Direct Conversion Receiver IQ Imbalance Correction Without Preambles
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Solution Overview
Problem
Direct conversion receivers in communication systems face amplitude and phase imbalance issues due to temperature dependencies and production imperfections, leading to degraded reception performance, particularly in two-way radios that do not use preamble signals, and existing methods like HOS techniques are computationally intensive and unsuitable for embedded platforms.
Innovation Solution
A two-parameter adaptive system within the direct conversion receiver estimates and corrects amplitude and phase imbalance errors by updating initial imbalance parameter values based on the error between average envelopes of DC offset corrected signals, without requiring training sequences or HOS techniques, using a block diagram and algorithm that iteratively minimizes the error to achieve balanced I and Q signal components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If training sequences or preamble signals are used to estimate and correct amplitude and phase imbalance, then the correction accuracy is improved, but the device complexity and difficulty of implementation increase significantly
Solution Approach 1:
The system uses the received signal itself to estimate and correct imbalance errors without requiring external training sequences or preamble signals. The correction algorithm processes the actual communication signal to adaptively estimate imbalance parameters and apply corrections, making the system self-sufficient and avoiding additional hardware/software complexity
Solution Approach 2:
The patent extracts the imbalance estimation function from the signal processing chain by using statistical properties of the received signal directly. Instead of relying on dedicated training sequences, the method extracts imbalance information from the signal envelope and phase characteristics, eliminating the need for separate training signal transmission and processing hardware
2Measurement precision
If HOS techniques are used to estimate amplitude and phase imbalance errors, then the estimation capability is improved, but the computational complexity increases making it infeasible for embedded platforms
Solution Approach 1:
The patent changes the estimation approach from high-order statistics to a simpler second-order statistics-based method. By using the envelope of the received signal and its statistical properties, the algorithm achieves adequate imbalance estimation with significantly reduced computational complexity suitable for embedded platforms
Solution Approach 2:
The method uses a simplified estimation approach that captures the essential imbalance characteristics without requiring full HOS processing. By focusing on the dominant statistical properties of the signal envelope, the system achieves sufficient correction accuracy with manageable computational requirements
3Measurement precision
If HOS techniques are used for imbalance estimation, then the estimation accuracy is improved, but the ease of operation deteriorates due to assumptions about signal sources
Solution Approach 1:
The patent develops a universal imbalance correction method that works across different signal types and modulation schemes without requiring specific assumptions about signal sources. The envelope-based statistical approach is applicable to various communication modes including analog FM and digital modulations, making the system versatile and broadly applicable
Data Source
AI summary
A communication system comprises a direct conversion receiver for correcting imbalance errors. The direct conversion receiver receives a radio frequency (RF) signal and converts the RF signal to baseband signals. The direct conversion receiver further translates the baseband signals to digital signals having a direct current (DC) offset and applies a DC offset correction to the digital signals having the DC offset to generate first DC offset corrected signals. An imbalance correction unit of the direct conversion receiver applies an imbalance correction to the first DC offset corrected signals by estimating an error between an average envelope of the first DC offset corrected signals and an average envelope of second DC offset corrected signals. The imbalance correction unit is fixed at initial imbalance parameter values. The direct conversion receiver further updates the initial imbalance parameter values of the imbalance correction unit based on the estimated error for correcting imbalance errors.