JP2000209030A - Oscillation circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize the oscillation frequency of an oscillation circuit which is using a crystal vibrator, etc., in terms of temperature, etc. SOLUTION: A resistor R1 is connected in series to a crystal vibrator X and a resistor R2 is connected in parallel to the vibrator X respectively. At the same time, a capacitor C2 is connected in series to the vibrator X to properly suppress the exciting level of the vibrator X and also to turn the oscillation frequency characteristic into a smooth tertiary curve corresponding to the temperature of the signal that is amplified by a transistor Q11 and outputted from an emitter. Thus, the temperature compensation is facilitated. Meanwhile, the power voltage supplied to an oscillation circuit of a microwave band, etc., using a dielectric resonator is varied by a temperature compensation circuit according to the temperatures to stabilize the oscillation frequency in regard to the temperature. In regard to the humidity, the relative humidity is detected by a humidity detection circuit. Then the temperature compensation circuit generates the control voltage in response to the relative humidity and controls the oscillation circuit to stabilize the oscillation frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oscillating circuit, and more particularly, to an oscillating circuit using a crystal resonator or a dielectric resonator, which improves the frequency stability with respect to a change in temperature or humidity.

[0002]

2. Description of the Related Art A crystal oscillator or a dielectric resonator is used in an oscillation circuit in order to obtain high oscillation frequency stability. FIG. 2 shows an equivalent circuit of a crystal oscillator. In an oscillation circuit using a crystal oscillator, stable oscillation can be obtained by sufficiently increasing the negative resistance of the oscillation circuit with respect to the equivalent series resistance R. However, if the excitation level of the crystal resonator becomes too high, the oscillation frequency characteristic with respect to temperature deviates from a cubic curve in a high temperature region as shown in FIG. Difficulties arise in some cases.

A dielectric resonator is often used for a local oscillation circuit in a microwave band, and the frequency characteristic of an oscillation circuit using the dielectric resonator with respect to temperature is quadratic as shown in FIG. Shows the characteristics of the shape. This characteristic allows the slope of the quadratic curve to rise to the right or to the left by selecting the material of the dielectric resonator or the like, but the quadratic curve cannot be changed to a straight line. Further, the frequency characteristic with respect to the relative humidity has a characteristic that the frequency decreases as the relative humidity increases as shown in FIG.

[0004]

SUMMARY OF THE INVENTION In view of the foregoing, the present invention provides an oscillation circuit using a crystal oscillator, in which the excitation level of the crystal oscillator is suppressed to an appropriate level, and the oscillation frequency characteristic with respect to temperature changes. Is a simple cubic curve to enable temperature compensation.In the case of an oscillator circuit using a dielectric resonator, the voltage supplied to the oscillator circuit has temperature characteristics to stabilize the oscillation frequency. With respect to humidity, an object is to change the control voltage applied to the oscillation circuit in accordance with the relative humidity, and to stabilize the oscillation frequency against environmental changes.

[0005]

In order to achieve the above object, in an oscillation circuit according to the present invention, one terminal of a crystal oscillator is connected to the base of a transistor, and the other terminal is grounded via a load capacitor. In the oscillation circuit, means for limiting the excitation level of the crystal resonator is provided to facilitate compensating the temperature characteristics of the oscillation frequency.

The means for limiting the excitation level of the crystal unit is such that a first resistor is connected in series with the crystal unit.

Alternatively, it is assumed that a second resistor is connected in parallel with the quartz oscillator.

Alternatively, it is assumed that a capacitor is connected in series between one terminal of the crystal unit and the base of the transistor.

Further, in an oscillation circuit using a dielectric resonator, a voltage from the power supply circuit is varied between the power supply circuit for supplying power to the oscillation circuit and the oscillation circuit in accordance with the ambient temperature. A temperature compensating circuit for supplying and varying the oscillation frequency is provided so as to suppress the fluctuation of the oscillation frequency when the temperature changes.

