JP4657797B2 - High frequency oscillator and high frequency synthesizer - Google Patents

Description

  The present invention relates to a high frequency oscillator and a high frequency synthesizer.

As a conventional high-frequency oscillator, an amplifying unit having an oscillation active element, an inductor and a capacitor, a load resistor connected to the output side of the amplifying unit, and an input side of the amplifying unit connected to the inductor and external control Some include a resonance circuit composed of a variable capacitance element whose capacitance value changes according to voltage, and an expansion capacitance element connected to the resonance circuit via a switching element.
As the operation, noise in the circuit of the high frequency oscillator is amplified by the active element, and a part of the amplified power is activated by a reactance circuit such as an inductor, a capacitor, and a resonance circuit connected to each terminal of the active element. Returning to the element, the power is further amplified by the active element, so that the oscillation operation is performed and the load resistor oscillates and outputs. This oscillation frequency is determined by the resonance frequency of the resonance circuit. When controlling the oscillation frequency, by changing the external control voltage applied to the variable capacitance element, the junction capacitance of the variable capacitance element is changed, and the resonance frequency of the resonance circuit is changed. Furthermore, the oscillation frequency band can be switched by controlling the switching element from the outside and turning it on and off to connect or disconnect the expansion capacitive element to the resonance circuit (see, for example, Patent Document 1).

As a conventional high-frequency synthesizer, a reference oscillator that outputs a 1 / N frequency having a high stability and a desired oscillation frequency, a phase comparator that compares phases of an output waveform of the reference oscillator and a feedback input waveform, and a phase comparison A low-pass filter that removes unnecessary high-frequency components from the control voltage from the voltage generator, a voltage-controlled oscillator that oscillates and outputs a frequency according to the control voltage, a coupler or distributor that distributes the output of the voltage-controlled oscillator, and distribution A bandpass filter for harmonics that passes harmonics out of the output of the controlled voltage controlled oscillator, a bandpass filter for fundamental waves that passes fundamentals out of the output of the distributed voltage controlled oscillator, and for fundamental waves And a frequency divider that divides the oscillation frequency of the voltage controlled oscillator that has passed through the band-pass filter by N and feeds back to the phase comparator.
The operation is based on the phase difference output from the phase comparator so that the phase difference between the oscillation frequency by the reference oscillator and the frequency oscillated by the voltage controlled oscillator and divided by N by the frequency divider becomes zero. The oscillation frequency of the voltage controlled oscillator is controlled by the control voltage. By applying such feedback, the phase of the output frequency of the voltage controlled oscillator is synchronized with the phase of the output frequency of the reference oscillator, and an oscillation output according to the stability of the reference oscillator is obtained. Moreover, the harmonic of the output frequency of a voltage controlled oscillator can be obtained from the bandpass filter for harmonics (for example, refer patent document 2).

JP-A-7-183726 JP-A-10-126262

Since the conventional high-frequency oscillator is configured as described above, in order to widen the oscillation frequency, it is necessary to provide a capacity element for expansion via a switching element in the resonance circuit, which increases the circuit configuration. In addition, there is a problem that the switching element needs to be controlled from the outside.
Conventional high-frequency synthesizers must distribute the output of the voltage-controlled oscillator with a coupler or distributor to separate the high-frequency with two band-pass filters, and the circuit configuration increases in size. There was a problem.

  The present invention has been made to solve the above-described problems. By using a coupler composed of a left-handed device, the oscillation frequency can be widened and the frequency can be increased while maintaining a small size. An object is to obtain a high-frequency oscillator and a high-frequency synthesizer.

