Multi-Stage Polyphase Mixer for Harmonic Rejection Mismatch
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Solution Overview
Problem
Conventional polyphase 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 for higher performance.
Innovation Solution
A multi-stage polyphase harmonic rejection mixer is implemented, with at least two stages performing selective weighting and combining, using integer ratios to approximate irrational weighting ratios, reducing the number of phases and outputting a complex differential down-converted signal, thereby reducing susceptibility to gain mismatch and achieving higher HRR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional single-stage HR mixer uses weighted combination of hard-switching mixers, then harmonic rejection ratio can reach 30 to 40 dBc, but the mixer becomes highly susceptible to gain and phase mismatch from PVT variations
Solution Approach 1:
The mixer is divided into multiple stages, where the first stage performs frequency conversion and subsequent stages perform selective weighting and combining. This segmentation allows each stage to have specialized functions, reducing the susceptibility to PVT variations by distributing the harmonic rejection function across multiple independent stages rather than relying on a single complex weighted combination stage.
Solution Approach 2:
The patent transitions from a single-stage architecture to a multi-stage architecture, adding the dimension of temporal processing. By distributing the weighting and combining operations across multiple stages that process signals sequentially, the system achieves better control over gain and phase relationships, reducing susceptibility to PVT variations while maintaining or improving harmonic rejection ratio.
2Measurement precision
If careful alignment of phase and amplitude is implemented to achieve high HRR, then harmonic rejection ratio improves beyond 30 to 40 dBc, but device complexity and calibration requirements increase
Solution Approach 1:
By segmenting the mixer into multiple stages with distinct functions (frequency conversion in first stage, selective weighting and combining in subsequent stages), the patent simplifies the alignment requirements for each individual stage. This segmentation reduces overall device complexity and calibration requirements compared to a single-stage design that would require precise alignment of all weighting parameters simultaneously.
Solution Approach 2:
The first stage performs frequency conversion preliminarily, preparing the signal for subsequent weighting and combining stages. This preliminary action allows later stages to focus specifically on harmonic rejection through weighting and combining, simplifying their design and reducing overall calibration requirements compared to a single-stage design where all functions must be precisely aligned simultaneously.
Data Source
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.