Modeling and analysis of smart material inspired ultra wideband reconfigurable antenna for cognitive radio applications

Abstract

The Cognitive Radio is an emerging technology in wireless access, to significantly improve the utilization of radio spectrum by allowing access opportunistically. The goal of Cognitive Radio is to develop a system that can interact with its radio environment to adapt, discover, and exploit unused frequencies. Cognitive Radio is utilized to make use of unused or unlicensed channels. If a spectrum hole is discovered through this process, the channel is subsequently utilized for other wireless communication applications. newlineThis continuous (or discontinuous) sensing process on a large bandwidth imposes different constraints on the radio-frequency front-ends of the secondary user. More precisely, these requirements constrain strict issues on antenna design, low noise amplification, frequency synthesizers providing a carrier frequency from tens of megahertz to about 10GHz, mixing spurs, and spectrum sensing. Software-defined Cognitive Radio equipment requires broadband and adjustable antennas, multiband amplifiers, RF filters, broadband direct-conversion mixers, baseband filters, and ADCs and DACs. These RF components are expected to work across a wide frequency range. newlineIn Cognitive Radio (CR) applications, reconfigurable antennas are used to change fundamental features and efficiently employ available bandwidth, whereas MIMO antenna system-based reconfigurable antennas are to be used to meet the high data rate requirements for future wireless terminals. In general, Spectrum sensing is usually done using UWB antennas, while communication is done with frequency reconfigurable narrow band (NB) antennas. In Cognitive Radio applications the main purpose of employing the reconfigurable antennas is to reduce the cost and space for fast tuning. But all these reconfigurable mechanisms make the printed antennas bulky and complex, which nullify all the advantages of planar antennas. Even these reconfigurable mechanisms are very difficult to implement in practice. newline