The center-feed in a single-layer slotted waveguide array[1]-[3] is one of the key components in polarization division duplex (PDD) wireless systems. Two center-feed arrays with orthogonal polarization and boresight beams are orthogonally arranged side-by-side for transmission and reception, simultaneously. Each antenna has extremely high XPD (almost 50 dB in measurement) and a very high isolation (over 80 dB in measurement) between two arrays is observed provided the symmetry of slot arrangement is preserved [4]. Unfortunately, the area blocked by the center feed causes high sidelobe levels. This paper proposes the ridged cross-junction multiple-way power divider for realizing blockage reduction and symmetrical slot arrangement at the same time.

The radiation patterns of a circularly polarized GPS microstrip disk antenna mounted on the roof of a car are analyzed using UTD. Based upon the excellent agreements between the calculated and the measured results in all the observation directions, the effects of the antenna location upon radiation patterns are discussed in detail. As the distance between the antenna and the edge decreases, the gain in the low elevation angle on the same side as the edge considerably decreases. The effects of the earth are also extracted. They cause the fine ripples in the low elevation angle, though they are negligible in macroscopical view. Furthermore, the validity of the simple design neglecting the earth and the plates other than roof is investigated. The errors are localized at low elevation angle. The results obtained in this paper are useful in the design of the general antennas for mobile communication.

A circularly-polarized planar array antenna using hexagonal aperture elements is proposed. A 22-element subarray as the basic unit is excited by a corporate-feed circuit located in the lower layer of the double-layered antenna. The hexagonal aperture is designed to achieve a good axial ratio in the boresight. A 1616-element array antenna with uniform element spacing smaller than the free-space wavelength was fabricated by diffusion bonding of laminated thin metal plates for the 60 GHz-band. The high gain of 33.4 dBic is measured with 91.6% antenna efficiency, including losses.