Vector Synthesis Phase Shifter Calibration for Quadrature Error
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Solution Overview
Problem
Conventional vector sum phase shifters face challenges in achieving high phase shift precision due to manufacturing variations, which result in quadrature and amplitude errors between in-phase and quadrature signals, making it difficult to simultaneously cancel these errors and improve phase shift precision.
Innovation Solution
A phase shift precision calibration circuitry is integrated into the vector sum phase shifter, comprising a table memory, gain controller, detector, recorder, and calibrator to detect amplitude and phase errors, record gain settings, and calibrate the phase shift characteristic, allowing for precise adjustment of variable gain amplifier gains to improve phase shift accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a calibration method selecting one varactor from multiple varactors is used to eliminate manufacturing variation, then quadrature error can be reduced, but amplitude error cannot be canceled simultaneously and phase shift precision cannot be sufficiently improved
Solution Approach 1:
The patent changes the calibration approach from selecting discrete varactor components to continuously adjusting gain parameters of variable gain amplifiers. By adjusting the gain parameters G1 and G2 of the variable gain amplifiers, both quadrature error and amplitude error can be simultaneously corrected, achieving sufficient phase shift precision improvement without the limitations of fixed varactor selection
Solution Approach 2:
The patent implements a feedback-based calibration system using a detector to measure the actual phase and amplitude of the Q signal, comparing it with the I signal, and using this feedback information to adjust the gain parameters of the variable gain amplifiers. This closed-loop feedback mechanism enables simultaneous cancellation of both quadrature error and amplitude error, resolving the technical contradiction
2Manufacturing precision
If varactor capacitance is used to compensate manufacturing variation, then quadrature error can be corrected, but the parasitic series resistance of the varactor prevents simultaneous amplitude error cancellation
Solution Approach 1:
The patent extracts the error compensation function from the varactor component and transfers it to the variable gain amplifier circuitry. By removing the reliance on varactor capacitance adjustment and using only gain parameter adjustment in the variable gain amplifiers, the harmful parasitic series resistance effect is eliminated while maintaining the ability to correct both quadrature and amplitude errors
Solution Approach 2:
The patent substitutes the electrical component-level correction mechanism (varactor capacitance adjustment) with a circuit-level parameter adjustment mechanism (variable gain amplifier gain control). This substitution replaces the physical varactor component's electrical property adjustment with electronic gain parameter control, eliminating the parasitic resistance limitation
Data Source
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AI summary
There are provided: a table memory to store a relation between a control code and gains of variable gain amplifiers; a gain controller to apply the gains to the variable gain amplifiers; an amplitude phase detector to detect amplitude and a phase from an output signal of the vector sum phase shifter; an amplitude phase recorder to record, when the gains are applied by the gain controller, a combination of a control code corresponding to said gains and the amplitude and the phase detected by the detector; and a table calibrator to find a phase shift characteristic of a vector summed part from records of the amplitude phase recorder and calibrate the relation between a control code and gains recorded in the table memory by using the phase shift characteristic.