In this temperature compensation circuit, a voltage from a power supply circuit is input to an emitter, a PNP transistor that outputs from a collector to an oscillation circuit, a collector is connected to the base of the PNP transistor, and the base is connected to a first thermistor and a first thermistor. It is connected to the collector of a PNP transistor via a parallel circuit of three resistors, connected to ground via a series circuit of a second thermistor and a fourth resistor, and has an emitter connected to the fifth.
N connected to ground via a resistor and to the collector of a PNP transistor via a Zener diode
And a PN-type transistor. Note that a sixth resistor may be connected in series with a parallel circuit of the first thermistor and the third resistor.

An oscillation circuit using a dielectric resonator includes:
A humidity detection circuit for detecting relative humidity, and a control voltage generation circuit for generating a control voltage according to a signal from the humidity detection circuit and controlling the oscillation frequency by applying the control voltage to an oscillation circuit are provided. It is configured to suppress the fluctuation of the oscillation frequency.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described based on embodiments with reference to the drawings. FIG. 1 is a block diagram of a main part of an embodiment of an oscillator circuit according to the present invention. (A) is an example of an oscillator circuit using a crystal oscillator, and (B) and (C) are other examples of a crystal oscillator circuit portion. FIG. 2 is an equivalent circuit diagram of the crystal unit, and FIG. 3 is a diagram showing the relationship between the excitation level of the crystal unit and the frequency characteristics. In FIG. 1, reference numerals 1, 1 'and 1 "denote crystal oscillator circuits, respectively, where X is a crystal oscillator, C1 is a load capacitance, and R1 is a first crystal oscillator.
A resistor, R2 is a second resistor, and C2 is a capacitor. Q11
Is an emitter-follower-connected transistor (NPN type) constituting an oscillation circuit. A base bias voltage is applied by a resistor R11 and a resistor R12. Bias capacitances (capacitors) C11 and C12 are determined in accordance with the transistor Q11.
The power is amplified and an oscillation signal is output via the resistor R13 of the emitter circuit.

The oscillation frequency of the crystal unit X is determined by the load capacitance C1. In this oscillation circuit, stable oscillation can be obtained by setting the negative resistance of the circuit sufficiently large with respect to the equivalent series resistance R of the crystal unit X. This is achieved by simultaneously increasing the excitation capability of the crystal unit X. Yes, the excitation level increases. However, when the excitation level of the crystal unit X becomes excessive, the oscillation frequency characteristic in the high temperature region deviates from the cubic curve as shown in FIG. It is extremely difficult to do so. Therefore, means for appropriately restricting the excitation level of the crystal unit X is provided, and the characteristic of the oscillation frequency with respect to the temperature is set as a cubic curve that smoothly changes as shown in FIG. The crystal oscillator circuit 1 of FIG. 1A has an example in which a first resistor R1 is inserted in series with a crystal oscillator X (first
It is also possible to insert the resistor R1 on the load capacitance C1 side),
The crystal oscillator circuit 1 'of (b) is an example in which the second resistor R2 is connected in parallel to the crystal oscillator X, and the crystal oscillator circuit 1''of (c).
Is an example in which a capacitor C2 is interposed in series with a crystal unit X. With these, the power consumption (excitation energy) of the crystal unit X is divided and consumed by these interposed resistors or capacitors. The excitation level of X is appropriately restricted, and the temperature characteristic of the oscillation frequency becomes a cubic curve that changes smoothly, so that temperature compensation can be easily performed.

FIG. 4 is a block diagram of a main part of another embodiment of an oscillation circuit according to the present invention and an example of a temperature compensation circuit. Reference numeral 21 denotes a power supply circuit, 22 denotes a temperature compensation circuit, and 23 denotes a dielectric resonator. This is an oscillation circuit used for a local oscillation circuit in the microwave band. As shown in FIG. 5 (b), the oscillation frequency of the oscillation circuit 23 peaks in the middle temperature range (20 ° C. to 25 ° C.) and decreases in both the high temperature range and the low temperature range. ). Incidentally, the oscillation circuit 23 has a characteristic that the oscillation frequency increases as the power supply voltage increases, as shown in FIG. Therefore, the temperature compensation circuit 22 outputs the voltage Vi from the power supply circuit 21 so as to be low in the middle temperature range (20 ° C. to 25 ° C.) and high in the high temperature range and the low temperature range (U-shaped). The voltage Vo has a temperature characteristic and is supplied to the oscillation circuit 23. Thereby, the frequency characteristic of FIG. 5B becomes substantially flat (linear) with respect to the temperature change, and the fluctuation of the oscillation frequency is suppressed.

