Bandwidth Enhancement Technique in Microstrip Antenna for Wireless Applications

Abstract

Low proflle, light weight, easily mounted and broad bandwidth are the key charac- teristics for antennae designed for wireless applications. The microstrip antenna (MSA) suits the features mentioned except for its narrow bandwidth. The bandwidth of the microstrip antenna usually ranges from less than 1% to several percent. This paper experimentally investigates an alternative approach in enhancing the bandwidth of the microstrip antenna for the Wireless Lo- cal Area Network (WLAN) application operating at a frequency of 2.45GHz. The bandwidth enhancement technique which is studied is the Identical Dual Patch Microstrip Antenna with Air-Gap (IDMA). A bandwidth enhancement of more than 11% was achieved. Wireless applications have undergone rapid development in recent years. One particular wireless application that has experienced this trend is the Wireless Local Area Network (WLAN). The wireless application that is selected to be studied is the 2.4GHz to 2.5GHz frequency band which is based on the 802.11b WLAN standard. This frequency band is very popular due to its low cost. WLAN antenna requires being low proflle, light weight and broad bandwidth. The microstrip antenna suits the features very well except for its narrow bandwidth. The WLAN antenna should have a minimum bandwidth of 100MHz to fully utilize the WLAN band based on the 802.11b standard. The conventional microstrip antenna could not fulflll this requirement as its bandwidth usually ranges from less than 1% to several percent (1). Although the required operating frequency range is from 2.4GHz to 2.5GHz, at least double the bandwidth is required to avoid expensive tuning operations and to cause uncritical manufacturing. Therefore, there is a need to enhance the bandwidth of the microstrip antenna for WLAN applications. This paper investigates a technique which can enhance the bandwidth of the microstrip antenna without increasing the lateral size and the complexity of the microstrip antenna too much. The Identical Dual Patch Microstrip Antenna with Air-Gap (IDMA) bandwidth enhancement technique takes the advantage of using the air gap to lower the efiective permittivity and increase the total thickness of the microstrip antenna which is essential for bandwidth enhancement. This bandwidth enhanced microstrip antenna can be deployed for the WLAN application operating at a frequency of 2.45GHz. 2. SIMULATED AND MEASURED RESULTS OF THE SINGLE-LAYER MICROSTRIP ANTENNA