Temporally Controlled Switchable Microwave Rasorbers

Frequency-selective absorbers (FSRs) with tunable transmission windows have recently garnered significant attention due to their high stealth performance. However, such an architecture remains susceptible to high-power electromagnetic (EM) wave illumination with broad or variable frequencies. To address this issue, we propose a temporal modulation-based smart FSR with the transmission window being either spectrally tunable or completely blocked, depending on practical needs. We demonstrated the switch between a typical FSR and a broadband absorber on a microsecond time scale using our alternative current (ac) bias network. Experimentally, a compact C-band reconfigurable FSR with wideband low reflection (< −10 dB) in 4 GHz to 8 GHz and a highly movable transmission window across the entire band was achieved. By applying a small ac bias voltage, we showed that the transmission can be significantly suppressed with good numerical and experimental agreement. We also discussed the influences of biasing voltage and wave incident conditions. This work reveals the potential of temporal modulation in constructing compact metamaterial FSRs for comprehensive wave manipulation and device applications.