Receiver Gain Control Using Statistical CNR Feedback
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Solution Overview
Problem
Conventional automatic gain control methods in communication systems are overly sensitive to noise and lack adaptability, leading to transient instability and difficulty in optimizing gain settings for optimal performance due to their direct and linear feedback mechanisms.
Innovation Solution
The implementation of a communication receiver with a variable gain amplifier and an automatic gain controller that uses Statistical Process Control (SPC) and fuzzy logic to monitor system performance parameters like carrier-to-noise ratio (CNR), adjusting gains non-linearly to maintain optimal performance by employing Shewhart control charts and look-up tables.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If direct feedback mechanism is used to control gain, then gain adjustment speed is improved, but system stability deteriorates due to transient instability with ill-behaved inputs
Solution Approach 1:
The patent introduces an intermediary statistical process control mechanism between the input signal and the gain control. Instead of directly responding to instantaneous signal values, the system uses statistical metrics (mean, standard deviation, skewness, kurtosis) calculated over a window of recent samples as intermediaries to determine gain adjustments. This filtering through statistical analysis prevents direct transmission of noise spikes and ill-behaved inputs to the gain control loop, maintaining stability while still enabling responsive adjustment.
2Measurement precision
If conventional automatic gain control is used, then noise sensitivity is improved through direct monitoring, but adaptability to different signal conditions deteriorates
Solution Approach 1:
The patent changes the parameters used for gain control from simple instantaneous signal levels to comprehensive statistical parameters including mean, standard deviation, skewness, and kurtosis. These statistical parameters provide a more complete characterization of signal conditions, enabling the system to adapt to different types of inputs (Gaussian noise, impulsive noise, skewed distributions) while maintaining precise monitoring capabilities. The look-up table maps these multi-dimensional statistical parameters to appropriate gain settings, achieving both precision and adaptability.
3Device complexity
If linear feedback function is used for gain control, then control simplicity is improved, but performance optimization deteriorates due to inability to handle non-linear relationships
Solution Approach 1:
The patent creates a copy of the statistical characteristics of the input signal through calculated metrics (mean, standard deviation, skewness, kurtosis) and uses this statistical copy to drive the gain control. Instead of directly applying linear feedback to the raw signal, the system copies the essential statistical features and uses pre-computed look-up tables that map these statistical copies to optimal gain values. This approach maintains relative simplicity while achieving non-linear optimization performance.
Data Source
AI summary
In a communication receiver having a variable gain amplifier and an automatic gain controller, the automatic gain controller is operable to measure values of a system performance parameter indicative of the performance of the communication system, determine a statistical value of the system performance parameter, and adjust the variable gain of the amplifier in response to the statistical value to maintain the statistical value in a control range.