Loading metal rectangular pyramid method for reducing feed blockage of folded transmitarray antenna

: Electromagnetic (EM) wave propagation is the transmission of an EM wave between a transmitter and a receiver. If a particular point on the wave front is followed over time, the collection of point positions would define a ray. The ray would coincide with a line from the transmitter to the receiver. The purpose of this raytrace technique is to describe an EM wave's path in terms of rays, as the wave propagates through a laterally heterogeneous medium where the index of refraction is allowed to vary both vertically and horizontally.

A comprehensive study of electromagnetic waves underwater propagation for a wireless sensor network is introduced in this paper. A mathematical model for the path loss due to attenuation of electromagnetic waves propagates in sea and pure water is given. Reflection from the air-water and water-sand interfaces as a function of distance between sensors and water depth is also introduced. A high gain antenna is required to overcome the high value of path loss. A bow-tie antenna is very common antenna used for underwater wireless communication applications. A high gain bow-tie antenna is designed and simulated using FEKO software. The antenna performance parameters studied in this paper are return loss, voltage standing wave ratio, input impedance and gain.

Metasurfaces have been extensively studied for generating electromagnetic waves carrying orbital angular momentum (OAM). In particular, programmable metasurfaces enable real‐time switching between multiple OAM modes in a digital manner. However, the current programmable metasurfaces are mostly based on reflective mode, which suffer from low efficiency as well as serious feed blockage. In this paper, a transmissive programmable metasurface is presented for the highly efficient generation of multimode convergent OAM beams. The proposed transmissive metasurface is composed of electronically reconfigurable units with 1‐bit phase resolution (0/π), which are obtained by integrating two PIN diodes in the radiating layer for current direction modulation. Through the antisymmetry configuration of the two PIN diodes, nearly uniform transmission magnitudes but inversed phase states in a wide band can be obtained. The simulation results show that the proposed reconfigurable unit can achieve good 1‐bit phase tuning, with minimum insertion loss of 0.2 dB and 2 dB transmission bandwidth of more than 10%. Through the dynamic modulation of the quantized code distributions on the metasurface, programmable multimode OAM beams can thus be constructed. Both simulated and measured results verify the effectiveness of the proposed design.

In this report, we consider the amplification of electromagnetic ion cyclotron waves along a geomagnetic field line in the multicomponent magnetosphere, assuming that the waves propagate parallel to the background magnetic field. We find it is possible for the ring‐current protons (energy ∼10–100 keV), which supply the free energy to stimulate the waves, to resonate with the waves not only in the equatorial region but also off the equator. An instability, caused by a thermal anisotropy, may occur in separated regions on and/or off the equator. The positions of the source regions along the wave path depend on the concentration of cold heavy ion species. The significant off‐equator source regions may be located at geomagnetic latitudes where the waves, with frequencies greater than the He+ gyrofrequency on the equator, are in a local He+ pass band.

The existence in the Earth's magnetotail of magnetic field and plasma density inhomogeneities can influence the propagation of electromagnetic waves in the lobe and plasma sheet. This is important in understanding the origin of magnetic noise bursts that are observed near the neutral sheet since the waves may not necessarily be generated locally but can be excited in other regions of the tail and propagate towards the central plasma sheet due to the presence of the global inhomogeneities. In this paper the generation and propagation of low‐frequency whistler waves excited by ion beams in the plasma sheet boundary layer is examined. The trajectories of waves that are generated inside the plasma sheet boundary layer are followed using standard ray tracing techniques assuming a Harris‐type neutral sheet magnetic field profile and with the density chosen such that the total pressure remains constant. The wave energy is calculated along the wave path taking into account growth due to the ion beam while the wave is in the plasma sheet boundary layer, and damping due to resonant interactions with the background plasma. Results show that the electromagnetic waves are guided towards the central plasma sheet by the plasma gradients but are damped out before reaching the neutral plane itself due to Cerenkov resonance with the hot central plasma sheet background ions. The amplitudes and final positions of the waves depend on the temperature of the background plasma, the ion beam drift speed, and the ion beam thermal speed.

