This paper presents a novel design of a wideband circular polarization 2 × 2 microstrip antenna array working at Ka-band frequencies, from 27.5 to 31 GHz. This module is highly integrable with new silicon beamformer chips, creating a unit cell that can be part of a large electronically steerable antenna for compact, ultra-low-profile, Satcom-on-the-move (SOTM) platforms. A multi-layer structure fabricated in standard printed circuit board (PCB) technology with high-yield substrates has been used. The radiating elements consist of double-stacked circular patches housed in a cavity and fed by H-shaped aperture coupling. It achieves a bandwidth of 16.5 % with a wide beam-width of 95° in the desired band, which is necessary for wide scanning angles in a large phased array. In the 2 × 2 unit cell, the antenna elements are distributed by means of a sequential rotation technique where the separation between two of them is 5.3 mm in the XY-plane. Broadside beam-widths ranging from 53.4° at 27.5 GHz to 42.1° at 31 GHz are achieved, with boresight directivities from 10.7 to 12.9 dBi, respectively, in both the RHCP and LHCP polarization. Moreover, mutual coupling levels below −20 dB and an axial ratio less than 3 dB in the whole band guarantee a good circular polarization purity.
The radio propagation for wireless systems embedded in surfboards has been characterized with the aim of testing the quality of a person to surfboard communication and person to infrastructure in aquatic environments, by means of Wireless Body Area Networks combined with an adequate transport technology. Wireless channel performance was analyzed using an in house developed 3D Ray Launching Method and validated by empirical measurements, showing good agreement with differences below 3dB, showing the influence of multipath components generated in this context as well as the strong influence of the average height of sea waves, which was introduced within the deterministic algorithm employed. The adoption of precise radioplanning techniques can aid in the deployment of efficient and cost effective new wireless solutions and optimal antenna location, applied to surfing and extendable to other aquatic sports and applications.Index Terms-WPAN, WSN, surfboard, 3D Ray Launching, aquatic environment, sea surface roughness.
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