A compact new dual band 4-port Vivaldi MIMO (Multiple-Input-Multiple-Output) antenna is designed for 5G mmWave applications. The proposed MIMO antenna resonates at two frequencies 28 GHz and 39 GHz, and it has dimensions 22x22x0.79 mm³. The Vivaldi structure etched on ground plane acts as a defected ground structure (DGS). The proposed antenna is fabricated on Rogers RT/duroid 5880 material having 0.79 mm thickness and 2.2 dielectric material. For high frequency and broad band applications RT/duroid material is suited to maintain low dielectric loss, and it works in high temperature places also. For the proposed four port Vivaldi MIMO antenna, the isolation between any two antenna elements is obtained below -21.59 dB. The bandwidths achieved for two bands are 4.64 GHz (26.31-30.95 GHz) at 28 GHz resonant frequency and 2.69 GHz (38.35-41.04 GHz) at 39 GHz resonant frequency for 4-port MIMO antenna. The gain achieved at 28 GHz is 5.65 dB and at 39 GHz is 5.53 dB. It is possible to achieve MIMO performance parameters such as ECC < 0.003, DG = 10, CCL < 0.4 (bits/s/Hz), TARC < -10 dB, and MEG ratio is 1.01. Simulated and measured results are compared, and the antenna is designed using ansys HFSS tool.

With the rapid growth of wireless communication systems, there is a rising demand for multi-input multi-output (MIMO) antenna systems capable of adapting to various frequency bands and operating conditions. This paper presents an integrated design for MIMO antennas based on a varactor diode as a promising component for achieving frequency agility in the proposed system. A dual-polarized system is achieved by employing a combination of two antennas. One antenna is situated on the exterior surface of the side-edge frame, while the other is positioned on the substrate surface. The spatial configuration enables the creation of orthogonal polarization orientations, specifically vertical and horizontal polarizations. In each element, varactor diodes are positioned to provide reactive loading. By incorporating varactor diodes with a variable bias voltage (0.5-10 V) into the antenna design, the resonant frequency can be dynamically adjusted, allowing the antenna to operate across a wide range of frequencies (4.3 to 6.5 GHz) with more than 18 dB of mutual coupling in the working band. The presented reconfigurable antennas are printed on compact dimensions of 15 x 25 x 0.8 mm³ using a Rogers RT5880 material with a relative dielectric constant 2.2. Because of its flexible frequency range, extensive tuning range, small size, and planar structure, it is well-suited for various current and future wireless communication applications, including cognitive radio, software-defined radio, and next-generation wireless networks.

The deep flux weakening (FW) switching point of the interior permanent magnet synchronous motor (IPMSM) is difficult to track accurately. After entering the deep FW region, the current regulator is easily saturated, and the current following capability is poor. Aiming at these problems, a deep FW control of the IPMSM based on thed-axis current error integral regulator (DCEIR) is proposed. Firstly, the deep FW switching point is accurately calculated by using the maximum torque per volt (MPTV) as the limit of the d-axis current. Secondly, through the study of the voltage deviation, it is found that the q-axis regulating current is related to the DCEIR. On this basis, a new transformation relationship between d-axis current and q-axis current in the deep FW region is obtained. Finally, the simulation and experiment results are compared with the conventional negative d-axis current compensation method (NDCCM). It is verified that the proposed method can successfully restrain the saturation of the current regulator and enhance the current following capability in the deep FW region.

In this communication, a compact metasurface-based circularly polarized antenna with inverted L-shaped slots engraved in the ground is proposed for biomedical applications. The prospective antenna operates in the two frequency bands covering Medical Device Radio Service (Med Radio) and Industrial, Scientific, and Medicine (ISM) bands with center frequencies of 2.45 GHz and 4.1 GHz respectively. On mounting the prototype on the body, the impedance bandwidth of 14.4% and 42.5%, peak gain of 3.04 dB, and AR bandwidth of 0.3 GHz and 1.1 GHz in the two frequency bands (2.31-2.67 GHz and 3.28-5.04 GHz) are obtained respectively. For validating the prospective design, an antenna with the size of 0.264λ₀ × 0.264λ₀ × 0.014λ₀ was fabricated on a Rogers RT/Duroid 6002 substrate and measurements were done in different scenarios. Link budget analysis of the device was also done for ensuring its communication ability.

