A Double Rhombus Antenna Fed by 180 $^{\circ}$ Phase Shifter for Ultrawideband Phased Array Applications

A double rhombus antenna fed through a microstrip 180deg phase shifter is presented. The 180deg phase shifter is a novel design of microstrip-to-coplanar waveguide (CPW)-to-microstrip transition. The proposed phase shifter is obtained without changing the layer of the second microstrip line for an easy embedding into the feedline. Via holes are used to transfer the current from the top to the bottom substrate layer and vice versa. The antenna with the phase shifter is operating in a wide bandwidth from 5.7 and 18.6 GHz (106%), and provides stable endfire radiation patterns. This design is tested in a modified two-element array configuration and proved to have a wide usable bandwidth.