Prediction in the transition region between lit and shadowed regions is important for maintaining stable mobile communication for the beyond 5th generation. In this paper, as the difference between the reflection and diffraction from a dielectric circular cylinder and an absorber screen, respectively, a novel additional term is derived by a uniform theory of diffraction (UTD) in the lit side of the transition region. The proposed model is validated by the UTD and exact solutions of a dielectric circular cylinder. Through the proposal, we can separate the contribution of the shadowed Fresnel zone (FZ) number and boundary conditions (i.e., the surface impedance and the polarization) to the total field. The frequency characteristics of the shadowed FZ and boundary conditions are theoretically analyzed. The analyzed results show that the contributions of the boundary conditions are weaker than the shadowed FZ in the lit region at a high frequency.

A study is made of the guiding properties of a nerve fiber consisting of myelinated axons as applied to electromagnetic waves in the optical and infrared ranges. Based on rigorous expressions for the electromagnetic field in the presence of a nerve fiber, the dispersion properties and field structures of eigenmodes guided by the fiber are analyzed for different values of the dielectric permittivity of myelin. It is shown that such a complex waveguide of natural origin can support the propagation of weakly attenuated eigenmodes in the considered ranges. It is shown that the dispersion properties and field structures of the modes of the nerve fiber can differ significantly from those of a single axon.

Directed energy weapons (DEWs) have been identified as valuable assets in future land and joint combat. High-power radio frequency (HPRF) is a form of DEW which can neutralise robotic systems by discharging electromagnetic (EM) radiation over a region to couple system electronics. Its widespread effect enables the simultaneous disruption of groups of electronic systems, such as swarms of unmanned aerial systems (UASs). Since EM radiation is a distance-based effect, the arrangement of defensive HPRF systems with respect to their target is critical to understanding their utility and viability. Consequently, a mathematical model to assess the effectiveness of HPRF DEW positioned at a given location is formulated. Towards this, a combat scenario specialised to land operations is defined. The assumptions required to formulate the scenario geometrically and mathematically are also outlined. Provided with the position of an effector, it is then possible to quantify the vulnerability of a UAS swarm in terms of a disruption probability. This accounts for uncertainty stemming from UAS and swarm behaviour and assumes that UASs are independent and identically distributed. The model also draws upon work previously conducted at Defence Science Technology Group (DSTG) which derived an HPRF disruption probability function. An optimisation of the disruption probability is undertaken in terms of the position of a single narrowband HPRF effector. Under a hypothesised set of HPRF and threat parameters, maximal swarm defeat probabilities are examined in different swarm deployment regions and HPRF beam widths. This led to the discovery of various tradeoffs between aforementioned features. In particular, under a fixed beam width, proximity to the swam provided an increased defeat probability but reduced the beam's coverage of the swarm. Hence, numerous UASs might not be affected by EM radiation throughout the engagement, reflected in a reduction to the swarm defeat probability.

Planar and conformal log periodic dipole array (LPDA) antennas are proposed in this paper with circular patch and hexagonal patch top loadings for multiband applications. Due to these top loadings, the size of the antennas is reduced, and the total dimensions of the two antennas are 44 mm x 40 mm. These antennas are fabricated on polyimide material with a dielectric constant of 3.3 and thickness of 0.1 mm. These two antennas resonate at 3.5 GHz, 5.7 GHz, 7.5 GHz and 9.3 GHz frequencies in both planar and conformal modes. The antenna characteristics of the proposed antenna models such as reflection coefficient, VSWR, radiation pattern, and gain are analyzed, and the measured results are in good agreement with simulation ones.

