JPS63275211A - Piezo-oscillator - Google Patents

Abstract

PURPOSE:To enable the automatic correction of a frequency secular change characteristic by measuring elapsed time, and generating a correction voltage by a digital-analog converter when it comes to the previously get time, and supplying the said correction voltage to a voltage control piezo-oscillator. CONSTITUTION:The output of a clock oscillator 1 for measuring time is supplied to a counter 2, and an elapsed time signal is fetched from the output Q of the counter 2. Then, the address input of a memory circuit 3 is connected to this output Q of the counter 2, and a previously set correction digital code is fetched from the memory circuit 3 according to the output Q of the counter 2. Next, this output of the memory circuit 3 is supplied to a digital-analog converter 4, and the correction voltage is generated. Then, this correction voltage is supplied to the voltage controlled piezo-oscillator 7, and the change of an oscillation frequency characteristic due to the secular change is corrected. Thus, the frequency secular change can be automatically corrected, and the maintenance of the piezo-oscillator comes unnecessary.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a highly stable piezoelectric oscillator, and particularly to a piezoelectric oscillator that can automatically correct changes in frequency over time.

[Conventional technology]

Conventionally, crystal oscillators with high frequency stability and elastic surface ° wave oscillators have been put into practical use as high-frequency and highly stable carrier wave generation sources and timing signal generation sources for wireless equipment,6 but In order to increase the frequency, it is necessary to correct the frequency change over time.

An example of a conventional piezoelectric oscillator is shown in FIG. 3 and will be described.

In the figure, 18 is an oscillation transistor, the collector of which is connected to a power supply terminal 21, and the emitter is grounded through a resistor 19 and connected to an output terminal 22 through a capacitor 2.0. . The base of the transistor 18 is grounded through the piezoelectric oscillator 13 and the variable capacitor 11 connected in series, and the capacitor 12 is connected in parallel to the variable capacitor 11. Furthermore, the connection point between the piezoelectric oscillator 13 and the base of the transistor 1B is connected to the power supply terminal 21 via a resistor 14 and grounded via a resistor 15, and is further grounded via capacitors 16 and 17 in series. , this capacitor 1
The connection point 6.17 is connected to the emitter of the transistor 18 and the connection point between the resistor 19 and the capacitor 20.

In the piezoelectric oscillator configured in this manner, changes in frequency over time have been corrected by periodically adjusting the variable capacitor 12 or the like.

[Problem that the invention seeks to solve]

The conventional piezoelectric oscillator described above has a problem in that in order to correct the frequency change over time, adjustment must be periodically performed using a variable capacitor built into the piezoelectric oscillator.

[Means for solving problems]

The piezoelectric oscillator of the present invention includes a clock oscillator for time measurement,
a counter that takes the output of this clock oscillator as input and measures elapsed time; a memory circuit that stores a time-varying digital code corresponding to an address specified by the output digital code of the counter; It is constructed of a digital-to-analog converter that converts a code into an analog signal, and a voltage-controlled piezoelectric oscillator that is controlled by the output of this digital-to-analog converter.

[Effect]

In the present invention, a counter measures the elapsed time, and when a preset time is reached, a digital-to-analog converter generates a correction voltage, and this correction voltage is supplied to a voltage-controlled piezoelectric oscillator to measure the frequency change characteristics over time. Correct automatically.

〔Example〕

Embodiments of the present invention will be described in detail below based on the drawings.

FIG. 1 is a block diagram showing an embodiment of a piezoelectric oscillator according to the present invention.

In the figure, 1 is a clock oscillator for time measurement, 2 is a counter that takes the output of this clock oscillator 1 as input and measures elapsed time, and 3 is a time-varying digital code corresponding to the address specified by the output digital code of this counter 2. 4 is a digital-to-analog converter that converts the output digital code of the memory circuit 3 into an analog signal; 5 is a battery that supplies power to each of these parts;
These constitute the temporal change correction section 6. T is a voltage-controlled piezoelectric oscillator which is controlled by the output of the digital-to-analog converter 4, and 8 is an output terminal from which the output of the voltage-controlled piezoelectric oscillator 7 is obtained.

Next, the operation of the embodiment shown in FIG. 1 will be explained.

First, the output of the clock oscillator 1 for time measurement is sent to the counter 2.
and extracts the elapsed time signal from the Q output of the counter 2. The address switch of the main circuit 3 is connected to the Q output of the counter 2, and a preset correction digital code is taken out from the memory circuit 3 in accordance with the Q output of the counter 2.

Next, the output of this memory circuit 3 is supplied to a digital-to-analog converter 4, which generates a correction voltage of 0 and 1. This correction voltage is supplied to a voltage-controlled piezoelectric oscillator 7, which corrects the oscillation frequency characteristics due to changes over time. .

Here, the temporal change correction unit 6 other than the voltage controlled piezoelectric oscillator 7
is constantly operated by battery 5.

FIG. 2 is a diagram showing an example of frequency change characteristics over time to explain the operation of FIG. 1, with the curve a before compensation and the curve a after compensation.

In this way, by predicting the frequency change characteristics over time of the voltage-controlled piezoelectric oscillator 7 in advance and storing them in the memory circuit 3, a highly stable piezoelectric oscillator can be realized.

The frequency change characteristics of the voltage controlled piezoelectric oscillator T over time are as follows:
A similar tendency occurs when the oscillators used are manufactured using the same manufacturing method.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to automatically correct changes in frequency over time, so there is no need for maintenance of the piezoelectric oscillator, and there is also an effect that the present invention is superior to the conventional method in terms of performance. There is.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a block diagram showing an embodiment of the piezoelectric oscillator according to the present invention, FIG. 2 is a diagram showing an example of frequency change characteristics over time to explain the operation of FIG. 1, and FIG. 1 is a circuit diagram showing an example of a conventional piezoelectric oscillator. 3. Memory circuit, 4. Digital-to-analog converter, 7. Voltage controlled piezoelectric oscillator.

Claims (1)

[Claims] A clock oscillator for time measurement, a counter that uses the output of this clock oscillator as input and measures elapsed time, a memory circuit that stores a time-varying digital code corresponding to an address specified by the output digital code of this counter, and this memory. A digital-to-analog converter that converts the output digital code of the circuit into an analog signal, and this digital
A piezoelectric oscillator comprising a voltage-controlled piezoelectric oscillator controlled by the output of an analog converter.