JPS6233774B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is characterized in that when a manual tuning switch is operated, it is repeatedly turned on, and each time it is turned on, the receiving frequency changes by a predetermined frequency, and This is a PLL synthesizer type digital tuning radio receiver that is configured so that muting is applied to the low frequency circuit for a certain period of time each time the tuning switch is turned on. The purpose is to provide a radio receiver.

Conventionally, a switch for manual tuning such as a rotary switch, in which the contact is closed repeatedly in short periods as the knob is rotated, is operated, and the reception frequency is set in advance each time the contact is closed. A PLL synthesizer type digital tuning radio receiver is known, which is configured so that the low frequency circuit changes by a predetermined frequency and muting is applied to the low frequency circuit for a fixed period of time each time the switch is turned on.

Figure 1 is a block diagram of this type of radio receiver. In the figure, 1 is an FM front end, 2 is a circuit block equipped with an FM intermediate frequency amplification circuit and a detection circuit, and 3 is a circuit block in the FM front end 1. 4 is a prescaler circuit that divides the output frequency of the local oscillation circuit; 4 is an AM high-frequency circuit equipped with an AM high-frequency amplification circuit, a local oscillation circuit, and a frequency conversion circuit; 5
6 is a circuit block equipped with an AM intermediate frequency circuit and a detection circuit, 6 is a low frequency stage muting circuit, 7 is a low frequency amplification circuit, 8 is a speaker, and 9 is a manual tuning switch 10 that is connected to a terminal 15 or The oscillation frequency of the local oscillation circuit in the FM front end 1 or
A PLL synthesizer-type digital tuning integrated circuit that increases or decreases the oscillation frequency of the local oscillation circuit in the AM high-frequency circuit 4 by a preset frequency, and changes the receiving frequency by a preset frequency. It is. The integrated circuit 9 is also configured to output a predetermined muting signal from the terminal 14 for a predetermined period of time each time the manual tuning switch 10 is turned on to the terminal 15 or 16.

In addition, as a radio receiver, a band switching circuit,
Although other circuits such as a reception frequency display circuit are included, they are not shown here for the sake of simplicity.

FIG. 2 specifically shows an example of the muting circuit 6. In the figure, 17 is a base resistor, and 18 is a muting transistor.

In the conventional radio receiver shown in FIGS. 1 and 2, each time the manual tuning switch 10, which is composed of a rotary switch or the like, is operated to be turned on the terminal 15 or terminal 16 side for a short time. The reception frequency increases or decreases stepwise by a preset constant frequency. and,
In synchronization with this, a positive muting output, for example, appears from the muting terminal 14 of the integrated circuit 9 for a predetermined period of time. Therefore, this output is applied to the base of the transistor 18 through the resistor 17, resulting in a low impedance between the collector and emitter of the transistor 18, and the audio signal input to the low frequency amplifier circuit 7 is greatly attenuated.

The above operation can be explained using a timing chart as follows. Now, a manual tuning switch 10 composed of a rotary switch or the like is connected to a terminal 15 or a terminal 16 of the integrated circuit 9.
Assume that the operation is performed so that the injection is repeated as shown in FIG. 3 T _A. This input time T _A
is typically several tens of milliseconds. Then, a muting signal is output from the muting terminal 14 of the integrated circuit 9 as shown in FIG. 3 M _A.
Here, M _A1 is the output time of the muting signal,
This is a fixed time determined by the integrated circuit 9 and its peripheral circuit constants. This output time M _A1 is usually 200~
This is done in about 500 milliseconds. However, the receiving frequency switching operation itself in a PLL synthesizer type digital tuning circuit is normally completed in about 20 milliseconds. Next, this muting output turns on the transistor 18, and as shown in _FIG.
The audio signal is muted for the time S _A1 as shown in FIG.

By the way, if the manual tuning switch 10 is turned on for a short period of time at a sufficiently long cycle of T _A1 , the time during which the sound is output is _A1 per cycle, as shown in Fig. 3 S _A. Therefore, the person operating the manual tuning switch 10 can identify the audio signal heard from the receiver during _A1 and determine whether there is a station on the receiving frequency at that time.

Next, switch 1 for manual tuning.
A case where zero is repeatedly turned on at a period considerably shorter than T _A1 as shown in FIG. 4 T _A ' by rotating a rotary switch will be explained. In this case, if T _A1 ≦ M _A1 , the muting pulse remains at a high level as shown in Fig. 4 M _A ', and the audio signal remains off (Fig. 4 S _A
'). Therefore, if the manual tuning switch 10 is operated to turn on at a certain rate or faster (T _A1 ≦ M _A1 ), the audio signal will remain off, and even if there is a station that can be received,
It cannot be identified by the operator.

This means that in order to search for a station using manual tuning, it is necessary to press the switch at a speed below a certain level.
The problem arises that it is extremely inconvenient that 0 must be manipulated.

