JP2006304041A - Tv/fm compound tuner circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that, although in a digital television broadcast system an intermediate frequency signal is inputted into a digital demodulation circuit to demodulate a video and an audio resulting in eliminating an intermediate frequency but disabling the reception of an FM voice multiplex broadcast as it is, an FM tuner is required for the reception independently from a TV tuner while miniaturization, light weight, and low power consumption are severely required for mobile television receivers mounted to portable phones and car navigation systems or the like. <P>SOLUTION: An FM reception signal is demodulated by dividing a VHF band oscillation signal of a local oscillator 42 in a frequency division circuit 51 and inputted it into a second mixing circuit 53. Consequently, the FM broadcast can be viewed and listened using a television tuner for a digital television broadcast system and an FM wave oscillation circuit, and its constituent circuits can be eliminated to achieve miniaturization, light weight, and low power consumption. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a TV / FM composite tuner mounted on a mobile television receiver, and more particularly to a TV / FM composite tuner circuit that is optimal for incorporation in a semiconductor integrated circuit.

  In recent years, demand for mobile television receivers mounted on mobile phones, car navigation systems, and the like has increased. As an added value, there is FM audio multiplex broadcast reception on mobile television receivers. (For example, refer to Patent Document 1).

  FIG. 3 is a configuration diagram of a conventional TV / FM combined tuner circuit described in Patent Document 1. In FIG.

  In FIG. 3, 1 is an antenna. Reference numeral 2 denotes a TV receiver that receives a terrestrial TV broadcast signal, and includes a UHF signal receiver 14 and a VHF signal receiver 24. Further, the UHF signal receiving unit 14 includes a single tuning filter 11, a high frequency amplifier 12 and a double tuning filter 13, and the VHF signal receiving unit 24 includes a single tuning filter 21, a high frequency amplifier 22 and a double tuning filter 23. ing. Reference numeral 34 denotes an FM signal receiving unit which includes a single tuning filter 31, a high frequency amplifier 32, and a double tuning filter 33. Reference numeral 103 denotes a switch for selecting one of the output signal from the UHF signal receiving unit 14, the output signal from the VHF signal receiving unit 24, and the output signal from the FM signal receiving unit 34. Next, reference numeral 4 denotes a frequency converter, which includes a first mixing circuit 41, a local oscillator 42, and an intermediate frequency filter 43. Reference numeral 105 denotes an intermediate frequency unit, which includes an amplifier circuit 151, a video detector 152, and a voltage controlled oscillator 153. Next, reference numeral 7 denotes an audio signal demodulator, which comprises an amplifier circuit 71 and an audio signal demodulator circuit 72. Reference numeral 106 denotes a band-pass filter that extracts only SIF (Sound Intermediate Frequency) from the output signal of the intermediate frequency unit 105 and inputs it to the audio signal demodulation unit 7. Reference numeral 181 denotes a TV audio multiplexed signal demodulation circuit, 82 denotes an FM stereo demodulation circuit, 191 denotes a video signal output terminal, 192 denotes a TV audio multiplexed signal output terminal, 93 denotes an FM stereo signal output terminal, and 94 denotes an FM audio signal output terminal. is there.

  Next, the operation of the TV / FM composite tuner circuit of FIG. 3 will be described.

(When receiving TV)
First, TV signal reception will be described.

  A high-frequency signal input from the antenna 1 is input to the TV receiver 2. 11 is a single tuning filter having a tuning frequency of the UHF broadcast band, and only the UHF broadcast band signal among the input signals from the antenna 1 passes therethrough. The high frequency amplifier 12 is connected to the output of the single tuning filter 11 and amplifies the UHF broadcast band signal. The output signal of the high frequency amplifier 12 is input to the switch 103 via the double tuning filter 13.

  Next, 21 is a single tuning filter having a tuning frequency of VHF broadcast band, and only the signal of VHF broadcast band among the input signals from the antenna 1 passes. The high frequency amplifier 22 is connected to the output of the single tuning filter 21 and amplifies the signal in the VHF broadcast band. The output signal of the high frequency amplifier 22 is input to the switch 103 via the double tuning filter 23. Here, by switching the switch 103, either the UHF broadcast signal or the VHF broadcast signal can be selected, and the selection signal is input to one end of the first mixing circuit 41.

