JPS5814619A - Generator of automatic channel selecting operation stopping signal of receiver - Google Patents

Abstract

PURPOSE:To increase the reliability and at the same time to decrease the number of pins for integration, by breaking the generation of a stopping signal if no pilot signal exists when a prescribed period of time passed from the generation of the stopping signal. CONSTITUTION:An IF level within an IF amplifier 2 is detected by a level comparator 8, and a stopping signal is applied to an OR gate 5 when the IF level is shifted to a high level. At the same time, a pilot signal showing a prescribed type program is detected by a pilot detector 4 and applied to the gate 5. Then the presence of the pilot signal in a prescribed period after the generation of the stopping signal is detected by a DFF12, etc. The generation of the stopping signal is broken when no pilot signal exists. Then the stopping signal is applied to a controller 11 to stop an automatic channel selecting operation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic tuning operation stop signal generation device for a receiver, and is particularly capable of receiving both regular broadcasts such as monaural and special broadcasts such as stereo, and has an automatic tuning function. The present invention relates to an automatic channel selection operation stop signal generation device in a receiver having the present invention.

For receivers with an automatic tuning function, the tuning frequency of the front end is automatically changed, for example, at each station placement interval frequency step, and when the received signal level exceeds a certain value and the detuning state is released. The system is configured to sometimes stop changing the tuning frequency and perform automatic tuning.

Among receivers having such a function, there are receivers that can receive both normal broadcast waves such as monaural broadcast waves and special broadcast waves such as stereo broadcast waves. The receiver has two types of tuning: the so-called stereo search mode, which automatically tunes only special broadcast waves such as stereo, and the so-called normal search mode, which automatically tunes without distinguishing between monaural and stereo waves. mode may be required.

In such a case, a method is to use a switch to simply switch between the received signal level detection output and the pilot signal detection output indicating that it is a stereo program broadcast, depending on the normal search mode and stereo search mode, and use it as a search stop signal. be. However, since both detection outputs are mechanically switched using a switch, there is a drawback that reliability is lacking. There is also a method of inputting both detection outputs independently as search stop signals to the search stop control circuit and switching the search mode externally, but this requires at least two input signal lines to the search stop control circuit. Therefore, the number of pins increases, which is particularly undesirable when integrated circuits are integrated.

SUMMARY OF THE INVENTION An object of the present invention is to provide an automatic tuning operation stop signal generation device for a receiver that is highly reliable and does not cause an increase in the number of pins when integrating circuits.

The automatic tuning operation stop signal generating device for a receiver according to the present invention includes means for generating a stop signal when the received signal level is equal to or higher than a predetermined value, and detecting a pilot signal indicating that the program is of a predetermined broadcast program type such as stereo. control means for detecting the presence or absence of the pilot detection signal after a predetermined period of time has elapsed since the generation of the stop signal, and for controlling the generation of the stop signal to stop when the pilot detection signal is absent; , means for stopping the cut-off control operation of the control means in response to an automatic tuning command (stereo search mode command) of a predetermined broadcast program, and is characterized in that the stop signal is used as a search stop signal.

The present invention will be explained below with reference to the drawings.

FIG. 1 is a circuit diagram of an embodiment of the present invention, in which a received IF (intermediate frequency) signal from a front end 1 is amplified by an IF amplifier 2 and input to a detector 3. In FIG.

This detector 3 is an AM detector in the case of the AM band, and an FM detector in the case of the FM band. This detection output is input to a pilot detector 4 to detect a pilot signal. This pilot signal is, for example, a 5 Hz signal for identifying an AM stereo program in the case of AM stereo broadcasting, and a 19 KHz signal in the case of FM stereo. Further, in the case of an ARI (traffic information) broadcast program, it is a 57 KHz signal used to identify that it is an ARI program. The detection output from this pilot detector 4 becomes one input of the OR gate 5.

A signal meter drive circuit 7 is provided to detect the IF level in IF7/7'2 and display this level on the signal meter 6, and this IF signal level is detected by the level converter II 8, For example, a high level output is generated when the value exceeds a certain value.

A differentiating circuit 9 is provided to detect the rising transition timing of this high level output, and this differentiated output is waveform-shaped by a Schmitt trigger circuit 1O to form a level detection signal and output to the OR gate 5.

