I/Q Receiver Correction Loops for Gain, Phase, and DC Offset
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Solution Overview
Problem
Communication receivers face challenges in DC offset correction and gain imbalance due to component mismatches and unpredictable signal amplitudes, leading to reduced sensitivity and maximum signal handling capability.
Innovation Solution
A method involving digital gain control and DC offset correction loops that count extreme codes from the ADC output to adjust VGA gain and compensate for DC offsets, along with phase imbalance correction using orthogonal operations and accumulators to maintain signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DC offset correction and gain control are implemented using conventional methods, then receiver sensitivity and signal handling capability can be maintained, but the device complexity increases due to requiring analog power detectors and calibration periods
Solution Approach 1:
The patent extracts and eliminates the analog power detector and calibration period from the conventional receiver architecture. Instead of using traditional analog components for DC offset correction and gain control, the invention implements these functions digitally through processing of ADC output codes, thereby removing the need for complex analog circuitry and calibration mechanisms while maintaining receiver reliability
Solution Approach 2:
The patent replaces the mechanical/analog system (analog power detectors and calibration periods) with a digital system. By using digital signal processing techniques that analyze ADC output code distributions, the invention achieves DC offset correction and gain control through software/algorithms rather than physical analog components, reducing device complexity
2Ease of manufacture
If component mismatches are present in the receiver, then manufacturing is simplified, but DC offset errors and gain imbalances increase leading to reduced performance
Solution Approach 1:
The patent implements a self-correcting system that automatically compensates for component mismatches without requiring precision manufacturing. The digital processing algorithm analyzes the statistical distribution of ADC output codes and automatically adjusts for DC offsets and gain imbalances caused by component variations, allowing the receiver to self-correct manufacturing tolerances without additional precision requirements
Solution Approach 2:
The invention employs feedback mechanisms where the digital processor continuously monitors ADC output code distributions and uses this information to adjust and correct DC offset and gain errors. This closed-loop feedback system compensates for component mismatches in real-time, maintaining manufacturing precision without increasing manufacturing complexity
Data Source
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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.