Design and Experimental Demonstration of Time-Modulated FSS in Broad Frequency Range for Radar Countermeasure

Abstract

In this letter, the time modulation utilizing switchable frequency selective surfaces (FSS) for a broad range of frequencies has been designed and experimentally demonstrated. The unit cell of the FSS comprises three layers, with the middle layer exhibiting switchable behavior with the help of the p-i-n diode. The incident electromagnetic (EM) wave undergoes time modulation through the use of a time-varying reflection coefficient. This is achieved by periodically altering the reflection state of the switchable FSS structure. The time-modulated complex-valued reflection coefficient can effectively produce the harmonics with reduced power of incident frequency component and enhance side-band harmonics. The thickness of the proposed prototype is 0.1 $\lambda _{L}$ with a periodicity of 0.13 $\lambda _{L}$ where $\lambda _{L}$ corresponds to the lowest frequency. The measured spectrum of reflected EM wave constituent at f $_{in}$ achieved ranges between −5 dB and −18 dB in the broad frequency range from 4.6 GHz to 7.8 GHz. This is the first experimental demonstration in C band. The proposed prototype have lower periodicity with wide fractional bandwidth and polarization insensitivity structure. With Doppler like frequency shift in reflected wave, the structure can effectively disrupt the Doppler radar's ability to detect and track targets.