Receiver Gain Partitioning for Linearity and SNR Tradeoff
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Solution Overview
Problem
Conventional receiver systems face a tradeoff between linearity and signal-to-noise ratio due to fixed gain partitioning between pre- and post-selectivity gains, which is inadequate in managing varying levels of out-of-band interference.
Innovation Solution
An automatic gain control loop within the receiver dynamically adjusts the gain distribution between pre- and post-selectivity stages based on intermediate received signal strength indicators and comparator thresholds, allowing continuous tradeoff between linearity and noise without external controllers or demodulators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pre-selectivity gain is increased to improve signal-to-noise ratio, then signal amplification is improved, but linearity performance degrades due to increased distortion products from blockers
Solution Approach 1:
The patent implements dynamic gain partitioning where the pre-selectivity gain and post-selectivity gain are continuously adjusted based on real-time signal conditions. The controller monitors the output signal and automatically redistributes gain between amplifiers 110 and 140, transitioning from fixed predetermined partitioning to adaptive dynamic partitioning that responds to varying blocker levels and signal conditions.
Solution Approach 2:
The patent employs a feedback mechanism where the output signal from amplifier 140 is fed back to a controller that monitors signal quality and blocker presence. Based on this feedback, the controller automatically adjusts the gain distribution between the pre-selectivity and post-selectivity amplifiers, creating a closed-loop system that optimizes linearity while maintaining signal-to-noise ratio.
2Object-affected harmful factors
If pre-selectivity gain is reduced to improve linearity, then distortion products are reduced, but signal-to-noise ratio degrades due to insufficient signal amplification
Solution Approach 1:
The system dynamically adjusts gain partitioning based on real-time conditions. When blockers are present, pre-selectivity gain is reduced to improve linearity, and post-selectivity gain is increased to compensate for signal loss. This dynamic redistribution ensures that signal-to-noise ratio is maintained while achieving improved linearity performance.
Solution Approach 2:
The patent changes the operating parameters of the amplifiers by dynamically adjusting gain values. The controller modifies the gain parameters of amplifiers 110 and 140 based on monitored signal conditions, allowing the system to transition between different gain partitioning configurations to optimize both linearity and signal-to-noise ratio under varying conditions.
3Device complexity
If fixed predetermined gain partitioning is used to simplify receiver design, then device complexity is reduced, but adaptability to varying interference levels is insufficient
Solution Approach 1:
The patent implements a self-adjusting gain partitioning system where the receiver automatically monitors its own output signal and redistributes gain between amplifiers without external intervention. The controller within the receiver autonomously detects blocker presence and adjusts gain parameters, enabling the system to adapt to varying interference levels while maintaining relatively simple integration.
Solution Approach 2:
The controller in the patent serves multiple functions: it monitors output signal quality, detects blocker presence, determines optimal gain partitioning, and adjusts amplifier gains accordingly. This multi-functional approach allows the receiver to adapt to various interference conditions while using a single integrated control mechanism rather than separate specialized circuits.
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.