In this paper, an ultrawideband linear cross polarization converter based on metasurface (MS) with wide incidence angle is presented and applied to the reduction of radarcross section (RCS) for planar and conformal surfaces. A pair of bow-and-arrow shaped split ring cells is printed onan FR4 dielectric substrate. The simulated and experimental results indicate that the converter achieves a cross polarization conversion ratio (PCR) of over 90% in 11.5-28.5 GHz (85% relative bandwidth), and that its oblique incidence performance can be stabilized at ±40° with a very small loss of bandwidth (1.65%). Then, the polarization conversion metasurface (PCM) cells and their mirror cells are laid out in a checkerboard array and applied to reduce RCS of planar and conformal surfaces. The planar PCM achieves more than 7 dB of RCS reduction in 11.4 to 29.6 GHz (88.8% relative bandwidth), and the conformal array with a center angle of 90°obtains more than 10 dB RCS reduction in 18.2 to 23.7 GHz. Due to its excellent performances, the proposed metasurface offers promising options for polarization control devices and stealth technology in Ku- and K-bands.

A metasurface that can be reconfigured for the conversion of linear-to-linear polarization has been designed, fabricated, and verified. It consists of dual co-centric split-ring resonators (SRRs), each of which has a pair of splits. It is specifically engineered to function in two reflection modes, one with polarization conversion and the other without. The unit cell achieves reconfiguration by utilizing two PIN diodes. Conversion of linear polarization to its perpendicular counterpart is achieved while the diodes are in OFF state. When the PIN diodes are turned on, full reflection without polarization conversion occurs. The proposed meta-surface operates over the 6.03-10.5 GHz frequency range. A 42×42 unit cell array is fabricated, and the results are experimentally verified. An FR4 substrate is used with copper ground plane on one side. The polarization conversion is measured and compared to simulation results for various incident angles. A Polarization Conversion Ratio (PCR) of ≥90% is achieved for incident angles up to 30°, with simulation and measured results showing good agreement.

This letter presents a wideband multi-linear polarization reconfigurable antenna, which has the ability to switch among four linear polarizations at rotation angle of 45°, namely 0°, 45°, 90° and -45°. Its main structure consists of three layers of substrates and a reflective cavity. Four pairs of crossed bow-tie dipoles are used as the primary radiators, and the polarization switching is realized by controlling the ON/OFF states of four pairs of PIN diodes between feeding source and the dipoles. In addition, circular ring and reflective cavity structures are used for enhancing the operating bandwidth, stabilizing the radiation patterns and increasing the gain. Finally, the simulation and measurement results both demonstrate that the antenna exhibits an overlapped impedance bandwidth of 42.6% (2.4 GHz-3.7 GHz) for all polarization states, and it remains a steady radiation pattern within the operating bandwidth. With these features, the design can be used in wireless communication systems in the 5G sub-6 GHz band.

This paper presents a circularly polarized double wall substrate integrated waveguide (SIW) fractal slot antenna array designed for X-band satellite applications. The proposed antenna demonstrates a reflection coefficient, covering the frequency range from 7.3 GHz to 8.5 GHz. The antenna is circularly polarized with a 3-dB axial ratio bandwidth ranging from 7.88 GHz to 8.58 GHz. The antenna array exhibits a gain variation between 11 dBi and 12.51 dBi. Moreover, the proposed design achieves an efficiency of 89%. With overall dimensions of 177 mm x 48.8 mm x 3.175 mm (4.8λ₀ x 1.32λ₀ x 0.086λ₀), the antenna array is compact and suitable for satellites with limited surface area. This compact form factor facilitates seamless integration into satellite systems without compromising performance. The proposed antenna is suitable to be employed for the satellite X-band telemetry application extending from 7.9 GHz to 8.4 GHz. A prototype of the proposed antenna has been fabricated and then measured using Vector Network Analyzer (VNA) and Anechoic chamber. The proposed antenna's measurement results match the simulated results.

