Passive Intermodulation Measurement Using Single Bandpass Filter
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Solution Overview
Problem
Existing PIM measurement apparatuses face challenges such as high costs and complexity due to the need for precise bandpass filters and complicated circuit configurations to accurately measure intermodulation distortion in transmission lines, leading to measurement errors and difficulties in determining the location of passive intermodulation sources.
Innovation Solution
A simplified apparatus and method that uses a first and second signal source, a combiner, a reference signal source, and a bandpass filter to measure and compute the location of a passive intermodulation source by passing distortion components through the bandpass filter, allowing for simultaneous measurement with a reference signal and reducing the need for expensive filters and complex circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two bandpass filters with sharp bandpass characteristics are used to pass (2F1−F2) component with enough attenuation of F1 and F2 components, then measurement precision is improved, but device cost and complexity increase
Solution Approach 1:
The patent extracts only the necessary filtering function to a single bandpass filter, removing the requirement for two complex filters. The single filter is configured to pass the (2F1−F2) component while attenuating F1 and F2 components, achieving the necessary measurement precision without the complexity of dual filter systems
Solution Approach 2:
The patent changes the operating parameters by using frequency modulation techniques and specific frequency relationships (2F1−F2) to enable measurement without requiring two identical bandpass filters. This parameter change allows a single filter to perform the necessary frequency selection and attenuation functions
2Measurement precision
If two bandpass filters with same frequency and phase characteristics are used, then measurement precision is improved, but device cost and manufacturing difficulty increase
Solution Approach 1:
The patent removes the requirement for manufacturing two identical bandpass filters with matching characteristics. By extracting the filtering function to a single filter, the manufacturing process is simplified while maintaining measurement precision through proper filter configuration and frequency modulation techniques
Solution Approach 2:
Instead of using two identical physical filters, the patent creates a virtual reference signal that copies the necessary frequency characteristics. This allows a single physical filter to be used in both measurement paths through frequency modulation, eliminating the need for costly matched filter pairs
3Reliability
If buffer circuits are added between signal source and frequency doubler, and between frequency source and frequency mixer, then reliability is improved by preventing signal reflection, but device complexity increases
Solution Approach 1:
The patent removes unnecessary buffer circuits from the signal path by redesigning the frequency multiplication and mixing stages. The frequency doubler and mixer are directly connected to the signal source and frequency source without intermediate buffers, maintaining reliability through proper impedance matching and isolation techniques built into the frequency conversion stages themselves
Solution Approach 2:
The frequency doubler and mixer circuits are designed to perform multiple functions including signal generation, frequency conversion, and impedance matching. This multi-functionality eliminates the need for separate buffer circuits while maintaining system reliability and preventing signal reflections
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
The solution enables accurate and cost-effective measurement of passive intermodulation sources in transmission lines, improving the precision and efficiency of determining their location without the need for expensive bandpass filters and complex circuit configurations.
Implementation Method 1
a bandpass filter configured to pass the distortion component of the signal returning from the PIM generation source to the test port
Implementation Method 2
a combiner configured to mix a first signal from the first signal source and a second signal from the second signal source
Implementation Method 3
a frequency mixer configured to mix the converted signal and the reference signal
Data Source
AI summary
A method and apparatus are described for generally passive intermodulation measurement to specify a location and strength of an intermodulation source of a passive component in a transmission line. Beneficially, the apparatus and method are comparatively simple and inexpensive.