Receiver IQ Mismatch Compensation Using Frequency-Domain Estimation
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Solution Overview
Problem
Existing communication systems face challenges in accurately estimating and compensating for in-phase/quadrature (IQ) mismatch in direct conversion reception methods, leading to increased bit error rates and performance degradation, especially in systems without pilot signals and those with high sampling frequencies.
Innovation Solution
A receiver is designed to estimate and compensate for IQ mismatch using an unknown received signal, employing a mismatch estimator to convert amplified I and Q components into the frequency domain to calculate gain and phase mismatch values, and a mismatch compensator to adjust the signal based on these values, effectively handling time delays in broadband systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pilot signal-based mismatch estimation is used in OFDM systems, then mismatch estimation can be performed, but the method cannot be applied to systems without pilot signals and performance is degraded due to pilot signal estimation errors
Solution Approach 1:
The system uses the received signal itself (containing data symbols) to perform mismatch estimation, rather than relying on external pilot signals. The estimator processes the actual received signal through FFT and correlation operations to extract mismatch parameters directly from the signal content, enabling the system to be self-sufficient and applicable to various modulation schemes without requiring pilot signals.
Solution Approach 2:
The invention changes the estimation approach from pilot signal-based to data symbol-based by transforming the received signal into frequency domain and utilizing the statistical properties of modulated symbols. This parameter change enables mismatch estimation to work with any modulation type (QPSK, 16-QAM, etc.) without requiring specific pilot signal structures.
2Reliability
If mismatch compensation is performed using related art methods, then some mismatch can be compensated, but time mismatch occurring due to group delay difference in broadband systems is not processed
Solution Approach 1:
The system performs preliminary mismatch estimation and compensation before demodulation and detection. By estimating the mismatch parameters (gain imbalance and phase error) from the received signal and applying compensation in advance, the system prepares the signal for optimal processing, ensuring high reliability in both narrowband and broadband conditions.
Solution Approach 2:
The mismatch estimation and compensation is performed dynamically for each received signal block rather than being a fixed static correction. The system continuously estimates mismatch parameters from incoming signals and updates compensation values, allowing it to adapt to time-varying conditions including those in broadband systems with sampling frequency-induced time delays.
3Manufacturing precision
If analog circuit precision is increased to reduce mismatch, then mismatch is reduced, but cost of the analog circuit increases
Solution Approach 1:
The invention replaces the need for high-precision analog circuit design with a digital signal processing approach. Instead of relying on precise analog components (mixers, amplifiers, filters), the system uses digital mismatch estimation and compensation algorithms that operate on the digitized signal, substituting mechanical/analog precision requirements with computational correction.
Solution Approach 2:
The digital mismatch estimator and compensator act as an intermediary between the imperfect analog front-end and the digital processing stages. This intermediary digitally corrects the mismatch effects introduced by analog circuits, allowing standard-cost analog components to achieve high-performance results through digital correction.
Data Source
AI summary
A receiver includes a first mixer configured to provide an in-phase (I) component of a radio frequency (RF) signal to an I channel by down-converting the RF signal, a second mixer configured to provide a quadrature (Q) component of the RF signal to a Q channel by down-converting the RF signal, amplification means, arranged on the I and Q channels, configured to amplify the I and Q components, a mismatch estimator configured to convert the amplified I and Q components into a frequency domain, and estimate a gain mismatch value and a phase mismatch value on the basis of the converted components, and a mismatch compensator configured to compensate for mismatch of the received signal on the basis of the estimated gain and phase mismatch values.