  In the high-frequency oscillator according to the present invention, when the first port is connected to the first terminal of the transistor and the first port is used as the input port, the second and fourth frequency bands are applied to the first frequency band. The left port is an isolation port, the third port is a pass port, and for the second frequency band, the second port is a pass port and the third and fourth ports are isolation ports. A coupler configured by the device, a first resonance circuit connected to the third port of the coupler and resonating at a first frequency included in the first frequency band, and connected to the second port of the coupler; A second resonance circuit that resonates at a second frequency included in the second frequency band; a reactance circuit connected to each of the second and third terminals of the transistor; At least one of the reactance circuits connected to at least one of them, and at least one of the reactance circuits is a tuning circuit capable of changing a resonance frequency in the first and second frequency bands; It is a thing.

  According to the present invention, the first resonance circuit, the third and first ports of the coupler, the transistor and the tuning circuit oscillate in the first frequency band, and the second resonance circuit, the second and first of the coupler, A high-frequency oscillator that can oscillate in the second frequency band through a port, a transistor, and a tuning circuit, and realizes a wide oscillation frequency while maintaining a small size by using a coupler configured by a left-handed device There is an effect that can be obtained.

Embodiment 1 FIG.
FIG. 1 is a circuit diagram showing a high-frequency oscillator according to Embodiment 1 of the present invention. In the figure, an FET (transistor, field effect transistor) 1 is an active element for oscillation that amplifies power in the circuit of the high-frequency oscillator. It is used as In the coupler 2 of the left-handed device, when the port 1 is connected to the gate terminal of the FET 1 and the port 1 is an input port, the ports 2 and 4 are the isolation ports and the port 3 is the frequency band fb1. For the frequency band fb2, the port 2 is a passing port, and the ports 3 and 4 are isolation ports. The isolation terminal 3 is an insulated terminal. The resonance circuit (first resonance circuit) 4a is connected to the port 3 of the coupler 2 and resonates at the frequency f1 included in the frequency band fb1. The resonance circuit (second resonance circuit) 4b is connected to the port 2 of the coupler 2 and resonates at the frequency f2 included in the frequency band fb2. The tuning circuit 5 is connected to the source terminal of the FET 1 and can change the resonance frequency in the frequency bands fb1 and fb2 by controlling the capacitance of a varactor diode or the like. The reactance circuit 6 is connected to the drain terminal of the FET 1. The load resistor 7 is connected to the reactance circuit 6 and extracts oscillation power.

Next, the operation will be described.
In the high-frequency oscillator shown in FIG. 1, noise in the high-frequency oscillator circuit is amplified by the FET 1, and the coupler 2 by the left-handed device connected to each terminal of the FET 1, the resonance circuit 4, the tuning circuit 5, and the reactance circuit 6, A part of the amplified power is returned to the FET 1, and the power is further amplified by the FET 1 to perform an oscillation operation and oscillate and output from the load resistor 7. The oscillation frequency is a frequency that satisfies the following expressions (1) and (2).
Re (Za) + Re (Zr) <0 (1)
Im (Za) + Im (Zr) = 0 (2)
However, Za is the impedance when the FET 1 side is viewed from the base terminal, Zr is the impedance when the coupler 2 side of the left-handed device is viewed from the base terminal, Re is a real component, and Im is an imaginary component.

FIG. 2 is a characteristic diagram showing the pass frequency band of the coupler. As shown in FIG. 2, the coupler 2 of the left-handed device passes the frequency band fb1 including the frequency f1 between the ports 1 and 3, and the port 1 , 2 passes through a frequency band fb2 including a frequency f2 that is different from the frequency band fb1. At this time, the frequency f1 inputted to the coupler 2 by the left-handed device from the gate terminal of the FET1 passes through between the ports 1 and 3 of the coupler 2 and is reflected by the resonance circuit 4a. Reflected by the resonance circuit 4b between the two.
FIG. 3 is a characteristic diagram showing switching of the gain by the tuning circuit. As shown in FIG. 3, in the tuning circuit 5, the resonance frequency can be varied in the frequency bands fb1 and fb2 by a variable device such as a variable capacitor. . By controlling the tuning circuit 5 so that a gain can be obtained at the frequency f1 or the frequency f2, the oscillation condition can be satisfied and the oscillation output can be obtained. This shows that the oscillation frequency can be easily switched.

