JP2008085878A - Television broadcast receiving device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make a device compact and inexpensive by composing a surface acoustic wave (SAW) filter portion of one stage of a SAW filter and obtaining the same filter characteristics as those of conventional devices. <P>SOLUTION: The device comprises an RF/IF conversion circuit section 21c which performs high-frequency processing and intermediate-frequency conversion processing for a received television broadcast signal of a selected channel; a band-pass filter section 22c which forms a next-stage circuit thereof to perform pass-band limiting filter processing for the output signal of the RF/IF converting circuit section 21c, and supplies the resulting signal to a receiving circuit 23c for analog television broadcast; and a surface acoustic wave filter section 24c, which performs pass-band limiting filter processing for the output signal thereof and supplies the resulting signal to a demodulating circuit 51c for digital television broadcast. The pass band for the band-pass filter section 22c is made narrow, in the range where information of analog television broadcast and on digital television broadcast passes through, and the surface acoustic wave filter section 24c is formed of a single stage of the surface acoustic wave filter. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a television broadcast receiving apparatus for receiving and processing analog television broadcasts and digital television broadcasts, and more particularly, to reducing the number of surface acoustic wave filters necessary for digital television broadcast reception processing.

  Conventionally, television broadcast receivers incorporated in video recording devices such as so-called television receivers, video tape recorders, DVD recorders, and HD (hard disk) recorders include NTSC analog television broadcasts and North American ATSC (Advanced Television Systems Committee). ) Some perform reception processing for both broadcasting and digital television broadcasting such as terrestrial digital broadcasting in Japan.

  A television broadcast receiving apparatus that performs reception processing of the analog television broadcast and the digital television broadcast is configured as shown in FIG.

  3 receives a tuner module 2a at the next stage of an antenna 1a, a surface acoustic wave filter (hereinafter, the surface acoustic wave filter is referred to as a SAW filter) module 3, and an analog television broadcast having an independent module configuration. The circuit 4 and a final-stage module 5a including a digital broadcast demodulating circuit 51a are provided, and each of the modules 2a, 3, 4, 5a is formed of a shielded individual board unit.

  The tuner module 2a includes an RF / IF conversion circuit unit 21a that performs high-frequency reception processing and intermediate frequency conversion processing on the received television broadcast signal of the selected channel, and an analog bandpass filter (hereinafter referred to as BPF). ) Portion 22a, and a television broadcast signal (RF signal) of a channel selected for analog television broadcasting or digital television broadcasting is input from the antenna 1a to the RF / IF conversion circuit portion 21a of the tuner module 2a. The IF conversion circuit unit 21a sequentially performs a high-frequency amplification high-frequency reception process and an intermediate frequency conversion process on the television broadcast signal to convert the television broadcast signal into an intermediate-frequency signal (hereinafter referred to as an IF signal).

  The IF signal is filtered by the BPF unit 22a with a sufficiently wide band limiting characteristic shown in FIG. 4A so as not to damage the information of the analog TV broadcast and the digital TV broadcast. When receiving analog television broadcasting and digital television broadcasting in North America, the center frequency fc of the pass band in FIG. 4A is, for example, 44 MHz, and the upper limit frequency and the lower limit frequency are α = 3 MHz. Fc + α, fc -Α.

  The IF signal after the filter processing of the BPF unit 22a is supplied to the reception circuit 4 for analog television broadcast. When an analog broadcast channel is selected, the reception circuit 4 receives, for example, the well-known NTSC for the input IF signal. A TV broadcast reception process is performed to reproduce and output an analog reception demodulated signal of the selected channel.

  When the subsequent video / audio processing is performed digitally, the analog reception demodulated signal of the analog TV broadcast receiving circuit 4 is converted into a digital signal by the A / D conversion circuit 52a of the final stage module 5a. The digital signal is subjected to digital amplification and characteristic adjustment of the video and audio of the digital processing circuit 53a, and then sent to a display processing and audio output processing module (not shown).

  By the way, the IF signal after the filter processing of the BPF unit 22 a is also supplied to the SAW filter module 3.

