A Compact Dual-Polarized Filtering Antenna with Steep Cut-Off for Base-Station Applications

© 2022 IEEE - All rights reserved. This is the accepted manuscript version of an article which has been published in final form at https://doi.org/10.1109/TAP.2022.3161280 ​​​​​​​A dual-polarized filtering antenna with steep cut-off and compact size is developed for base station applications. In this design, four controllable radiation nulls are obtained by utilizing split rings, slotted T-shaped branches, a single-stub tuner, and a parasitic loop. Split rings are firstly used as the dipole arms to obtain the 1st radiation null at upper out-of-band. Four T-shaped branches working as DGS are printed under the crossed dipoles to achieve the 2nd radiation null. The connected outer conductors of the differential feed structure acting as a single-stub tuner can provide the 3rd radiation null to further enhance the upper-band rejection. Finally, a parasitic loop is incorporated around the split rings, and the out-of-band rejection of the lower-band is further enhanced by the 4th radiation null. More importantly, the impedance bandwidth of the antenna can be expended with two newly introduced resonant modes. As a result, a compact filtering antenna with a wide operational bandwidth of 1.7- 3.01 GHz (56%) is realized for |Sdd11| < -15 dB with the isolation higher than 38 dB. The out-of-band suppression is higher than 18.4 dB in 3.1-4.5 GHz and more than 47 dB in 0.8-1.1 GHz.Peer reviewedFinal Accepted Versio

Novel Pseudo Magneto-electric Dipole Antennas

One of the major requirements for modern wireless communications is very high data transmission, so antennas with simple geometry, wide operation bandwidth and stable high gain features are in increasing demand. In this thesis, three novel pseudo magneto-electric (ME) dipole antennas operating in 5G Frequency Range 1 (FR1) sub-6GHz and Frequency Range 2 (FR2) millimeter-wave (mmW) band are introduced and analyzed. Comparing with conventional ME dipole antennas, which always require a vertical quarter-wave cavity to generate the magnetic dipole resonance, the pseudo-ME dipole designs proposed in this thesis do not rely on the cavity to provide the complementary magnetic dipole mode, therefore, they have extremely simple geometry. Meanwhile, it achieved wide bandwidth (50.30%) and high gain (average 8.74 dBi) the in-band gain variation is only ± 1dB. Based on the novel cavity-less Pseudo-ME dipole antenna geometry, a wide axial ratio bandwidth (54.1%) circularly polarized pseudo-ME dipole antenna is also designed to overcome the polarization misalignment problem in multipath-rich wireless environments, this antenna has two pairs of orthogonal electric dipoles and magnetic dipoles to achieve the wide axial ratio bandwidth performance. Finally, an aperture-coupled printed pseudo-ME dipole antenna is designed for operating in millimeter-wave band, it has 32.3% of impedance bandwidth and stable high gain 7.4 ± 0.8 dBi. Especially, there is none typical via-hole formed cavity in the geometry, so the fabrication of the mmW band antenna becomes simpler

Compact-Size Wideband Antennas and Arrays for Wireless Communications

Polarization is an important parameter for characterizing antenna systems. Dual-polarized and circularly-polarized wideband antennas with compact size are very useful for mobile communications and satellite communications. Due to the multipath propagation and shadowing in urban environment, radio signals received by mobile terminals can become very weak. Dual-polarized antennas can achieve better signal quality in mobile communications by using polarization diversity. Wideband circularly polarized antennas are very important for mobile satellite communications as circularly polarized signals are immune to Faraday rotation effects. Circular polarization also enables mobile satellite communications without strict alignment between transmit and receive antennas. Therefore, dual-polarized antennas and circularly polarized antennas have been drawn increasing popularity in the wireless communication systems. In this thesis, several novel designs of compact, wideband, and specially functioned antennas and arrays are developed for wireless communication applications. First, wideband antennas and arrays are investigated for base station applications with different appealing features, such as compact radiator size, enhanced upper out-of-band suppression, or low pattern sidelobes. They are designed with different novel design concept, such as shared-dipole, electromagnetic dipoles, shorted dipoles, and fourth-order coupling structure. Then, to directly match to the newly emerged differential circuit systems, several wideband differentially fed dual-polarized antennas are proposed for base station applications. They are designed for high common mode suppression, high harmonic suppression, or compact radiator size by using the idea of orthogonal six-port power divider, multi-resonance structure, and crossed open loop resonators. The final designs are two circularly polarized antennas, which have the wide overlapped impedance and axial ratio bandwidth, or dual circularly polarized radiations realized by using crossed open slot-pairs, orthogonal power diver, and phase shift unit cells. The working principles of these different antennas are extensively illustrated with the relevant design theories and detailed structure studies. The performances of these antennas and arrays are evaluated first by the full-wave electromagnetics simulations, and followed by the measurements of the corresponding fabricated prototypes. Good agreements between the simulated and measured results are obtained. With these different features to accommodate different requirements, these antennas and arrays can be the good candidates for the wireless communication systems

