Passive Intermodulation Correction Using Digital-RF Filter Weights
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Solution Overview
Problem
Existing communication systems face challenges in accurately estimating and mitigating passive intermodulation (PIM) interference caused by RF impairments in transmit and receive chains, which limits PIM cancellation performance and affects signal quality.
Innovation Solution
An estimation circuitry is employed to derive weights based on digital and RF signals, accounting for distortion effects in both transmit and receive chains, to generate a PIM correction signal that is used to subtract interference in the digital domain, improving signal quality by minimizing PIM distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional PIM cancellation methods are used, then some level of interference mitigation is achieved, but PIM cancellation performance is limited due to inaccurate estimation of distortion effects in transmit and receive chains
Solution Approach 1:
The patent replaces conventional simplified PIM estimation methods with a more sophisticated digital signal processing approach that uses filter weights to model distortion effects. The estimation circuitry employs digital filtering and mathematical modeling to accurately capture non-linear distortion characteristics in both transmit and receive chains, substituting simpler mechanical or analog estimation methods with precise digital computation.
Solution Approach 2:
The patent changes the estimation parameters by deriving filter weights that specifically characterize distortion effects in the transmit and receive chains. Instead of using fixed or simplified parameters, the system dynamically determines filter weights based on actual signal measurements, allowing accurate modeling of PIM interference across varying operating conditions and improving estimation precision.
2Reliability
If accurate PIM correction is implemented using filter weights derived from both digital and RF signals, then signal quality and SNR are improved, but the processing complexity and computational requirements increase
Solution Approach 1:
The patent introduces filter weights as an intermediary element that bridges the gap between raw digital and RF signals and the final PIM correction. These weights serve as a mathematical mediator that captures the complex distortion effects without requiring direct complex signal manipulation, thereby improving signal quality while managing processing complexity through efficient weight application.
Solution Approach 2:
The patent performs preliminary derivation of filter weights based on captured RF signals and digital signals before applying them to correct PIM interference. By pre-characterizing the distortion effects and storing the resulting filter weights, the system prepares correction parameters in advance, reducing real-time computational burden while maintaining high signal quality through accurate PIM cancellation.
Data Source
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AI summary
The present subject matter relates to an apparatus comprising an estimation circuitry configured to: receive a first set of one or more digital signals of transmitters of a communication system; capture a set of one or more radio frequency signals that have been generated from the first set of digital signals, the set of radio frequency signals being input of an antenna system of the communication system; derive based on the first set of digital signals and the corresponding set of radio frequency signals a set of weights related to a distortion effect caused by the generation of the radio frequency signals; weight a received second set of one or more digital signals using the set of weights, resulting in one or more filtered signals respectively; estimate using the filtered signals a correction signal indicative of an interference that is caused by a transmission of the second set of digital signals at a receiver of the communication system.