Broadband time-domain measurement system applied to the characterization of cross-modulation in nonlinear microwave devices

This paper presents a calibrated 4 channel broadband time-domain measurement system for the characterization of nonlinear microwave devices. The hardware architecture of the proposed measurement system is described with particular emphasis on the samplers and intermediate frequency (IF) circuit configuration. The sampling heads are working at a high strobe signal repetition frequency that can be tuned between 357 MHz and 536 MHz. 40 GHz RF frequency bandwidth is achieved. The calibration procedure of this system is also described. This instrument is then used for cross-modulation characterization of a 15W GaN HEMT CREE power amplifier at S Band. Cross-modulation measurements between a double side band amplitude modulation and a single tone signal at a 60 MHz offset frequency are performed to illustrate the capabilities of the proposed system. Time-domain waveforms are measured and variations of amplitude and phase modulation indices versus input power are recorded.