A device that radiates transverse magnetic Bessel beams in the radiative near field is reported. The cone angle of the emitted radiation remains constant over a wide frequency range (18-30 GHz), allowing highly localized pulses (X Waves) to be generated under a broadband excitation. The design process, based on ray optics, is discussed. Both frequency and time domain experimental results from a prototype are presented. The measured fields show close agreement with simulation results and demonstrate the radiator's ability to emit X Waves within its nondiffracting range.
We consider nonlinear electromagnetic time reversal (TR) applied to a semireverberant complex enclosure containing a discrete passive nonlinear circuit. Unlike closed reverberant systems used for the previous demonstrations of nonlinear electromagnetic TR, the experimental system used here better represents realistic environments that are often far more lossy. Moreover, we demonstrate the use of pulse inversion to extract nonlinear responses for electromagnetic time reversal, which could help overcome potential practical-implementation issues. Concentrating on the application of this technique as an efficient power-delivery method, we evaluate the peak power enhancement resulting from TR focusing at the location of the nonlinear circuit.PHYSICAL REVIEW APPLIED 2, 044013 (2014) 2331-7019=14=2(4)=044013 (8) 044013-1
Abstract-In this paper, we demonstrate a device that is capable of generating an ultrashort (sub-nanosecond) high power microwave pulse by means of passive pulse compression in a compact reverberant cavity. The long duration input pulse into the cavity is created using time-reversal techniques, which allows the waveform to contain the inverse profile of the cavity phase distortion. When fed back into the cavity, the wave focusing at the output port results in a compressed ultrashort pulse with enhanced peak amplitude. We experimentally demonstrate a pulse compressor consisting of a 0.0074 m 3 cavity capable of generating a 130 picosecond pulse from an input waveform of 300 nanosecond duration with the peak gain of up to 19 dB.
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