A compact spoof surface plasmon polariton (SSPP) low-pass filter is proposed. By adopting a novel fishbone structure, the effective depth of the groove is increased, reducing the filter width by 24.84%. The length of the filter is reduced by 22.23% with a new transmission structure. To intuitively display this structure, the filter is designed and fabricated. The area of the filter is 47.44 mm × 8 mm. The results demonstrate that the insertion and return losses are less than 3 dB and greater than 13 dB, respectively, in a wideband range of 0-10.00 GHz.

This article aims to exploit Ricci tensor with certain geometric properties which are used for feature representation and ship detection in synthetic aperture radar (SAR) image. The proposed method is composed of the following key points. Firstly, Riemannian metrics on the Gamma manifold are constructed based on the family of Gamma density functions. Secondly, direct calculation gives the Ricci tensor of Gamma manifold, where the curvature tensor resorts to the torsion-free affine connection. Thirdly, a general scheme for Zermelo navigation problem on the Riemannian manifold is addressed, and the solution of the navigation problem is proposed. Fourthly, feature representation problems are formulated as certain forms of Finsler metric of Randers type, indicating a joint framework for extracting low-dimensional features with closed-form solutions. Comprehensive experiments on real SAR image data sets demonstrate the effectiveness of the proposed method against compared state-of-the-art detection approaches.

A low-profile ultra-high frequency (UHF) radio frequency identification (RFID) tag antenna for double-sided anti-metal applications is proposed. The antenna comprises a middle layer of radiation patch, which is sandwiched between two layers of foam substrates, each with a thickness of 0.5 mm, and flanked by two layers of ground plane. A rectangular loop is designed on the radiation patch to expand the frequency band and optimize impedance matching. Particularly, one side of the radiation patch is shorted to the ground through a slotted stub to reduce the antenna size. The tag antenna is compact with a dimension of 38 mm × 20 mm × 1.15 mm (0.1159λ × 0.061λ × 0.0035λ at 915 MHz). When the two ground planes are individually mounted on metallic objects, the read distances are 5.4 m and 5.2 m, respectively. The proposed tag antenna demonstrates double-sided metal resistance, making it highly suitable for use in the industrial internet of things field.

A broadband circular arc-shaped slot antenna is proposed in this paper which operates from 25.1 GHz to 31.5 GHz. The antenna is based on a substrate-integrated waveguide (SIW) and fed through a grounded coplanar waveguide (GCPW). A circular arc-shaped slot is presented instead of a conventional narrow rectangular slot to extend bandwidth performance. The slot antenna generates six closely resonant frequencies by exciting high-order modes, which help get a broadband response. Antenna's prototype is fabricated using the standard Printed Circuit Board (PCB) process. The results of its measurement show that the antenna achieves an impedance bandwidth of 22.6% at 28 GHz and a peak gain of 11.5 dBi. The efficiency in the operating bandwidth is more than 85%. The antenna shows the merits of low-profile, high-gain, and broadband characteristics, which are very suitable for mm-wave wireless communication systems.

In the context of 6G communication technology, Reconfigurable Intelligent Surfaces (RIS) can effectively reconfigure signal propagation paths through the adjustment of their passive metamaterial reflector units. This capability mitigates the issue of radio wave attenuation in the complex environments of mine tunnels by optimizing signal paths, thereby reducing energy loss and minimizing coverage dead zones. By utilizing RIS-assisted multi-antenna terrestrial mobile communication channels and ray tracing techniques, researchers have established a wireless channel fading model specifically for rectangular coal mine tunnels. The results suggest that under comparable conditions, RIS technology enhances low-frequency signals (e.g., 2.4 GHz) more effectively than high-frequency signals (e.g., 30 GHz). Furthermore, these improvements are more pronounced as the size of the RIS increases.

In this study, an optimal multi-band microstrip fed metasurface antenna is designed. Three by three non-uniform circular radiating cross slotted elements make up the antenna's metasurface. The metasurface is analyzed using characteristic mode analysis (CMA), and the Modal Significance (MS), Characteristic angle (CA), and Eigen Value (EV) curves are utilized to optimize the antenna's performance. In addition, surface currents are examined for the metasurface and patch using CMA, and the design incorporates microstrip feeding to excite the targeted frequency bands. With its resonance frequencies of 5.4 GHz, 8.9 GHz, 12.8 GHz, 15.9 GHz, and 19.8-31.58 GHz, the developed antenna has potential uses in 5G and wireless communications. The suggested antenna achieves a gain of 10.05 on average. The prototyped model conformability analysis of the antenna is also performed, and good matching with simulation results is found.

