JP2003224420A - Microwave oscillator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microwave oscillator capable of suppressing fluctuations in the temperature of oscillation frequencies by controlling the gate voltages of an FET used as an oscillation element. <P>SOLUTION: The microwave oscillator comprising an FET2 as the oscillation element, a resonant circuit 8 connected to the FET2, a gate bias circuit and a drain bias circuit for the FET2 and having a negative voltage between the drain and the source voltage of the FET2, wherein two circuits which are connected in series with thermistors 13a and 13b with resisters 14a and 14b being respectively connected in parallel are connected in series, a temperature compensated circuit 10 for controlling the gate voltage of the FET2 is provided, in such manner that the center point of the two circuits becomes an output, and an operational amplifier 20 is connected at the output of the compensated circuit 10. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave oscillator, and more particularly to a microwave oscillator having a temperature compensation circuit for stabilizing the oscillation frequency.

[0002]

2. Description of the Related Art FIG. 5 shows, for example, "Simple temperature compensation of oscillation frequency of MIC electronic tuning FET oscillator" by Seino et al.
FIG. 3 is a circuit diagram showing a configuration of a microwave oscillator shown in (National Conference of IEICE 1981). In the figure,
1 is an output terminal, 2 is an FET that is an oscillating element, and 3 is an FET
A reflection circuit connected to 2, 4 is a source voltage terminal for operating the FET 2, 5 is a self-biasing resistor of the FET 2, 6 is a half-wavelength line of a desired frequency for blocking a desired frequency, 7 is a quarter wavelength line of a desired frequency for grounding at a desired frequency, 8 is a resonance circuit connected to the FET 2, 9 is a varactor diode for changing the oscillation frequency, and 10 is connected to the varactor diode 9. A temperature compensating circuit, 11 is a control voltage terminal serving as an input voltage of the temperature compensating circuit 10, 12 is an output voltage terminal of the temperature compensating circuit 10 for controlling the varactor diode 9, 13 is a thermistor whose resistance value changes due to temperature change, and 14 is A constant resistance that adjusts a change in the resistance value of the thermistor 13, and 15 is a voltage dividing resistance.

Next, the operation will be described. In the microwave oscillator shown in FIG. 5, the reflection circuit 3 and the resonance circuit 8 are connected to the FET 2 which is an oscillating element to create a loop gain, and the phases of the loops are superposed in the same phase to amplify power. And oscillate.

The resonant circuit 8 is loaded with a varactor diode 9 which is grounded by a quarter wavelength line 7. By controlling the DC voltage applied to the varactor diode 9, the junction capacitance of the varactor diode 9 is controlled. To change the oscillation frequency.

The output voltage terminal 12 of the temperature compensating circuit 10 is connected to the varactor diode 9 so that the DC voltage V ₂ applied to the varactor diode 9 becomes higher at high temperature than in the case without the temperature compensating circuit 10. Since it is set, the oscillation frequency becomes high and fluctuations at room temperature are suppressed. Further, when the temperature is low, the operation is reversed, the oscillation frequency is lowered, and the fluctuation from the normal temperature is suppressed.

[0006]

The conventional temperature compensation circuit for the microwave oscillator shown in FIG. 5 is effective when the oscillation frequency monotonously decreases with respect to temperature, as shown in FIG. On the contrary, there is a problem that the temperature cannot be compensated when it has an inflection point without increasing monotonously or changing monotonically. Further, since the varactor diode 9 is used for the resonance circuit 8, in the case of an oscillator using a high Q resonator, for example, a dielectric resonator, the Q value is deteriorated by the internal resistance of the varactor diode 9. As a result, there is a problem that the phase noise becomes worse.

The present invention has been made in view of the above points, and an object of the present invention is to obtain a microwave oscillator capable of suppressing the temperature fluctuation of the oscillation frequency by controlling the gate voltage of the FET used as the oscillation element. And

[0008]

A microwave oscillator according to the present invention has a FET as an oscillation element, a resonance circuit connected to the FET, a gate bias circuit and a drain bias circuit of the FET, In a microwave oscillator in which the drain-source voltage of the FET is negative, two circuits in which other resistors are connected in series are connected in series to a thermistor in which resistors are connected in parallel, and the midpoint thereof is used as an output of the FET. It is characterized in that a temperature compensation circuit for controlling the gate voltage is provided.

