Design and Analysis of Frequency Reconfigurable Micro strip Antennas

Abstract

The goal of this thesis is to design and analyse the frequency reconfigurable microstrip patch antenna which are mainly the combination of filters and antennas called filtering antennas (filtennas). The increasing demand for high data rate and new wireless communication has led to the development of multifunctional devices including antennas and radio frequency (RF) front ends. The novel solution is to design antennas which has multiband, multimode, low profile, low cost and easy to integrate with portable devices. In this thesis three different frequency reconfigurable microstrip patch antenna has been proposed for cognitive radio system. The design and simulation of the proposed antennas are d one in CST (computer simulation technology) microwave simulation software. The first design is single port frequency agile antenna for overlay cognitive radio. When all the PIN diodes are in ON state, it is UWB and used to sense the entire spectrum and by selectively changing the PIN diode states five different reconfigurable cases occurs which is used for communication. Thereflection coefficient curve of UWB antenna shows bandwidth from 3.1 GHz to 9.8 GHz and reconfigurable antenna resonate at 6.7 GHz, 5.33 Hz, 5.73 GHz, 7.04 GHz, 6.33 GHz and 9.45 GHz. The second antenna proposed is dual port microstrip patch for cognitive radio system. This design is used for overlay cognitive radio in which one antenna is for sensing and other for communication. Sensing and communication can be done simultaneously and tuning in reconfigurable antenna can be done continuously. UWB antenna bandwidth is from 3.4 GHz to 13.2 GHz and the reconfigurable antenna is dual and triple band resonating frequency according to the biasing of varactor. The radiation pattern obtained in both cases are almost omnidirectional which is good for mobile application and sensing antenna. The third design is proposed for underlay cognitive radio system in which UWB antenna is used which radiate at very low power. The UWB antenna resonates from 2.8 GHz to 13.4 GHz. The filter is then added to this antenna as notch reconfigurable and this can be used to communicate over long distance without interference with primary used. The notches depends on states of PIN diodes, the frequency which are rejected are 5 GHz, 5.7 GHz, 6.45 GHz, 7.5 GHz, 9 GHz. The fourth proposed design is planar inverted F antenna (PIFA) for mobile devices. Currently cellular phones are using more than one services, so many antennas are needed. In the proposed design two varactor diodes has been used for tuning of operating frequency so that one antenna can replace many antennas for different wireless services like WIFI, WIMAX, GPS,WLAN , WiBro etc. .The simulated refection coefficient of this antenna shows dual band and triple band from 2 GHz to 5.5 GHz at different varactor diode biasing states.