A design of compact planar SIW filter with notch band characteristics is proposed. Double split square complementary split ring resonators are used to realize the ultra-wide band (UWB) characteristics. Proposed UWB filter contributes a passband from 2.9 GHz to 10.3 GHz with minimum insertion loss 0.7 dB at 3.7 GHz and maximum of 1.84 dB at 7 GHz. By employing complementary split ring resonator in the ground plane, a narrow band characteristic is obtained to reject the undesired wireless local area network (WLAN) signals. The notch band frequency ranges from 5 GHz to 5.7 GHz with insertion loss of 14 dB at center frequency. The 3 dB fractional bandwidth in the notch band is 12.9%. The variation of group delay less than 0.5 ns in the passband range. Overall size of the proposed filter is 0.35λ_g × 1.06λ_g. Because of these salient features, the proposed filter can be used for space applications.

Simultaneous realization of load-independent dual-type output, namely constant current output (CCO) and constant voltage output (CVO), is necessary in some wireless power transmission (WPT) application fields. Therefore, an S-CL compensated WPT system with dual-type output function is proposed in this paper. This proposed system consists of a two-coil loosely coupled transformer（LCT）which can avoid cross-coupling phenomena, a transmitter-side compensation capacitor, a receiver-side compensation capacitor and a receiver-side compensation inductor. Meanwhile, the proposed system can achieve near zero-phase-angle (ZPA) and zero-voltage-switching (ZVS) operations, avoiding power losses caused by reactive circulation. In addition, the theoretical analysis of the system's constant voltage and constant current outputs are further elaborated in this paper, and a test prototype is fabricated to verify the rationality and implementability of the proposed WPT system.

To solve the issue of chattering that occurs during the estimation of the rotor position in the permanent magnet-assisted synchronous reluctance motor using the conventional sliding mode observer (SMO), the saturation function is used in this paper instead of the original sign function to reduce its jittering effect; to solve the problem of phase delay caused by the low-pass filter (LPF), the adaptive law is implemented as a substitute for the LPF. This allows for a smoother back electromotive force and eliminates the need for position compensation caused by phase delay; finally, the phase-locked-loop (PLL) technique is used to extract more accurate rotor position information. A 3 kW permanent magnet-assisted synchronous reluctance motor is taken as the control object, and a simulation model of the control system is established. The results show that the improved saturation function adaptive SMO has higher level of accuracy in estimating rotor position information than the conventional SMO.

Wafer-level three-dimensional stacked integration technology is demonstrated in this paper, employing three gallium arsenide (GaAs) monolithic integrated circuits (MMICs) and gold (Au) bumps, and specifically designed for high-density and low-profile applications operating at millimeter-wave frequencies. A ground coplanar waveguide to ground coplanar waveguide (GCPW to GCPW) hot via interconnect has been developed to facilitate vertical transitions within a multi-stacked electromagnetic (EM) environment. Electrical connection between the upper and lower layers is achieved through 70 μm-height Au bumps. Compared to 2.5D packaging, this innovative structure exhibits an increased integration capability of more than three times within the same area, with a thickness of 0.451 mm. Ultra-wideband transmission between RF chips is achieved within a compact area of 0.16 square millimeters, enabling extremely short-distance interconnect for system-in-package configurations. Appropriate utilization of ground metal within the package ensures strict electromagnetic field confinement, preventing interference from adjacent circuits. The designed transitions were fabricated and characterized. The measured result has an insertion loss of less than 0.65 dB and return loss of better than 20 dB up to 40 GHz for a back-to-back structure. This integration technology can further enhance integration capability, reduce transmission loss, and improve electromagnetic isolation. The presented approach holds significant potential for applications requiring high-density integration and reliable performance in the millimeter-wave regime.

