JPH061905B2 - Receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to each antenna reception output of satellite television broadcasting using frequencies in the SHF band, television broadcasting using frequencies in the UHF / VHF band, and FM voice radio broadcasting. The present invention relates to a receiving device capable of receiving in common and selectively viewing and listening, and particularly to a demodulation circuit therein.

[Conventional technology]

Regarding general commercial TV / radio broadcasting, SH
Band 27 is used for satellite television broadcasting that uses frequencies in the F band.
The FM modulation system of MHz is adopted, the AM modulation system of band 6 MHz is adopted in UHF / VHF television broadcasting, and the transmission is carried out in band 150 KHz in FM audio radio broadcasting.

In order to receive each of these broadcasts with a single receiving device, if a demodulation circuit suitable for each broadcast system is provided, the configuration becomes complicated and the price becomes expensive. Conventionally, one of the receivers capable of receiving some of these broadcasts is, for example, a receiver capable of receiving SHF band satellite television broadcasts and UHF / VHF band television broadcasts. It is described in Japanese Laid-Open Patent Publication No. 57-39628.

[Problems to be solved by the invention]

In the prior art described in the above publication, the demodulation circuit is provided separately for the FM demodulation circuit and the AM demodulation circuit, and no consideration is given to sharing the circuit.
If an existing FM demodulation circuit is used to add a voice radio broadcast reception function and demodulate it, the frequency shift of the FM signal is ± 13.5 MHz in SHF band satellite television broadcasting, for example, in Japan. On the other hand, in the FM voice radio broadcasting, the maximum is ± 75 KHz, which is very small, and therefore a demodulation output is hardly obtained. Therefore, there is a problem that another FM demodulation circuit must be provided for the FM voice radio.

The object of the present invention is to provide satellite television broadcasting in the SHF band, television broadcasting in the UHF / VHF band, and FM with a simple configuration.
It is an object of the present invention to provide a receiving device capable of guiding reception outputs of all broadcast waves of voice radio broadcasting to a common demodulation circuit and selectively demodulating them.

[Means for solving problems]

The above object is to provide two first and second PLL circuits (face locked loop circuits) as circuit elements constituting the demodulation circuit, and to connect the connection midpoints of the voltage controlled oscillator and the phase comparator in both PLL circuits. It is connected to each other via a 90 ° phase shifter, the voltage controlled oscillator of the second PLL circuit is stopped, and the FM is output from the output of the loop filter of the first PLL circuit.
Obtain the demodulated output of the modulated satellite television broadcast signal,
Further, the voltage controlled oscillator of the first PLL circuit is stopped to obtain the demodulated output of the AM-modulated UHF / VHF television broadcast signal from the output of the phase comparator of the first PLL circuit, or the second PLL circuit. This is achieved by the configuration in which the demodulated output of the FM-modulated audio broadcast signal is obtained from the output of the loop filter of and the control voltage of AFC and AGC is obtained from the PLL circuit.

[Action]

Regarding the first and second PLL circuits, the SHF
The second PL is used when demodulating the satellite television broadcast signal of the band.
The voltage controlled oscillator of the L circuit is stopped and the first PLL circuit performs FM demodulation of the satellite broadcast wave.
The C control voltage is obtained, and the output of the voltage controlled oscillator of the first PLL circuit is applied to the phase comparator of the second PLL circuit via the 90 ° phase shifter to form a synchronous detection circuit by the same phase comparator. Then, the AGC control voltage is obtained from the output of the in-phase comparator.

When demodulating UHF / VHF television broadcast signals,
The voltage detection oscillator of the first PLL circuit is stopped, and the second PLL circuit, the 90 ° phase shifter, and the phase comparator of the first PLL circuit form a synchronous detection circuit. A demodulation signal of the John broadcasting signal is output, an AGC control voltage is obtained from the demodulation signal, and the second PL
At the output of the loop filter of the L circuit, a DC voltage corresponding to the carrier frequency of the UHF / VHF television signal is obtained and becomes the AFC control voltage.

At the time of demodulating the FM audio radio signal, the voltage controlled oscillator of the first PLL circuit is stopped and the FM demodulation is performed by the second PLL circuit, and the AFC control voltage is obtained by the demodulated signal. The output of the voltage controlled oscillator is 9
The AGC control voltage is obtained from the output of the in-phase comparator, which is applied to the phase comparator of the first PLL circuit via the 0 ° C. phase shifter to form a synchronous detection circuit.