This work describes the design and analysis of a four-element wideband circularly polarized (CP) Multiple-Input-Multiple-Output (MIMO) antenna for mid-band 5G utilizations. The proposed MIMO antenna miniaturization is obtained by the implementation of composite right/left-handed (CRLH) transmission line (TL) and loading of octagonal shaped slotted rings inside the antenna ground plane. Further, the circular polarization radiation is obtained due to the sequence arrangement of two CRLH-TL based unit cells of opposite branches, inside a conventional square patch. The intended MIMO antenna encompasses two layers, the layer-1 consists of a four-element CRLH-TL based circularly polarized MIMO antenna placed in side-by-side configuration. The layer-2 consists of 3×3 square-shaped metasurface on one side and an octagonal slotted ring on another side. The combination of two layer results in wider bandwidths of 68.84% (2.21-4.53) and 3 dB axial ratio (AR) bandwidth of 30.4% (3.1-4.21 GHz). Furthermore, the antenna has better than 10 dB isolation, a maximum gain of 7.2 dBi at 4.04 GHz, radiation efficiency of more than 65%, and lower envelope correlation coefficient (ECC) values across the whole operating band. Diversity Gain (DG) values are high and near to 10 dB. Total Active Reflection Coefficient (TARC) and Channel Capacity Loss (CCL) values are also very much acceptable. As a result, the suggested four-element MIMO antenna is appropriate for midband 5G utilizations.

This paper presents a new simplified procedure to design a fourth-order coupled resonator filter. This procedure does not require the calculation of complicated Eigenvalues to develop the required coupling matrix. It starts with studying the effects of different coupling mechanisms on the performance of the overall filter structure. Then, these coupling mechanisms are combined to obtain the design of the required filter. This procedure may be more suitable for machine learning procedure to design coupled-resonator filters. The proposed method is used to design a substrate integrated waveguide (SIW) bandpass filter for sub-six GHz 5G applications. The designed SIW bandpass filter operates in the frequency range from 3.7 GHz to 3.98 GHz which covers the New C-band 5G network with a fractional bandwidth (FBW) of 28% and is centered at 3.84 GHz. This filter is fabricated and measured for verification.

This paper presents the design of dual-band spatial filter for shielding S band and X band wireless signals. The proposed Frequency Selective Surface (FSS) geometry consisting of a square loop convoluted with four strips positioned along the conducting loop. The FSS is aimed to reject WLAN/S-band (2.64 GHz) and X-band (8.3 GHz) wireless signals. The proposed FSS is tested for its angular stability by considering the wave incidence at various angles between 0˚ and 60˚. It is also tested for its polarization insensitive feature via TE mode and TM mode. The prototype FSS is printed on an FR-4 substrate with 1.6 mm thickness and the unit cell footprint of 14.8 mm and tested in an anechoic chamber. The working principle is explained through surface current distribution and the equivalent circuit model of the FSS. Measured results have better similarity with the simulated results.

A multiband electromagnetic band gap (EBG) structure is designed and implemented with a multiband MIMO antenna for mutual coupling reduction. An area of 16 × 16 mm² on a low cost FR4 substrate is used for the proposed EBG design. The designed E-coupled slotted U-shape MIMO antenna resonates at 5.7 GHz, 7.5 GHz and 10 GHz frequencies. Edge to edge separation between the two antennas is kept as 6 mm. EBG structure is placed in the ground plane between two antennas that enable us to keep separation of antennas less than the size of the EBG. Mutual coupling gets reduced by 6.6 dB for 5.7 GHz, 4 dB for 7.5 GHz and 6.95 dB for 10 GHz. Simulated radiation properties of MIMO antenna are verified by measured results, and surface current distribution of MIMO antenna surface also verifies the mutual coupling reduction. Envelope correlation coefficient < 0.01 and channel capacity loss < 0.2 are achieved at resonating frequencies.

The advantage of the canonical filter theory approach to design inductive power transfer (IPT) systems is that values for the coupled resonator elements are readily calculated from scaled canonical filter prototypes with specific frequency response characteristics. For example, Butterworth bandpass filter prototypes can be used to synthesize resonant-coupled IPT systems with critically-coupled frequency response characteristics. In this work, we analyze two canonical filter prototype structures: one prototype has series matching elements at the ports, and the other prototype has shunt matching elements at the ports. Equations are provided to transform the networks into coupled resonator structures that implement IPT links with a transmitter, receiver, and multiple repeater coils. The filter methodology for IPT link synthesis also provides an easy framework to evaluate design trade-offs. An example of comparing resonator inductor sizes for both the series and shunt matching topologies is shown for IPT links operating in ISM frequency bands of 6.78 MHz, 13.56 MHz, 27.12 MHz, and 40.68 MHz. Experimental results are shown for four different IPT examples that were designed using filter synthesis methods.

