Wireless Receiver AGC Timing Control for OFDM Blocker Peaks
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Solution Overview
Problem
Conventional automatic gain control (AGC) circuits in wireless receivers face challenges when receiving weak signals in the presence of high peak-to-average ratio blockers, such as Wi-Fi signals, leading to signal loss or reduced performance due to contention between peak detectors and inappropriate gain settings.
Innovation Solution
A wireless receiver design incorporating a gain network, level detector, timing system, gain up disable circuit, and blocker strength detect circuit, which adjusts gain based on statistical information from the RF level detector to prevent gain increase during strong blocker signals and reduce gain during weak blocker signals, thereby improving signal reception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional AGC circuits use peak detectors to adjust gain in the presence of blocker signals, then the system attempts to capture desired weak signals, but the contention between RF and IF peak detectors causes AGC to chatter resulting in signal loss or reduced performance
Solution Approach 1:
The patent introduces a timing system as an intermediary between the peak detectors and the AGC circuit. This timing system measures the duration that peak detector outputs exceed thresholds and only triggers AGC gain adjustments when the exceedance duration meets specific criteria. This intermediary filtering mechanism prevents the AGC from responding to transient peaks, thereby eliminating chatter and improving both signal reception reliability and AGC stability.
2Object-affected harmful factors
If AGC is driven by real peak detector, then occasional peaks in OFDM signal trigger gain reduction, but this sets gain lower than necessary preventing reception of desired weak signals
Solution Approach 1:
The patent implements dynamic threshold-based timing analysis where the system evaluates not just the amplitude but the duration that peak detector outputs exceed predefined thresholds. By dynamically assessing whether peak exceedances are transient or sustained, the system distinguishes between harmful blocker peaks and legitimate signal variations, allowing appropriate gain adjustments that protect against blockers while maintaining weak signal reception capability.
3Reliability
If AGC is driven by RMS detection, then AGC sets gain higher than necessary causing front end saturation when receiving peaks of OFDM signal
Solution Approach 1:
The timing system serves as an intermediary that filters RMS detection outputs by evaluating the duration of threshold exceedances. This prevents the AGC from reacting to transient peak excursions that would cause saturation, while still maintaining sufficiently high gain levels for detecting weak signals. The timing-based filtering allows the system to benefit from RMS detection's overall signal level measurement capability while avoiding its tendency to over-amplify transient peaks.
4Reliability
If wireless receiver operates in presence of strong Wi-Fi blocker signal, then desired weak signal reception is attempted, but the high peak-to-average ratio of OFDM blocker causes inappropriate gain settings
Solution Approach 1:
The patent implements periodic timing window analysis where the system continuously monitors peak detector outputs over defined time windows and evaluates the duration of threshold exceedances within each window. This periodic assessment mechanism provides a more accurate representation of sustained signal levels versus transient peaks, enabling precise gain control decisions that accurately reflect the true signal strength even in the presence of high peak-to-average ratio blockers like Wi-Fi OFDM signals.
Data Source
AI summary
A wireless receiver including a gain network that adjusts a gain of a received wireless signal and provides an RF signal, a level detector that provides a level indication while a strength of the RF signal is at least an RF level threshold, a timing system that provides a timing value indicative of a total amount of time that the level indication is provided during a timing window, a gain up disable circuit that provides a gain up disable signal when the timing value reaches a low threshold, a blocker strength detect circuit that provides a gain down request signal when the timing value reaches a high threshold, and an AGC circuit that does not increase the gain of the gain network while the gain up disable signal is provided, and that allows a reduction of the gain of the gain network while the gain down request signal is provided.