Wireless Receiver AGC Using ADC Variance for Stable Demodulation
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Solution Overview
Problem
Ultra low power (ULP) wireless receivers face challenges in maintaining signal quality due to high variations in received signal power caused by multipath and shadowing effects, leading to saturation and low signal-to-noise ratio (SNR) issues, which affect demodulation in applications like body area networks and wireless sensor networks.
Innovation Solution
A method and apparatus for automatic gain control (AGC) in ULP wireless receivers, where an energy detection circuit computes variance in the output signal of an analog-to-digital converter (ADC) and activates an AGC circuit to adjust the gain of components in a radio frequency integrated chip (RFIC) based on signal-to-noise ratio (SNR) and output power, ensuring the signal remains close to a target power level, preventing clipping and ensuring successful demodulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple variable gain stages are used in the ULP wireless receiver, then the signal-to-noise ratio (SNR) and amplitude variation are improved, but the device complexity and power consumption increase
Solution Approach 1:
The patent extracts the AGC functionality into a separate, dedicated circuit block that operates independently from the main signal path. This extraction allows the complex gain control logic to be isolated, enabling simpler integration with the ADC and reducing overall system complexity while maintaining multiple gain stages for SNR improvement
Solution Approach 2:
The patent implements a feedback mechanism where the AGC circuit continuously monitors the ADC output signal levels and automatically adjusts the gain of variable gain stages. This closed-loop feedback system maintains optimal SNR and amplitude variation without requiring complex manual configuration or multiple observation points, thereby improving reliability while managing device complexity
2Measurement precision
If multiple observation points are used for AGC operation, then the gain control accuracy is improved, but the processing complexity and convergence time increase
Solution Approach 1:
The patent segments the AGC measurement process into distinct functional blocks: an energy detection circuit that measures signal energy, a variance computation unit that calculates signal variations, and a gain control unit that applies corrections. This segmentation allows accurate gain control through multiple measurement aspects while reducing processing complexity by distributing functions across specialized circuits rather than requiring centralized complex processing of multiple observation points
3Reliability
If the variable gain stages are incorrectly set, then the demodulation success rate decreases, but the power consumption increases due to frequent adjustments
Solution Approach 1:
The patent implements preliminary action by having the AGC circuit perform gain adjustments during the preamble period before actual data demodulation begins. The energy detection and variance computation occur during this initial phase, allowing the system to converge on optimal gain settings in advance. This preliminary adjustment ensures accurate demodulation from the start while minimizing the need for frequent power-consuming adjustments during data reception
Solution Approach 2:
The patent employs periodic action where the AGC circuit performs measurements and adjustments at regular intervals rather than continuously. The energy detection circuit samples the ADC output at periodic intervals, computes variance over defined windows, and updates gain settings periodically. This periodic operation maintains reliable demodulation by catching signal level changes while significantly reducing power consumption compared to continuous adjustment mechanisms
Data Source
AI summary
Examples provide a method of performing automatic gain control (AGC) in a wireless receiver, the method including computing, by an energy detection (ED) circuit, a variance in an output signal of an analog-to-digital converter (ADC), and activating, by the ED circuit, an AGC circuit to adjust a gain of at least one component in a radio frequency integrated chip (RFIC) in response to the variance exceeding a threshold. Examples also provide for a wireless receiver that implements such a method.