Wideband and UWB antennas for wireless applications. A comprehensive review

A comprehensive review concerning the geometry, the manufacturing technologies, the materials, and the numerical techniques, adopted for the analysis and design of wideband and ultrawideband (UWB) antennas for wireless applications, is presented. Planar, printed, dielectric, and wearable antennas, achievable on laminate (rigid and flexible), and textile dielectric substrates are taken into account. The performances of small, low-profile, and dielectric resonator antennas are illustrated paying particular attention to the application areas concerning portable devices (mobile phones, tablets, glasses, laptops, wearable computers, etc.) and radio base stations. This information provides a guidance to the selection of the different antenna geometries in terms of bandwidth, gain, field polarization, time-domain response, dimensions, and materials useful for their realization and integration in modern communication systems

Wideband Dual-Polarized Antenna with High Selectivity for 5G Sub-6GHz Base Station Applications

A dual-polarized antenna with wide impedance bandwidth and high selectivity is presented for the use of 5G sub-6GHz base stations. By strategically introducing a novel coupled dual-mode grid structure, two additional resonant modes (One is in-band, another one is out-of-band) as well as two radiation nulls can be obtained to enhance the impedance bandwidth and out-of-band rejection level of the widely used tightly coupled cross-dipole antenna. The two radiation nulls introduced by the grid structure are located at the two edges of the desired frequency band. To further improve the gain suppression level in higher out-of-band, a new radiation null is obtained by symmetrically introducing four T-shaped strips. Apart from these additional radiation nulls, this antenna also exhibits two inherent radiation nulls originating from its feed structure and reflector. The measured results demonstrate that the proposed antenna exhibits a wide impedance bandwidth of 39.5% (ranging from 3.07 GHz to 4.58 GHz), excellent isolation of over 31 dB, and a notable out-of-band rejection level exceeding 17.6 dB and 19.2 dB in the frequency bands of 1.7 GHz-2.7 GHz and 4.8 GHz- 5.0 GHz

Next Generation of Magneto-Dielectric Antennas and Optimum Flux Channels

abstract: There is an ever-growing need for broadband conformal antennas to not only reduce the number of antennas utilized to cover a broad range of frequencies (VHF-UHF) but also to reduce visual and RF signatures associated with communication systems. In many applications antennas needs to be very close to low-impedance mediums or embedded inside low-impedance mediums. However, for conventional metal and dielectric antennas to operate efficiently in such environments either a very narrow bandwidth must be tolerated, or enough loss added to expand the bandwidth, or they must be placed one quarter of a wavelength above the conducting surface. The latter is not always possible since in the HF through low UHF bands, critical to Military and Security functions, this quarter-wavelength requirement would result in impractically large antennas. Despite an error based on a false assumption in the 1950’s, which had severely underestimated the efficiency of magneto-dielectric antennas, recently demonstrated magnetic-antennas have been shown to exhibit extraordinary efficiency in conformal applications. Whereas conventional metal-and-dielectric antennas carrying radiating electric currents suffer a significant disadvantage when placed conformal to the conducting surface of a platform, because they induce opposing image currents in the surface, magnetic-antennas carrying magnetic radiating currents have no such limitation. Their magnetic currents produce co-linear image currents in electrically conducting surfaces. However, the permeable antennas built to date have not yet attained the wide bandwidth expected because the magnetic-flux-channels carrying the wave have not been designed to guide the wave near the speed of light at all frequencies. Instead, they tend to lose the wave by a leaky fast-wave mechanism at low frequencies or they over-bind a slow-wave at high frequencies. In this dissertation, we have studied magnetic antennas in detail and presented the design approach and apparatus required to implement a flux-channel carrying the magnetic current wave near the speed of light over a very broad frequency range which also makes the design of a frequency independent antenna (spiral) possible. We will learn how to construct extremely thin conformal antennas, frequency-independent permeable antennas, and even micron-sized antennas that can be embedded inside the brain without damaging the tissue.Dissertation/ThesisDoctoral Dissertation Electrical Engineering 201