Wideband Quadrature Imbalance Compensation via Segmented Estimation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional quadrature modulators assume a constant phase error across the input signal frequency band, which is insufficient as the bandwidth increases, leading to variations in quadrature imbalance error, and fail to adequately address gain imbalance and local oscillator feed-through.
Innovation Solution
A wideband quadrature imbalance compensation system that uses inverse complex inputs to phase quadrature estimator filters to generate estimated quadrature modulator distortion, compares it with the true output to calculate residual error, and applies a least mean square algorithm to update filter coefficients for both the estimator and compensator, thereby pre-compensating for quadrature imbalance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a constant phase error assumption is used across the input signal frequency band, then the device complexity is reduced, but the manufacturing precision of quadrature imbalance compensation deteriorates as bandwidth increases
Solution Approach 1:
The patent divides the single wideband phase error compensation problem into multiple narrowband sub-problems by segmenting the frequency band. Each sub-band is processed independently with its own phase error estimation and compensation, transforming a complex wideband problem into multiple simpler narrowband problems that can be solved more accurately.
Solution Approach 2:
The patent transitions from a static constant phase error assumption to a dynamic frequency-dependent phase error model. The phase error is estimated separately for different frequency sub-bands and updated adaptively, allowing the compensation system to track and correct phase variations across the bandwidth dynamically rather than using a fixed constant value.
2Adaptability or versatility
If the input signal bandwidth is increased, then the adaptability of the communication system is improved, but the quadrature imbalance error varies more across the band, worsening the manufacturing precision
Solution Approach 1:
The patent segments the wide input signal bandwidth into multiple narrower frequency sub-bands. Each sub-band experiences less phase error variation, allowing for more accurate local phase error estimation and compensation. This segmentation enables the system to maintain high compensation precision even when the overall bandwidth is large.
Solution Approach 2:
The patent applies different phase error compensation parameters to different frequency sub-bands rather than using a uniform compensation across the entire bandwidth. Each sub-band receives localized optimization with its own estimated phase error characteristics, ensuring that the compensation is tailored to the specific conditions of each frequency region.
3Reliability
If real-time compensation is implemented, then the reliability of quadrature imbalance correction is improved, but the use of energy and device complexity increase
Solution Approach 1:
The patent segments the real-time compensation process into discrete frequency sub-band processing steps. By processing each sub-band separately and independently, the system can efficiently update only the necessary parameters for each band, reducing the overall computational energy requirement compared to processing the entire wideband signal as a single unit.
Solution Approach 2:
The patent implements partial real-time compensation by focusing on the most critical frequency sub-bands or updating parameters at optimized intervals rather than continuously for all parameters. This approach maintains sufficient real-time compensation reliability while reducing energy consumption by avoiding unnecessary full-system updates.
Data Source
AI summary
Compensating for wideband quadrature imbalance error by introducing inverse complex inputs to phase quadrature estimator filters to generate estimated quadrature distortion; summing estimator quadrature distortion with a delayed version of the actual complex input to obtain estimated quadrature output; comparing the output with the true output to obtain residual quadrature imbalance error; applying a least mean square to the inverse input and imbalance residual error to obtain an updated estimate of filter coefficients; updating the filter coefficients of the phase quadrature estimator; and updating the filter coefficients of a phase quadrature compensator with the filter coefficients of the phase quadrature estimator to obtain a quadrature output pre-compensated for quadrature imbalance error.