The article presents a low-profile quad-port dual-band printed antenna designed for 5G applications. The antenna is printed on a 58.6 mm x 58.6 mm FR4 substrate with a thickness of 0.8 mm. It operates in the 5G spectrum between 3.3 and 3.8 GHz, specifically in the n77 band, with a 10 dB bandwidth impedance. This flexible operating range allows the antenna to cover future frequency bands essential for 5G applications. The design of the antenna focuses on minimizing the distance between antenna components, which results in a significant improvement in isolation performance, greater than 14 dB. This improved isolation allows for a high radiation efficacy of 85% and an overall gain of approximately 4.8 dBi over the operating range. To evaluate the Multiple-Input Multiple-Output (MIMO) performance of the proposed antenna, the researchers developed additional MIMO metrics, including channel capacity, the Envelope Correlation Coefficient (ECC), and Channel Capacity Loss (CCL). These metrics help assess the antenna's ability to handle multiple signals and maintain good performance in MIMO systems. This study shows that the proposed antenna is suitable for a wide range of applications operating over multiple frequency bands. This makes it a promising candidate for 5G applications, as it covers the necessary frequency range and offers good MIMO performance. The antenna's low profile and compact size also make it suitable for various compact and portable 5G devices.

To meet 5G requirements, designing an optimal antenna is challenging due to numerous design factors. Conventional electromagnetic modeling simulators require excessive time and processing power during the antenna design process. Machine learning (ML), an innovative technology, can be used in the domain of antenna design with favorable performance and can resolve problems that the previous conventional methods cannot. The main goal of this work is to create an antenna that operates at 28 GHz, which is a significant 5G band for the 5G futuristic infrastructure revolution, and to predict the return loss of an antenna using some machine learning models like K-Nearest Neighbor (KNN), Extreme Gradient Boosting (XG-Boost), Decision Tree (DT) and Random Forest (RF). On comparing results, all models perform well with over 83% accuracy. However, the Random Forest model predicts return loss with higher accuracy at 90% and lower MSE and MAE values of 1.99 and 0.827, respectively. Moreover, this antenna holds potential for 5G applications and can be efficiently optimized using a machine learning approach, saving valuable time.

Ship's movement on the sea surface will produce wake extending for several kilometers. In order to study the electromagnetic scattering characteristics of the composite scene of sea surface, ship and wake, this paper combines geometric optics with physical optics (GO-PO), Kirchhoff approximation (KA) and facet scattering field model of sea surface to calculate the electromagnetic scattering characteristics of this composite scene. Firstly, the geometric model of the composite scene of sea surface and Kelvin wake is established by using Elfouhaily omnidirectional spectrum and classical ship wave generation theory. Secondly, the generated geometric overlay model of the wake and the sea surface is combined with the ship to generate a composite scene model of the sea surface, ship, and wake. Finally, the scattering echoes of sea surface and wake are calculated by KA and facet scattering field model of sea surface, and the scattering echoes of ship is calculated by GO-PO. On this basis, the electromagnetic characteristics of the composite scene of sea surface, ship and wake under different conditions are discussed. The research conclusion has certain reference value for the detection of ship and wake in complex sea conditions.

In model-free sliding mode control (MFSMC) of permanent magnet synchronous motor (PMSM), the first-order sliding mode surface convergence state is asymptotic convergence, and the dithering of the first-order sliding mode surface causes the motor control performance to degrade when the motor parameters change. To save the problem, a model-free fast non-singular terminal sliding mode control (MFFNTSMC) strategy is proposed. Firstly, considering the perturbation of motor parameters, a mathematical model of embedded permanent magnet synchronous motor is established, and the ultra-local model of the speed link is summarized. Then, according to the defined fast non-singular terminal sliding mode surface and the new reaching law, a new mode-free sliding mode controller based on the speed link is designed, which weakens the jitter by eliminating the high-gain switching by the high-order sliding surface, and at the same time makes the system state converge to zero in a limited time. In order to more accurately track the speed tracking effect, an extended sliding mode observer (ESMO) is used to observe the unknown disturbance of the system in real time. Finally, simulation and experiment comparisons with PI control as well as MFSMC control confirm that the method proposed in this paper has better steady state and transient performance for PMSM.

