A low-loss dual-band negative group delay circuit (NGDC) with a flexible design is proposed. The proposed NGDC consists of a transmission line coupled asymmetrically with two step-impedance open-loop resonators. The negative group delay (NGD) times and center frequencies of the lower and upper bands can be tuned independently. To verify the design concept, two dual-band NGDC prototypes I and II are fabricated and measured. The measured NGD times of prototype I are -4.9 ns and -4.8 ns at the center frequencies of 1.949 GHz and 2.054 GHz, respectively. The insertion loss is lower than 2.7 dB and the return loss larger than 11.2 dB in both NGD bands. For prototype II, the NGD times at 1.949 GHz and 2.086 GHz are -4.7 ns and -3.3 ns, respectively. The measured insertion loss is better than 2.4 dB with the return loss larger than 11.9 dB.

A fast solution for electromagnetic (EM) scattering problems over a wide incident angle based on compressed sensing (CS) has been proposed in recent years. Since current expansion coefficients are not known in advance, the parameters of this solution (e.g., the times of measurements, the selection of sparse transforms) for different scattering objects are difficult to determine. In order to solve this problem, this paper presents a prior parameter extraction method based on the principle of on-surface discretized boundary equation (OS-DBE), in which an approximate distribution of current expansion coefficients at any given point of the scatterer is first obtained with low-coverage and low-complexity, and then the prior parameters can be determined by CS tests for the approximate result. The implementation method is elaborated, and its effectiveness is verified by numerical results.

Despite the advancements in the field of glucose monitoring sensors, the development of noninvasive, wearable, continuous and comfortable systems is still a real challenge. New technologies are required for noninvasive, continuous and effective measurements remaining discreet, painless, comfortable to the patient and avoiding additional costs.This article presents a truly noninvasive microwavetomography prototype designed for glucose monitoring. The system is based on an array of dipole antennas placed in a circular configuration.The transmitted field data are collected using a switchmatrix connected to a vector network analyzer. A heterogeneous 3-D arm model and a 3-D electromagnetic solver have been used to model the human arm and to characterize the system. Blood electromagnetic properties are affected by the glucose concentration, a promising correlation between the dielectric properties of blood and glucose level should be investigated. By simulating the antenna array on the arm phantom, the characteristics of the S-Parameters were interesting at the frequencies of interest. The transmission coefficient amplitude decreases as the dielectric constant decreases from 63 to 40, and the conductivity increases from 1.5 S/m to 3.5 S/m. For each value of dielectric properties, a given transmission coefficient value can be clearly identified. Experimental measurements validated the arm phantom and confirmed the relationship between the response of the system and the dielectric properties of blood tissue. The armband sensor is designed as an inexpensive, noninvasive, and light weight device suitable for all patients with a high level of discretion. This work, under optimization for preclinical and clinical testing, demonstrates the proof of concept of an innovative microwave tomography system for noninvasive glucose monitoring. Compared to studies with a similar aim, this research may achieve distinct advances and offers promising hope in the field of noninvasive glucose sensors.

A high-gain wide-band planar antenna with H-Shaped Resonators (HSRs) for Self-Powered wireless systems is proposed in this paper. The proposed antenna consists of four major parts, namely, a grating Vivaldi electrical dipole, a half-ring magnetic dipole, HSRs, and a solar panel reflector. The dipoles are etched from both antenna substrate sides by each half on one side. The HSR structures are etched on a single side of the used substrate to avoid the capacitive coupling effects which cause the radiation efficiency reduction. HSR inclusions are designed and tested numerically to have the desired electromagnetic properties at frequency band of interest. After introducing the HSR inclusions to the antenna structure, the antenna performance is tested numerically and compared to that without HSR inclusions. The fabricated prototype based HSR structure shows an enhanced gain bandwidth product to cover the frequencies from 1.75 GHz up to 7.43 GHz with a gain varying from 9.52 dBi up to 16.71 dBi over the entire frequency range. Finally, an excellent agreement has been achieved between the gathered numerical results and those from the experimental measurements.

The paper is focused on reliable modeling and analysis of the effects connected with the resonant transformation of the field of a plane and density-modulated electron beam flying over the periodic rough boundary of a natural or artificial medium. In the paper such a medium occupies a part of the half-space, limited in thickness. Therefore, the numerous effects appeared due to transverse (in the thickness of the periodic structure) resonances, and the coupling of eigen regimes of two different periodic interfaces also contributes to the anomalies appearing due to excitation of the surface eigen waves of the periodic boundary interface that had been discussed in previous papers of this series.

