Synthesis of an Ultra-Wideband Pulse by a Log-Periodic Antenna with Continuous Excitation by Harmonic Oscillations

We propose a method for synthesizing ultra-wideband pulses using a vector network analyzer and a wideband transceiving log-periodic antenna. The transfer characteristic of the antenna-feeder transmission line of the system is described by the model of a two-port network whose S-matrix elements are calibrated for at least two heights of the antenna above the reflecting surface (metal plate). The proposed method of calibrating the transfer characteristic of a log-periodic antenna allows one to minimize the amplitude- and phase-frequency distortions, which are introduced to the sensing pulse by the antenna. Employing the developed method, we experimentally demonstrate a possibility of synthesizing an ultra-wideband pulse with a duration of 0.46 ns at the level of half amplitude of the envelope (when the pulse contains several field oscillations) using a log-periodic antenna with a passband of 1.36 to 4.88 GHz (at the level −10 dB). This method is specially developed for creating miniature radar systems using portable vector network analyzers and log-periodic antennas for applications to remote sensing of an underlying surface by ultra-wideband pulses from small-size unmanned aerial vehicles.