| Modern antennas with multiband, wideband and miniature characteristics have been drawn more and more attention due to the development of modern radar, electronic warfare and wireless communication and the upgrading of electronic equipments. As two kinds of antennas with good performance, planar printed antennas and tapered slot antennas (TSAs) become important research topics in antenna area. As a main part of a research project, this dissertation is mainly concerned with the design of printed antennas and TSA arrays. The multiband printed antennas, the band-notched ultra-wideband printed antennas, as well as the tapered slot antennas and arrays have been investigated systematically. The author’s major contributions are as follows:1. Four multiband printed antennas are studied. According to the requirements of WLAN or WiMAX, a broadband coplanar waveguide-fed (CPW-fed) printed monopole antenna with fractal slots covering2.4/5GHz WLAN and3.5GHz WiMAX bands, a G-shaped printed monopole antenna with good omni-directional radiation patterns at the higher bands, a compact printed monopole antenna using a metal via and parasitic patch and a compact coplanar strip-fed (CPS-fed) printed slot antenna are designed. The prototypes of the proposed antennas are also fabricated. The measured results show that these four antennas have good multiband characteristics.2. Four ultra-wideband (UWB) printed antennas with band-notched characteristics are studied. In order to restrain the potential interference on UWB system from the others, such as WLAN or WiMAX, a rectangle monopole antenna with a L-shaped slot and a meandered strip, a slot antenna with a Sierpinski-shaped slot, a printed monopole antenna with two or three metal strip are proposed, respectively. At the same time, the equivalent models for each antenna are also introduced. The prototypes of these band-notched UWB antennas are also fabricated. The measured results show that these antennas have good band-notched UWB characteristics.3. Three ultra-wideband baluns are proposed and studied. Firstly, a low-loss microstrip-to-parallel strip balun is presented, which is used for the antipodal Vivaldi antenna. Secondly, the modified wideband microstrip-to-slotline balun is introduced, in which a microstrip open stub, composed of a quarter circular patch, a quarter ellipse patch and a polygon strip, is used to improve the impedance matching at the lower operating band. Based on the design of microstrip-to-slotline balun, a straight strip is also employed to obtain the desired band-notched characteristic. The proposed baluns are fabricated. The measured results indicated that these baluns have good ultra-wideband or band-notched characteristics.4. Several ultra-wideband TSAs are investigated. Firstly, an antipodal Vivaldi antenna is introduced covering1-12.5GHz frequency band. By analyzing the relationship between radiation areas and impedance matching of the TSA, a novel radiation flare curve is then proposed for improving the impedance matching in the lower band. A compact Vivaldi antenna with aperiodic corrugated edges is also introduced. Finally, a method for improving TSA’s radiation patterns at the higher band is investigated. Additionally, the prototypes of the proposed TSAs are fabricated and measured.5. The ultra-wideband tapered slot arrays are studied. Based on the design methods of tapered slot array and the analysis of element coupling in an infinite tapered slot array, a microstrip-fed TSA element is designed. After analyzing the coupling of TSA elements in a finite array, a method for reducing the truncation effects is proposed. Combining with the low-loss ultra-wideband feed networks, the1×8-and8×8-element tapered slot arrays are designed and fabricated. The measured results show that both tapered slot arrays have good ultra-wideband characteristics. |
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