A Broadside Shared Aperture Antenna for (3.5, 26) GHz Mobile Terminals With Steerable Beam in Millimeter-Waveband

The shared aperture antenna is regarded as one of the promising approaches to support new frequencies with very efficient space utilization. To the best of the authors' knowledge, there are few shared aperture antennas that include both the sub-6 GHz antenna and the millimeter-wave (mm-wave) beam-steering array for broadside applications. In this article, a broadside sharing aperture technique is developed so that a 2 \times4\,\,26 GHz beam-steering substrate-integrated DRA (SIDRA) array can be integrated into a 3.5 GHz bandwidth enhanced perforated patch antenna in a coplanar and aperture-shared way. The proposed solution benefits from several aspects. First, the 3.5 GHz antenna features a compact size as this part is built on the substrate (where the mm-wave SIDRA is constructed) with a high permittivity. Second, the mm-wave SIDRA is a 3-D-type device, and in the case of coplanar integration, its height can be freely adapted to the thickness of 3.5 GHz antenna without concerning the impact from surface waves as many 2-D-type antennas have to do. Third, the antenna can be implemented with the multi-layer printed circuit board (PCB) process, yielding a high integrity level. The dual-frequency antenna was designed, fabricated, and measured. The performances of the antenna are reported with reasonable agreement between the measured and simulated results observed.