Investigating Time-Varying Signal Propagation at Sub-THz Frequencies Using a VNA

Vector network analyzers (VNAs) are traditionally designed to measure time-invariant networks, where each frequency point is measured individually over a specified interval, influenced by factors such as the intermediate frequency bandwidth (IFBW), dwell time, and the total number of points. This approach creates challenges for time-varying signals, as waveform changes must be captured throughout the sweep. This study explores methods to adapt VNA signal acquisition for time-varying transmissions, evaluating the feasibility and limitations of such measurements. We analyze sweep duration, test segmented waveforms, and conduct experimental verification to establish a measurement scenario. This setup enhances our understanding of time-varying measurements and to apply it to other dynamic channel-sounding systems, enabling estimation of measurement uncertainties of time-varying environment. We present the measurement setup, mathematical analysis of the scenario, and time intervals for each segment at varying velocities, considering optimized reflector positions for each frequency step.