Multi-Source PIM Cancellation Using Calibrated CFR Signals
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Solution Overview
Problem
Passive intermodulation (PIM) interference degrades receiver sensitivity in communication systems, particularly in base stations and satellite systems, due to non-linear responses of passive components, leading to signal degradation and increased noise.
Innovation Solution
Implementing a base station with a receiver and processing device that calibrates crest factor reduction (CFR) output signals to generate a non-linear actuation (NA) input signal, using PIMC coefficients to cancel intermodulation distortion through a PIMC control path, enhancing receiver sensitivity by reducing PIM from multiple sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If passive components are used in the receiver path, then device complexity is reduced, but passive intermodulation distortion increases degrading receiver sensitivity
Solution Approach 1:
The patent generates an artificial PIM signal using the same non-linear passive components that cause harmful PIM distortion, then uses this artificial signal to create a cancellation signal that subtracts the harmful PIM from the received signal. The harmful non-linearity is converted into a useful reference for cancellation.
Solution Approach 2:
An artificial PIM signal is generated as an intermediary that mimics the characteristics of the harmful PIM distortion. This intermediary signal serves as a template for creating the cancellation signal, allowing the system to eliminate the harmful PIM without removing the passive components.
2Object-affected harmful factors
If multiple PIM sources are present in the Rx band, then receiver sensitivity degrades further, but identifying and canceling each source increases processing complexity
Solution Approach 1:
The patent separates the cancellation process into distinct segments: one segment generates cancellation signals for internal PIM sources using the CFR output, while another segment handles external PIM sources using the diagnostic receiver. Each PIM source is addressed by a dedicated cancellation path.
Solution Approach 2:
The processing device is designed with multi-functionality to handle both internal and external PIM sources through a unified PIMC architecture. The same processing device performs calibration, signal generation, and cancellation for multiple PIM sources, reducing overall system complexity despite the multiple sources.
3Measurement precision
If PIMC calibration is performed to match CFR output signal to Rx output signal, then PIM cancellation accuracy improves, but calibration time and processing overhead increase
Solution Approach 1:
The patent performs PIMC calibration in advance during system initialization or maintenance periods, storing the calibration parameters for later use. This preliminary calibration action allows the system to operate with high PIM cancellation accuracy without requiring continuous calibration during normal operation.
Data Source
AI summary
A system includes a receiver (RX) configured to receive an RX output signal in an RX band, where the RX output signal has a first passive intermodulation (PIM) source in the RX band and a second PIM source in the RX band; and a processing device configured to: receive the RX output signal from the receiver on an RX path, receive a crest factor reduction (CFR) output signal from a CFR on a transmit (TX) path, identify the first PIM source and the second PIM source based on the RX output signal and the CFR output signal, calibrate the CFR output signal based on the first and second PIM sources in the RX output signal to generate a non-linear actuation (NA) input signal, and generate an intermodulation distortion signal by using an NA function on the NA input signal.