LC Digitally Controlled Oscillator Temperature Compensation
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Solution Overview
Problem
Digitally controlled oscillators (DCOs) face challenges in maintaining stable output frequency due to temperature variations, with existing methods struggling to achieve low temperature drift, especially for LC-DCOs, which exhibit significant temperature sensitivity.
Innovation Solution
A combination of supply voltage compensation and a temperature compensating capacitor bank is used to reduce temperature sensitivity, where the voltage reference supply adjusts the supply voltage and the temperature compensation capacitor bank adjusts capacitance to correct for both linear and non-linear frequency errors, leveraging a synergistic effect to achieve stable frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a temperature sensor and temperature compensation capacitor bank are used, then temperature sensitivity is improved, but temperature drift remains high due to sensor inaccuracies and analog varactor temperature dependence
Solution Approach 1:
The patent replaces the analog temperature compensation system (analog varactors and continuous voltage control) with a digital system using switched capacitor banks controlled by digital signals. This substitution eliminates the temperature dependence of analog varactors and improves measurement precision by using digital temperature sensing and processing, directly resolving the contradiction between measurement precision and reliability.
Solution Approach 2:
The patent changes the control parameter from continuous analog voltage to discrete digital control signals that switch between fixed capacitor values. By quantizing the capacitance values and using digital control, the system achieves better temperature compensation accuracy and reduces the impact of temperature drift, thereby improving both measurement precision and frequency stability.
2Adaptability or versatility
If LC oscillator topology is used in DCO, then frequency range and tuning capability are improved, but temperature sensitivity increases significantly
Solution Approach 1:
The patent segments the continuous capacitance adjustment into discrete steps using multiple switched capacitor banks with different capacitance values. This segmentation allows the LC oscillator to maintain its frequency tuning capability while using digital control to compensate for temperature effects, thereby reducing temperature sensitivity without sacrificing adaptability.
Solution Approach 2:
The patent implements a feedback mechanism where the temperature is sensed and used to control the switching of capacitor banks to counteract temperature-induced frequency drift. This closed-loop feedback system maintains frequency stability across temperature variations while preserving the wide tuning range of the LC oscillator topology.
3Object-affected harmful factors
If ring oscillator topology is used in DCO, then temperature sensitivity is reduced compared to LC oscillator, but frequency tuning capability and Q-factor are limited
Solution Approach 1:
The patent merges the advantages of both ring oscillator and LC oscillator topologies by using the LC oscillator structure with digital temperature compensation. This combination achieves the low temperature sensitivity of ring oscillators while maintaining the superior frequency tuning capability and Q-factor of LC oscillators, resolving the contradiction between these two features.
Data Source
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AI summary
A device comprising: a voltage reference supply (120), configured to provide a reference voltage that varies in response to temperature according to a predefined relationship; a temperature sensor (130) providing a temperature signal indicating a temperature; a first controller (140) configured to receive the temperature signal and to output a control signal; an LC-DCO (110) receiving the reference voltage and providing an output signal with a frequency from an LC circuit, the LC-DCO (110) comprising a switched capacitor bank configured to provide temperature compensation by varying an effective capacitance in the LC circuit in response to the control signal.