This research aims to assess the signal propagation behavior of millimeter waves (mmWaves) over maritime environments. It focuses on the path loss performance of shore-to-vessel and vessel-to-vessel overwater communication at 28 GHz when considering line-of-sight conditions. The study is conducted by means of synthetic simulations at four different receiver antenna heights with respect to the water surface, representing emerging maritime Internet-of-Things application scenarios. Simulation results are shown concerning the path loss and the excess path loss - additional path loss relative to that in free-space - for each particular antenna height, over different TX-RX separations. We also show the cumulative distribution function of the excess path loss. The outcomes reveal variations of up to 10 dB in path loss performance depending on the height-distance setup. The results also reveal an initial distance range for all antenna heights in which the excess path loss is below 3 dB with 90% probability.

Two-Ray Model Analysis for Overwater Communication at 28 GHz with Different Heights

Assessing short-range Shore-to-Shore (S2S) and Shore-to-Vessel (S2V) WiFi communications

In this paper, a 1-bit phase-reconfigurable aperture coupled equivalent magnetic dipole element operating at the Cband is proposed. The element contains a symmetrical feeding network and an equivalent magnetic dipole placed on the ground. By utilizing two PIN diodes, various feeding paths can be selectively activated to achieve a 1-bit reconfigurable phase shift (0°/180°). Simulated results show that the half-power beam-width (HPBW) of the E-plane and H-plane at 5.8 GHz are 155° and 100° under radiation boundary conditions, respectively. The element has the advantages of compact structure, wide beam and reconfiguration, which has certain application prospects in wide-angle scanning phased array.

A 1-Bit Phase-Reconfigurable Equivalent Magnetic Dipole Element Applied to Wide-Angle Scanning Phased Array

A wideband high-efficiency metal-only folded reflectarray antenna (FRA) using 3-D subwavelength detachable trapezoidal grooved element (SDTGE) is proposed in this communication. The presented element is made up of two orthogonally rectangular metal plates etched with two trapezoidal grooves. It allows the reflection phases of the two linearly polarized (LP) waves to be shifted independently by varying the lengths of the grooves. To make a detachable structure, a sliding groove is employed on one of the two metal plates to help assembly. By setting the period to a subwavelength, a smooth phase shift response is obtained to extend the bandwidth. In addition, a large reflection phase variation of 670° at 10.0 GHz and a low element loss of nearly 0 dB are obtained to further enhance the gain. Then, a $35\times 35$ element reflective aperture spatially fed by a 3-D printed pyramidal horn antenna is designed and measured to verify the performance. The measured results exhibit that a wide 1-dB gain bandwidth of 26.5% is achieved. To reduce the profile, a wideband triple-layer polarization selector suspended on the reflective aperture is designed to achieve an FRA prototype. It features a maximum gain of 29.2 dBi corresponding to an aperture efficiency of 51.8% and a 3-dB gain bandwidth of over 34.2%. These results indicate that this metal-only FRA (MOFRA) has advantages of wide bandwidth and high efficiency.

A Wideband High-Efficiency Metal-Only Folded Reflectarray Using Subwavelength Detachable Trapezoidal Grooved Element

Unmanned aerial vehicles (UAVs) have enabled the unmanned management of water areas. Path loss (PL) serves as a critical factor that affects the UAV communication quality. In this work, a PL model for UAV channel in water scenarios is proposed, aiming to explore the multidimensional relationship between transceiver distance, carrier frequency, UAV height, and PL by constructing an Artificial Neural Network (ANN). Moreover, channel measurements are conducted in a river area, and the obtained data are analyzed using the proposed ANN model as well as the close-in (CI) model. The analysis results demonstrates that the PL increases initially and then declines as the UAV height increases. The proposed ANN model has higher prediction accuracy than the classic empirical model, and can achieve precise prediction of the PL in water scenarios. 

Measurement-based Path Loss Prediction and Analysis in Water Scenarios

This letter proposes a path loss model in urban water–land environments for line-of-sight (LOS) and non-LOS (NLOS) propagation at millimeter-wave (mm-wave) band, in which water surface reflection and building diffraction are considered simultaneously. An extensive measurement campaign in a campus pond environment at 28 GHz is conducted. Other channel characteristics, such as power delay profile and root-mean-square delay spread are also analyzed. Results indicate that the proposed model can predict the path loss in urban water–land environments accurately. This work can be applied to the deployment of wireless networks in urban water–land environments.