This study aims to achieve the co-optimization of thrust force and thrust fluctuation using a long secondary double-sided linear flux switching permanent magnet motor (LSDLFSPM). Firstly, the motor model is constructed and derived using a theoretical approach. Subsequently, the motor parameters are subjected to sensitivity analysis using the Taguchi method to identify the significant influencing factors. Based on the screening results, the Response Surface Method (RSM) is employed to construct the test space and derive regression equations for thrust force and thrust fluctuation. The Multi-Objective Grasshopper Optimization Algorithm (MOGOA) is then utilized to iteratively optimize the regression equation for optimal parameter sizes. Finally, the optimized results are validated through finite element analysis (FEA) and compared with the original motor performance to demonstrate the effectiveness of the optimization approach proposed in this paper.

To reduce the coupling between closely packed antenna elements in multiple-input multiple-output (MIMO) systems, a method is proposed to reduce the coupling between planar inverted F-shaped antennas (PIFAs) by using cross slot defected ground structure (CSDGS). This structure includes four intersecting slits etched into the ground plane. The resonant frequency of the PIFA is within the bandgap of the CSDGS, effectively suppressing surface waves and reducing the coupling between antennas. Through simulation, it is demonstrated that the proposed structure achieves more than 35 dB isolation between two antenna elements. To validate the effectiveness of the method, the circuit of the simulated structure is processed and measured using a vector network analyzer. The measured results align closely with the simulated ones, confirming the viability of the proposed method. The parameter study and correlation coefficient of CSDGS are also analyzed.

Recently, clustered antenna arrays have been proved as an efficient method in implementing the large planar arrays for massive MIMO wireless communications in 5G and beyond applications. However, obtaining optimum clustering configurations needs a high computational time, and it does not guarantee a total clustering coverage of the whole array aperture. In this paper, a new and unconventional array pattern synthesis method based on ascending/descending clustered subarray rings is presented. The method is equally applicable to the rectangular and circular planar arrays where they are first divided into multiple square or circular clustered rings starting from the largest ring at the array perimeter up to the last ring (the smallest one) at the array center. Then the amplitude distributions of these clustered rings are optimized to obtain the desired radiation characteristics subject to the user-defined constraint mask. Implementation of the proposed array at the clustered level instead of the conventional element level offers many advantages such as simplified feeding network, efficient taper efficiency, low sidelobe level, and high directivity. Simulation results show the effectiveness of the proposed method for both square and circular planar array layouts.

Based on a framework recently published, the double-Cornu spiral antenna is extended to an array to enhance the gain. The designed array of 2×2-elements is of low profile and small sizes, has however a large effective bandwidth, and shows overall good radiation characteristics: enhanced gain, large axial ratio bandwidth, and high degree of polarization purity. Except for a few deviations, which are due to manufacturing tolerances, artificial noise and measurement uncertainties on the one hand and diffracted waves at external edges on the other, simulated results and experimental data fit well together. In addition, EMC along with signal integrity issues related to the reduction of noise and unwanted radiation have been addressed. The proposed antenna is suitable for 5G applications and radar systems. With 14.02 dB realized gain, 6.2 GHz effective bandwidth and an uplink data rate of 3.44 Mbit/s, the array is promising for many mobility applications.

We have developed a fast method of using Multiple Scattering Theory-Broadband Green's Function (MST-BBGF) for band field calculations. In this paper, we successfully extended the method to the vector electromagnetic case of 3D periodic structures. In the MST-BBGF approach, the broadband transformation to vector spherical waves for 3D is derived using the Broadband Green's function. The band eigenvalue problem is expressed in terms of the single scatterer T matrix which is independent of the periodic lattice nor the Bloch vector. For the first five bands, the dimension of the KKR eigen equation is merely 6, as 6 vector spherical waves are utilized for the scattered waves. We make extensive comparisons of the results with the commercial software COMSOL in both accuracy and computation efficiency. The CPU requirementon a standard laptop for the MST-BBGF method is merely 0.309 seconds for the first 5 bands. The MST-BBGF method is accurate and is at least two orders of magnitude faster than commercial software COMSOL. In the band field calculations, we employ the approach of extended coefficient to use the low order eigenvector of 6 to extend to 240 vector spherical wave coefficients without the need of re-calculating the eigenvalue nor the eigenvector of the KKR equation. The extended coefficients approach gives accurate band field solutions for the entire (0,0,0) cell.

