High-Speed RF Testing With Parasitic Suppression
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Solution Overview
Problem
Conventional testing systems for RF and microwave UUTs face challenges in achieving high-speed testing due to long settling times of YIG oscillators, while faster-settling sources like DDSs introduce parasitic effects that degrade spectral purity.
Innovation Solution
The technique involves obtaining multiple DFTs with different configurations to suppress invalid content by generating a corrected DFT with minimum magnitude values for corresponding frequencies, allowing the use of fast-settling local oscillators without compromising test quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a YIG oscillator is used as a local oscillator, then spectral purity is improved, but settling time increases
Solution Approach 1:
A digital signal processor acts as an intermediary to capture and process the test signal during the YIG oscillator's settling period. The DSP records multiple samples and performs digital signal processing to extract valid frequency components while filtering out parasitic effects, thereby decoupling the measurement process from the oscillator's settling time constraint
Solution Approach 2:
The system changes the parameter of sampling rate dynamically. By sampling at a rate higher than the minimum required by the Nyquist theorem, the system captures sufficient signal information during the settling period, enabling accurate spectral analysis even when the oscillator has not fully settled
2Loss of time
If a DDS is used as a local oscillator, then settling time is reduced, but spectral purity deteriorates due to parasitic effects
Solution Approach 1:
The digital signal processor extracts only the valid frequency components from the captured signal by analyzing spectral peaks and isolating them from parasitic effects. This extraction process separates the desired test signal characteristics from the unwanted DDS-generated artifacts, restoring measurement accuracy
Solution Approach 2:
The system converts the harmful parasitic effects into a beneficial diagnostic tool by analyzing their presence and characteristics. The parasitic signals serve as fingerprints that identify DDS usage, and their systematic analysis allows the test system to compensate for their effects and maintain measurement validity
3Measurement precision
If multiple DFTs are obtained with different configurations to suppress invalid content, then spectral purity is improved, but testing speed decreases
Solution Approach 1:
The system performs periodic sampling at multiple rates (e.g., 1 GS/s, 2 GS/s, 4 GS/s) and uses the periodic nature of spectral components to identify and eliminate invalid content. By analyzing results from multiple periodic sampling cycles, the system distinguishes between genuine signal features and parasitic artifacts introduced by the test apparatus
Data Source
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AI summary
A technique for testing an electronic UUT by a test apparatus includes obtaining multiple DFTs of a test signal received from the UUT with the test apparatus configured differently for obtaining each DFT. The resulting DFTs include both valid content representing the test signal and invalid content introduced by the test apparatus. The improved technique suppresses the invalid content by generating a corrected DFT, which provides minimum magnitude values for corresponding frequencies relative to the test signal across the multiple DFTs.