JP2848156B2 - Variable frequency high frequency oscillation circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable-frequency high-frequency oscillator, and more particularly to a high-frequency oscillator that mixes the outputs of one overtone oscillator and a high-frequency oscillator of a synthesizer type and selects and outputs only a desired frequency. 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 the high-frequency signal with a frequency of an overtone oscillator by a mixer.
A desired high-frequency signal is selected by a center frequency variable filter. Therefore, every time the frequency is different, a circuit or a modularized high-frequency oscillator must be replaced with an overtone oscillator, and several types of high-frequency oscillators corresponding to frequency band changes have been prepared.

[0003]

As described above, in the conventional variable-frequency high-frequency oscillator circuit, a high-frequency oscillator of a synthesizer system must be prepared for each variable frequency band. There is a disadvantage that the configuration is expensive.

An object of the present invention is to input both output signals of a high frequency band voltage controlled oscillator circuit and a relatively low frequency band overtone crystal oscillator circuit to a mixer circuit, and to output a large number of difference frequencies appearing at the output of the mixer circuit. By selecting a desired high-frequency signal by a band-pass filter capable of changing the center frequency by voltage control, a variable-frequency high-frequency oscillation circuit is realized.

[0005]

According to the present invention, there is provided a variable-frequency high-frequency oscillation circuit comprising: an overtone crystal oscillation circuit; a first bandpass filter for selecting a desired frequency from the overtone crystal oscillation circuit; A first frequency divider for dividing the output of the bandpass filter by 1 / m (m is an integer), a voltage-controlled oscillator for generating a high-frequency signal, and a control signal from a control terminal By 1 / n
(N is an integer) A phase comparator that compares the phases of a second frequency divider circuit for frequency division and output signals of the first and second frequency divider circuits and feeds back a voltage having a phase difference to the voltage controlled oscillator. 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 that is used in advance to change 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 dividing ratio n to the set control terminal of the second frequency dividing circuit;
A control circuit that outputs a second control signal that controls a voltage-controlled bandpass filter that branches the output signal of the decoder and selects a desired signal from the output signal of the mixer circuit.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of one embodiment of the present invention. In FIG. 1, an oscillation signal in a high frequency band is obtained from a voltage controlled oscillation circuit (referred to as a VCO) 1. The voltage for controlling the VCO 1 is obtained by dividing a 1 / m frequency-divided output and the oscillation frequency of the VCO 1 by using a desired one of the output frequencies of the overtone oscillation circuit 2 obtained through the bandpass filter 3 as a reference frequency. The phase of the output of the / n frequency dividing circuit 5 is compared by the phase comparing circuit 6. The control voltage corresponding to this phase difference is extracted by a low-pass filter 1A provided at the input of the VCO 1. As shown in FIG. 2A, the oscillation frequency of the VCO 1 is determined as f _1A , as shown in FIG.
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 overtone oscillating signals f ₂ , 2f ₂ , 3f ₂ ,... As shown in FIG. The frequencies of the two oscillation circuits are respectively input to the mixer circuit 8, and the output includes a plurality of difference frequencies as shown in FIG.
For example, this frequency array f _1C ± f ₂ , f _1C + 2f ₂ , f
_1C ± 3f ₂ ,... Are for generating transmission / reception radio frequencies. In this case, the channel interval of the radio frequencies is f ₂ . Further, the frequency band of f ₂ is a high frequency band (for example, about 1/3 of the high-frequency band) then the aforementioned f _1C ± f _2, f _1C
Each ± 2f ₂ is _{f 1C ± f 1C / 3,} f 1C ± 2f 1C / 3
In other words, 4/3 times, 5/3 times or 2 /
It becomes 3 times and 1/3 times, and the band of the oscillation frequency can be expanded equivalently. Thus, 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 a voltage-controlled bandpass filter 9, one wave determined by the center frequency of the voltage-controlled bandpass filter 9 is selected, and a constant output level is set by an automatic gain amplifier 10. Is output after being controlled. On the other hand, the voltage-controlled bandpass filter 9 is controlled by the control circuit 11 to 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 or the like is removed by the above, the voltage-controlled 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, the frequency of the high-frequency oscillation circuit can be easily changed with a simple circuit configuration without replacing the local oscillator module and adjusting the circuit each time as in the conventional example. There is an effect that can be done.

[Brief description of the drawings]

FIG. 1 is a block diagram of one 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, (b) is an output frequency train of the overtone crystal oscillation circuit, and (c) is a mixer circuit output frequency train.

[Explanation of symbols]

 1 Voltage Controlled Oscillator (VCO) 2 Overtone Crystal Oscillator 3 Bandpass Filter 4, 5 Divider 6 Phase Comparator 7 Decoder 8 Mixer 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)

(57) [Claims] 1. An overtone crystal oscillation circuit, a first bandpass filter for selecting a desired frequency from the overtone crystal oscillation circuit, and an output of the first bandpass filter divided by 1 / m (m is an integer) A first frequency-dividing circuit, a voltage-controlled oscillating circuit for generating a high-frequency signal, and an output of the voltage-controlled oscillating circuit which is 1 / n by a control signal from a control terminal.
(N is an integer) A phase comparator that compares the phases of a second frequency divider circuit for frequency division and output signals of the first and second frequency divider circuits and feeds back a voltage having a phase difference to the voltage controlled oscillator. 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 that is used in advance to change 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 dividing ratio n to the set control terminal of the second frequency dividing circuit;
And a control circuit for outputting a second control signal for controlling a voltage-controlled bandpass filter for selecting a desired signal from an output signal of the mixer circuit by branching an output signal of the decoder. Modified high-frequency oscillation circuit. 2. The frequency of the output signal of the voltage controlled oscillator is set to a certain frequency fc by the control of the decoder and the second frequency divider, and the frequency of the output signal of the overtone crystal oscillator is M · If f2 (M is an integer), the frequency of the output signal of the mixer circuit is fc ± M
2. The variable frequency high frequency oscillation circuit according to claim 1, wherein ± M output signals of f2 are output. 3. The voltage controlled bandpass filter controls the frequency f of an output signal of the mixer circuit under the control of the control circuit.
3. The frequency-variable high-frequency oscillation circuit according to claim 1, wherein the central frequency is controlled to match any one of c ± M · f2.