Auxiliary Mixer Circuit for Phase Imbalance Correction
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Solution Overview
Problem
Wireless communication systems face phase imbalance issues between in-phase (I) and quadrature (Q) components in RF circuits, leading to increased residual sideband (RSB) and image rejection problems, which existing calibration techniques often address at the expense of introducing amplitude errors.
Innovation Solution
The implementation of a circuit and method using auxiliary mixers to perform duplex phase imbalance adjustment by combining partial outputs of auxiliary mixers with conventional I and Q mixer outputs, allowing for phase correction without amplitude errors, through programmable scaling and phase inversion of frequency converted signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing calibration techniques are used to correct phase imbalance, then phase imbalance is reduced, but amplitude errors are introduced
Solution Approach 1:
The calibration process is segmented into two independent stages: phase calibration using auxiliary mixers to correct phase imbalance, and amplitude calibration to correct amplitude errors. This segmentation allows each stage to address its specific parameter without interfering with the other, resolving the contradiction between phase and amplitude precision
Solution Approach 2:
Auxiliary mixers are introduced as intermediary components to perform phase calibration separately from the main signal path. These auxiliary mixers enable phase correction without directly affecting the amplitude characteristics of the main I and Q signal paths, thus preventing amplitude errors during phase calibration
2Measurement precision
If phase correction is performed using conventional methods, then phase imbalance is corrected, but residual sideband increases
Solution Approach 1:
The system employs feedback mechanisms where the outputs of auxiliary mixers are combined with main mixer outputs in a controlled manner. This feedback approach allows iterative refinement of phase correction while monitoring and minimizing residual sideband levels, achieving both phase correction and low RSB
Solution Approach 2:
The invention changes the calibration parameters by introducing programmable scaling factors and phase shift amounts that can be independently adjusted. By optimizing these parameters through calibration routines, the system achieves effective phase correction while minimizing residual sideband generation
3Measurement precision
If auxiliary mixers are used for phase correction, then phase imbalance is minimized, but circuit complexity increases
Solution Approach 1:
The auxiliary mixers are designed to serve multiple functions: phase calibration, amplitude calibration, and residual sideband cancellation. This multi-functionality reduces the need for separate dedicated components for each calibration task, thereby limiting the increase in circuit complexity despite the addition of auxiliary mixers
Solution Approach 2:
The calibration functions are merged into a unified process where auxiliary mixer outputs are combined with main mixer outputs through programmable scaling and phase shifting. This merging approach consolidates multiple calibration operations into a single integrated system, reducing overall complexity compared to separate calibration circuits
Data Source
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AI summary
Certain aspects of the present disclosure provide methods and apparatus for performing quadrature combining and adjusting. One example circuit may include first through fourth mixing circuits. The first mixing circuit may multiply a radio frequency signal with a first local oscillating signal to generate a first frequency converted signal. The second mixing circuit may multiply a radio frequency (RF) signal with a second local oscillating signal, which may be about 90 out of phase with the first local oscillating signal, to generate a second frequency converted signal. The third and fourth mixing circuits may multiply the RF signal with the second and first signals, respectively, to generate third and fourth frequency converted signals, respectively. A first combining circuit may combine the first and third frequency converted signals, and a second combining circuit may combine the second and fourth frequency converted signals.