JPS63232603A - Temperature compensation type piezoelectric oscillator - Google Patents

Abstract

PURPOSE:To simplify the adjustment by constituting a surrounding temperature detector, an analog digital converter, a memory circuit, an analog/digital converter and an active component of a voltage controlled oscillator by one integrated circuit, mounting the integrated circuit on the circuit board and sealing it into an airtight package so as to facilitate the production of temperature compensation voltage. CONSTITUTION:The temperature detector 4, the A/D converter 5, the memory circuit 6, the D/A converter 7 and the active component 8a of the voltage controlled oscillator 8 are integrated to be an integrated circuit. The integrated circuit 9 is mounted on a ceramic board 10 as the circuit board. The ceramic board 10 is sealed via terminals 12, 13 of a base 11 of the airtight package. A digital quantity required for the temperature compensation is stored in advance in the memory circuit 6. As a result, even if there is a difference in the temperature characteristic of each component, since it is not required to use a computer for approximation calculation, the adjustment is facilitated and sure frequency is oscillated stably.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a highly stable oscillator.

[Conventional technology]

Conventionally, crystal oscillators and surface acoustic wave oscillators with high frequency stability have been put into practical use as high-frequency and highly stable carrier wave generation sources and timing signal generation sources for wireless equipment, etc., but in order to further increase frequency stability, requires additional circuitry for temperature compensation. As shown in FIG. 5, in a conventional oscillator, the stabilized output of a reference voltage generator 1 using a constant voltage diode or the like is applied to a voltage controlled oscillator 3 via a compensation network 2 such as a thermistor to determine the frequency temperature. A method to improve the characteristics was put into practical use.

[Problem that the invention seeks to solve]

However, in conventional oscillators, there are manufacturing errors in individual elements such as voltage-controlled variable capacitance elements and temperature variable resistors, so the required temperature compensation voltage differs for each oscillator. In order to adjust this by combining a variable temperature resistor and a fixed resistor, it is necessary to perform approximate calculations using a computer, which has the drawback of requiring a large amount of time and effort in the adjustment process. .

In addition, since the temperature variable resistor and the oscillation element are composed of separate components, there is a difference in the thermal time constant between them, which deteriorates the frequency-temperature characteristics when the ambient temperature is transiently changed. There was also a drawback.

The present invention has been made in view of these points, and its purpose is to provide an oscillator that can easily generate a temperature compensation voltage and that can be easily adjusted.

[Means for solving problems]

In order to achieve such objects, the present invention includes a temperature detector that detects ambient temperature, an analog-to-digital converter that converts the analog output of this temperature sensor into digital code,
A memory circuit that stores a temperature-compensated digital code corresponding to an address specified by the digital code output from this analog-to-digital converter, and converts the temperature-compensated digital code output from this memory circuit into an analog signal. Digital to analog converter and this digital
and a voltage controlled oscillator controlled by the output of the analog converter, the temperature detector, the analog-to-digital converter, the memory circuit, the digital-to-analog converter, and the active elements of the voltage controlled oscillator are configured in one integrated circuit. , this collection-
The integrated circuit is mounted on a circuit board and sealed in an airtight container.

[Effect]

The temperature compensated piezoelectric oscillator according to the present invention is easy to adjust and can stably oscillate at a certain frequency.

〔Example〕

FIG. 1 is a system diagram showing an embodiment of a temperature compensated piezoelectric oscillator according to the present invention. In FIG. 1, 4 is a temperature detector, 5 is an analog-to-digital converter, 6 is a memory circuit,
7 is a digital-to-analog converter, and 8 is a voltage controlled oscillator having an active element 8a and a crystal oscillator 8b.

The operation of the oscillator configured in this way will be explained.

The ambient temperature is detected by a temperature detector 4, and the analog output of the temperature detector 4 is supplied to an analog-to-digital converter 5, where it is digitally coded and supplied to a memory circuit 6.

The memory circuit 6 is provided with an analog temperature address signal to compensate for the frequency-temperature characteristics of the voltage controlled oscillator 8.
A temperature compensation digital code corresponding to the digital code of the digital converter 5 is stored in advance. As the ambient temperature changes, the temperature address signal also changes, and the temperature compensated digital code changes accordingly.

This temperature compensated digital code is read out from the memory circuit 6. The read temperature compensated digital code is supplied to the digital-to-analog converter 7, converted into an analog signal, and supplied to the voltage controlled oscillator 8.

