This article reports a multilayer implantable biosensor for a continuous glucose monitoring system, tested on rats to determine the relationship between intravenous glucose level and resonance frequency of implant antenna sensor. An implantable antenna sensor with the volume 330.9 mm³ is tested in three rats as an animal model. This antenna biosensor operates in the Medical Implant Communication Service frequency band (402-405 MHz) with the simulated and measured maximum gains of -13.33 and -21.1 dB, respectively. The specific absorption rate obtained is within the standard limits. An oral glucose tolerance test is proposed to obtain the variation in blood glucose level in the animal's body during measurement. The resonance frequency shift and the corresponding blood glucose level are observed at a regular interval of 30 minutes. A frequency shift of 4.94 kHz per mg/dL is observed. Also, the results related to the reflection coefficient and the factors affecting sensor performance are discussed. The biosensor performance is validated using the proposed simple linear regression model.

An electrically small ultra-wideband (UWB) antenna to cater to the need for UWB communication suitable for today's small gadgets is presented. The antenna is realized on a substrate of relative dielectric permittivity 4.4, loss tangent 0.02 and height 1.6 mm. The overall dimension of the antenna is 21 mm×16 mm×1.6 mm (0.217λ_min×0.165λ_min×0.0165λ_min), where λ_min is the wavelength corresponding to the antenna's lowest operating frequency in free-space 3.1 GHz). The small `k<sub>min</sub>a' value of 0.856 of the antenna, where k<sub>min</sub> is the wavenumber corresponding to λ<sub>min</sub>, and `a' is the radius of the sphere that can fully enclose the antenna, is electrically small. The antenna operates at the FCC recommended UWB frequency range from 3.1 GHz to 10.6 GHz with a reasonably good 2:1 voltage standing wave ratio (VSWR) impedance bandwidth. A prototype of the proposed antenna is fabricated, and different radiation characteristics of the antenna in the frequency and time domain are measured and validated by simulation. The high pulse fidelity for different antenna orientations and very small group delay in the operating frequency band exhibit insignificant pulse distortion. The equivalent isotropically radiated power (EIRP) of the antenna satisfies the FCC mask in the entire UWB. The maximum gain and efficiency achieved within the UWB are 3.95 dBi and 93% respectively. Radiation characteristics of the antenna in the UWB are studied in an anechoic chamber using Agilent PNA E 8362B.

This paper presents a novel variable leakage flux flux-intensifying motor (VLF-FIM) to improve flux-weakening ability. The innovation lies in the variable leakage flux property and the characteristic of L_d>L_q. The two characteristics can be achieved by the adoption of magnetic barriers and magnetic bridges. Consequently, the flux-weakening ability is enhanced. Then, the topology structure and operation principle of the proposed machine are introduced. Based on the two-dimensional finite element method (2DFEM), the electromagnetic performances of the proposed motor are analyzed and compared with the conventional interior permanent magnet motor (CIPMM) in detail. The performances mainly include torque, flux-weakening ability, constant power speed range (CPSR), irreversible demagnetization risk of the PM, structural strength, etc. Finally, the results show that the proposed motor has some advantages, such as good flux-weakening ability, a wide constant power range, and a large high-efficiency area. In addition, it verifies the effectiveness of the proposed method in improving the flux-weakening ability of the motor.

A multi-stack anisotropic cylindrical dielectric resonator antenna with high gain and wide bandwidth is reported. This antenna is designed with three different stacks, and each stack consists of a multilayer dielectric structure to emulate uniaxial anisotropy. Multi-stack, multilayer structure is responsible for producing wide bandwidth and high gain. In addition, the antenna is surrounded by cylindrical metallic cavity to increase directivity in broadside direction. Similar simulated and measured results indicate a wide impedance bandwidth of 37% along with a maximum gain 9.25 dB.

Broadband variations of a proximity fed circular microstrip antenna gap-coupled with narrow annular sectoral patches are proposed. The gap-coupling of pairs of parasitic annular sectors along the x- and y-axes of the fed patch tunes the spacing in between the fundamental modes on the respective patches that yields wider bandwidth. A maximum bandwidth of 728 MHz (55%) offering peak gain of nearly 9 dBi is obtained in the circular patch gap-coupled with four pairs of annular sectors along the x-axis. This bandwidth is around 13% larger than the bandwidth offered by a single circular microstrip antenna. Instead of using multiple sectoral patches, a gap-coupled design of circular patch with a stub loaded annular sectoral patch is presented. The stub tunes TM₀₂ mode frequency with reference to the fundamental modes on the circular and sectoral patches that yields bandwidth of 660 MHz (51%). Resonant length formulation and subsequent design methodology for all the proposed gap coupled configurations are presented, which helps in the re-designing of similar antennas at the given fundamental mode frequency. All the optimum and re-designed antennas are fabricated, and the measured results shows close agreement with the simulations.