The voltage controlled oscillator of the first PLL circuit is selected to have high sensitivity (for example, about 50 MHz / V) corresponding to a wide frequency shift of SHF satellite television broadcasting, and the voltage controlled oscillator of the second PLL circuit is an FM voice radio. Broadcast FM demodulation and UHF
-Selecting a low sensitivity (for example, about 2MHz / V) that supports synchronous detection of VHF television broadcasting. By these, S
Since HF band satellite television broadcasting and FM voice radio broadcasting are FM demodulated by PLL, and UHF / VHF television broadcasting is AM demodulated by synchronous detection, demodulation characteristics with excellent weak electric field characteristics and low distortion can be obtained. .

〔Example〕

 Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 5 is a block diagram showing an outline of the configuration of an embodiment of the present invention.

Referring to FIG. This receiving apparatus includes a satellite broadcast receiving antenna and BS converter 43, a UHF television broadcast receiving antenna 44, a VHF television broadcast receiving antenna 45, an FM radio broadcast receiving antenna 46, an input filter 47, a wide band RF amplifier circuit 48, and 1 Mixer 49
Variable oscillators 50 and 51, first IF amplifier circuit 52, bandpass filter 53, second mixer 54, and fixed oscillator 55.
, Mixer 56, IF output filter 57, second IF amplifier circuit 58, demodulator circuit 59, prescaler 60, and tuning circuit 6
It consists of 1.

Satellite television broadcast received by antennas 43-46,
UHF / VHF television broadcasting and FM radio broadcasting are guided to the input filter 47 by a cable and band-selected, and then amplified by the wide band amplifier circuit 48 and input to the first mixer 49, and the oscillation output of the variable frequency oscillator 50 or 51. Is converted into a first IF frequency by being mixed with the first IF amplifier circuit 52, amplified by a first IF amplifier circuit 52, and an unnecessary wave is suppressed by a bandpass filter 53
The signal is input to the mixer 54, mixed with the oscillation signal of the fixed oscillator 55, converted to the second IF frequency, and the unnecessary wave is suppressed by the narrow band filter 57 set for each broadcast signal band, and then the predetermined signal level is set by the second IF amplifier circuit 58. Amplify and demodulate circuit 59
Entered in.

For tuning, the frequency difference between the variable oscillators 50 and 51 and the fixed oscillator 55 is detected by the mixer 56 and the prescaler 60, and the tuning circuit 61 sets the variable oscillators 50 and 5 so that the desired frequency difference is achieved.
Control 1 The AGC is applied by outputting the output of the terminal 103 of the demodulation circuit 59 to the wideband RF amplifier 48 and the second IF amplifier 58. The AFC outputs the output from the terminal 104 of the demodulation circuit 59 to the frequency division ratio control terminal 50 of the prescaler.
It can be applied by connecting to 0 and changing the division ratio of the prescaler.

Since the feature of the present invention lies in the demodulation circuit 59 in the configuration outline described above, the demodulation circuit 59 will be described below.

FIG. 1 shows a demodulation circuit 5 as an essential part of one embodiment of the present invention.
It is a block diagram which shows the detail of 9.

Please refer to FIG. The phase comparator 1, the loop filter 2 and the voltage controlled oscillator 3 constitute a first PLL circuit 4, and the phase comparator 5, the loop filter 6 and the voltage controlled oscillator 7 constitute a second PLL circuit 4.
Of the phase comparators 1 and 5 are connected to the input terminal 107, and the connection midpoints of the phase comparators 1 and 5 and the voltage controlled oscillators 3 and 7 are branched to form a 90 ° phaser. 9
And the output of the phase comparator 1 is branched and connected to the first audio processing circuit 13 including the bandpass filter 10 and the audio demodulating circuit 11, and the first video image including the audio trap 14. It is also connected to the processing circuit 17.

The output of the loop filter 2 is branched and connected to a second audio processing circuit 15 which is, for example, a PCM demodulation circuit 16 for demodulating a PCM signal of a satellite television signal into audio, and a video filter 18 and a de-emphasis circuit 19 are connected.
Second video processing circuit 21 including a clamp circuit 20 and a clamp circuit 20.
Connected to.

The output of the loop filter 6 is branched and connected to the third audio processing circuit including the stereo demodulation circuit 22.

