Ring Oscillator Frequency Multiplier With Calibration for Low Jitter
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Solution Overview
Problem
Existing frequency multipliers based on ring oscillators face challenges in achieving low jitter and high output frequencies due to limitations in lock range and injection current as frequency multiple N increases, leading to decreased jitter performance.
Innovation Solution
A frequency multiplier design that utilizes complementary ring oscillators, a combining circuit, and a calibration circuit to correct discontinuous pulses, adjusting pulse widths and frequencies to generate a seamless output signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a single ring oscillator is used for frequency multiplication, then the circuit area is small, but the jitter performance deteriorates at high frequency multiples
Solution Approach 1:
The frequency multiplier is divided into multiple ring oscillators (first, second, and third ring oscillators) that operate in complementary fashion. Each oscillator handles a portion of the frequency multiplication task, with their outputs combined to achieve the final N-times frequency multiplication. This segmentation allows each oscillator to operate within its optimal performance range while collectively achieving high frequency multiplication with low jitter.
2Adaptability or versatility
If the injection pulse width is increased to improve lock range, then the lock range increases, but the power consumption increases
Solution Approach 1:
The injection signals are applied periodically to the ring oscillators in a complementary manner. The first and second ring oscillators receive injection signals during different time periods, with their injection pulse widths adjusted to be non-overlapping. This periodic, time-division injection approach maintains adequate lock range while reducing the total power consumption compared to continuous or overlapping injection.
3Reliability
If complementary ring oscillators are used to improve jitter performance, then the jitter performance improves, but the device complexity increases
Solution Approach 1:
The outputs of multiple ring oscillators are combined using a combining circuit that merges their individual outputs to produce the final frequency-multiplied signal. The combining circuit integrates the signals from the first, second, and third ring oscillators in a manner that achieves the N-times frequency multiplication while maintaining low jitter performance. This merging approach consolidates the functionality of multiple oscillators into a unified output.
4Speed
If the number of ring oscillators is increased to achieve higher frequency multiples, then the output frequency increases, but the discontinuous pulses increase
Solution Approach 1:
A calibration circuit is employed that uses feedback from the combined output signal to detect and correct discontinuous pulses. The calibration circuit monitors the output from the combining circuit and adjusts the injection pulse widths of the individual ring oscillators to eliminate gaps or discontinuities in the frequency-multiplied signal, ensuring smooth and continuous operation at high frequency multiples.
Data Source
AI summary
A frequency multiplier includes a first ring oscillator, a second ring oscillator that is turned on complementarily to the first ring oscillator, a combining circuit that combines a first output signal of the first ring oscillator and a second output signal of the second ring oscillator to generate a final output signal, and a calibration circuit that corrects a discontinuous pulse included in the final output signal based on feedback of the final output signal.