In order to achieve a ultra-wideband operating characteristics. A low profile dual-band absorbing structure is proposed, the two-dimensional periodic array double ring printed on a dielectric substrate, and insert the chip resistors in four symmetrical positions on the circumference of the ring. The RCS of the two-dimensional array of finite element simulation, the influence of the various parameters of the structure of the electromagnetic wave absorption characteristics of the final results show that the new dual-band absorbing structure can be a metal reflector of RCS reduced. A 4×4 array is simulated, and the result indicates a excellent absorber characteristic to vertical incident electromagnetic wave. The relative bandwidth with return loss below −10dB at 2.4GHz and 5GHz are 10% and 12% respectively. The frequency selective surfaces can be used in aircraft stealth.

High-speed digital system with an increased data transmission rate is facing with serious signal integrity and electromagnetic compatibility problems. To reduce crosstalk and electromagnetic radiation, the components of PCB are placed on the top layer, while the routing of differential transmission lines is on the inner layer. Therefore, Vias must be used to connect components and the inner layer. Vias cause impedance discontinuity during the signal transition and significantly affect signal integrity in a high-speed system. When the signal passes through the vias, reflection may occur due to impedance mismatch. It's necessary to model and optimize the differential vias structure. The traditional optimizing method is realized by adjusting the vias' radius, the distance between differential vias and the anti-pad's radius to reduce impedance mismatch. This paper proposes new optimization methods of vias structure, which has good performance in GHz digital system. In this paper, Ansys HFSS is used to simulate the three-dimensional electromagnetic model of differential vias on a 24-layer PCB and analyze the S parameters (return loss and insert loss). Several key factors affecting the performance of differential vias are analyzed, including stub, non-functional pads and ground vias. Simulation results show that the stub will make the signal resonate and shortening the stub can eliminate the resonance gradually. Removing non-functional pads and adding additional ground vias can help improve the high frequency performance of the system.

The paper presents a non-invasive wireless power transfer technique that facilitates horizontal propagation of electromagnetic (EM) waves within the tissue layer of the human body. The horizontal propagation is achieved by using a modified aperture open-ended circular waveguide as the radio front-end and a wave launcher for impinging the EM wave at a desired angle. The EM wave, then with a dominant horizontal component, takes advantage of the sub-dermal fat channel, a parallel plate-like channel formed by the sandwiched low dielectric fat layer between the high dielectric skin and muscle layer. This horizontally propagating wave can be utilized to power multiple implants from a single external source for overcoming the challenges associated with transmitter-receiver alignment in medical implants. The wave launcher is designed for an operating frequency of 2.4 GHz, which is in compliance with the ISM band, and attributed to the optimal frequency for through-body power transfer. This paper further contains an elaborate discussion on the design of the wave launcher including the SMA to wave launcher transition and the results of its numerical study. The design is then validated based on the return loss and electric field intensity in the multilayer heterogeneous medium replicating the human tissues.

From the study of the relationship between the periodic structure and electromagnetic characteristics of stealth materials, we studied the changes in the rotational rotation angle of the polarization plane of the electromagnetic waves, and proposed a hardware control circuit and software based on the circular polarization propagation method for detecting different paths of satellite electromagnetic waves in the ionosphere. The radio design can produce relatively narrow bandwidth and strong multi-path reflection interference caused by Faraday rotation effects. The simulation results show it can effectively increase the stealing performance of stealth aircraft, thus achieving the purpose of stealth

The research of transformation electromagnetics uses spatial coordinate transformation method to transform Maxwell’s equations for the propagations of electromagnetic waves in space, thereby achieving the goal of designing the path of electromagnetic waves, which eventually leads to a more complex tensor design of its constitutive parameters of metamaterials. This demand for artificial design of material parameters has been combined with the rapid development of micro-scale, molecular-scale, and atomic-scale experimental engineering techniques in recent years, enabling metamaterials to be developed, fabricated, and applied in various frontier fields. In this paper, the metamaterial electromagnetic wave concentrator used to reduce the antenna size is mainly discussed and detailed simulations and researches on the electromagnetic lossy conditions of the metamaterial parameters are given, which can better verify the electromagnetic scattering performance under actual engineering conditions. Solutions and quantitative simulations for the attenuation characteristics are also provided, which can deepen the research on the engineering performance of the metamaterial electromagnetic transformation devices.

