Vertically Multilayer-Stacked Yagi Antenna With Single and Dual Polarizations.

There are many applications such as local positioning systems (LPS) and wireless sensor networks that require high-directivity and compact-size or small footprint antennas. The classical Yagi-Uda antenna may be useful in meeting such demands, which however, becomes very large in size to achieve a high-gain performance due to a large number of directors as well as space required between those elements. In this paper, high-gain yet compact stacked multilayered Yagi antennas are proposed and demonstrated at 5.8 GHz for LPS applications. This structure makes use of vertically stacked Yagi-like parasitic director elements that allow easily obtaining a simulated gain of 12 dB. Two different antenna configurations are presented, one based on dipole geometry for single polarization, and the other on a circular patch to achieve dual polarization. The characteristics of these antennas with respect to various geometrical parameters are studied in order to obtain the desired performance. Measured results of the fabricated antenna prototypes are in good agreement with simulated results. The measured dipole Yagi antenna yields 11 dB gain over 14% bandwidth with a size of 80 × 80 × 29 mm3. Radiation patterns of the dual-polarized Yagi antenna are nearly identical to those of the single-polarized antenna, which has a size of 50 × 50 × 60 mm3, and also its two-port isolation is found to be as low as 25 dB over 4% bandwidth. The proposed antennas present an excellent candidate for compact and low-cost microwave and millimeter-wave integrated systems that require fixed or variable polarization capabilities and small surface footprint. [ABSTRACT FROM AUTHOR]