The fusion of electromagnetic (EM) waves and information theory in wireless and waveguide communication technologies has enjoyed a remarkable revival during the last few years. In particular, unlike traditional transceiver systems, the recently proposed information metasurface system directly links the controllable binary array sources with the scattered EM waves, making the combination of EM and information theories highly desirable and natural. Moreover, a traditional linear channel matrix cannot be directly used for such scattering reconfigurability enabled communication system, making the information characterization of such system a great challenge. In this paper, EM information characteristics of a direct digital modulation (DDM) system enabled by programmable information metasurface, also known as reconfigurable intelligent surface (RIS), are analyzed, in which RIS is used as a modulator of the illuminating field, while the scattered far-field amplitudes are measured and effectively treated as the received quantities. The posterior probability for a specific source coding pattern, conditioned over a given measured scattering fields, is obtained through the Bayesian analysis technique, from which the average mutual information (AMI) is obtained to estimate the RIS observation capability along any particular direction. The averaged receiver mutual information (ARMI) is then introduced to characterize the generated field correlation structures along different observation directions. Based on ARMI, the joint observation capability is also analyzed. Furthermore, the suggested techniques are employed in a noisy environment, and a code selection scheme is put forth to achieve efficient information transmission. The proposed configuration is validated through a simulated experiment. As a comprehensive evaluation of the system's performance, the channel capacity of the system is derived, and a set of relevant influencing factors are identified and analyzed from four different perspectives: 1) the observation direction, 2) the size of RIS, 3) potential joint observations in multiple directions, and 4) the noise level. The proposed method, together with the various related performance measure metrics introduced therein, are expected to provide the research community with guidelines for analyzing and designing the current and future RIS-based communication systems, which can also be extended to other aspects in the growing field of the EM information theory.

The introduction of microfluidics technology with graphene provides many advantages, such as improving the selectivity and sensitivity, achieving chemical and thermal stability, decreasing the size of devices, and impoving the cell and The biological response of the substance. The principal objective of this paper is to compare the constitutive parameters in order to develop graphene-based microfluidic sensors. The simulation results illustrate that the suggested sensor exhibits a strong ability in detecting normal skin tissue with an exellent sensitivity of 6.060 (THz/RIU) and to identify skin cancer with a notably significant sensitivity of 4.59 THz/RIU. Additionally, it shows considerable figure of merits, with values of 550.9 and 353.61 RIU, respectively. In conclusion, the simplicity, effectiveness, and adjustability of the proposed biosensor render it well-suited for breast tumor detection.

In electrical machines, most of the iron loss estimation in finite element modeling is based on Bertotti coefficients obtained from the corresponding data sheet. However, often a more exact estimation of coefficients for the laminated steel material is needed. Especially in the case of high speed machines (where iron loss has the highest contribution to the total loss), it is very difficult to estimate the iron loss variation as a result of laser cutting when just using data sheet information as input data in finite element analysis. Laser cutting impacts also the magnetic properties, in terms of magnetization curves at different frequencies, not only the core losses. In this paper, three different core materials of the same lamination steel are prepared to realize the estimation of the Berttotti loss coefficient when the material is subjected to high frequency and under the stress of laser cutting. Experimental analysis is performed to obtain more precise values of Bertotti coefficients at a high frequency range so that they can be utilized in iron loss estimation in a high speed machine (100 krpm maximum speed-1667 Hz) which is further shown as an application. Finally, it is shown how frequency domain iron loss results can be utilized for the time stepping iron loss analysis.

In this paper, a comparison microwave method between Transmission and Reflection using a Coaxial Cable and complimentary double split ring resonator (CDSRR) for characterization of magneto-dielectric material is proposed. This method enables the determination of both relative permittivity and permeability of magneto-dielectric material. The CDSRR resonates at 3.46 GHz with a quality factor of 127 in unloaded condition. To determine the effects of permittivity and permeability on the shift of resonant frequency, the electric and magnetic fields are localized in two separate zones in the CDSRR sensor. Prediction formulas are proposed to extract the value of real permittivity and permeability from S₂₁ parameter. For Transmission/Reflection Method, to extract the dielectric and magnetic properties, Nicolson-Ross-Weir (NRW) are used. The prototypes of proposed sensors are fabricated on a ROGERS 3003 and tested for validation of their functionality. A good agreement between the measured data using Transmission/Reflection Method and CDSRR sensor is observed.