  The SAW filter module 3 forms SAW filter sections of two-stage SAW filters 31 and 32. For example, the band characteristics of the SAW filter 31 in FIG. 4B and the pass band characteristics of the SAW filter 32 in FIG. Depending on the combination, the input IF signal is subjected to a band limitation with a steep cutoff characteristic, and the IF signal after the band limitation is supplied to the digital television broadcast demodulation circuit 51a of the final stage module 5a through the AGC (automatic gain control) amplifier 33. .

  Then, the demodulating circuit 51a of the digital television broadcast performs known demodulation processing of the ATSC broadcast and the terrestrial digital broadcast in Japan on the input IF signal, and reproduces the digital broadcast video and audio digital signal of the selected channel. The digital broadcast video and audio digital signals are subjected to the same amplification and characteristic adjustment in the digital processing circuit 53a and then sent to the display processing and audio output processing modules. .

  Then, the above-mentioned television broadcast receiving apparatus for receiving the North American analog television broadcast and digital television broadcast includes the SAW filter module 3 in the preceding stage of the digital television broadcast receiving circuit as shown in FIG. In general, two-stage SAW filter processing is performed on an input signal of a television broadcast receiving circuit (see, for example, Patent Document 1).

  Also, in an ATSC digital television broadcast-only receiver, it has been proposed to perform a two-stage SAW filter process on an input signal of a digital television broadcast reception circuit (see, for example, Patent Document 2).

  The receiving apparatus described in Patent Document 2 is configured as schematically shown in FIG. 5, and the tuner module 2b connected to the antenna 1b corresponds to the RF / IF conversion circuit unit 21a and the BPF unit 22a in FIG. An RF / IF conversion circuit unit 21b, a BPF unit 22b, and a SAW filter 23b and an AGC amplifier 24b corresponding to the SAW filter 31 and the AGC amplifier 33 in FIG. 3 are provided. The IF signal of the RF / IF conversion circuit unit 21b is a BPF unit. 22b, the SAW filter 23b, and the AGC amplifier 24b are sent to the SAW filter 6 having a module configuration corresponding to the AW filter 31 of FIG.

Further, the output signal of the SAW filter 6 is sent to the digital broadcast demodulating circuit 51b of the final stage module 5b via the amplifier 7, and the digital video and audio signals demodulated by the demodulating circuit 51b are converted into the digital processing of FIG. It is sent to the digital processing circuit 53b similar to the circuit 53a for processing.
JP 2002-158594 A (abstract, [0002]-[0010], FIG. 3 etc.) Utility Model Registration No. 3113190 ([0006]-[0009], FIG. 4 etc.)

  3 and 5, the SAW filter unit formed by the BPF units 22a and 22b and the two-stage SAW filters 31, 32, 23b, and 6 in order to perform the filter processing of the television broadcast signal. With.

  The reason why the processing of the two-stage SAW filters 31, 32, 23b and 6 of the SAW filter unit is necessary for the digital television broadcast signal is as follows.

  In other words, in order to reduce the error rate of digital TV broadcast information, it is necessary to make the passband as wide as possible. On the other hand, in order to reduce the influence of interference from adjacent channels or the like, it is necessary to increase the attenuation rate (cutoff rate) outside the passband as much as possible.

  On the other hand, the BPF section 22a of the tuner module 2a generally does not cause a problem regardless of the input characteristics of the reception circuit 4 or the like of the next stage analog TV broadcast. For example, a sufficient wide band characteristic shown in FIG. 4A is set, which exceeds the necessary pass band characteristic that does not impair the information. In addition, the BPF section 22b of the tuner module 2b is also set to a broadband characteristic that exceeds the required characteristics so that no problem arises regardless of the characteristics of the SAW filters 23b, 6 and the like.

  Then, it is difficult for a wideband signal passing through the BPF units 22a and 22b to perform a necessary band limitation for digital television broadcasting with a steep characteristic having a large attenuation rate as described above with a single-stage SAW filter.

