Two-Stage Polyphase Harmonic Rejection Mixer for Mismatch Robustness
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Solution Overview
Problem
Conventional harmonic rejection mixers are susceptible to gain and phase mismatch due to process, voltage, and temperature variations, limiting their harmonic rejection ratio (HRR) to around 30 to 40 dBc and requiring calibration to achieve higher HRR.
Innovation Solution
A multi-stage polyphase harmonic rejection mixer is introduced, which distributes weighting and combining over two stages to achieve higher HRR by using integer ratios to approximate irrational weighting ratios, reducing the impact of component mismatch and achieving accurate phase and gain alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional hard-switching mixers are used with weighted combining to achieve harmonic rejection, then the harmonic rejection ratio can be improved, but the mixer becomes highly susceptible to gain and phase mismatch from PVT variations
Solution Approach 1:
The patent divides the single-stage weighted combining into multiple stages, where each stage performs partial weighting and combining. This segmentation reduces the sensitivity to gain and phase mismatch in each individual stage, as the overall harmonic rejection is achieved through cumulative effect across stages rather than requiring precise single-stage weighting.
Solution Approach 2:
The patent employs tuning mechanisms that allow dynamic adjustment of phase and gain parameters in response to PVT variations. This enables the mixer to maintain optimal harmonic rejection performance under varying operating conditions by adapting the weighting parameters in real-time.
2Measurement precision
If careful alignment of phase and amplitude is implemented to achieve high harmonic rejection ratio, then the harmonic rejection performance is improved, but the device complexity and calibration requirements increase
Solution Approach 1:
By dividing the weighting and combining into multiple stages, each stage requires less precise alignment compared to a single-stage implementation. This reduces the overall calibration complexity while achieving the same or better harmonic rejection ratio.
Solution Approach 2:
The patent incorporates automatic tuning mechanisms that reduce the need for manual calibration. The system can automatically adjust phase and gain parameters to maintain optimal harmonic rejection performance, reducing device complexity and calibration requirements.
Data Source
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AI summary
A polyphase harmonic rejection mixer, comprising a plurality of stages following each other; wherein a first stage is arranged to perform at least frequency conversion; and a second stage is arranged to perform at least selective weighting and combining; wherein at least two of the plurality of stages are arranged to perform at least combining. In an embodiment, the first stage (28) comprises three single-ended gain blocks (10, 12, 14), arranged to perform selective weighting, frequency conversion and combining; and a second stage (30) following the first stage (28) and arranged to perform selective weighting and combining. The second stage (30) may reduce the number of phases output by the first stage (28) and may output (32) a complex differential down converted signal. The mixer may be directly interfaced to an antenna of an LNA-less receiver without weighting in the first stage. The mixer may be included in a software-defined radio.