Wideband high-gain multi-layer patch antenna-coupler with metamaterial superstrate for X-band applications

A wide bandwidth, high-gain and high directivity multi-layer patch antenna integrated with coupler and covered with metamaterial superstrate is proposed for frequency range of 10.8 to 12 GHz. The novel high level of integration of three different functions in one configuration is done in a straightforward design. It consists of a 50 ohm microstrip line coupled directly to the non-radiating edge of a patch antenna. This structure is covered by two layers of near zero refractive index metamaterial. The prototype of this configuration shows a flat coupling factor of 25 dB and a high isolation factor of 33 dB. The two layers of metamaterial superstrate enhanced the performance of the patch antenna-coupler. At the center frequency of 11.4 GHz, the gain of the patch antenna-coupler with metamaterial superstrate is improved by 8 dB to 13.4 dB and the return loss bandwidth is improved to more than 10%. Furthermore, the 3-dB beamwidth of the antenna is reduced by more than 70° to 30°.