Gap-surface plasmon (GSP) metasurfaces that consist of metallic resonators, a middle dielectric spacer, and a back metallic reflector have become an emerging research area due to their excellent properties, such as ease of fabrication, high efficiency, and unprecedented capabilities of controlling reflected fields. In this concise review, we introduce our efforts in exploring the physical principles and fascinating applications of multifunctional GSP metasurfaces in the optical range. Starting with a typical GSP meta-atom, we present the concept and mechanism of simultaneous and independent phase and polarization control. We then overview some typical applications of GSP metasurfaces, including beam-steering, surface plasmon polariton coupling, metalenses, meta-waveplates, and dynamical metasurfaces. The review is ended with a short perspective on future developments in this area.

In this paper, an optimized circularly polarized (CP) antenna is proposed for operating in the LTE bands 42/43 applications. This CP antenna comprises three sections, the meander-line and L-shaped strip structures modeled on the front side of a Roger 3003 substrate, and on the back side a rotated H-shaped ground plane is printed. In order to further increase the antenna common bandwidth (CBW), that is the voltage standing wave ratio bandwidth (VRBW) and axial ratio bandwidth (ARBW), an offset-fed line on the front side and a shorting pinare used. A feasible solution of the optimized CP antenna with compact size is achieved by applying an optimization design methodology with a fitness function that takes into account the antenna performance parameters, CBW or both the VRBW and ARBW in addition to the realized gain (RG). Two programs are operating in synchronous fashion for finding the optimal geometric antenna parameters, a particle swarm optimization (PSO) for implementing the fitness function in MATLAB and a CST MWS simulator tool for extracting the antenna performance parameters. The optimized antennas without and with shorting pin are obtained with a broadest CBW and feature of CP operation and an acceptable RG across the desired LTE 42 (3.4-3.6 GHz) and LTE 42/43 (3.4-3.8 GHz) band, respectively. The proposed two designed antennas, with and without shorting pin, are fabricated, and the measured results are in good agreement with the simulated ones. From measured results, a -10 dB-S₁₁ impedance bandwidth (IBW) of 220 MHz (3.38-3.60 GHz) and 460 MHz (3.37-3.83 GHz), a 3-dB ARBW of 200 MHz (3.4-3.6 GHz) and 390 MHz (3.42-3.81 GHz) with respective maximum RG of 2.26 and 2.39 dBic are exhibited by the antennas without and with pin, respectively. The obtained 3-dB ARBWs and -10-dB IBWs make the proposed antennas entirely cover the LTE 42 or LTE 42/43 frequency bands.

Aiming at the problem of large torque ripple caused by large tracking error between actual torque and reference torque in commutation region in direct instantaneous torque control (DITC) algorithm of switched reluctance motor (SRM) based on torque sharing function (TSF), a torque compensation method combining TSF-DITC and model predictive control (MPC) is proposed. Sectors are subdivided in the commutation region according to the rotor position. Different voltage states are selected in different sectors to fully compensate for the tracking error between the actual phase torque and the reference torque distributed by TSF, and then the total torque ripple is greatly reduced. At the same time, the algorithm also effectively reduces the candidate voltage states at the current time and reduces the computational burden. The simulation comparison with TSF-DITC shows that the algorithm (TSF-PDITC) has better steady-state and dynamic performance.

A compact and novel quad element MIMO antenna is presented for ultra-wideband (UWB) applications. The proposed orthogonal MIMO antenna comprises four identical elliptical structure-based tree shape microstrip line fed radiating elements. Radiating elements are placed in orthogonal with each other to obtain low mutual coupling and good diversity characteristics among MIMO elements. The proposed MIMO antenna operates from 4.2 GHz-13.2 GHz with an impedance bandwidth (S₁₁ < -10 dB) of 9 GHz. It is investigated at 5.9 GHz DSRC band for vehicular communication applications and X-band for FSS applications. It exhibits superior characteristics with a peak gain of 6.2 dB at 11.7 GHz and radiation efficiency above 80%. To assess diversity performance of the proposed antenna MIMO performance metrics are investigated. Mean effective gain (MEG) < -3 dB, envelope correlation coefficient (ECC) < 0.05, channel capacity loss (CCL) < 0.4 bits/sec/Hz, diversity gain > 9.99, and multiplexing efficiency > -3 dB. Simulation results and experimentally obtained results are in fine agreement.

