A Step Temperature Compensation Method for Crystal Oscillator

Abstract

The invention discloses a step temperature compensation method of a crystal oscillator adopting a closed-loop feedback compensation framework. First, determine the target frequency f 0 Corresponding binary code B 0i , and stored in the single-chip microcomputer; when the temperature changes, the signal with the modulus frequency f(T) is sent to the analog-to-digital converter and converted into the corresponding binary code B 1i , and input to the microcontroller with the target frequency f 0 binary code B 0i For comparison, set the threshold range ΔB in the microcontroller, and set B 0i and B 1i After the comparison, judge the comparison result B 0i -B 1i is within the threshold range. If B 0i -B 1i Not within the threshold, code B in stepped binary 2i Make compensation, and send it to the microcontroller again after compensation and B 0i Perform a comparison, and perform circular compensation in this way until the comparison result B 0i -B 1i Within the threshold range, temperature compensation is finally achieved. Compared with the existing temperature-compensated crystal oscillator, the present invention does not need a temperature sensor, thus overcoming the temperature hysteresis problem in the existing TCXO caused by the asynchronous temperature change of the temperature sensor and crystal resonator chip.

Description

technical field [0001] The invention belongs to the technical field of crystal oscillators, and more specifically relates to a step temperature compensation method for crystal oscillators. Background technique [0002] Temperature Compensated Crystal Oscillator (TCXO, Temperature Compensate Xtal (crystal) Oscillator) is a kind of crystal oscillator that can work in a wide temperature range and maintain the output frequency of the crystal oscillator within a certain accuracy range (10 -6 ~10 -7 order of magnitude) crystal oscillator. It has the characteristics of low power, can work immediately after starting up, and has high stability. It is widely used in various communications, navigation, radar, satellite positioning systems, mobile communications, program-controlled telephone exchanges, and various electronic measuring instruments. [0003] The existing temperature-compensated crystal oscillator is essentially a voltage-controlled crystal oscillator (Voltage Controlled...

AI Technical Summary

Problems solved by technology

This method has advantages in phase noise characteristics when realizing high-frequency temperature-compensated crystal oscillators (TCXO), but the composition is relatively complicated and has not been widely used yet.

[0016] In summary, the existing temperature compensation methods for crystal oscillators all adopt an open-loop compensation framework, and a temperature sensor is used. The temperature sensor is as close as possible to the crystal resonator on the circuit, and the resonator chip of the crystal resonator It is packaged separately in a closed space, which inevitably produces a temperature hysteresis between the temperature sensor and the resonant chip, resulting in a failure to achieve a breakthrough in the frequency-temperature characteristics of the temperature-compensated crystal oscillator, that is, the TCXO.

Especially for crystal oscillators whose output signals are high frequency, this temperature hysteresis problem is more serious, and the compensation accuracy is limited

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