For applications involving triple bands, a small slot structure loaded with an asymmetric split ring resonator (ASRR) is suggested in this article. The slot mode, which is agitated with the help of a microstrip line feed, produces the first band. 2.24 GHz resonance frequency is the intended operating band. The sand third frequency bands are achieved by loading ASRR on the slot. The slot produces axial magnetic field required to excite the ASRR. The asymmetry introduced in the conventional SRR produces dual resonances. The ASRR gives the resonant frequencies at 2.97 GHz and 3.66 GHz. The frequency bands of the slot and ASRR can be independently tuned. The proposed geometry is verified experimentally, and it is in good agreement with the simulated one. The impedance bandwidth of all three resonant bands measured from experiment are 14.25%, 1.78%, 8.37%. The peak gains of 3.1 dBi, 2.18 dBi, and 3.29 dBi are obtained at resonant points, respectively. The designed antenna is compact and well suits for wireless application like WLAN, GPS, and LTE48/TD3600.

In dynamic wireless charging systems for electric vehicles (EVs), the coupling mechanism is difficult to align, which leads to high output voltage fluctuations and low transmission efficiency of the system. A reverse series double-layer symmetrical coil (RSDSC) structure with magnetic core is proposed. First, the mutual inductance characteristics of this structure are analyzed based on its coupling structure. Secondly, a mutual inductance optimization method is proposed to obtain the optimal values of each parameter of the coil and the optimal values of the magnetic core parameters. Finally, a wireless power transfer system is built based on the obtained coil and magnetic core parameters, and the correctness of the structure is verified through simulation and experimentation. The results show that the maximum mutual inductance fluctuation of the structure of RSDSC with magnetic core is only 4.88%, and the efficiency is up to 97.86% when the receiving coil is offset within 50% (20.8 cm) of the outer length of the transmitting coil.

A novel design of a dumbbell shape quad elliptical slotted (DSQES) antenna for directive ultra-wideband (UWB) integrated with WCDMA, WLAN, and mid-band of 5G applications is presented. Initially, a circular patch is designed by inserting four elliptical slots in radiator with a rectangular slotted ground plane. To realize ultra-wide impedance bandwidth, three symmetrical stepped rectangular slots are inserted in ground below a stepped-quarter-wave transformer feed line. The proposed antenna achieves fractional bandwidth (FBW) of 104% (S₁₁ < -10 dB) which covers UWB frequency range of 5.4-17.3 GHz at resonant frequencies 5.8/7.4/10.3/12/15.7 GHz. Further, a ground structure is customized by loading two asymmetrical meander strip resonators (MSRs), which provides extra lower frequency bands 2.1 GHz (1.96-2.21 GHz) and 3.5 GHz (3.22-4.07 GHz) for WCDMA, WLAN, and 5G mid-band applications, respectively. Furthermore, the measured gain and half-power-beam-width (HPBW) are 1.7-6.4 dBi and 75°-20° in 5.4-17.3 GHz UWB, respectively. The optimized dimension of proposed antenna is 30×30 mm² which is simulated on Computer Simulation Technology (CST) electromagnetic simulator using an FR-4 substrate of thickness 1.6 mm and dielectric constant 4.3. The simulated structure is computed by ADS simulator, and simulated results are validated with measured ones.

A dual-band dual-sense (DBDS) circularly polarized (CP) filtering dielectric resonator antenna (FDRA) with a quasi-elliptic band-pass response is proposed in this paper. The proposed antenna consists of a rectangular dielectric resonator (DR) with a Z-shaped strip at the top, a ground plane with a rectangular slot, and a microstrip feedline etched with a section of the spur line. By using the microstrip coupled slot line structure to excite DR with a Z-shaped strip, different senses of circular polarization are achieved in the two bands. The results show that the lower and upper bands are independently controlled by the strip and the DR, respectively. In addition, three radiation nulls are generated at the passband's edge by elaborately designing a half-wavelength open stub and etching the spur line. For demonstration, a prototype DBDS CPFDRA is fabricated and measured. The measurements illustrate that the antenna achieves a wide impedance bandwidth of 38.2%, as well as a dual axial ratio (AR) bandwidth of 2.2% for the left-hand circular polarization (LHCP) and 4% for the right-hand circular polarization (RHCP). The realized gain exhibits a decline of 25 dB at the passband edge, indicating high selectivity.