A controller 11 for automatic tuning is provided, and is configured so that the tuning frequency of the front end 1 is automatically changed in response to a search operation command from the user in accordance with the station placement interval frequency step, The well-known PLL (phase locked droop) frequency synthesizer configuration or P
It has an LL voltage synthesizer configuration.

The output of the OR gate 5 is the data input of DFF (delayed flip-flop) 12 and 13.
As a clock input for DFF 12, ant game) 14
The output of is used. The Q output of the DFF 12 is applied to one input of the DFF 14, and the reference clock signal is applied to each input. Further, the carry output of the n-ary counter 15 is used as the clock input of the DFF 13, and the reference clock signal is used as the clock input of the counter 15. The counter 15 is enabled by the Q output of the DFF 12. The carry output of the counter 15 and the Q output of the DFF 13 are connected to the input of the gate 16, and the output of this gate is an AND gate whose input is a signal obtained by inverting the clock signal by the inverter 17. There are 18 inputs. The output of this gate 18 is an ant game whose one input is a mode command signal that determines the search mode.
There are 19 inputs, and the output of this gate is the input of an OR gate whose one input is a reset signal.

Then, the output of the gate 20 becomes a reset signal for the DFFs 12 and 13 and the counter 15, and the Q output of the DFF 12 is delivered to the controller 11 as a search stop signal.

Now, when the controller 11 starts the search operation, P
VCO (voltage controlled oscillator) using LL synthesizer circuit
is locked to a predetermined local oscillation frequency, and then the output of the signal meter drive circuit 7 rises to a high level, and a high level level detection signal with a constant width is generated from the Schmitt trigger circuit IO. On the other hand, in the case of special program broadcasting such as stereo, the pilot signal included in the output of the detector 3 is detected with a certain time delay with respect to the generation timing of the level detection signal.

In particular, in the case of a method in which a pilot signal is detected using a PLL circuit, this delay is significant because of the lock time of the PLL circuit. Further, since the AM stereo pilot signal has a low output of 5 as described above, the delay is large. Assuming that this delay time is T1, the pilot detection signal arrives at the output of the OR gate 5 a time T1 after the level detection output arrives.

Taking this fact into consideration, the operation of the circuit shown in FIG. 1 will be explained with reference to timing charts shown in FIGS. 2 and 3. First, second
The figure shows waveforms during a so-called normal search, which performs a search operation regardless of normal broadcasts or special broadcasts. (α) is the clock signal, (b) is the level detection signal that is the output of the Schmitt trigger 10, and (1) is the waveform. Q output of DFF12, (d) is carry output of counter 15, (1) is Q of DFF13
The output, ω, is a search stop signal. These (α) ~
The waveforms in (1) are the same in FIG. 3 as well.

During a normal search, since the single input of the AND gate 19 is set to a low level, the gate) 19 is closed, and the reset output by the gate) 16 and 18 is blocked, and only the external reset by the addition of the OR gate is possible. It becomes effective. Now, the level detection signal with time width T2 is shown in Figure 2 (
When it arrives as shown in (6), it is stored in the DFF 12 by the clock signal (, ), so the Q output of the DFF 12 transitions to a high level as shown in (1).

Incidentally, since the pulse width T1 of the detection signal needs to be selected to be larger than the period of the clock signal, it is assumed that the time constant of the differentiating circuit 90 is determined accordingly.

Since the Q output of the DFF 12 is inverted to a high level and simultaneously changes to a low level, the analog gate 14 is closed and blocks the clock signal. Therefore, if the arrival of one level detection signal is stored in the DFF 12, its Q output is maintained at a high level, so the generation of the stop signal is held as long as an external reset signal is not applied.
This becomes a search stop signal and is input to the controller 11, stopping tuning control, and automatic tuning has been performed regardless of the type of broadcast program.

FIG. 3 is a timing chart during a stereo search.During a stereo search, the search command signal of the antagonal gate 19 is at a high level, so this gate 19 is controlled to be open. Therefore, the reset signal from the AND gates 16 and 18 is effectively transmitted to DFFl2 and the like. First, a level detection signal is generated as shown in FIG. 3 (6), and DFFl
A high-level stop signal is generated and maintained by the Q output of 2 as shown in (1). At the same time, the counter 15 starts counting the clock signal, its carry output becomes high level as shown in FIG. 3(d), and the output state of the OR gate 5 at that time is stored in the DFF13. At this time, if the broadcast is monaural, no pilot detection signal is generated, so the DF
Fl3 does not change at all and its Q output remains at high level. Therefore, the AND gate 16 passes the carry output of the counter 15, and the AND gate 18, 19 in the open state
and the OR gate 20, and is derived as a reset signal. Therefore, DFFl2. l&counters 15 are all reset. Therefore, the stop signal, which is the Q output of DFF12, is cut off and transitions to a low level, so that the controller performs the search operation again.

