JPS61216528A - Audio channel selector - Google Patents

Abstract

PURPOSE:To prevent beads from being generated owing to the cross-talk of a local frequency signal between systems of plural channels by a allowing the output of a voltage-controlled oscillator of one channel to be inputted to the mixer of the other channel through a high frequency switch circuit. CONSTITUTION:Plural audio subcarriers are inputted to a band-pass filter 16. When the 1st and the 2nd data are inputted to a microcomputer 47 so that the same audio subcarrier is selected on sides of a mixer 17 and a mixer 21, the microcomputer 47 generates the 1st and the 2nd selection data DA1 and DA2 for respective channels and the DA1 and DA2 are compared with each other to decide whether the difference DELTAf when those data are converted into oscillation frequencies is within a specific range (DELTAf<20kHz) or not; when DELTAf<20kHz, the microcomputer 47 operates as a system switching means to control a high-frequency switch circuit 49 and the oscillation output of the voltage-controlled oscillator 41 is inputted to the mixer 21 through a buffer circuit 48 and a high frequency switch circuit 49. At this time, the other voltage- controlled oscillator is inhibited from operating.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an audio channel selection device used, for example, in an 8HF receiver [Technical Background of the Invention] In a 5HF (4 GHz band) broadcasting system using a communication center The system employs a method in which an audio signal is FM-modulated, and this FM audio signal is further FM-modulated and transmitted together with a video signal. In this case, the FM audio signal is 5.0M
There are multiple subcarriers between Hz and 8.5 MHz. For example, in the case of stereo broadcasting, the stereo signal is not multiplexed onto fixed subcarriers (4,5MHz) as in current terrestrial television broadcasting, but instead the left channel and right channel are multiplexed.
channel) - with different subcarriers of the same wave number T'
It has been Mffilliil. Therefore, when receiving such stereo broadcasts, the user needs to tune into each of the L and R channels separately. moreover,
Other frequency subcarriers also include signals unrelated to video signals (such as FM broadcasts), and it is also possible to listen to TV audio on the L channel and FM broadcasts on the R channel.

As an audio channel selection circuit for this type of 8HF broadcast receiver, a system as shown in FIG. 4 has been developed. This system consists of two completely independent frequency synthesizer one-way channel selection circuits.

The received signal whose frequency has been converted by the converter 11 is subjected to gain control by an automatic gain control circuit 12, and then sent to an FM demodulator 13.
is input. The demodulated signal demodulated by the FM demodulator 13 is a video signal, and the 0 video signal, which is a plurality of audio subcarriers, is extracted by a bandpass filter 14 and guided to an output terminal 15FC.

Multiple audio subcarriers (5,0MHz to 8.5Mh)
is extracted by bandpass filter 16 and input to mixers 17 and 21. The oscillation output of the local generator 31 is also input to the mixer Z7, thereby converting it into a desired subcarrier voice intermediate frequency signal. mixer 12
The intermediate frequency signal outputted from the FM demodulator 18 is extracted by the bandpass filter 18, and the intermediate frequency signal output from the FM demodulator ! 9 is input.

The demodulated output of this FM demodulator 19 is output to the output terminal 20.
Hail to you. mixer 21, bandpass filter 22,
The 1M demodulator 23 and local generator 34 also operate in the same manner.

Here, a first loop is formed by a local generator 31, a Briskeller 32, and a phase-locked loop processing circuit 33, and a first loop is formed by a local generator 34, a Griskeller 35, and a phase-locked loop processing circuit 36. The second loop is independently controlled based on channel selection data from the microcomputer 37. That is, the local generator 31
．． Numerals 34 and 34 are voltage-controlled generators, each of which can maintain its oscillation frequency stably through the action of a phase-locked loop.

[Problems with the background art] The above-mentioned audio tuning circuit system has a system in which each local generator 31,
By adjusting the oscillation frequency of 34, the output terminal j
An OKL channel output and an R channel output can be obtained at the output terminal 24.

However, this system requires a voltage-controlled generator for each channel:! II, 34, there is crosstalk between local frequencies and beat interference! There is a problem that occurs! Ri, L Chi, Jannel, R
There is no problem if subcarriers with different frequencies are selected for each channel, but if the same subcarrier is selected for each channel, there may be a slight difference in each channel due to variations between the two systems. may be locked at the cull frequency. Now, the local frequency t-f of the L channel, R? , the local frequency of Jannel is f
, and fl>f2, fl-f2=Δf...
Assuming (1), if we consider the case where an R channel local signal leaks into the L channel, this signal will flow into the mixer 11 and undergo multiplication processing.

