I/Q Receiver Gain Control With DC Offset and Phase Correction
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Solution Overview
Problem
Communication receivers face challenges in maintaining consistent signal amplitude due to unpredictable over-the-air channels and intra-receiver component variations, leading to decreased sensitivity and gain imbalances between I and Q channels, as well as issues with DC offsets and phase imbalances.
Innovation Solution
A digital gain control system that adjusts the gain of a variable gain amplifier based on signal statistics, incorporates a gain control loop that counts extreme codes to maintain constant power, corrects inter-channel gain imbalances, and includes DC offset and phase imbalance correction mechanisms using accumulators and multipliers to ensure optimal signal processing under adverse conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If automatic gain control is implemented using signal statistics, then gain control accuracy is improved, but device complexity increases due to additional digital processing requirements
Solution Approach 1:
The patent replaces traditional analog gain control mechanisms with a digital signal processing approach. A digital processor implements automatic gain control by analyzing signal statistics and generating control signals, substituting mechanical/analog components with digital logic and algorithms, thereby improving precision while managing complexity through software-based control.
Solution Approach 2:
The automatic gain control system uses the statistical characteristics of the received signal itself to determine the appropriate gain adjustment. The system serves itself by extracting signal power level information directly from the input signal and using this information to control its own gain, eliminating the need for external calibration or manual adjustment.
2Reliability
If inter-channel gain imbalance correction is applied, then receiver sensitivity is improved, but device complexity increases due to additional correction circuits
Solution Approach 1:
The patent combines multiple correction functions into a unified digital signal processing framework. Gain imbalance correction, DC offset correction, and phase imbalance correction are integrated into a single system that processes I and Q channel signals simultaneously, reducing overall device complexity by eliminating separate correction circuits for each function.
Solution Approach 2:
The digital signal processing system performs multiple correction functions using the same hardware resources. A single digital processor handles gain control, gain imbalance correction, DC offset correction, and phase imbalance correction, making the system multi-functional and reducing the need for dedicated circuits for each correction type.
3Measurement precision
If DC offset and phase imbalance correction are implemented simultaneously, then signal processing accuracy is improved, but computational complexity increases
Solution Approach 1:
The system performs DC offset correction before phase imbalance correction in the signal processing chain. By removing DC offsets first, the subsequent phase imbalance correction algorithm operates on cleaner signals with removed bias terms, simplifying the computational requirements of the phase correction stage and improving overall accuracy.
Solution Approach 2:
The patent divides the correction process into distinct stages: DC offset correction, gain imbalance correction, and phase imbalance correction. Each stage processes specific signal components separately, allowing algorithms to be optimized for each function and reducing the overall computational complexity compared to attempting all corrections simultaneously in a single algorithm.
Data Source
AI summary
Described herein is a method of automatic gain control and simultaneous digital correction of three types of variations in I/Q receivers: gain imbalance, phase imbalance, and DC offset. Three adaptation loops can operate simultaneously and use the output of an analog to digital converter (ADC) as their input, with the output driving digitally controllable analog components. With appropriate knowledge of signal statistics, the algorithm automatically optimally fills the ADC's full input signal range, providing an automatic gain control function and thus maximizing the signal-to-quantization-noise ratio. In so doing, it corrects gain imbalances between I and Q paths, while additional circuitry corrects DC offsets and phase imbalances.