In this study, a compact, reconfigurable, and high-efficiency Long Range (LoRa) patch antenna, which is novel, is presented for Internet of Things (IoT) applications. The antenna is designed to operate at the three major frequencies used for LoRa communication, namely 915 MHz, 868 MHz, and 433 MHz, which are widely employed for global LoRa connectivity. The compact size and impedance matching of the antenna are achieved through the use of meandered radiating patches, a partial ground plane, and a ground plane stub. The antenna is prototyped on a commercially available and cost-effective FR-4 material and measures 80 mm x 50 mm x 1.6 mm (0.12λ x 0.07λ at the lowest resonant frequency), which is smaller than the size of a standard credit card. The antenna utilizes three RF PIN diodes (SW1, SW2, and SW3) for frequency reconfiguration, which are characterized by low insertion loss and fast switching time. The RLC equivalent circuit of the antenna was validated through simulations and measurements, yielding the peak gain and radiation efficiency of 2.1 dBi and >90%, respectively. These results prove that the antenna is a promising solution for LoRa IoT applications in terms of size, cost, and performance, filling a gap in the existing literature of LoRa MPAs that are typically large, non-reconfigurable, low-gain, and single-band.

Light is widely used in life science in both controlling and observing biological processes, yet a long-standing challenge of using light inside the tissue lies in the limited penetration depth of visible light. In the past decade, many in vivo light delivery methods using photonics and materials science tools have been developed, with recent demonstrations of non-invasive, deep-tissue light sources based on systemically delivered luminescent nanomaterials. In this perspective, we provide an overview for the principles of intravital nanoscopic light sources and discuss their advantages over existing methods for in vivo light delivery. We then highlight their recent applications in optogenetics neuromodulation and fluorescent imaging in live animals. We also present an outlook section about the feasibility of combining these non-invasive light sources with other modalities to expand the utilities of light in biology.

In this paper, a 24-element microstrip antenna array with three-dimensional near-field pattern shaping capability for microwave hyperthermia is presented. The antenna array operating at 2.45 GHz is designed based on the weighted constrained method of the maximum power transmission efficiency (WCMMPTE). By setting proper constraints for the electric field distribution of several selected points within the target area, the three-dimensional (3D) shape of the electric field can be characterized, meanwhile ensuring that the power is maximally concentrated in this area. Moreover, the shape, size, and spatial location of the three-dimensional area are all adjustable according to the selection of those specific points, making the array quickly adaptable for different actual requirements. The electric field distribution of the preset 3D shape can be focused at center or off-center with optimized excitations fed into the array. The measured electric field distribution shows that the transmitting array antenna is able to achieve a preset 3D shape of the electric field distribution as well as a preset offset position in the desired direction, agreeing very well with the simulations.

This research presents the design of a Chebyshev linear antenna array (CLA) integrated with the dielectric lens. In comparison to a uniform amplitude distribution (UAD), a Chebyshev amplitude distribution (CAD) is used to achieve a low side lobe level (SLL) characteristic and increase the directivity of the antenna array. The proposed CLA is optimized to operate at a high fifth generation (5G) frequency. The proposed CLA achieves a -10 dB wide bandwidth from 25.8 GHz to 42.4 GHz. Dielectric lenses can be employed to modify the phase and amplitude of the antenna array, which increases the realized gain and leads to stable radiation over the operational bandwidth. The main purposes of the dielectric lens are to improve the realized gain, enhance efficiency, and result in stable radiation pattern properties. Also, the research presents a study of two types of dielectric lenses with different shapes and their effects on the efficiency and the realized gain of the antenna. The substrate of the dielectric lens is epoxy resin, which has a relative permittivity (ε_r) of 2.716. The proposed CLA integrated with the proposed Type 2 dielectric lens has a realized gain of 15.2 dB and 11.94 dB at the dual-bands 28 GHz and 38 GHz, respectively. All the suggested designs are simulated using CSTMWS2020 and HFSS. However, to verify the obtained results, the proposed CLA is fabricated using a photolithography process technique, and the proposed Type 2 dielectric lens is fabricated using a 3D printing technique.

