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.

We designed a dielectric resonator antenna (DRA) that carries orbital angular momentum and has dual-band ultra-wideband characteristics based on the advantage of minor rain decay in L-band and C-band of microwave bands. The cavity of the antenna adopts an inner and outer nested spiral structure, and the material of resonant cavity shell is photosensitive resin. The internal medium is distilled water with a dielectric constant of 81, and the outer filling is saline with a concentration of 0.035 g/ml at room temperature for the dielectric constant. At the bottom of the cavity, we applied 2 feeds with phase difference of 90° to produce a circularly polarized beam in the DRA. Adjusting the size of the DRA and the height of the helical step surface to excite the OAM waves in higher order modes. The designed DRA generates resonance in 0.82-1.63 GHz and 3.35-7.27 GHz, and achieves ultra-wideband in both operating bands, furthermore, the antenna can generate OAM waves in l=±1 and l=±3 modes when operating at 1.51 GHz and 5.28 GHz, respectively. The simulation results match the measured results. The results show that the vortex wave generated by our designed antenna also has advantages such as high mode purity. Therefore, it can be effective in near-field communication and also provides a new solution for OAM near-field communication in 6G which is of great importance, and also for satellite communication and downlink signal transmission of communication satellites.

In this paper, a planar wideband antenna array with wide scanning angle in both E- and H-planes is proposed. The dipole antenna is used as an essential element of the array. To enlarge the scanning angle of the array, two layers of frequency selective surface (FSS) superstrates are loaded on the top of the antenna elements. A conducting-patch with shorting pins is loaded under the unit patch to enlarge the bandwidth of the array. Both simulated and measured results have confirmed that the proposed antenna array can scan up to 85° and 70° in the E- and H-planes from 8 GHz to 11 GHz, respectively.

This work presents a study where a Sinusoidal Corrugated Antipodal Vivaldi Antenna (SC-AVA) operating in the Ultra-Wideband (UWB) region is employed as a transducer for microwave imaging of a cancerous breast. The functionality of the antenna within the Ultra-Wideband (UWB) range is initially confirmed through thorough testing of performance parameters, including return loss, gain, radiation pattern, and group delay. Subsequently, its practical application in biomedical imaging is evaluated by measuring Specific Absorption Rate (SAR) readings at multiple frequencies within the operational range. The SAR readings are obtained from an EM simulator by modelling both homogeneous and heterogeneous breast phantoms and placing them in close proximity to the transducer. The SAR values are recorded at various frequencies, and it is determined that these readings comply with the Federal Communication Commission (FCC) regulations. The modelled SC-AVA is further utilized in the detection of a single tumor in a homogeneous breast phantom and multiple tumors in a realistic heterogeneous breast phantom. These phantoms are developed in a laboratory environment and imaged using an in-house developed monostatic microwave imaging setup. To gather preliminary information about the target, a homogeneous phantom with one tumor is imaged initially. Subsequently the heterogeneous phantom with two embedded tumorsis imaged in this study. The imaging results demonstrate that tumors of different sizes can be clearly visualized in both breast phantoms using the SC-AVA, employing image reconstruction algorithms such as Delay and Sum (DAS) and iterative Delay and Sum (it-DAS). Furthermore, a comparison of the reconstructed images reveals that the it-DAS reconstruction algorithm produces images with improved clarity compared to the DAS algorithm.

From the perspective of motor control and manufacturing process, the application of fault-tolerant permanent magnet rim driven motor (FTPM-RDM) in shaftless rim driven thruster (RDT) can avoid the complicated shafting structure in traditional propulsion system effectively, and realize the sensorless control while reducing volume. Referring to the fault-tolerant structure features, this paper introduces an improved sensorless control algorithm based on two-stage second-order generalized integral (SOGI) pulsating high-frequency (HF) voltage injection which is applied to the FTPM-RDM in zero and low speed. This algorithm can realize the rotor position estimation under fault and healthy condition. Based on pulsating HF injection method, HF square-wave voltages are injected in the virtual dq axis, and the initial rotor position can be extracted from the response currents of stationary reference frame (SRF). The sinusoidal voltage is injected into the virtual $dq$ axis, and use two-stage SOGI instead of the traditional filter is used to realize the current modulation without delay in low speed rotor position estimation. Combining the simulation and experiments, the proposed sensorless control strategy can estimate the rotor position accurately whether in failure or not and has good dynamic and static performance.