In this paper, a novel low-profile and dual-polarized antenna is presented. The antenna is composed of two pairs of rhombic dipoles excited by two orthogonal baluns. The broadband characteristic is achieved by introducing a metal ring under the rhombic dipole, and the radiation pattern beam widths are also improved. Based on the antenna unit, a 2-element antenna array is designed, fabricated, and measured. The relative bandwidth (standing wave less than 1.5) of the antenna is 45.1%, and the port isolation is greater than 27 dB, whereas the cross-polarization level maintains lower than 16 dB in the the frequency band of 2.4-3.8 GHz. The measured results are in good agreement with the simulated ones. This proposed antenna also has low profile characteristics, and the profile height is 20.8 mm, which is less than one quarter of the wavelength (24.2 mm) of the central frequency point (f = 3.1 GHz).

A dual-band Wilkinson power divider covering comprehensive frequency ratios with improved Out-of-Band rejection is proposed with the use of only a resistor. In millimeter-wave range, the established lumped element based design with a wide range of frequency ratio suffers from the nonexistence of tiny required values and the difficulties of integrating them in the proposed designs. To tackle some of the more common millimeter-wave frequency bands challenges, the RLC is substituted in the design by transmission lines and a single resistor. The design parameters and rules are derived theoretically using even/odd mode analysis, and it takes into consideration the Out-of-Band performance. For validation, three different dual-frequency bands are studied (5.8-28 GHz, 20-35 GHz, and 28-35 GHz). The simulated and experimental results exhibit all the advantages of the proposed Wilkinson power divider, succeeding in boosting multi-functional and multi-standard RF and mm-wave front-ends for communication systems.

In this paper, a compact and reconfigurable rectangular substrate integrated waveguide structure dual-mode configuration based dual-band band-pass filter has been presented for 5G communication and milli-meter-waves. The dual-band bandpass filter is realized by utilizing the two pairs of dumbbell-shaped defected ground structure. The dumbbell-shaped defected ground structures etched on both the ground and the top side of the cavity have been used to produce transmission zeros, minimize the circuit size, and enhance the passband characteristics at a particular frequency of operations. In an effort to demonstrate the proposed dual-band substrate integrated waveguide band-pass filter, the proposed configuration has been designed and fabricated at the 28.3 GHz and 38.5 GHz frequency using low-cost PCB technique. The centre frequency of the second pass-band has been easily tuned using the geometrical parameters of the filter to achieve the desired applications in the 5G frequency band. Furthermore, the measured in-band return loss (rejection attenuation) of the two bands is approximately better than 26 dB and 28 dB respectively. The insertion loss of not more than 01 dB for both bands of the filter has been achieved. This dual-band filter operating at the licensed frequencies for the 5G spectrum bands renders this filter appropriate for numerous 5G and millimeter-wave communication applications.

A dual band flexible antenna for applications at 900 and 2450 MHz is proposed in this paper. The antenna offers a compact size of 0.23λ_o × 0.120λ_o × 0.0007λ_o, where λ_o is the wavelength at the lower resonance. The antenna comprises a simple geometrical structure consisting of a W-shaped serpentine structure fed by a microstrip line, while a Defected Ground Structure (DGS) technique was utilized with a partial ground plane to achieve wide operational bandwidth. An additional capacitor was loaded in between the slots to achieve a higher resonance, thus resulting in a compact dual band antenna. Various performance parameters were analyzed, and results were compared with the measured ones. The antenna offers good performance in terms of size, bandwidth, gain, and radiation pattern and thus increases the potential of the proposed antenna for both rigid and flexible devices.

