JPS5880921A - Receiver - Google Patents

Abstract

PURPOSE:To prevent an automatic sweep from stopping owing to a noise, etc., by providing a PLL synthesizer channel selecting circuit, FM stereophonic demodulator, threshold value switching circuit, and D-FF, and performing stereophonic reproduction even if the level of a received signal is relatively low. CONSTITUTION:A D-FF9 is added and only when a station searching signal is generated during channel selection, the reproduction mode of a stereophonic demodulator 5 is set to auto mode. Consequently, when the level of the station searching signal is low during preset channel selection, the reproduction mode is set to monaural mode, so that no change of the reproduction mode is caused between stereophonic reproduction and monaural reproduction. In addition, it is unnecessary to provide hysteresis characteristics to a circuit for generating the station searching signal. Further, a PLL controller 7 generates a sweep channel selection signal during sweep channel selection and according to the presence of said signal, threshold values of the station searching signal are changed between high and low to perform stereophonic reproduction even the level of the received signal is relatively low while preventing the stopping of an automatic sweep due to a noise and a disturbance signal.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a receiver using a PLL synthesizer channel selection method.

As shown in Figure 1, the receiver that forms the basis of this 0 invention is equipped with a sweep tuning system and a preset that starts frequency sweeping in response to a tuning start operation and stops frequency sweeping when a station detection signal is generated. PLL synthesizer tuning circuit 1 capable of tuning
and a 7M stereo demodulator (au)/monora A that switches the reproduction mode of the received signal of the frequency tuned by this PLL V synthesizer tuning circuit 1 to auto or monaural.
5, the PLL synthesizer channel selection circuit 1 detects the presence or absence of the station detection signal every time it performs a channel selection operation, and performs the 7M stereo demodulation only when the station detection signal is present. Equipped with a D flip laminate 5 (station detection signal detection circuit) 9 for setting the playback mode (auto/monaural mode switching circuit) s6 to auto-F mode.

To explain in detail, the output of this reception IId and the end signal is detected by a wave detector 4 via an intermediate frequency amplifier 3, and the output of this FM detector 4 is detected by a wave stereo demodulator 5.
and output K through the muting circuit 10.
The 0 channel selection is the front end 2 and prescaler 6, PLL: Itrotz 7 and low mechanical filter I! 8 constitutes a PLL sy y selector tuning circuit 1, which performs sweep tuning or pre-seller tuning. Sweep tuning is performed by the tuning operation l) When an up or down frequency sweep is started in the PLL S/synthesizer tuning circuit 1 and a station detection signal detected by the FM detector 4 is generated, the PLL ￥: This is done by the sizer tuning circuit 1 stopping the frequency sweep at /-. On the other hand, preset channel selection is performed by previously transmitting the frequency to be selected to the PLL controller 7 and selecting a channel.

During this tuning operation, the PLL controller 7 outputs a simulating signal, and the simulating signal activates the simulating circuit 10 to eliminate noise during tuning.

The D flip-flop 9 inputs the searching signal to the input C and the station detection signal to the data input signal. - If the falling of the tuning signal is short, that is, the holding state occurs in response to the completion of the channel selection operation. During the period of time, D)1, P, and P9 remain in the detection state, and the Q output maintains its previous state. If a detection signal is generated, the frequency sweep is stopped, and as a result, when the mini-tizig signal falls, the station detection signal is read into the D flip-flop 9 and the Q output becomes low. D7
The P-Tub 9 maintains the Q output at a low level until the channel selection operation is performed, and sets the playback mode of the FM stereo demodulator 6 to auto mode since the direct output becomes a low level. do.

On the other hand, Precessi channel selection #! When a station selection operation is performed after c, a mini-ticida signal is generated, and when one station selection operation is completed, the mini-ticida signal falls.At this time, the preset frequency is selected regardless of the presence or absence of a station detection signal. It will be broadcast. D7
When the voltage kneading signal is generated, the voltage level 9 becomes a detection level.

In response to the falling edge of the mining signal, the holding state is entered, but if the received signal level is lower than the threshold for stopping automatic sweep and no station detection signal is generated, the output is at a high level. This state is maintained by the fall of the muting signal, and the monaural mode, which is the playback mode of the 1M stereo demodulator 5 after the completion of channel selection, is set.

'If the reception signal level is still higher than the threshold for stopping automatic sweep and the station detection signal is generated, the muting signal falls), so the output 6 of the D flip-prop 9 is at a low level. The state is maintained, and the playback mode of the FM stereo tllall device 5 is set to auto mode after the channel selection is completed.

By turning on the taxi switch 11 connected to the reset input kK of the D flip-flop 9, the reproduction mode of the 1M stereo demodulator 5 can be manually set to monaural mode.

Such a receiver shown in Fig. 1 uses the station detection signal generated when the received signal level exceeds a threshold value as an automatic sweep stop signal and an auto Z monosil mode switching signal.
However, it generates a station notification signal! It is necessary to determine the threshold value based on the received signal level that is possible when the signal is actually generated.If the pressure threshold value is set low in this way, the frequency sweep may be caused by noise or interference signals during automatic sweep. The problem was that it stopped easily.