This paper focuses on designing and manufacturing a compact microstrip diplexer, which operates at 3.5 GHz and 5 GHz for 5G and Wi-Fi applications, respectively. Indeed, two bandpass filters are combined to create the proposed diplexer. For making bandpass filters compact, a hairpin resonator is suggested and developed into an E-shaped resonator. To attain the central frequencies, a short microstrip stub loading the E-shaped resonator is proposed. The filters were combined by a coupling junction to form the final diplexer. The proposed diplexer exhibits good isolation that is better than 40 dB in the whole operational frequency band. Additionally, the passband insertion losses are about 1 dB, and the return losses are about 20 dB and 26 dB at the two channels, respectively. Moreover, the final size of the manufactured diplexer is 30 × 25 mm² (0.6λ_g x 0.52λ_g). These results confirm that the suggested diplexer is suitable for the demanded applications.

This paper presents a new compact dual-band slotted-ring monopole antenna (SRMA) with circular fractal elements (CFEs) design for WiMAX and C bands applications. Good improvements are obtained in widening the upper-frequency band of the proposed antenna and in miniaturizing its overall size. Antenna miniaturization is accomplished by employing a coplanar waveguide (CPW)-fed fractal-based SRMA loaded at its inside and outside of the ring's peripherals by two types of CFEs, namely, CFE₁ and CFE₂. The dual-band capability of antenna is realized by introducing in its ring's center a circular slit to act as a key parameter for band rejection characteristic. The design procedure starts from conventional circular monopole antenna (CMA), and evolution steps of antenna are performed until achieving the proposed antenna with aforementioned features. The simulated results in terms of reflection coefficient, gain, efficiency and radiation patterns are obtained by using CST MWS and HFSS programs. Due to the agreement between the CST and HFSS simulated results, the prototype of the antenna is fabricated on one side of an FR4 substrate with a volume of 20×22×0.8 mm³. Then the measured reflection coefficient is conducted, and it agrees well with the simulated counterpart. As observed from measurement, the antenna operates at two distinct bands of 3.15-3.75 GHz and 5.02-7.58 GHz that exhibits the proposed antenna to cover WiMAX, WLAN, C-, 4G LTE, 5G, and Sub-6 GHz bands. Also, the proposed antenna exhibits an acceptable gain and efficiency across the operating bands along with omnidirectional radiation pattern.

A three-way power divider based on Bagley polygon is here reduced in dimension by applying the concept of reducing delay line length by applying open circuit stubs. Whereas this technique is known in literature, the delay line reduction is done symmetrically by placing the stub mid-line, which would imply packing issues leading to a reduced size reduction. In this contribution a theoretical development on non-symmetric reduced length delay line is carried out, allowing for a more effective size reduction of the Bagley-based power divider. Measurements on a prototype designed at 2.45 GHz occupying less than half of the area of a canonical Bagley divider with comparable performances over a slightly reduced operational bandwidth prove the validity of the approach.

The paper presents a very compact hexagonal mm-wave antenna of dimension 9 x 5 x 0.25 mm³ with defected ground plane for mm wave applications. The parametric design analysis is done for circular patch and hexagonal antenna on the same defected ground plane, and performance parameters of the antenna are analyzed. The designed hexagonal antenna with defected ground plane is compared with existing planar mm antennas in literature and works in ultra wide band frequency at 40 GHz to 52 GHz with a minimum gain of 5.3 dBi and maximum gain of 6.5 dBi over the band and has total efficiency of 80-95.9%. Antenna characteristic behavior is analyzed by varying the length of notches of the ground plane and other parameters such as thickness of the substrate, dielectric constant, and width of the strip of antenna. The antenna equivalent model is presented and is also simulated using Linear Technology (LT Spice). The radiation patterns are analyzed, and S₁₁ impedance of the antenna is studied using Smith chart. The antenna is simulated using CST Microwave Studio simulation tool and fabricated, and the results are validated using VNA (Vector Network Analyzer). This antenna's low profile enables easy integration with micro circuits and can be used in applications such as fixed and mobile satellite, earth explorations satellite, space research services, broadcasting satellite services, international mobile telecommunication services, and High-Altitude Platform Systems (HAPS) services in mm-wave domain.

