Implementation of Multi-Frequency Antenna with Broadband Designs for Wireless Applications

Abstract

Wireless systems have highly revolutionized and replaced the wired communication systems in consumer as well as industrial applications. Advanced multifunctional wireless devices have evolved which are capable of supporting multiple systems, services and standards in a single device. For example, smart phones provide a number of applications to the user simultaneously such as audio, video, data transfer, radio, TV, NFC feature and access to different networks such as Bluetooth, GPS, WiFi, WLAN and GSM. The usefulness of wireless device depends on the effectiveness of the antenna used for the transmission and reception of information over the wireless media, as it ensures coverage, capacity and quality to the system. The performance characteristics of any communication system for a particular application are profoundly influenced by the type of antenna used. Its design and placement in the communication system also affect the application of the system. Different forms of antennas are employed in different systems. Some systems require directional antennas for transmitting information in a particular direction such as radars, whereas in some other systems, the omnidirectional antennas are used to broadcast the information equally in all directions as in WLAN access points. In some systems antennas for point-to-point communication are required. Thus antennas play an important role in formulating the characteristics of any communication system. Next Generation wireless system devices needs high data rate for multimedia applications like VoIP, Video Conferencing, VBR (Variable Bit Rate) etc. These high data rate applications require large bandwidth. So the antenna used should have good characteristics over wide range of frequencies. Thus the antennas should be designed in such a manner that these are able to sustain multi-functionality feature and multibanding in homogeneous as well as heterogeneous bands with enhanced bandwidth at each band, in a single compact antenna system. Along with the multifunctional features, the wireless communication devices need to be compact and light weight such as mobiles and other handheld devices. Thus the antennas used in such devices should have low profile, light weight, cost effective, safe for human health, and able to transfer data at high data rate at different communication standards. In this thesis, methods to develop Microstrip Patch Antennas (MPAs) that exhibit multifrequency and wideband performance for different homogeneous and heterogeneous wireless applications like WLAN, UNII bands, WiMAX, LTE, aeronautical radionavigation and radiolocation standards are investigated. iv In this research work different techniques have been used to design various multifrequency antennas with a goal of getting perfectly matched antenna with appreciable value of return loss, wide impedance bandwidth, increased gain, and reasonable antenna size. First two antenna designs are presented to cover various homogeneous bands of WLAN standard. In the first design, the use of multiple rings in the main patch is dictated along with the formation of DGS (Defected Ground Structure) in the CPW ground plane to obtain multibanding at 2.4 GHz WLAN band, lower/ middle UNII bands at 5.2/ 5.3 GHz. The second design presents an innovative antenna design in which a UWB antenna is experimented with EBG filter structure implemented at the input side, that is, on the microstripline to create a stopband from 5.9 GHz to 11.3 GHz and enabling its use in homogeneous WLAN bands. The other two antenna designs are aimed at making multifrequency antennas for heterogeneous networks which are based on different topologies. The modification in the patch by means of slotting to form E-slot in the radiating patch and extending the Co-Planar waveguide (CPW) feed all around the patch is found effective in producing additional resonances beside the fundamental resonating frequency. The modifications in the patch cause the current distribution to change accordingly, generating multiband operation with wideband characteristics for heterogeneous networks. The design is able to cover several communication bands at LTE (3.4 to 3.6 GHz) and WiMAX (3.4– 3.694 GHz), aeronautical radionavigation radiolocation (2.7–2.9 GHz), radiolocation radionavigation (2.9–3.1 GHz), radiolocation earth exploration-satellite (active) mobile (3.1–3.3 GHz), radiolocation amateur mobile (3.3–3.41 GHz), mobile (3.41–3.6 GHz) standards. In the fourth design, rectangular rings along with parasitic strip and meandering are incorporated in a rectangular patch to obtain multiband operation for WLAN (2.4/5.2/5.8 GHz) and WiMAX (2.3/2.5/5.5 GHz) bands with enhanced impedance bandwidth in WLAN (from 2.26 GHz to 3.03 GHz) and WiMAX (from 4.48–6.85 GHz) bands. On the whole, the antenna designs presented in this thesis, display multiband and wideband behavior. The goal of achieving seamlessly matched antenna with considerable reflection coefficient, desired radiation patterns and increased peak gain is accomplished. The simulation results are obtained on CST MWS V.10 and V.14, and IE3D software to judge their performance. On attaining the desired results the antenna structures are fabricated using photolithographic and wet etching method and tested practically on Vector Network Analyzer (VNA) and Anechoic Chamber, available in Microwave and Antenna Laboratory of Thapar Institute of Engg. & Tech., which validates the simulated results of the designed antennas.