JPH09270637A - Digital temperature compensation piezoelectric oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily adjust a frequency of the digital temperature compensation piezoelectric oscillator without giving adverse effect onto a temperature characteristic and a control characteristic. SOLUTION: In order to solve problems, an oscillated frequency in relation to a variable capacitance diode being a frequency variable element is not adjusted nor corrected, a digital adder circuit 4 is provided between a 1st memory circuit 3 and a 2nd memory circuit 5 as a means to adjust and to vary the oscillated frequency and the frequency is adjusted to give an offset signal required for the frequency adjustment from an offset setting circuit 8 to the digital adder circuit 4.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a technique for offsetting an oscillation frequency of a digital temperature compensation oscillator.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 4, a temperature detection circuit 1, a first analog-digital conversion circuit 2 for digitizing an analog output of the temperature detection circuit 1, and a first analog-digital conversion circuit 2 are used. A first memory circuit 3 that stores temperature compensation data corresponding to an address designated by the output digital signal, and a second memory circuit 3 that stores control compensation data corresponding to the address designated by the digital signal of the first memory circuit 3. A memory circuit 5, a digital-analog conversion circuit 6 for converting a digital signal output from the second memory circuit 5 into an analog signal, and a voltage-controlled piezoelectric oscillation circuit 7 controlled by the output of the digital-analog conversion circuit 6. It had been.

[0003]

However, in this configuration, the load capacitance of the voltage-controlled piezoelectric oscillation circuit 7 is basically used when the frequency is adjusted to the reference frequency and when the time-dependent change of the frequency is corrected. The fixed capacitance or the variable capacitance diode used for the adjustment of the variable capacitance diode normally used as the oscillation frequency variable element of the voltage controlled piezoelectric oscillation circuit 7 is used as the location for adjusting the frequency. However, the control compensation data used to correct the non-linearity of the varactor diode is changed, and the linearity becomes worse. There was a problem that rewriting had to be performed.

[0004]

[Means for Solving the Problems] To solve the problems,
The first memory circuit 3 is used as a means for adjusting and varying the oscillation frequency without adjusting or compensating the oscillation frequency in relation to the variable capacitance diode which is the frequency variable element.
The digital adder circuit 4 is provided between the second memory circuit 5 and the frequency can be adjusted by inputting an offset signal of an amount required for frequency adjustment from the offset setting circuit 8 to the digital adder circuit 4. Solved the problem.

[0005]

1 is a system diagram showing a digital temperature compensation piezoelectric oscillator according to an embodiment of the present invention. The output as the temperature information detected by the temperature detection circuit 1 is input to the first analog-digital conversion circuit 2 for converting an analog signal into a digital signal. The output of the first analog-digital conversion circuit 2 is the first
The temperature compensation data corresponding to the address designated by the digital signal as the output of the analog-to-digital conversion circuit 2 is input as the address of the first memory circuit 3 for storing or reading.

The first memory circuit 3 reads and outputs the temperature compensation data stored in advance corresponding to the address designated by the digital signal as the output of the first analog-digital conversion circuit 2. The output of the first memory circuit 3 is input as one of the digital adder circuits 4, and the output of the offset setting circuit 8 for frequency adjustment is used as the other input to perform addition.

By changing the output signal of the offset setting circuit 8, the output signal of the digital adding circuit 4 can be changed, and as a result, the frequency can be adjusted or corrected. The output signal of the digital adder circuit 4 is supplied to the second memory circuit 5. It is input as an address of the second memory circuit 5 for storing and reading the control compensation data corresponding to the address designated by the digital signal as the output of the digital adding circuit 4.

The second memory circuit 5 includes a digital adder circuit 4
The control compensation data stored in advance corresponding to the address designated by the digital signal as the output of is read and output. The output of the second memory circuit 5 is digital
It is supplied to the analog conversion circuit 6. The digital-analog conversion circuit 6 converts the digital output signal of the second memory circuit 5 into an analog signal and outputs the analog signal.

