Design of low observable antenna using active hybrid-element FSS structure for stealth applications

A novel EM (electromagnetic) design of low observable antenna using active hybrid-element frequency selective surface (FSS) as ground plane is presented in this paper for stealth applications. The EM characteristics of active hybrid-element FSS structure are reconfigured from reflecting mode to transmitting mode and vice versa by switching ON and OFF the PIN diode at 10 GHz. In ON state of diode (reflection mode), the FSS structure shows extremely less transmission (<−40 dB), which corroborates its suitability for ground plane of antenna. In OFF state of diode (transmission mode), it exhibits bandpass response over the frequency range 9.3-10.7 GHz corresponding to very less power loss (<−0.42 dB). Further, a low observable microstrip patch antenna (MPA) is designed using proposed FSS structure as ground plane and its EM characteristics are studied using commercial software package. In ON state of diode, the FSS-based MPA is observed to perform as typical MPA and its out-of-band radar cross section (RCS) also reduces as well. In OFF state of diode, FSS-based antenna does not radiate while passes EM signal impinging on its structure in result reduces significantly in-band RCS (up to 15.8 dBmm2) as compared to conventional MPA. Finally, a prototype active FSS-based antenna is fabricated and measured for proof-of-the concept.