Audio processing circuits 13, 15, 23 and video processing circuits 17, 2
The respective outputs of 1 are selected by the switches 24, 25 and 26, and the L and R audio signals from the terminals 100 and 101, the terminal 10
A video signal is output from 2. That is, the switch 2
When the U terminals are selected for 4, 25, and 26, the first audio processing circuit 13 and the first video processing circuit 17 are selected, and the UHF / V signals are output from the output terminals 100, 101, and 102.
A demodulated output of the HF television broadcast signal is to be obtained.

When the switches 24, 25, and 26 select the M terminal, the second audio processing circuit 15 and the second video processing circuit 21 are selected, and satellite television broadcasting is output from the output terminals 100, 101, and 102. A demodulated output of the signal is to be obtained. When the switches 24, 25 and 26 select the L terminal, the third audio processing circuit 23 and the ground are selected, and the FM from the output terminals 100, 101 and 102.
A demodulated output of the audio broadcast signal is to be obtained.

On the other hand, the AGC circuit 30 is constituted by the sync separation circuit 27, the switch 28, and the AGC control circuit 29, and the sync separation circuit 2
7, the output of the phase comparator 1 is input, and in the switch 28, the output of the sync separation circuit 27 is connected to the U terminal, and the phase comparators 1, 5
Output is connected to the L and M terminals respectively, and the switch 2
The output of 8 is connected to the AGC control circuit 29, and the terminal 103
The AGC voltage is output.

The AFC control circuit 33 is composed of a switch 31 and an AFC control circuit 32. The outputs of the loop filters 2 and 6 are connected to the M, U and L terminals of the switch 31, and the output of the switch 31 and the AFC control circuit 32 are connected. The AFC voltage is output from the terminal 104.

Further, the mode control circuit 34 includes switches 24, 25, 2
6, 28 and 31 are connected by a path c, the voltage controlled oscillators 3 and 7 are connected by a path a, and the loop filter 6 is connected by a path b. Then, the mode control circuit 34 is instructed by the control signal given to the terminal 106 which broadcast signal should be received, and switches each circuit so as to correspond to the broadcast signal to be received.

The loop condition of the PLL circuits 4 and 8 is that the first PLL circuit 4
Is set to a wide band, and the second PLL circuit 8 is set to a narrow band. When demodulating the SHF band satellite television broadcast signal that is FM-modulated, the voltage-controlled oscillator 3 oscillates by the signal from the mode control circuit 34, the voltage-controlled oscillator 7 stops, and the switch 26 is at the M terminal. The output of the second video processing circuit 21 is selected and the switches 24 and 2 are selected.
5 is also at the M terminal and the output of the second audio processing circuit 15 is selected, switch 28 is also at the M terminal and the output of the phase comparator 5 is selected, and switch 31 is also the M terminal.
The output of the loop filter 2 is selected at the terminal.

As a result, the FM signal of the satellite television broadcast input from the terminal 107 is FM-demodulated by the first PLL circuit 4, extracted from the loop filter 2, and imaged from the terminals 102, 100 and 101 via each processing circuit. Is output.

In the AFC, the demodulated output of the loop filter 2 is integrated by the AFC control circuit 32, the fluctuation of the average value is detected, and the corresponding voltage is output from the terminal 104. Since the voltage controlled oscillator 7 is stopped in the AGC, the phase comparator 5 has the first P
The output of the voltage controlled oscillator 3 of the LL circuit 4 is the 90 ° phase shifter 9
Is inputted through the phase comparator 5, the phase comparator 5 carries out synchronous detection, the amplitude component is output, and the AGC control circuit 29 outputs a voltage corresponding to the variation of the amplitude component. Is generated and is output from the terminal 103.

When demodulating the AM-modulated UHF / VHF television broadcast signal, the voltage-controlled oscillator 7 oscillates and the voltage-controlled oscillator 3 is stopped by the signal from the mode control circuit 34, and the switch 26 is at the U terminal. The output of the first video processing circuit 17 is selected, the switches 24 and 25 are also at the U terminal and the output of the first audio processing circuit 13 is selected, and the switch 28 is also at the U terminal and the sync separation circuit 27 is selected. Output is selected, the switch 31 is also at the U terminal, and the output of the loop filter 6 is selected.

The voltage controlled oscillator 7 of the second PLL circuit 8 oscillates at the same frequency as the carrier frequency of the AM signal which is the UHF / VHF television broadcast signal input from the terminal 107, and 9
By passing through the 0 ° phase shifter 9, the carrier of the same phase, that is, the AM signal is reproduced. Therefore, the AM signal is the phase comparator 1
Is synchronously detected by and is extracted from the output of the phase comparator 1.
Video and audio are output from the terminals 102, 100 and 101 via the respective processing circuits.