  On the other hand, the output of the local oscillator 42 is connected to the other end of the first mixing circuit 41. The output of the first mixing circuit 41 mixed with the output of the switch 103 and converted to the intermediate frequency is the intermediate frequency. The interference wave is removed by the filter 43, amplified by the amplifier circuit 151, and then input to the video detector 152. The output signal of the amplifier circuit 151 input to the video detector 152 is detected by the output signal of the voltage controlled oscillator 153 and output from the video signal output terminal 191. Here, the output signal of the video detector 152 is also input to the band pass filter 106, and only the SIF is extracted and input to the amplifier circuit 71. The signal input to the amplifier circuit 71 is amplified and demodulated into an audio signal by the audio signal demodulation circuit 72 and output from the TV audio multiplexed signal output terminal 192 via the TV audio multiplexed signal demodulation circuit 181.

  Since the voltage controlled oscillator 153 at this time is locked at the video intermediate frequency, the desired C / N is secured.

(When receiving FM)
Next, FM signal reception will be described.

  The high frequency signal input from the antenna 1 is input to the FM signal receiving unit 34. 31 is a single tuning filter whose tuning frequency is FM broadcast band, and an input signal from the antenna 1 passes therethrough. The high frequency amplifier 32 is connected to the output of the single tuning filter 31 and amplifies this FM broadcast band signal. The output signal of the high frequency amplifier 32 passes through the switch 103 via the double tuning filter 33 and the 1 is input to one end of the mixing circuit 41.

  On the other hand, the output of the local oscillator 42 is connected to the other end of the first mixing circuit 41. The output of the first mixing circuit 41 mixed with the output of the switch 103 and converted to the intermediate frequency is the intermediate frequency. The interference wave is removed by the filter 43, amplified by the amplifier circuit 151, and then input to the video detector 152. The output signal of the video detector 152 is input to the band pass filter 106, and only the SIF is extracted and input to the amplifier circuit 71. The signal input to the amplifier circuit 71 is amplified, demodulated into an audio signal by the audio signal demodulator circuit 72, output from the FM audio signal output terminal 94, and input to the FM stereo demodulator circuit 82, and demodulated to stereo. And output from the FM stereo signal output terminal 93.

  However, at this time, since there is no video intermediate frequency, the voltage controlled oscillator 153 performs free-run oscillation, and the audio carrier output causes a frequency shift, so that C / N deteriorates, which is disadvantageous in terms of S / N characteristics. How to use.

Thus, by using the TV / FM composite tuner circuit, both TV broadcast and FM audio multiplex broadcast can be viewed on the mobile television receiver.
JP 2002-238005 A

  However, in the terrestrial digital television broadcasting system introduced as a new system for terrestrial TV broadcasting, the intermediate frequency signal is input to the digital signal demodulating circuit and the video signal and the audio signal are digitally demodulated. A certain intermediate frequency unit 105 becomes unnecessary. For this reason, FM sound multiplex broadcasting cannot be viewed as it is, and an FM tuner is required separately from the TV tuner in order to view this.

  On the other hand, miniaturization, weight reduction, and power saving are strictly required for mobile television receivers installed in mobile phones and car navigation systems.

  The present invention solves the above-mentioned conventional problems, and enables viewing of FM audio multiplex broadcasting with a TV tuner system for a digital terrestrial television broadcasting system, as well as reduction in size, weight, and power consumption. An object is to provide a TV / FM composite tuner.

  In order to solve the above problems, a TV / FM composite tuner circuit according to claim 1 is a local oscillator having oscillation frequency changing means, a first high frequency signal selected by an output of the local oscillator and an antenna tuning circuit. And a digital signal demodulating circuit for digitally demodulating the first intermediate frequency signal, and a digital terrestrial digital circuit comprising: a first mixing circuit for converting the first high frequency signal into a first intermediate frequency signal; A terrestrial FM tuner circuit comprising: a TV tuner circuit; a second mixing circuit that converts a second high-frequency signal selected by the antenna tuning circuit into a second intermediate-frequency signal; and an audio signal demodulation circuit. A frequency divider that divides the output signal of the local oscillator, wherein the second mixed signal is used to convert the output signal of the frequency divider to convert the second high frequency signal into the second intermediate frequency signal. Is obtained and wherein the input to the road.

  According to a second aspect of the present invention, in the tuner according to the first aspect, a filter circuit for inputting the output of the frequency dividing circuit is provided.

  By using the TV / FM composite tuner circuit of the present invention, the FM wave oscillation circuit and its constituent circuits (PLL synthesizer, etc.) can be omitted, and FM audio multiplex broadcasting can be viewed using a TV tuner for digital terrestrial television broadcasting. It is possible to reduce the size, weight, and power consumption.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

(Embodiment 1)
FIG. 1 is a block diagram showing a configuration of a tuner of a mobile television receiver according to Embodiment 1 of the present invention. In FIG. 1, the same components as those in FIG. 3 of the conventional example are denoted by the same reference numerals, and description thereof is omitted.

