Shared AGC Loop Control for Demodulation and FFT Spectrum Analysis
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Solution Overview
Problem
In wireless communication systems operating in unlicensed bands, the increasing density of devices leads to overcrowding and interference, as existing signaling protocols are not designed to cooperate, causing service degradation and user dissatisfaction.
Innovation Solution
Implementing a system that shares a radio and an automatic gain control (AGC) loop between a wireless data demodulator and a spectrum analysis module, with features like a predetermined hold time for the AGC loop, digital variable gain amplifiers, and multiple AGC loops to manage gain adjustments and minimize interference, allowing simultaneous demodulation and spectrum analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single radio and AGC loop are shared between demodulator and spectrum analysis module, then device complexity and power consumption are reduced, but gain adjustments for demodulation may interfere with spectrum analysis measurements
Solution Approach 1:
The AGC loop dynamically switches between two operational modes: a fast attack mode for demodulation that quickly adjusts gain to track signal levels, and a frozen mode for spectrum analysis that holds gain constant to ensure measurement reliability. This dynamic behavior allows a single shared AGC loop to satisfy the conflicting requirements of both demodulation and spectrum analysis functions
Solution Approach 2:
The system periodically alternates between demodulation-oriented AGC adjustments and spectrum analysis-oriented gain freezing. During spectrum analysis measurement periods, the AGC loop is frozen to prevent gain changes from corrupting measurements. Between measurements, the AGC loop is active to maintain proper signal levels for demodulation. This periodic switching resolves the contradiction by temporal separation of conflicting requirements
2Speed
If the AGC loop responds quickly to signal level changes, then demodulation performance is improved, but spectrum analysis measurements become unreliable due to frequent gain adjustments
Solution Approach 1:
The AGC loop implements dynamic response characteristics by switching between fast attack mode during demodulation (where quick gain adjustments are needed) and frozen mode during spectrum analysis measurements (where gain stability is critical). This dynamic adaptability allows the system to achieve both fast response when needed and measurement precision when required
Solution Approach 2:
The system performs preliminary freezing of the AGC loop before spectrum analysis measurements begin, ensuring gain stability is established in advance. This preliminary action prevents any gain adjustments from occurring during the measurement window, guaranteeing measurement precision while allowing fast AGC response during non-measurement periods
3Reliability
If multiple separate radios are used for demodulation and spectrum analysis, then measurement reliability is maintained, but power consumption and device complexity increase
Solution Approach 1:
The patent merges the demodulation radio and spectrum analysis radio into a single shared radio, and combines two separate AGC loops into one shared AGC loop with multiple modes. This consolidation eliminates redundant hardware, reducing power consumption and device complexity while maintaining measurement reliability through intelligent mode switching that freezes the AGC loop during spectrum analysis measurements
Solution Approach 2:
The single shared radio and AGC loop are designed to perform multiple functions: demodulation with fast gain tracking, spectrum analysis with frozen gain, and transitional operations between these modes. The AGC loop's multi-functionality, achieved through configurable attack modes and freezing capability, allows it to serve both demodulation and spectrum analysis requirements without requiring separate dedicated hardware for each function
Data Source
AI summary
Systems and methods for sharing an AGC loop between a wireless data demodulator and a spectrum analysis module that operates simultaneously with the data demodulator. In one embodiment, a predetermined hold time prevents the AGC loop from changing gain too often, thereby allowing the spectrum analysis module to collect reliable data. In another embodiment, the hold time may be extended to coincide with a spectrum analysis event, such as a boundary of an FFT block. In still another embodiment, an FFT valid signal is provided such that collected FFT blocks can be designated as suspect and then subsequently processed accordingly.