JPS6228100Y2 - - Google Patents

Description

[Detailed description of the invention] This invention automatically stops the search when a broadcast signal with a strong electric field is received, but stops the search for a few seconds when a broadcast signal with a medium or weak electric field is received. However, the present invention relates to a synthesizer tuner that eliminates the need for an auto-search sensitivity changeover switch by starting a search several seconds later unless a holder switch is turned on.

When using auto search using a synthesizer tuner in a car radio receiver, an auto search sensitivity changeover switch is always required. This is because if you set it so that all broadcast signals from weak electric fields to strong electric fields can be searched automatically, the reception point will move and the search will stop even if you try to search for a noisy weak electric field broadcast signal. As a result, you will be listening to a broadcast signal with a lot of noise. For this reason, it becomes necessary to switch the auto-search sensitivity and auto-search only for broadcast signals with strong electric fields. However, if the auto search sensitivity is set to stop the search only when a broadcast signal with a strong electric field is received, auto search will not be performed at all in areas where only broadcast signals with a weak electric field are present, such as in mountainous areas. . Therefore, the sensitivity of auto search has been changed depending on the location, but it is inconvenient to operate the switch while the car is moving, and it is difficult to operate the switch while the car is moving.
If the front panel is narrow, there is no room to install such a changeover switch.

The present invention therefore provides a synthesizer tuner that eliminates these drawbacks.

The present invention will be explained below with reference to the drawings. 1 is a high-frequency circuit having an antenna section having a semiconductor variable capacitance element for tuning, an amplification section, a mixing section, etc.;
2 is an intermediate frequency amplification circuit connected to the high frequency circuit 1, 3 is a detection circuit, 4 is an audio amplification circuit, and 5 is a controller, which is connected to a set terminal S as described in Japanese Patent Publication No. 60-28417, for example. an oscillator 16 having a reset terminal R and a pause terminal P;
It consists of a register 17 that counts every time the pulse signal oscillated by the oscillator 16 is added and generates a multi-bit digital signal that changes every moment.
The PLL circuit 6 includes a programmable counter 18 whose frequency division ratio is determined by the applied multi-bit digital signal, a signal from the high frequency circuit 1 obtained by frequency division by the programmable counter 18, and a reference signal from the reference oscillator 19. a phase comparator 20 that compares the phase with the phase comparator 20, and a filter 21 that filters the signal obtained by the comparison with the phase comparator 20 and generates a search signal.
It becomes more. In the controller 5, when the search switch 7 is turned on, the oscillator 16 oscillates to start a search, and when an intermediate frequency signal is generated in the intermediate frequency amplifier circuit 2, a stop signal generated by the auto-stop detection circuit 8 is applied to the pause terminal P, and the oscillator 16 The search is temporarily stopped by temporarily stopping the oscillation of the oscillator, and the search is resumed after a few seconds. However, when the hold switch 9 is turned on, the oscillator 16 is reset and the search can be stopped continuously. A transistor 10 is connected in parallel to the hold switch 9, and its base is connected to the intermediate frequency amplification circuit 2 via a differentiation circuit 11 and a Schmitt circuit 12.

Next, the operation of the present invention will be explained. When search switch 7 is pressed and turned on temporarily, oscillator 1
6 is set and starts oscillation, a pulse signal is added to the register 17, the register 17 is counted,
Generates a multi-bit digital signal that changes every moment,
The frequency division ratio of the programmable counter 18 is changed every moment. Initially, since there is no signal applied to the programmable counter 18 of the PLL circuit 6 from the high frequency circuit 1 or it is not tuned, the programmable counter 18 applied to the phase comparator 20
Since the phases of the signals from the reference oscillator 19 and the reference oscillator 19 are different, a signal corresponding to the phase difference is generated, and this signal is filtered by the filter 21 and becomes a DC search signal, which is added to the semiconductor variable capacitance element for tuning of the high frequency circuit 1, and In order to change the capacitance value of the semiconductor variable capacitance element, the tuning frequency of the antenna section of the high frequency circuit 1 and the frequency of the local oscillation signal are changed, and are tuned to one broadcast signal being received by the antenna 13 in a certain state. The broadcast signal is thus amplified and further frequency converted to produce an intermediate frequency signal. The intermediate frequency signal is amplified by an intermediate frequency circuit 2 and then converted into an audio signal by a detection circuit 3. The converted audio signal is amplified by the audio amplification circuit 4 and then sent to the speaker 14.
drive and emit sound. By the way, when an intermediate frequency signal is generated in the intermediate frequency amplifier circuit 2, a stop signal is detected by the auto-stop detection circuit 8, and the oscillation of the oscillator 16 of the controller 5 is interrupted to temporarily stop the search. Furthermore, at this time, if the intermediate frequency signal is above a predetermined level, the Schmitt circuit 12 is operated to generate a pulse signal. The pulse signal is applied to the base of the transistor 10 via the differentiating circuit 11, and turns on the transistor 10 for a period determined by the differentiating circuit 11. Then, the state is the same as when the hold switch 9 is turned on, so the oscillator 16 of the controller 5 stops oscillating and continues to stop searching, and continues to receive the searched broadcast signal. Next, turn on search switch 7,
At this time, since the transistor 10 in the differentiating circuit 11 is turned off, the oscillator 16 oscillates and starts searching again.

When the search progresses and the high frequency circuit 1 is tuned to a broadcast signal again, the signal is amplified, frequency converted, detected, etc. as described above, and the speaker 14 is driven to emit sound.
At this time as well, a stop signal is detected by the auto-stop detection circuit 8 from the intermediate frequency amplifier circuit 2, and the oscillation of the oscillator 16 of the controller 5 is interrupted to temporarily stop the search. However, when the electric field strength of the tuned broadcast signal is small and the intermediate frequency signal is below a predetermined level, the Schmitt circuit 12 is not operated and does not generate a pulse signal, so that the transistor 10 is not turned on for several seconds. , the oscillator of the controller 5 oscillates and restarts the search.
If you want to listen to the searched broadcast signal even if it has a weak electric field strength and a lot of noise, turn on the hold switch 9 and the oscillator 16 of the controller 5 will not oscillate and the search will stop continuously. You can listen to the broadcast.

As mentioned above, in the synthesizer tuner of the present invention, when a broadcast signal with a strong electric field is searched, the controller's search stops and the broadcast signal can be listened to, but when a broadcast signal with a medium-weak electric field is searched, the hold switch is activated. Since the search is automatically resumed unless the switch is turned on, it is possible to easily search only for broadcast signals with a strong electric field and desired broadcast signals with a medium-weak electric field.

[Brief explanation of the drawing]

The figure is a circuit diagram of the synthesizer tuner of the present invention. 1...High frequency circuit, 2...Intermediate frequency amplification circuit,
5... Controller, 6... PLL circuit, 7... Search switch, 9... Hold switch, 10...
...Transistor, 11... Differential circuit, 12... Schmitt circuit.

Claims (1)

[Scope of utility model registration request] A device that controls a PLL circuit using a digital signal taken out from a controller, generates a search signal, performs a search, and when one broadcast signal is searched, temporarily stops the search action of the controller and restarts the search after a few seconds. In this method, a transistor is connected in parallel to a hold switch that continuously stops the search action of the controller, and the transistor is turned on by a signal of a predetermined level or higher taken out from an intermediate frequency amplification circuit, so that the search action of the controller is continuously stopped. A synthesizer tuner characterized by the ability to stop.