  In this configuration, the output signal of the local oscillator 42 is also connected to the frequency divider circuit 51, and the signal frequency-divided by the frequency divider circuit 51 is input to the second mixing circuit 53. This is a circuit that uses the input signal of the second mixing circuit 53 instead of the oscillation signal of the FM wave oscillator in the FM composite tuner circuit. The antenna 1, the single tuning filter 11, the high frequency amplifier 12, the double tuning filter 13, the single tuning filter 21, the high frequency amplifier 22, the double tuning filter 23, the single tuning filter 31, the high frequency amplifier 32, and the double tuning filter 33 according to this embodiment. The first mixing circuit 41, the local oscillator 42, the intermediate frequency filter 43, the amplification circuit 71, the audio signal demodulation circuit 72, the FM stereo demodulation circuit 82, the FM stereo signal output terminal 93, and the FM audio signal output terminal 94 are the conventional ones. It is the structure similar to a thing.

  The operation of the tuner circuit of the present invention configured as described above will be described. The configuration and functions other than the frequency dividing circuit are the same as those in the prior art.

  First, reference numeral 51 denotes a frequency divider, which divides the oscillation signal of the local oscillator 42 and inputs it to one end of the second mixing circuit 53.

  On the other hand, the high frequency signal input from the antenna 1 is input to the other end of the second mixing circuit 53 via the FM signal receiving unit 34. The output signal of the frequency dividing circuit 51 and the output signal of the FM signal receiving unit 34 are mixed and converted to an FM intermediate frequency, amplified by the amplifier circuit 71, demodulated into an audio signal by the audio signal demodulation circuit 72, and FM. The audio signal is output from the audio signal output terminal 94, input to the FM stereo demodulation circuit 82, demodulated into audio multiplexes, and output from the FM stereo signal output terminal 93.

  For example, in Japan, the local oscillation frequency required for FM broadcast reception is 65.3 MHz to 79.3 MHz, and the local oscillation frequency required for VHF broadcast reception is 150 MHz to 276 MHz. Here, a value three times the local oscillation frequency for FM broadcast reception is 195.9 MHz to 237.9 MHz, which is a part of the local oscillation frequency for VHF broadcast reception. Therefore, for example, when the frequency dividing circuit 51 is a three-frequency divider, the local oscillator 42 oscillates at a frequency of 195.9 MHz to 237.9 MHz, and these signals are input to the frequency dividing circuit 51 and divided into one third. A signal used for FM broadcast reception can be obtained by going around.

  For example, when the FM broadcast wave signal RF selected by the FM signal receiving unit 34 is RF = 77.4 MHz and the intermediate frequency signal IF is IF = 10.7 MHz, the necessary local oscillation frequency signal Lo is Lo = 66.7 MHz. However, considering that the local oscillation frequency signal Lo is substituted with the oscillation frequency signal of the local oscillator 42, the frequency dividing ratio of the frequency dividing circuit 51 is fixed to 1/3, and the local oscillator 42 is oscillated at 200.1 MHz. By doing so, the output of the second mixing circuit 53 can be an intermediate frequency signal of the desired wave.

  In the present invention, Japan is taken as an example. In the United States, for example, the local oscillation frequency required for FM broadcast reception and the local oscillation frequency required for VHF broadcast reception are 98.7 MHz to 118.7 MHz and 101 MHz to 413 MHz, respectively. Become.

  For example, in the United States, when the FM broadcast wave signal RF selected by the FM signal receiver 34 is RF = 106.8 MHz and the intermediate frequency IF is IF = 10.7 MHz, the necessary local oscillation frequency signal Lo is Lo = 117. However, considering that this local oscillation frequency signal Lo is substituted by the oscillation frequency signal of the local oscillator 42, the frequency division ratio of the frequency dividing circuit 51 is fixed to ½, and the local oscillator 42 is set to 235 MHz. When oscillated, the output signal of the second mixing circuit 53 can be an intermediate frequency signal of the desired wave.

  Here, it is necessary to change the frequency dividing ratio of the frequency dividing circuit 51 according to the time, so that the frequency dividing ratio of the frequency dividing circuit 51 is halved.

  When the FM signal is converted to an intermediate frequency using the oscillation signal of the local oscillator 42 in this way, the signal locked by the PLL is used, so that it is compared with the conventional TV / FM composite tuner shown in FIG. In addition, both frequency characteristics and C / N can be improved.

