Development of a circular complementary split ring resonator microstrip antenna for high altitude platform station

Abstract

In this thesis, the influences of Circular Complementary Split Ring Resonators (CCSRR) and air gap within the circular microstrip patch antenna structure are investigated for the use of Malaysia’s future High Altitude Platform Station(HAPS) wireless communication. The proposed antenna is designed to operate from 5.850 GHz to 7.075 GHz spectrum band using microwave laminate RT/D 5880 (εr = 2.2 and thickness of 1.82 mm). The antenna structure was organized into three separate layers consisting of circular copper sheet as the ground plane (layer number one), an undersized main radiator, where the electromagnetic signal and energy gathered and stored, focuses and passes through (layer number two) to resonate its above layer and the etched slotted split ring resonators on the dielectric laminate (layer number three) supported by low dielectric foams (εr = 1.2). All layers are separated by an air gap, simulated and optimized using the Computer Simulation Technology Suite (CST), Microwave Studio software. The distance of air gap, the positioning of coaxial feed together with a small circular copper patch, the number and the width of the split ring resonators corresponding to each individual circular patch are varied and analyzed as the key player studies. The results of the return losses, VSWR, realized gain and farfield characteristics either in 2D, 3D or polar plot views obtained are compared and analyzed. Measurement of the fabricated antenna showed deep line return loss below -10 dB beginning at 5.75 GHz to 7.25 GHz as compared to simulations which were 5.0 GHz to 7.5 GHz (VSWR 2:1). Overall, the antenna, once compared between its simulations and fabricated managed to produce a stable 5 dBi gain and directivity along the targeted spectrum band. The results show that inclusion of split ring resonators have enhanced and improved the antenna fundamental performance and in terms of sustaining the targeted bandwidth. The CCSRR structure also managed to produce real part of permittivity and permeability readings into negative values through a two port numerical simulation, part of a metamaterial simulation experiment, that is to investigate Double Negative (DNG) characteristics. DNG characteristics helps to improve surface current flow raised the gain and beam phase within the frequency spectrum (the more negative the values of ε and become, a slight increase to the gain can be observed). CST MW powerful transient solver was able to simulate the antenna integration with a miniaturized plane the stratospheric M55. Deploying two antenna units on the M55 aircraft wings (separated at 23 meter apart, the total wingspan = 37.46 meter) have created an array formation and further increased the signal gain. The antenna produced maximum E-plane and H-plane co and cross polarization difference in the magnitude of 3.5 dB and E-plane half power beam width (HPBW) of 200.