This paper proposes an improved mathematical formulation of Johnston's approach to measure the radiation efficiency of an antenna, based on the Wheeler Cap (WC) technique. The proposed modifications allow the measurement of the radiation efficiency of small antennas matched to complex loads implemented on Radio Frequency IDentification (RFID) tags. The studied structure is a low-cost, silver-printed, differentially-fed RFID dipole antenna. The antenna is printed on a flexible PET (polyethylene terephthalate) paper that is conformable on various objects. Link budget measurements validate the accuracy of the formulation, which can be applied to any dipole antenna matched to an RFID chip with a complex input impedance.

The Bateman-Whittaker theory, which was developed a century ago, is shown to be a comprehensive basis for deriving a large class of null spatiotemporally localized electromagneticwaves characterized by intriguing vortical structures. In addition, it provides the modeling for studying topological structures dealing with linked and knotted electromagnetic waves.

A novel and compact triple-band two-element Multiple Input Multiple Output (MIMO) antenna array is designed to provide simultaneous communications for uplink and downlink which covers GSM, LTE, and sub-6 base station applications. The proposed MIMO system is a configuration of four triple-band two-element arrays in which two are used for uplink and the other two for downlink. This compact structure with separate antennas for uplink and downlink provides simultaneous communication. For this proposed structure, the parameters like impedance bandwidth, efficiency, gain and cross polarization aspects are presented for all the three specified bands. To achieve good isolation uplink and downlink arrays are placed orthogonal to each other. Further, to enhance the isolation a defected ground is incorporated for the antenna array structure, and isolation strips are provided between uplink and downlink arrays. In addition, for the proposed structure diversity performance with Envelope Correlation Coefficient (ECC) and diversity gains are also calculated. The simulated and measured results are in acceptable correlation.

Parasitic effects in a lumped-element multilayer LC resonator are analyzed with an equivalent circuit. An optimization technique is proposed. With this technique, undesired influences of parasitic effects may be reduced. Meanwhile, some of the parasitic effects may be used for the size-reduction and performance improvement. A lumped-element multilayer LC resonator is used for demonstration. The optimized resonator outperforms the resonator before optimization in both performance and size. A multilayer filter composed of four LC resonators is used for verification. The measurement results agree very well with circuit results. The measured parasitic resonances are higher than the third harmonic frequency. These facts show the effectiveness of the proposed technique.

We present the design, optimization, and analyses of efficient couplers to construct nano-optical transmission systems involving nanowires. The couplers consist of optimized arrangements of nanocubes and are integrated into critical locations, such as nanowire inputs, corners, and junctions, to improve electromagnetic transmission in accordance with design purposes. Optimization and numerical analyses are performed by employing an efficient simulation environment based on a full-wave solver and genetic algorithms. Using the designed couplers, we obtain various configurations that enable efficient transmission and distribution of input powers to multiple outputs. With their favorable properties, the designed couplers and constructed systems can be further used to build larger nanowire networks.

A compact broadband circularly-polarized (CP) patch antenna with a wide 3-dB axial-ratio (AR) beamwidth is proposed for universal ultra-high-frequency (UHF) radio frequency identification (RFID) applications. The proposed antenna consists of four triangular radiation patches and a compact feed network. Each of the radiation patches is grounded by shorting pins for 3-dB AR beamwidth enhancement and patch miniaturization. The feed network having a miniaturized hybrid coupler and two trans-directional couplers is proposed for good circular polarization. Measured results show that the -10-dB impedance bandwidth of the antenna is 18.4% (820-986 MHz); the 2.5-dB AR bandwidth is 32.8% (700-975 MHz); and the gain is 5.12 dBic. The measured 3-dB AR beamwidths for the planes of phi = 0° and phi = 45° are 177° and 190°, respectively. The overall antenna size is 0.408λ₀ × 0.408λ₀ × 0.053λ₀ at 900 MHz.

In this paper, a triangle-shaped Quarter Mode Substrate Integrated Waveguide (QMSIW) cavity back slot antenna is developed using TE₁₁₀, TE₂₂₀, and TE_{310, 130} modes for tri-band operation. The QMSIW is obtained from the quadrant part of a square SIW (Substrate Integrated Waveguide) structure. The electric field distributions of resonant modes are studied for the Full Mode SIW, Half Mode SIW, and Quarter Mode SIW cavities through HFSS simulation tool. The generation of the hybrid mode TE_{310, 130} mode is clearly explained with the simulation tool. A rectangular slot is engraved on top layer of the structure along the perfect electric wall, to radiate the EM (Electro Magnetic) wave towards positive Z-direction. Further, a metallized via has been inserted to bring reflection coefficient below -10 dB at the three resonant modes. The developed antenna achieves resonance at 5.2 GHz, 9.88 GHz, and 10.6 GHz frequencies with peak gains of 9 dB, 6.2 dB, and 7.9 dB, respectively. The antenna is designed on a single layer thin substrate which reduces the fabrication complexity.