An efficient and stability-improved finite-difference time-domain (FDTD) method with auxiliary difference equations (ADE) for cold magnetized plasma is developed in this paper. The two equations of Ampere's law and the auxiliary equation for plasma are unified as a single equation at first. Then the leapfrog difference scheme is applied to it and Faraday's law, respectively. By introducing a mid-term computation into the unified equation, the iterative equations of the ADE-FDTD for plasma are derived. Its stability condition remains the same as that of a vacuum which is analyzed and numerically verified. Numerical experiments show that our proposed method is more efficient than those provided by others but with the same accuracy. Finally, the transmission properties of a magnetized plasmonic slab are investigated. The reflection and transmission coefficients of the right-circularly-polarized (RCP) and left-circularly-polarized (LCP) waves are calculated. The results show that our proposed method can be applied to study these plasma-based structures accurately and efficiently.

Fractal and reconfigurable antennas are the need of modern wireless communication systems that operate under dynamic scenarios catering to the diversified needs of modern wireless applications. In this dissemination, a novel multiband Fractal Reconfigurable Antenna (FRA) has been presented and discussed using two RF PIN diodes as switching elements for electronic reconfiguration. It is analyzed using equivalent circuit concept and investigated in terms of various antenna performance parameters. The proposed FRA can operate in various frequency bands resonating at four different frequencies with switchable bandwidth and gain. The highest gain is observed to be about 8.37 dB at 9.68 GHz while the highest bandwidth is about 540 MHz in the X-band. The simulation and measurement results obtained are found to be in agreement. The multiband characteristics of the proposed FRA make it useful for smart wireless communication applications in the S (2-4 GHz), C (4-8 GHz) and X (8-12 GHz) microwave bands.

This paper proposes an efficient method to simulate the micro-Doppler (MD) frequency of a ballistic warhead by considering a real flight scenario in monostatic and bistatic observations. The radar signal is difficult to obtain by changing the observation angle as the conventional electromagnetic software does obtain the reflected signal for a fixed target, so we transformed the pose of the model engaged in micro-motion in a local coordinates, to the pose on the trajectory, by constructing the transformation matrix. Then we obtained the radar signal by using the point scatterer model and the high frequency estimation method, physical optics, and compared the MD results by using the short-time Fourier transform. In simulations for various observation scenarios, MD signatures were successfully obtained, and scattering characteristics were accurately analyzed.

A defected ground structure (DGS) loaded slotted patch antenna is proposed in this article to achieve multiband response with minimization of cross polar radiations in both the radiation planes. Besides, the antenna in this work achieves reduction in cross polar radiation at all its resonating bands with a simple inset feeding mechanism. Loading of identical U-shaped slots in the patch helps the antenna to achieve dual resonance characteristics and also leads to minimize the orthogonal E-field components. Along with the slotted patch, implementation of DGS results in multiple current paths leading to additional resonances in lower frequency range and also suppresses the strong leakage current in the ground plane. Moreover, three identical slots are loaded at the edges of the ground which balance the strong E-field components in opposite direction improving the reflection coefficient at the different resonating bands. The proposed antenna achieves multi-resonance characteristics operated in 2.44-2.56, 5.45-5.52, 6-6.13, 7.43-8.04, and 8.99-9.17 GHz. Minimization of orthogonal E-field components and suppression of leakage current are responsible for obtaining minimum cross polar radiation from the antenna as -39.08 and -41.01 dB in E- and H-planes, respectively.

In this work we demonstrate the extended and generalized methodology for the design of Quad-Furcated Profiled Horns (Q-FPHs). Based on a design case of a 4λ₀×4λ₀ Q-FPH, we extract the Generalized Scattering Matrix (GSM) of the enlarged quad-furcated discontinuity and provide analytical expressions for its multimode feeding. Next, the four feeding and the upper common waveguide sections are optimized accordingly through Mode-Matching (MM). The high aperture efficiency levels delivered by the methodology are verified by full-wave simulations of the optimized design case and compared to the state-of-the-art which is thereby redefined.

The evolution of computing and network technologies which involve thousands of devices that are connected wirelessly to serve variety of applications in Internet-of-Things (IoT) draws significant interest in locating the indoor objects. In our paper, we focus on developing a hybrid source positioning technique with off-the-shelf hardware modules. A rectangular corridor with a multipath environment is considered in our work. For better localization accuracy, the corridor is classified into segments with threshold RSS values. Based on the measurement data segment-wise logarithmic regression models are developed, and the performance in terms of Correlation Coefficient (R2) and Root Mean Square Error (RMSE) is evaluated. For localization, basically trilateration is used. However, to overcome the adverse issues due to the indoor environment such as flip ambiguity, uncertainty in range measurements, circumscribing the circle's scenarios, two circle intersection, dynamic circle contraction, and expansion methods are used. Relevant Pseudocode algorithms are presented. The proposed hybrid method significantly improves the localization accuracy. The standard deviation of errors in x and y directions are about 16.75 cm, 66.24 cm in the first segment and 19.75 cm, 60.16 cm in the second segment. The analysis and results are useful in establishing state of the art IoT and future generation 5G networks.

