A 3-D Wideband and High-Selectivity Amplifying Frequency-Selective Surface Based on Slot Line and Microstrip Line

In this work, a wideband and high-selectivity amplifying frequency-selective surface (AFSS) has been proposed. To achieve a wideband FSS, meta vias that are employed to couple energy between a microstrip line and slot lines have been created. A transmission zero has been introduced at high frequency by short-circuiting microstrip lines in parallel, which improves the selectivity of FSS and decreases the out-of-band level. To achieve the passband amplification, the amplifier is integrated into the microstrip line. Compared to the other FSS available, AFSS can increase the amplitude of electromagnetic waves. This makes AFSS potentially helpful in future communication systems, such as improving signal-to-noise ratio, antenna gain, signal detection, and signal isolation. To better understand the working mechanism of the AFSS, its equivalent circuit has been proposed. The amplifying passband of the AFSS ranges from 2.79 to 3.8 GHz. The relative amplification bandwidth of the AFSS is 30%. A maximum gain of 9.6 dB at 3.5 GHz has been obtained by the experimental type. A transmission zero at 4.2 GHz has been introduced. The experimental results corroborate the simulation results.