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

A Wideband Differentially Driven Dual-Polarized Antenna by Using Integrated Six-Port Power Divider

A new method to design wideband differentially driven dual-polarized antenna with high common mode suppression and high port isolation is presented. The presented antenna can be equivalent as a combination of a six-port power divider and four crossed folded dipoles. The six-port power divider is composed of two orthogonal input ports and four equal magnitude output ports. The detailed analysis illustrates that the six-port power divider can have wide bandwidth and high isolation under odd mode excitation and high common mode suppression under even mode excitation. Therefore, based on the wideband and high even mode suppressed six-port power divider, a wideband differentially driven dual-polarized antenna is developed with high common mode suppression. To validate the design concept, the proposed antenna was designed, fabricated, and measured. The measured results prove that the antenna has a wide impedance bandwidth of 1.64-3.0 GHz (58.6%) for the return loss higher than 15 dB and isolation higher than 35.4 dB. In addition, very high common mode suppression is achieved for the measured common mode reflection coefficient higher than -0.87 dB over the entire bandwidth. With stable antenna gain and half power beamwidth, the develop antenna is suitable for base station applications

Antenna/Propagation Domain Self-Interference Cancellation (SIC) for In-Band Full-Duplex Wireless Communication Systems.

In-band full duplex (IBFD) is regarded as one of the most significant technologies for addressing the issue of spectrum scarcity in 5G and beyond systems. In the realization of practical IBFD systems, self-interference, i.e., the interference that the transmitter causes to the collocated receiver, poses a major challenge to antenna designers; it is a prerequisite for applying other self-interference cancellation (SIC) techniques in the analog and digital domains. In this paper, a comprehensive survey on SIC techniques in the antenna/propagation (AP) domain is provided and the pros and cons of each technique are studied. Opportunities and challenges of employing IBFD antennas in future wireless communications networks are discussed

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 Differentially Fed Dual-Polarized Antenna by Using Three-Strip Transmission Lines

A new method of designing a wideband differentially fed dual-polarized antenna by using three-strip transmission lines (TS-TLs) is presented. A wideband power divider composed of four TS-TLs is firstly proposed and illustrated by using its equivalent circuit. Based on the proposed power divider, a wideband differentially fed dual-polarized antenna with four in-band resonances is developed. To enhance the outof-band selectivity, two radiation nulls with quasi-elliptic response are obtained by utilizing the specifically designed structures in the TS-TL based power divider. The first radiation null at the lower out-of-band is produced by the resonance from the center strip of TS-TL and shorting coaxial cable. The second radiation null at the upper out-of-band is produced by the resonance from the slot formed by the dipole arm and the outer strip of TS-TL. Combining with the high 2nd -order harmonic suppression owing to the differentially fed method, the presented differentially fed antenna is demonstrated that it not only has high inband selectivity covering 1.67-2.91 GHz, but also has high out-of-band suppressions of 33.8 dB and 20.6 dB over the frequency bands of 0.6-1 GHz and 3.3-5 GHz. In addition, stable gain and beamwidth are achieved for base station applications

Wideband Dual-Polarized Filtering Antenna for Base Station Applications

A compact wideband dual-polarized filtering antenna based on tightly coupled cross dipoles is presented in this letter. The enhancement of impedance bandwidth is realized by introducing four impedance equalizers to equalize the input resistances of the two inherent resonant modes of tightly coupled cross dipole antenna. The enhancement of the selectivity is realized by introducing two radiation nulls in 5G sub-6 GHz n77 and n79 bands. The radiation null in n77 band is obtained by introducing the cross strips in the center of the antenna. The radiation null in the n79 band is achieved by the introduction of open-end branches. The manipulation of their key parameters allows for independent control over both radiation nulls. The validity of the antenna's design principle was confirmed by carrying out fabrication and measurements. The results obtained showcase the antenna's broad fractional bandwidth of 63.4% and exceptional port isolation of 31 dB. High out-of-band rejection levels in n77 and n79 bands are also obtained. In addition, since the whole radiator of the presented antenna is coplanar, it offers the advantage of a simple structure and convenient manufacturing, making it highly suitable for the use in base stations operating across multiple bands

Millimeter-Wave Components and Antennas for Spatial and Polarization Diversity using PRGW Technology