Therefore, an object of the present invention is to be able to perform stereophonic playback even when the level of the C reception signal is relatively low during preset tuning or sweep tuning, and to eliminate noise
It is an object of the present invention to provide a receiver capable of preventing automatic sweeping from being stopped due to interference signals.

An embodiment of the invention is shown in FIG. 2, that is, this receiver has FM11! ! 1. The station search signal output from the device 4 is input to the PLL controller 7- and the D flip-flop 9 via the threshold switching circuit 12, and the PLL controller 7 is used to input the station search signal outputted from the device 4 to the PLL controller 7 during the sweep channel selection operation. A signal is generated, and in response to the presence or absence of this sweep tuning operation signal, the PLL controller 7 and the D flip full tube 9
To switch the threshold value of the station detection signal input to the K
Therefore, station detection (+11) occurs and the i1%/-h value is switched high and low.

With this receiver, when you use the sweep channel selection mode and perform the channel selection operation,
When the PLL synthesizer tuning circuit 1 starts to sweep the frequency up or down, the PLL controller 7 generates a sweep tuning operation signal and a retrospective tuning signal, and the threshold switching signal 12 changes the station detection signal. When the threshold is switched to a higher value, no station detection signal is generated below the FM detector threshold, and when a station detection signal is generated at the higher threshold, the frequency sweep stops. ,
When the sweep station selection operation signal disappears, the threshold switching circuit 12 switches to lower the threshold of the station detection signal.
When the D flip-flop 9 detects the station detection signal, the Q output is at a low level, and the fall of the mini-5 Ping signal is υ, so the Q output of the D flip-flop 9 is at a low level. is held and the output 4 becomes low level, thereby setting the playback mode of the fiFM stereo uII 14 unit 5 to auto and shade.

On the other hand, in preset tuning, when a tuning operation is performed, the tuning operation is performed in the same way as in the first section, and the D flip 70 knob 9 is operated in the same way as 4 in Fig. 1 depending on the presence or absence of the station detection signal. FM post-circuit 5 switches between auto mode and monaural mode. In this case, the PLL controller 7 does not generate a U-sweep station selection operation signal, and the threshold switching circuit 12 switches to lower the threshold of the station detection signal. Switches to auto mode when the threshold is exceeded, and switches to monaural mode when it is below the lower threshold.

Other operations are similar to those in FIG.

Thus, this example if. L) A flip-flop 9 is attached to turn F only when there is a station detection signal when selecting a station.
Since the playback mode of the M stereo demodulator 5 is set to auto mode, when the station detection signal level is low during preset tuning, the playback mode is set to monaural mode. No, there is no playback mode change between stereo playback and monaural playback. Furthermore, there is no need to provide hysteresis characteristics to the circuit that generates the station detection signal. Furthermore 1. During the sweep tuning operation, a sweep tuning operation signal is generated from the PLL controller 7, and the threshold of the p-station detection signal is switched between high and low depending on the presence or absence of this sweep tuning operation signal. Stereo reproduction can be performed even if the received signal level is relatively low, and automatic sweeping can be prevented from stopping due to noise or interference signals.

As described above, the receiving 4G fence of the present invention is capable of sweep tuning and preset tuning, in which the frequency sweep is started in response to the tuning start operation and the frequency sweep is stopped when a station detection signal is generated. P that generates a sweep tuning operation signal during sweep tuning operation
An LL synthesizer tuning circuit, an auto/monaural mode switching circuit that switches the reproduction mode of the received signal of the frequency tuned by the PLL synthesizer circuit to auto or monaural, and the sweep tuning circuit. a threshold switching circuit for switching the threshold b- at which the station detection signal is generated to high or low in response to the presence or absence of an operation signal; A station detection signal 4j that detects the presence or absence of the station detection signal 4m every time the station selection operation is performed, and sets the reproduction mode of the auto/normal mode switching circuit to auto mode only when the station detection signal is present. Since the present invention is equipped with a detection circuit, stereo reproduction can be performed with a relatively low received signal level, and the automatic sweep can be prevented from being stopped due to noise or interference signals.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a receiver that is the basis of this invention, and FIG. 2 is a block diagram of a receiver that is the basis of this invention. It is a block diagram of an example. 1...PLL V synthesizer tuning circuit, 5...FM
Stereo demodulator (auto/monaural mode switching circuit),
9.-D friddef! Tsubu (station detection signal detection circuit), 1
2...Threshold switching circuit

Claims (1)

[Claims] Sweep tuning and de@
41L9) A PLL V synthesizer tuning circuit capable of tuning and generating a sweep tuning operation signal during sweep tuning operation;
This PLL synthesizer tuning circuit responds to the presence/absence of the sweep tuning operation signal by switching the reproduction mode of the received signal of the frequency tuned by the auto/mono mode switching circuit. The threshold value switching circuit switches the threshold value at which the station detection signal is generated between high and low levels, and detects the presence or absence of the station detection signal every time the station selection circuit and the 2-sizer selector perform a channel selection operation. A receiver equipped with a station detection signal detection circuit that sets the reproduction mode of the auto/monaural mode switching circuit to AUTO mode only when there is a station detection signal.