Study of Different Bandwidth Enhancement Techniques for Microstrip Patch Antennas

Abstract

Microstrip Antenna (MSA) is a simple antenna with a dielectric substrate, a ground plane on the bottom and a patch on the top. It is planar, low profile, simple, less expensive to manufacture. Having so many advantages, the major disadvantages of a MSA are low gain and narrow bandwidth (BW). Conventional MSA offers a narrow BW of around 1%, which is very less for many practical applications. Thus, MSA are often not preferred for the applications where wide bandwidth is the foremost requirement. Hence, researchers are very much interested in finding the new techniques to increase the impedance bandwidth of a MSA. It can be done by applying many novel techniques, like loading a patch with a slot, making a ground plane open, increasing the height of a substrate, reducing the dielectric constant of a substrate, folding patch, etc. In this thesis, the brief introduction of microstrip antenna, the detailed literature survey on several techniques applied to increase the bandwidth is discussed. Conventional technique to enhance the BW of MSA is by increasing the thickness of a substrate and by decreasing the dielectric constant of a substrate. BW also depends on the feeding technique. This is proved in this thesis by suitable examples. The wide bandwidth of 153.88% and 158.26% is obtained by rotating a patch with having L-Shaped slot in the ground and by loading two opposite triangular slots in an open ground antenna having U-Slot in the ground, respectively. Antenna based on the use of multilayer substrate concept is proposed which achieved a BW of 20% covering a Wi-Fi band from 4.4-5.3 GHz. Another wide band antenna which is designed by using fractal and fed by coplanar waveguide and having an UWB application for a band of 3.7-11.7 GHz is proposed and the results are discussed.