The evolution of the wireless communication systems to the future generation is accompanied by a huge improvement in the system performance through providing a high data rate with low latency. These systems require access to millimeter wave (mmWave) bands, which offer several advantages such as physically smaller components and much wider bandwidthcomparedtomicrowavefrequencies. However, mmWavecomponentsstillneed a significant improvement to follow the rapid variations in future technologies. Although mmWave frequencies can carry more data, they are limited in terms of their penetration capabilities and their coverage range. Moreover, these frequencies avoid deploying traditional guiding technologies such as microstrip lines due to high radiation and material losses. Hence, utilizing new guiding structure techniques such as Printed Ridge Gap Waveguide (PRGW) is essential in future mmWave systems implementation. ThemainpurposeofthisthesisistodesignmmWavecomponents,antennasubsystems and utilize both in beam switching systems. The major mmWave components addressed in this thesis are hybrid coupler, crossover, and differential power divider where the host guidingstructureisthePRGW.Inaddition,variousdesignsfordifferentialfeedingPRGW antennas and antenna arrays are presented featuring wide bandwidth and high gain in mmWave band. Moreover, the integration of both the proposed components and the featured antennas is introduced. This can be considered as a significant step toward the requirements fulfillment of today's advanced communication systems enabling both space and polarization diversity. The proposed components are designed to meet the future ever-increasing consumer experience and technical requirements such as low loss, compact size, and low-cost fabrication. This directed the presented research to have a contribution into three major parts. The first part highlights the feeding structures, where mmWave PRGW directional couplers and differential feeding power divider are designed and validated. These components are among the most important passive elements of microwave circuits used in antennabeam-switchingnetworks. Different3-dBquadraturehybridcouplersandcrossover prototypes are proposed, featured with a compact size and a wide bandwidth beyond 10 % at 30 GHz. In the second part, a beam switching network implemented using hybrid couplers is presented. The proposed beam switching network is a 4 × 4 PRGW Butler matrix that used to feed a Magneto-electric (ME) dipole antenna array. As a result, a 2-D scanning antenna array with a compact size, wide bandwidth, and high radiation efficiency larger than84%isachieved. Furthergainenhancementof5dBiisachievedthroughdeployinga hybridgainenhancementtechniqueincludingAMCmushroomshapesaroundtheantenna array with a dielectric superstrate located in the broadside direction. The proposed scanning antenna array can be considered as a step toward the desired improvement in the data rate and coverage through enabling the space diversity for the communication link. The final activity is related to the development of high-gain wide-band mmWave antenna arrays for potential use in future mmWave applications. The first proposed configuration is a differential feeding circular polarized aperture antenna array implemented with PRGW technology. Differential feeding antenna designs offer more advantages than single- ended antennas for mmWave communications as they are easy to be integrated with differential mmWave monolithic ICs that have high common-mode rejection ratio providing an immunity of the environmental noise. The proposed differential feeding antenna array is designed and fabricated, which featured with a stable high gain and a high radiation efficiency over a wide bandwidth. Another proposed configuration is a dualpolarized ME-dipole PRGW antenna array for mmWave wireless communication. Dual polarizationisconsideredoneofthemostimportantantennasolutionsthatcansavecosts and space for modern communication systems. In addition, it is an effective strategy for multiple-input and multiple-output systems that can reduce the size of multiple antennas systems by utilizing extra orthogonal polarization. The proposed dual- polarized antenna array is designed to achieve a stable gain of 15 ± 1 dBi with low cross- polarization less than -30 dB over a wide frequency range of 20 % at 30 GHz

Wideband Dual-Polarized Filtering Antenna for Base Station Applications

For the purpose of open access, the author has applied a CC BY public copyright licence to any Author Accepted Manuscript version arising from this submission.A compact wideband dual-polarized filtering antenna based on tightly coupled cross dipoles is presented in this letter. The enhancement of impedance bandwidth is realized by introducing four impedance equalizers to equalize the input resistances of the two inherent resonant modes of tightly coupled cross dipole antenna. The enhancement of the selectivity is realized by introducing two radiation nulls in 5G sub-6 GHz n77 and n79 bands. The radiation null in n77 band is obtained by introducing the cross strips in the center of the antenna. The radiation null in the n79 band is achieved by the introduction of open-end branches. The manipulation of their key parameters allows for independent control over both radiation nulls. The validity of the antenna's design principle was confirmed by carrying out fabrication and measurements. The results obtained showcase the antenna's broad fractional bandwidth of 63.4 exceptional port isolation of 31 dB. High out-of-band rejection levels in n77 and n79 bands are also obtained. In addition, since the whole radiator of the presented antenna is coplanar, it offers the advantage of a simple structure and convenient manufacturing, making it highly suitable for the use in base stations operating across multiple bands.Royal Society - International Exchanges 2019 Cost Share (NSFC); Huawei Technologies Ltd, in part by Engineering and Physical Sciences Research Council (EPSRC) (Grant Number: EP/S005625/1 and EP/N032497/1)

Compact Dual-Polarized Fabry-Perot Leaky-Wave Antenna for Full-Duplex Broadband Applications

A Fabry-Perot leaky-wave antenna (LWA) with dual-differential feeding is proposed for full-duplex (FD) scenarios by offering dual-linearly polarized radiation. The compact feed system includes slots within substrate integrated waveguide (SIW) technology to excite two orthogonal fields with high isolation. The 2-D LWA aperture field is constituted by a top partially reflective surface (PRS) or screen, and is realized by a superstrate PCB. Dispersive results for the proposed structure are also reported, suggesting that broadside radiation is possible from about 22 GHz. The fabricated antenna is also well matched from 22 GHz to about 25 GHz with isolation values greater than 40 dB. The 3− dB fractional bandwidth for broadside radiation is 10.5%, from about 22.5 GHz to 25 GHz. As compared to other FD antenna systems, the developed configuration is compact, provides dual-linear (orthogonal) polarization, also offering higher isolation levels, low cross-polarization (about − 40 dB), and high gain (16 dBi), whilst employing simple feeding. As further described in the paper, the prototyped dual-polarized LWA can be useful in 5 G and 6 G systems where FD is required