Investigation of active microstrip antennas and improved performance techniques

The microstrip antenna (MSA) is one of the most widely used microwaveantennas possessing several advantages. However, it presents a low impedancebandwidth, low gain, and tolerance problems. Probably the most direct way ofimproving the impedance bandwidth of a microstrip antenna is to attach a separatelossless matching network. The aim of the this study is to develop a new wide bandmatching systems for improving the electrical characteristics such as, low efficiency,low antenna gain and narrow band. In the research stage of this thesis, differentmicrostrip antenna geometries, matching networks and theoretical models foranalysis and design of microstrip antennas were investigated. Three different types ofthe matching circuits which are realized as the negative capacitance, the negativeinductance and the Pi-matching circuit with RC mutator, have been proposed. Theimpedance bandwidth and the return loss level were improved by using the proposednew compensation networks. The theoretical solutions of the developed matchingnetworks by using the active circuit components were investigated and themathematical models were developed. A parametric study of the components in theactive compensation networks on both radiation and input characteristics of themicrostrip antennas were carried out. The performance parameters of the designedmicrostrip antennas with and without compensation networks and classicaltechniques have been compared. The matched antenna prototypes for some of theconfigurations have been fabricated and tested in order to verify the simulated andthe theoretical results. Within the tolerances, the agreement with the results has beensatisfactory.