Crystal Oscillator Temperature Control Using Frequency Difference Detection
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Solution Overview
Problem
Conventional oven controlled crystal oscillators (OCXO) face challenges in maintaining temperature control within ±20 m° C due to individual variation and long-term changes in analog parts, making it difficult to achieve high frequency stability, especially in applications like base stations and relay stations.
Innovation Solution
A crystal controlled oscillator system that includes two oscillator circuits, a heating unit, a pulse generator, a frequency difference detector, and a control circuit to maintain atmosphere temperature uniformity by using the frequency difference between two crystal units as a temperature detection value, allowing for precise control of the heating unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional OCXO uses discrete analog parts (thermistor, operational amplifier, resistor, capacitor) for temperature control, then the device structure is simple, but temperature control precision cannot achieve ±20 m°C due to individual variation and long-term changes in analog parts
Solution Approach 1:
The patent replaces the mechanical/analog temperature sensing system (thermistor, operational amplifier, resistor, capacitor) with a digital frequency-based temperature detection system. Two crystal units are used where frequency differences between them indicate temperature, eliminating the need for discrete analog parts and achieving ±20 m°C precision through digital processing of frequency signals.
Solution Approach 2:
The patent changes the detection parameter from electrical resistance (analog) to oscillation frequency (digital). By monitoring frequency differences between two crystal units, the system achieves precise temperature detection without relying on analog components that suffer from individual variation and drift over time.
2Measurement precision
If frequency difference between two crystal units is used as temperature detection value, then temperature control precision improves, but the detection range becomes limited
Solution Approach 1:
The patent implements dynamic detection range adjustment by allowing the system to adaptively select between different detection methods based on the current temperature range. When the frequency difference method is insufficient, the system switches to alternative temperature detection approaches, ensuring both precision and wide adaptability across different operating conditions.
Solution Approach 2:
The patent creates a multi-functional temperature detection system that can operate in multiple modes: frequency difference detection for normal ranges, and alternative detection methods for extended ranges. This universal approach ensures the system maintains ±20 m°C precision while adapting to various temperature conditions and application requirements.
3Reliability
If conventional temperature control methods are used, then device complexity is low, but frequency stability cannot be sufficiently maintained for high-precision applications
Solution Approach 1:
The patent implements a feedback control system where temperature is continuously detected through frequency differences between two crystal units, and heating power is adjusted based on this detection. This closed-loop feedback mechanism ensures high frequency stability by actively compensating for temperature variations, overcoming the limitations of conventional open-loop temperature control methods.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach stabilizes the oscillation output with high frequency stability, reducing the yield reduction of crystal units and improving frequency-temperature characteristics, enabling effective temperature control and maintaining the atmosphere temperature at a set value.
Implementation Method 1
a heating unit configured to uniform an atmosphere temperature where each of the crystal units is placed
Implementation Method 2
a first oscillator circuit and a second oscillator circuit connected to respective first crystal unit and second crystal unit for temperature detection
Data Source
AI summary
A crystal controlled oscillator of the present disclosure includes: an oscillator circuit for oscillator output, a first oscillator circuit, a second oscillator circuit, a heating unit, a pulse generator, a frequency difference detector, an addition unit, a circuit unit, a frequency measuring unit, a determination unit, and a signal selector. The signal selector is configured to: select a control signal where electric power supplied to the heating unit is smaller than supplied electric power in the detection range in a case where a frequency in a set period at the train of pulses is out of the detection range at the high temperature side; select a control signal where electric power supplied to the heating unit becomes a preset value in a case where a frequency in the set period at the train of pulses is out of the detection range at the low temperature side.