This paper presents a novel four-sector shaped-beam antenna suitable for base station antennas in 60-GHz wireless local area networks (LANs). The antenna has a plateau configuration, whose four side walls have four linearly arranged microstrip antennas. Each trapezoidal facet excites a shaped beam in the elevation plane in order to meet link-budget requirement between base station and remote terminal, taking account of directional patters of remote terminal antennas. Low-loss curved microstrip-line is applied to connect the three-dimensional antennas with active circuits mounted on a flat carrier plate. This antenna has been adopted as the base station antenna in 60-GHz wireless LANs. The first-stage transmission experiment confirms the usefulness of shaped-beam antennas in the 60-GHz band.

A novel dual-band internal antenna similar in size to the single-band internal antenna for cellular handsets is proposed. Our approach to realize a small and low-profile dual-band internal antenna is to use the dominant mode (TM10 mode) and the higher-order mode (TM30 mode). In order to use this approach for recent dual-band cellular systems it is necessary to lower the resonant frequency of the higher-order mode (TM30 mode). This motivated our development of a new antenna configuration with a slot on the radiation element of a quarter-wavelength shorted microstrip antenna to lower the resonant frequency of the TM30 mode. In this paper, the experimental and the analytical results for this antenna are presented. In the results, by adjusting the location and the length of the slot, the dual-frequency operation can be achieved with the frequency ratio (TM30 mode/TM10 mode) from 2 to 3. In addition, the enhancement of bandwidth is presented.

The authors propose a new circular polarization method for a slot-coupled microstrip antenna. The simple configuration antenna in which a parasitically excited slot exists in addition to a directly excited slot generates circular polarization, by the effect of higher order modes. Experimental results and numerical results using the Spatial Network Method are described to verify the performance and discuss the circular polarization generating mechanism.

A new circularly polarized microstrip antenna fed by a cross slot using an aperture coupled feed is proposed. The proposed antenna has no 90 degree hybrid coupler for circular polarization and allows easy connection to microwave devices for electronical beam scanning. In this paper, the conditions for circular polarization in this new antenna are derived, and the measured results are also described to verify the authors' proposed conditions for circular polarization. Good return loss and axial ratio characteristics have been obtained.