An Approach for Characterizing the Frequency Response of Sampling-Oscilloscopes Using a Large-Signal Network Analyzer

We propose an approach for characterizing the complex frequency response of sampling oscilloscopes using a calibrated large-signal network analyzer (LSNA) and a broadband pulse source. First, we perform a full wave-parameter calibration of the LSNA using its internal continuous wave (CW) sources. Then, we replace the internal CW sources with an external broadband pulse source and measure it with the calibrated LSNA and oscilloscope connected to the LSNA test port. The complex frequency response of the oscilloscope's sampler is derived in the frequency domain as the ratio of the oscilloscope signal spectrum to the calibrated LSNA signal spectrum. We achieve less than 0.7 dB amplitude and 5 degrees phase difference up to 45 GHz between the proposed LSNA calibration and previous NIST electro-optic sampling (EOS) characterization of the same sampler.