The magnetic field produced by overhead high voltage transmission lines has received extensive attention owing to its possible biological effects on humanity. The scientific community as well as general public are interested in the possible threats that living things may pose from the magnetic field. This research proposes a magnetic field mitigation approach near an overhead transmission line to avoid negative impact on the population around these lines. Apart from altering human brain activity and heart rate, magnetic fields can also lead to diseases like cancer. As a result, many techniques are employed to lessen that magnetic field. To reduce this magnetic field, scientists are looking for transmission line schemes. The suggested study investigates the influence of mechanical rearranging power conductors on magnetic field mitigation using genetic algorithm (GA) which is one of the evolutionary optimization techniques. The proposed GA has the objective to minimize the magnetic field as a fitness function and the location of conductors as genes considering their symmetry. The proposed method is tested using two published study cases of actual overhead transmission lines resulting in 48.4% and 57% reduction in magnetic field for case1 and case2, respectively. The contribution of the proposed method is to provide higher mitigation level of the mechanical rearrangement method depending on different sub-conductors spacing for one phase. The proposed mechanical rearrangement increases the geometric mean radius of the inner phase by optimizing its sub-conductors spacing within allowable critical ranges, thus the practical implementation of the proposed method requires a special design of the inner insulators string to support its sub-conductors.

In this paper, a very small 4-port MIMO antenna is designed, based on a metamaterial structure composed of embedded octagonal Split-Ring Resonators (SSRs). The antenna array shows an axial symmetry configuration with dimensions of 32 × 32 mm², corresponding to 0.157λ², approximately, related to a center frequency of 3.5 GHz, with a high electromagnetic isolation despite the radiators' closeness, reaching values bigger than 26 dB for adjacent antennas, and more than 28 dB for opposite antennas. The antenna is built on a substrate with dielectric permittivity of 2.2 and 1.27 mm thick. The Total Active Reflection Coefficient (TARC) presents a steady behavior for different random phases at the incoming signals, keeping a system bandwidth of 0.9 GHz for a -10 dB value. On the other hand, the Envelope Correlations Coefficient (ECC) reports values lower than 0.001 in all the antenna relationships, achieving a very uncorrelated performance of the electric fields in each element. The radiation pattern is quasi-omnidirectional, obtaining a low gain around -2 dBi, a trade-off that is considering the size reduction of the MIMO antenna.

Future 6G networks are anticipated to use reconfigurable intelligent surfaces (RISs) because of their capability to expand coverage, provide a customizable wireless environment, increase localization accuracy, etc. In this paper, RIS-aided localization is considered with orthogonal frequency division multiplexing (OFDM) and single-input single-output (SISO) downlink system in millimeter-wave (mmWave). An efficient beam sweeping (EBS) scheme is proposed accomplished by an RIS to scan the area of interest and estimate the direction of the user equipment (UE), i.e., the signal's angle of departure (AoD). The AoD with the measured signal time of arrival (ToA), from the RIS to the UE, is used to estimate the UE position. The ToA measurements can be obtained by exploiting the OFDM signal, while the beam sweeping can be obtained by carefully designing the RIS phase profile. The first step of the proposed EBS scheme is to scan the whole area of interest with equally spaced beam angles for coarse estimation of AoD. Then, based on this estimation, the RIS is reconfigured to sweep a slight angle's range by narrow beams to refine the AoD estimation. Besides, a multi-RIS scenario is proposed, and leveraging the EBS and the consensus fusion method is used to obtain accurate position estimation. Simulation results demonstrate that the proposed EBS in single and multi-RIS scenarios enhances positioning accuracy compared to linear beam sweeping (LBS) methods. Also, the impact of increasing the number of RIS elements and number of sweeping beams, as well as the number of RISs, is investigated thoroughly via numerical simulations. Furthermore, the achievable localization accuracy is assessed using the positioning error bound (PEB).

Aiming at the operational stability of DC-biased transformer, a multi-parameter correlation method based on electromagnetic coupling is presented in this paper. The mode-state analysis scheme is designed, and the feature parameters of electromagnetic, mechanical, and acoustic fields in internal components are simulated and analyzed. The electromagnetic properties under DC bias are simulated by the electromagnetic model, thus the winding current and magnetic flux density are extracted as the feature parameters. Then the vibration and stress distribution can be solved by the mechanical model, which are treated as the feature parametersof the mechanical field. By utilizing the computed mechanical information as excitation, the spatial-temporal distribution of sound pressure can be obtained in the acoustic model. Taking three-phase three-limb transformer and three-phase group transformer as examples, the electromagnetic, mechanical, and acoustic parameters of components are analyzed under different conditions. The variations of feature parameters are summarized and contrasted. Furthermore, actual vibration and noise parameters are measured through dynamic experimental platforms. The effectiveness of the multi-parameter correlation method is verified by the consistency between simulation and experiments, and the unobservable abnormal physical features can be represented by observable electrical information.

