Injection-Locked Ring Oscillator Calibration for Frequency Matching
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Solution Overview
Problem
Injection-locked oscillators in wireless communication systems face frequency mismatch issues between their output and input signals, leading to degraded performance characteristics such as phase mismatch, reduced tracking bandwidth, and increased jitter.
Innovation Solution
A calibration system comprising a ring oscillator, main and replica injection apparatuses, and a calibration apparatus with amplitude comparator, frequency detector, and state machine generates fine-tuning and coarse-tuning codes to adjust bias currents and gains, ensuring the output signal matches the input signal frequency, thereby minimizing frequency errors and improving performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If an injection-locked oscillator is used to provide wide locking range and low power consumption, then power efficiency and locking range are improved, but frequency mismatch between output and input signals occurs leading to phase error and reduced tracking bandwidth
Solution Approach 1:
The patent applies preliminary action by performing calibration of the injection-locked oscillator during manufacturing or initialization. The calibration process measures the actual frequency of the output signal and determines correction values that are stored and applied during normal operation, thereby pre-compensating for frequency mismatch before it affects system performance.
Solution Approach 2:
The patent implements feedback by continuously monitoring the output signal frequency and using the measured information to adjust control parameters of the injection-locked oscillator. This closed-loop feedback mechanism dynamically compensates for frequency drift and mismatch, ensuring accurate frequency tracking while maintaining the power efficiency benefits of the injection-locked architecture.
2Measurement precision
If calibration procedures are implemented to reduce frequency mismatch, then frequency accuracy and phase matching are improved, but device complexity and calibration overhead increase
Solution Approach 1:
The patent uses copying by creating a simplified model or replica of the injection-locked oscillator's frequency characteristics during calibration. This model is used to predict and correct frequency mismatch without requiring complex real-time measurements and adjustments, thereby reducing calibration system complexity while maintaining frequency accuracy.
Solution Approach 2:
The patent applies parameter changes by adjusting key control parameters of the injection-locked oscillator (such as tank capacitance, injection strength, or bias currents) during calibration to optimize frequency matching. By focusing calibration efforts on a limited set of critical parameters rather than all system parameters, the complexity of the calibration process is reduced while achieving the desired frequency accuracy.
Data Source
AI summary
An apparatus comprises a ring oscillator comprising a plurality of delay cells connected in cascade, a main injection apparatus comprising a plurality of main buffers, wherein the main buffers receive a reference clock from their inputs and the outputs of the main buffers are coupled to respective inputs of the delay cells and a replica injection apparatus comprising a plurality of replica buffers, wherein the replica buffers receive the reference clock from their inputs and the replica buffers are configured such that the replica buffers are tri-stated and each output is connected to ground when the ring oscillator operates in an injection-locked mode and each output is connected to ground through a capacitor when the ring oscillator operates in a calibration mode.