JPH06125269A - Variable frequency type high frequency oscillator circuit - Google Patents

Abstract

PURPOSE:To provide a high frequency oscillator which outputs an arbitrary high frequency by extracting a desired wave by a band-pass filter with variable center frequency to take out the wave out of the output of a voltage controlled high frequency oscillator circuit and the differential frequency output of an overtone oscillator circuit. CONSTITUTION:This circuit is provided with an overtone crystal oscillator circuit 2, a first frequency division circuit 4 which performs the 1/m-frequency division of a desired frequency from the oscillator circuit 2, a VCO 1 which generates a high frequency signal, a second frequency division circuit 5 which performs the 1/n-frequency division of the output of the VCO 1 by a control signal, a phase comparator 6 which feeds back the voltage of phase difference to the VCO 1 by performing the phase comparison of the output signals of the first and second frequency division circuits, a mixer circuit 8 which outputs a differential frequency by mixing the output signal of the overtone crystal oscillator circuit 2 with that of the VCO 1, a decoder 7 which supplies the control signal to vary the frequency ratio of the second frequency division circuit to change the frequency of the output signal of the mixer circuit 8, and a voltage controlled band-pass filter 9 which selects a desired signal from the output signal of the mixer circuit 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable frequency type high frequency oscillating circuit, and more particularly to a high frequency oscillating circuit which mixes the outputs of one overtone oscillating circuit and a synthesizer type high frequency oscillating circuit to select and output only a desired frequency. Regarding the circuit.

[0002]

2. Description of the Related Art Conventionally, this type of high-frequency oscillator circuit outputs a high-frequency signal from a synthesizer-type high-frequency oscillator circuit and mixes it with the frequency of an overtone oscillator by a mixer,
A desired high frequency signal is selected by the filter of variable center frequency. Therefore, a circuit or a modularized high-frequency oscillator and an overtone oscillator have to be replaced each time the frequency is different, and several types of high-frequency oscillators have been prepared for changing the frequency band.

[0003]

As described above, in the conventional variable-frequency high-frequency oscillator circuit, since a synthesizer-type high-frequency wave oscillator must be prepared for each variable frequency band, the number of steps for changing the frequency and There is a drawback that the configuration is expensive.

The object of the present invention is to input the output signals of both the high frequency band voltage controlled oscillator circuit and the relatively low frequency band overtone crystal oscillator circuit to a mixer circuit, and to obtain a large number of difference frequencies appearing at the outputs. Among them, a desired high frequency signal is selected by a band filter whose center frequency can be changed by voltage control, thereby realizing a variable frequency high frequency oscillator circuit.

[0005]

A variable frequency high-frequency oscillator circuit according to the present invention is an overtone crystal oscillator circuit, a first bandpass filter for selecting a desired frequency from the overtone crystal oscillator circuit, and a first bandpass filter thereof. The first frequency divider circuit for dividing the output of the band-pass filter of 1 / m (m is an integer), the voltage controlled oscillator circuit for generating a high frequency signal, and the output of this voltage controlled oscillator circuit for the control signal from the control terminal. By 1 / n
(N is an integer) A phase comparator for phase-comparing a second frequency-dividing circuit for frequency-dividing and the output signals of the first and second frequency-dividing circuits and feeding back a voltage having a phase difference to the voltage-controlled oscillator. And a mixer circuit that mixes the output signal of the overtone crystal oscillation circuit and the output signal of the voltage controlled oscillation circuit to output a difference frequency, and a program in advance when changing the frequency of the output signal of the mixer circuit. A decoder for supplying a first control signal for changing the value of the frequency division ratio n to the set control terminal of the second frequency divider circuit;
A control circuit for branching the output signal of the decoder and outputting a second control signal for controlling a voltage controlled bandpass filter for selecting a desired signal from the output signal of the mixer circuit.

[0006]

