IQ Clock Phase Calibration for Quadrature Mixer Mismatch
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Solution Overview
Problem
In transmitters and receivers with quadrature mixers, phase and magnitude mismatches occur due to undesired phase mismatches in the generation of LO phases, leading to errors in upconverted or downconverted signals.
Innovation Solution
A communication circuit with a calibration system that adjusts input data based on the duty cycles of clock signals to reduce phase and magnitude mismatches, using a frequency synthesizer to generate clock signals and an IQ calibration system to generate and store digital values corresponding to duty cycles, thereby compensating for phase errors in the mixer clock phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If four LO phases are generated using a divide-by-N phase generator, then the system can achieve quadrature mixing, but phase mismatch occurs due to mismatches in the generation of the four LO phases
Solution Approach 1:
The patent changes the duty cycle parameter of clock signals from the ideal 50% to optimized values (e.g., 40%-60%) to compensate for phase mismatch. By adjusting this physical parameter, the system corrects phase errors without requiring complex additional circuitry, thus resolving the contradiction between maintaining quadrature mixing and achieving phase accuracy.
2Productivity
If passive mixers with non-overlapping clocks are used, then the system achieves frequency conversion, but phase and magnitude mismatch occurs in the upconverted or downconverted signal
Solution Approach 1:
The patent applies preliminary correction to the input data by adjusting it based on pre-determined duty cycle optimization values before the mixing operation. This preliminary action compensates for expected phase and magnitude mismatches, ensuring higher signal quality in the frequency conversion process without compromising the mixer's operational capability.
3Measurement precision
If clock signals with different duty cycles are used, then phase calibration can be achieved, but the system requires additional calibration complexity
Solution Approach 1:
The patent introduces dynamic adjustment of duty cycle parameters through a calibration system that can adaptively optimize clock signal characteristics. The system dynamically selects optimal duty cycle values to achieve phase calibration, balancing the need for precision with acceptable system complexity through programmable control rather than fixed complex hardware.
Data Source
AI summary
A communication circuit is disclosed. The communication circuit includes a calibration system, configured to receive clock signals respectively having first and second clock phases, and first and second duty cycles, where the calibration system is further configured to receive input data and to adjust the input data to generate adjusted data based partly on the input data and based partly on the first and second duty cycles. The communication circuit also includes a mixer, configured to receive the clock signals and to receive the adjusted data, where the mixer is configured to generate output data based on the clock signals and the adjusted data, and where a mismatch in the output data caused by the first and second duty cycles being different is reduced because of the adjustment made to the input data to generate the adjusted data.