Receiver Gain Partitioning for Blocker-Aware AGC Control
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Solution Overview
Problem
Conventional receiver systems face a tradeoff between linearity and signal-to-noise ratio due to finite linearity of frequency converters and filters, requiring external controllers or demodulators to adjust gain partitioning and manage interference from undesired signals, which complicates the system and reduces performance.
Innovation Solution
An automatic gain control loop within the receiver adjusts the gain distribution across stages using received signal strength indicators and comparators to optimize signal levels entering the filter, allowing continuous tradeoff between linearity and noise without external intervention, by varying the partitioning between pre and post-selectivity gains based on detected interference levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pre-selectivity gain is increased to improve signal-to-noise ratio, then signal quality improves, but linearity performance degrades due to distortion products from blockers
Solution Approach 1:
The patent implements dynamic gain partitioning where the pre-selectivity and post-selectivity gains are continuously adjusted based on the detected level of blocker signals. The controller monitors the output signal and automatically redistributes gain between amplifiers 110 and 140 to maintain optimal linearity while preserving signal-to-noise ratio, eliminating the need for fixed predetermined gain settings.
Solution Approach 2:
The system employs a feedback mechanism where the output signal from amplifier 140 is monitored to detect blocker levels and distortion products. This feedback information is used by the controller to automatically adjust the gain partitioning between the pre-selectivity and post-selectivity stages, creating a closed-loop system that adapts to varying interference conditions.
2Object-affected harmful factors
If pre-selectivity gain is reduced to improve linearity, then distortion products decrease, but signal-to-noise ratio deteriorates
Solution Approach 1:
The system dynamically adjusts the gain partitioning based on real-time detection of blocker levels. When blockers are present, the controller reduces pre-selectivity gain to maintain linearity; when blockers are absent or weak, the controller increases pre-selectivity gain to optimize signal-to-noise ratio. This dynamic adaptation allows the system to achieve both linearity and signal quality under different operating conditions.
Solution Approach 2:
The patent changes the operating parameters (gain values) of amplifiers 110 and 140 based on the detected signal conditions. The controller modifies the gain parameters dynamically to optimize the tradeoff between linearity and signal-to-noise ratio, rather than using fixed predetermined gain settings.
3Device complexity
If predetermined gain partitioning is used to simplify control, then system complexity is reduced, but adaptability to varying interference levels is lost
Solution Approach 1:
The system is self-regulating through an automatic gain control loop that continuously monitors the output signal for blocker levels and automatically adjusts the gain partitioning without external intervention. The controller within the receiver system independently manages the gain distribution between pre-selectivity and post-selectivity stages, making the system self-adaptive to varying interference conditions.
Solution Approach 2:
The automatic gain control employs feedback from the output signal monitoring to continuously adjust gain partitioning. The controller detects distortion products and blocker levels in the output signal and uses this feedback to automatically redistribute gain between amplifiers 110 and 140, providing adaptability without requiring external controllers or demodulators.
Data Source
AI summary
An automatic gain control loop disposed in a receiver is adapted to compensate for varying levels of out of band interference sources by adaptively controlling the gain distribution throughout the receive signal path. One or more intermediate received signal strength indicator (RSSI) detectors are used to determine a corresponding intermediate signal level. The output of each RSSI detector is coupled to an associated comparator that compares the intermediate RSSI value against a corresponding threshold. The take over point (TOP) for gain stages is adjusted based in part on the comparator output values. The TOP for each of a plurality of gain stages may be adjusted in discrete steps or continuously.