Since the output voltage of the loop filter 6 changes according to the carrier frequency change of the AM signal, the AFC
The control circuit 32 integrates this, detects the fluctuation of the average value, and outputs a corresponding voltage from the terminal 104.

The AGC outputs the demodulated output of the phase comparator 1 to the sync separation circuit 27.
Synchronous separation is performed by means of, and a voltage corresponding to the voltage fluctuation at the synchronizing tip is created and output from the terminal 103.

When demodulating the FM-modulated FM audio signal, the signal from the mode control circuit 34 causes the voltage-controlled oscillator 7 to oscillate, the voltage-controlled oscillator 3 to stop, and the switch 26 to switch to L level.
Ground (ground) is selected at the terminal and switch 2
4 and 25 are both at the L terminal and have a third audio processing circuit 23.
Output is selected, the switch 28 is at the L terminal and the output of the phase comparator 1 is selected, and the switch 31 is at the L terminal and the output of the loop filter 6 is selected.

As a result, the FM audio signal input from the terminal 107 is FM-demodulated by the second PLL circuit 8, extracted by the loop filter 6, and passed through the third audio processing circuit 23 to the terminal 10.
Audio is output from 0 and 101.

In the AFC, the output of the loop filter 6 is the AFC control circuit 3
The voltage is output from the terminal 104 in response to the fluctuation of the average value which is integrated by 2. Since the voltage-controlled oscillator 3 is stopped in the AGC, a signal in phase with the input FM audio signal is input to the phase comparator 1 from the voltage-controlled oscillator 7 via the 90 ° phase shifter 9 to perform phase comparison. Synchronous detection is performed by the device 1, the amplitude component is output, the AGC control circuit 29 creates a voltage corresponding to the fluctuation of the amplitude component, and the voltage is output from the terminal 103.

The loop condition of the second PLL circuit 8 of the loop filter 6 is A of the UHF / VHF television signal of AM modulation.
Carrier reproduction in M demodulation and F of audio signal in FM modulation
In M demodulation, since carrier reproduction has a narrower band, the cutoff frequency is switched by the signal from the mode control circuit 34 (path b).

In the voltage controlled oscillators 3 and 7, the frequency deviation of the FM signal is SH
F-band satellite television broadcasting, for example in Japan ±
In order to obtain an appropriate demodulation amplitude with respect to 8.5 MHz and ± 75 KHz of FM audio radio broadcasting, the voltage controlled oscillator 3 is selected to have high sensitivity, for example, about 50 MHz / V.
Is low sensitivity, for example, about 2 MHz / V.

The highly sensitive voltage controlled oscillator 3 can be easily realized by, for example, the emitter-coupled multivibrator shown in FIG.
Although the circuit operation of the emitter-coupled multivibrator is well known and omitted, the oscillation output is output from the terminals 200 and 201, the oscillation frequency is determined by changing the current of the current source 35, and the oscillation and the oscillation stop are performed at the terminal 202. Transistor 3
The bias of 6,37 is turned on and off.

The low-sensitivity voltage controlled oscillator 7 can be easily realized by, for example, an oscillator in which the differential amplifier shown in FIG. 3 is positively fed back. This oscillator is omitted because the circuit operation is well known, but the oscillation output is at the terminal 30.
0, 301, the oscillation frequency is determined by the current source 3
8 current is changed and oscillation and oscillation stop are done at terminal 3
02 transistor 39 and 40 base bias on
And off.

FIG. 4 is a block diagram showing another specific example of the demodulation circuit 59 in FIG.

In FIG. 4, as in the case of the UHF / VHF television signal, the audio component contained in the satellite television broadcast signal is FM-modulated with subcarriers arranged in a frequency higher than the video signal band. Demodulate.

In FIG. 4, blocks having the same functions as in FIG. 1 are given the same numbers. Voice processing circuit 13A
Is composed of a bandpass filter 41, a tuning channel selection circuit 42, and a voice demodulation circuit 11. The outputs of the phase comparator 1 and the loop filter 2 are connected to the bandpass filter 41, and the output of the bandpass filter 41 is It is connected to the tuning and tuning circuit 42, the output of which is input to the audio demodulation circuit 11, and the output of the audio demodulation circuit 11 is connected to the switches 24 and 25.