When demagnetization occurs, direct-drive permanent magnet synchronous wind generator exhibits problems of poor dynamic performance, weak immunity to disturbances and speed fluctuations. Aiming at these problems, this paper proposes a cascaded linear active disturbance rejection control method. First, the mathematical models of the generator during normal operation and demagnetization are described. Second, the linear active disturbance rejection controller (LADRC) for the speed and current loops is designed. The compensation for demagnetization disturbances at the speed loop's input is enabled by the control approach. The current output of the speed loop is imported as a rated value into the LADRC of the current loop. At the same time, the current is compensated at the input. Compensated speed and current accurately track the given values, and the goal of achieving demagnetization fault tolerance is met. Finally, this method is compared with dual-loop Proportional Integral (PI) control. The experimental results affirm that, under this control method, when demagnetization occurs, the speed fluctuation is reduced by 95.7%, the current response time decreased from 0.01 seconds to 0.001 seconds, and the electromagnetic torque ripple amplitude reduced by 50%. These experimental results fully validate the heightened fault tolerance and resistance to interference exhibited by the method advocated in this paper.

A Sierpinski Gasket Fractal Structure embedded in an Octagonal Microstrip Printed Monopole Antenna is proposed. The prototype is mathematically developed in a miniaturized cross-sectional area with ultra-wide resonance. A fractal design resembling a third-order Sierpinski gasket is applied to the octagonal radiator in a mutually proportional manner, increases the radiation across the entire surface area by extending the effective length of the dielectric. Additionally, the partial ground alters the resonant modes of TM11 and TM21 to a second-order iterative response via two contactless slots. Also, the driven radiator exhibits Fractional Bandwidth (FBW) of 156% spanning at 2.65 GHz-21.6 GHz, along with a peak gain 6.23 dB. The fabricated prototype demonstrates excellent agreement during testing and measurement using a microwave analyzer and an anechoic chamber, respectively. The proposed antenna covers resonance for applications at the S, C, X, and Ku bands. Also, it completely envelopes the Ultra-Wideband (UWB) and Sub-6 GHz 5G spectrum.

In the wireless power transfer (WPT) system of electric vehicles, the system leakage magnetic field and transmission efficiency depend on the coil structure, and the traditional unipolar coil has high transmission efficiency but generates high leakage magnetic field. In order to maintain the transmission efficiency while reducing the magnetic leakage and improve the safety index of the WPT system, this paper proposes a bidirectional inverse series coil of four meshes structure (FBISC), which maintains the high transmission efficiency of the WPT system only by the advantages of the coil structure without applying any metal materials and shielding coils. At the same time, the leakage field produced by the coil structure of the target area is less than the safety limit value, which makes the traditional shielding coils no longer necessary, and is light, clean, and highly efficient. First, the leakage magnetic field generated by the coil in the target region after energization is analytically calculated using a vector potential-based method for calculating the magnetic induction strength of rectangular coils. Secondly, a coil parameter assignment optimization method that weighs two structural performance indexes, namely, transmission efficiency and leakage magnetic field, is given to obtain the coil parameters that satisfy the given conditions. Furthermore, the proposed coil structure is compared with the conventional coil structure. Compared with the conventional unipolar coil, the bidirectional inverse series coil of four meshes reduces the leakage magnetic field by 56.4% and sacrifices only 2.38% of the transmission efficiency. Compared with the reverse double D coil (DD coil), the bidirectional inverse series coils of four meshes reduces the leakage magnetic field in the target region by 48.5% and sacrifices only 1.3% of the transmission efficiency. Finally, an electric vehicle WPT system with shielding is built to verify the correctness of the proposed structure. The results show that the leakage magnetic field of the FBISC coil structure in the target region is only 5.22 μT, and the transmission efficiency is more than 95% at an output power of 4 kW.