Adaptive Filter Bank for Pulsed RF Signal Characterization
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Solution Overview
Problem
Vector network analyzers face challenges in measuring pulsed RF signals with low duty cycles due to energy loss from adaptive filter nulling and gating, which reduces the system's dynamic range, making measurements unusable in certain applications.
Innovation Solution
A measurement system utilizing a filter bank to select and process multiple spectral components of pulsed RF signals, including a signal source, filter bank, accumulator, and analyzer, which combines and analyzes these components to determine device characteristics, thereby maintaining dynamic range independent of duty cycle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If adaptive filter nulling and gating are used to isolate the primary spectral component, then spectral isolation is improved, but processed signal energy is reduced
Solution Approach 1:
The measurement signal is divided into multiple spectral components using a filter bank, where each filter captures a specific spectral component. This segmentation allows the system to process multiple components simultaneously rather than isolating a single component, thereby maintaining total signal energy while achieving spectral separation.
Solution Approach 2:
Multiple spectral components captured by individual filters are combined through coherent integration in the accumulator. By merging the energy from multiple spectral components (including the primary component and sidebands), the system recovers the total signal energy that would otherwise be lost when using single-component filtering alone.
2Adaptability or versatility
If the duty cycle is decreased to enable isothermal measurements, then measurement applicability is improved, but system dynamic range is reduced
Solution Approach 1:
The sideband spectral components, which represent energy lost from the primary component when duty cycle decreases, are converted from harmful (signal energy loss) to beneficial (additional measurable signal). The filter bank captures these sidebands and the accumulator coherently integrates them with the primary component, transforming the duty-cycle-induced energy redistribution into a measurement advantage.
Solution Approach 2:
The system changes the processing approach by moving from single-frequency narrowband detection to multi-frequency spectral component detection. By adjusting the filter bank to capture multiple spectral components and using coherent integration, the system adapts its processing parameters to maintain dynamic range across varying duty cycles.
3Device complexity
If a single spectral component is measured using narrowband detection, then measurement simplicity is maintained, but signal energy capture is reduced
Solution Approach 1:
The signal spectrum is segmented into multiple discrete components using a filter bank, with each filter capturing a specific spectral component. This segmentation enables the system to process multiple frequency components separately while maintaining the simplicity of narrowband detection techniques for each individual component.
Solution Approach 2:
The measurement system is enhanced to perform multiple functions: it can detect the primary spectral component and simultaneously capture sideband components. The filter bank structure allows the same basic detection architecture to be applied across multiple frequency components, making the system multi-functional while retaining the simplicity of the original narrowband approach.
Data Source
AI summary
A test system and method which employs a filter bank to select different spectral components of a pulsed measurement signal. The filter bank utilizes filter nulls to suppress non-selected spectral components. After filtering the selected spectral components, the spectral components are combined to provide for a measurement signal which is analyzed to determine characteristics of a device being tested. The characteristics of the filters can be adjusted in response to a change in the characteristics of a pulsed signal applied to the device under test, so that the selected spectral components will correspond to desired spectral components generated by the pulsed signal applied to the device under test.