Ultra-light MXene aerogel/wood-derived porous carbon composites with wall-like “mortar/brick” structures for electromagnetic interference shielding

The rectenna as a device, is critical for achieving long-distance wireless power transfer. The centrality of this study is focused on adding to the collective knowledge of the subject matter, by providing a new perspective in terms of an alternative design for the antenna component of the rectenna. Essentially, this study features a novel “3-point star” design which was simulated in comparison with the conventional square microstrip patch antenna design. Both designs (i.e., operating at the Wi-Fi band 2.4 GHz), were assessed in terms of simulated performance parameters: gain, directivity, return loss, radiation pattern, and efficiency. From the simulation results, the proposed “3-point star” design, though slightly less efficient exhibited improved performance over the conventional square patch alternative, in terms of gain, directivity, and return loss. For the rectifying component, a greinacher voltage-doubler (with two HSMS2820 diodes), was designed separately and simulated over a range of input power levels (10dBm—34dBm), for 220-Ω, 380-Ω and 810-Ω load resistances, respectively. A maximum conversion efficiency of 88.02% was achieved at 28dBm for an 810 Ω load resistance. All design simulations were executed using Advanced Design System (ADS) software.

A miniaturized dual-band folded reflect/transmit array antenna is proposed in this article. The proposed antenna consisting of lower band folded reflectarray (FRA) and upper band transmitarray (FTA). A unit cell of FRA, with a period of 9 mm (0.33λ at 11 GHz), is designed with a cross shape featuring loaded arcs and four mirror-symmetric L-shaped structures. Meanwhile, the conversion of y-polarized waves incident into x-polarized waves at dual-band is enabled by this unit cell structure. In addition, the unit cell of FTA, with a period of 7 mm (0.39λ at 17 GHz), consists of a top-layer polarizing grid, a middle-layer diagonal Jerusalem cross, and a bottom layer containing two polarizing grids and dipoles. Moreover, the conversion of x-polarized waves into y-polarized waves is enabled only at the upper frequency band by the unit cell of FTA. Phase compensation is performed separately for the phases of the lower band and upper band in both the FRA and FTA. The units of FRA and FTA are combined to form an array, with the 3 dB gain bandwidths covering 10.8-11.8 GHz and 16.5-18.1 GHz, providing relative bandwidths of 8.8% and 10.4%, respectively. The peak gain reach 20.6 and 24.3 dBi, while the maximum aperture efficiency is 19.6%. This proposed antenna features low cost and miniaturization.

Magnetic, dielectric and microwave absorption properties of rare earth doped Ni–Co and Ni–Co–Zn spinel ferrites

The traditional way to measure an electric field electrically disturbs the original field, so that can cause a number of measuring problems. Using a Pockels' crystal to measure an electric field has several advantages over electrical methods, such as interference from electromagnetic radiation, high sensitivity and wide frequency bandwidth. This paper presents a kind of new optical method for measuring electric voltage, current and power, and this new method makes the Sensing Technology on Pockels effect and optical Technology together. The study shows that this kind of method can be used to measure the electric voltage, current and power when the voltage is high and/or the current is large. And a comparison is made between transverse Pockels effect and longitudinal Pockels effect. Electric-optic effect voltage measurement system is designed based on longitudinal Pockels high-voltage measurement methods odotThese methods can applying to high-voltage levels up to 400 kV in a wide bandwidth between dc to30 MHz is developed. In addition, an excellent agreement is observed between the measured and predicted values.