The temperature compensating circuit 22 is provided with a voltage from the power supply circuit 21.
Vi is input to the emitter of the PNP transistor Q21, a voltage Vo is output from the collector to the oscillation circuit 23, the collector of the NPN transistor Q22 is connected to the base of the PNP transistor Q21, and the base of the NPN transistor Q22 is the first. It is connected to the output voltage Vo terminal (collector of the PNP transistor Q21) through a parallel circuit of the thermistor Th21 and the third resistor R21, and the second thermistor Th22 and the fourth resistor
R22 is connected to ground via a series circuit, the emitter is connected to the output voltage Vo terminal via a zener diode Dz, and is connected to ground via a fifth resistor R23. Third resistor R2
Numeral 1 is for reducing the temperature change of the resistance value of the first thermistor Th21, and the fourth resistor R22 is composed of two thermistor circuits (a parallel circuit of the first thermistor Th21 and the third resistor R21 and a second thermistor circuit). Series circuit of Th22 and fourth resistor R22)
To adjust the voltage branching ratio at the connection point.
The voltage at the connection point of the two thermistor circuits, that is, the branch ratio of the output voltage Vo changes with temperature.
Although this becomes the base voltage of the N-type transistor Q22, the emitter voltage (reference voltage) is linked to the output voltage Vo, so that the temperature of the bias voltage of the NPN-type transistor Q22 depends on the appropriate selection of each element of the two thermistor circuits. , The temperature of the base current of the PNP transistor Q21 can be made temperature dependent, and the output voltage Vo can have the above-mentioned U-shaped temperature characteristic. The first thermistor
By connecting the sixth resistor in series to the parallel circuit of Th21 and the third resistor R21, the temperature compensation accuracy can be increased by appropriately selecting the sixth resistor.

FIG. 6 is a block diagram showing a main part of another embodiment of the oscillation circuit according to the present invention.
Reference numeral 33 denotes a control voltage generation circuit, and reference numeral 33 denotes an oscillation circuit used for a local oscillation circuit in a microwave band using a dielectric resonator. For example, the humidity detecting circuit 31 has a structure in which a conductive surface adsorption layer pattern is formed on a thin film of a styrene copolymer, and the surroundings are surrounded by a non-conductive substance. A humidity sensor that utilizes the point at which the temperature decreases is used. The humidity sensor outputs an AC voltage to the conductive surface adsorption layer by applying an AC voltage to the conductive surface attraction layer through an appropriate resistor, because the voltage between both ends of the resistor increases due to an increase in relative humidity. That is, as shown in FIG. 7 (a), the output voltage (signal level) of the humidity detection circuit 31 increases as the relative humidity increases. The control voltage output from the control voltage generation circuit 32 increases when the signal level from the humidity detection circuit 31 increases. The oscillation circuit 33
As shown in FIG. 7B, when the relative humidity increases, the oscillation frequency decreases. As shown in FIG. 7C, when the control voltage increases, the oscillation frequency increases. That is, according to the configuration of the block diagram shown in FIG.
Rises, the control voltage output from the control voltage generation circuit 32 rises, and the oscillation frequency of the oscillation circuit 33 rises, that is, the oscillation frequency of the oscillation circuit 33 that has fallen due to the rise in relative humidity is Reduction is suppressed and stabilized.

[0017]

As described above, according to the oscillation circuit according to the present invention, in the case of using the crystal oscillator, the excitation level of the crystal oscillator is suppressed to an appropriate level, and the oscillation frequency is changed with respect to temperature change. Since the characteristic is a straight cubic curve, temperature compensation can be easily performed,
In the case of using a dielectric resonator, with respect to temperature, the voltage supplied to the oscillation circuit is varied according to a temperature change by a temperature compensation circuit to control the oscillation frequency of the oscillation circuit. In order to stabilize the oscillation frequency, the control voltage applied to the oscillation circuit is varied according to the relative humidity.When the oscillation frequency is used for a local oscillation circuit in a microwave band, etc., the local oscillation frequency is changed with respect to changes in temperature or relative humidity. And can be stabilized.