  For this reason, the conventional device or the like combines the band characteristics of the two-stage SAW filters 31, 32, 23b, and 6 to obtain a comprehensive characteristic that sharply attenuates in a wide band as shown in FIG. 4D, for example.

  The SAW filters 31, 32, 23b, and 6 are large and expensive parts compared to the BPF units 22a and 22b having the analog circuit configuration. The SAW filters 31, 32, 23b, and 6 are not only the BPF units 22a and 22b but also two (two-stage) SAWs. The conventional apparatus including the SAW filter portions of the filters 31, 32, 23b, and 6 is large and expensive, and there is a problem that the apparatus cannot be reduced in size and cost.

  An object of the present invention is to form a SAW filter portion with one (one stage) SAW filter so as to obtain filter characteristics similar to those of a conventional apparatus, and to reduce the size and cost of the apparatus.

  In order to achieve the above-described object, the television broadcast receiving apparatus of the present invention performs high frequency reception processing, intermediate frequency conversion processing, and passband limiting filter processing on the received television broadcast signal of the selected channel, and performs analog television broadcasting. A high-frequency processing unit for performing the high-frequency processing and the intermediate frequency conversion processing, and the high-frequency processing in a television broadcast receiving apparatus for receiving and processing analog television broadcasting and digital television broadcasting A band-pass filter unit that forms a next-stage circuit of the unit, applies a pass-band limiting filter process to the output signal of the high-frequency processing unit, and supplies the filtered signal to the analog television broadcast receiving circuit, and an output signal of the band-pass filter unit Surface to which a passband limiting filter process is applied to the digital television broadcast demodulation circuit An acoustic wave filter unit, and narrows the pass band of the band-pass filter unit within a range in which the information of the analog television broadcast and the digital television broadcast passes, and the surface acoustic wave filter unit of the band-pass filter unit It is characterized in that it is formed by a one-stage surface acoustic wave filter that extracts information of the digital television broadcast with a steep cut-off characteristic in combination with the filter characteristic (claim 1).

  2. The television broadcast receiver according to claim 1, wherein the high-frequency processing unit, the band-pass filter unit, and the surface acoustic wave filter unit are arranged upstream of the analog television broadcast reception circuit and the digital television broadcast demodulation circuit. The tuner modules are collectively provided (claim 2).

  According to the television broadcast receiving apparatus of the first aspect, the BPF section subsequent to the high-frequency processing section does not have an excessively wide band characteristic like the BPF section of the conventional apparatus, but the information of the analog television broadcast and the digital television broadcast passes. The bandwidth is narrowed within the range.

  Therefore, the BPF part acts as a first-stage SAW filter of the SAW filter part of the conventional device. In this case, by forming the SAW filter unit with a single-stage SAW filter, it is possible to extract digital TV broadcast information by performing a passband limitation of a steep cutoff characteristic in combination with the filter characteristic of the BPF part, Filter processing similar to the SAW filter unit of the conventional apparatus can be performed.

  Therefore, it is possible to provide a small and inexpensive television broadcast receiving apparatus in which the SAW filter unit is formed by one (one stage) SAW filter and the same filter characteristics as the conventional apparatus can be obtained.

  According to the television broadcast receiver of claim 2, since the high-frequency processing unit, the BPF unit, the SAW filter unit, and the analog broadcast receiving circuit are collectively provided in the tuner module, further miniaturization can be achieved. Since these connection wirings are shortened and the entire tuner module can be shielded, noise mixing in the front stage of the demodulating circuit for digital television broadcasting can be reduced, and the S / N characteristics are also improved.

  Next, in order to describe the present invention in more detail, the embodiment will be described in detail with reference to FIGS.

  FIG. 1 is a block diagram of a television broadcast receiver that receives, for example, analog television broadcast and digital television broadcast in North America, and FIG. 2 is an explanatory diagram of filter characteristics of the television broadcast receiver of FIG.

  The television broadcast receiver in FIG. 1 includes a tuner module 2c at the next stage of the antenna 1c and a final module 5c at the subsequent stage.

  And the antenna 1c is the structure similar to the antenna 1a of FIG.