A target detection method based on polarimetric multi-domain feature fusion is proposed in this paper to improve the detection performance of slow small targets on the sea. Firstly, a complex symmetric matrix was established based on the Pauli scattering vector. On the basis of an analysis on the matrix, the Takagi decomposition method was adopted to extract the normalized polarimetric maximum eigenvalue to characterize the echo signal. Secondly, a real symmetric Hurst exponent matrix was constructed by processing the echo signal of the polarimetric radar, and the normalized polarimetric Hurst exponent was extracted by the eigenvalue decomposition method. Thirdly, the normalized polarimetric Doppler peak height was extracted through the Doppler peak height algorithm. Finally, by fusing multi-domain features, a false alarm controllable detector was constructed through the convex hull algorithm. The results of experimental analysis on the measured datasets indicate that when the parameters are the same, compared with the traditional detection methods based on polarimetric features, the proposed method presents better robustness in the case of short observation time and low signal to clutter rate.

RF and mm wave filterssuffers from a common problem of asymmetries in filters transmission response caused by unwanted field couplings between individual resonators. In this paper, unwanted or spurious couplings between non-adjacent resonators are identified in the filter network from the simulation stage and mitigated to the extent possible. A 4-pole Quasi Elliptic Planar Band Pass Filter is fabricated at 48.5 GHz on a Liquid Crystal Polymer (LCP) substrate. An improvement of 6 dB in side lobe imbalance in filter transmission response is obtained. Effect of spurious coupling on band pass filters transmission response is demonstrated through EM simulation. Commensurate measurement results are presented.

This work is purposed to provide microstrip antennas for a CP-SAR system with low sidelobe, tilted beam, and circular polarization. This antenna is configured for the L-band (1.27 GHz) mounting on an Unmanned Aerial Vehicle (UAV). The proposed microstrip antenna consists of three-square radiating elements, due to the ease in fabrication. Meanwhile, the proximity structure has been adopted in the feeding network. The tilted beam was obtained by arranging the different phases for each element. On the other hand, a low sidelobe was achieved by managing the power distribution of each patch using the Chebyshev polynomial. The proposed antenna was precisely printed and examined in an anechoic chamber to verify the characteristics of the antenna such as polarization, sidelobe level, and beam direction. Based on the measurement results, the proposed antenna has a tilted beam and a low side lobe that meets the specifications of the CP-SAR system.

In this paper, best arrangement of overhead transmission line conductors is determined via the ant lion optimization (ALO), to minimize the emitted electric and magnetic fields. Compute delectric and magnetic fields are compared with measured datain order to confirm the validity and usefulness of the formulation. ALO algorithm is applied to optimize both single and double circuit transmission lines. The two cases of spacing between line conductors are considered, namely, taking into account the effects of ice and wind, and neglecting the effects of ice and wind. IEC-71 standards are followed for the spacings in both cases. A MATLAB computer code based on ALO algorithm is written for finding the positions of line conductors that will minimize field emissions. Significant reduction of the fields is observed owing to the new optimized positions of conductors. The optimized results of ALO are compared with previous results obtained by genetic algorithm and particle swarm optimization. To the authors' knowledge, this is the first paper that applies ALO to organize high-voltage line conductors. Finally, to demonstrate the financial applicability of the solution, comparison is held between the cost of rearranging transmission line conductors and the cost of non-reducing the fields, based on a survey for people living near high voltage line in the populated city of Irbid in Jordan. Although the operating frequency for the examples in this paper is 50 Hz, the algorithm can be used for other power frequencies such as 60 Hz. The solutions are 2D, where infinite line length is assumed. Also, the algorithm uses the recommended exposure limits of 0.4 µT for the magnetic field and 5 kV/m for the electric field.

