A Reconfigurable Microstrip Patch Antenna for Various Wireless and Cognitive Radio Applications

Abstract

Cognitive radio is an apparent technology for coherent use of the radio spectrum where, the spectrum can be used by the unlicensed users without interference with the licensed users. Reconfigurable antennas provide a potential solution to solve the antenna problems related to the cognitive radio system using the ability to switch frequency, radiation patterns and polarization. In this paper a reconfigurable microstrip patch antenna for possible applications in cognitive radio systems is presented. This work provides a methodology to design reconfigurable antennas with PIN diode switch. The reconfigurability is achieved in the frequency ranges from 4.3 GHz to 8.3 GHz respectively. To switch between the frequencies in the cognitive radio, the frequency reconfigurability is done. The PIN diode switch is used to change the dimensions of the patch and to make the antenna to resonate at various frequencies. The proposed antenna is simulated using Ansoft HFSS software. The results show with only two switches 9 different transmitting frequencies are available which are useful to implement cognitive radio applications. Keywords: Cognitive radio, Ansoft HFSS, PIN diode, Reconfigurable antenna, microstrip patch antenna, reflection coefficient. I. INTRODUCTIONThe main goal of cognitive radio system is to determine the spectrum holes using an ultra wide band sensing antenna and to transmit using a narrow band frequency reconfigurable antenna in the identified free channels [4], [8], [9]. The main feature of cognitive radio is to sense the communication environment to maximize the quality of service for the secondary users and to minimize the interference with the primary users. Reconfigurable antennas can be achieved by many techniques that alter the electromagnetic fields with respect to antennas aperture by redistributing the currents by electrical, optical, and mechanical means. Reconfigurable antennas are needed to cover different wireless services over a wide frequency range. So in order to be able to transmit at any frequency a frequency reconfigurable antenna is required for a cognitive radio system. By altering the frequency of operation a cognitive radio is able to communicate efficiently across channel. To meet this requirement a rectangular patch antenna can be used. It has light weight, planar structure, low cost and ease of design. Hence it is more useful as a communicating antenna. Reconfigurability can be achieved by using different types of switches like FET, PIN-Diode and varactor diode, among them PINDiode is being mostly used due to its high switching speed [2], [5]- [7]. A rotatable reconfigurable antenna design has been proposed in [1]. Two different triangular shaped patches that are separated by 8mm are used. Two different positions are identified by which each of triangular shaped patches can be fed one at a time. To go from one position to the other the assembly of two patches has to be rotated by 180 degrees. The antenna can be tuned between 5.3 -9.15 GHz in one position and 3.4 -4.85 GHz ...