IEEE Transactions on Antennas and Propagation

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ISSN / EISSN : 0018-926X / 1558-2221
Published by: IEEE (10.1109)
Total articles ≅ 16,602
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Tianqi Pei, , Jianpeng Wang, Wen Wu
IEEE Transactions on Antennas and Propagation, pp 1-1; doi:10.1109/tap.2021.3098565

Abstract:
In this paper, a new low-profile decoupling structure originated from the phase shift concept for the patch antenna array is proposed. To clearly illustrate the operation principle, the phase of the signal transmitted from Patch 1 to Patch 2 has been initially studied and the decoupling condition for two closely spaced patch antennas in H-plane has also been obtained. Afterwards, the decoupling element concisely composed of a half-wave microstrip line and a shorting pin is developed. Attributing to the introduction of additional signal path by the new decoupling structure, mutual coupling between two adjacent patches is effectively suppressed. To verify the feasibility of the proposed design scheme, demonstrators of two-element patch antennas with and without decoupling structure are respectively implemented and analyzed. Results indicate that compared with the coupled array, the isolation between two patch elements is enhanced from 7dB to 18dB at the center frequency of 3.16 GHz under the edge-to-edge separation of only 0.027λ0. Besides, owing to the single layer layout, the profile of the whole antenna structure is as low as 0.02λ0. Ultimately, the proposed decoupling scheme has been applied to the three-element counterpart, so as to demonstrate and validate its effeteness of isolation enhancement for multi-element patch array.
, Anke Schmeink
IEEE Transactions on Antennas and Propagation, pp 1-1; doi:10.1109/tap.2021.3098558

Abstract:
Robust channel models for indoor areas are a crucial part of network planning and are immensely valuable for the small cell and indoor 5G network evolution. As the main input for many resource allocation and network planning problems, the accuracy of the path loss model can improve the overall accuracy of these techniques. Previous measurement campaigns exist for outdoor areas and higher frequencies, however extensive indoor measurements at these frequencies is missing from the literature. Both WLAN and LTE networks use 2.4 GHz and 5 GHz bands. For this work, indoor measurements were carried out in two distinct indoor environments, at two frequencies, and various models were compared. The measurements were made at the Deutsches Museum Bonn and the ICT cubes, an office space at RWTH Aachen University. Both empirical and deterministic models are tested on the data, the free space path loss model, the single and dual slope models with line-of-sight and nonline-of-sight, ray tracing models, and artificial neural network models were all tested and evaluated. Overall, the artificial neural network combined with the free space path loss model proved to be the most robust model which accurately predicted the propagation in the indoor environments, at both frequencies.
Dehao Zhao, , HouJun Sun, Xiu Yin Zhang
IEEE Transactions on Antennas and Propagation, pp 1-1; doi:10.1109/tap.2021.3098561

Abstract:
In this paper, a dual-band substrate integrated waveguide (SIW) filtering antenna with improved out-of-band rejection is presented. It consists of two dual-mode rectangular cavity resonators integrated with the slot antenna. Four metal-insulator-metal (MIM) capacitors are designed in the first cavity to realize circuit miniaturization and wide upper stopband. The second slot-loaded cavity achieves a miniaturized dual-band radiation by cutting the currents of TE110 and TE210 modes. Three radiation nulls are obtained due to the multiple coupling paths between the resonating and spurious modes. The radiation nulls locations can also be adjusted by changing the feeding position. For verification, a SIW filtering antenna operating at 3.6/4.1 GHz (f1/f2) is designed and fabricated. The measured peak gain and 10-dB bandwidth at low band of 3.57 GHz (high band of 4.12 GHz) are 4.84 dBi (4.85 dBi) and 2.3% (1.6%), respectively. The measured >30dB inner stopband suppression and 20-dB upper stopband suppression up to 1.46f2 are achieved.
Hao Li, Ziheng Zhou, Yue Li
IEEE Transactions on Antennas and Propagation, pp 1-1; doi:10.1109/tap.2021.3098548