FIG. 2 is a structural diagram of the temperature compensated piezoelectric oscillator of FIG. 1. In FIG. 2, reference numeral 9 indicates a temperature detector 4, an analog/digital converter 5. Memory circuit 6 is an integrated circuit in which active elements 8a of a digital-to-analog converter 7 and a voltage-controlled oscillator 8 are combined into one, and this integrated circuit 9 is mounted on a ceramic substrate 10 as a circuit board. Further, the ceramic substrate 10 is connected to the terminals 12 and 13 of the base 11 of the airtight container.
It is enclosed through. Integrated circuit 9 and crystal oscillator 8b
The voltage controlled oscillator 8 including the oscillator 8 is hermetically sealed by the base 11 of the airtight container and the cap 14 of the airtight container in order to ensure reliability and eliminate temperature differences.

FIG. 3 shows another embodiment of the airtight container. In FIG. 3, reference numeral 15 is a window through which ultraviolet light passes, as indicated by an arrow 16, and in this figure, the same or equivalent parts as in FIG. 2 are given the same reference numerals. Due to the ultraviolet vA16 transmitted through the window 15,
The memory contents of the memory circuit 6 can be erased. In this case, the memory of the memory circuit 6 may be an electrically writable element that can be erased by ultraviolet light.

In the above embodiment, the oscillation element of the voltage controlled oscillator 8 is a crystal oscillator, but it may be a surface acoustic wave element.

Further, although the circuit board is a ceramic board, it may be a printed board. Furthermore, the material of the airtight container includes, for example, metal, ceramic or glass. Further, as the memory element of the memory circuit, in addition to the above-mentioned electrically writable/ultraviolet erasable element, there are other electrically writable/electrically erasable elements.

FIG. 4 is a graph showing the characteristics before and after temperature compensation. In the figure, a curve S1 shows the frequency-temperature characteristics of the oscillator before compensation, and a curve S2 shows the frequency-temperature characteristics of the oscillator after compensation. In this way, a highly stable temperature compensated piezoelectric oscillator can be realized.

〔Effect of the invention〕

As explained above, the present invention combines a temperature detector and an analog
The digital converter, memory circuit, digital-to-analog converter, and voltage-controlled oscillator active elements are configured in one integrated circuit, and this integrated circuit is mounted on a circuit board and sealed in an airtight container, which is necessary for temperature compensation. By storing digital quantities in the memory circuit in advance (this eliminates the need for approximation calculations using a computer etc. even if there are differences in the temperature characteristics of individual components, it is easy to make adjustments and it is possible to obtain accurate frequencies). This has the effect of allowing stable oscillation.Also, if the integrated circuit with temperature compensation function and the oscillation element of the voltage controlled oscillator are sealed in the same airtight container, an oscillator with even higher reliability can be obtained. be.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing one embodiment of the temperature compensated piezoelectric oscillator according to the present invention, FIG. 2 is a structural diagram thereof, FIG. 3 is a structural diagram showing another embodiment of the airtight container, and FIG. A graph showing a comparison before and after compensation, and FIG. 5 is a system diagram showing a conventional temperature compensated piezoelectric oscillator. 4... Temperature detector, 5... Analog/digital converter, 6... Memory circuit, 7... Digital/analog converter, 8... Voltage controlled oscillator, 8a... Voltage controlled oscillator 8b... Crystal oscillator, 9... Integrated circuit, 10... Ceramic substrate, 11... Base of airtight container, 12. 13... Terminal, 14... Airtight container cap.

Claims (2)

[Claims] (1) A temperature detector that detects the ambient temperature, an analog/digital converter that converts the analog output of this temperature sensor into a digital code, and an address specified by the digital code output from this analog/digital converter. a memory circuit that stores a corresponding temperature-compensated digital code; a digital-to-analog converter that converts the temperature-compensated digital code output from the memory circuit into an analog signal;
and a voltage controlled oscillator controlled by the output of the digital to analog converter, the temperature sensor and the analog
The digital converter, the memory circuit, the digital-to-analog converter, and the active elements of the voltage-controlled oscillator are composed of one integrated circuit, and the integrated circuit is mounted on a circuit board and sealed in an airtight container. Temperature compensated piezoelectric oscillator. (2) The temperature compensated piezoelectric oscillator according to claim 1, wherein the airtight container has a window through which ultraviolet rays pass.