriers. Further, when receiving one segment, a complicated circuit configuration is required to operate only a necessary circuit and reduce power consumption.

  In view of the above problems, an object of the present invention is to provide an OFDM receiver, a terrestrial digital broadcast receiver, and a terrestrial digital broadcast receiver tuner that can reduce power consumption while suppressing an increase in circuit scale.

  To achieve the above object, a first feature of the present invention is an OFDM receiver for receiving an OFDM signal divided into a plurality of segments, and a plurality of segment demodulation circuits for OFDM-demodulating each of the plurality of segments. The gist of the present invention is an OFDM receiver including a control circuit that selects a segment demodulation circuit to be operated from among a plurality of segment demodulation circuits and stops the operation of a non-selected segment demodulation circuit.

  According to a second aspect of the present invention, in the OFDM receiver according to the first aspect, when operating at least two of the plurality of segment demodulation circuits, a segment combination circuit for combining the segments after OFDM demodulation is further provided. This is the gist.

  According to a third aspect of the present invention, in the OFDM receiver according to the first or second aspect, the plurality of segment demodulation circuits include a first segment demodulation circuit that OFDM-demodulates a basic segment of the plurality of segments, and a basic A second and third segment demodulation circuit for OFDM demodulating two extended segments having different segments and layers, and the control circuit operates the first segment demodulation circuit when receiving only the basic segment, The gist is to stop the operation of the three-segment demodulation circuit.

  According to a fourth aspect of the present invention, in the OFDM receiver according to the first or second aspect, each of the plurality of segments belongs to one of the plurality of broadcast services, and the control circuit includes the plurality of broadcast services. When only a part of the segment is received, the gist is to stop the operation of the segment demodulation circuit for OFDM-demodulating each segment belonging to a broadcast service that is not received.

  According to a fifth feature of the present invention, in the OFDM receiver according to the fourth feature, the plurality of segment demodulation circuits perform OFDM demodulation on the first basic segment, which is a basic segment of the plurality of segments belonging to the first broadcast service. A first segment demodulating circuit, second and third segment demodulating circuits for demodulating the second and third extended segments having different hierarchies from the first basic segment among a plurality of segments belonging to the first broadcasting service, respectively; A fourth segment demodulating circuit for OFDM-demodulating a second basic segment, which is a basic segment of a plurality of segments belonging to a broadcast service, and a fourth and a different hierarchy from the second basic segment among the plurality of segments belonging to the second broadcast service Fifth and sixth segment demodulation times for OFDM demodulation of the fifth extension segment, respectively And summarized in that comprises and.

  According to a sixth aspect of the present invention, there is provided an antenna for receiving a digital broadcast signal transmitted by an OFDM transmission method, a tuner for limiting a received signal from the antenna to a predetermined frequency band, and reception limited to a predetermined frequency band. An A / D converter that digitizes a signal, a plurality of segment demodulation circuits that respectively OFDM demodulate a plurality of segments included in the digitized reception signal, and a segment demodulation circuit that operates among the plurality of segment demodulation circuits A terrestrial digital broadcast receiving terminal comprising: a control circuit that selects and stops operation of a non-selected segment demodulation circuit; and an output device that performs at least one of video display and audio output based on a received signal after OFDM demodulation It is a summary.

  According to a seventh aspect of the present invention, there is provided a tuner for limiting a received signal to a predetermined frequency band, an A / D converter for digitizing the received signal limited to the predetermined frequency band, and a digitized received signal. A plurality of segment demodulation circuits for OFDM demodulating each of the plurality of included segments; and a control circuit for selecting a segment demodulation circuit to be operated from the plurality of segment demodulation circuits and stopping an operation of the non-selected segment demodulation circuit The gist is that it is a terrestrial digital broadcast receiving tuner.

  According to the present invention, it is possible to provide an OFDM receiver, a terrestrial digital broadcast receiver, and a terrestrial digital broadcast receiver tuner that can reduce power consumption while suppressing an increase in circuit scale.

  Next, first and second embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings in the first and second embodiments, the same or similar parts are denoted by the same or similar reference numerals.

(First embodiment)
In the first embodiment of the present invention, digital audio broadcasting using 8 or 13 segments can be received, and “1 segment reception” for receiving 1 segment and “3 segment reception for receiving 3 segments” are received. Will be described. As shown in FIG. 1, the terrestrial digital broadcast receiving terminal according to the first embodiment includes an antenna 1, a tuner 2 connected to the antenna 1, and an analog / digital (A / D) connected to the output of the tuner 2. Converter 3, branch circuit 4a connected to the output of A / D converter 3, demodulation circuit 100 connected to the output of branch circuit 4a, and error correction circuit 9 connected to the output of demodulation circuit 100 , A tuner 2, a branch circuit 4a, a demodulation circuit 100, and a control circuit 10a connected to the error correction circuit 9. The terrestrial digital broadcast receiving terminal further includes an output device (not shown) that performs at least one of video display and audio output. The output device includes an MPEG decoder and a display or speaker.