In such a case, unnecessary carriers are generated as shown in FIG. This can be regarded as the carrier being FM modulated with the ΔfO signal, and when FM demodulated, Δf
In such a case, especially when Δf<15KRz, the problem arises that the S/N of the audio signal is significantly degraded.In order to improve the above problem, Efforts have been made to reduce the amount of crosstalk by reconsidering the ground pattern and devising shielding cases, but the signals that cause crosstalk are thought to have a negative impact on the generator's resonant circuit, so No effect has been obtained. Therefore, when selecting the same nap carrier, an offset is intentionally set so that the local frequency between channels is locked at a frequency that differs by 20KRz or more. However, in the method described above, the intermediate frequency of each channel (10.7 M
Hz) signal will also deviate from the predetermined uniform wave number,
If this deviation is large, there is a problem that the audio distortion rate also becomes large. Furthermore, if the difference between the intermediate frequencies of each channel is too small, the S/N ratio will deteriorate significantly because unnecessary carriers are mixed in.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an audio channel selection device that can reduce beat disturbance caused by pasted stalks of quaternary frequency signals between multiple channel systems in a simple manner. shall be.

[Summary of the invention]

In this invention, for example, as shown in FIG. 1, the output of the voltage control generator 41 of one channel can be inputted to the mixer 21 of the other channel via the high frequency switch circuit 49, thereby achieving the above-mentioned purpose. The goal is to achieve the following.

[Embodiments of the invention]

Embodiments of this invention will be described below with reference to the drawings.
The figure shows one embodiment of the present invention, in which a bandpass filter fi
16Fc is multiple s! O audio subcarrier is input.

These multiple audio subcarriers are signals transmitted together with the 8HF broadcast signal, and are 5.0 to 5.5.
．． It exists as an FM signal in the 8M& band. pando passf 4
The output of filter 16 is input to mixer 1, r, 21. This mixer17. :! The stage after 1 is the same as that explained in FIG. 4, and is given the same reference numeral as in FIG. 4.

Since this invention features a local generator system,
The local oscillation output supply means for the mixer 11, which will be explained in detail below, include the voltage control generator 41, the Briskeler 42, and the phase-locked loop (
PI, L) processing circuit 43 and the like. The phase-locked loop processing circuit 43 divides the output of the prescaler 42, compares the phase with the 9-frequency output, and the oscillation output of the reference generator, and converts the output into a two-phase comparator and DC converter of the phase comparator. It includes a low-pass filter section, frequency dividing means for dividing the output of the prescaler 42, and the like. Therefore, microphone, four combiator four
1 to the first selection data CDAI) is given to the branching means of the phase-locked loop processing circuit 43, and its branching ratio is set, the control voltage (VTI) output from the phase-locked loop processing circuit 43 becomes The local frequency can be varied. This allows mixer 1
2, the sum and difference between the input signal and the local oscillation signal;
For example, the difference component is an audio intermediate frequency signal (
10.7M&).

The phase-locked loop processing circuit 46 also has the same configuration as the phase-locked loop processing circuit 43 described above, and can control the number of local oscillations of the voltage control generator 44 by its output control voltage (CVTR). The voltage control generator 44, the Briskeller 45, and the phase-locked loop processing circuit 46 are
Forms a phase-locked loop.

External data for selecting an audio nap carrier can be input to the micro combinator 41 for each channel via the keyboard. Now, mixer 17 side is L channel (first channel), mixer 21 side is T-
It is assumed to be the R channel (second channel). In this way, the first . When the second external data is input to the micro combinator 4'lK, the micro combinator 47 inputs the first external data. Based on the second external data, the first . Second selection data IDAl and DAj are generated. And the first. Second selection data DAZ.

By comparing DAj, it is possible to obtain a determination result as to whether the difference Δf when each data is converted into an oscillation frequency is within a predetermined range (Δf<20 KHz).

Now, when the determination result that Δf (20KIIz) is obtained, the micro combinator 47 operates as a system switching means and controls the high frequency switch circuit 49, so that the oscillation output of the voltage control generator 41 is The signal is set to be input to the mixer 2) via a circuit 48 and a high frequency switch circuit 49. Further, at this time, the operation of the other voltage control' generator 44 is stopped by the micro combinator 42.

As a result, when using the same audio nap carrier and processing the R channel, mixers 1'l and 21 of each channel
The local oscillation output input to the single voltage controlled generator 4
It will be from 1.

When audio subcarriers of different frequencies are processed in each channel, the first . Second selection data DI'l
@ The contents of DAj are different. Also, at this time, the high frequency switch circuit 49 is switched by the micro combinator 47 so as to input the output of the voltage control generator 44 to the mixer 21 .