An elliptical shape multi-band microstrip patch antenna with narrow semicircle cuts and bulges on two horizontal ends is proposed for Global Positioning System (GPS), Indian Regional Navigation Satellite System (IRNSS), Sub-6 GHz 5G and Wireless Local-Area Network (WLAN) wireless communication applications. The proposed antenna operates at 1.56 GHz, 2.49 GHz, 3.5 GHz, and 5.24 GHz for desired applications, respectively. The proposed antenna, fed by coaxial feeding mounted on Rogers AD255C substrate, has optimized physical dimensions of 80×80×3.175 mm³. The semicircle cuts and bulges on horizontal ends on the elliptical element contribute to exciting higher-order modes and affect the current distribution at the resonant frequencies resulting in producing multi-band operations. The antenna is fabricated and tested. The measured return loss characteristic (S₁₁) below -10 dB is -14.58 dB, -18.80 dB, -22.25 dB, & -27.03 dB, with the radiation efficiency of 58.7%, 94.8%, 93.2%, & 84.9% and peak gain of 3.49 dBi, 6.49 dBi, 4.93 dBi & 4.36 dBi for desired application band, respectively. The proposed antenna also offers impedance bandwidths of 40 MHz (1.55-1.59 GHz), 90 MHz (2.43-2.52 GHz), 100 MHz (3.44-3.54 GHz) & 90 MHz (5.23-5.32 GHz) at resonant frequencies and relatively stable radiation patterns. Simulated and measured results for the proposed antenna exhibit good agreement. The proposed multi-band antenna offers a simple design and improved performance.

This article presents the performance of a hexagonal split-ring resonator (H-SRR) antenna in the 2.4/5.2 GHz bands and evaluation of channel capacity for single-input multiple-output (SIMO) and multiple-input single-output (MISO) systems. The proposed antenna consists of two hexagonal-shaped split-ring resonators for dual-band operation with higher gain and metallic loadings between the rings to achieve a wide impedance bandwidth. Impedance modeling of the proposed antennas confirms the role of conductance and inductance of metallic loading for enhancing the antenna characteristics, and thus, the fabricated H-SRR antenna achieves dual-band features with improved impedance bandwidth of 50%/76% and a gain of 2.32/2.57 dB at 2.4/5.2 GHz frequency bands. The performance of the hexagonal SRR antenna is then investigated for space diversity applications in the 1×3 SIMO and 3×1 MISO systems with circular SRR antennas. In linear and spherical arrangements of the antennas, the channel capacity is found in the range of 2.7 to 4.8 Mbps at the 2.4/5.2 GHz bands, which also confirms its dependency on the number of antennas as well as on the placement of antennas.

The paper addresses a bioinspired printed antenna in the shape of a `Lotus' which is further loaded with a new type of Frequency Selective Surface (FSS) structure with unit cell dimension as 0.16λ₀×0.16λ₀×0.033λ₀, where λ₀ is the lowest operating wavelength. The two dissimilar layers of FSS, which are separated by an air gap of about 3.2 mm, have been placed below the antenna. The combined structure operates over 3.8 GHz to 14.4 GHz (116.5% measured) with peak realized gain of 7.5 dBi. The introduction of the FSS layer provides gain enhancement of about 5.9 dBi. The standalone FSS geometry provides a wide transmission bandwidth from 5.5 to 12.5 GHz along with good angular stability of about 50º. The Gielissuper formula has been used to develop the petal of the lotus shaped antenna. The time domain analysis of the lotus shaped antenna has also been provided. The proposed structure can be used as an electromagnetic sensor for wide band applications over C, X and partially Ku bands.