As described above, according to the first embodiment, the resonant circuit 4a, the ports 1 and 3 of the coupler 2, the FET 1 and the tuning circuit 5 oscillate in the frequency band fb1, and the resonant circuit 4b and the ports 2 and 1 of the coupler 2 are oscillated. A high-frequency oscillator that can oscillate in the frequency band fb2 through the FET 1 and the tuning circuit 5 and realizes a wide oscillation frequency while maintaining miniaturization by using the coupler 2 composed of a left-handed device. Obtainable.
In addition, the active element for oscillation can be easily configured by the FET 1.
In the first embodiment, the tuning circuit 5 is connected to the source terminal of the FET 1. However, the tuning circuit 5 may be connected to the drain terminal of the FET 1 or the source terminal and the drain terminal of the FET 1. Can play.
In the first embodiment, the load resistor 7 is connected to the reactance circuit 6. However, the load resistor 7 may be connected to the tuning circuit 5, and the same effect can be obtained.

Embodiment 2. FIG.
4 is a circuit diagram showing a high-frequency oscillator according to Embodiment 2 of the present invention. In the figure, a tuning circuit (first tuning circuit) 5a is connected to the port 3 of the coupler 2 and has a resonance frequency in the frequency band fb1. Can be varied. The tuning circuit (second tuning circuit) 5b is connected to the port 2 of the coupler 2 and can change the resonance frequency in the frequency band fb2. The reactance circuit 6a is connected to the source terminal of the FET1. Other configurations are the same as those in FIG.

Next, the operation will be described.
In the first embodiment, the oscillation frequency can be easily switched by connecting the two resonance circuits 4a and 4b having different resonance frequencies to the coupler 2 of the left-handed device and controlling the frequency at which the gain is obtained by the tuning circuit 5. It was shown that. In the second embodiment, it will be shown that a wide band of oscillation frequency can be easily realized by connecting two tuning circuits 5a and 5b having different resonance frequency bands to the coupler 2 of the left-handed device.
In the high-frequency oscillator shown in FIG. 4, noise in the high-frequency oscillator circuit is amplified by the FET 1 and amplified by the coupler 2, the tuning circuit 5, and the reactance circuit 6 by the left-handed device connected to each terminal of the FET 1. Part of the electric power is returned to the FET 1, and the oscillation is performed by further amplifying the electric power by the FET 1, and the oscillation is output from the load resistor 7. The oscillation frequency is a frequency that satisfies the expressions (1) and (2).

At this time, the frequency f1 input to the coupler 2 by the left-handed device from the gate terminal of the FET1 passes between the ports 1 and 3 of the coupler 2 and is reflected by the tuning circuit 5a, and the frequency f2 is the port 1 of the coupler 2 The signal is reflected by the tuning circuit 5b between the two and satisfies the oscillation condition in two bands.
FIG. 5 is a characteristic diagram showing the switching of gain by the tuning circuit. As shown in FIG. 5, when oscillating in the frequency band fb1, for example, 10V is supplied to the varactor diode of the tuning circuit 5b for the frequency band fb2. Then, by fixing the tuning circuit 5b at a frequency with no gain, it is prevented from oscillating in the frequency band fb2, and when oscillating in the frequency band fb2, the varactor diode of the tuning circuit 5a for the frequency band fb1 is, for example, 0V By supplying and fixing the tuning circuit 5a at a frequency with no gain, it is possible to prevent oscillation in the frequency band fb1.