This article presents a compact, low profile, four ports multiple-input-multiple-output (MIMO.) antenna operating at the n38 and n41 5G frequency bands. The antenna has a measured -10 dB bandwidth of 2.5-2.9 GHz with isolation less than -11 dB. The designed antenna system employs open slot radiators etched on a single-sided rectangular PCB substrate with a total size of 40 ×100 mm², including a ground plane. The open slot radiators are symmetrically printed at the four corners of the rectangular substrate. The radiators are excited by 50-Ω strip lines. Rectangular-shaped slits are used as decoupling structures. MIMO parameters such as the envelope correlation coefficient (ECC), channel capacity loss (CCL), and mean effective gain (MEG) are being calculated using the measured results. The ECC is less than 0.1 over the entire operating band despite the antenna's small size. The proposed antenna shows good performance in two sub-6-GHz frequency bands for 5G NR applications: n38 (2570 to 2620 MHz) and n41 (2496 MHz-2690 MHz).

An elliptical shape patch (ESP) antenna with inverted U-shaped slots is proposed and presented in this paper for on-body communication. A coplanar waveguide (CPW) feed is used as ground to produce impedance matching, and inverted U-shaped slots are used to produce the ultra-wideband (UWB). The proposed ESP antenna model covers UWB characteristics in free space, and it is observed at 3 to 10.7 GHz. When it is implanted on flat tissue model of human body, the bandwidth is 2.2 to 10.8 GHz. The SAR values of 1.26 W/kg and 1.58 W/kg are observed on-body at 4.9 GHz and 7.3 GHz operating frequencies, respectively. The results with respect to radiation pattern, gain, reflection coefficient, surface current distribution are also presented.

Various resonance modes, high transmission, and quality factor with simple design are highly desirable parameters for realizing nano-integrated plasmonic devices. In the context, a plasmonic structure consisting of two straight waveguides MIM coupled one central defective circular nano-disk resonator (CNDR) is proposed in this work. The insulator and metal of the proposed plasmonic filter are air and silver, respectively. The plasmonic filter is designed and investigated numerically by using the finite difference time domain method (FDTD). Our simulation results indicate that the proposed plasmonic filter has two transmission peaks with a maximum transmission equal to 80 and 70 percent. The advantages of the proposed filter are the various resonance modes with high transmission peaks and high quality factor which reaches 35.27. In view of these features, our proposed structure of plasmonic filter has the potential to be employed in various devices such as plasmonic demultiplexers and sensors for optical communication purposes.

Reconfigurable intelligent surface (RIS) has been suggested as a promising solution to prevent wireless communication systems from transmission blockage. In this paper, the performance of reconfigurable intelligent surface in cooperative decode-and-forward relaying for hybrid radio frequency (RF)/free space optical (FSO) system is evaluated where parallel transmission of information occurs on the system downlink. In this network, the RF links in the system are assumed to follow Nakagami-m distributions while the FSO link is subjected to Gamma-Gamma distribution. Thus, the exact closed-form expressions of the system outage probability and average bit error rate are obtained to quantify the system performance. The accuracy of these expressions is justified by the Monte-Carlo simulations. Also, to get more physical insight from the derived outage probability expression, the asymptotic outage probability under the condition of higher signal-to-noise ratio (SNR) is provided. In addition, the results illustrate that the system and channel parameters significantly affect the performance of the concerned system. Furthermore, the results show that RIS-hybrid downlink system offers better performance than hybrid downlink system without RIS. Under the RIS system, the results demonstrate that RIS-hybrid downlink system outperforms RIS-FSO downlink system.

The design of an innovative breast model system that focuses on a wideband for the detection of malignant tumours is described. The planned antenna has an overall area of 18×28 mm² and a fractional bandwidth (FBW) of 99% across a frequency spectrum of 3.4-10 GHz. The suggested antenna has excellent impedance matching, a considerable gain of 3.95 dBi, maximum efficiency of 96.98%. Omnidirectional radiated patterns are verified in the frequency, and time-domain analysis is also investigated for breast tumor diagnosis. For detecting a breast tumor with accuracy, the suggested antenna S₂₁ parameters are evaluated together, including imaging outcomes of current densities and specific absorption rate (SAR). These findings show that the radiator and the whole system work well at finding the tumor.

Bipartite systems have become popular in emerging quantum radar and quantum communication systems. This paper analyzes the various correlation coefficients for different types of quantum radar measurement schemes, such as: (i) immediate detection of the idler photon events to be used in post-processing correlation with the signal photon events, (ii) immediate detection of the idler electric field to be used in post-processing correlation with the signal electric field, (iii) immediate detection of the idler quadratures to be used in post-processing correlation with the signal quadratures, and (iv) conventional analog correlation method of the optical parametric amplifier. The showcased results compare the performance of these different methodologies for various environmental scenarios. This work is important at developing the fundamentals behind quantum technologies that require covariance measurements and will permit more accurate selection of the appropriate measurement styles for individual systems.