Narrowband Receiver AGC Using Wideband Detection for Fast Attack
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Solution Overview
Problem
Conventional automatic gain control (AGC) systems in communication receivers face challenges with fast response times due to reduced selectivity in receiver front ends, leading to overloading from wideband signals and increased dynamic range exceeding the capabilities of cost-effective analog-to-digital converters (ADCs), especially in frequency hopped or time division multiple access systems.
Innovation Solution
An AGC system that utilizes both on-channel and wideband signal detectors to rapidly adjust gain, incorporating a wideband signal detector to provide fast gain control and an on-channel signal detector to ensure appropriate signal levels, with a controller managing gain adjustments based on both signal types to prevent overloading and ensure accurate signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional on-channel AGC systems are used to control receiver gain, then appropriate on-channel signal levels are established, but response time is too slow for rapid frequency changes or time slotted periods
Solution Approach 1:
The AGC system is segmented into two independent detectors: a wideband signal detector for fast response and an on-channel signal detector for precise on-channel level control. Each detector operates independently and feeds into the gain control mechanism, allowing the fast wideband detector to provide rapid initial response while the on-channel detector ensures accurate final signal levels.
2Ease of manufacture
If less selectivity is incorporated in receiver front ends and IF stages, then economic pressures are relieved and cost effective ADCs can be used, but front ends and later receiver stages may be overloaded by large wideband signals
Solution Approach 1:
The wideband signal detector performs preliminary detection of wideband signal levels before the signal reaches the ADC. Based on this early detection, the AGC system adjusts receiver gain in advance to prevent overloading conditions, allowing the use of cost-effective ADCs without sacrificing protection against wideband signal overload.
3Ease of manufacture
If less selectivity is incorporated in receiver front ends, then ADC dynamic range requirements are reduced, but additional time delays occur for on-channel AGC systems to operate
Solution Approach 1:
The detection function is segmented into wideband and on-channel components operating in parallel. The wideband detector provides immediate response without waiting for on-channel processing, eliminating the time delay while maintaining the ability to use cost-effective ADCs with reduced dynamic range requirements.
4Measurement precision
If conventional AGC systems operate primarily on on-channel signals, then accurate on-channel signal levels are maintained, but fast attack times cannot be achieved with rapid frequency changes
Solution Approach 1:
The wideband signal detector serves multiple functions: it provides fast attack time response for rapid frequency changes, detects wideband signal levels to prevent overloading, and operates independently of on-channel processing. This multi-functional detector enhances system adaptability while the on-channel detector maintains accurate signal level control.
Data Source
AI summary
An automatic gain control (AGC) system for a receiver and corresponding method facilitate AGC in a receiver. The automatic gain control system includes an on-channel signal detector 123 configured to provide an on-channel signal level indication corresponding to a narrow band on-channel signal and a wideband signal detector 121 configured to provide a wideband signal level indication corresponding to a wideband signal, where the wideband signal includes the narrow band on-channel signal. Further included is a controller 149 that is coupled to the wideband signal level indication and the on-channel signal level indication and that is configured to provide a gain control signal corresponding to the wideband signal level and one or more of a plurality of states of the receiver.