Simulation and experiments on back-fed coplanar patch antennas

A new coplanar patch antenna (CPA) with back-feeding structure has been introduced. The simulation and experiment for the proposed antennas have been done at X-band. The measured results clearly demonstrate that the back-fed CPA has a similar behavior to the CPA with a surface feeding structure: it operates as a patch antenna rather than a loop slot antenna. The back-fed antenna has a reasonably good antenna gain (∼7 dBi at 10 GHz) and impedance bandwidth (∼4 % at X-band). Furthermore, a back-fed CPA with simple straight cutting slots on both ground conductors parallel to the feed line and the coplanar patch was introduced to improve antenna performance which may be degraded by some undesired modes introduced by the back feeding structure. The experimental results clearly showed that the slots can dramatically reduce or suppress some of the undesired exciting modes while keeping almost the same antenna gain but better return loss, front-to-back ratio and cross polarization at both E-plane and H-plane.