JPS6012346Y2 - tuned circuit - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a tuning circuit for a receiver, a transmitter, or a transceiver.

Generally, when a receiver has multiple bands, in order to perform groin tuning, conventional techniques include manually fine-tuning the variable capacitor in the tuning circuit, or switching the voltage applied to the variable capacitance diode in the tuning circuit using a variable resistor or switch. In some cases, a variable resistor like this is linked with a variable capacitor of a local oscillator, eliminating the need for manual tuning.

However, in the conventional type, the tuning operation is troublesome because it is manual, and in the case where manual tuning is omitted, a bandpass filter is required, and in this case, there are problems with the selectivity characteristics.

In view of the above-mentioned drawbacks, this invention selects a frequency band with a band selection switch, and uses the frequency output of the local oscillator when setting the desired frequency within the selected band by varying the local oscillator. The object of the present invention is to obtain a tuning circuit in which an interstage tuning circuit automatically tunes to a desired frequency for transmission or reception.

The configuration of the present invention includes a variable local oscillator to tune a receiver or transmitter to a desired frequency, a changeover switch that can set a reference voltage in conjunction with a band changeover switch that selects a frequency band, and a changeover switch that can set a reference voltage in conjunction with a band changeover switch that selects a frequency band. It consists of a frequency-voltage conversion means for converting a frequency output into a DC voltage, and a voltage synthesis circuit for synthesizing the reference voltage and the DC voltage,
The voltage synthesized by the voltage synthesis circuit is applied to a variable capacitance diode of a tuning circuit, and the interstage tuning circuit is configured to automatically tune to a desired frequency in response to a change in the frequency output of the local oscillator. ing.

Embodiments of this invention will be described below based on the drawings.

In the figure, 1 is a variable frequency oscillator (hereinafter abbreviated as VFO), 2 is a fixed frequency oscillator, 3 is a switch for switching the local oscillation frequency of one of them, 4 is a waveform shaping circuit using a Schmitt trigger circuit, etc., and 5 is a frequency dividing circuit. circuit, 6 is a monostable multi-bi break, 7 is a low-pass filter (hereinafter L
(abbreviated as PF), 8 is a changeover switch interlocked with a band changeover switch, which switches each of the resistors R1 to Rn for obtaining a reference level setting voltage to obtain variously set voltages.

9 is a voltage synthesis circuit that synthesizes the DC voltage of LPF 7 and the voltage passed through changeover switch 8; 10 is a variable capacitance diode D
101~10n, D2~D
The same applies to n.

The variable frequency oscillator 1 and the fixed frequency oscillator 2 are local oscillators that are variable in order to tune a receiver or transmitter to a desired frequency, and the frequency-voltage conversion means includes a waveform shaping circuit 4 such as a Schmitt trigger circuit, It is composed of a frequency dividing circuit 5, a monostable multivibrator 6, and a low pass filter 7.

The operation of the above configuration will be explained next.

The frequency output of the VFO 1 or the fixed frequency oscillator 2 is selected by the changeover switch 3, a target frequency is taken out, the waveform is shaped by the waveform shaping circuit 4, and it is applied to the frequency dividing circuit 5.

When the frequency dividing circuit 5 divides the frequency by 1/N and adds it to the monostable multivibrator 6 to obtain output pulses with constant amplitude and width, the number of pulses depends on the oscillation frequency of the VFOl or the fixed frequency oscillator 2. This will change.

When it passes through LPF 7, the frequency -
A converted DC voltage is obtained.

By combining this DC voltage and the set voltage obtained by the changeover switch 8 and applying this output to the variable capacitance diode D1 of the interstage tuning circuit 10, the local oscillation frequency and band changeover switch can be adjusted to the desired frequency. At the same time, the interstage tuning circuit will also automatically tune to the desired frequency.

Other interstage tuning circuits 10□-10. The same applies to the case of .

Note that the voltage synthesis circuit 9 is not necessary for monoband or two or more band tuning circuits in which coils are switched for each band.

As described above, according to this invention, the interstage tuning circuit is always automatically tuned to the desired frequency, making operation easier.
The tuning knob can also be omitted, and the selectivity and spurious characteristics can be improved compared to those using band-pass filters, and the frequency- The voltage conversion means makes it possible to always make the best adjustments, making it easy to eliminate the need for adjustments in transmitters and receivers, and eliminating the need for direct manual adjustment of high-frequency circuits as in the past. It has the advantage that it does not include any mechanical parts that operate in conjunction with the variable capacitor of the local oscillator.

[Brief explanation of the drawing]

The figure is a block diagram showing an embodiment of this invention. In the figure, 1...VFo, 2...Fixed frequency oscillator, 4... Waveform shaping circuit 5...
... Frequency divider circuit, 6... Monostable multivibrator, 7. Song LPF, 9... Voltage synthesis circuit,
10~10n/music/interstage tuning circuit.

Claims (1)

[Scope of utility model registration request] A local oscillator that can be varied to tune the receiver or transmitter to a desired frequency, a changeover switch that can set a reference voltage in conjunction with a band changeover switch that selects the frequency, and a conversion switch that converts the frequency output of the local oscillator into a DC voltage. a frequency-to-voltage converter that synthesizes the reference voltage and the DC voltage; the voltage synthesized by the voltage synthesizer circuit is applied to a variable capacitance diode of the tuning circuit; In response to changes in the frequency output of
A tuning circuit characterized in that a crotch tuning circuit is automatically tuned to a desired frequency.