In order to reduce the complexity and cost of an N×M large planar array from a practical point of view, firstly, the array matrix is divided into four equal N/4×M/4 quarter regions, and then only one quarter is selected to be optimized. After that, this selected quarter region is tiled with a few irregular polyomino clusters (IPC) and then rotating it to the other three-quarter regions. This method is called Quarter Region Rotational Symmetry (QRRS). The copy from the selected region is rotated by three angles 90,180 and 270 degrees respectively until the main planar array is filled. Two methods of feeding clusters based on amplitude only and phase only were used to reduce the complexity further. In addition, the complexity can bereduced more by applying the thinning technique with clusters or building clusters for a part of the planar array. A genetic algorithm (GA) is used to implement these ideas until a radiation pattern (RP) useful for modern applications. An additional constraint is included in the optimization process represented by a mask to cover the pattern according to the desired shape. The simulation results showed that the RP can be fully controlled by applying the QRRS technique successfully while reducing the complexity of the feeding network to only 2.25% in the amplitude-only and phase-only cases, and 1.75% and 1.5% in the thinning and partially tiling cases, respectively. Moreover, a detailed design of the feeding network circuit of the main planar array based on IPCis given for practical implementation.

In the wireless power transfer(WPT) system of electric vehicles, the magnetic shielding performance often comes at the expense of the transmission efficiency. How to maintain high transmission efficiency while reducing magnetic leakage is a challenge. For this reason, this paper proposes a double-layer passive magnetic shielding coil structure for an electric vehicle WPT system. First, a leakage optimization method is given, and the optimal parameters for each shielding coil are obtained with this method. Second, according to the obtained coil parameters, a WPT system with magnetic shielding for electric vehicles is developed. The correctness of the proposed structure and method is verified by simulation and experiment. Finally, when the system output is 4 kW, the proposed shielding structure not only reduces the maximum leakage field in the target area by 54.64%, but also has a transmission efficiency of 94.8%.

A staircase-shaped printed monopole antenna (SPMA) with a partial ground structure for wireless applications is proposed. The performance parameters of the designed antenna have been evaluated by integrating a novel structure of frequency selective surface (FSS) with the antenna. A Polyimide dielectric material has been utilized for designing both the antenna and the FSS reflector. The proposed SPMA integrated with designed FSS reflector operates at dual bands from 2.18 to 2.83 GHz and 4.42 to 5.58 GHz with fractional impedance bandwidth of 25.94% and 23.2%, respectively. A single-layered FSS reflector with a 5 × 5 array size is employed to obtain optimum performance. The suggested combined structure of the FSS reflector integrated staircase antenna achieves an attractive peak gain of 7.87 dBi and radiation efficiency of 98.8%. The design methodology for the antenna and unit cell design of the required FSS, analysis of field and current distributions, fabricated prototyped models of antenna and FSS along with measured results are included and discussed in this article. The proposed antenna is suitable for modern wireless communication (WLAN/Wi-Fi etc.) applications at 2.4/5.2 GHz.

A low profile metasurface, which rotates the polarisation of incident electromagnetic wave upon reflection, is presented in this study. The design, which works over a large bandwidth of 67%, is achieved by combining the effect of a circle and a triangle forming a unit cell. By proper modification, the array is found to be useful in RCS reduction over a broad frequency range. Unlike many earlier designs, this structure is of single layer and can be fabricated using standard process on a thin substrate which is inexpensive and easily available. The results are presented with simulation and experiment.