An operational amplifier is connected to the output of the temperature compensation circuit.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. Embodiment 1. 1 is a circuit diagram showing a configuration of a microwave oscillator according to a first embodiment of the present invention. In FIG. 1, the same parts as those in the conventional example shown in FIG. As new symbols, 16 is a dielectric resonator, 17 is a 50Ω terminator, and 18 is a drain voltage terminal of FET2.

In the temperature compensating circuit 10 shown in FIG. 1, a circuit in which a thermistor 13a and a variation width adjusting resistor 14a are connected in parallel and a voltage dividing resistor 15a is connected in series, a thermistor 13b, and a variation width adjusting resistor 14b. , Resistor for voltage division 15
The circuit in which b is similarly connected is connected in series, and the output voltage at the midpoint thereof is applied to the gate terminal.

Next, the operation will be described. In the microwave oscillator of the present invention, the F used as the oscillation element
The terminal voltage of ET2 is applied so that the drain-source voltage becomes negative. Since the drain-gate voltage becomes smaller than that when applied so that the drain-source voltage becomes positive, the drain-gate voltage is different from the drain-gate voltage as shown in Fig. 2 due to the diode characteristics. The capacitance change between them becomes large. When the capacitance change between the drain and the gate is large, the change in the reflection phase of the FET 2 is large. As a result, it becomes easy to suppress the temperature fluctuation of the oscillation frequency by controlling the gate voltage.

Further, as shown in FIG. 3, the temperature compensation circuit 1
The output voltage of 0 is the thermistor 13, the variable width adjusting resistor 1
4. By adjusting each of the voltage dividing resistors 15, four kinds of characteristics can be obtained with respect to temperature. Therefore, even when the characteristics of the oscillation frequency with respect to temperature have a positive or negative slope or an inflection point, It is possible to suppress the temperature fluctuation of the oscillation frequency.

In FIG. 1, the combined resistance of the thermistor 13a, the variation width adjusting resistor 14a and the voltage dividing resistor 15a is Ra.
When the combined resistance of the thermistor 13b, the variation width adjusting resistor 14b, and the voltage dividing resistor 15b is Rb, the output voltage of the temperature compensating circuit 10 obtains four characteristics with respect to temperature as shown in FIG. To do so, make the following adjustments.

In the case of monotonic increase: The slope (rate of change) of the combined resistance Rb with respect to temperature is made larger than that of the combined resistance Ra. In order to increase the inclination, the resistance 14b is increased and the resistance 14a is decreased.

In the case of monotonic decrease: The slope (rate of change) of the combined resistance Ra with respect to temperature is increased as compared with the combined resistance Rb. In order to increase the inclination, the resistance 14a is increased and the resistance 14b is decreased.

When there is one inflection point (maximum value): With the temperature having the maximum value as a reference, the slope of the combined resistance Rb with respect to the temperature is increased as compared with the combined resistance Ra at a low temperature, and the temperature is At a high point, the slope of the combined resistance Ra with respect to temperature is made larger than that of the combined resistance Rb. The resistance 14b is increased, the resistance 15b is increased, and the resistance 15a is decreased.

When there is one inflection point (minimum value): With the temperature having the minimum value as a reference, the slope of the combined resistance Ra with respect to the temperature is made larger than that of the combined resistance Rb at a low temperature. At a high point, the slope of the combined resistance Rb with respect to the temperature is made larger than that of the combined resistance Ra. The resistance 14a is increased, the resistance 15a is increased, and the resistance 15b is decreased.

Therefore, according to the first embodiment, without using a varactor diode, the terminal voltage of the FET used as the oscillating element of the microwave oscillator has a positive or negative slope of the oscillation frequency characteristic with respect to temperature, or Even if there is an inflection point, temperature fluctuation of the oscillation frequency can be suppressed by controlling with a temperature compensation circuit composed of a resistor and a thermistor.

Embodiment 2. FIG. 4 is a circuit diagram showing the configuration of the microwave oscillator according to the second embodiment of the present invention. 4, the same parts as those in the first embodiment shown in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. As new symbols, 19 is a gate voltage terminal, 20 is an operational amplifier, and 21 is a reference voltage resistor.

