Multiphase Clock Interpolation for Rotational and Static IQ Skew
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Solution Overview
Problem
In serial receiver systems, rotational and static phase skews between in-phase (I) and quadrature (Q) clocks generated by phase interpolators lead to increased bit errors due to non-linearity characteristics, causing the I clock to jitter or remain offset from the center of the data bit, affecting sampling accuracy.
Innovation Solution
A system comprising a phase interpolator and a ring oscillator or clock mixers that generate corrected clocks with a static phase relationship, using opposite polarity clocks and clock mixers to maintain a 90° phase difference between I and Q clocks, and a rotational IQ phase skew correction unit using an injection-locked ring oscillator to minimize phase skews.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a phase interpolator is used to generate I and Q clocks to overcome frequency offset, then the frequency alignment with received data is improved, but rotational and static phase skews occur causing the I clock to jitter or offset from the center of data bits
Solution Approach 1:
The patent implements a feedback mechanism where the receiver measures the phase relationship between received symbols and locally generated I and Q clocks, detects rotational and static skews, and feeds back correction signals to adjust the phase interpolator settings. This closed-loop feedback eliminates phase skews by continuously correcting the I and Q clock phases based on measured deviations, thereby resolving the contradiction between frequency alignment and phase accuracy.
2Stability of the object's composition
If crystal oscillators are used to provide clock frequencies, then the frequency stability is improved, but mechanical differences cause plesiochronous operation with frequency offsets
Solution Approach 1:
The patent changes the operational parameters of the crystal oscillators by using a phase interpolator to dynamically adjust the phase and frequency of the I and Q clocks. Instead of relying solely on the fixed frequencies from separate crystal oscillators, the system continuously modifies the clock parameters to achieve precise frequency synchronization with the received data, thereby resolving the contradiction between frequency stability and frequency synchronization.
3Speed
If the phase interpolator advances the phase of I and Q clocks to align with received data, then the frequency offset compensation is improved, but non-linearity characteristics cause the quadrature relationship to deteriorate
Solution Approach 1:
The patent employs feedback to continuously monitor the quadrature relationship between I and Q clocks after phase advancement. The system measures any deviations from the ideal 90-degree phase difference and feeds back correction signals to the phase interpolator, adjusting the phase advancement amounts for I and Q clocks separately. This feedback mechanism ensures that frequency offset compensation is achieved while maintaining precise quadrature relationships, resolving the contradiction between frequency offset compensation and quadrature relationship precision.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Effectively eliminates rotational and static IQ phase skews, ensuring accurate sampling of data bits and reducing bit errors by maintaining precise quadrature relationships between I and Q clocks.
Implementation Method 1
a rotational IQ phase skew correction unit comprising an injection-locked ring oscillator that receives at least one in-phase (I) clock and at least one quadrature (Q) clock
Data Source
AI summary
Systems and methods disclosed herein provide for effectively eliminating the rotational and static phase skews between the in-phase (I) and quadrature (Q) clocks generated by phase interpolators in decision feedback equalizer based receivers. Embodiments of the systems and methods provide for (i) a ring oscillator that eliminates the rotational phase skews and (ii) a plurality of clock mixers that eliminate the static phase skews.