| Electrically small antennas are a classic research topic for more than half a century, and recently they are becoming increasingly significant with tremendous development of personal communication system. Antenna engineers are faced with appealing design problems of the smallest possible antenna while accompanying satisfying radiation characteristics such as broad impedance bandwidth, high radiation efficiency, and good radiation patterns.;Design and analysis of planar electrically small antennas are pursed in this research work using electromagnetic simulations and measurements. The efforts are dedicated to improving radiation performances of planar printed antennas. An ultra slow-wave right-handed transmission line is invented based on quasi-lumped LC circuit elements to miniaturize a printed planar quarter-wave monopole. Design considerations are addressed including un-balanced antenna systems, radiation of backside ground plane, dielectric loading, bow-tie shape optimization and folding of radiation arms, which outline optimization techniques associated with radiation performances. A new model of N-folded printed dipoles in vertically folded configuration is proposed which shows that the impedance bandwidth can be improved by N times and the radiation resistance by N2 timesin comparison with the non-folded dipole at self-resonances. |