Exceptional points are spectral singularities in non-Hermitian systems at which two or more eigenvalues and their corresponding eigenvectors simultaneously coalesce. Originating from quantum theory, exceptional points have attracted significant attention in optics and photonics because their emergence in systems with nonconservative gain and loss elements can give rise to many counterintuitive phenomena. Metasurfaces - two-dimensional artificial electromagnetic materials structured at the subwavelength scale - can provide a versatile platform for exploring such non-Hermitian phenomena through the addition of dissipation and amplification within their unit cells. These concepts enable a wide range of exotic phenomena, including unidirectional propagation, adiabatic mode conversion, and ultrasensitive measurements, which can be harnessed for technological applications. In this article, we review the recent advances in exceptional-point and non-Hermitian metasurfaces. We introduce the basic theory of exceptional point and non-Hermiticity in metasurfaces, highlight important achievements and applications, and discuss the future opportunities of non-Hermitian metasurfaces from basic science to emerging technologies.

When particle swarm optimization (PSO) is used to identify the parameters of permanent magnet synchronous motor (PMSM), the movement of particles is not selective, which makes the algorithm easy to fall into the local optimum, and the accuracy is poor. The simulated annealing particle swarm optimization (SAPSO) improves the accuracy and evolution speed, but SAPSO has redundant iteration problems. To solve these problems, a motor parameter identification method based on fast backfire double anneal particle swarm optimization (FBDAPSO) is proposed. By reducing the optimization time and quickly tempering and annealing the "misunderstood" difference, the motor adjustable model and fitness function are designed, and the number of iterations is constantly reset to achieve the effect of online identification. Under different working conditions, simulated and experimental results show that the proposed method can quickly and accurately identify the four parameters of the motor's stator, winding resistance, stator winding d-axis inductance, stator winding q-axis inductance and permanent magnet flux linkage at the same time, compared with the traditional method of parameter identification, and it has better accuracy, rapidity, and robustness.

In this letter, a compact dual-band patch antenna based on ball grid array (BGA) packaging for 5G mmWave is proposed. The patch antenna adopts a U-slot and a shorting pin to achieve dual-band operation of 28 GHz and 37 GHz. A single-layer FR4 substrate provides cost-effective features for the massive application. The BGA packaging not only reduces the size but also enables the antenna to be surface-mounted with other components in the same package, which improves the integration. The antenna has been fabricated and measured, and an acceptable agreement was obtained between the simulation and measurement results.

A novel coplanar waveguide (CPW) fed wide slot antenna for broadband circular polarization (CP) operation is proposed in this letter. Utilizing an asymmetrical ground plane and an open slot, broadband axial ratio and good impedance characteristics can be obtained in the middle and low bands. The perturbation patch on the right side of the wide slot excites the upper-band CP mode. By adjusting the upper-part feedline and the wide slot structure, the axial ratio performance can be optimized to a wideband axial ratio bandwidth (ARBW). Compared with wide slot antennas of similar size, the proposed antenna has a simpler structure while achieving a wider ARBW. The proposed antenna has been fabricated and tested. The measured results show that the -10 dB impedance bandwidth (ZBW) is 2.40-7.55 GHz (103.5%); 3-dB ARBW is 2.47-6.2 GHz (86.0%); and the peak gain is about 4 dBic. Right-hand circular polarization (RHCP) radiation pattern is achieved in +z direction. The proposed antenna can be used in WLAN/WiMAX applications and various wireless communication systems which require broadband ZBW and ARBW.

This paper mainly deals with the channel diversity and the effect of spatial consistency parameters for different millimeter wave (mmWave) bands (28, 38 and 73 GHz) according to the channel parameters of the NYUSIM model. Statistical analyses are performed for various spatial consistency scenarios in an urban microcell (UMi) environment. Most of the recent analyses ignored the effect of adjusting the spatial consistency parameters on the 5G mmWave channel characteristics, including path loss (PL), received power, and path loss exponent (PLE). As a result, we have analyzed the effect of each parameter mentioned above for both directional power delay profile (DPDP) and omnidirectional power delay profile (OPDP). Numerical results illustrate how the characteristics of mmWave channels communication can be affected by changing the spatial consistency parameters.

This paper deals with analyzing a novel eddy current damper for an axially magnetized multi-ring permanent magnet thrust bearing (MPMTB). Initially, the bearing is optimized for maximum axial force by selecting three general parameters (air gap, outer diameter of stator, and length) using a generalized optimization procedure. Then, the axial force of an optimized bearing is validated with the mathematical model results. Finally, the novel and conventional eddy current dampers (ECDs) for an optimized MPMTB are analyzed for damping forces and coefficients using three-dimensional (3D) finite element transient analysis in ANSYS. Based on the analysis results, the proposed novel structure could be selected to replace the conventional one for providing damping to MPMTB effectively without affecting the radial air gap between the rotor and stator rings.