Comparative study of some novel wideband Tulip Flower Monopole Antennas (TFMAs) is presented in this paper. To Improve the bandwidth and increase the gain, modification of the shape of the curves and slots in the patch and ground plane was carried out on the seven TFMAs. TFMA-A, TFMA-B, TFMA-C, and TFMA-D have dimensions of 50×50 mm², while TFMA-E, TFMA-F, and TFMA-G have dimensions of 30×70 mm². From the simulation result, TFMA-A operated from 2 GHz to more than 30 GHz with a return loss of 15 dB occupies most of its operating frequency. In the whole frequency work, the peak directivity performance in the order of superiority is obtained for TFMA-G, TFMA-F, TFMA-D, TFMA-E, TFMA-C, TFMA-B, and TFMA-A. The improvement of directivity is reached for TFMA-D of 5.03 if it is compared to TFMA-A at 24 GHz. TFMA-G obtains the peak of directivity of 10.148 dBi at 23 GHz. The impedance bandwidth and directivity of the antenna element change by varying the curvature, the shape, and the position of slot in the radiator and ground plane also the height of the microstrip feeding line and ground plane. The return losses of the TFMA-A and TFMA-E show good agreement between simulation and measurement results.

In this paper we present a simple approach to compute quickly and accurately the global inductance of multilayer circular air coils with a wire of rectangular cross section. The case of the uniform current density distribution in the wire cross section is considered. The approach, implemented under GNU Octave, computes the inductance of the multilayer coil in three steps. First, the self-inductance of each coil turn is computed using the Maxwell's formula. Secondly, each wire section is subdivided into several negligible square or rectangular subsections to form a filiform turn, and then the mutual inductances between the turns are computed using Rosa's formula. The last step sums all obtained self-inductances and mutual inductances to deduce the global inductance of the multilayer coil. To verify the efficiency and accuracy of the proposed approach, the obtained equivalent inductance of each turn is compared to the computed one using finite element method implemented in FEMM open source. Furthermore, the global coil inductance is compared to the measured one. The proposed approach shows a good accuracy with a relative error less than 1% for all considered coils.

We report a reduction in crosstalk between a transmitting antenna and an adjacent receiving antenna due to the use of radiation patterns with different orbital angular momentum (OAM). This crosstalk reduction is based on the orthogonality between different OAM modes. To generate OAM beams, patch array antennas are designed using High frequency simulation software (HFSS). The designed antennas are fabricated and characterized. An experiment is carried out to determine the amount of crosstalk reduction achieved due to the OAM nature of the signals transmitted. The variation of this crosstalk reduction with the distance between the transmitting and receiving antennas is also studied. The results obtained are verified through theoretical analysis using simulations in HFSS. A maximum theoretical crosstalk reduction of 3.6 dB has been obtained, and a crosstalk reduction of 2.6 dB has been realized experimentally. The results may benefit full-duplex communication links.

A compact-size quad-band (28/45/51/56 GHz) microstrip patch antenna is proposed for the Fifth Generation (5G) mobile handsets. The present paper introduces a new method to reduce the size of a 28-GHz rhombic patch antenna so as to properly operate at the higher frequency bands (45/51/56 GHz) without negative effects on the antenna characteristics at 28 GHz. A novel design is introduced for the quad-band patch antenna to include complicated radiation mechanisms required for multiple-band operation. The proposed (single-element) antenna is constructed as primary and secondary patches which are capacitively coupled and designed to realize impedance matching and to produce appropriate radiation patterns in the four frequency bands. Two-port and four-port MIMO antenna systems that employ the quad-band patch antenna are proposed in the present work for the 5G mobile handsets. Numerical and experimental investigations are achieved to assess the performance of both the single-element antenna and the proposed MIMO antenna systems including the return loss at each antenna port and the coupling coefficients between the different ports. It is shown that the simulation results agree with the experimental measurements, and both show good performance. The bandwidths achieved around 28, 45, 51, and 56 GHz are about 0.6, 2.0, 1.8, and 1.3 GHz, respectively. The radiation patterns produced when each port is excited alone are shown to be suitable for spatial diversity scheme with high radiation efficiency. It is shown that the envelope correlation coefficient (ECC) and diversity gain (DG) are perfect over the four frequency bands.

