Bandwidth Enhancement of Rectangular Patch Antenna based on the Properties of Substrate

Microstrip antennas or patch antennas are popular for their attractive features such as low profile, low weight, low cost, ease of fabrication and integration with RF devices. Micro strip antennas have been found favorable because they are inexpensive to manufacture and compatible with monolithic microwave integrated circuit designs (MMIC). They are usually employed at UHF and higher frequencies because the size of the antenna is directly tied to the wavelength at the resonance frequency. A Microstrip or patch antenna is a narrowband, wide-beam antenna fabricated by etching the antenna element pattern in metal trace bonded to an insulating dielectric substrate with a continuous metal layer bonded to the opposite side of the substrate which forms a ground plane. The most commonly employed microstrip antenna is a rectangular patch. They usually consist of a rectangular metal patch on a dielectric coated ground plane. The strip and the ground plane are separated by a dielectric sheet referred to as the substrate. The radiating element and the feed lines are normally photo etched on the dielectric substrate. The rectangular patch antenna is approximately a one-half wavelength long section of rectangular microstrip transmission line. The major disadvantages of Microstrip antennas are lower gain and very narrow bandwidth. Microstrip patch antennas has some drawbacks of low efficiency, narrow bandwidth (3-6%) of the central frequency, its bandwidth is limited to a few percent which is not enough for most of the wireless communication systems nowadays. Millimeter wave technology being an emerging area is still much undeveloped. As micro strip antennas have found wide variety of application areas, a number of techniques are evolved to improve its limited bandwidth. A straight forward application to improve the bandwidth is increasing the thickness of substrate supporting the micro strip patch and to increase the inductance of the microstrip by cutting holes or slot in it. However limitation shall exist on the ability to effectively feed the patch on a thick substrate and the radiation efficiency can degrade with increasing substrate thickness. A substantial research needs to be done in this area as its applications are numerous. The input impedance‚ radiation patterns and S11 performance are used for the analysis of the different configurations. In the present endeavor a rectangular patch antenna is designed on thick substrate and also a slot is cut in the substrate of a designed patch antenna and the bandwidth variations are compared and simulation is done using MATLAB software.