In this paper, a novel microwave oscillator is developed at frequencies of 5.7 and 7.5 GHz through the application of Negative Resistance and Harmonic Balance theory. The design process involves leveraging the Agilent Advance Design System (ADS) tool, ensuring exceptional electromagnetic (EM) performance. The utilization of microstrip circuit elements enhances the overall performance of the oscillator structure. Following optimization and co-simulation of nonlinear models for the compact Planar Microwave Oscillator (62x38 mm²), highly satisfactory results are obtained. Quantitatively, the measured output powers at 5.7 and 7.5 GHz are determined to be 9.5 dBm and 7.05 dBm, respectively. These power levels are particularly relevant for C band applications spanning 4 to 8 GHz, including areas such as satellite communication, radar, and wireless networks.

In this paper, a new UWB antenna for the Internet of Things (IoT) based on a left-handed structure is designed. The antenna utilizes a microstrip feeder and consists of a new complementary split ring resonator (CSRR) equipped with a three-stage double rectangular electromagnetic resonator (RER) to form the main radiator with left-handed characteristics. It also includes a double L-shaped parasitic patch and a slotted ground. The dimensions of the antenna are 0.42×0.42×0.013λ₀³. It covers the frequency band of 1.70-3.34 GHz (65.1%), which includes the communication frequency bands used by IoT antennas. The antenna exhibits good directional patterns within this frequency band. The measured peak gain is 5.49 dBi, making it suitable for applications in Wi-Fi, Bluetooth, Zigbee technology, and other fields.

A new non-dissipative and explicit finite-difference time-domain (FDTD) method is proposed for relaxation of the Courant condition of FDTD(2,6) in three and two dimensions. To the time-development equations, the third- and fifth-degree spatial difference terms with fourth- and second-order accuracy, respectively, are appended with coefficients. A set of optimal coefficients for the appended terms is searched to minimize the numerical error in phase velocity but relax the Courant condition as well. The numerical errors with the new method are more reduced than those with the previous methods for each Courant number. However, there exists a large anisotropy in the phase velocity errors at large Courant numbers.

In this paper, we explore interferences arising in the electromagnetic scattering by an object buried inside a layer with two rough interfaces by using the GPILE method. We show that there are two categories of interferences in the echoes that make up GPILE: the interferences that are present whatever the chosen scenario and those that come from the geometry of the problem (distance between the three scatterers). In this last category, we can cite for example the interferences which come from the position of the object, more precisely from its depth, because an object closer to one of the surfaces would produce echoes which arrive almost at the same time as those of the nearby interface.

This paper describes the design of an antenna and the development of a brain phantom model to validate the simulation results. The fabricated design of the phantom is interfaced with fabricated antenna, and the tumour in the fabricated phantom brain model is detected by return loss variation of the transmitted and reflected signals. Antennas are designed at the 2.45 GHz ISM (Industrial Science Medical) band and 5.8 GHz, and the lengths and widths for rectangular microstrip patch antenna (RMPA) have been calculated from the standard design equations. Different types of defects are applied in the front plane and ground plane of the antenna. Defect Ground Structures (DGSs) are applied to make the antenna ultra-wideband (UWB), because UWB is the basic requirement of antenna used in tumour detection applications. The design of gelatine brain phantom models with tumour and tumour-free is described. Finally, the brain phantom design is Interfaced to each deigned antenna. The tumour in brain is detected by variations in the incident and reflected wave reflection loss parameter.

A wideband, dual-element MIMO antenna operating in the 2.83-7.21 GHz frequency bands is presented in this study. The proposed design consists of a stub-loaded partial ground plane and a stepped feedline with a dual circular-shaped radiator on top. The designed MIMO antenna operates from 2.83-7.21 GHz, covering the C band (4-8 GHz) and 5G (sub-6 GHz) applications. The peak gain observed is 4.8 dBi at 6.2 GHz, with a maximum efficiency of 92% at 3.2 GHz. The minimum port isolation and ECC over the bands 2.83-7.21 are observed as 22 dB and 0.003, respectively. To achieve the best outcome, a parametric analysis of the proposed antenna is also simulated. Various diversity characteristic metrics, including diversity gain (DG), mean effective gain (MEG), total active reflection coefficient (TARC), channel capacity loss (CCL), and ergodic channel capacity (CC), are thoroughly analyzed to determine how well the MIMO antenna performs in terms of diversity. In all operating bands, the measured values provide good agreement with simulation results, indicating a strong candidacy for operation in the investigated bands.