Design and Analysis of Compact Antenna for Ultra Wideband and Super Wideband Applications

Abstract

At the initial stage of electronic communication, the connectivity between the users was provided through wired media. With advancement in technology the wired media was replaced by wireless medium. To provide connectivity through wireless medium the antenna is an integral part of the communication system. The wireless system provided the users unlimited connectivity even to the interior remote places. newlineThere after the number of applications associated with the wireless media communication compounded the system day by day. To handle this high data traffic the only solution is to have wide band communication system design. The antennas are also required to be developed to support this wideband wireless communication system. newlineThis thesis aims at design and analysis of planar microstrip antennas operating over a very wide band with appreciably less surface area. The designing not only limited to achieve a wider bandwidth but also to achieve appreciable gain in the entire operational band along with other electrical time domain parameters such as impulse response. To begin with the research, different techniques and methods used for designing antennas were extensively studied. newlineThe first antenna design demonstrates the use of fractal geometry to achieve the ultra wideband operability. In this study a hexagonal shaped radiator excited with a coplanar waveguide feed was proposed operating in the millimeter spectrum having an operational bandwidth of 13 GHz (22.7 GHz-35.7 GHz). newlineIn the second step the requirement of providing stop bands at the frequencies used by other applications (WLAN and Wi-MAX) co existing with commercial UWB spectrum (3.1 GHz-10.6 GHz) was taken care of. For this purpose, a study on different band stop filter designs were taken up. newlineOnce the design methods for radiator having UWB operability and the band stop filter were confirmed through simulating different designs on Ansys HFSS 14.0 plat form, these techniques were merged to design the UWB antennas with band notch characteristics. There are three different designs demonstrated in this thesis. newlineThe first proposed UWB antenna has a circular radiating patch. The quarter wave transformer matching technique was employed in feed design to support wideband operation. The antenna has an impedance bandwidth of 11.2 GHz (2.6 GHz - 13.8 GHz). A band notch was created in the WLAN band (5.15 GHz - 5.85 GHz) using rectangular CSRR structures. newlineIn the second UWB antenna design a modified octahedron shaped radiator with a microstrip feed was proposed. A pair of parasitic loading planes was placed beside the feed line to achieve wideband operability. The proposed antenna has an impedance bandwidth of 17.1 GHz (2.4 GHz 19.5 GHz). Here rectangular split ring resonators (RSRRs) with different dimensions were used to achieve the band notch at Wi-MAX (3.3 GHz 3.7 GHz) and WLAN (5.15 GHz 5.85 GHz) bands. newlineIn the third UWB antenna design a tree shaped radiator with CPW feed was proposed. The wideband operability was achieved by modifying both the top and bottom ground planes. The proposed antenna has an impedance bandwidth of 17.3 GHz (2.2 GHz-19.5 GHz). Here the band notch at Wi-MAX band was achieved by using a Spiral shaped Defected Microstrip Structure (SDMS) and for WLAN band rectangular split ring resonator (RSRR) was used. newlineIn the following step efforts were focused on extending the operational impedance bandwidth further keeping the other electrical characteristics intact. In this process a circular patch SWB antenna was proposed. The radiator was fed through a feed line which was designed through quarter wave transformer matching technique. This proposed design has an impedance bandwidth of 26 GHz (2.4 GHz 28.4 GHz). newline newlineAt the final step of the designing efforts were made to take the UWB and Narrow band technology on a single platform. In this regard a frequency reconfigurable antenna was proposed with operability either in the UWB spectrum (3.1 GHz 10.6 GHz) or WLAN spectrum (5.15 GHz 5.85 GHz). The switching between the modes was done by changing the biasing conditions of a P-I-N diode used as a switch. During reverse bias condition of the P-I-N diodes the circular patch radiates providing the UWB operation and during the forward bias condition the RSRRs were connected to provide the WLAN band operability. newlineThe performance and characteristics of all these designs were analyzed both in time domain and frequency domain on HFSS platform. The optimum parameters of the designs were taken by parametric characterization. The proposed UWB antennas with band notched characteristics were fabricated and the electrical performance parameters were measured. The simulation and measured results are in good agreement making the designs suitable candidate for different UWB applications. newline