Wideband RF Receiver I/Q Correction Using Joint Polynomial Estimation
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Solution Overview
Problem
Existing signal processing algorithms in direct down conversion receivers and low-IF receivers face challenges in accurately estimating and compensating for both frequency-dependent and frequency-independent I/Q mismatches, which are exacerbated by environmental changes and system imperfections, leading to suboptimal performance in IQ-based signal processing.
Innovation Solution
A quadrature error correction (QEC) method that jointly estimates and compensates for both frequency-dependent and frequency-independent mismatches using a discrete-time signal model, incorporating a QEC circuit with a windowing circuit, FFT block, statistics generator, and polynomial estimation block to calculate and correct for channel mismatches in real-time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional methods are used to estimate frequency-independent mismatch, then the frequency-independent phase mismatch caused by LO can be compensated, but the estimation produces invalid results due to the existence of frequency-dependent mismatch
Solution Approach 1:
The patent segments the mismatch estimation problem into two independent components: frequency-independent mismatch (caused by LO) and frequency-dependent mismatch (caused by analog baseband channel). By using separate estimation algorithms for each type - a pilot-based method for frequency-independent mismatch and a signal-based method for frequency-dependent mismatch - the patent avoids the interference that occurs when trying to estimate both types simultaneously with a single algorithm, thereby producing valid estimation results for both.
Solution Approach 2:
The patent performs preliminary estimation of frequency-independent mismatch using pilot signals before processing the actual data signals. This preliminary action allows the system to compensate for LO-induced mismatch in advance, ensuring that subsequent estimation of frequency-dependent mismatch using data signals is not contaminated by frequency-independent errors, thus guaranteeing estimation validity.
2Measurement precision
If separate compensation methods are used for frequency-independent and frequency-dependent mismatches, then each type can be compensated differently, but the overall system complexity increases
Solution Approach 1:
The patent implements a unified quadrature error correction (QEC) architecture that handles both frequency-independent and frequency-dependent mismatches through a single integrated processing chain. The QEC circuit performs both types of compensation sequentially using different algorithms appropriate for each mismatch type, providing multi-functional capability within one system structure. This approach achieves accurate compensation for both mismatch types while avoiding the need for completely separate processing systems, thus controlling overall complexity.
3Adaptability or versatility
If real-time tracking of I/Q mismatch is implemented to account for environmental changes, then the compensation remains accurate under varying conditions, but the computational load and processing time increase
Solution Approach 1:
The patent implements periodic re-estimation of mismatch parameters using pilot signals at predetermined intervals rather than continuous estimation. This periodic action allows the system to track environmental changes and update compensation parameters at appropriate frequencies while avoiding excessive computational burden. The system balances adaptability to environmental changes with processing efficiency by updating mismatch estimates only when necessary, based on pilot signal analysis.
4Measurement precision
If advanced signal processing algorithms are used to compensate for both types of mismatches, then the compensation performance improves, but the convergence time increases
Solution Approach 1:
The patent performs preliminary estimation and compensation of frequency-independent mismatch using pilot signals before processing data signals. This preliminary action removes the dominant source of mismatch early in the processing chain, allowing subsequent estimation of frequency-dependent mismatch to converge faster. By addressing the larger frequency-independent errors first, the system reduces the overall convergence time while maintaining high compensation performance.
Solution Approach 2:
The patent segments the compensation process into two sequential stages: first compensating frequency-independent mismatch using pilot-based estimation, then compensating frequency-dependent mismatch using signal-based estimation. This segmentation allows each algorithm to focus on its specific mismatch type with optimized convergence characteristics, avoiding the prolonged convergence that would result from attempting to estimate both mismatch types simultaneously with a single complex algorithm.
Data Source
AI summary
A receiver apparatus models and corrects the frequency-dependent and the frequency-independent mismatches between I and Q paths jointly by polynomial estimations. The receiver apparatus may sample digitized I and Q path signals. The sampled data point may be modeled in equations with real and imaginary components. The sampled discrete time-domain data may be converted to frequency-domain data. Multiple statistics values based on the frequency-domain data may be computed. Coefficients for the polynomial equations may be estimated based on the computed statistic values. The channel mismatches may be estimated from the polynomial equations and used to compensate the mismatch either on the I path or the Q path.