  The tuner 2 converts the OFDM signal received by the antenna 1 into an intermediate frequency (IF) signal and limits it to a predetermined frequency band. Specifically, the tuner 2 includes, for example, a radio frequency (RF) signal processing circuit connected to the antenna 1 and an IF signal processing circuit connected to the output of the RF signal processing circuit. The IF signal processing circuit is provided with two systems of IF filters for extracting one segment or three segments of frequency band from each segment of the OFDM signal.

  The control circuit 10a controls the tuner 2 to extract IF signals for three segments when receiving three segments, and controls the tuner 2 to extract IF signals for one segment when receiving one segment.

  The A / D converter 3 converts the band-limited analog OFDM signal AS from the tuner 2 into a digital OFDM signal BS. The branch circuit 4a performs a Hilbert transform on the digital OFDM signal BS obtained from the A / D converter 3, thereby deriving a quadrature component from the in-phase component and generating a complex OFDM signal CS. The complex OFDM signal CS is branched into a plurality by the branch circuit 4a. In the example of FIG. 1, the branch circuit 4a branches the complex OFDM signal CS into three.

  The demodulation circuit 100 includes a segment coupling circuit 8 and a plurality of (first to third) segment demodulation circuits 20 a to 20 c connected in parallel between the branch circuit 4 a and the segment coupling circuit 8. The first to third segment demodulation circuits 20a to 20c receive the complex OFDM signal CS, extract different segments from the complex OFDM signal CS, and perform OFDM demodulation on the extracted segments. Here, the “OFDM demodulation” is to establish a symbol synchronization, a frequency synchronization, and a clock synchronization, and after converting a received signal from the time domain to the frequency domain using FFT, It means the process to equalize.

  The control circuit 10a selects a segment demodulation circuit to be operated from the first to third segment demodulation circuits 20a to 20c, and stops the operation of the non-selected segment demodulation circuit. For example, the control circuit 10a stops the operation by cutting off the power supply to the non-selected segment demodulation circuit.

  Thus, by providing an independent segment demodulation circuit for each segment of the OFDM signal, the control circuit 10a can selectively operate each segment demodulation circuit, and low power consumption can be realized.

  The first segment demodulation circuit 20a demodulates the “basic segment”, which is the segment of the A layer that requires the highest reception quality, when receiving one segment and when receiving three segments. On the other hand, the second segment demodulating circuit and the third segment demodulating circuit are “first extension segment” and “second segment” which are segments of the B layer whose required reception quality is lower than the A layer when receiving the three segments. Each "extension segment" is demodulated.

  The control circuit 10a operates all of the first to third segment demodulation circuits 20a to 20c when receiving the three segments. On the other hand, at the time of receiving one segment, the control circuit 10a operates only the first segment demodulation circuit 20a and stops the operations of the second and third segment demodulation circuits 20b and 20c.

  The first segment demodulation circuit 20a includes a first band pass filter (BPF) 5a connected to the output of the branch circuit 4a, a first frequency conversion circuit 6a connected to the output of the first BPF 5a, and a first frequency conversion circuit 6a. And a first OFDM demodulation circuit 7a connected between the segment combination circuits 8. The first BPF 5a extracts the frequency band component DS of the basic segment from the branched received signal CS. The first frequency conversion circuit 6a converts the frequency band component DS of the basic segment into a baseband signal ES. The first OFDM demodulation circuit 7a performs OFDM demodulation on the baseband signal ES output from the first frequency conversion circuit 6a.

  The second segment demodulation circuit 20b includes a second BPF 5b connected to the output of the branch circuit 4a, a second frequency conversion circuit 6b connected to the output of the second BPF 5b, and between the second frequency conversion circuit 6b and the segment coupling circuit 8. And a second OFDM demodulation circuit 7b connected thereto. The second BPF 5b extracts the frequency band component FS of the first extension segment from the branched received signal CS. The second frequency conversion circuit 6b converts the frequency band component FS of the first extension segment into a baseband signal GS. The second OFDM demodulation circuit 7b performs OFDM demodulation on the baseband signal GS output from the second frequency conversion circuit 6b.

The third segment demodulation circuit 20c includes a third BPF 5c connected to the output of the branch circuit 4a, a third frequency conversion circuit 6c connected to the output of the third BPF 5c, and the third frequency conversion circuit 6c and the segment coupling circuit 8. And a third OFDM demodulator circuit 7c connected thereto. The third BPF 5c extracts the frequency band component HS of the second extension segment from the branched received signal CS. The third frequency conversion circuit 6c converts the frequency band component HS of the second extension segment into the baseband signal IS. The third OFDM demodulation circuit 7c performs OFDM demodulation on the baseband signal IS output from the third frequency conversion circuit 6c.

  The segment combining circuit 8 generates a demodulated signal JS by combining the segments demodulated by the first to third segment demodulating circuits 20a to 20c when receiving three segments. On the other hand, when one segment is received, the demodulated signal JS is transmitted to the error correction circuit 9 without performing the segment combining operation.