(Embodiment 2)
FIG. 2 is a block diagram showing the configuration of the tuner of the mobile television receiver according to the second embodiment of the present invention. 2, the same components as those in FIGS. 1 and 3 are denoted by the same reference numerals, and the description thereof is omitted.

  In this configuration, by passing the output signal of the frequency dividing circuit 51 to the filter circuit 52, an unnecessary signal component is suppressed from the output signal of the frequency dividing circuit 51, and an unnecessary signal component is generated in the FM intermediate frequency band. The output of the frequency dividing circuit 51 is input to the second mixing circuit 53 via the filter circuit 52.

  For example, when the FM broadcast wave signal RF selected by the FM signal receiving unit 34 is RF = 85.6 MHz and the intermediate frequency signal IF is IF = −10.7 MHz, the necessary local oscillation frequency signal Lo is Lo = 74.9 MHz. Yes, the frequency dividing ratio of the frequency dividing circuit 51 may be set to one third, and the oscillation frequency of the local oscillator 42 may be set to 224.7 MHz. At this time, in addition to the desired wave of 74.9 MHz, 149.8 MHz, 299.6 MHz. , 374.5 MHz, 449.4 MHz, 524.3 MHz, and the like are generated and supplied to the second mixing circuit 53. On the other hand, since the broadcast wave signal RF is 85.6 MHz, its harmonic components 171.2 MHz, 256.8 MHz, 342.4 MHz, 428.0 MHz, 513.6 MHz, and the like are supplied to the mixer. Here, for example, a signal of 10.7 MHz, which is a difference between 524.3 MHz and 513.6 MHz, is generated by the second mixing circuit 53, and a beat component is generated in the FM intermediate frequency band.

  In this case, the 10.7 MHz beat component can be suppressed by connecting a low-pass or band-pass filter circuit having a cutoff frequency of 524 MHz or less to the output of the frequency divider circuit 51.

  The TV / FM composite tuner circuit according to the present invention enables viewing of FM audio multiplex broadcasting using a TV tuner for the terrestrial digital television broadcasting system, as well as miniaturization, weight reduction, and low power consumption. The present invention relates to a tuner mounted on a mobile television receiver, and is particularly useful as a tuner circuit that is most suitable for being incorporated in a semiconductor integrated circuit.

FIG. 2 is a diagram of a TV / FM combined tuner circuit of the mobile television receiver according to the first embodiment of the present invention. Diagram of a TV / FM combined tuner circuit of a mobile television receiver according to Embodiment 2 of the present invention Configuration diagram of a conventional TV / FM composite tuner circuit

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Antenna 2 TV receiving part 3 Switch 4 Frequency converting part 6 Digital signal demodulating circuit 7 Audio signal demodulating part 11 Single tuning filter 12 High frequency amplifier 13 Double tuning filter 14 UHF signal receiving part 21 Single tuning filter 22 High frequency amplifier 23 Double tuning filter 24 VHF signal receiving unit 31 Single tuning filter 32 High frequency amplifier 33 Double tuning filter 34 FM signal receiving unit 41 First mixing circuit 42 Local oscillator 43 Intermediate frequency filter 51 Dividing circuit 52 Filter circuit 53 Second mixing circuit 71 Amplifying circuit 72 Audio signal demodulator circuit 82 FM stereo demodulator circuit 91 Digital signal output terminal 93 FM stereo signal output terminal 94 FM audio signal output terminal 103 Switch 105 Intermediate frequency unit 106 Band pass filter 151 Amplifying circuit 152 Video detector 153 Controlled oscillator 181 TV sound multiplex signal demodulation circuit 191 video signal output terminal 192 TV sound multiplex signal output terminal

Claims (2)

A local oscillator having oscillation frequency changing means, an output of the local oscillator, and a first high-frequency signal selected by an antenna tuning circuit are supplied to convert the first high-frequency signal into a first intermediate frequency signal A digital television tuner circuit including a first mixing circuit that performs digital demodulation of the first intermediate frequency signal, and a second intermediate frequency signal selected by the antenna tuning circuit. A terrestrial FM tuner circuit having a second mixing circuit for converting to a frequency signal and an audio signal demodulating circuit has a frequency dividing circuit for frequency-dividing the output signal of the local oscillator, and the output of the frequency dividing circuit A TV / FM combined tuner circuit, wherein a signal is input to the second mixing circuit for converting the second high frequency signal into the second intermediate frequency signal. 2. The TV / FM composite tuner circuit according to claim 1, further comprising a low-pass type or band-pass type filter circuit for inputting an output of the frequency dividing circuit.

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