SIMULTANEOUS TRANSMIT AND RECEIVE ANTENNA FOR AESA RADAR

Abstract

To optimize available bandwidth, it is desired that the transmission and reception to be carried out simultaneously and at same spot frequency. Such type of simultaneous two-way communication is known as Simultaneous Transmit and Receive (STAR) or in-band full duplex communications. STAR systems are known to have high speeds and theoretically require almost half bandwidth for its operations as compared to its half-duplex counterparts. This thesis explores the feasibility of utilizing the emerging STAR technology in military applications such as Radars. Such systems when implemented will not only have high speeds two-way communication, require low bandwidth but also be able to fulfill various tactical operational requirements like ensuring electronic warfare as well as surveillance of the sector simultaneously. The thesis presents a STAR antenna system operating at 3.5 GHz (S-band) having high gain, high isolation and low cross polarization suitable for radar applications. The designed dual polarized antenna is a planar patch antenna, and is differentially excited with a pair of wideband planar baluns. This differential feeding scheme not only reduces the self-interference but also helps in improving the isolation between the differential ports. Defected ground structures below the patch are used for enhancement of antenna bandwidth. The measured |S11| ≤ - 10 dB bandwidth is 228 MHz (3.34 GHz to 5.62 GHz), isolation is better than 59 dB while realized gain is 10.1 dBi at TX port while it is 9.34 dBi at the RX port. The total efficiency is better than 80 % for both the ports.