Quartz-enhanced photothermal spectroscopy (QEPTS) technique is suitable for simultaneous measurement of multi-gas in near-infrared (NIR) and mid-infrared (MIR) bands with advantages of wide spectral response and high sensitivity. Here, we report a multi-gas sensing system based on QEPTS using NIR and MIR Lasers. A quartz tuning fork (QTF) with a resonant frequency f₀ of 32.742 kHz was employed as a photothermal detector. A continuous wave distributed feedback (CW-DFB) fiber-coupled diode laser with a center wavelength of 1.58 µm and an interband cascade laser (ICL) with a center wavelength of 4.47 μm were used as the light sources to simultaneously irradiate on different surfaces of QTF for scanning the absorption lines of carbon dioxide (CO₂) and nitrous oxide (N₂O). A multi-pass cell with an effective optical path of 40 m and a 40 cm absorption cell were selected for the measurements of CO₂ and NO₂, respectively. The developed sensor was validated by the detection of mixtures containing 3000 ppm CO₂ and 20 ppm N₂O. The relationships between the second harmonic (2f) amplitude of the QEPTS signal and the CO₂ and N₂O concentrations were investigated. Allan deviation analysis shows that this sensor had excellent stability and high sensitivity with a minimum detection limit (MDL) of 2.729 ppm for CO₂ in an integration time of 195 s and 0.038 ppb for N₂O in an integration time of 90 s, respectively.

In this paper, we investigate the propagation behavior of electromagnetic waves through coaxial optical fiber bounded with DB-boundaries. For this purpose, an eigenvalue equation is derived by using suitable DB-boundary conditions to determine the allowed values of propagation constant β for each propagating mode. Moreover, we have analyzed the electric field and power distribution patterns through coaxial optical fiber for different propagating modes and dimensions, respectively. Our results show that small dimensional guide confinement remains maximum close to the lower interface of the guide, whereas, for larger dimensions, it shifts toward the upper interface. Investigations show that high power is confined by H₁₂ mode compared to H₁₁ mode, and, therefore, shows contrary behavior compared to commonly used fibers.

A surface plasmon resonance-based arc-shaped photonic crystal fiber high-sensitivity refractive index (RI) sensor is proposed. An open arc-shaped analyte channel is produced at the top of the fiber to facilitate RI detection of the analyte, and a gold film is coated inside the arc-shaped structure to stimulate mode coupling. The performance of the sensor is analyzed by using the finite element method (FEM). The results have demonstrated that the sensor can detect a sensing range of 1.35-1.42 with maximum RI sensitivity of 24900 nm/RIU and resolution of 4.01×10^-6 RIU. Furthermore, the highest figure of merit (FOM) of 661.71 RIU^-1 is obtained. Additionally, the effects of air hole size and air hole distance on sensitivity are investigated. Finally, the proposed sensor characterizes great potential in biomedical, chemical, and other fields due to its excellent performance.

Wireless Power Transfer (WPT) technology can achieve non-contact transmission of electrical energy from the power grid or batteries to electrical equipment. To solve the problem of a significant decrease in output power caused by frequency detuning in a magnetic coupled resonant WPT system, it is necessary to dynamically adjust the operating frequency of the system. The frequency tracking control tuning using phase locked loop technology is currently the most commonly used method. A new method using incomplete cross S transform (ICST) for phase difference detection is proposed in this paper. Firstly, the low-pass filter is used to eliminate the noise of the original signals, and the waveform of the original voltage signal is changed from pulsed square wave to sinusoidal wave. Then the signals output by the filter are sampled synchronously to obtain a series of discrete signal sequences, and the sampling frequency varies with the operating frequency and is determined by the PI controller. Finally, the phase vector is obtained by performing ICST on two channel discrete signal sequences, and the phase difference, which is provided for subsequent frequency tracking controller, between the primary voltage and the primary current, is extracted from the phase vector. The computational complexity of S transformation is greatly reduced by utilizing incomplete S transformation. The effectiveness of the proposed method is verified by MATLAB simulation experiments. Several experiments were conducted separately. The accuracy, noise immunity, and real-time performance of this method are verified under different working conditions.