JPS6364927B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a linkopex radio receiving apparatus in the SSB system.

Conventional linkopex systems divide audio into frequency information and amplitude information, and while the frequency information is transmitted as constant amplitude, the amplitude level of the amplitude information is converted to frequency and simultaneously transmitted as FM waves.

FIG. 1 shows the arrangement of frequency spectra of frequency information A and amplitude information B of the link-optics method accompanied by residual carriers. ₀ is the residual carrier. In this case, since the amplitude information B is transmitted by converting the amplitude level into a frequency, if there is a difference between the transmission frequency and the reception frequency, the audio signal level reproduced after reception will be greatly affected.
Therefore, it is necessary to increase the stability of the transmitting and receiving frequencies, or to apply AFC on the receiving side to correct the frequency deviation on the transmitting side.

Figure 2 shows a general receiving device that performs AFC by extracting the residual carrier component and comparing the phase with a reference signal. 1 is an RF amplifier, 2
is a mixer, 3 is a crystal filter, 4 is an upper and lower amplifier,
5 is a demodulator consisting of a product detector or a balanced demodulator; 6 is a distributor; 7 is a bandpass filter that allows only the control channel to pass; 8 is a carrier filter that extracts residual carrier components; 9 is a carrier amplifier; 10 is a carrier oscillator, 11 is a phase comparator,
12 is a low pass filter, and 13 is a VCO.

Now, in Figure 1, the frequency information bandwidth is 300
Hz to 2380Hz and control channel bandwidth to 2520Hz
~2640Hz, when the AFC range shown in Figure 2 is required to exceed the carrier frequency ±300Hz, the AFC range partially overlaps with the voice band, and if there is a continuous tone in the overlapping band, the AFC circuit will treat the continuous tone as a carrier. This method has the disadvantage of causing a phenomenon of erroneous recognition and locking (hereinafter, the above-mentioned phenomenon will be referred to as voice erroneous locking).

In order to eliminate such audio false lock phenomenon that occurs during AFC operation, the present invention improves the AFC circuit system and uses the fact that the carrier and control channel have a certain frequency relationship to release the false lock. This is what I did. This will be explained below along with examples.

FIG. 3 is a block diagram showing one embodiment of the present invention. Here, 1 to 13 are the same as those in Fig. 2, 14 is a switch, 15 is a sweep voltage generation circuit, 16 is a control channel amplifier, 17 is a wave detector, 18 is a DC amplifier, and 19 is a control channel signal generator. The presence of the switch 19 is detected and the switch 19 is activated accordingly.
This is a judgment circuit that turns on and off.

In this configuration, the carrier frequency in Figure 1 is _0.
Then, audio channel A and control channel B are given by the following equations.

A = ₀ +300Hz ~ ₀ +2380Hz B = ₀ + (2580±60Hz) Now, if the frequency of the output of the carrier component (output of carrier amplifier 9) extracted in Fig. 3 is correctly locked to the frequency of carrier oscillator 10. The output frequency of the band wave generator 7 is expressed by the following equation, and its output is detected and turns on the determination circuit 19.

F=B- ₀ =2580±60Hz Here, if we assume that the lowest audio frequency ₀ + 300Hz is locked to the output frequency of the carrier oscillator 10 due to audio lock, the frequency of the control channel input to the bandpass converter 7 is The following formula is obtained.

F' = ₀ + (2580 ± 60Hz) - ( ₀ + 300Hz) = 2280 ± 60Hz The frequency expressed by this formula completely falls within the audio channel bandwidth of 300Hz to 2380Hz, and therefore is a band wave that only passes the control channel. The output of the device 7 (bandwidth 2580±60Hz) becomes 0 and the judgment circuit 19
Turn off.

When the judgment circuit 19 is off, the changeover switch 14
releases the lock state, connects the output voltage of the sweep oscillator 15 to the VCO 13, and the VCO 13 starts searching.

When the determination circuit 19 is on, the changeover switch 14 connects the output voltage of the phase comparator 11 to the VCO 13 to maintain the normal AFC lock state.

As is clear from the above embodiments, according to the present invention, erroneous audio locking operations of AFC can be prevented by using the output information of the demodulated control channel, and as a result, good AFC operation can be achieved in the link optics receiver. This makes it possible to ensure high quality reception.

[Brief explanation of drawings]

Figure 1 is a diagram showing the arrangement of frequency spectra in a link-compensation system with residual carriers, Figure 2 is a block diagram of a general receiving device that performs AFC using residual carriers, and Figure 3 is a diagram showing the arrangement of the frequency spectrum in the link compensating system with residual carriers. FIG. 1 is a block diagram of a linkopex receiver according to one embodiment. 1... RF amplifier, 2... Mixer, 8... Carrier filter, 11... Phase comparator, 17... Detector, 19... Judgment circuit.

Claims (1)

[Claims] 1. A means for extracting the residual carrier component from the received signals and applying AFC by extracting the residual carrier component from the received signal including the residual carrier and the audio channel signal consisting of the frequency information of the voice and the control channel signal consisting of the amplitude information of the voice, and the presence or absence of the control channel signal. A linkopex receiving device is provided with means for determining whether the AFC is locked or unlocked.