The sub-carrier frequency of the audio component in this example is an arbitrary frequency UHF within 5 to 8.5 MHz for satellite television broadcast signals.
The VHF television broadcast signal has a frequency of 4.7 MHz, and the bandpass filter 41 passes a frequency of 4.7 to 8.5 MHz, the tuning and tuning circuit 42 selects an arbitrary subcarrier within 4.7 to 8.5 MHz, and outputs the sound. The demodulation circuit 11 demodulates.

〔The invention's effect〕

According to the present invention, in the demodulation circuit, two PLL circuits are used for the SHF band satellite television broadcast and the FM voice radio broadcast, and the FM demodulator circuit by the PLL, and the UHF / VH
In F television broadcasting, it operates as an AM demodulation circuit by synchronous detection, and since the control voltage of AGC and AFC is obtained from the dynamic PLL circuit, the circuit configuration is simplified, the weak electric field characteristics are excellent, and the demodulation characteristics are low distortion. Is obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing details of an example of a demodulation circuit as a main part in one embodiment of the present invention, FIG. 2 is a circuit diagram showing an example of a voltage controlled oscillator in a PLL circuit, and FIG. FIG. 4 is a circuit diagram showing an example, FIG. 4 is a block diagram showing details of another example of a demodulation circuit as a main part in one embodiment of the present invention, and FIG. 5 is a block showing a schematic configuration of one embodiment of the present invention. Fig. Explanation of reference numerals 1, 5 ... Phase comparator, 2, 6 ... Loop filter, 3, 7 ... Voltage controlled oscillator, 9 ... 90 ° phase shifter

Claims (5)

[Claims] 1. A common input section for receiving the antenna reception output of each broadcast radio wave of satellite broadcasting, UHF / VHF TV broadcasting and FM audio broadcasting, and a received signal from the input section is converted into an intermediate frequency signal. A frequency conversion circuit that outputs the intermediate frequency signal from the frequency conversion circuit, and a demodulation circuit that demodulates the intermediate frequency signal from the frequency conversion circuit by inputting the intermediate frequency signal from the frequency conversion circuit. And an input terminal for receiving the intermediate frequency signal through the input terminal, each of which comprises a phase comparator, a loop filter and a loop connection of a voltage controlled oscillator. Of the PLL circuit (face locked loop circuit), the connection point of the phase comparator and the voltage controlled oscillator in the first PLL circuit, and the second PLL circuit. A 90 ° phase shifter connecting between the connection point of the phase comparator and the voltage controlled oscillator, and a first voice processing circuit for branching the output of the phase comparator in the first PLL circuit and inputting them respectively. And a first video processing circuit, a second audio processing circuit and a second video processing circuit for branching the output of the loop filter in the first PLL circuit and inputting them respectively, and the second PLL.
A third audio processing circuit that branches and outputs the output of the loop filter in the circuit, and selects the first audio processing circuit and the first video processing circuit when receiving a UHF / VHF TV broadcast, and receives the satellite broadcast. Selecting means for selecting the second audio processing circuit and the second video processing circuit at times, and selecting the third audio processing circuit for receiving FM audio broadcast; and UHF / VHF TV broadcast reception and FM audio broadcast The operation of the voltage controlled oscillator in the first PLL circuit is stopped at the time of receiving the
And a control means for stopping the operation of the voltage controlled oscillator in the PLL circuit. 2. The receiving device according to claim 1, wherein the output of the loop filter in the first PLL circuit is taken out as an AFC control voltage at the time of satellite broadcasting reception, and at the time of receiving UHF / VHF TV broadcasting and FM. A receiving device, wherein an output of a loop filter in the second PLL circuit is taken out as an AFC control voltage when receiving a voice broadcast. 3. The receiving device according to claim 1 or 2, wherein the second PL is used when satellite broadcasting is received.
The output of the phase comparator in the L circuit is taken out as the AGC control voltage, and is received when receiving UHF / VHF TV broadcast and
A receiving device, wherein an output of a phase comparator in the first PLL circuit is taken out as an AGC control voltage when receiving an M audio broadcast. 4. A receiving device according to any one of claims 1 to 3, wherein the first audio processing circuit and the second audio processing circuit are bandpass filters. A receiving apparatus comprising one audio processing circuit including a tuning channel selection circuit and an audio demodulation circuit. 5. A receiver according to any one of claims 1 to 4, wherein the second PL is used.
The cutoff frequency of the loop filter in the L circuit is
A receiving device characterized in that it is switched between reception and demodulation of an audio broadcast signal and reception and demodulation of a UHF / VFH TV broadcast signal.