Quadrature Clock Path Deskew With Adaptive Phase Correction
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Solution Overview
Problem
Quadrature clocking schemes in modern communications systems suffer from phase imbalance due to quadrature skew and duty cycle distortion, which degrade the receiver's eye and increase jitter, and existing solutions require large area and high power consumption.
Innovation Solution
A system with inner and outer correction loops, including amplifiers, duty cycle correction circuits, error detectors, error amplifiers, and steering circuits, that correct for duty cycle distortion and quadrature skew by using feedback mechanisms to align the in-phase and quadrature phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyphase circuits with PLLs and DLLs are used to generate I and Q signals locally, then quadrature skew and duty cycle distortion are avoided, but area occupancy and power consumption increase substantially
Solution Approach 1:
The patent extracts only the essential function of phase generation from the complex polyphase circuit, using a simple ring oscillator to generate the clock signal while eliminating the need for bulky PLLs and DLLs. This reduces area occupancy while maintaining the core functionality of generating quadrature phases.
Solution Approach 2:
The patent changes the approach from using complex feedback-based phase locking mechanisms to using a fixed-frequency ring oscillator with deterministic phase relationships. This parameter change in the oscillation mechanism reduces both area and power while maintaining signal quality.
2Reliability
If polyphase circuits with PLLs and DLLs are used to generate I and Q signals locally, then quadrature skew and duty cycle distortion are avoided, but power consumption increases substantially
Solution Approach 1:
The patent removes the power-intensive PLL and DLL circuits from the system, retaining only the essential ring oscillator that consumes significantly less power while still providing the necessary quadrature phase signals for communication.
Solution Approach 2:
The patent replaces expensive, power-consuming precision phase-locking circuits with a simpler, lower-power ring oscillator approach that achieves adequate performance without the overhead of complex feedback mechanisms.
3Device complexity
If conventional transmission lines are used to transmit clock signals, then simple routing is achieved, but quadrature skew and duty cycle distortion occur
Solution Approach 1:
The patent generates all four phase signals (0°, 90°, 180°, 270°) simultaneously at the source using a ring oscillator, rather than transmitting a single clock signal and generating phases locally at the destination. This preliminary generation of all phases eliminates the skew problems associated with long transmission lines.
Solution Approach 2:
The patent creates multiple phase copies (0°, 90°, 180°, 270°) of the clock signal simultaneously at the source using the ring oscillator's inherent phase relationships, rather than copying a single clock signal through transmission lines where phase distortion occurs.
Data Source
AI summary
Quadrature clocking schemes are widely used in modern communications systems, but often suffer from phase imbalance. Conventional solutions that attempt to address this phase imbalance, however, are generally large and use a substantial amount of power. Here, however, a correction circuit is provided that can locally correct for phase imbalance without the need for bulky and high power consuming circuitry.