A Compact, Low-Profile Shorted TM1/2,0 Mode Planar Copolarized Microstrip Antenna for Full-Duplex Systems

In this letter, a single-layer compact copolarized shorted TM1/2,0 mode microstrip patch antenna is presented for in-band full-duplex application. Two shorted TM(1/2,0 )mode patch antennas, used for transmission and reception purposes, make the structure compact. The widehand behavior of the patch antenna is obtained by fusing the two resonances, one because of the shorted TM1/2,0 mode radiating patch and the other because of the lambda/4 line resonator. To enhance the isolation between the transmitter and receiver antenna, a novel defected ground structure is used. Slots are introduced into the ground plane to create a weak field region for the basic antenna element. The other antenna element (receiver) is located in the weak field region to enhance isolation. Further enhancement in isolation is achieved by introducing a T-shaped metallic strip into the slots. The structure is proposed with the credits of compactness, enhanced bandwidth, colinear polarization, very less fabrication complexity, low profile, and high isolation. The proposed structure is fabricated and measured. The structure experimentally exhibits a bandwidth ( <= -10 dB) of 2.42-2.52 GHz with the isolation of 25 dB, peak isolation of 36 dB, and an average realized gain of 4 dBi in the entire band.