Peak-Based AGC for ADC Range Control Under RF Interference
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Solution Overview
Problem
Existing receivers, such as GPS receivers, face inefficiencies in dynamic range utilization due to radio frequency interference, as traditional RMS-based automatic gain control circuits fail to maintain optimal gain when interference is present, leading to suboptimal performance.
Innovation Solution
A method and system that estimate the peak-to-average ratio of analog signals from digital samples to determine a peak value, allowing the automatic gain control circuit to adjust the gain and maintain the signal magnitude at the analog-to-digital converter, effectively controlling the receiver's operating range and detecting narrow band interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If RMS-based AGC circuit is used to maintain constant RMS voltage at ADC input, then the dynamic range of ADC is efficiently utilized when only desired signal is present, but the dynamic range utilization deteriorates when RF interference is present
Solution Approach 1:
The patent changes the control parameter from RMS voltage to peak voltage. The AGC circuit now maintains constant peak voltage at the ADC input by detecting the peak value of the combined signal and adjusting gain accordingly. This parameter change allows the system to differentiate between desired signal peaks and interference peaks, improving dynamic range utilization in interference environments while maintaining efficiency in clean environments.
2Object-affected harmful factors
If RMS-based AGC circuit reduces gain to maintain constant RMS amplitude, then the combined RMS amplitude of desired signal and RF interference is kept constant, but the gain reduction causes loss of desired signal information
Solution Approach 1:
The patent applies local quality by making the AGC response selective to different signal components. Instead of uniformly responding to all signal energy (as RMS does), the peak-based AGC selectively responds to peak excursions. This allows the system to control the peak amplitude of the combined signal without uniformly reducing gain, thereby preserving desired signal information while still managing the overall signal level to prevent ADC saturation.
3Adaptability or versatility
If high SQNR is required to handle high magnitude RF interference, then the receiver can process interference, but the requirement of high SQNR becomes infeasible and dynamic range is not optimally utilized
Solution Approach 1:
The patent introduces dynamic adaptation through peak-based AGC that continuously monitors and adjusts gain based on instantaneous peak values. This dynamic control allows the receiver to adapt to varying interference conditions in real-time, maintaining optimal operating points for the ADC. The system can handle high magnitude interference by dynamically reducing gain when peaks occur, rather than requiring consistently high SQNR, thus reducing the infeasible SQNR requirement while maintaining adaptability.
Data Source
AI summary
Automatic gain control in a receiver. A method for controlling operating range of an analog-to-digital converter (ADC) by an automatic gain control circuit includes estimating a peak-to-average ratio corresponding to an analog signal from digital samples of the analog signal. The method includes determining a peak value corresponding to the analog signal based on the peak-to-average ratio. Further, the method includes maintaining magnitude of the analog signal at an input of the ADC and gain of the receiver based on the peak value.