Analysis And Design Of Planar Printed Antennas

In the21st century, electronic and wireless communication technologies have developedrapidly. As an important part of the modern wireless communication system, antennas arealways required to be miniature, multiband, wideband and etc.. Today, planar printed antennasbased on the advanced PCB technology have drawn more and more attention due to theirintrinsic merits such as simplicity in design, light weight, low profile, and ease to beintegrated with active components or microwave circuits. The microstrip patch antennas notonly have good directional radiation patterns, but also are agile for dual polarization orcircular polarization and suitable to be arrayed for high gain. Printed monopole antennas andslot antennas have good omnidirectional patterns, which can be developed for multiband orwideband operations. Thus, these kinds of planar antennas are researched and usedextensively in many modern applications such as radar, satellite communications, and mobilecommunications systems. Therefore, investigations on the planar printed antennas are of greattheoretical significance and practical value. With the consideration of associated researchprojects and some urgent requirements of antennas in wireless communications systems, thisdissertation is mainly concerned with the design of PCB based planar printed antennas,including dual-polarized microstrip array antenna, printed multiband antennas, and widebandantennas. The author’s major innovative contributions are as follows:1. Miniature multi-layer microstrip array antenna is investigated, and a noveldual-polarized monopulse microstrip array antenna is designed. Operating at Ku band, theproposed antenna comprises288dual-polarized microstrip antenna elements. There aremainly several characteristics for the antenna as follows:(1) By using8-layer PCB technology,the proposed antenna has achieved miniature and low profile characteristics, with a totalthickness of just1.6mm;(2) By adopting a high-isolated dual-polarized antenna as the arrayelement, the proposed array is proved to have a isolation better than-36dB;(3) Dualpolarization operation can make the antenna receive more spatial information, which willresult in a more accurate position. This design fills the blank of dual-polarized monopulseantenna;(4) With integrated feeding network, the antenna elements are arranged in the formof concentric rings, which not only make full use the space of the carrier, but also make thelayout more compact;(5) By using the180°out-of-phase feeding method, the array issymmetrical to the quadrant axis lines, which make it sufficient to design only one quarter of the feeding network. This action reduces the workload and improves the designing efficiency.2. The microstrip monopulse comparators are researched, and a novel configurationcharacterized by local circumrotatory symmetry is presented. This comparator, which has across shape, is composed of four3dB hybrid couplers and several delay lines. Different fromthe configurations reported in the references, the delay lines in the proposed comparator arecreatively shifted to the outside of the3dB hybrid couplers, which reduces the number of thedelay lines and hence improves the symmetry of the comparator, simplifies the designingprocess and reduces the designing difficulty.3. The multiband printed antennas are studied. By adding straight and meandered stripinside the rectangular ring, two tri-band monopole antennas are designed, which can be usedfor WLAN/WiMAX2.5/3.5/5.5GHz wireless communication systems; Similarly, branches areadded to U-shaped ring antenna to achieve2.5/5.5GHz dualband operation. Another dualbandmonopole antenna based on U-shaped configuration is designed to cover2.5/7.5GHz bandsby using trimming approach, which is a good candidate for WLAN or UWB communicationssystems; By etching∩-shaped slots on the ground, two printed slot antennas withrhombus-shaped slots are presented, which are suitable for WLAN/WiMAX3.5/5.5GHzapplications; By utilizing multi-branch method, a tri-band printed monopole antenna isdeveloped for WLAN/WiMAX2.5/3.5/5.8GHz. Prototypes of the aforementioned printedantennas are fabricated and measured, and good multiband characteristics are obtained.4. The wideband printed antennas are presented. In order to realize the wideband circularpolarization performance, an arrow-shaped branch is added on the traditional PIFA antenna,which results in a wideband circularly polarized PIFA antenna. The measured impedancebandwidth is39.8%(Return Loss>10dB), axial ratio bandwidth is41.7%(AR<2dB), whichprove the proposed antenna has a bandwidth wider than traditional circularly-polarizedmicrostrip antenna；By using a three-point-star strip, the bandwidth of traditional rectangularring monopole antenna can be broadened from31.2%to94.5%, and thus a wideband printedantenna for WLAN/WiMAX2.5/3.5/5.5GHz bands applications is designed; An miniatureprinted ultra-wideband antenna with an L-shaped slot and an inverted-F-shaped feedingbranch is presented, which can cover UWB3.1GHz to10.6GHz band, with a compact size ofonly23.7mm×23.7mm×0.8mm.