Receiver AGC Using Phase-Aligned Samples to Preserve Detection Margin
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Solution Overview
Problem
Existing automatic gain control (AGC) techniques in communication systems, particularly in receivers, face limitations when dealing with over-equalized signals, leading to reduced signal gain and loss of detection margin, as they rely on signal envelope detection rather than samples taken at a desired sampling phase and target voltage.
Innovation Solution
The method adjusts receiver gain by obtaining samples at a desired sampling phase and target voltage level, using a comparison such as an exclusive OR function to determine if the signal amplitude is equal to the target voltage, and making average gain updates based on these samples to maintain optimal signal levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If envelope-based AGC techniques are used to adjust receiver gain, then the ability to maintain desired signal levels is improved, but signal detection margin is lost when the receiver input signal is over-equalized
Solution Approach 1:
The patent replaces the analog envelope detection mechanism with a digital sampling and comparison mechanism. Instead of using analog rectification and averaging circuits to detect signal envelope, the invention uses digital latches to sample the signal at specific phases and compares these samples against reference voltage levels, thereby substituting mechanical/analog detection with digital processing to achieve more precise control without losing detection margin
Solution Approach 2:
The invention changes the fundamental parameter being measured from signal envelope amplitude to signal phase-aligned sample values. By sampling at specific phases (e.g., center of unit interval) and comparing against reference voltages, the system transforms the measurement parameter to achieve both reliable level maintenance and preserved detection margin, resolving the contradiction between these two requirements
2Ease of operation
If gain control is based on signal envelope detection, then overall receiver gain can be adjusted, but gain compression occurs and signal detection margin is reduced
Solution Approach 1:
The patent replaces the analog envelope detection mechanism with a digital sampling and comparison mechanism. Instead of using analog rectification and averaging circuits to detect signal envelope, the invention uses digital latches to sample the signal at specific phases and compares these samples against reference voltage levels, thereby substituting mechanical/analog detection with digital processing to achieve more precise control without losing detection margin
Solution Approach 2:
The system uses the signal's own phase information and voltage samples to automatically determine the appropriate gain adjustment. By sampling at the desired phase and comparing with reference voltages, the system self-regulates the gain without external intervention, maintaining detection margin while achieving ease of operation through automatic control
Data Source
AI summary
Methods and apparatus are provided for automatic gain control in a receiver using samples taken at a desired sampling phase and target voltage level. The gain of a received signal is adjusted by obtaining a plurality of samples of the received signal substantially at a desired sampling phase (such as a center of a given unit interval), wherein at least one of the samples is taken substantially at a target voltage level; comparing the plurality of samples to determine whether the received signal has an amplitude that is substantially equal to the target voltage level; and adjusting a receiver gain based on whether the received signal amplitude is substantially equal to the target voltage level. The comparison can comprise the evaluation of a logic function, such as an exclusive OR function. The comparison can be performed over a plurality of samples to obtain an average gain update decision. The receiver gain can be adjusted based on a histogram of the average gain update decision, relative to a predefined threshold.