Abstract:
In this communication, a novel dual-polarized (DP) epsilon-near-zero (ENZ) antenna is proposed with its operating frequencies independent to lengths for both polarizations. To obtain a DP implementation of ENZ antenna, an anti-phase epsilon-near-zero (AP-ENZ) mode is used based on a slot-fed substrate-integrated waveguide (SIW) antenna at its cutoff frequency, in which the electric field presents a sign function-like distribution, presenting a fixed operating frequency independent on length. The proposed DP length-irrelevant antenna design is composed by a cross-shaped SIW operating on two orthogonal AP-ENZ modes, which are excited by a cavity-backed cross-shaped slot with good port isolation. The SIW lengths for both polarizations can be tuned independently without disturbing the operation frequency with controllable radiation patterns. To be specific, we study two cases of different lengths where sidelobe elimination and high gain radiation are realized, respectively. To verify this design, two antenna prototypes Ant. 1 and Ant. 2 are fabricated and tested, exhibiting agreements between simulation and experiment. The proposed Ant. 1 presents no sidelobes at 2.42 GHz while Ant. 2 shows a high gain of 10.56 dBi from 2.45-2.55 GHz. The proposed design method enables antennas with a variety of radiation patterns to be designed at a fixed frequency and both symmetric and asymmetric patterns for DP antennas. It also inspires the design of a flexible antenna with unchanged operating frequency when folded in both dimensions.
Ling-Jun Yang, , Wei E. I. Sha, Zhixiang Huang, Jun Hu
IEEE Transactions on Antennas and Propagation, pp 1-1; doi:10.1109/tap.2021.3098604

Abstract:
This paper presents an efficient synthesis method for generating vortex beams based on donut-shaped orbital angular momentum (OAM) metasurfaces. It not only allows one to synthesize the vortex beam with an arbitrary combination of OAM modes and arbitrary mode energy distribution, but also avoids the undesired phase singularities in the conventional OAM metasurfaces. Three specific examples are implemented to verify the effectiveness of the synthesis method including single-mode, multi-mode, and equal-amplitude vortex beams. Based on the proposed constraint conditions, a donut-shaped metasurface is designed to generate a high-purity single-mode vortex beam. To generate high-performance multi-mode beams, a shape-related tailoring is further introduced to avoid the undesired phase singularities of the multi-mode OAM metasurfaces. Finally, the synthesized equal-amplitude vortex beams are generated and verified experimentally over a wide frequency range, which demonstrates robust and precise control of the vortex beams.
Jianfeng Zhu, , ShaoWei Liao, Quan Xue
IEEE Transactions on Antennas and Propagation, pp 1-1; doi:10.1109/tap.2021.3098559

Abstract:
This paper presents an aperture-shared dual-band large frequency-ratio high gain antenna for Sub-6 GHz and mmwave bands applications. Initially, the partially reflective surface (PRS) of the Fabry-Perot cavity (FPC) antenna operating at the Sub-6 GHz band is realized by using single-layered periodic grid patches while the opaque region of the mm-wave band FZP lens antenna is implemented by using periodic double-screen dipoles. Then, the PRS and the FZP lens are hybridized together and upgraded into a kind of composite metasurface, which simultaneously functions as the PRS of the Sub-6 GHz FPC antenna and the mm-wave band FZP lens with little dual-band mutual interference. Thus, the FPC antenna and the FZP lens can share the same aperture with high aperture reuse efficiency. Because the principles are based on the FPC resonance and the collimating Fresnel zone plate (FZP) lens, high gains are achieved at both bands without a feeding network. Meanwhile, a dual-band large frequency-ratio antenna is designed as the feed. A prototype working at 3 and 28 GHz bands is designed, fabricated, and measured to verify the idea.
Malathi Kanagasabai, Padmathilagam Sambandam, M. Gulam Nabi Alsath, SandeepKumar Palaniswamy, Abinaya Ravichandran, Cibita Girinathan
IEEE Transactions on Antennas and Propagation, pp 1-1; doi:10.1109/tap.2021.3098517