This paper proposes two low divergence angle orbital angular momentum (OAM) Fabry-Perot (F-P) antennas with nonuniform superstrates. There are two steps to design the proposed two F-P antennas. First, two primary array antennas (a slot array antenna and a patch array antenna) are designed. Both antennas can generate OAM vortex beams with a mode of -1. Second, two F-P resonator cavity antennas are formed by loading a nonuniform partially reflective surfaces (PRS) superstrates above the two primary antennas in order to increase the antenna gain and reduce the divergence angle. The PRS is designed non-uniform for increasing the aperture efficiency. The measured results indicate that the F-P OAM antennas can obviously improve the performance of primary OAM antennas: (1) for the slot array antenna, the divergence angle reduces from 27° to 18°, and the maximum gain increases from 5.2 dBi to 7.5 dBi; (2) for the patch array antenna, the divergence angle decreases from 30° to 18°, and the peak gain increases from 3.4 dBi to 7.2 dBi.

In this paper, a novel mechanical-flux-weakening interior permanent magnet (MFW-IPM) machine is proposed to improve flux-weakening ability. The key of the proposed machine is that the permanent magnet is rotatable, and a mechanical device is equipped on both sides of the rotor. The mechanical device can regulate the air-gap magnetic field by rotating PM to change the leakage flux and magnetization direction of PM. As a result, the flux-weakening ability is improved. The flux-weakening principle of the MFW-IPM machine is investigated in detail. In addition, a multi-objective optimization method is adopted to improve the performance of the proposed machine. Then, the electromagnetic performances of the original machine and optimized machine are compared by finite element analysis. Finally, both simulation results and experimental tests verify the effectiveness of the flux-weakening enhancement design and optimization method.

The engine of a fighter plane is one of the largest scattering centers of the entire aircraft. One possible way of reducing the radar cross section (RCS) of the engine is to use an S-shaped bending air inlet to avoid direct radar wave illumination and reflection. We evaluate the efficacy of an S-shaped air inlet on RCS reduction by simulating the boresight and ±15˚ bistatic RCS for a digital model of an engine located behind an S-shaped inlet, using a multi-level fast multipole method (MLFMM) code in the S and X bands. The results show that a curved S-type air inlet can reduce the engine boresight bistatic RCS by ~10-12 dBsm at 3 GHz, and ~16 dBsm at 10 GHz when radar wave is incident from boresight, but not to the level required by RF stealth standards. When the radar waves are incident from θ=105˚ φ=90˚ or θ=90˚ φ=345˚, the RCS reduction is less effective, which is the results of the bend direction of the S-type air inlet.

This paper presents a new integro-differential coupling between partial equivalent electrical circuits (PEEC) and finite difference method (FDM) taking into account the magnetization effect. This coupling is intended for thin plates having simultaneously significant conductive and magnetic properties in presence of exciting coils of complex topologies. These cases exist in eddy current nondestructive testing (ECNDT), eddy current separation, induction or levitation melting devices and more other applications. The choice of FDM, is in relation with rectangular surfaces generated by numerical meshes leading to mathematical integrations of magnetic and electrical quantities with independent variables, unlike more complicated forms of surfaces generated by finite element method (FEM) or others. Fully successful analytical expressions have been realized and implemented in overall coupling process. The PEEC method is mainly used to calculate the magnetic field applied to the nodes of the plate from different inclined polygonal coils. The results of magnetic field and eddy current distributions on thin plates are presented, and parts of them are compared with those realized by Flux 3D software.

Due to low power density, it is difficult for a single-band rectenna to harvest enough power for IoT devices like wireless sensors. Thus to supply these consuming devices, harvesting RF energy from multiple frequencies is a solution to enhance the amount of harvested DC power. In this work, we introduce a triple-band rectenna, working at 900 MHz, 1.8 GHz and 2.1 GHz, three readily available bands in the ambience, for energy harvesting application. The proposed rectenna consists of three monoband rectifiers connected to a multi-band receiving antenna via a highly efficient triplexer. The antenna is made by superposing two concentric rings and manipulating their radii to achieve the desirable operating frequencies, with antenna gains of respectively 2.5 dBi, 4.5 dBi, and 4 dBi. The contiguous triplexer is made by connecting open stubs band-reject filters and optimizing their positions, resulting in the triplexing efficiency higher than 75%. The measured RF-DC efficiency under -10 dBm triple-tone input power is 40%.