A Multiband Frequency Reconfigurable and Bifunctional Metasurface

ABSTRACT A multiband, frequency reconfigurable, and bifunctional metasurface for simultaneous full-space control of Electromagnetic (EM) waves is proposed for wearable applications. The unit-cell structure contains concentric rectangular rings and empty substrate-integrated waveguides (SIWs) for miniaturisation. The miniaturised dimension of the Polydimethylsiloxane (PDMS) substrate is 18 × 18 × 1 mm3. Two varactor diodes are integrated for frequency switching operations by configuring the structure using bias voltage (forward/reverse) through the ground via the proposed surface resonates at 3.5,5.8,7.6 (On),8.1 (Off) GHz frequencies, which provide simultaneous bi-functionalities: artificial Magnetic Conductor (AMC) reflector/absorber in reflection and transmission space of operations, respectively. In reflection space, it acts as an AMC reflector by providing in-phase reflection with a radiation efficiency of >84% and unidirectional E-field patterns. However, the magnitude of absorbance is more than 96% in transmission, thereby simultaneously controlling full-space EM wave in normal incidence. The obtained simultaneous metasurface functionalities are investigated for different oblique angles of the transverse electric (TE) and transverse magnetic (TM) incident wave. The proposed surface is fabricated and experimentally validated. The features of the designed bifunctional metasurface provide a strategic platform for potential multifunctional wearable devices.