  The error correction circuit 9 performs deinterleave processing, Viterbi decoding, Reed-Solomon decoding, and the like on the demodulated signal JS, and generates an MPEG2-transport stream (TS) signal. The deinterleaving process is a process for returning various interleaving processes performed on the transmission side in order to remove a signal error caused by distortion in the transmission path.

  As described above, since different modulation and error correction are performed according to the layer of each segment, the control circuit 10a receives the A layer (basic segment) and the B layer (first and second extension segments) when receiving three segments. ), Different deinterleaving and Viterbi decoding are executed for each layer, and error correction corresponding to the A layer (basic segment) is executed when one segment is received.

  FIG. 2 shows an internal configuration example of the first to third OFDM demodulation circuits 7a to 7c in FIG. The first OFDM demodulation circuit 7a includes a first FFT circuit 71a that performs FFT processing on the baseband signal ES, and a first equalization circuit 72a that equalizes the output signal of the first FFT circuit 71a. Similarly, the second OFDM demodulation circuit 7b includes a second FFT circuit 71b that performs FFT processing on the baseband signal GS, and a second equalization circuit 72b that equalizes the output signal of the second FFT circuit 71b. The third OFDM demodulation circuit 7c includes a third FFT circuit 71c that performs an FFT process on the baseband signal IS, and a third equalization circuit 72c that equalizes the output signal of the third FFT circuit 71c.

  Each of the first to third FFT circuits 71a to 71c shown in FIG. 2 has a minimum number of points that can be subjected to FFT for one segment, that is, 512 points, and the first to third FFT circuits 71a to 71c. The total number of points is 1536 points. Accordingly, 512 points of redundant portions can be reduced as compared with the case where the minimum number of points at which FFT for three segments can be performed, that is, one 2048-point FFT circuit is used.

The control circuit 10a sets the control data for the tuner 2, the branch circuit 4a, the first to third segment demodulation circuits 20a to 20c, the segment coupling circuit 8, and the error correction circuit 9, so that the tuner 2, the branch circuit 4a, the first to third segment demodulation circuits 20a to 20c, the segment combination circuit 8, and the error correction circuit 9 are controlled. The control data is composed of a combination of a plurality of parameters as shown in Table 1, for example.

  The control circuit 10a preferentially sets the control data for 3 segment reception when 3 segment reception can be performed. Even when 3 segment reception can be performed, the control circuit 10a can perform an input operation or the like from the user. Control data for receiving one segment may be set. Alternatively, the control circuit 10a may be configured to monitor the remaining battery level and switch from receiving three segments to receiving one segment when the remaining battery level becomes a certain amount or less. It should be noted that by referring to the transmission control signal (TMCC signal) multiplexed on the OFDM signal, it is possible to automatically determine whether or not 3-segment reception can be performed.

  Next, the operation of the OFDM receiving apparatus according to the first embodiment will be described with reference to the flowchart shown in FIG.

  (A) First, the operation when receiving three segments will be described. Examples of frequency arrangement of each signal in the OFDM receiver shown in FIG. 1 are shown in FIGS.

  In step S101, the control circuit 10a determines that it is not one-segment reception, and the process proceeds to step S112.

  In step S112, the control circuit 10a sets control data for three-segment reception for the tuner 2, the branch circuit 4a, the first to third segment demodulation circuits 20a to 20c, the segment combination circuit 8, and the error correction circuit 9. To do. As a result, the tuner 2, the branch circuit 4a, the first to third segment demodulation circuits 20a to 20c, the segment combination circuit 8, and the error correction circuit 9 are set to the three-segment reception configuration.

In step S113, the tuner 2 down-converts the received signal from the RF band to the IF band, and 3 segments (basic segment, first extension segment, and second segment).
Limit the frequency band for the extended segment). As a result, the tuner 2 outputs an analog OFDM signal AS having the frequency arrangement shown in FIG. In FIG. 4A, the basic segment is arranged at the IF center frequency, the first extension segment is arranged adjacent to the low frequency side of the basic segment, and the second extension segment is arranged adjacent to the high frequency side of the basic segment. Yes. The analog OFDM signal AS is converted into a digital OFDM signal BS by the A / D converter 3. Further, the branch circuit 4a converts the digital OFDM signal BS into a complex OFDM signal CS and branches it into three systems.

  In step S114, as shown in FIG. 5A, the frequency band component DS of the basic segment is extracted from the complex OFDM signal CS by the first BPF 5a, and the frequency band component DS of the basic segment is basebanded by the first frequency conversion circuit 6a. Converted to signal ES. As shown in FIG. 5B, the frequency band component FS of the first extension segment is extracted from the complex OFDM signal CS by the second BPF 5b, and the frequency band component FS of the first extension segment is extracted by the second frequency conversion circuit 6b. It is converted into a baseband signal GS. As shown in FIG. 5C, the frequency band component HS of the second extension segment is extracted from the complex OFDM signal CS by the third BPF 5c, and the frequency band component HS of the second extension segment is baseband by the second frequency conversion circuit 6b. Converted to signal IS. Further, the first to third OFDM demodulation circuits 7a to 7c perform OFDM demodulation on the baseband signals ES, GS, and IS, respectively.

