JPH09284014A - Phase characteristic stabilizing circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a phase adjustment circuit of a directional coupler stable against temperature changes. SOLUTION: An oscillated frequency is changed by changing a bias voltage of a varactor diode 1. An F-V conversion circuit 4 converts the oscillated frequency of the oscillator 3 into a voltage, which is compared with a reference voltage at comparator circuit 5, its output controls a voltage controlled source 6, and its output is fed back to a bias power supply of the varactor diode 1. The bias voltage of the varactor diode 1 is to be a voltage to apply temperature compensation to the varactor diode 1. The temperature compensation bias voltage of the varactor diode 1 is the same as varactor diodes 7, 8, then the temperature compensation bias voltage is fed to the varactor diodes 7, 8 via a voltage mixer 15, then the phase characteristic of the directional coupler 11 is sufficiently made stable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase characteristic stabilizing circuit, and more particularly to a phase characteristic stabilizing circuit for a directional coupler.

[0002]

2. Description of the Related Art A directional coupler outputs a signal applied to an input terminal 13 to an output terminal 12 via a coupling line 14 as shown in FIG. At this time, the termination point 9 of the coupled line 14
If a capacitor is connected between 10 and 10, the reflection coefficient of the coupling line 14 can be changed and the phase between the input and output signals can be shifted. As this capacitance, for example, variable capacitance diodes 7 and 8 are connected as shown in the figure (in anti-series), and the bias voltage of the variable capacitance diodes 7 and 8 is changed by adjusting the bias voltage regulator 16. It is possible to adjust the phase between the input and output signals by changing the equivalent capacitance of.

[0003]

The phase adjusting circuit of the directional coupler using the variable capacitance diode as shown in FIG. 4 is convenient because the phase can be freely and continuously adjusted only by changing the voltage. When the temperature changes, the equivalent capacitance of the varactor diode changes accordingly, and the inconvenience of changing the phase characteristic of the directional coupler remains.

An object of the present invention is to provide a phase adjusting circuit for a directional coupler which is stable against temperature changes.

[0005]

A phase characteristic stabilizing circuit for a directional coupler according to the present invention is a voltage control type circuit provided between a pair of coupling lines and terminal points of the pair of coupling lines to determine phase characteristics. A phase characteristic stabilizing circuit of a directional coupler including a variable capacitance element, comprising compensation voltage generating means for generating a compensation voltage for compensating the temperature characteristic of the variable capacitance element, It is characterized in that it is supplied to the variable capacitance element.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The operation of the present invention is as follows.
The temperature compensation voltage of the variable capacitance diode is derived and applied to the variable capacitance diode of the phase adjustment circuit of the directional coupler to correct the phase characteristic of the phase adjustment circuit of the directional coupler.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the construction of an embodiment of a phase adjusting circuit for a directional coupler according to the present invention.
The parts equivalent to are denoted by the same reference numerals. In addition, overlapping description is omitted.

In FIG. 1, an oscillator 3 is composed of an oscillation circuit 2, a variable capacitance diode 1 and a resistor R. By changing the bias voltage of the variable capacitance diode 1,
The oscillation frequency is changed by changing the capacitance value.

The F-V conversion circuit 4 is a circuit for converting a frequency into a voltage. The F-V conversion circuit 4 converts the oscillation frequency of the oscillator 3 into a voltage, compares it with a reference voltage in a comparison circuit 5, and controls the voltage-controlled voltage source 6 with its output. Then, it is fed back to the bias power source of the variable capacitance diode 1. If the loop gain of this feedback loop is sufficiently high, the oscillation frequency of the oscillator 3 can be stably kept constant even if the temperature changes. Therefore, the bias voltage of the variable capacitance diode 1, that is, the output voltage of the voltage control voltage source 6 should be the voltage (bias) voltage obtained by temperature compensation of the variable capacitance diode 1.

Since the variable capacitance diodes 1, 7 and 8 are selected for the same type (same characteristics), the temperature compensation bias voltage of the variable capacitance diode 1 is the same as that of the variable capacitance diode 7.
Also for 8 and 8, the temperature compensation bias voltage is used. Therefore, if this is added to the variable capacitance diodes 7 and 8 via the voltage mixer 15, the variable capacitance diodes 7 and 8 can be temperature-compensated and the phase characteristics of the directional coupler 11 can be sufficiently stabilized.

The adjustment of the phase shift amount of the directional coupler 11 is achieved by the bias voltage adjuster 16 finely adjusting the bias voltages of the variable capacitance diodes 7 and 8 through the voltage mixer 15. .

