Internet of things applications require orientation insensitive wireless devices to maintain stable and reliable communication. The devices developed can also require positioning or a special protocol communication as Global Positioning System, Bluetooth Low Energy or Wi-Fi, which all implement a specific polarization, namely right hand circular (RHCP) and linear (LP) for the last two. For those reasons, antennas providing near-isotropic radiation patterns along with wide far-field sphere polarization coverage, including LP and RHCP, are highly demanded in IoT applications. In this paper, we present some theoretical limitations on the synthesis of an antenna with near-isotropic radiation and polarization patterns. We consider two models: a set of orthogonal Hertzian electric dipoles located at different points, as well as a model of Hertzian magnetic dipoles located on faces of a perfectly electric conducting cube. These models allow synthesizing the near-isotropic radiation and polarization patterns of an antenna based on short dipoles, as well as a cubic antenna with radiating patches on the cube faces.

The Internet of Things applications require small wireless sensors with quasi isotropic radiation, so that their placement is orientation insensitive. This paper shows the design steps for a microstrip patch based quasi-isotropic Antenna-in-Package (AiP). The structure proposed is a hollow cube with six microstrip patch radiators, one on each of its faces. The cubes internal walls are metallized to not only act as ground planes for the microstrip patch antennas, but also provide the necessary shielding between the radiators and the future embedded electronics. Thus, the problem in hand is to find the optimal phases to be applied to each patch so that when all six are activated simultaneously, the obtained radiation pattern is quasi-isotropic. Given the complexity of the structure, a simplified model of Hertzian magnetic dipoles was used to determine the phase each patch was to be excited to achieve the closest to an isotropic radiator as possible. A measured gain variation of 6.5 dB has been achieved for the entire 3D sphere after fabrication of a prototype. Keywords-Antenna in package (AiP), quasi isotropic radiation, Hertzian magnetic dipoles, microstrip patch antenna. I.

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With the era of Internet of Things (IoT), antennas that can adapt to different radio frequency environments have become highly desirable. These reconfigurable antennas must be compact to suit the futuristic IoT devices, be low cost for implementation on billions of devices, and be robust to the presence of nearby electronics. This paper demonstrates a novel 2.4 GHz 3D Cubic Antenna System, which comprises of a cube package with six microstrip patch antennas, one on each face. The system with embedded electronics, is aware of its orientation and reconfigures its radiation pattern automatically by switching ON the appropriate patch antenna for a focused communication with a boresight receiver. Alternately, if the position of the receiver is unknown, a quasi-isotropic radiation pattern can be achieved by providing the right phase conditions to all the patches to radiate simultaneously. The ground plane of the antennas provides a shield between the radiators and the electronics. In the focused mode, 10 dB more power is received as compared to the quasi-isotropic mode, which results in an energy efficient communication. While the quasi-isotropic mode provides an all-around radiation coverage with a gain variation of 6.4 dB for the entire 3D sphere, which is one of the best reported experimental value in literature for IoT compatible antenna systems.INDEX TERMS Intelligent antenna, electromagnetic shielding, automated reconfiguration, quasi isotropic radiation, switched beam antenna.

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