Time-Modulated Transmissive Frequency-Selective Surfaces for Ultrawideband Doppler Spectral Manipulation

Abstract

The time-modulated frequency-selective surfaces (TM-FSSs) have emerged as an effective platform for Doppler radar spoofing via controlled spectral redistribution. However, most reported TM-FSS designs employ a continuous metallic ground plane, resulting in reflective-only operation and preventing transmission-based integration with radiating apertures. This constraint limits their applicability in systems requiring simultaneous communication and Doppler signature manipulation. In this work, a compact, low-profile transmissive TM-FSS is presented, enabling wideband time-modulated transmission while generating harmonic sidebands for Doppler spectral engineering. The proposed TM-FSS exhibits a wideband time-modulation response from 2.2 to 11.1 GHz, corresponding to a fractional bandwidth of 133.8% and covering the S-, C-, and X-bands. The periodic temporal modulation redistributes the incident signals into first-order harmonic components without displacing the fundamental transmitted spectral component. To experimentally verify the claimed transmissive operation under practical excitation, the TM-FSS is integrated with an X-band antenna array beneath the surface, serving solely to demonstrate uninterrupted in-band transmission through the time-modulated structure. Full-wave simulations, fabrication, and measurements confirm the wideband transmission performance and stable harmonic generation, establishing the proposed TM-FSS as a viable transmission-enabled platform for Doppler spectral manipulation. The proposed transmissive TM-FSS overcomes the inherent limitation of prior reflective-only TM-FSS designs by simultaneously supporting in-band antenna integration and Doppler spectral manipulation within a single compact platform. © 1963-2012 IEEE.