As described above, according to the second embodiment, the tuning circuit 5a, the ports 1 and 3 of the coupler 2 oscillate in the frequency band fb1 through the FET 1 and the reactances 6 and 6a, and the tuning circuit 5b and the ports 1 and 2 of the coupler 2 are oscillated. 2. A high frequency that can oscillate in the frequency band fb2 through the FET 1 and the reactances 6 and 6a, and realizes a wide oscillation frequency while maintaining a small size by using the coupler 2 constituted by a left-handed device. An oscillator can be obtained.
In the second embodiment, a wide oscillation band can be obtained by making the highest frequency of the frequency band fb1 and the lowest frequency of the frequency band fb2 the same.
In the second embodiment, the load resistor 7 is connected to the reactance circuit 6. However, the load resistor 7 may be connected to the reactance circuit 6a, and similar effects can be obtained.

Embodiment 3 FIG.
FIG. 6 is a circuit diagram showing a high-frequency oscillator according to Embodiment 3 of the present invention. In the figure, a tuning circuit 5c is connected to the source terminal of the FET 1, and the resonance frequency can be varied in the frequency bands fb1 and fb2. is there. Other configurations are the same as those in FIG.

Next, the operation will be described.
In the second embodiment, it has been shown that the oscillation frequency can be easily widened by connecting the two tuning circuits 5a and 5b having different resonance frequency bands to the coupler 2 of the left-handed device. In the third embodiment, the oscillation frequency is controlled by connecting two tuning circuits 5a and 5b having different resonance frequency bands to the coupler 2 of the left-handed device and controlling the band in which gain is obtained by the other tuning circuit 5c. It will be shown that the wider band can be realized more easily.
In the high-frequency oscillator shown in FIG. 6, noise in the high-frequency oscillator circuit is amplified by the FET 1, and amplified by the coupler 2, the tuning circuit 5, and the reactance circuit 6 by the left-handed device connected to each terminal of the FET 1. Part of the electric power is returned to the FET 1, and the oscillation is performed by further amplifying the electric power by the FET 1, and the oscillation is output from the load resistor 7. The oscillation frequency is a frequency that satisfies the expressions (1) and (2).

At this time, the frequency f1 input to the coupler 2 by the left-handed device from the gate terminal of the FET1 passes between the ports 1 and 3 of the coupler 2 and is reflected by the tuning circuit 5a, and the frequency f2 is the port 1 of the coupler 2 Reflected by the tuning circuit 5b between the two, the expression (2) is satisfied in two bands.
Further, by controlling the tuning circuit 5c to obtain a gain in the frequency band fb1 or the frequency band fb2, the oscillation conditions can be satisfied and the oscillation output can be obtained. Thus, it can be seen that the oscillation frequency band can be easily switched.

As described above, according to the third embodiment, it is possible to easily obtain a broad oscillation frequency by controlling the frequency band in which gain is obtained by the tuning circuit 5c.
In the third embodiment, a wide oscillation band can be obtained by making the highest frequency of the frequency band fb1 and the lowest frequency of the frequency band fb2 the same.
In the third embodiment, the tuning circuit 5c is connected to the source terminal of the FET 1. However, the tuning circuit 5c may be connected to the drain terminal of the FET 1, or the source terminal and the drain terminal of the FET 1. Can play.

Embodiment 4 FIG.
FIG. 7 is a circuit diagram showing a high-frequency oscillator according to Embodiment 4 of the present invention. In the figure, a coupler (second coupler) 2a based on a left-handed device has port 1 connected to the source terminal of FET 1 and its port. When 1 is an input port, ports 2 and 4 are isolation ports and port 3 is a passing port for frequency band fb1, and port 2 is a passing port and port 3 for frequency band fb2. , 4 are isolation ports. The isolation terminal 3a is an insulated terminal.
The tuning circuit (third tuning circuit) 5d is connected to the port 3 of the coupler 2a and can change the resonance frequency in the frequency band fb1. The tuning circuit (fourth tuning circuit) 5e is connected to the port 2 of the coupler 2a and can change the resonance frequency in the frequency band fb2. Other configurations are the same as those in FIG.