Abstract:
A compact body-worn circular polarized textile monopole antenna for wearable applications is reported. The proposed antenna is fabricated on a jean fabric providing flexibility, light-weight, and easy integration into human clothes. The overall size of the proposed antenna is 25 × 30 × 1.4 mm3. Circular polarization (CP) is advantageous for on-body communication as it provides features such as multipath immunity, suppressing interferences, and enables better link connectivity between the sensor nodes. The proposed antenna achieves the CP using an asymmetric stepped L-shaped ground plane and through the incorporation of cross-shaped stub in the radiator. The single fed octagonal strip monopole antenna provides good impedance matching over the entire ultra-wide frequency range from 3.09 -11 GHz. Simulation results are in good correlation with the measured results. Axial ratio bandwidth < 3 dB is achieved in the frequency range of 3.4-10 GHz. Gain and efficiency obtained are about 2.3-4.4 dBi and 65-82% at the said frequency range respectively. Structural deformation is performed to analyze the flexibility of the proposed antenna. The simulated SAR values follow the FCC limit making it most suitable for wearable applications.
Yinuo Li,
IEEE Transactions on Antennas and Propagation, pp 1-1; doi:10.1109/tap.2021.3098595

Abstract:
A high gain low-frequency bow-tie antenna with artificial magnetic conductor and metamaterial lens for ground penetrating radar (GPR) is proposed. Firstly, a bow-tie antenna working in 348-772 MHz frequency band is designed. The substrate is a square with side length of 420 mm. A periodic artificial magnetic conductor reflector is designed. The in-phase reflection region of the unit is 481 MHz-1.44 GHz. The results show that the gain of antenna loaded with reflector is increased by 5 dB. A metamaterial lens based on the zero-index metamaterial element is also proposed to improve the gain. The zero refractive index frequency point is 810 MHz, the unit size of the metamaterial is 60 mm, and the lens size is consistent with the antenna substrate size. The gain of the antenna loaded with artificial magnetic conductor (AMC) reflector and the metamaterial lens is increased by 6.5 dB and the front-to-back ratio is 23 dB. The directivity of the antenna is further optimized. The measured results are in good agreement with the simulations.
Hongcai Yang, , Yi Fan
IEEE Transactions on Antennas and Propagation, pp 1-1; doi:10.1109/tap.2021.3098542

Abstract:
broadband circularly polarized (BCP) all-textile antenna and its wearable conformal antenna array (WCAA) are investigated for body-centric communications. Initially, a circu-larly polarized (CP) microstrip patch antenna loaded with a piece of modified metasurface is designed to achieve wide impedance and axial ratio (AR) bandwidths. Characteristic mode analysis is employed to understand the operating mechanism, which pro-vides clear physical insight into each mode at various frequencies. Due to the adoption of textile (i.e., felt) as substrate and nylon conductive fabric as conductor, the proposed antenna is flexible, totally conforming to the curve-shaped human body. The antenna with broadside radiation is suitable for off-body communications. For verification, the prototype operating at 5-GHz (5.15–5.825 GHz) band was fabricated. The measured −10-dB impedance and 3-dB AR bandwidths of 35.1% and 17.5% with a peak gain of 8.5 dBi are achieved. Furthermore, the BCP antenna is used as element to constitute the WCAA and the omnidirectional radiation pattern in the azimuth plane is achieved for on-and off-body communications. The considerations about how to achieve omni-directional radiation and avoid radiation nulls are studied in detail. Lastly, the WCAA was fabricated and tested, the measured results guarantee its potential for wearable applications.
Majedehsadat Rad, Nastouh Nikkhah, , Mohammad Yazdi
IEEE Transactions on Antennas and Propagation, pp 1-1; doi:10.1109/tap.2021.3098516

Abstract:
In this paper, two wideband dual-polarized Dielectric Resonator Antennas (DRA) for X band radar applications are presented. The design procedure is started with designing a linear polarized DRA fed by a microstrip line. The feedline is optimized to excite the HEM11δ mode of DRA which corresponds to magnetic monopole like radiation. Then, a novel quadrature hybrid is designed in the feeding structure to provide both left (LHCP) and right-handed (RHCP) circular polarization. Finally, two antenna prototypes are fabricated and tested: a dual (right hand and left hand) circular polarization DRA with omni-directional pattern, and an enhanced gain version of dual-polarized CP DRA with a directive pattern. The measurement results of antennas confirm wideband impedance bandwidth (34% and 38.8%) as well as wideband Axial Ratio (AR) one (23% and 30%) in element and array structures, respectively. The antennas also provide both RHCP and LHCP radiation. The first antenna contains monopole-like radiation which is aimed at wireless systems with omnidirectional pattern requirements. The second, a 2*1 antenna array, which presents around 9 dB across the entire band. The presented antennas are good candidates for radar applications such as weather monitoring, air traffic control, and vehicle speed detection.
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