Path Loss Modeling in Urban Water–Land Environments at 28 GHz: Considering Water Surface Reflection and Building Diffraction

A 2-bit electronically planar reconfigurable array antenna (PRAA) at Ku band is presented in this letter. The proposed PRAA element employs the hybrid phase control method to realize the reconfiguration of its radiation structure and feeding structure. The radiation structure is designed as a O-slot radiation patch integrated with two p-i-n diodes to obtain a 1-bit phase quantization. To obtain the 2-bit phase control ability, a digital phase shifter with two p-i-n diodes is integrated in the feeding structure to obtain additional 90° phase shifting. Then, a 4 × 4-element subarray is designed and simulated, which is fed by using an asymmetric 16-way stripline feeding network. To realize 2-D beam scanning, an 8 × 8-element PRAA prototype is fabricated and measured, which is composed of four subarrays stitched together. The measured gain of the pencil beam is 20.8 dBi at 12.2 GHz with aperture efficiency of 60.0%, while the 3-dB gain bandwidth is 13.9% (11.4 - 13.1 GHz). The measured results verify that the proposed PRAA has good 2-D beam scanning capability within ±45°. In addition, the height of the PPRA prototype is only 0.3λ 0 , which indicate this design has a highly integrated, planar, low-profile structure.

A 2-Bit Electronically Planar Reconfigurable Array Antenna with 2-D Beam-Scanning Capacity Using Hybrid Phase Control Method

This brief presents a miniaturized wideband circularly polarized magneto-electric dipole antenna using <inline-formula> <tex-math notation="LaTeX">$\Psi $ </tex-math></inline-formula>-shaped phase shifter. Its magneto-electric dipole structure utilizes four L-section patches attached to outer edges of four square patches to achieve miniaturization. A parasitic patch positioned above the dipole structure is employed as an impendence transformer to extended the bandwidth. Meanwhile, a notched cavity equivalent to four magnetic dipoles is set around the dipole structure to enhance the beamwidth. To achieve circularly polarized wave, a feeding network composed of four-order Wilkinson power divider and <inline-formula> <tex-math notation="LaTeX">$\Psi $ </tex-math></inline-formula>-shaped phase shifter is designed to realize two equal-amplitude outputs with 90° phase difference. The <inline-formula> <tex-math notation="LaTeX">$\Psi $ </tex-math></inline-formula>-shaped phase shifter utilizes an open-short stub combining open circuit and short circuit, then achieving 106.9% impendence bandwidth with low insertion loss of 0.03 dB at 1.5 GHz. Then, the proposed antenna is fabricated with a compact size of <inline-formula> <tex-math notation="LaTeX">$0.5{\lambda }_{0} \times 0.5{\lambda }_{0} \times 0.3{\lambda }_{0}\,\,({\lambda }_{0}$ </tex-math></inline-formula> at 1.5 GHz). The measured results show that its impedance bandwidth is 94.6% while the 3-dB axial ratio bandwidth reaches 107.1%. The maximum half-power beamwidth reaches 144°/135° at -45°/45°-plane within the band from 0.78 GHz to 2.15 GHz while maximum axial ratio beamwidth respectively obtains 182°/203° in -45°/45°-planes.

A Miniaturized Wideband Circularly Polarized Magneto-Electric Dipole Antenna With Wide Beamwidth Using Ψ-Shaped Phase Shifter

This work introduces an all-meta high-gain folded reflectarray antenna (FRA) for mm-wave applications. The proposed FRA consists of a reflectarray aperture and a linearly polarized feed with a wide operating frequency band on the bottom layer, and a simple grid polarizer on the top layer. The simple polarized grid is a single-layer structure consisting of a series of parallel metal strips. The polarized grid has the ability to reflect one linearly polarized wave while transmitting its orthogonal linearly polarized wave. The reflectarray is composed of dual-polarization elements who have excellent orthogonal polarization isolation, and an open-ended waveguide is selected as the feed. According to the results of the simulation, the elements provide a significant phase variation of about 540° with low losses in the 200-240 GHz frequency band. Meanwhile, a wideband FRA with a size of 13.6×13.6 mm is designed and simulated. According to simulation results, the suggested FRA achieves a 3 dB gain bandwidth of 29.5%, a peak gain of 27.8 dBi, and a peak aperture efficiency of 48.4% at 220 GHz.

Design of an All-Metal High-Gain Folded Reflectarray for Mm-Wave Application

ABSTRACT A hybrid phase error analysis for dual-polarized reflectarray antenna using asymmetric split patch element is proposed in this article. The asymmetric split patch consists of a four-leaf patch and two split rings of different size where small one makes the patch asymmeric along y-axis and large one is used for impedance matching. And a complete 360° phase shift is obtained by using variable-size approach and flipping split patch 180° along y-axis. Then, we use hybrid phase error analysis approach to analyze and optimize the influence of phase sensitivity, quasi-periodic influence and phase constant on the reflectarray antenna. The simulated results show that maximum of element phase sensitivity is reduced by 275°/mm and element quasi-periodic phase error is dropped by 38°. Furthermore, dual-polarized reflectarray composed of 676 asymmetric split patch elements is designed, fabricated and measured. The measured gain of the proposed antenna is 29.9 dBi @10.0 GHz with aperture efficiency of 46%. The −1 dB gain bandwidth is 12% @10.0 GHz. The measured results show that the proposed antenna can improve phase accuracy effectively by using hybrid phase error analysis approach with asymmetric split patch.

Hybrid phase error analysis for dual-polarized reflectarray antenna using asymmetric split patch element

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