Next, the operation will be described.
In the third embodiment, the oscillation frequency is controlled by connecting the two tuning circuits 5a and 5b having different resonance frequency bands to the coupler 2 of the left-handed device and controlling the band in which the gain is obtained by the other tuning circuit 5c. It was shown that the widening of the band can be realized more easily. In the fourth embodiment, the oscillation frequency is obtained by connecting the two tuning circuits 5a and 5b having different resonance frequency bands to the coupler 2 of the left-handed device, the two terminals of the FET 1, or all the three terminals. It will be shown that the wider band can be realized more easily.
In the high-frequency oscillator shown in FIG. 7, noise in the high-frequency oscillator circuit is amplified by the FET 1 and amplified by the coupler 2, the tuning circuit 5, and the reactance circuit 6 by the left-handed device connected to each terminal of the FET 1. Part of the electric power is returned to the FET 1, and the oscillation is performed by further amplifying the electric power by the FET 1, and the oscillation is output from the load resistor 7. The oscillation frequency is a frequency that satisfies the expressions (1) and (2).

For example, as shown in FIG. 7, when two tuning circuits 5 having different resonance frequency bands from the coupler 2 are connected to the two terminals of the FET 1, they are input from the gate terminal of the FET 1 to the coupler 2 by the left-handed device. The frequency f1 passes between the ports 1 and 3 of the coupler 2 and is reflected by the tuning circuit 5a, and the frequency f2 passes between the ports 1 and 2 of the coupler 2 and is reflected by the tuning circuit 5b. Satisfy (2).
Further, since the FET 1 has a source terminal provided with a coupler 2a using a left-handed device and a tuning circuit 5d for obtaining a gain in the frequency band fb1 and a tuning circuit 5e for obtaining a gain in the frequency band fb2, a frequency at which gain can be obtained. Can be controlled in a wide band, and a broad oscillation frequency can be obtained more easily.

As described above, according to the fourth embodiment, by controlling the frequency band in which gain is obtained by the tuning circuits 5d and 5e, a broadband oscillation frequency can be obtained more easily.
In the fourth embodiment, a single wide oscillation band can be obtained by making the highest frequency of the frequency band fb1 and the lowest frequency of the frequency band fb2 the same.
In the fourth embodiment, the coupler 2a and the tuning circuits 5d and 5e are connected to the source terminal of the FET1, but the coupler 2a and the tuning circuits 5d and 5e are connected to the drain terminal of the FET1 and the source terminal and the drain terminal of the FET1. Connections may be made and similar effects can be achieved.

Embodiment 5. FIG.
FIG. 8 is a circuit diagram showing a high-frequency oscillator according to Embodiment 5 of the present invention. In the figure, BJT (transistor, bipolar transistor) 8 is an active element for oscillation that amplifies the power in the circuit of this high-frequency oscillator. It is used. Other configurations are the same as those in FIG.

Next, the operation will be described.
In the first to fourth embodiments, an FET 1 is used as an active element for oscillation, and a coupler 2, a resonance circuit 4, a tuning circuit 5, and a reactance circuit 6 are connected to a terminal of the FET 1 by a left-handed device. Thus, it was shown that the oscillation frequency can be switched or a broadband oscillation frequency can be obtained. In the fifth embodiment, it is shown that the same effect can be obtained by using BJT 8 as an active element for oscillation.
In the high-frequency oscillator shown in FIG. 8, noise in the circuit of the high-frequency oscillator is amplified by the BJT 8 and amplified by the coupler 2, the tuning circuit 5, and the reactance circuit 6 by the left-handed device connected to each terminal of the BJT 8. A part of the electric power is returned to the BJT 8, and the electric power is further amplified by the BJT 8 to perform an oscillation operation and oscillate and output from the load resistor 7. The oscillation frequency is a frequency that satisfies the expressions (1) and (2).