The analog signal output of the digital-analog converter circuit 6 is supplied to a voltage controlled piezoelectric oscillator circuit 7 whose oscillation frequency is controlled by a control voltage. As a result, the first
The temperature compensation data stored in the memory circuit 3 and the second
The oscillation frequency of the voltage-controlled piezoelectric oscillation circuit 7 is controlled by the control compensation data stored in the memory circuit 5, and a piezoelectric oscillator whose oscillation frequency is temperature-compensated digitally is obtained.

FIG. 2 is a system diagram showing the offset setting circuit 8 according to the embodiment of the present invention. FIG. 2A shows the simplest circuit. The offset setting circuit 8 finely adjusts the frequency and corrects the frequency change over time, and normally does not change much. Therefore, an embodiment has been shown in which a digital code is set by the digital switch circuit 9 such as a DIP switch or a rotary code switch and is supplied to the digital adder circuit 4.

In FIG. 2B, an offset voltage is generated and the offset voltage is supplied to the second analog-digital conversion circuit 10. The second analog-digital conversion circuit 10 converts the offset voltage into a digital code. An embodiment has been shown in which the converted signal is supplied to the digital adder circuit 4.

FIG. 3 is a graph showing an example of the relationship between the control voltage and the oscillation frequency according to the embodiment of the present invention. In FIG. 3, the control voltage is V on the straight line of the initial characteristic with V0 as the center.
When changing to 1, V2, the frequency f
It changes to 1, f2. When f0 is deviated after the elapse of time, when the control voltage is moved by ΔVa by the offset setting circuit to adjust the frequency again to f0, V0a = V
Centered on 0 + ΔVa, V1a = V1 + ΔVa, V2
a = V2 + ΔVAa, the control voltage-oscillation frequency characteristic changes by ΔVa compared to the initial characteristic, but the frequencies at that time are f0, f1, f2,
Changes in the same way as.

This is because the adjustment by the offset setting as described above is performed by linearly compensating the control voltage and the oscillation frequency which are originally non-linear by the control compensation data. Further, in the graph of FIG. 3, the voltages are greatly shifted for the sake of explanation, but in reality, ΔVa is for frequency adjustment and is a very slight voltage.

[0013]

According to the present invention, the frequency adjustment of the digital temperature-compensated piezoelectric oscillator can be performed very easily without adversely affecting the frequency temperature characteristic and the control characteristic. Even in manufacturing, we were able to significantly reduce the number of processes, improve quality, stabilize accuracy, and improve yield.

[Brief description of drawings]

FIG. 1 is a system diagram showing a digital temperature compensation piezoelectric oscillator according to an embodiment of the present invention.

FIG. 2 is a system diagram showing an embodiment of an offset setting part of the present invention.

FIG. 3 is a graph of an example showing the relationship between the oscillation frequency and the control voltage of the present invention.

FIG. 4 is a system diagram showing a digital temperature-compensated piezoelectric oscillator according to an embodiment of the prior art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Temperature detection circuit 2 1st analog / digital conversion circuit 3 1st memory circuit 4 Digital addition circuit 5 2nd memory circuit 6 Digital / analog conversion circuit 7 Voltage control piezoelectric oscillation circuit 8 Offset setting circuit 9 Digital switch circuit 10 2nd Analog-digital conversion circuit

Claims (3)

[Claims] 1. A temperature detection circuit, a first analog-digital conversion circuit for digitizing an analog output of the temperature detection circuit, and an address designated by a digital signal output from the first analog-digital conversion circuit. A first memory circuit for storing temperature compensation data corresponding to
A second memory circuit that stores control compensation data corresponding to an address specified by a digital signal output from the memory circuit, and a digital-analog conversion circuit that converts the digital signal output from the second memory circuit into an analog signal And a voltage-controlled piezoelectric oscillation circuit controlled by the output of the digital-analog conversion circuit, wherein a digital addition circuit is connected between the first memory circuit and the second memory circuit. A digital temperature compensation piezoelectric oscillator, wherein an offset setting circuit is connected to the digital addition circuit. 2. The digital temperature-compensated piezoelectric oscillator according to claim 1, wherein the offset setting circuit is composed of a digital switch circuit. 3. The offset setting circuit is configured by inputting a variable offset voltage to a second analog-digital conversion circuit and by a digital output of the second analog-digital conversion circuit. A digital temperature-compensated piezoelectric oscillator according to.