A Study Of Multiband Printed Anteimas And Array Pattern Synthesis

Due to the development of modern radar, electronic warfare and wirelesscommunication and the upgrading of electronic equipments, modern antennas andantenna arrays are facing more challenges, which require antennas with multiband anddemand antenna arrays to be scannable in a wide frequency band with lower sidelobelevel. As a main part of a research project, this dissertation is mainly concerned with thedesign of multiband printed antennas and the optimization of antenna arrays based onthe DE algorithms. The major contributions of this dissertation are outlined as follows:1. Two types of multiband printed antennas are designed. According to therequirements of WLAN or WiMAX systems, a compact monopole antenna withS-shaped and C-shaped meander strips and a microstrip-line-fed solt antenna with twopairs of band-notched strips are studied. The surface current distributions and parametereffects are analyzed to investigate the radiation principles. The prototypes of theproposed antennas are also fabricated. The measured results show that these twoantennas have good multiband characteristics.2. Low sidelobe concentric ring antenna arrays are designed. Patterns of concentricring array with sidelobe suppression under first null beamwidth (FNBW), aperturedimension and efficiency constraints are synthesized. The simulation results of severalexamples are described. The relation between aperture effieciency and PSLLperformance is investigated. The results also demonstrate the stability and reliability ofthe DE algorithm.3. A wideband scannable aperiodic linear array is designed. With given aperturedimension, bandwidth, and maximum scan angle, the peak side lobelevel of a linearscannable array is minimized by using the DE algorithm to find the optimalinter-element spacings. Simulation results show that the aperiodic placement techniqueis a very effective approach to suppress grating lobes of a linear scannable array inwideband. The simulation of the optimized array is carried out by Ansoft HFSSsoftware, the results of which show good agreements with that of the optimization.