PIM Detection Using Time Delay and FFT Analysis
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Solution Overview
Problem
Conventional methods for detecting passive intermodulation (PIM) generation points in in-building feeders are inaccurate, leading to prolonged replacement times and increased maintenance costs due to the inability to precisely locate dysfunctional elements causing interference between upward and downward channels.
Innovation Solution
The introduction of a time delay module at the output end of the reference signal, controlled by a time delay control module, enhances detection accuracy by performing Fast Fourier Transform (FFT) on beat frequency signals to calculate the PIM generation point with precision up to 10 centimeters, allowing for rapid replacement and repair of faulty elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional digital signal processing is used to estimate PIM generation point, then the detection can be performed, but the accuracy is only several meters which is insufficient for precise localization
Solution Approach 1:
The patent introduces a time delay module that varies the time delay parameter of the reference signal to create multiple virtual signal sources. By changing the time delay parameter and performing FFT analysis at different delay values, the system achieves fine-grained distance measurement with 10 cm accuracy, resolving the contradiction between measurement precision and time loss.
2Productivity
If multiple candidate PIM generation points are estimated due to limited accuracy, then the detection process is simple, but the replacement or repair of dysfunctional elements takes too much time
Solution Approach 1:
The patent uses FFT analysis to rapidly process the delayed reference signal and PIM signal, quickly identifying the beat frequency and calculating the PIM generation point distance. This mathematical transformation method allows the system to skip through multiple measurement iterations and directly compute the precise location, thereby increasing productivity without sacrificing measurement precision.
3Ease of manufacture
If a common in-building feeder is used for multiple frequency bands, then construction cost is reduced, but passive intermodulation occurs causing interference between channels
Solution Approach 1:
The patent implements a self-diagnosis system that automatically detects and locates PIM generation points within the in-building feeder system. By using the existing common feeder infrastructure and adding only a detection apparatus, the system enables autonomous identification of dysfunctional elements, allowing maintenance personnel to quickly locate and repair the specific components causing interference without needing to redesign the entire feeder system.
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
This solution significantly improves the accuracy of PIM generation point detection, reducing maintenance time and costs, and enhances mobile service range and telephone connection efficiency by promptly resolving PIM-related issues.
Implementation Method 1
a time delay module configured to delay, according to a time delay amount control value, a reference signal based on a frequency modulation continuous wave (FMCW) signal and a continuous wave (CW) signal, or a PIM signal output from an in-building feeder
Implementation Method 2
a signal processing result obtained by performing a Fast Fourier Transform (FFT) on a beat frequency signal based on a signal which is delayed by the time delay module among the PIM signal and the reference signal and the other signal which is not delayed signal among the PIM signal and the reference signal
Implementation Method 3
a beat frequency signal based on a signal which is delayed by the time delay module among the PIM signal and the reference signal
Data Source
AI summary
The present disclosure provides apparatuses or methods for detecting a PIM generation point, which can enhance the accuracy of the PIM generation point detection up to a level of 10 centimeters, and thus enable rapid replacement or maintenance of a disfunctional element causing the PIM by installing and controlling a time delay module in an output end of a reference signal (or, a PIM signal) for detection of the PIM generation point.