  Further, the tuner module 2c corresponding to the tuner module 2a of FIG. 3 has the RF / IF conversion circuit unit 21c, the BPF unit 22c, the analog television broadcast receiving circuit 23c, the SAW filter unit 24c, and the AGC amplifier 25c shielded. It is formed on a common substrate unit.

  The RF / IF conversion circuit unit 21c connected to the antenna 1c has the same configuration as the RF / IF conversion circuit unit 21a of FIG. 3, and performs high-frequency processing and intermediate frequency conversion processing on the received TV broadcast signal of the selected channel. A high-frequency processing unit for performing is formed.

  Further, the BPF unit 22c corresponds to the BPF unit 22a of FIG. 3, but the pass band is not excessively wide like the BPF unit 22a but the range through which the information of the analog TV broadcast and the digital TV broadcast passes. The band is narrowed by.

  Specifically, based on selection of filter constants, the pass band of the BPF unit 22c is set as shown in FIG. 2A, and the characteristic of this pass band is the pass of the BPF unit 22a of FIG. 4A. Compared with the band characteristics, the upper and lower limit attenuation characteristics are steep, and the passband width of the flat portion including the center frequency fc is narrowed as follows.

  That is, in the case of the North American specification, the center frequency fc is 44 MHz and the pass bandwidth is 6 MHz in the past, but according to experiments, etc., adjacent channel interference of information included in IF signals of analog television broadcasting and digital television broadcasting, etc. A practical passband width that eliminates the effects of is about 5 MHz.

  Therefore, the attenuation characteristics of the BPF unit 22c at the upper limit frequency fc + α (= 47 MHz) and the lower limit frequency fc−α (= 41 MHz) are made steeper than the attenuation characteristic of the conventional BPF 22a as shown in Table 1 below.

  By setting in this way, the pass band width of the BPF 22a is about 6 MHz, whereas the pass band width of the BPF 22c is narrowed to about 5 MHz.

  As a result, the filter characteristic of the BPF unit 22c of FIG. 2A is substantially the same as the filter characteristic of the first-stage SAW filter 31 of the conventional apparatus of FIG. Acts as the first-stage SAW filter 31 of the SAW filter module 3 of the conventional apparatus.

  Then, the IF signal after the filter processing of the BPF unit 22c is supplied to an analog television broadcast receiving circuit 23c. When an analog broadcast channel is selected, the receiving circuit 23c performs reception processing on the input IF signal. The analog received demodulated signal of the selected channel is reproduced and output.

  Next, since the SAW filter unit 24c in the next stage of the BPF unit 22c extracts digital television broadcast information with a steep cut-off characteristic in combination with the filter characteristic of the BPF unit 22c, the filter is substantially the same as the SAW filter 32 of FIG. The filter is formed by a single-stage SAW filter having the filter characteristics shown in FIG. 2B, which is substantially equal to the characteristics shown in FIG. 4C. In FIG. 2, β is a band several channels away.

  The total filter characteristics of the BPF unit 22c and the SAW filter unit 24c are as shown in FIG. 2C, and are substantially the same as the total filter characteristics of the two-stage SAW filters 31 and 32 of FIG. become.

  Therefore, when a digital broadcast channel is selected, the IF signal after being filtered by the BPF unit 22c and the SAW filter unit 24c in the same manner as the conventional device of FIG. 3 corresponds to the AGC amplifier 33 of FIG. The signal is supplied to the digital television broadcast demodulation circuit 51c of the final stage module 5c through the AGC amplifier 25c.

  The final stage module 5c includes a demodulation circuit 51a, an A / D conversion unit 52a, and a digital processing circuit 53a identical to the demodulation circuit 51a, the A / D conversion unit 52a, and the digital processing circuit 53c of the final stage module 5a of FIG. And operates in the same manner as the final module 5a.

  Therefore, the television broadcast receiving apparatus of the above embodiment has a configuration including the SAW filter unit 24c including a single-stage SAW filter, and the configuration including the SAW filter module 3 including the two-stage SAW filters 31 and 32 in FIG. Analog TV broadcast and digital TV broadcast can be received by performing the same filter processing as in the case.