At this time, the frequency f1 input to the coupler 2 by the left-handed device from the base terminal of the BJT 8 is reflected by the tuning circuit 5a through between the ports 1 and 3 of the coupler 2, and the frequency f2 is the port 1 of the coupler 2 Reflected by the tuning circuit 5b between the two, the expression (2) is satisfied in two bands.
Further, since the BJT 8 has an emitter terminal provided with a coupler 2a using a left-handed device, a tuning circuit 5d for obtaining a gain in the frequency band fb1, and a tuning circuit 5e for obtaining a gain in the frequency band fb2, a frequency at which gain can be obtained. Can be controlled in a wide band, and a broad oscillation frequency can be obtained more easily.

As described above, according to the fifth embodiment, by controlling the frequency band in which gain is obtained by the tuning circuits 5d and 5e, a broadband oscillation frequency can be obtained more easily.
In addition, the active element for oscillation can be easily configured by the BJT 8.
In the fifth embodiment, a wide oscillation band can be obtained by making the highest frequency of the frequency band fb1 and the lowest frequency of the frequency band fb2 the same.
In the fifth embodiment, the coupler 2a and the tuning circuits 5d and 5e are connected to the emitter terminal of the BJT 8, but the coupler 2a and the tuning circuits 5d and 5e are connected to the collector terminal of the BJT 8, and the emitter terminal and collector terminal of the BJT 8. Connections may be made and similar effects can be achieved.

Embodiment 6 FIG.
FIG. 9 is a circuit diagram showing a high-frequency synthesizer according to Embodiment 6 of the present invention. In the figure, a voltage-controlled oscillator (oscillator) 9 outputs an oscillation frequency corresponding to the control voltage. The coupler 2b of the left-handed device is connected to the frequency band fb1 including the fundamental wave fo of the oscillation frequency by the voltage controlled oscillator 9 when the port 1 is connected to the output of the voltage controlled oscillator 9 and the port 1 is an input port. In this case, ports 2 and 4 are isolation ports and port 3 is a passage port. For frequency band fb2 including the second harmonic 2fo of the oscillation frequency of voltage-controlled oscillator 9, port 2 is a passage port and port. 3 and 4 are isolation ports. The output terminal 10 is connected to the port 2 of the coupler 2b and outputs the second harmonic 2fo of the oscillation frequency of the voltage controlled oscillator 9. The phase locked loop 11 is connected to the port 3 of the coupler 2b, and supplies a control voltage to the voltage controlled oscillator 9 according to the phase comparison between the fundamental wave fo of the oscillation frequency to be fed back and the reference wave.

Next, the operation will be described.
In the high-frequency synthesizer shown in FIG. 9, the fundamental wave fo and the second harmonic 2fo can be separated by inputting the output of the voltage controlled oscillator 9 to the coupler 2 of the left-handed device, and the fundamental wave fo is phase-shifted. By using the feedback loop of the synchronous loop 11 to stably output the oscillation frequency of the voltage controlled oscillator 9, and outputting the second harmonic 2fo to the output terminal 10, the output frequency of the high frequency is output by the low-frequency phase-locked loop 11. Is obtained. Further, it is possible to reduce the size without using a bandpass filter.

As described above, according to the sixth embodiment, the high-frequency second harmonic 2fo can be output from the port 2 of the coupler 2, and the band pass can be achieved by using the coupler 2 constituted by the left-handed device. It is possible to obtain a high-frequency synthesizer that achieves a high frequency while maintaining a reduction in size without providing a filter.
As the voltage controlled oscillator 9, the high frequency oscillator shown in the first to fifth embodiments may be applied.

1 is a circuit diagram showing a high frequency oscillator according to a first embodiment of the present invention. It is a characteristic view which shows the pass frequency band of a coupler. It is a characteristic view which shows the switching of the gain by a tuning circuit. It is a circuit diagram which shows the high frequency oscillator by Embodiment 2 of this invention. It is a characteristic view which shows the switching of the gain by a tuning circuit. It is a circuit diagram which shows the high frequency oscillator by Embodiment 3 of this invention. It is a circuit diagram which shows the high frequency oscillator by Embodiment 4 of this invention. It is a circuit diagram which shows the high frequency oscillator by Embodiment 5 of this invention. It is a circuit diagram which shows the high frequency synthesizer by Embodiment 6 of this invention.