  In step S115, the segment combining circuit 8 combines the demodulated signals separated for each segment as shown in FIG. 6, and outputs the demodulated signal JS.

  In step S116, the error correction circuit 9 performs error correction on the demodulated signal JS for each layer to generate an MPEG2-TS signal.

  (B) Next, the case of 1-segment reception will be described. FIG. 7 shows an example of frequency arrangement of each signal in the OFDM receiver shown in FIG.

  In step S101, the control circuit 10a determines that one segment is received, and the process proceeds to step S102.

  In step S102, the control circuit 10a sets control data for receiving one segment in the tuner 2, the branch circuit 4a, the first to third segment demodulation circuits 20a to 20c, the segment combination circuit 8, and the error correction circuit 9. To do. As a result, the tuner 2, the branch circuit 4a, the first to third segment demodulation circuits 20a to 20c, the segment coupling circuit 8, and the error correction circuit 9 are set to a configuration for receiving one segment.

  In step S103, the tuner 2 down-converts the received signal from the RF band to the IF band and limits the frequency band for one segment (basic segment). As a result, the tuner 2 outputs an analog OFDM signal AS having the frequency arrangement shown in FIG. In FIG. 7A, a basic segment is arranged at the IF center frequency. The analog OFDM signal AS is converted into a digital OFDM signal BS by the A / D converter 3. The branch circuit 4a converts the digital OFDM signal BS into a complex OFDM signal CS of one segment.

  In step S104, as shown in FIG. 7C, the first frequency conversion circuit 6a converts the frequency band component CS for one segment into a baseband signal ES. The first OFDM demodulation circuit 7a performs OFDM demodulation on the baseband signal ES.

  In step S104, since the second and third segment demodulation circuits are not operating, the segment combination circuit 8 does not perform the segment combination and outputs the demodulated signal from the first segment demodulation circuit 20a to the error correction circuit 9. Timing adjustment is performed for output.

  In step S106, the error correction circuit 9 performs error correction for only the A layer on the demodulated signal JS to generate an MPEG2-TS signal.

  As described above in detail, according to the OFDM receiver according to the first embodiment of the present invention, it is possible to reduce redundant circuits by assigning independent segment demodulation circuits to each segment of the OFDM signal, and to reduce the Power consumption can be reduced.

(Second Embodiment)
In the second embodiment of the present invention, an OFDM receiver that can simultaneously receive two broadcast services will be described. In the following description of the second embodiment, differences from the first embodiment will be mainly described, and overlapping descriptions will be omitted.

  As shown in FIG. 8, the OFDM receiver according to the second embodiment is connected to the first and second demodulation circuits 100a and 100b connected to the output of the branch circuit 4b and the output of the first demodulation circuit 100a. This is different from FIG. 1 in that it includes a first error correction circuit 9a and a second error correction circuit 9b connected to the output of the second demodulation circuit 100b. Each of the first and second demodulation circuits 100a and 100b has a configuration similar to that of the demodulation circuit 100 shown in FIG.

  When only one broadcast service is received without receiving two broadcast services at the same time, the operation of either the first demodulation circuit 100a or the second demodulation circuit 100b is stopped and the same as in the first embodiment. The receiving operation is performed.

  The first demodulation circuit 100a and the first error correction circuit 9a are used when receiving the first broadcasting service of the one-segment method or the three-segment method. The second demodulator circuit 100b and the second error correction circuit 9b are used when receiving the second broadcast service of the 1-segment system or the 3-segment system. That is, it selectively controls whether or not to operate the first demodulation circuit 100a, the first error correction circuit 9a, the second demodulation circuit 100b, and the second error correction circuit 9b according to the broadcast service to be received. As a result, low power consumption of the OFDM receiver is realized.

  Specifically, the first demodulation circuit 100a includes first to third segment demodulation circuits 20a to 20c and a first segment coupling circuit 8a. The first segment demodulation circuit 20a performs OFDM demodulation on the first basic segment among the plurality of segments belonging to the first broadcast service. The second and third segment demodulating circuits 20b and 20c perform OFDM demodulation on the second and third extended segments having different hierarchies from the first basic segment among the plurality of segments belonging to the first broadcast service, respectively. When the first segment service circuit 8a receives three segments of the first broadcast service, the first segment combination circuit 8a combines the segments demodulated by the first to third segment demodulation circuits 20a to 20c.

