PIMD Cancellation via Power Series Kernel Subtraction
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Solution Overview
Problem
Passive intermodulation distortion (PIMD) products in wireless communication systems, caused by nonlinearities in passive components and nearby metal objects, limit the dynamic range and sensitivity of wireless networks, particularly in advanced technologies like LTE, leading to reduced cell coverage and increased network costs.
Innovation Solution
A method involving upsampling and time delaying baseband signals, estimating and subtracting PIMD products using power series kernels, and downsampling to cancel PIMD products, effectively reducing their impact on the uplink path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If passive components and metal contacts are used in the transceiver system, then the system structure is simple and cost-effective, but passive intermodulation distortion products are generated that limit dynamic range and sensitivity
Solution Approach 1:
The patent converts the harmful PIMD distortion into a beneficial signal processing task by modeling the distortion products using power series kernels and systematically canceling them through digital signal processing. The harmful nonlinear effects from metal contacts and passive components are transformed into predictable mathematical models that can be inverted and removed, turning the distortion problem into a solvable signal processing challenge.
Solution Approach 2:
The patent introduces digital signal processing algorithms as an intermediary between the physical transmission medium and the receiver. By inserting a mathematical model (power series expansion) as an intermediary representation of the distortion mechanism, the system can predict and cancel PIMD products before they degrade the received signal, effectively mediating the harmful interaction between passive components and received signals.
2Object-affected harmful factors
If feed-forward linearization is used to suppress IMD products from active components, then active distortion is reduced, but PIMD distortion from passive components remains unaffected
Solution Approach 1:
The patent creates a universal distortion cancellation framework that handles both active and passive intermodulation distortion through a unified power series modeling approach. While feed-forward linearization addresses active component distortion, this patent extends the solution to passive components by modeling their nonlinear behavior through power series kernels, making the distortion cancellation system versatile enough to handle multiple distortion sources with a single methodology.
3Measurement precision
If higher sensitivity and dynamic range are implemented in new technologies like LTE, then network performance improves, but PIMD levels become the limiting factor reducing cell coverage
Solution Approach 1:
The patent applies preliminary anti-action by predicting and canceling PIMD distortion products before they can degrade the received signal. Using power series kernels to model the distortion mechanism, the system proactively generates and subtracts estimated distortion products from the received signal, preventing the distortion from limiting the sensitivity and dynamic range that newer technologies like LTE are designed to achieve.
4Productivity
If more transceiver systems are deployed to improve network coverage, then network capacity increases, but network costs increase and PIMD interference accumulates
Solution Approach 1:
The patent implements feedback by using the received signal itself to generate and cancel the distortion products. The power series kernels are adapted based on the actual received signal characteristics, creating a feedback loop that continuously optimizes the distortion cancellation. This allows the system to maintain high sensitivity and dynamic range even in the presence of accumulated PIMD from multiple transceivers, enabling network expansion without proportional cost increases.
Data Source
AI summary
A method for diminishing passive intermodulation (PIM) is provided. The method comprises: upsampling an uplink baseband modulated signal; upsampling a downlink baseband modulated signal; determining a time delay for the upsampled downlink baseband modulated signal; time delaying the upsampled downlink baseband modulated signal by the determined time delay; estimating a third order PIM distortion (PIMD) product by filtering the time delayed, upsampled downlink baseband modulated signal with a third order power series kernel; generating a first filtered signal by subtracting the estimated third order PIMD product from the upsampled downlink baseband modulated signal; estimating a Nth order PIMD product by filtering the time delayed, upsampled downlink baseband modulated signal with a Nth order power series kernel; generating a nth filtered signal by subtracting the estimated Nth order PIMD product from the n−1th filtered signal; and downsampling the nth filtered signal.