The present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of an embodiment of the present invention. In FIG. 1, an oscillation signal in a high frequency band is obtained from a voltage control type oscillation circuit (called VCO) 1. The voltage for controlling the VCO 1 divides the 1 / m frequency-divided output and the oscillation frequency of its own VCO 1 with the desired 1 wave obtained through the bandpass filter 3 among the output frequencies of the overtone oscillation circuit 2 as the reference frequency. The phase comparison circuit 6 compares the output of the / n frequency divider circuit 5 in phase. The control voltage corresponding to this phase difference is extracted by the low-pass filter 1A provided in the input part of the VCO 1. The oscillation frequency of the VCO 1 is f _1A , as shown in FIG. 2A, when the frequency division ratio n of the 1 / n frequency dividing circuit 5 is determined by the high frequency frequency setting decoder 7.
It can be output as an arbitrary frequency within a certain band such as f _1B , f _1C , .... On the other hand, the overtone crystal oscillating circuit is a relatively low frequency oscillating circuit, and its oscillation state outputs an overtone oscillating signal of f ₂ , 2f ₂ , 3f ₂ , ... As shown in FIG. The frequencies of the two oscillator circuits are input to the mixer circuit 8, and the output thereof includes a plurality of difference frequencies as shown in FIG. 2 (c).
For example, this frequency array f _1C ± f ₂ , f _1C + 2f ₂ , f
_1C ± 3f ₂ , ... Is a source for generating a transmission / reception radio frequency, and in this case, the radio frequency channel interval is f ₂ . If the frequency band of f ₂ is a high frequency band (for example, about 1/3 of the high frequency band), the above f _1C ± f ₂ , f _1C
± 2f ₂ is f _1C ± f _1C / 3, f _1C ± 2f _1C / 3, respectively
That is, 4/3 times, 5/3 times or 2 / of the high frequency oscillator
It becomes 3 times and 1/3 times, and the band of the oscillation frequency can be broadened equivalently. In this way, various frequency bands and channel intervals can be easily realized by combining the frequencies of the oscillation circuits.

Next, the output of the mixer circuit 8 is input to the voltage control type bandpass filter 9, one wave determined by the center frequency of the voltage control type bandpass filter 9 is selected, and a constant output level is set by the automatic gain amplifier 10. It is output after being controlled by. On the other hand, the voltage-controlled bandpass filter 9 is controlled by the control circuit 11 to have a band of a predetermined center frequency. Further, the control circuit 11 converts the decoded output having the individual code for each RF frequency output from the RF frequency setting decoder 7 into a voltage by the D / A conversion circuit 11A, and passes through the DC amplifier 11B to the low pass filter 11C. After the noise and the like are removed by, the voltage control type bandpass filter 9 is controlled via the DC amplifier 11D.

As described above, the oscillation frequency corresponding to each high frequency is output.

[0009]

As described above, according to the present invention, it is possible to easily change the frequency of the high-frequency oscillation circuit with a simple circuit configuration without replacing the local oscillator module as in the conventional example or adjusting the circuit each time. There is an effect that can be done.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the operation of the present embodiment.
(A) is a chart of the output frequency of the VCO, FIG. (B) is an output frequency sequence of the overtone crystal oscillation circuit, and (c) is a mixer circuit output frequency sequence.

[Explanation of symbols]

 1 Voltage Controlled Oscillation Circuit (VCO) 2 Overtone Crystal Oscillation Circuit 3 Bandpass Filter 4,5 Frequency Division Circuit 6 Phase Comparator 7 Decoder 8 Mixer Circuit 9 Voltage Controlled Bandpass Filter 10 Automatic Gain Control Amplifier 11 Control Circuit 11A D / A conversion circuit 11B, 11D DC amplifier 11C Low-pass filter

Claims (3)

[Claims] 1. An overtone crystal oscillator circuit, a first bandpass filter for selecting a desired frequency from the overtone crystal oscillator circuit, and 1 / m (m is an integer) of the output of the first bandpass filter. The first frequency divider circuit for frequency division, the voltage controlled oscillator circuit for generating a high frequency signal, and the output of the voltage controlled oscillator circuit is 1 / n according to the control signal from the control terminal.
(N is an integer) A phase comparator for phase-comparing a second frequency-dividing circuit for frequency-dividing and the output signals of the first and second frequency-dividing circuits and feeding back a voltage having a phase difference to the voltage-controlled oscillator. And a mixer circuit that mixes the output signal of the overtone crystal oscillation circuit and the output signal of the voltage controlled oscillation circuit to output a difference frequency, and a program in advance when changing the frequency of the output signal of the mixer circuit. A decoder for supplying a first control signal for changing the value of the frequency division ratio n to the set control terminal of the second frequency divider circuit;
A control circuit for branching the output signal of the decoder to output a second control signal for controlling a voltage-controlled bandpass filter for selecting a desired signal from the output signal of the mixer circuit. Modified high-frequency oscillator circuit. 2. The frequency of the output signal of the voltage controlled oscillator circuit is set to a certain frequency fc by the control of the decoder and the second frequency divider circuit, and the frequency of the output signal of the overtone crystal oscillator circuit is M · If f2 (M is an integer), the frequency of the output signal of the mixer circuit is fc ± M
The variable frequency high-frequency oscillator circuit according to claim 1, which outputs ± M output signals of f2. 3. The frequency f of the output signal of the mixer circuit is controlled by the voltage control type bandpass filter by the control circuit.
The variable frequency type high frequency oscillator circuit according to claim 1 or 2, wherein the center frequency is controlled to match any one of c ± M · f2.