  The second demodulation circuit 100b includes fourth to sixth segment demodulation circuits 20d to 20f and a second segment coupling circuit 8b. The fourth segment demodulation circuit 20d performs OFDM demodulation on the second basic segment among the plurality of segments belonging to the second broadcast service. The fifth and sixth segment demodulation circuits 20e and 20f perform OFDM demodulation on the fourth and fifth extension segments, which are different from the second basic segment, among the plurality of segments belonging to the second broadcast service, respectively. The second segment combining circuit 8b combines the segments OFDM demodulated by the fourth to sixth segment demodulating circuits 20d to 20f when receiving three segments of the second broadcast service.

  In the digital OFDM signal BS input to the branch circuit 4b, the segments of the first and second broadcast services are arranged in the frequency direction as shown in FIG. In FIG. 9, the IF center frequency is set between the first broadcast service and the second broadcast service. The first basic segment is disposed in the central frequency band of the first broadcast service, the first extended segment is disposed adjacent to the low frequency side of the first basic segment, and the second extended segment is disposed on the high frequency side of the first basic segment. Adjacent to each other. In addition, the second basic segment is arranged in the center frequency band of the second broadcast service, the third extension segment is arranged adjacent to the low frequency side of the second basic segment, and the fourth extension segment is the high frequency of the second basic segment. Adjacent to the side.

In order to simultaneously receive two broadcast services, the control circuit 10b, as shown in Table 2, (1) When receiving one segment of both the first and second broadcast services (hereinafter referred to as "first reception mode") ), (2) When receiving three segments of both the first and second broadcast services (hereinafter referred to as “second reception mode”), (3) receiving one segment of the first broadcast service, and receiving the second broadcast service by 3 When receiving segments (hereinafter referred to as “third reception mode”), (4) Total when receiving the first broadcast service with three segments and receiving the second broadcast service with one segment (hereinafter referred to as “fourth reception mode”) Four patterns of control data are held.

  Although the number of extracted segments in the tuner in the first reception mode is “6”, only the four segments of the first basic segment, the second extended segment, the third extended segment, and the second basic segment in FIG. It may be configured to extract.

  Next, the operation of the OFDM receiving apparatus according to the second embodiment will be described with reference to the flowchart shown in FIG.

  (A) First, the operation in the first reception mode will be described.

  In step S201, the control circuit 10b determines that both the first and second broadcast services are received, and the process proceeds to step S202. Whether or not to receive both the first and second broadcast services is selected by, for example, an input operation from the user.

  In step S202, the control circuit 10b determines that both segments of the first and second broadcast services are received, and the process proceeds to step S204.

  In step S204, the control circuit 10b includes the tuner 2, the branch circuit 4b, the first to sixth segment demodulation circuits 20a to 20f, the first and second segment coupling circuits 8a and 8b, and the first and second errors. Control data indicating the first reception mode shown in Table 2 is set for the correction circuits 9a and 9b.

  In step S205, the tuner 2 down-converts the received signal from the RF band to the IF band and limits the frequency band for six segments (first and second basic segments, first to fourth extension segments). The analog OFDM signal AS is converted into a digital OFDM signal BS by the A / D converter 3. Further, the branch circuit 4b converts the digital OFDM signal BS into a complex OFDM signal and branches it into six systems.

  In step S206, the frequency band component of the first basic segment is extracted from the complex OFDM signal by the first BPF 5a, and the frequency band component of the first basic segment is converted into a baseband signal by the first frequency conversion circuit 6a. Further, the frequency band component of the second basic segment is extracted from the complex OFDM signal by the fourth BPF 5d, and the frequency band component of the second basic segment is converted into a baseband signal by the fourth frequency conversion circuit 6d. As a result, the first and fourth OFDM demodulation circuits 7a and 7d perform OFDM demodulation on the baseband signals from the first and fourth frequency conversion circuits 6a and 6d, respectively.

  In step S207, the first segment combination circuit 8a performs timing adjustment or the like so as to output the demodulated signal from the first OFDM demodulation circuit 7a to the first error correction circuit 9a without executing segment combination. Similarly, the second segment combination circuit 8b performs timing adjustment and the like in order to output the demodulated signal from the fourth OFDM demodulation circuit 7d to the second error correction circuit 9b without performing segment combination.

  In step S208, the first and second error correction circuits 9a and 9b perform error correction only for the A layer on the supplied demodulated signals to generate MPEG2-TS signals, respectively.

  (B) Next, the operation in the second reception mode will be described.

  In step S201, the control circuit 10b determines that both the first and second broadcast services are received, and the process proceeds to step S202.

  In step S202, the control circuit 10b determines that one segment of both the first and second broadcast services is not received, and the process proceeds to step S213.

  In step S213, the control circuit 10b determines that both segments of the first and second broadcast services are received, and the process proceeds to step S214.

  In step S214, the control circuit 10b includes the tuner 2, the branch circuit 4b, the first to sixth segment demodulation circuits 20a to 20f, the first and second segment coupling circuits 8a and 8b, and the first and second errors. Control data indicating the second reception mode shown in Table 2 is set for the correction circuits 9a and 9b.

