Exploitation of the electromagnetic band gap (EBG) in 3-dB multi-layer branch-line coupler

Abstract

An advanced shift that driven with high carrier frequencies, wide bandwidths, device densities, unique numbers, universal high-rate coverage and a seamless user experience present future 5G air interface and spectrum together with LTE is currently experiencing an explosive growth in the communication world. This letter presents performance improvement of multi-layer slot coupled 3 dB Branch-Line Coupler (BLC) with the integration of electromagnetic band gap into the design. The proposed BLC is simulated on a Rogers RT/duroid 5880 with permittivity of 3.38 and designed to operate at 7 GHz. A configuration of uniplanar compact electromagnetic band-gap (UC-EBG) structures is exploited to serve as a slot coupled ground to reduce mutual coupling between the radiating elements and to achieve a higher operating resonance frequency. The periodic structure of electromagnetic band gap (EBG) is considered in RF-microwave industry due to their extraordinary surface wave suppression property. The proposed BLC delivered simulated coupling and transmission values of 3.12 and 4.04 dB, respectively. The impedance bandwidths (BW) of the BLC significantly increase to 120% when integrated with an EBG slot coupled ground plane. The proposed BLC design was accomplished in multilayer microstrip-slot technology by employing coupling technique. Ultimately, these applications produce wide operational bandwidth in which the BLC will serves as an essential key beam forming network element for future 5G wireless communications.