Passive Harmonic-Rejection Mixer Calibration for Accurate Weighting
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Solution Overview
Problem
Passive harmonic-rejection mixers face challenges in achieving high harmonic rejection due to finite and frequency-dependent input impedance of IF amplifiers, which complicates the accurate weighting of RF currents, and require precise calibration for effective harmonic cancellation.
Innovation Solution
A segmented approach with calibration circuitry is implemented, where individual sub-mixing stages are used to cancel harmonic conversion products, and the calibration method fine-tunes the weighting of each sub-mixer stage to improve harmonic rejection, relaxing the requirements on IF amplifier input impedance and compensating for processing variations and component mismatches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If passive mixers are used to achieve better 1/f noise and higher linearity, then noise performance and linearity are improved, but harmonic rejection becomes more difficult to implement
Solution Approach 1:
The passive mixer is divided into multiple segments, each processing a different portion of the RF signal spectrum. By segmenting the mixer architecture, the patent achieves harmonic rejection functionality in passive mixers without compromising noise performance or linearity, as each segment can be independently optimized for its specific frequency range
2Reliability
If the input impedance of IF amplifiers is reduced to improve harmonic rejection, then harmonic rejection performance is improved, but the frequency-dependent nature of input impedance makes it difficult to maintain over the frequency range
Solution Approach 1:
The patent employs dynamic equalization circuits that automatically adjust the input impedance characteristics of the IF amplifiers across different frequencies. This dynamic adjustment allows the system to maintain optimal harmonic rejection performance (input impedance less than 0.3 Ohm) across the entire frequency range of the received RF signal and its harmonics, compensating for the natural frequency-dependent variations in amplifier input impedance
Solution Approach 2:
The patent changes the electrical parameters (impedance values) of the IF amplifier stages through equalization circuits. By dynamically modifying the input impedance parameters of the amplifiers, the system achieves consistent harmonic rejection performance across varying frequencies, transforming the fixed impedance characteristic into an adaptive one
3Measurement precision
If precise calibration is implemented to compensate for processing variations and component mismatches, then harmonic rejection accuracy is improved, but device complexity and calibration time increase
Solution Approach 1:
The patent incorporates preliminary calibration procedures during the manufacturing and assembly process. By performing initial calibration of the equalization circuits and mixer segments before deployment, the system pre-compensates for processing variations and component mismatches, reducing the need for extensive field calibration and minimizing calibration time during operation
Data Source
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AI summary
An electronic device comprising a passive harmonic-rejection mixer (400) and a calibration circuitry (425). The passive harmonic rejection mixer has an input (102) connected to several sub-mixer stages (402), and the sub-mixer stages are connected to a summing module (406, 408) for generating the output (104). Each sub-mixing stage comprises a gating module (414), an amplifier (416), and a weighting module (418), the gating module selectively passing the input signal or the input signal with inverted polarity under the control of control signals. The calibration circuitry (425) is adapted to input a reference signal (430) to the input of the mixer, receive an output signal (104) from the output of the mixer, and set the weights (K1, K2, K3, K4) of the weighting modules to make the output signal match an expected output signal.