Switchable Feed Network using Microstrip/Negative-Refractive-Index Coupled-Line Coupler

This paper presents a single-feed switchable feed network that combines four ports of the microstrip patch antennas using the two microstrip/negative-refractive-index (MS/NRI) coupled line coupler. When a two-way quarter wavelength transmission lines, which are terminated by an antenna and each resonant frequency of the antennas is very closely located, it acts as an ideal single-pole double-throw (SPDT) switch. The MS/NRI coupled line coupler was used to achieve tight backward-wave coupling (- 3 dB) and port isolation. For verification purposes, a two by two microstrip patch array antenna for wideband code division multiple access (WCDMA) frequency bands (1.92 GHz - 2.17 GHz) was built and tested.