Focusing an arbitrary RF pulse at a distance using time-reversal techniques

In this paper, we demonstrate the use of a time reversal (TR) technique to effectively focus an arbitrary RF pulse at a remote location from a single-feed aperture for directed energy applications. The TR focusing is achieved by backing the aperture with a reverberating cavity, whose multipath environment enables the reconstruction of the aperture field distribution needed for directing the energy to the target location. Here, we use the impulse response between the target location and the time-reversal mirror (TRM) located inside the cavity to enable the effective transmission of arbitrary RF pulses, which are convolved with the time-reversed impulse response before transmission. The demonstration is carried out both numerically and experimentally for various RF pulses. The results show good temporal and spatial focusing at the target location. This approach could be an efficient selective “beamforming” method for directed energy, where it only requires a single feed and the impulse response between the TRM and target location or direction to effectively deliver an RF pulse of choice within an ultra-wide bandwidth of the impulse response.