Improved Time-Reversal-Based Beamforming Using a Self-Biasing Switch

In this letter, a self-biasing switch is proposed to reduce the artifacts associated with time-reversal-based beamforming. This device consists of multiple diodes placed in series on a 50- Ω microstrip. At low incident voltages, this device behaves like a high-pass filter, rejecting low-power transients over a broad bandwidth. Once the activation voltage of these diodes is exceeded, the capacitive elements of this filter are shorted, allowing energy to pass with significantly less attenuation. By preferentially attenuating low-power transients, this device can suppress the temporal artifacts associated with the time reversal process. An experimental demonstration of this device is performed using a reverberant cavity as a passive delay line network. Measured outputs from this cavity are used as inputs to a simulated array of Vivaldi antennas to demonstrate the proposed improvement in beamforming.