JPS5814769B2 - automatic tuning receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatically tuned receiver using a phase locked loop (PLL) as a local oscillator circuit, and more particularly to an automatically tuned receiver with an improved sweep stop circuit.

In the conventional sweep receiver in which the local oscillator circuit 1 is constructed of a PLLλ, as shown in FIG. When the signal is swept and received, the flip-flop 6 is reset by the reception detection signal S2, the pulse generation of the sweep pulse generator 4 is stopped, and automatic tuning is performed. During the sweep, the voltage controlled oscillator 7 repeats a transient response for each sweep pulse as shown in FIG. 2 and settles into a steady state, but the flip-flop 6 is reset due to noise generated during this transient state or external noise. Malfunctions such as stopping the sweep even though no signal was received were likely to occur.

Therefore, the present invention was devised in view of this point, and uses a sweep stop sampling pulse to detect the received signal at the end of the transient response of the voltage controlled oscillator 7, that is, just before the next sweep pulse is input. The present invention provides an automatic tuning receiver equipped with a sweep stop circuit for resetting.

An embodiment of the sweep stop circuit according to the present invention will be described below with reference to the drawings.

8 is a flip-flop 9 to which a start key signal is applied to the set terminal and a sweep stop signal S1 is applied to the reset terminal;
a sweep pulse generation control circuit comprising an AND gate 10 that detects coincidence between a reception detection signal S2 and a sweep stop sampling pulse S3 described below and generates the above-mentioned sweep stop signal S1;
Reference numeral 11 comprises an astable multivibrator whose pulse oscillation is controlled by the sweep pulse generation control circuit 8, and a pulse generation circuit that oscillates pulses as shown in FIG. and AN
A single pulse generation circuit is constructed of a D gate 15 and generates a single pulse as shown in FIG. 4C from the pulse train of the pulse generation circuit 11 in synchronization with the clock pulse shown in FIG. Used as pulse S3.

6 is a delay circuit that delays and generates the output of the single pulse generating circuit 12, and includes a delay D flip-flop 17;
It consists of an AND gate 18 which detects the coincidence of the output of the flip-flop 17 and the output of the sweep pulse generation control circuit 8, and a sweep pulse S4 is applied to the sweep force counter 5 from this AND output.

Next, the operation of the present invention having such a configuration will be explained.

It is assumed that a broadcast is currently being received and the value of the sweep force counter 5 is N.

When the start key is operated at time T in order to receive a new station from this state, the flip-flop 9 is set and the pulse generator 11 starts oscillating pulses.

The oscillated pulse is converted into a single pulse S3 by the single pulse generation circuit 12, which is further converted into a single pulse S3 by the delay circuit 16.
After a clock delay, S4 is applied to the sweep force counter 5, and the frequency division ratio of the programmable frequency divider 3 is changed to N+1.

When the frequency division ratio is changed and reception is received, the sweep stop sampling pulse S3 generated after the transient state of the voltage controlled oscillator 7 and the reception detection signal S2 match, and the AND gate 10 is opened and the flip-flop of the sweep pulse generation control circuit is activated. Reset 9.

Therefore, the AND gate 18 closes and the sweep force counter 5
Sweep pulse S4 is not applied to , and the sweep stops.

However, if there is no reception detection signal S2 when the sweep stop sampling pulse S3 is generated, the AND gate 10 is not opened and the flip-flop 9 is not reset, and the sweep pulses are sequentially input to the sweep force counter 5 to continue the sweep. .

FIG. 4 shows a case where there is no receiving station at N+1 and there is a receiving station at N+2.

As described above, since reception detection is performed using the sweep stop sampling pulse S3 immediately before the sweep pulse is input, noise may be mixed in the middle of the reception detection signal, as shown in S2' and S2'' shown in Figure 4e, for example. There is no need to stop the machine by mistake.
The probability of malfunction can be reduced.

As described above, the automatic tuning receiver of the present invention performs reception detection only when a sweep stop sampling pulse is generated, so it is possible to prevent malfunctions due to external noise mixed in during the sweep, and the sweep stop sampling pulse is detected when the next sweep pulse is generated. Since the signal occurs immediately before the signal, reception detection is performed when the transient response of the voltage controlled oscillator settles into a steady state, so that the receiving station can be reliably detected.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a conventional automatic tuning receiver, FIG. 2 is a waveform diagram of the main part of FIG. 1, FIG. 3 is a circuit configuration diagram showing the configuration of the present invention, and FIG. 3 is a waveform diagram of the main part of FIG. 3. FIG. 1...Local oscillation circuit, 2...PLL,
5...Sweep force counter, 8...Sweep pulse generation control circuit, 11...Sweep pulse generation circuit, 12...Single pulse generation circuit, 16. ...
...Delay circuit.

Claims (1)

[Claims] 1. In an automatic tuning receiver that sequentially sweeps using sweep pulses and stops the sweep upon detection of a received signal, reception detection is performed for a predetermined period only by a sweep stop sampling pulse generation means that is generated immediately before the sweep pulse is generated, and the sweep is stopped. An automatic tuning receiver characterized by performing control.