In the first embodiment, with the drain-source voltage being negative, two thermistors in which resistors are connected in parallel are connected in series with two circuits in which resistors are connected in series, and the temperature compensation is performed with the middle point as the output. It was shown that the circuit makes it easy to suppress the temperature fluctuation of the oscillation frequency by controlling the gate voltage. In the second embodiment, the temperature compensation circuit using an operational amplifier at the output of the temperature compensation circuit controls the drain voltage to suppress the temperature variation of the oscillation frequency.

Next, the operation will be described. The terminal voltage of the FET2 used as the oscillating element is applied so that the drain-source voltage becomes negative. Since the drain-gate voltage is smaller than when applied so that the drain-source voltage becomes positive, the capacitance change between the drain-gate is large with respect to the drain-gate voltage due to the diode characteristics. Become. When the capacitance change between the drain and the gate is large, the change in the reflection phase of the FET 2 is large.
As a result, it becomes easy to suppress the temperature fluctuation of the oscillation frequency by controlling the drain voltage.

Further, since the output voltage of the temperature compensation circuit can obtain four kinds of characteristics with respect to temperature, even when the characteristics of the oscillation frequency with respect to temperature have a positive or negative slope or an inflection point, the oscillation voltage is oscillated. It is possible to suppress the temperature fluctuation of the frequency. Further, by using the operational amplifier 20, there is an effect that a change in drain current due to a change in drain voltage does not affect the output voltage of the temperature compensation circuit.

[0024]

As described above, according to the present invention, the FET as the oscillation element, the resonance circuit connected to the FET, the gate bias circuit and the drain bias circuit of the FET, and the FET are provided. In a microwave oscillator with a negative drain-source voltage, two circuits in which other resistors are connected in series are connected in series to a thermistor in which resistors are connected in parallel. Since the temperature compensating circuit for controlling the temperature is provided, the temperature fluctuation of the oscillation frequency can be suppressed by controlling the gate voltage by the temperature compensating circuit.

Further, since the operational amplifier is connected to the output of the temperature compensation circuit, there is an effect that the change of the drain current due to the change of the drain voltage does not affect the output voltage of the temperature compensation circuit.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of a microwave oscillator according to a first embodiment of the present invention.

FIG. 2 is a characteristic diagram of drain-gate capacitance with respect to drain-gate voltage of FET 2 of FIG.

3 is a characteristic diagram of the output voltage with respect to the temperature of the temperature compensation circuit 10 of FIG.

FIG. 4 is a circuit diagram showing a configuration of a microwave oscillator according to a second embodiment of the present invention.

FIG. 5 is a circuit diagram showing a configuration of a conventional microwave oscillator.

6 is a characteristic diagram of a temperature compensation circuit of the conventional microwave oscillator shown in FIG.

[Explanation of symbols]

1 output terminal, 2 field effect transistor (FET),
3 reflection circuit, 4 source voltage terminal, 5 self-biasing resistor, 7 1/4 wavelength line, 8 resonant circuit, 9 varactor diode, 10 temperature compensation circuit, 11 control voltage terminal, 12 output voltage terminal, 13 thermistor, 14
Variable width adjusting resistor, 15 voltage dividing resistor, 16 dielectric resonator, 1750 Ω terminator, 18 drain voltage terminal,
19 gate voltage terminal, 20 operational amplifier, 21 reference voltage resistor.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kenichi Tajima             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. (72) Inventor Yoji Isoda             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. (72) Inventor, Miyatake             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. (72) Inventor Norio Takeuchi             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. F term (reference) 5J081 AA11 CC17 DD04 DD24 EE02                       EE03 EE10 EE18 FF05 FF07                       FF23 FF28 GG07 KK02 KK09                       KK12 KK22 LL03 MM01

Claims (2)

[Claims] 1. A drain of the FET, comprising a field effect transistor (hereinafter referred to as FET) as an oscillating element, a resonance circuit connected to the FET, a gate bias circuit and a drain bias circuit of the FET,・ In a microwave oscillator in which the voltage between sources is negative, two thermistors in which resistors are connected in parallel are connected in series with other resistors in series, and the gate voltage of the FET is controlled using the midpoint as an output. A microwave oscillator having a temperature compensating circuit for 2. The microwave oscillator according to claim 1, wherein an operational amplifier is connected to the output of the temperature compensation circuit.