  Then, it is possible to provide a small and inexpensive television broadcast receiving apparatus in which the SAW filter unit 24c is formed by one (one stage) SAW filter and the same filter characteristics as those of the conventional apparatus can be obtained.

  In addition, in the case of the present embodiment, the RF / IF conversion circuit unit 21c, the BPF unit 22c, the SAW filter unit 24c, and the analog broadcast receiving circuit 23c as high-frequency processing units are integrated on the shielded circuit board of the tuner module 2c. Therefore, it is possible to further reduce the size, shorten the connection wiring thereof, and shield the entire tuner module 2c, so that noise is mixed in the preceding stage of the demodulating circuit 51c for digital television broadcasting. There is an advantage that the S / N characteristics can be improved.

  The present invention is not limited to the embodiment described above, and various modifications other than those described above can be made without departing from the spirit of the present invention, and the filters of the BPF unit 22c and the SAW filter unit 24c are possible. The characteristics and the like may be variously set based on the signal characteristics of analog television broadcasting and digital television broadcasting.

  Further, the RF / IF conversion circuit unit 21c, the BPF unit 22c, the SAW filter unit 24c, the analog broadcast receiving circuit 23c, and the like may not be provided collectively in the tuner module 2c.

  The present invention can be applied to television broadcast receivers having various analog television broadcast and digital television broadcast reception processing functions.

It is a block diagram which shows the circuit structure of the television broadcast receiver in one Embodiment of this invention. FIG. 6 is a frequency characteristic diagram of the BPF unit and the SAW filter unit, where (a) shows the characteristic of the BPF unit, (b) shows the frequency characteristic of the SAW filter unit, and (c) shows the frequency characteristics of the BPF unit and the SAW filter unit. Shows overall characteristics. It is a block diagram which shows the circuit structure of an example of a conventional apparatus. It is a frequency characteristic diagram of a BPF unit and a two-stage SAW filter unit of an example of a conventional device, (a) shows the characteristics of the BPF unit, (b) shows the frequency characteristics of the first stage SAW filter, (C) shows the frequency characteristics of the second-stage SAW filter, and (d) shows the total characteristic characteristics of the BPF section and the two-stage SAW filter section. It is a block diagram which shows the circuit structure of the other example of the conventional apparatus.

Explanation of symbols

2c tuner module 21c RF / IF conversion circuit unit 22c band pass filter (BPF) unit 23c analog TV broadcast receiving circuit 24c surface acoustic wave (SAW) filter unit 51c digital TV broadcast demodulation circuit

Claims (2)

  The received TV broadcast signal of the selected channel is subjected to high frequency reception processing, intermediate frequency conversion processing and passband limiting filter processing, and supplied to an analog TV broadcast reception circuit and a digital TV broadcast demodulation circuit. In a television broadcast receiving apparatus for receiving and processing digital television broadcast, a high-frequency processing unit that performs the high-frequency processing and the intermediate frequency conversion processing and a next-stage circuit of the high-frequency processing unit are formed and passed to an output signal of the high-frequency processing unit A band-pass filter unit that performs band-limiting filter processing and supplies the analog television broadcast receiving circuit to the analog television broadcast receiving circuit, and performs pass-band limiting filter processing on the output signal of the band-pass filter unit to the digital television broadcast demodulation circuit A surface acoustic wave filter section to be supplied, and a pass band of the bandpass filter section The information of the digital television broadcast is narrowed in a range in which the information of the analog television broadcast and the digital television broadcast passes, and the surface acoustic wave filter unit is combined with the filter characteristic of the bandpass filter unit with a steep cutoff characteristic. A television broadcast receiver characterized in that it is formed by a single-stage surface acoustic wave filter for extracting a signal.   The high-frequency processing unit, the band-pass filter unit, the surface acoustic wave filter unit, and the analog broadcast receiving circuit are collectively provided in a tuner module in front of the digital television broadcast demodulation circuit. The television broadcast receiver according to claim 1.

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