Abstract
Quasi-isotropic antennas are promising candidates due to their applications in modern communication systems, where full spatial coverage and/or uniform signal reception is required. In this work, an in-depth review of quasi-isotropic antennas is presented, with the aim of understanding the working principles of such antennas and presenting the recent advancements, challenges, and solutions offered by various researchers. First, different design techniques adopted to achieve quasi-isotropic patterns, such as the use of complementary dipoles, multiple monopoles or dipoles, and an array of discrete elements are discussed. Then, different types of quasi-isotropic antennas—for example, planar, electrically small, 3-D printed, dual-band/wideband, circularly polarized, metamaterial-inspired, and dielectric resonator-based quasi-isotropic antennas—are revisited. Their applications in various technologies, such as RFID, energy harvesting, wireless sensor networks, and the IoT, are briefly explained. Lastly, different key performance parameters, such as complexity of configuration, design approach, physical profile, far field and radiation characteristics, reflection coefficients, operating frequency and bandwidth, gain deviation, and fabrication process, are discussed and tabulated. This review not only provides a guideline but will also help antenna engineers in designing a quasi-isotropic antenna with desirable performance.
Highlights
Wireless networks are a cost-effective and scalable alternative to cable networks for a wide range of applications, as using cables in complex control environments presents prohibitive costs and practical difficulties
According to the concept of complementary dipoles [2], [3], [14], when two equivalent dipoles are fed with two signals of the same amplitude and quadrature phase, the maximum-field direction of the one is along the null-field direction of the other one
At the second frequency, the y-oriented folded split-ring resonators (FSRR) resonated only acting as an electric dipole in the y-axis and magnetic dipole in the x-axis, resulting in dual-polarization in yz-plane
Summary
Wireless networks are a cost-effective and scalable alternative to cable networks for a wide range of applications, as using cables in complex control environments presents prohibitive costs and practical difficulties. Wireless networks are considered a crucial infrastructure in industries for mission-critical control systems, such as automation, monitoring, power grid protection, IoT devices, and many more. In such situations, instability, or interruption in communication links can have a substantial impact on the performance of the system. Isotropic antennas that can provide full spatial coverage are currently fictional, and cannot be realized theoretically. This is because the transverse electric field in the far field region cannot be uniform over a sphere if the field is linearly polarized everywhere [2], [3]. Scientists have proposed null-free quasi-isotropic antennas [4]
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