In-Service PIM Interference Cancellation in Transceiver Systems
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Solution Overview
Problem
Passive intermodulation (PIM) interference degrades the sensitivity of uplink receivers in wireless communication systems, particularly due to nonlinear junctions and external signals, and existing testing methods disrupt service and are not feasible post-installation.
Innovation Solution
A transceiver system with a multi-port filter, band-pass filter, and monitoring and cancellation circuit that models non-linearity to cancel intermodulation components between transmission and reception signals, using adaptive parameters to minimize interference, and employs digital pre-distortion techniques to linearize power amplifiers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If instrument-based PIM testing is performed during antenna installation, then PIM interference can be detected, but service is interrupted and the test is not feasible after installation
Solution Approach 1:
The system enables the base station to perform self-diagnosis of PIM interference using its own transmitted signal and receiver. The transceiver monitors its own operation by analyzing the received signal for intermodulation products, eliminating the need for external testing instruments and service interruption.
Solution Approach 2:
The system implements continuous feedback monitoring where the receiver detects PIM interference in real-time, and this information is fed back to the processor which then adjusts system parameters or notifies maintenance personnel, enabling ongoing detection without external testing.
2Measurement precision
If high-power two-tone signal is used for PIM testing, then PIM interference can be detected, but the test signal frequency band is not licensed to the service provider
Solution Approach 1:
The system uses the base station's own licensed transmission signal as the test stimulus, eliminating the need for external high-power two-tone signals in unlicensed bands. The receiver analyzes its own received signal for PIM products generated during normal licensed operation.
Solution Approach 2:
The transmitted signal serves dual purposes: normal communication function and PIM testing stimulus. The same licensed frequency band is used for both service provision and interference detection, eliminating the conflict between testing and licensing.
3Reliability
If passive intermodulation interference is present in the uplink frequency band, then receiver sensitivity is degraded, but existing cancellation methods are not feasible for in-service systems
Solution Approach 1:
The system implements continuous feedback monitoring where the receiver detects PIM interference in real-time during normal operation, and this information is fed back to the processor which then adjusts system parameters or notifies maintenance personnel, enabling ongoing detection without external testing.
Solution Approach 2:
The system transitions from static pre-installation testing to dynamic in-service monitoring, allowing PIM detection to adapt to changing environmental conditions and component degradation over time while the system remains operational.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Effectively mitigates PIM interference across different classes (Class-A, B, and C) by continuously monitoring and adapting to minimize interference, thereby maintaining receiver sensitivity and service integrity.
Implementation Method 1
Nonlinear junctions in degraded antenna components (e.g. connectors) and rusty objects near antenna 101 (e.g. metal fences) introduce passive-intermodulation (PIM) interference in the reverse direction
Implementation Method 2
a band-pass filter coupled to the antenna for receiving a sampled signal that includes intermodulation components between two or more of an external signal, the transmission signal and the reception signal
Implementation Method 3
The intermodulation cancellation circuit models non-linearity in the intermodulation components. In some embodiments, the non-linearity is modeled according to a polynomial function.
Implementation Method 4
an analog linearizer for providing pre-distorted RF signal
Implementation Method 5
a digital signal processor that receives the transmission signal to provide a pre-distorted transmission signal
Data Source
AI summary
A transceiver coupled to an antenna includes: (a) a multi-port filter having a bidirectional port coupled to the antenna, at least one input port and at least one output port; (b) a transmit datapath receiving a transmission signal and providing the transmission signal for transmission by the antenna through the multi-port filter, the transmit datapath being coupled to the input port of the multi-port filter; (c) a receive datapath receiving a reception signal from the antenna, the receive datapath being coupled to the output port of the multi-port filter; (d) a band-pass filter coupled to the antenna for receiving a sampled signal that includes intermodulation components between two or more of an external signal, the transmission signal and the reception signal; and (e) a monitoring and cancellation circuit receiving the transmission signal, the reception signal and the sampled signal to cancel the intermodulation components.