Receiver AGC Gain Tables for Strong Blocker Distortion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional automatic gain control (AGC) systems in communication receivers struggle with non-constant amplitude modulation and strong blocker signals, leading to distortion and reduced signal-to-noise plus distortion ratio (SNDR), which necessitates increased complexity and cost in receiver design.
Innovation Solution
A communication system with multiple gain tables and a digital AGC circuit that adjusts gain stages based on coarse gain back-offs, selecting the appropriate gain table based on the presence and strength of blockers to optimize signal-to-noise ratio (SNR) and SNDR, allowing for reduced SNR to improve SNDR in stronger blocker conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single gain table optimized for SNR is used, then signal-to-noise ratio is maximized, but signal-to-noise plus distortion ratio deteriorates in the presence of strong blockers
Solution Approach 1:
The patent divides the single gain table into multiple gain tables, each optimized for different blocker conditions. The gain tables are segmented based on blocker strength scenarios, allowing the system to select the appropriate table for current conditions rather than using a single compromise table.
Solution Approach 2:
The patent changes the parameters of the gain tables based on detected blocker conditions. By monitoring signal characteristics and identifying blocker presence, the system adjusts which gain table parameters are applied, switching between tables optimized for different signal-to-blocker ratio conditions.
2Object-affected harmful factors
If multiple gain tables are added to handle different blocker conditions, then blocker performance improves, but device complexity increases
Solution Approach 1:
The patent performs preliminary detection of blocker conditions before selecting a gain table. By analyzing the received signal in advance to identify the presence and strength of blockers, the system pre-determines which gain table will be optimal, avoiding the need to evaluate multiple tables during signal processing.
Solution Approach 2:
The patent introduces an intermediary blocker detection mechanism that assesses signal conditions and mediates the selection between multiple gain tables. This intermediary layer simplifies the complexity by providing a clear decision criterion for table selection based on measured signal characteristics.
3Device complexity
If conventional AGC with single gain table is used, then circuit design is simpler, but receiver chain saturates more easily in presence of blockers
Solution Approach 1:
The patent makes the gain table selection dynamic rather than fixed. The system continuously monitors signal conditions and dynamically switches between different gain tables based on current blocker presence and strength, allowing the receiver to adapt to changing conditions and avoid saturation.
Solution Approach 2:
The patent implements feedback mechanisms that monitor receiver chain saturation conditions and signal characteristics. This feedback information is used to adjust gain table selection in real-time, preventing saturation by selecting appropriate gain tables before saturation occurs.
Data Source
AI summary
A communications receiver with improved blocker performance including multiple gain tables selected based on a number of reductions or back offs from a maximum coarse gain setting. A receiver chain with multiple gain stages converts a received signal to a digital format, determines the power level of the received signal, and provides an overload indication. A first gain table maximizes SNR and SNDR for weak blockers and at least one additional gain table successively improves SNDR for stronger blockers. An AGC circuit initially sets the coarse gain setting to maximum, and backs off a number of coarse gain steps until the receiver chain is not overloaded. The number of back off steps is used to select a gain table, the power level is used to select an entry in the selected table, and the selected entry includes gain settings for the gain stages of the receiver chain.