Investigation and design of a very compact circularly polarized microstrip antenna for use on microsatellites.

摘要

Microsatellites are becoming increasingly viable as a platform for research and communication. Their small size and weight demand innovative and compact electrical and antenna systems There has been significant research into the miniaturization of microstrip patch antennas. The main techniques for miniaturization include the incorporation of various shorting or loading schemes, including the very popular quarter-wave patch arrangement, and the use of high dielectric constant materials. The quarter-wave concept was extended by proposing the idea of folding both the patch and the ground plane into layers to create a folded shorted patch (S-P) further reducing the antenna element size. This thesis presents the investigation and design of a circularly polarized folded S-P antenna using multilayer printed circuit board (PCB) technology for use in microsatellite communication.;This thesis describes the theoretical, simulation, and experimental based investigation of the performance of a folded S-P structure. Transmission line models for a linearly polarized antenna element were developed and extended for use with dielectric substrate materials. Using the theoretical models as a starting point, simulations were carried out on various single element configurations to qualitatively understand their effects on antenna performance. These configurations included probe, aperture, and capacitive plate terminated probe feed systems, different dielectric materials, and the usage of electrical vias to form electrical walls. Findings of the single element investigation were then applied in the design and optimization of a four-element antenna array where the elements and their corresponding feed signals were sequentially rotated and phased to generate circular polarization.;Both a linearly polarized single element prototype and a four-element circularly polarized prototype were fabricated. The four-element array prototype was designed to work at 400MHz. It had a length, width, and height of 150mm x 150mm x 40mm which is equivalent to 0.2lambdao x 0.2lambda o x 0.053lambdao. Experimental performance of the prototypes in terms of the return loss (S11) and radiation patterns was measured and analyzed. The results supported the simulation findings. The measured impedance bandwidth for the array prototype was greater than 20MHz and the simulation predicted a boresight realized gain of 2.3dBic. The results and subsequent analysis show that implementation of a circularly polarized folded S-P antenna using multilayer PCB techniques has good potential for CP antenna systems on microsatellites where size is critical.;Keywords: Antenna, design, compact, circular polarization, folded, microsatellite.