Simulation and experiments on back-fed coplanar patch antennas

In this paper, 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 demonstrated that the back-fed CPA has a similar behaviors as 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 reasonable good antenna gain (∼7dBi at 10GHz) 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 keep almost the same antenna gain but better return loss, front-to-back ratio and cross polarization at both E-pIane and H-plane.