Bandwidth Enhancement of Microstrip Antenna for Wireless Local Area Network Applications

These days, there is a very large demand for wireless applications. Antennas which are used in these applications should be low profile, light weight, low volume and broad bandwidth. The microstrip antenna suits the features mentioned except for its narrow bandwidth, typically ranges from less than one percent to several percent of relative bandwidth. By reducing that limitation, the advantages using microstrip antenna can further outweigh its disadvantages. In this research, an alternative bandwidth enhancement technique is studied and then proposed in order to broaden the bandwidth of the microstrip antenna. The wireless application that is selected to be studied is the Wireless Local Area Network (WLAN) based on the IEEE 802.11b standard. In Malaysia, this WLAN band spans from 2.4GHz to 2.5GHz. Initially, the characteristic of a microstrip transmission line is analyzed. This is done to determine the cause for microstrip antenna in having narrow bandwidth. Then, a basic single-layer microstrip antenna without bandwidth enhancement technique is designed. A substrate with low permittivity namely RT/Duroid 5880 is used as the dielectric for the radiating patch. The feeding method used is the coaxial probe. Parameters such as the operating frequency, input impedance and the bandwidth are observed. This design will serve as a benchmark for the design of the microstrip antenna with bandwidth enhancement technique. The bandwidth enhancement technique which is selected is the Identical Dual-Patch Microstrip Antenna with Air-Gap (IDMA). This technique makes use of the air gap for bandwidth enhancement of the microstrip antenna. By using this technique, a bandwidth enhancement of about 11% has been achieved. This bandwidth very well covers the required WLAN band with an operating frequency of 2.45GHz.

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