Gain Enhancement of Triangular Slot X-band Antenna Using Rhombic Loop Frequency Selective Surfaces

Abstract

The paper presents boresight gain enhancement of a microstrip fed X-band triangular slot antenna using rhombic loop (RL) based frequency selective surfaces (FSSs). Two single side printed orthogonal layers of arrays of dual rhombic loops (DRLs) kept in pairs are stacked together to form cascaded dual rhombic loop (CDRL) based reflective surface which exhibits wide stop bands within X-band but with reflection phase non-linearities. The non-linearities are suppressed when both layers are printed back to back (BTB) on both sides of same dielectric substrate while they are completely eliminated when both the layers are printed on same side of the dielectric substrate to form a merged dual rhombic loop (MDRL) based FSS. A triangular slot antenna operating at 8.2 GHz is designed and integrated with these FSSs for a purpose to investigate their impact on antenna performance. Through simulations, it is found that antenna when integrated with MDRL FSS demonstrates superior performance. Later, the slot antenna and MDRL FSS are developed and integrated to perform experiments. The integrated antenna exhibits an impedance bandwidth of 650 MHz and a maximum gain of 8.5 dB in antenna boresight including 4.5 dB enhancement due to frequency selective reflectors.