Receiver Gain Control for Intermodulation Interference Mitigation
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Solution Overview
Problem
Conventional radios, particularly Land Mobile Radios, experience significant intermodulation interference when close to broadband or narrowband base station sites, leading to degraded performance and sensitivity due to high noise floors, especially exacerbated by broadband signals' high peak to average power ratio.
Innovation Solution
The system monitors demodulator performance metrics such as Bit Error Rate and modulation fidelity to detect intermodulation interference and adjusts the gain of variable attenuators or low noise amplifiers to optimize receiver performance, using an Automatic Gain Controller to converge to the best gain profile for improved sensitivity under interference conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If receiver gain is increased to improve sensitivity, then signal detection capability is improved, but intermodulation interference and noise floor increase
Solution Approach 1:
The patent implements dynamic gain adjustment by continuously monitoring demodulator performance metrics (BER, BDR, ASE) and automatically adjusting the receiver gain setting in response to detected interference conditions. This transforms the static gain control into a dynamic system that adapts to changing interference environments, allowing the receiver to optimize sensitivity while mitigating intermodulation products through real-time gain modulation.
Solution Approach 2:
The system employs feedback mechanisms by monitoring demodulator performance metrics and using this information to control gain adjustment. The performance metrics (Bit Error Rate, Block Drop Rate, Average Symbol Error) serve as feedback signals that indicate the presence of intermodulation interference, triggering automatic gain reduction to restore optimal receiver performance and maintain signal quality.
2Reliability
If conventional interference mitigation methods are used, then intermodulation performance is improved, but computational complexity increases
Solution Approach 1:
The patent replaces complex computational interference mitigation algorithms with a simpler control mechanism based on monitoring demodulator performance metrics and adjusting gain settings. Instead of using computationally intensive signal processing techniques to cancel or filter intermodulation products, the system uses a feedback-controlled gain adjustment mechanism that responds to performance degradation, significantly reducing computational complexity while maintaining effective interference mitigation.
Data Source
AI summary
Systems and methods for mitigating broadband and/or Intermodulation (“IM”) interference. The methods comprise: monitoring performance of at least one demodulator performance metric of a communication device; detecting when the communication device is under or will be under an influence of IM interference based on a performance of the at least one demodulator performance metric; determining an improved level of gain to be applied to (i) a variable attenuator of the communication device or (ii) a variable gain low noise amplifier of the communication device; and selectively adjusting an amount of gain being applied by the variable attenuator or variable gain low noise amplifier based on the improved performance achieved with new level of attenuation.