Active Transmission/Absorption Frequency Selective Surface With Dynamical Modulation of Amplitude

A novel active frequency selective surface (AFSS) is proposed in this communication which not only can achieve electromagnetic (EM) switching between the transmission and absorption modes but also has the capability of dynamically modulating the amplitudes for the above two modes. The designed AFSS consists of a periodic metallic structure layer and a graphene capacitor layer. The periodic metallic structure plays the role of the EM switching for the mode selection of transmission/absorption by regulating the bias states of the loaded p-i-n diodes, while the corresponding amplitudes of the transmission/absorption can be further tuned by changing the effective sheet resistance of graphene through an electrostatic field bias. An equivalent circuit model is introduced to explain the EM switching and amplitude tuning behaviors of transmission/absorption. In addition, the designed AFSS is also demonstrated to perform well under circumstances of oblique incidence and different polarizations. The AFSS prototype is fabricated and measured. In the transmission mode, the transmission loss can be tuned from -4.8 to -1.1 dB at the band of 6-7 GHz, while in the absorption mode, the average value of absorptivity can be controlled between 0.65 and 0.95 at the band of 5-8.4 GHz. The measurement results agree well with the simulation ones, which demonstrate the great performance of our AFSS.