In this paper, 1 × 1 and 2 × 2 Multiple-input Multiple-output (MIMO) antenna is designed for a multiband application. The antenna consists of three concentrated decagon shaped rings which are responsible for obtaining the three resonance frequencies. The proposed antenna has a unique design technique; without using any decoupling structure the antenna attains better isolation performance. First, a two (1 × 1) element MIMO antenna with three different orientations (Orientation-I, II, and III) is studied. Second, a four-element MIMO antenna is designed without any decoupling structure for better performance. The above two antenna designs are fabricated and measured. The dimension of the proposedantenna element is 23.5 mm × 26.5 mm, and it has -10 dB impedance bandwidth over 2.4-2.52 GHz, 3.66-4 GHz, and 4.62-5.54 GHz, which cover various applications such as WLAN (2.4/5.2 GHz), WiMAX (2.5/5.5 GHz), public safety (4.9 GHz), and 5G (3.6-3.8 GHz). The proposed MIMO antenna diversity performances such as isolation, ECC, Directivity Gain, TARC, Channel Capacity Loss (CCL), and Mean Effective Gain (MEG) are studied.

Polariton assisted tunable directionality provides an intrinsic ingredient to various micro/nano integrated optical systems. Their capabilities of light manipulation in mesoscopic structures allow numerous beneficial properties in information processing. The realization of active near-field directionality by tuning the input signal of system bias is more preferable than that by reconfiguring the nanostructures. Recent progresses on the multiple hybrid dipole radiations ensure another methodology in realizing tunable directionality. Here we investigate some exotic near-field phenomena in a 5-layer waveguide consisted of graphene and hexagonal boron nitride (hBN) illuminated by hybrid dipole sources such as a Circular dipole, a Huygens dipole or a Janus dipole. We demonstrate divergent behaviors of hybrid polariton excitations subject to various source types and the tunability of switching between phonon-like polaritons and plasmon-like polaritons. We also show that the flipping of the group velocity of excited hybrid polaritons can be used to flexibly tune the transportation direction away from the dipolar sources. To be specific, when the group velocity of supported polariton flips its sign, the energy flow will shift to the opposite side accordingly. Such phenomena are promising in the design of reconfigurable and multifunctional nanophotonic devices.

A novel high gain two port planar antenna for 5G millimetre-wave and satellite band is presented. The proposed antenna besides working in the millimetre-wave range has an added feature to work for the satellite X-band as well. The antenna has a miniaturised low-cost planar geometry having the dimensions of 1.83λ x 1.83λ x 0.07λ at 27.5 GHz, designed and fabricated on a Rogers RT/duroid substrate of thickness 0.8 mm. The proposed antenna has return loss values of 12.34 dB and 17.94 dB for the two resonant millimetre wave frequencies of 27.24 GHz and 28.88 GHz respectively and 12.66 dB for the satellite band frequency of 8.42 GHz. The antenna attains a peak gain of 10.2 dBi for 28 GHz millimetre wave band and 6.2 dBi for satellite X-band by exploiting an inverse micro-strip Yagi director geometry. The isolation between two ports has been found satisfactory thus making it operate efficiently forthe available Ka and X band capacity of the Wideband Global Satcom system (WGS). The experimental results regarding the fabricated prototype are presented and compared with the simulated results, which are in good agreement. The performance of proposed antenna regarding radiation efficiency, directivity, gain, radiation pattern, and good isolation between the two ports makes the antenna employed as a suitable candidate for satellite communication and especially for 5G millimetre-wave communication.

A compact 30×30 mm² high performance four elements ultra-wide band multi-input multi-output (UWB MIMO) diversity antenna is proposed. The prototype antenna consists of four symmetrical antenna elements which are orthogonally placed on top surface of the substrate with partial slotted ground plane. The isolationamong the antenna elements is improved by placing antenna elements orthogonally without any additional decoupling structure. The various antenna characteristic parameters, i.e. return loss (< -10 dB), isolation parameter (<-22 dB), radiation patterns near omnidirectional, and maximum realized gain 4.8 dB, were measured. The MIMO performances of prototype antenna were also measured in terms of various MIMO diversity parameters and found ECC<0.06, DG>9.98 dB, TARC<-10 dB and MEG<-3 dB throughout the frequency band. This design provides an operational bandwidth from 2.15 to 16.75 GHz which covers the whole UWB spectrum and is suitable for portable devices.