  In step S215, the tuner 2 down-converts the received signal from the RF band to the IF band and limits the frequency band for six segments. The analog OFDM signal AS is converted into a digital OFDM signal BS by the A / D converter 3. Further, the branch circuit 4b converts the digital OFDM signal BS into a complex OFDM signal and branches it into six systems.

In step S216, the frequency band component DS of the first basic segment is extracted from the complex OFDM signal by the first BPF 5a, and the frequency band component of the first basic segment is converted into a baseband signal by the first frequency conversion circuit 6a. Further, the frequency band component of the first extension segment is extracted from the complex OFDM signal by the second BPF 5b, and the frequency band component of the first extension segment is converted into a baseband signal by the second frequency conversion circuit 6b. The frequency band component of the second extension segment is extracted from the complex OFDM signal by the third BPF 5c, and the frequency band component of the second extension segment is converted into a baseband signal by the second frequency conversion circuit 6c . The frequency band component of the second basic segment is extracted from the complex OFDM signal by the fourth BPF 5d, and the frequency band component of the second basic segment is converted to the baseband signal by the first frequency conversion circuit 6d. The frequency band component of the third extension segment is extracted from the complex OFDM signal by the fifth BPF 5e, and the frequency band component of the third extension segment is converted to the baseband signal by the fifth frequency conversion circuit 6e. The frequency band component of the fourth extension segment is extracted from the complex OFDM signal by the sixth BPF 5f, and the frequency band component of the fourth extension segment is converted to the baseband signal by the sixth frequency conversion circuit 6f. Furthermore, the first to sixth OFDM demodulation circuits 7a to 7f perform OFDM demodulation on the respective baseband signals.

  In step S217, the first segment combination circuit 8a receives the demodulated signals from the first to third OFDM demodulation circuits 7a to 7c, combines the demodulated signals separated for each segment, and outputs them. The second segment combining circuit 8b receives the demodulated signals from the fourth to sixth OFDM demodulating circuits 7d to 7f, combines the demodulated signals separated for each segment, and outputs them.

  In step S218, the first and second error correction circuits 9a and 9b perform error correction on the A layer and the B layer for each demodulated signal, and generate MPEG2-TS signals, respectively.

  (C) Next, the operation in the third reception mode will be described.

  In step S201, the control circuit 10b determines that both the first and second broadcast services are received, and the process proceeds to step S202.

  In step S202, the control circuit 10b determines that one segment of both the first and second broadcast services is not received, and the process proceeds to step S213.

  In step S213, the control circuit 10b determines not to receive both segments of the first and second broadcast services, and the process proceeds to step S223.

  In step S223, the control circuit 10b determines that one segment of the first broadcast service is received and three segments of the second broadcast service are received, and the process proceeds to step S224.

  In step S224, the control circuit 10b includes the tuner 2, the branch circuit 4b, the first to sixth segment demodulation circuits 20a to 20f, the first and second segment coupling circuits 8a and 8b, and the first and second errors. Control data indicating the third reception mode shown in Table 2 is set for the correction circuits 9a and 9b.

  In step S225, the tuner 2 down-converts the received signal from the RF band to the IF band and limits the frequency band for six segments. The analog OFDM signal AS is converted into a digital OFDM signal BS by the A / D converter 3. Further, the branch circuit 4b converts the digital OFDM signal BS into a complex OFDM signal and branches it into six systems.

  In step S226, the frequency band component DS of the first basic segment is extracted from the complex OFDM signal by the first BPF 5a, and the frequency band component of the first basic segment is converted into a baseband signal by the first frequency conversion circuit 6a. The frequency band component of the second basic segment is extracted from the complex OFDM signal by the fourth BPF 5d, and the frequency band component of the second basic segment is converted to the baseband signal by the first frequency conversion circuit 6d. The frequency band component of the third extension segment is extracted from the complex OFDM signal by the fifth BPF 5e, and the frequency band component of the third extension segment is converted to the baseband signal by the fifth frequency conversion circuit 6e. The frequency band component of the fourth extension segment is extracted from the complex OFDM signal by the sixth BPF 5f, and the frequency band component of the fourth extension segment is converted to the baseband signal by the sixth frequency conversion circuit 6f. Further, the first, fourth, fifth, and sixth OFDM demodulation circuits 7a, 7d, 7e, and 7f perform OFDM demodulation on the respective baseband signals.

  In step S227, the first segment combination circuit 8a performs timing adjustment and the like so as to output the demodulated signal from the first OFDM demodulation circuit 7a to the first error correction circuit 9a without executing the segment combination. The second segment combining circuit 8b receives the demodulated signals from the fourth to sixth OFDM demodulating circuits 7d to 7f, combines the demodulated signals separated for each segment, and outputs them.

  In step S228, the first error correction circuit 9a performs error correction for only the A layer on the demodulated signal to generate an MPEG2-TS signal. The second error correction circuit 9b performs error correction for the A layer and the B layer on the demodulated signal to generate an MPEG2-TS signal.

