Novel Broadband Patch Antennas With Reduced Radar Cross Section

This research focuses on the configuration of novel broadband monopole patch antennas with reduced Radar Cross-Section(RCS). The dissertation is composed of two parts. The first part gives a research background, literature review and the theoretical analysis as to get idea about the basic formulas of the RCS hence to comprehend the significance of the RCS. The second part of the dissertation comprises the experimental work, designing of suitable antennas and their outcomes. Besides this, it demonstrates many techniques for the RCS reduction of antennas so as to overcome the issue as discussed.Radar cross-section(RCS) is a measure of how detectable an object is with radar, a bigger RCS indicates that a target is more easily detectable and vice versa. The RCS contributes for the most part in two advancements, one is the detection technology and other is the stealth technology. For the recognition innovation the RCS ought to be bigger as to make objects observable. But for the stealth technology RCS must be reduced thus to make an object invisible or low observable, in this manner it is additionally called low observable(LO) technology. Antenna is one of the key components of the radar system. In military and defense applications the antenna RCS is an important subject in detecting and tracking aircrafts, ships and missiles and additionally developing counter intelligence, such as, RCS reduction and stealth design. The radar stealth performance of military systems and platforms acts as a vital measure of their survivability in hostilities. Thus, the antennas with reduced RCS have a significant role in low observable platforms.In the literature many techniques for RCS reduction of antennas has been found. The Frequency Selective Surfaces(FSS) and Radar Absorbing Materials(RAM) are the most common and practiced solutions used for reducing the RCS. But, in ultra wide band operation, the radar absorbing material coating methods do not produce an intended effect by virtue of its narrow operation-band. Moreover, these RAM coating techniques changes over the electromagnetic energy into heat energy, thus severely reduces the antenna performance. For the vast majority of the techniques, when they improve the RCS, then they severely degrade the antenna gain or scattering performance. Therefore no single method is suitable for the RCS reduction, especially in ultra wideband frequency limits at the premises of balancing the impedance matching and radiation performance of antenna. Henceforth, despite this the RCS reduction is a serious issue and is the focal center to be solved in this subject.In this dissertation, the antennas are designed based on multi techniques like size miniaturization technique, subtraction of less effective area, ground blended and slot etching techniques on the ground and patch, subsequently to explain the issue as talked about. These techniques are based on the surface current distributions. In this research, after examining the surface current distributions of referenced and the modified antennas in working conditions, the region of minimum current amplitude is reduced in area either by notching aperture of different geometrical shapes or by etching slots on it. Therefore, the RCS will be reduced, while the performance of the proposed designs will be maintained the same. The ground plane is blended at the opposite edges as to stop the gradual changes of radiating beam and hence to maximize the power transfer from the antenna or minimize signal reflection from the load. Moreover, slots are notched on the ground which serves as impedance matching circuit hence to balance the radiation performance of the designed antennas. In order to achieve a research goal, the antenna models are simulated by using Computer Simulation Technology(CST) microwave studio then the designs are fabricated and functionalized.In this research study triangular, octagonal and H-shaped broadband monopole patch antennas are aimed and investigated for C-band, X-band, and UWB applications. The intention of antenna designs is to realize RCS reduction and to show the effect of some physical parameters on the performance of antenna. The return loss curves of designed antennas shows the well matching of signals with feed port. Moreover, a return loss less than-10 dB of the new antennas is achieved in the entire frequency range to cover C-band, X- band and UWB applications. The parametric investigations of models give a clever thought that the RCS has been reduced to the required worth.In this dissertation five antenna models are designed and their simulated and measured results are matched with each other and the referenced designs as well. The printed octagonal-shaped antenna with octagon aperture has better results compared to the other designs. The outcomes demonstrate that the designed antennas have an improved RCS in all the working frequencies; which is achieved because of the relatively small geometrical size of the proposed antennas. Therefore, the proposed designs provide the possibility of future success and hence can be advantageously utilized as UWB antennas where the low RCS property is required.