A 20-Element Cavity-Backed Slot Electronically Steerable Parasitic Array Radiator (ESPAR) With 2-D Beamsteering and Minimized Beam Squint

A 20-element cavity-backed slot antenna array is presented herein based on an electronically steerable parasitic array radiator (ESPAR) cross subarray. This ESPAR array is able to steer the main beam within +/- 45 degrees in the E-plane and +/- 40 degrees in the H-plane without grating lobes. Inside each subarray, the beamsteering is realized by tuning the reactance of the loads at the four parasitic elements. Therefore, only four phase shifters are needed for this 20-element array to achieve 2-D beamsteering, corresponding to an 80% reduction on the number of phase shifters compared to a classic phased array. The measured impedance matching is maintained below -10 dB from 6.0 to 6.4 GHz (6.4% fractional bandwidth) at all scan angles. The radiation patterns are measured at five different scan angles in E- and H-planes. At each scan angle, the measured radiation patterns at five frequencies across the impedance-matching bandwidth exhibit very small beam squint. The measured peak gain is found to be 14.0 dBi at the boresight direction.