The temperature compensation bias voltage generating circuit for the variable capacitance diodes 7 and 8 includes an example as shown in FIG. 2 in addition to the example shown in FIG. In FIG. 2, the phase shifter 26 utilizes the phase shift characteristic of the resonance circuit composed of the coil 20 and the variable capacitance diode 21 acting as a capacitance, and the input and output signals of the phase shifter 26 are multiplied by the multiplier 22. Together, they form a demodulator that demodulates the FM wave signal input. The signal demodulated by the multiplier 22 becomes a demodulated output through the low-pass filter 24 that removes the carrier component.

On the other hand, the voltage corresponding to the center potential of the demodulation characteristic obtained from the demodulation output through the low-pass filter 25 having a sufficiently large time constant is compared with the reference voltage by the comparison circuit 23, and the bias voltage is applied to the variable capacitance diode 21. As feedback.

When the capacitance of the varactor diode 21 changes with temperature, the phase shift amount of the phase shifter 26 changes, so that the center potential of the demodulation characteristic changes. If the change in the center potential of the demodulation characteristic is detected and fed back to the bias voltage of the variable capacitance diode 21, the temperature compensation bias voltage of the variable capacitance diode can be obtained as the output of the comparison circuit 23 as in the case of FIG. it can.

FIG. 3 is a diagram showing another example of the temperature compensation bias voltage generating circuit in the embodiment of the present invention, and the same portions as those in FIG. 1 are designated by the same reference numerals. In FIG. 3, the oscillation output of the oscillator 3 including the variable capacitance diode 1, the resistor R, and the oscillation circuit 2 is one input of the synchronous detection circuit 31.

Then, the output of the crystal oscillator 32 having an extremely high accuracy is used as the other input of the synchronous detection circuit 31 to perform the synchronous detection. By comparing this detected output with the reference voltage in the comparison circuit 5 and controlling the voltage control voltage source 6 based on the difference, the temperature compensation voltage output of the variable capacitance diodes 7 and 8 can be obtained more accurately and inexpensively. To be

Although the present invention has been described above as using a variable capacitance diode, the present invention can be similarly implemented by using not only a variable capacitance diode but also a voltage control type capacitance.

[0019]

As described above, according to the present invention, the phase characteristic of the directional coupler can be stabilized by providing the temperature compensation bias voltage generating circuit for the variable capacitance diode.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing an example of a temperature compensation bias voltage generation circuit for a variable capacitance diode.

FIG. 3 is a block diagram showing another example of the temperature compensation bias voltage generating circuit.

FIG. 4 is a block diagram showing an example of a conventional phase adjustment circuit for a directional coupler.

[Explanation of symbols]

 1, 7 and 8 Variable capacitance diode 2 Oscillation circuit 3 Oscillator 4 FV conversion circuit 5 Comparison circuit 6 Voltage control voltage source 9, 10 Termination point 11 Directional coupler 12 Output terminal 13 Input terminal 14 Coupling line 15 Voltage mixer 16 Bias voltage regulator

Claims (6)

[Claims] 1. A phase characteristic stabilizing circuit for a directional coupler, comprising: a pair of coupled lines; and a voltage controlled variable capacitance element that is provided between terminal points of the pair of coupled lines and determines a phase characteristic. A phase characteristic stabilizing circuit having compensation voltage generating means for generating a compensation voltage for compensating the temperature characteristic of the variable capacitance element, and supplying the compensation voltage to the variable capacitance element. 2. The compensating voltage generating means includes an oscillating means including a variable capacitance element having the same characteristic as the variable capacitance element, a converting means for converting the oscillation output into a voltage, and the compensating voltage according to the conversion output. The phase characteristic stabilizing circuit according to claim 1, further comprising: a generating unit that generates 3. The phase characteristic stabilizing circuit according to claim 2, wherein the conversion means is a frequency / voltage converter that converts the frequency of the oscillation output into a voltage. 4. The phase characteristic stabilizing circuit according to claim 2, wherein the conversion means includes a crystal oscillator and a detector that synchronously detects the oscillation output by the output of the crystal oscillator. 5. The generating means includes a comparator for comparing a predetermined reference voltage with the converted voltage of the converting means, and the comparison output is used as the compensation voltage.
The phase characteristic stabilizing circuit according to any one of the above. 6. The phase characteristic stabilizing circuit according to claim 1, wherein the variable capacitance element is a variable capacitance diode element.