Passive Intermodulation Origin Detection Using Phase Delay
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Solution Overview
Problem
Existing methods fail to accurately determine the origin of passive intermodulation products in devices under test, leading to undesired interference in high-frequency transmission systems due to non-linear transmission characteristics, which complicates payload data decoding.
Innovation Solution
A method involving the use of two sinusoidal excitation signals with a specific frequency spacing to generate and measure passive intermodulation products, allowing for the determination of the phase and delay time of these products, thereby inferring the origin within the device under test.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If one of the two excitation signals is swept (as in the known measuring method), then the measurement process is simplified, but the method has not proved successful in practice and cannot accurately determine the place of origin
Solution Approach 1:
The patent applies periodic action by using two continuous wave (CW) excitation signals with fixed frequencies instead of sweeping one signal. The signals are applied periodically to the device under test, allowing for stable measurement conditions while maintaining measurement accuracy through phase comparison of the resulting intermodulation products.
Solution Approach 2:
The patent changes the measurement parameters by utilizing phase information of the intermodulation products at different frequencies. Instead of sweeping frequency, the method varies the frequency spacing between the two CW signals and measures the phase difference of the generated intermodulation products, which provides accurate location information through time delay calculation.
2Reliability
If passive intermodulation products occur in the frequency range of the transmission system, then interference occurs that complicates payload data decoding, but removing or avoiding these products requires identifying and correcting non-linearities in the device
Solution Approach 1:
The patent replaces physical inspection and correction methods with an electromagnetic field-based measurement system. By using phase measurement of intermodulation products generated through electromagnetic excitation, the system can remotely identify the location of non-linearities without physical disassembly or complex manual inspection, thereby reducing device complexity while improving reliability.
Solution Approach 2:
The patent introduces an intermediary measurement system that uses phase-coherent signal sources and vector network analyzers to indirectly detect the location of non-linearities. Instead of directly examining the device, the system measures the phase characteristics of intermodulation products, which serve as intermediaries carrying information about the location and nature of the non-linearities.
Data Source
AI summary
A method for determining the place of origin of a passive intermodulation product excites a distributed device under test with two first excitation signals (x1(t), x2(t), each with a single spectral line, of which the frequencies (f1, f2) provide a frequency spacing relative to one another. Following this, the phase (φIM3Meas) of a first passive intermodulation product generated at the place of origin in the distributed device under test from the first excitation signals ((x1(t), x2(t)) by nonlinear distortion is measured, and the delay time of the first passive intermodulation product from the place of origin to the measuring device is calculated from the measured phase (x1(t), x2(t)) and the frequency (2·f1−f2) of the first passive intermodulation product. Finally, the place of origin of the passive intermodulation product is determined from the delay time and the topology of the distributed device under test.