Alternatively, to avoid this drawback, it is possible to remove the muting circuit itself.
In this case, another drawback arises in that abnormal noise is always generated during various key operations such as manual tuning and power-on.

The present invention eliminates the above drawbacks with a simple circuit configuration.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The radio receiver of the present invention will be described below with reference to the drawings of one embodiment. FIG. 5 is an electrical wiring diagram of the main parts of an embodiment of the radio receiver of the present invention. The same thing as in the figure is shown. Further, 19 to 21 are resistors, and 22 and 23 are diodes.

In FIG. 5, when the manual tuning switch 10 is operated so that the terminal 15 or the terminal 16 is turned on for a short time, the receiving frequency changes by a preset constant frequency each time it is turned on. At the same time, a muting output is output from the muting terminal 14. By the way, in this case, since the diode 22 or 23 is turned on while the switch 10 is connected to the terminal 15 or 16, the muting output from the terminal 14 of the integrated circuit 9 is connected to the diode 22, 23 and the resistor 19, 2.
0 and 21, the muting output is not applied to the muting circuit 6, and the transistor 18 is not turned on but remains off. That is, while the manual tuning switch 10 is connected to the terminal 15 or 16, muting is forcibly released.

This is illustrated with a timing chart:
The result is as shown in FIG. Now, when the tuning switch 10 is applied to the terminal 15 or 16 with a sufficiently long period T _B1 , the muting pulse M _B is output with a pulse width of M _B1 (200 to 500 milliseconds as described above). However, according to this embodiment, the switch 10 for manual tuning is connected to the terminal 15.
or T _B2 (several tens of milliseconds) while being inserted into 16
Since mutating is canceled, the actual muting time becomes M _B1 - T _B2 = S _B1 . Therefore, as is clear from FIG. 6, only T _B1 - M _B1 + T _B2 = _B1 is output per one step of the audio signal.

Next, the period T B1 at which the manual tuning switch 10 is turned on to the terminal 15 or 16 by a quick rotation operation of the rotary switch is T _{B1 ′} (however, T _B1 ′≦ The case where the length is shortened to M _B1 ) will be explained. In this case, the muting pulse remains at a high level as shown in FIG. 7 M _B ', but according to the above embodiment, the manual tuning switch 1
Since the muting of T _B2 is forcibly canceled while 0 is applied to the terminal 15 or 16, the actual muting time is T _B1 '-T _B2 = S _B1 '. Therefore, as is clear from FIG. 7, the number of audio signals T _B2 = _B1 ' is output per one step. Therefore, even if the speed at which the manual tuning switch 10 is operated is considerably increased, the
Sound is always output for a time period T _B2 for each step, and if a station is received during this period, it can be identified.

In other words, as mentioned above, the pulse width M _B1 of the muting pulse M _B is set to 200 to 500 milliseconds in consideration of the stabilization time of the AGC circuit, etc., but the PLL synthesizer type digital Since the switching operation of the receiving frequency in the tuning circuit is completed within approximately 20 milliseconds after the manual tuning switch 10 is turned on, T _B2 (several 10 If a sound is output within a millisecond), reception of the station can be identified. Therefore, the closing period T _B1 ' of the switch 10 is T _B2 at the shortest.
It is possible to shorten it to .

As described above, according to the present invention, manual tuning can be made fast and easy while maintaining the muting function with a simple circuit configuration.
This is extremely advantageous in practice.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a conventional radio receiver, Fig. 2 is a specific electrical connection diagram of the main parts, Figs. 3 and 4 are operational explanatory diagrams of the main parts, and Fig. 5
The figure is an electrical connection diagram of the main parts of an embodiment of the radio receiver of the present invention, and FIGS. 6 and 7 are operation explanatory diagrams of the main parts. 1...FM front end, 2...Circuit block equipped with FM intermediate frequency reception circuit and detection circuit, 3
...Prescaler circuit, 4...AM high frequency circuit,
5... Circuit block equipped with an AM intermediate frequency circuit and a detection circuit, 6... Muting circuit, 7... Low frequency circuit, 9... Integrated circuit for digital tuning, 18... Muting transistor,
19-21...resistor, 22,23...diode.

Claims (1)

[Claims] 1. Contacts may close due to operations such as rotating a knob.
Each time a manual tuning switch such as a rotary switch is repeatedly turned on for a short period of time longer than the time required to change the frequency of a PLL synthesizer type tuner, the receiving frequency is changed to a preset constant frequency. Tuning is performed using a PLL synthesizer-type digital tuning integrated circuit configured to operate in such a way that the muting output changes and at the same time synchronize with this and output the required muting output to the muting circuit for a preset period of time. The muting output is applied to the muting circuit for a period of time after the manual tuning switch is turned on until a certain period of time has elapsed after the digital tuning integrated circuit changes to a new frequency. A radio receiver that is equipped with a circuit that forcibly cancels muting to prevent it from being muted.