  (D) Next, the operation in the fourth reception mode will be described.

  In step S201, the control circuit 10b determines that both the first and second broadcast services are received, and the process proceeds to step S202.

  In step S202, the control circuit 10b determines that one segment of both the first and second broadcast services is not received, and the process proceeds to step S213.

  In step S213, the control circuit 10b determines not to receive both segments of the first and second broadcast services, and the process proceeds to step S223.

  In step S223, the control circuit 10b determines that three segments of the first broadcast service are received and one segment of the second broadcast service is received, and the process proceeds to step S234.

  In step S234, the control circuit 10b includes the tuner 2, the branch circuit 4b, the first to sixth segment demodulation circuits 20a to 20f, the first and second segment coupling circuits 8a and 8b, and the first and second errors. Control data indicating the fourth reception mode shown in Table 2 is set for the correction circuits 9a and 9b.

  In step S235, the tuner 2 down-converts the received signal from the RF band to the IF band and limits the frequency band for six segments. The analog OFDM signal AS is converted into a digital OFDM signal BS by the A / D converter 3. Further, the branch circuit 4b converts the digital OFDM signal BS into a complex OFDM signal and branches it into six systems.

In step S236, the frequency band component DS of the first basic segment is extracted from the complex OFDM signal by the first BPF 5a, and the frequency band component of the first basic segment is converted into a baseband signal by the first frequency conversion circuit 6a. Further, the frequency band component of the first extension segment is extracted from the complex OFDM signal by the second BPF 5b, and the frequency band component of the first extension segment is converted into a baseband signal by the second frequency conversion circuit 6b. The frequency band component of the second extension segment is extracted from the complex OFDM signal by the third BPF 5c, and the frequency band component of the second extension segment is converted into a baseband signal by the second frequency conversion circuit 6c . The frequency band component of the second basic segment is extracted from the complex OFDM signal by the fourth BPF 5d, and the frequency band component of the second basic segment is converted to the baseband signal by the first frequency conversion circuit 6d. Further, the first to fourth OFDM demodulation circuits 7a to 7d demodulate each baseband signal, respectively.

  In step S237, the first segment combination circuit 8a receives the demodulated signals from the first to third OFDM demodulation circuits 7a to 7c, and combines and outputs the demodulated signals separated for each segment. The second segment combination circuit 8b performs timing adjustment and the like in order to output the demodulated signal from the fourth OFDM demodulation circuit 7d to the second error correction circuit 9b without performing segment combination.

  In step S238, the first error correction circuit 9a performs error correction on the A layer and the B layer on the demodulated signal to generate an MPEG2-TS signal. The second error correction circuit 9b performs error correction for only the A layer on the demodulated signal to generate an MPEG2-TS signal.

  (E) Finally, a case where only one broadcast service is received without simultaneously receiving two broadcast services will be described.

  In step S201, the control circuit 10b determines that both the first and second broadcast services are not received, and the process proceeds to step S203.

  In step S203, the control circuit 10b stops the operation of either the first demodulation circuit 100a or the second demodulation circuit 100b. Whether to stop the operation of either the first demodulation circuit 100a or the second demodulation circuit 100b is determined according to the broadcast service to be received.

  In step S100, the same receiving operation as in step S100 of FIG. 3 is executed.

  As described above, according to the OFDM receiver according to the second embodiment, it is possible to suppress an increase in power consumption and a circuit scale while simultaneously receiving a plurality of broadcast services.

(Other embodiments)
As described above, the present invention has been described according to the first and second embodiments. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  In the first embodiment described above, as shown in FIG. 11, the branch circuit 4a inputs one segment of the complex OFDM signal KS to the first frequency conversion circuit 6a without receiving it to the first BPF 5a when receiving one segment. It is good also as composition to do. This is because it is not necessary to use the first BPF 5a because the tuner 2 can extract only the frequency band component of the basic segment. Therefore, when one segment is received, in addition to the second and third segment demodulation circuits 20a and 20b, the operation of the first BPF 5a is stopped, so that the power consumption at the time of receiving one segment can be further reduced.

  In the second embodiment, the configuration in which two broadcast services are simultaneously received has been described. However, a configuration in which three or more broadcast services are simultaneously received may be employed. In the case of simultaneously receiving three or more broadcast services, third to n-th demodulation circuits are provided in addition to the first and second demodulation circuits 100a and 100b shown in FIG. 8 (n: an integer of 4 or more).

  The A / D converter 3, the branch circuit 4a, the demodulation circuit 100, the error correction circuit 9, and the control circuit 10a according to the first embodiment can be monolithically integrated on the same semiconductor chip and configured as a semiconductor integrated circuit.

  Similarly, the A / D converter 3, the branch circuit 4b, the first demodulation circuit 100a, the second demodulation circuit 100b, the first error correction circuit 9a, the second error correction circuit 9b, and the control circuit 10b according to the second embodiment. Can be monolithically integrated on the same semiconductor chip and configured as a semiconductor integrated circuit.

