Injection-Locked Ring Oscillator Offset Calibration for Stable Locking
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Solution Overview
Problem
Oscillator circuits face phase error detection issues due to manufacturing imperfections, process variations, and temperature changes, leading to offsets that reduce locking range and can prevent the oscillator loop from locking.
Innovation Solution
An injection locked ring oscillator (ILRO) circuit with a calibration sequence to program circuitry for detecting phase differences and generating power or control voltage to compensate for offsets, using a phase detector, gain stage, and offset compensation register to optimize phase differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase error detection circuitry is used to control oscillator frequency and phase, then locking accuracy is improved, but offsets from manufacturing imperfections and environmental variations reduce locking range and may prevent locking
Solution Approach 1:
The patent applies preliminary action by performing offset calibration before normal oscillator operation. A calibration sequence is executed that measures and stores offset values from the phase error detection circuitry and feedback control circuits under known conditions. These pre-determined offset values are then used to compensate for manufacturing imperfections and environmental variations during actual operation, ensuring both high measurement precision and reliable locking across varying conditions.
2Measurement precision
If feedback control circuits are used to adjust oscillator frequency, then phase locking accuracy is improved, but circuit offsets reduce the effective locking range
Solution Approach 1:
The patent implements feedback by using the calibrated offset values to adjust the operation of feedback control circuits. The system continuously monitors phase errors and applies corrective control signals that are compensated for known offset values. This feedback mechanism with offset compensation enables the oscillator to maintain accurate phase locking across a wider frequency range, effectively resolving the contradiction between locking accuracy and locking range.
3Reliability
If offset compensation calibration is performed, then locking range and reliability are improved, but additional circuit complexity and calibration procedures are required
Solution Approach 1:
The patent applies self-service by designing a calibration system that automatically measures and stores its own offset values without requiring external intervention or complex manual adjustment procedures. The calibration sequence is initiated and executed automatically, using the oscillator's own phase error detection circuitry to measure offsets under controlled conditions. This self-calibrating approach minimizes additional circuit complexity while significantly improving locking reliability.
Data Source
AI summary
A method of using an oscillator circuit is disclosed. The method includes: with an oscillator, generating a plurality of output clock signals based on an override control signal; with a phase detector circuit, generating a phase error signal based on the output clock signals; with a gain stage circuit, modifying a feedback control signal based on the phase error signal and an offset compensation code; with a controller, modifying the offset compensation code; with a comparator, generating an equality signal indicating that the feedback control signal is equal to the override control signal; and with the controller, in response to the equality signal, causing the modified offset compensation code to be stored.