A Low-Cost Suspended Patch Antenna for WLAN Access Points and Point-to-Point Links

In this letter, a very low-cost antenna is presented for 802.11-b (2.4-2.484 GHz) wireless local area network (WLAN) applications. This antenna can be used in two different configurations. In a stand-alone configuration the antenna has a 12-dBi gain and a 40° half power beamwidth (HPBW) in both E and H planes, thus matching typical requirements for WLAN base stations or access points for indoor WLAN. Furthermore, the same antenna can be used as feeder for a standard TVSAT offset parabolic reflector, thus obtaining a high-gain antenna system configuration (Gain = 23 dBi, HPBW = 12° with a 80 cm reflector) useful for point-to-point connections. The latter configuration provides a very low-cost antenna system useful for Internet service provider to cover the "last mile" toward the customer via a wireless link. A FR4 epoxy-glass substrate is employed providing a solution that is cheap both in material and manufacturing costs. A "suspended" structure allows to synthesize an effective material with low dielectric constant and losses, suitable for antennas application, despite the use of FR4; indeed an 86% loss efficiency is obtained. Some prototypes was realized and measured; their input impedance and gain was found in satisfactory agreement with the numerical predictions provided by the design tools.