  Thus, it should be understood that the present invention includes various embodiments and the like not described herein. Therefore, the present invention is limited only by the invention specifying matters in the scope of claims reasonable from this disclosure.

It is a block diagram which shows the structural example of the OFDM receiver which concerns on 1st Embodiment of this invention. It is a block diagram which shows the internal structural example of the 1st-3rd OFDM demodulation circuit based on 1st Embodiment of this invention. It is a flowchart which shows the operation example of the OFDM receiver which concerns on 1st Embodiment of this invention. It is a schematic diagram which shows the frequency arrangement | positioning of the received signal at the time of 3 segment reception of the OFDM receiver which concerns on 1st Embodiment of this invention. It is a schematic diagram which shows the frequency arrangement | positioning of the received signal at the time of 3 segment reception of the OFDM receiver which concerns on 1st Embodiment of this invention. It is a schematic diagram which shows the frequency arrangement | positioning of the received signal at the time of 3 segment reception of the OFDM receiver which concerns on 1st Embodiment of this invention. It is a schematic diagram which shows the frequency arrangement | positioning of the received signal at the time of 1 segment reception of the OFDM receiver which concerns on 1st Embodiment of this invention. It is a block diagram which shows the structural example of the OFDM receiver which concerns on 2nd Embodiment of this invention. It is a schematic diagram which shows the frequency arrangement | positioning of the received signal at the time of 6 segment reception of the OFDM receiver which concerns on 2nd Embodiment of this invention. It is a flowchart which shows the operation example of the OFDM receiver which concerns on 2nd Embodiment of this invention. It is a block diagram which shows the structural example of the OFDM receiver which concerns on other embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Antenna 2 ... Tuner 3 ... A / D converter 4a, 4b ... Branch circuit 6a ... 1st frequency conversion circuit 6b ... 2nd frequency conversion circuit 6c ... 3rd frequency conversion circuit 6d ... 4th frequency conversion circuit 6e ... 1st 5 frequency conversion circuit 6f ... 6th frequency conversion circuit 7a ... 1st OFDM demodulation circuit 7b ... 2nd OFDM demodulation circuit 7c ... 3rd OFDM demodulation circuit 7d ... 4th OFDM demodulation circuit 7e ... 5th OFDM demodulation circuit 7f ... 6th OFDM demodulation circuit 8 ... Segment Coupling circuit 8a ... first segment coupling circuit 8b ... second segment coupling circuit 9 ... error correction circuit 9a ... first error correction circuit 9b ... second error correction circuit 10a, 10b ... control circuit 20a ... first segment demodulation circuit 20b ... Second segment demodulator circuit 20c ... Third segment demodulator circuit 20d ... Fourth segment demodulator circuit 20e 5th segment demodulation circuit 20f ... 6th segment demodulation circuit 71a ... 1st FFT circuit 71b ... 2nd FFT circuit 71c ... 3rd FFT circuit 72a ... 1st equalization circuit 72b ... 2nd equalization circuit 72c ... 3rd equalization circuit 100 ... Demodulator circuit 100a ... first demodulator circuit 100b ... second demodulator circuit

Claims (4)

An OFDM receiver for receiving an OFDM signal divided into a plurality of segments including a basic segment and an extended segment ,
A plurality of segment demodulation circuits corresponding to each of the plurality of segments, each having a bandpass filter for extracting the OFDM signal of the decoding target segment from the OFDM, and configured to demodulate the OFDM signal of the decoding target segment When,
A control circuit for selecting an operation target segment demodulation circuit from the plurality of segment demodulation circuits ,
The plurality of segments belong to either the first broadcast service or the second broadcast service,
The control circuit includes a first reception mode for receiving only the basic segment belonging to the first broadcast service and the second broadcast service, the basic segment belonging to the first broadcast service and the second broadcast service, and the extension. A second reception mode for receiving a segment; a third reception mode for receiving only the basic segment belonging to the first broadcast service and receiving the basic segment and the extended segment belonging to the second broadcast service; Receiving the basic segment belonging to the first broadcast service and the extension segment, and receiving only the basic segment belonging to the second broadcast service, and a fourth reception mode,
The control circuit selects the operation target segment demodulation circuit based on one of the first reception mode, the second reception mode, the third reception mode, and the fourth reception mode,
The OFDM receiving apparatus , wherein the control circuit stops the operation of non-operation target segments other than the operation target segment demodulation circuit . A segment combination circuit for combining the segments demodulated by the at least two operation target segment demodulation circuits when operating at least two operation target segment demodulation circuits among the plurality of segment demodulation circuits; The OFDM receiver according to claim 1. A digital terrestrial digital system comprising: the OFDM receiver according to claim 1; and an output device that performs at least one of video display and audio output based on the segment demodulated by the operation target segment demodulation circuit. Broadcast receiving terminal. A terrestrial digital broadcast receiver tuner comprising the OFDM receiver according to claim 1 .

Images