Next, the microcomputer 47 can also perform automatic 71 in-chaining processing.

This will be explained on behalf of the R channel side. In the micro combinator 47, an audio intermediate station wave signal is introduced from the FM demodulation circuit 19 side via a limiter circuit, and the FM
Detection output can be obtained.

Then, digital conversion of this FM detection output is performed,
A shift in the intermediate frequency is detected.

If a shift in the intermediate frequency occurs, the first selection data is finely adjusted by wI4, and control is performed to finely adjust the local oscillation frequency in the direction of eliminating the shift.

The same automatic 71-inch 212-inch cutting process 1i-can also be applied to the R channel side.

Next, the processing procedure when the data for channel selection □ for selecting an audio subcarrier is input to the microcomputer 47 will be shown and explained. In FIG.
First data for channel selection is input.

The microphone combiator 47 inputs the selection data DAJ' to the phase-locked loop processing circuit 43 based on this first data from the outside. As a result, a frequency sweep (step 82) operation is obtained, and the FM demodulator 19 The so-called 8 for viewing the fine chimney condition from the side.
A linear detection output is given. (Step 83). If this S biopsy wave output reaches a predetermined value Kk', then the first C
The value of I selection data DAJ is held (step 84).
Frequency sweep processing stops. Next, the microcomputer 47 reads the second external data given by the user for the L channel, and the second external data corresponding to this is read.
generate selection data. (Step S'5').

Next, the first selection data for the L channel and this @
The two selection data are compared and it is determined whether the difference in oscillation frequency determined by each data is 20 KHz or less (Δf<20 KHz). (Step Si!t, S7). Here, if Δf < 20 KHz, it is determined that the same audio subcarrier should be selected for both the L and R channels, and the high frequency switch circuit 49 transfers the local oscillation output of the R channel to the mixer 21 of the R channel. Switch to introduce it. (Step S8). No. 1 above. Second
If the comparison result of the selected data is Δf)20KHz, then
An independent phase-locked loop is formed for each channel.

The present invention is not limited to the above-mentioned embodiment, but as shown in FIG. K may be used so that it can be delivered to the output terminal 24 via the buffer circuit 52. When external data indicating that the same audio subcarrier is to be selected on the R channel is input, the Micro Combiator 4
1 stops the voltage control generator 44 and switches the analog switch 5 so that the demodulated output of the L channel is also output to the output terminal 24 side. The other parts are rounded and given the same numbers as in FIG. 1, and their explanation will be omitted.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to prevent the generation of noise due to crosstalk of local oscillation output signals provided in a plurality of channels. In addition, it is not necessary to take measures such as adding a 20 KHz deviation to the frequency of the local oscillation signal as in the past, and the relatively strictly required characteristics of the bandpass filters 18 and 22 can be relaxed to a certain extent, so the design can be improved. You can also afford the top.

[Brief explanation of the drawing]

FIG. 1 is a configuration explanatory diagram showing one embodiment of the present invention, FIG. 2 is an explanatory diagram showing the operating element Jli of the device shown in FIG. 1, and FIG. 3 is a configuration explanatory diagram showing another embodiment of the present invention. 4 is a block diagram showing a conventional audio channel selection device, and FIG. 5 is a spectrum explanatory diagram when crosstalk occurs.

Claims (3)

[Claims] (1) First and second mixers having in common an input section into which a plurality of audio carrier signals having different frequencies are input; and first and second mixers output from the first and second mixers. first and second demodulation means for demodulating intermediate frequency signals of the first and second mixers; first and second voltage control generators for supplying local oscillation outputs to the first and second mixers, respectively; 1. First and second selection data for respectively setting each oscillation output frequency of the second voltage controlled oscillator are input, and each of the voltage controlled oscillators is controlled with each control voltage based on each of these selection data. First,
determining that the difference between the oscillation frequencies of the second phase-locked loop processing means and the first and second voltage controlled oscillators determined by the first and second selection data is within a predetermined range; , stopping the second voltage controlled oscillator and transmitting the demodulated output of the intermediate frequency signal frequency-converted by the oscillation output of the first voltage controlled oscillator to the first voltage controlled oscillator;
, and system switching means for outputting the signal to the output terminal of the second demodulation means. (2) The system switching means includes a high frequency switch circuit that receives oscillation outputs from the first and second voltage controlled oscillators, selects one of them, and inputs the selected one to the second mixer. An audio channel selection device according to claim 1, characterized in that: (3) The system switching means includes an analog switch circuit into which the outputs of the first and second demodulation means are input, and selects and outputs either one. The audio channel selection device described in Section 1.