VC-TCXO Gain Control for Stable Frequency-Temperature Compensation
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Solution Overview
Problem
Voltage control type temperature compensation piezoelectric oscillators experience a shift in frequency-temperature characteristic when the external control voltage varies, leading to deteriorated temperature compensation.
Innovation Solution
A voltage control type temperature compensation piezoelectric oscillator with a gain variable circuit controlled by the AFC circuit, which adjusts the gain based on the external control voltage to maintain the frequency-temperature characteristic within a desired range, incorporating a temperature compensation voltage generating circuit, a piezoelectric resonator, and variable capacitance elements for temperature compensation and frequency variation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the external control voltage is varied to change the oscillation frequency, then the oscillation frequency can be adjusted, but the frequency-temperature characteristic shifts from the initial characteristic
Solution Approach 1:
The gain of the temperature compensation voltage generating circuit is made variable rather than fixed. The gain changes dynamically based on the control voltage level, being larger when the control voltage is near the center value and smaller when it deviates. This dynamic gain adjustment compensates for the non-linear f-V characteristic of the varactor diode, maintaining stable frequency-temperature characteristics across the full frequency adjustment range.
Solution Approach 2:
The invention changes the parameter of gain in the temperature compensation voltage generating circuit based on the control voltage level. By adjusting the gain parameter dynamically, the system compensates for the non-linear frequency-voltage characteristic of the varactor diode, ensuring that the frequency-temperature characteristic remains stable even when the oscillation frequency is varied over a wide range.
2Measurement precision
If the gain of temperature compensation voltage generating circuit is optimized for center value, then accurate temperature compensation is achieved at center frequency, but compensation accuracy deteriorates when control voltage deviates from center value
Solution Approach 1:
The gain of the temperature compensation voltage generating circuit is made dynamically adjustable based on the control voltage level. When the control voltage is near the center value, the gain is larger to provide accurate compensation. When the control voltage deviates from the center value, the gain is automatically reduced to match the non-linear f-V characteristic of the varactor diode, maintaining compensation accuracy across the entire frequency adjustment range.
Solution Approach 2:
The system uses the control voltage itself as a feedback signal to adjust the gain of the temperature compensation voltage generating circuit. This feedback mechanism ensures that the gain automatically adapts to the control voltage level, maintaining optimal temperature compensation accuracy whether the oscillator is operating at center frequency or at the extremes of its frequency range.
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
The solution effectively maintains the frequency-temperature characteristic within a specified range even when the external control voltage is varied, ensuring stable oscillation frequency and accurate temperature compensation.
Implementation Method 1
a voltage control type oscillation circuit (6) comprising: a piezoelectric resonator (X)
Implementation Method 2
a frequency-voltage (f-V) characteristic of the varactor diode 55
Data Source
AI summary
A voltage control type temperature compensation piezoelectric oscillator, includes: a voltage control type oscillation circuit; an automatic frequency control (AFC) circuit outputting a control voltage for controlling an oscillation frequency of the voltage control type oscillation circuit based on an external control voltage; a temperature compensation voltage generating circuit generating a temperature compensation voltage; and a gain variable circuit varying a gain of the temperature compensation voltage. In the oscillator, the gain variable circuit is controlled by the control voltage outputted from the AFC circuit, and the oscillation frequency of the voltage control type oscillation circuit is controlled by an output voltage of the gain variable circuit.