Certain investigations on the development of planar antennas for unlicensed microwave wireless communications

Abstract

Radio frequency spectrum is the range of electromagnetic frequencies from approximately 30 KHz to 300 GHz that can be used for wireless communications. Unlicensed spectrum in this spectrum encourages the development of complementary, demand-enhancing services that raise the economic value of the licensed spectrum networks. The main challenge while operating in the unlicensed spectra is to overcome the high attenuation due to oxygen and water vapour. Due to this limitation, it is safe to use these frequencies for indoor applications. Hence, in order to extend it to outdoor applications and to increase the transmission radius, it is essential to design unique high-gain antennas that overcome the atmospheric attenuation. The design of Microstrip antennas is selected for its distinct advantages such as low profile planar configuration, low volume, low cost, light weight and almost maintenance free installation. This thesis focuses on the design of different types of patch antennas for wireless application. Other types of antennas like fractal and Vivaldi antennas are also presented. These antenna models are simpler in configuration, less complex in the design procedure and offers multiband operation. A 24 GHz Micro strip patch antenna for short range radar for vehicular communications is designed, developed and implemented. The availability of the 24-24.25 GHz license exempt band provides short range high speed communication possible with high throughput and high data rate. The real time measurements show a minimum return loss of -38.79dB for the fabricated antenna at 24 GHz band and provide a gain of 5.9dBi for an input newline