Abstract
When an electrically small antenna is conceived, designed, simulated, and tested, the main emphasis is usually placed immediately on its impedance bandwidth and radiation efficiency. All too often it is assumed that its directivity will only be that of a Hertzian dipole and, hence, its directivity becomes a minor consideration. This is particularly true if such a compact antenna radiates in the presence of a large ground plane. Attention is typically focused on the radiator and its size, while the ground plane is forgotten. This has become a too frequent occurrence when antennas, such as patch antennas that have been augmented with metamaterial structures, are explored. In this paper, it is demonstrated that while the ground plane has little impact on the resonance frequency and impedance bandwidth of patch antennas or metamaterial-inspired three-dimensional magnetic EZ antennas, it has a huge impact on their directivity performance. Moreover, it is demonstrated that with both a metamaterial-inspired two-element array and a related Huygens dipole antenna, one can achieve broadside-radiating electrically small systems that have high directivities. Several common and original designs are used to highlight these issues and to emphasize why a fundamental figure of merit such as directivity should never be overlooked.
Highlights
As mobile platform and the internet-of-things move into serious 5G research and development efforts, one antenna/ array performance characteristic frequently mentioned is directivity
There has been little discussed in the literature directly about the directivity of electrically small antennas
Because the ground plane size usually is already many times larger than the patch, it does not play a role in variations in the impedance matching or radiation efficiency
Summary
As mobile platform and the internet-of-things move into serious 5G research and development efforts, one antenna/ array performance characteristic frequently mentioned is directivity. To the 3D magnetic EZ antenna, to the use of two-element NFRP antenna arrays, and to a multiple NFRP element antenna, directivity and FTBR values will be emphasized to characterize these different compact and electrically small antenna systems These various examples will illustrate how one tailors their designs to obtain radiated power emitted primarily into one hemisphere, which would be an advantageous performance characteristic for a variety of current and future 5G applications. The latter include biomedical monitoring and on-body systems; point-to-point communications and wireless power transfer; mitigation of cell-phone specific absorption rate issues; and radio frequency identification devices. Several of the integrated components are based on the Rogers DuroidTM 5880 copper cladded substrate
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