abstract This paper presents empirical results of a novel planar microstrip array antenna based on a simplified composite right/left-handed transmission line (SCRLH-TL) for application in circularly polarized synthetic aperture radar (CP-SAR) systems operated in UHF, L, S, and C-Bands. The array antenna consists of 6 × 6 matrix of spiral-shaped radiating elements that are excited through proximity-coupled, single feed-line. Pattern synthesis technique is used to determine the excitation coefficients (amplitude and phase) to apply to the individual array elements to achieve the required pattern shape. The array antenna has dimensions of 111.5 × 96.06 mm2. The measured impedance bandwidth of the antenna is 3.85 GHz for S11 < ¿10 dB from 300 MHz to 4.15 GHz, corresponding to a fractional bandwidth of 173%. Maximum gain and radiation efficiency measured are 4.8 dBi and 79.5%, respectively, at 2.40 GHz. The antenna has a 3-dB axial-ratio bandwidth of 3.94 GHz from 144 MHz to 4.66 GHz. The antenna¿s beamwidth in azimuth and elevation planes vary between 60° and 120° across its operational frequency range from 300 MHz to 4.15 GHz. The antenna design fulfills the challenging electrical and physical specifications required for CP-SAR employed onboard unmanned aerial vehicle (UAV). © 2018 Informa UK Limited, trading as Taylor & Francis Group.
keywords metamaterials planar array antenna simplified composite right/left-handed transmission line synthetic aperture radar antenna arrays antenna feeders bandwidth directional patterns (antenna) electric impedance electric lines metamaterials microstrip antennas radar antennas spiral antennas synthetic aperture radar unmanned aerial vehicles (uav) airborne synthetic aperture radars axial ratio bandwidth composite right/left-handed transmission lines excitation coefficients fractional bandwidths operational frequency range physical specifications planar-array antennas microwave antennas