Explanation of symbols

1 FET (transistor, field effect transistor), 2, 2b coupler, 2a coupler (second coupler), 3, 3a isolation terminal, 4a resonance circuit (first resonance circuit), 4b resonance circuit (second resonance) Circuit), 5, 5c tuning circuit, 5a tuning circuit (first tuning circuit), 5b tuning circuit (second tuning circuit), 5d tuning circuit (third tuning circuit), 5e tuning circuit (fourth tuning circuit) Circuit), 6, 6a reactance circuit, 7 load resistance, 8 BJT (transistor, bipolar transistor), 9 voltage controlled oscillator (oscillator), 10 output terminal, 11 phase-locked loop.

Claims (7)

A transistor used as an active element for oscillation;
When a first port is connected to the first terminal of the transistor and the first port is used as an input port, the second and fourth ports are isolation ports for the first frequency band. , A coupler constituted by a left-handed device in which the third port is a passing port, the second port is a passing port, and the third and fourth ports are isolation ports for the second frequency band When,
A first resonance circuit connected to the third port of the coupler and resonating at a first frequency included in a first frequency band;
A second resonant circuit connected to the second port of the coupler and resonating at a second frequency included in a second frequency band;
A reactance circuit connected to each of the second and third terminals of the transistor;
A load resistor connected to at least one of the reactance circuits and extracting oscillation power;
At least one of the reactance circuits is a tuning circuit capable of changing a resonance frequency in the first and second frequency bands. A transistor used as an active element for oscillation;
When a first port is connected to the first terminal of the transistor and the first port is used as an input port, the second and fourth ports are isolation ports for the first frequency band. , A coupler constituted by a left-handed device in which the third port is a passing port, the second port is a passing port, and the third and fourth ports are isolation ports for the second frequency band When,
A first tuning circuit connected to the third port of the coupler and capable of varying a resonance frequency in a first frequency band;
A second tuning circuit connected to the second port of the coupler and capable of varying a resonance frequency in a second frequency band;
A reactance circuit connected to each of the second and third terminals of the transistor;
A high-frequency oscillator comprising a load resistor connected to at least one of the reactance circuits and extracting oscillation power.   3. The high-frequency oscillator according to claim 2, wherein at least one of the reactance circuits is a tuning circuit capable of changing a resonance frequency in the first and second frequency bands. When the first port is connected to the second or third terminal of the transistor and the first port is used as an input port, the second and fourth ports are isolated for the first frequency band. And the third port is a passing port. For the second frequency band, the second port is a passing port and the third and fourth ports are isolation ports. A second coupler,
A third tuning circuit connected to the third port of the second coupler and capable of changing a resonance frequency in a first frequency band;
4. The high-frequency oscillator according to claim 3, further comprising a fourth tuning circuit connected to the second port of the second coupler and capable of changing a resonance frequency in a second frequency band. Transistor is
5. The high frequency oscillator according to claim 1, wherein the high frequency oscillator is a field effect transistor. Transistor is
5. The high-frequency oscillator according to claim 1, wherein the high-frequency oscillator is a bipolar transistor. An oscillator that outputs an oscillation frequency according to the control voltage;
When the first port is connected to the output of the oscillator and the first port is used as the input port, the second and second frequency bands are applied to the first frequency band including the fundamental wave of the oscillation frequency of the oscillator. 4 port is an isolation port, a third port is a pass port, and for the second frequency band including the second harmonic of the oscillation frequency by the oscillator, the second port is the pass port, And a coupler constituted by a left-handed device in which the fourth port is an isolation port;
A high-frequency synthesizer comprising a phase-locked loop connected to the third port of the coupler and supplying a control voltage to the oscillator in accordance with a phase comparison between a fundamental wave of the oscillation frequency to be fed back and a reference wave.

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