Design and Validation of Measurement Procedures for Time-Varying Scatterers and Antennas

Abstract

There is an interest in establishing performance metrics for time-varying antennas. However, quantifying the realized performance of a time-varying antenna requires considerations not necessary in LTI measurements as many metrics and electromagnetic properties, often utilized in traditional LTI antenna measurements, are not applicable to a non-LTI antenna measurement. It is expected from earlier work that antennas loaded with time-varying components will radiate power at many frequencies other than the excitation frequency when excited by a pure-toned signal. Two conventionally used metrics to calibrate antenna performance are monostatic backscatter and effective aperture. Using only traditional measurement methodologies and definitions are not ideal as they are only concerned with a device's performance at the incident frequency. However, the existing quantities and their measurement methodology can be redefined to account for the time-varying antenna's non-LTI behavior. This work presents a methodology for performing cross-frequency backscatter and effective aperture measurements of an antenna loaded with a time-varying component. These techniques are demonstrated by measuring two switch-loaded bowtie antennas operating at four different switching frequencies. These techniques are also validated and supported by comparing the measurements to the simulation results provided by the electromagnetic solvers XFdtd and CM-MoM.