Comparative study of different techniques to design ultra wideband antenna in cognitive radio

Abstract

The Ultra Wide Band (UWB)radio technology has attracted much interest in academics, industrial and standardization activities. Transmission systems with instantaneous spectral occupancy of higher fractional bandwidth is characterized by UWB. The antenna is probably the most overlooked part of a RF (Radio Frequency) design. The range, performance, and legality of a RF link are critically dependent upon the antenna. The radio spectrum is the source that is needed to be utilized using cognitive radio (CR) system. Detecting primary users (PU) over the spectrum is one of the problems that we face in the cognitive radio system. Here the UHF (Ultra High Frequency) TV Band is specifically addressed which is a target band of IEEE802.22 standardization. The UHF TV band is 336MHz wider according to CCIR (Consultative Committee on International Radio) standards. One major challenge in designing a UWB antenna for UHF band is limiting the physical size of the antenna. The paper illustrates the successful design, implementation and testing of a UWB antenna for cognitive radios in the UHF TV Band. The antenna is simple, cheap and very compact and can be used in fixed transceivers. Different papers on various configurations of wideband antenna have been studied and the different antenna parameters have been verified. The microstrip antenna has advantages of being low profile, light in weight and cheap. In this paper we have designed and simulated a GPS micro strip antenna that perform wide band CP radiation. The proposed antenna consists of orbicular micro strip patch, a substrate of feeding network and a circular patch above and orbicular patch antenna fed by two coaxial wires that is considered as the base structure. The feeding network was designed and combined with the antenna. The proposed CP antenna can be designed by adjusting the dimensions of the inner and the outer radius of the orbicular patch to determine the operating frequency of the antenna. Then the parameters of the branch line directional coupler can be fine tuned to achieve the required frequency with good impedance matching.