SHORT-PULSE PROPAGATION IN A HOLLOW WAVE-GUIDE - ANALYSIS, OPTOELECTRONIC MEASUREMENT, AND SIGNAL-PROCESSING

An asymptotic analysis is performed for short-pulse propagation in a h ollow waveguide. It is demonstrated that each time-domain mode support ed by the guide is characterized by a time-dependent frequency which, as time proceeds, approaches the modal cutoff frequency, This phenomen on is demonstrated experimentally by performing short-pulse optoelectr onic measurements for the case of rectangular waveguide, In these meas urements a short-pulse laser is used to switch planar antennas photoco nductively, generating freely propagating waveforms with instantaneous bandwidth from 15-75 GHz. Time-frequency signal processing is perform ed on the measured data, the results of which are in close agreement w ith the predictions of the asymptotic analysis.