Quadrature Error Compensation Using Cross-Correlation Feedback
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Solution Overview
Problem
Conventional quadrature error compensating circuits fail to accurately detect and correct phase errors in 90° phase shifters due to variations in characteristics between analog elements of analog baseband filters, leading to inaccurate phase error correction.
Innovation Solution
A quadrature error compensating circuit that includes a first filter, a multiplier, a subtractor, and a correlation calculating circuit, which calculates a cross-correlation value to correct quadrature phase errors by filtering low-band signal components and using feedback operations to reduce interference, thereby accurately correcting phase errors even in frequency bands with small variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional phase error detection methods are used in quadrature error compensating circuits, then the detection process is simple, but the detection accuracy is insufficient due to variations in analog baseband filter characteristics
Solution Approach 1:
The patent segments the signal processing into distinct functional blocks: analog baseband filters (first and second filters), multipliers for mixing signals, subtractors for combining signals, and a correlation calculating circuit. This segmentation allows each component to perform its specific function optimally, with the correlation circuit specifically designed to calculate cross-correlation values that accurately detect phase errors despite filter characteristic variations.
Solution Approach 2:
The patent implements a feedback mechanism where the correlation calculating circuit continuously calculates cross-correlation values between the output of the first filter and the second filter, and uses this information to generate control values that are fed back to adjust the 90° phase shifter. This closed-loop feedback system enables accurate and continuous phase error detection and correction, overcoming the limitations of conventional open-loop methods.
2Reliability
If analog baseband filters are used in the receiver, then signal filtering is achieved, but variations in filter characteristics cause additional phase errors that reduce correction accuracy
Solution Approach 1:
The patent introduces a correlation calculating circuit as an intermediary between the analog baseband filters and the phase correction mechanism. This intermediary calculates the cross-correlation value between the filter outputs, which serves as a reliable indicator of phase error that is independent of filter characteristic variations. By using this intermediary measurement, the system can accurately detect phase errors even when filter characteristics vary, thereby maintaining high correction accuracy.
3Measurement precision
If cross-correlation calculation is used to detect phase errors, then detection accuracy is improved, but calculation complexity and processing time increase
Solution Approach 1:
The patent performs preliminary signal conditioning before correlation calculation by using analog baseband filters to pre-filter the signals in the analog domain. This preliminary filtering reduces the bandwidth and power of the signals before they reach the correlation calculating circuit, thereby reducing the computational complexity and processing time required for the cross-correlation calculation while maintaining detection precision.
Data Source
AI summary
According to one embodiment, a quadrature error compensating circuit for acquiring an in-phase component signal and a quadrature component signal, includes a first filter, a first multiplier, a first subtractor, a second filter, a correlation calculating circuit. The first multiplier multiplies the in-phase component signal by a control value. The correlation calculating circuit calculates a cross-correlation value between an output of the first filter and an output of the second filter, and uses the cross-correlation value as the control value.