A novel subarray layout method is proposed for the problems of high power dispersion and high complexity of the existing layout methods of receiving rectifier antenna arrays. By the traditional RF synthesis and DC synthesis array layout, the number of units used is high, and the received power dispersion is high. Therefore, this paper proposes a uniform non-overlapping triangular subarray partition layout, and the layout takes three discrete parameters of subarray type, subarray position, subarray placement direction as optimization variables. The minimum dispersion of the received power of the subarray is used as the optimization objective to establish the optimization model. We adopt the Taboo Search (TS) algorithm to achieve the global optimum by setting up a taboo table for global neighborhood search and homogenize the received microwave power value from each subarray. The result shows a lower coefficient of variation (CV) with fewer subarrays and a globally symmetric subarray layout, which reduces the engineering complexity and cost of the subsequent rectification circuit, as well as a lower dimensional span between different subarray types in this novel subarray layout model. We conducted a series of numerical simulations to prove that the method can meet the requirement of minimum power dispersion while ensuring that the total reception efficiency will not be greatly reduced, which verifies the effectiveness of this receiving subarray layout method.

This paper presents a terahertz high gain beam steering transmitarray antenna (BSTA) working at 340 GHz. Substrateless double hexagon ring slots unit-cells which present low loss characteristics at THz band are used to constitute the layout of THz BSTA. To improve the beam steering performance, bifocal technique is used to design the layout of BSTA. Because the fabrication risk of the THz BSTA prototype increases a lot as the aperture dimension is enlarged, four inch silicon wafer is chosen after weighting the risk and gain of the BSTA. Micromachining process is used to fabricate the large aperture THz BSTA to ensure the machining accuracy of the unit-cells. The measured results of the prototype show that the THz BSTA could realize -15°~15° range beam scanning with gain > 38.3 dB, scanning loss < 1.2 dB and side lobe level < -17.8 dB, by moving the feed along the focal plane of the BSTA.

An exhaustive numerical analysis is presented on the effects of defect layers and electric and magnetic loss factors on the transmission spectrum of one-dimensional metamaterial photonic crystal. The proposed structure is a symmetrical multilayer configuration consisting of alternating layers of lossy metamaterial and double-positive material, with a defective region in the middle. The study shows that one or more defect transmission modes are generated in photonic band gaps. The optical properties have been numerically analyzed and simulated using the transfer matrix method. Parameters, such as permittivity, thickness and number of the defect layers, influence the band gap width and the tunability of the defect peak frequency. The effects of the electric and magnetic loss factors (or damping frequencies) of the metamaterial on the intensity and on the quality factor of the defect modes are also well observed. The analysis is validated by comparing the results to some available in the literature, and the proposed structure can be exploited in the design of narrowband filters in the microwave domain.

Since wireless technology has been developed so quickly, there is a surge in interest in multi-band reconfigurable antennas as devices and satellites continue to advance in the direction of downsizing. Due to physical limitations, current and future wireless technologies as well as the cutting-edge compact satellites need antenna systems that are dependable, effective, and have a large bandwidth. The fifth generation of mobile communication technology promises to deliver fast data rates, low latency, and exceptional spectrum efficiency. One of the most crucial factors that makes this technology possible is the way in which satellite technology is integrated with terrestrial communication systems. Therefore, it is crucially important to develop next-generation antennas that can meet the functional requirements for 5G and CubeSat applications. Additionally, the antenna components need to be small and low-profile for Advanced Driver-Assistance Systems (ADAS) and Vehicle-to-Everything (V2X) to function properly. Reconfigurable antennas can offer a wide range of configurations in terms of operating frequency, radiation pattern, and polarization. This paper aims to investigate pixel antenna arrays for wireless communication and Internet of Things (IoT) systems. Design, analysis, and comparison have been done on both the traditional and proposed pixel design configurations. The proposed pixel patch design area reduction is about 75%, and the full design area reduction is about 90%, compared to conventional patches. The pixel design parameters of these antennas are carefully examined to increase their gain, radiation pattern, and efficiency. For a variety of applications, increased gain and various radiation pattern configurations may be advantageous. As a result, increasing the coverage of 5G, 6G, and small satellites requires antennas with a small size, higher gain, and better radiation patterns.