[Brief description of the drawings]

FIG. 1 is a block diagram of a main part of an embodiment of an oscillation circuit according to the present invention.

FIG. 2 is an equivalent circuit of a crystal resonator.

FIG. 3 is a diagram illustrating a relationship between an excitation level of a crystal resonator and frequency characteristics.

FIG. 4 is a main part block diagram of another embodiment of the oscillation circuit according to the present invention and an example of a temperature compensation circuit.

5 is an oscillation frequency characteristic of the oscillation circuit of FIG. 4 with respect to voltage and temperature.

FIG. 6 is a main part block diagram of another embodiment of the oscillation circuit according to the present invention.

FIG. 7 is a graph showing an oscillating frequency characteristic of the oscillation circuit of FIG.

[Explanation of symbols]

 1, 1 ', 1 "crystal resonator circuit X crystal resonator C1 load capacitance R1, R2 first and second resistors C2 capacitor Q11 transistor (NPN type) R11 to R13 resistors C11, C12 capacitor R Equivalent series resistance C Equivalent series capacitance of crystal unit L Equivalent series wire of crystal unit Co Equivalent parallel capacitance of crystal unit 21 Power supply circuit 22 Temperature compensation circuit 23, 33 Oscillation circuit 31 Humidity detection circuit 32 Control voltage generation circuit Q21 PNP transistor Q22 NPN transistor Dz Zener diode Th21, Th22 First and second thermistors R21 to R23 Third to fifth resistors

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5J079 AA04 BA02 BA32 CB02 DA00 FA12 FA14 FA21 FB11 GA02 GA15 5J081 AA03 CC17 CC23 DD03 DD26 EE05 FF17 FF19 FF23 GG01 HH06 KK02 KK03 KK12 KK22 LL01 KK01 KK01 KK01 KK01 KK01 KK01 LL01

Claims (8)

[Claims] 1. An oscillation circuit in which one terminal of a crystal unit is connected to a base of a transistor and the other terminal is grounded via a load capacitor, means for limiting an excitation level of the crystal unit is provided. An oscillation circuit that facilitates compensating for the temperature characteristics of the oscillation frequency. 2. The oscillation circuit according to claim 1, wherein the excitation level limiting means of the crystal unit is configured by connecting a first resistor in series with the crystal unit. 3. The oscillation circuit according to claim 1, wherein said excitation level limiting means of said crystal unit is connected to a second resistor in parallel with said crystal unit. 4. The oscillation circuit according to claim 1, wherein the excitation level limiting means of the crystal unit is configured by connecting a capacitor in series between one terminal of the crystal unit and a base of the transistor. 5. An oscillation circuit using a dielectric resonator, wherein the voltage from the power supply circuit is varied between the power supply circuit for supplying power to the oscillation circuit and the oscillation circuit in accordance with the ambient temperature. An oscillation circuit provided with a temperature compensating circuit for varying the oscillation frequency by supplying the oscillation frequency to the oscillation circuit to suppress the variation of the oscillation frequency when the temperature changes. 6. A temperature compensating circuit, comprising: a PNP transistor that inputs a voltage from the power supply circuit to an emitter and outputs a voltage from a collector to the oscillation circuit; a collector connected to a base of the PNP transistor; The PNP through a parallel circuit of a first thermistor and a third resistor
The PNP transistor is connected to the collector of the PNP transistor via a series circuit of a second thermistor and a fourth resistor, to the ground via a fifth resistor, and to the ground via a Zener diode. 6. The oscillation circuit according to claim 5, comprising an NPN-type transistor connected to the collector. 7. The oscillation circuit according to claim 6, wherein a sixth resistor is connected in series to the parallel circuit of the first thermistor and the third resistor. 8. An oscillating circuit using a dielectric resonator generates a humidity detecting circuit for detecting relative humidity and a control voltage corresponding to a signal from the humidity detecting circuit, and applies the control voltage to the oscillating circuit to reduce the oscillating frequency. An oscillation circuit provided with a control voltage generation circuit for controlling the oscillation frequency when the relative humidity changes.