RF Signal Vector Spectral Measurement via Frequency Stitching
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Solution Overview
Problem
Conventional methods for vector spectral measurements of RF signals, such as Digital Oscilloscope and Wide-Bandwidth Spectrum Analyzer, are expensive and limited in amplitude resolution, especially when dealing with repetitive RF waveforms, and Narrow Bandwidth Spectrum Analyzers face bandwidth limitations and interference issues.
Innovation Solution
A method using a Narrow Bandwidth Spectrum Analyzer with a frequency stitching technique, employing marker signals for external triggering to capture and stitch multiple frequency segments, preserving phase continuity and reducing interference, allowing for vector spectral measurements of wide-bandwidth RF signals with repetitive waveforms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a Wide-Bandwidth Spectrum Analyzer (WBSA) is used to measure wide-bandwidth RF signals, then the bandwidth coverage is improved, but the device cost and complexity increase significantly
Solution Approach 1:
The patent divides the wide-bandwidth RF signal measurement into multiple narrow-bandwidth frequency segments. Each segment is measured sequentially by the NBSA, and then the segments are stitched together in the frequency domain to reconstruct the complete wide-bandwidth spectrum. This segmentation approach enables wide bandwidth measurement using a low-cost narrowband instrument.
Solution Approach 2:
The patent transitions from time-domain sequential measurement to frequency-domain composite measurement. By measuring multiple frequency segments at different center frequencies and stitching them in the frequency domain, the system achieves wide bandwidth coverage equivalent to expensive wideband analyzers.
2Productivity
If a Digital Oscilloscope (DO) is used for vector spectral measurements, then the measurement speed is improved, but the amplitude resolution and phase accuracy deteriorate
Solution Approach 1:
The patent replaces the digital oscilloscope's time-domain sampling approach with a spectrum analyzer's frequency-domain measurement approach. By using the NBSA's built-in FFT and frequency domain processing, the system achieves superior amplitude resolution and phase accuracy while maintaining efficient measurement of repetitive waveforms.
3Adaptability or versatility
If frequency segments are captured and stitched together, then the wide-bandwidth measurement capability is improved, but the phase continuity between segments may be lost
Solution Approach 1:
The patent uses external triggering as an intermediary reference signal to synchronize the capture of multiple frequency segments. The trigger signal, derived from the repetitive waveform itself, provides a common time reference that enables accurate phase alignment and stitching of segments in the frequency domain, preserving phase continuity across the wide bandwidth.
Data Source
AI summary
A method is provided for performing vector spectral measurements of a radio frequency (RF) signal having a repetitive waveform, using a receiver having a frequency span less than a total bandwidth of the RF signal. The method includes capturing multiple frequency segments of the RF signal corresponding to waveforms of the repetitive waveform synchronized to corresponding external triggering, each frequency segment having a corresponding segment bandwidth less than the total bandwidth of the RF signal; performing at least one instance of phase stitching and at least one instance of amplitude stitching between adjacent captured frequency segments; and using an Inverse Fast Fourier Transform (IFFT) to obtain a time-domain record of the repetitive waveform.