When the level detection signal is generated again, DFF12 stores it. Next, assume that a pilot signal is generated after a time TI. At this time, if the base number of the counter 15 is appropriately selected so that the carry output is generated at a time approximately equal to the delay time of pilot signal generation, the DFF
Since the generation of the pilot signal is stored in 13, its Q output becomes high level as shown in (1). Therefore, its Q output goes low, closing gate 16 and clamping the output of gate 18 to a low level. the,
As a result, the output of 19 becomes low level, so unless there is an external reset signal, the reset signal to DFF1-2 and 13 will not be generated, and the stop signal which is the Q output of DFF12 will be at high level. There is no way. Therefore, this becomes a search stop signal and the controller 11
The search operation of the station is stopped, and stereo station reception becomes possible. Note that 18 serves as a time delay circuit to prevent malfunction of DFF13.

In the case of searching for an ARI station, a high level command signal may be applied as an ARI search mode control input to the gate 190.

With the above in mind, the PLL synthesizer in the controller 11 will control the increase/decrease of the local oscillation frequency in synchronization with the timing of the clock signal, and will stop and restart depending on the presence or absence of the step signal stored by the clock signal. It is constructed over and over again. In normal search mode, the clock signal determines the search speed, but in stereo search mode,
First, it is temporarily stopped at the timing of the clock signal, and after a time determined by the counter 15, the presence or absence of the pilot signal is detected, and then a decision is made as to whether to stop or restart. Therefore, in the case of stereo search, the search is performed at the timing of the clock signal during the no-signal section, and the presence or absence of the pilot signal is detected at a sufficiently late timing after the signal is detected, so there is no malfunction and the search speed becomes faster.

Further, when the circuit of the output section of the gate 5 is integrated with the controller 11, only one signal is required to be exchanged between the output of the gate 5 and the integrated circuit section, thereby preventing an increase in the number of bins.

As described above, the present invention has the advantage that it has high reliability, enables faster search operation, and can be easily integrated into a circuit.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment of the present invention, and FIGS. 2 and 3 are timing charts for each operation mode of the circuit of FIG. 1. Explanation of symbols of main parts 4...Pilot signal detector 7...Signal meter drive circuit 8...Level comparator 11...Controller 12, 13-DFF 15...Counter Applicant Pioneer Corporation Agent Patent attorney Motohiko Fujimura

Claims (1)

[Claims] (1) Stop signal generating means that generates a stop signal when the received signal level is equal to or higher than a predetermined value, and a pilot detection signal that detects a pilot signal that indicates a predetermined broadcast program type. a control means for detecting the presence or absence of the pilot detection signal after a predetermined period has elapsed since the generation of the stop signal and disabling the generation of the stop signal when the pilot detection signal is absent; automatic selection of a receiver, comprising means for stopping the disconnection control operation of the control means in response to an automatic tuning command of a program, and the stop signal is used as an automatic tuning operation stop signal. Station operation stop signal generator. (2) The stop signal generating means includes means for generating a level detection signal when the received signal level is equal to or higher than a predetermined value, and a storage means for storing generation of the level detection signal, and the control means 2. The apparatus according to claim 1, further comprising reset signal generation means for resetting said storage means when said pilot signal is absent, and wherein said storage output of said storage stage is said stop signal. (3) The predetermined broadcast program is an FM stereo program, and the pilot signal detection means detects an FM stereo pilot signal. (4) The predetermined broadcast program is an AM stereo program, and the pilot signal detection means detects an FM stereo pilot signal. The device according to claim 1 or 2, wherein the means is configured to detect an AM stereo pilot signal. (5) The predetermined broadcast program is a traffic information program, 3. The apparatus according to claim 1, wherein said pilot signal detection means is configured to detect a pilot signal indicating a traffic information program.