Wireless Transceiver IQ Calibration Using Shared RF Front-End Circuit
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Solution Overview
Problem
Current RF transceivers face challenges in achieving a low image rejection ratio (IRR) due to mismatch between in-phase and quadrature-phase signal paths, as RX IQ calibration does not perfectly align with TX IQ calibration, resulting in incompatible circuit symmetry and output impedance.
Innovation Solution
A wireless transceiver design incorporating a transmitter, receiver, signal generator, and switch circuits, where the first switch circuit is used for RX calibration and the second switch circuit for TX calibration, ensuring both calibrations occur under identical RF front-end circuit conditions, allowing for accurate IQ calibration and low IRR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If separate RF front-end circuits are used for RX and TX, then the transceiver can perform both receiving and transmitting functions, but the circuit symmetry and output impedance observed during RX IQ calibration differ from those during TX IQ calibration, resulting in incompatible calibration results and poor image rejection ratio
Solution Approach 1:
The patent merges the RF front-end circuit used during RX IQ calibration with the same RF front-end circuit used during TX IQ calibration. By using the identical RF front-end circuit for both calibration processes, the circuit symmetry and output impedance characteristics remain consistent, making the RX IQ calibration results directly applicable to TX IQ calibration and achieving low image rejection ratio.
Solution Approach 2:
The RF front-end circuit is designed to serve multiple functions: it acts as the receiver RF front-end circuit during RX IQ calibration and as the transmitter RF front-end circuit during TX IQ calibration. This multi-functionality ensures that the same circuit characteristics are used in both calibration processes, resolving the incompatibility issue.
2Adaptability or versatility
If the in-phase path circuit and quadrature-phase path circuit are not made identical, then circuit design flexibility is improved, but signal path mismatch occurs leading to generation of image signals and poor image rejection ratio
Solution Approach 1:
The patent applies local quality by making the in-phase path circuit and quadrature-phase path circuit substantially identical in structure and characteristics. This local symmetry in the signal paths ensures that both paths process signals with matching characteristics, minimizing signal path mismatch and reducing image signal generation, thereby achieving low image rejection ratio while maintaining overall circuit design flexibility.
Data Source
AI summary
A wireless transceiver having an in-phase quadrature-phase (IQ) calibration function includes a transmitter, a receiver, a signal generator, and a switch circuit. The switch circuit includes a first and a second switch circuits. The first switch circuit is turned on in a receiver-end calibration process, and outputs a predetermined signal from the signal generator to the transmitter. The second switch circuit is turned on in the receiver calibration process and outputs a derivative signal of the predetermined signal from the transmitter to the receiver to let the receiver performs a receiver-end IQ calibration accordingly. The first switch circuit is turned off and the second switch circuit is turned on in a transmitter-end calibration process; the second switch circuit outputs a radio-frequency signal from the transmitter to the receiver to let the receiver generates a calibration reference accordingly; and the transmitter performs a transmitter-end IQ calibration according to the calibration reference.