FMCW Radar IQ Mismatch Correction Across Chirped LO Frequencies
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Solution Overview
Problem
FMCW radar systems face performance degradation due to IQ mismatches between in-phase and quadrature channels, especially with the shift to Si-based CMOS radar integrated circuits, leading to image band fold-back and degraded performance across wide RF frequency bands.
Innovation Solution
A dynamic IQ mismatch correction method that generates phase and gain correction parameters based on the slope rate of the chirped LO signal, applied during each interval of the chirp, to correct for time-varying IQ mismatches using a dynamic correction parameter generator and IQ mismatch correction circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If static correction parameters are used for IQ mismatch correction, then the device complexity is reduced, but the image rejection ratio deteriorates by nearly 30 dB across wide RF frequency bands
Solution Approach 1:
The patent implements dynamic correction parameters that vary with the instantaneous frequency of the chirped LO signal. The correction parameters are generated dynamically based on the slope rate of the chirped LO signal, allowing the system to adapt to frequency-dependent IQ mismatches across the wide RF bandwidth, thereby achieving high image rejection ratio without requiring overly complex static correction circuits
Solution Approach 2:
The patent changes the correction parameters (phase and gain) based on the frequency slope rate of the chirped LO signal. By generating different correction parameter values during different intervals of the chirp, the system optimizes image rejection at each instantaneous frequency point, resolving the contradiction between simple correction circuits and high image rejection performance
2Ease of manufacture
If Si-based CMOS radar integrated circuits are used, then the manufacturing cost and ease of manufacture are improved, but IQ mismatch increases leading to degraded performance
Solution Approach 1:
The patent implements a self-correcting system where the radar dynamically generates and applies correction parameters based on its own operating conditions (chirped LO signal slope rate). This self-service approach compensates for the inherent IQ mismatches introduced by Si-based CMOS manufacturing variations, maintaining reliable radar performance without requiring manual calibration or more expensive manufacturing processes
Solution Approach 2:
The system uses feedback from the chirped LO signal characteristics to dynamically adjust the correction parameters. By monitoring the slope rate of the chirped LO signal and generating corresponding correction parameters, the system continuously compensates for IQ mismatches, ensuring reliable performance despite manufacturing variations in Si-based CMOS circuits
Data Source
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AI summary
In described examples, an FMCW radar receiver (100) includes a LO (102) providing a chirped LO signal (103), an in-phase (I) channel for outputting I-data and a quadrature (Q) channel for outputting Q-data. A dynamic correction parameter generator (140) generates IQ phase correction values (P[n]s) and IQ gain correction values (G[n]s) based on a frequency slope rate of the chirped LO signal (103) for generating during intervals of chirps including a first sequence of P[n]s and G[n]s during a first chirp and a second sequence of P[n]s and G[n]s during a second chirp. An IQ mismatch (IQMM) correction circuit (130) has a first IQMM input coupled to receive the I-data and a second IQMM input receiving the Q-data, and the P[n]s and G[n]s. During the first chirp, the IQMM correction circuit provides first Q'-data and first I'-data. During the second chirp, the IQMM correction circuit provides at least second Q'-data and second I'-data.