A brand-new four-channel mux system built entirely out of multicore photonic crystal fiber (PCF) structures, which permit wavelength multiplexing at 0.85, 1.19, 1.1, and 1.35 µm, has been confirmed. The multiplexer is a device that sends multiple messages or signals simultaneously via one communication channel. PCF is a category of optical fiber primarily according to the characteristics of photonic crystals, and it is an effective waveguide based on the interaction of microstructured materials with various refractive indices. Silica substance was used to fill up a few air-hole places to optimize the PCF mux structure along with coupling light between more nearby ports (cores) over the PCF axis. The low-index portions are air holes that may be found anywhere along the length of the fiber, and the background material is often natural silica.

A general theory of a passive multi-port system is presented, incorporating an arbitrary number of feed and load ports. The result is a nonlinear equation system, in which the solution variables are the load admittances, connected to the load ports. The solution ensures impedance match at all feed ports at one particular frequency. It is also shown how this theory can be applied to adaptive and reconfigurable antennas, by using switches to include or exclude some of the load admittances. If, by open state of a switch, the corresponding load admittance is excluded, then the nonlinear equation system is simplified. In general, one load admittance per feed port is required to obtain complex conjugate impedance match. Then, the admittance has a real and an imaginary part, where the real part relates to a resistor, adding loss to the system. It is shown how loss-less matching can be obtained by using two, purely reactive admittances per feed port.

In this paper, a novel design concept that uses multi-layer metasurface structures to design and develop bandpass filter screens is proposed. The unique proposition of the work lies in the control of transmission bandwidth of such metasurface screens, which has been obtained by sequential arrangement of unit cell layers, that comprise of Minkowski fractal-shaped unit cells and its complement. This reconfigurability of the structure is achieved without changing the geometry of the unit cell design, rather by stacking the layers in different configurations, or even by changing the substrate thickness, leading to the capability to obtain either narrowband or broadband filtering screens as per the requirement. An equivalent circuit model is proposed to explain such behaviour. Two configurations of stacked complementary surfaces, namely the Patch-Slot-Patch (PSP) and the Slot-Patch-Slot (SPS) designs have been investigated. The PSP structure on a thinner dielectric substrate offered dual band resonance with distinguishable transmission peaks, whereas the same configuration on substrate of increased thickness offered wider transmission bandwidth (45.5% to 50.5% percentage bandwidth). In comparison, the SPS structure offered much narrower transmission bandwidth (varies between 4.7% to 8.16%). The effect of changing the periodicity of the unit cell elements, without altering the fractal unit cell dimensions, has been described, through which one can control the band of operation and roll-off performance of the screens. The simulation results are found to be in good agreement with the measured results of the fabricated prototypes.

In this paper, a planar microstrip patch antenna operating in FCC MBAN for tumor detection is presented. The proposed antenna is constructed using a triangle-shaped patch with inset feeding. It is fabricated on an Arlon AD1000 substrate. Some of the parameters are assumed, and optimization is carried out to achieve greater performance. This prototype is placed on a human tissue mimicking model and simulated considering the cases of body model with tumor and without tumor. The designed antenna resonates at 2.37 GHz with 10 dB bandwidth of 3 MHz meeting the requirements specified by the FCC. Further, the introduction of a slot in the ground plane gives a half power beam width of 20.6° with directivity of 8 dB. This narrow beam is suitable for scanning application in microwave imaging. The fabrication of the antenna is carried out, and measurements are done to assess the performance of the antenna. Body phantom is created using petroleum jelly and mixture of wheat flour and water. The fabricated antenna is placed on the created model, and the variation in the resonant characteristics has been observed with the presence and absence of tumor.

With the gradual popularization of high-power electric vehicle wireless power transfer (EV-WPT) applications, the safety issue of human exposure to electromagnetic fields leaked from EV-WPT devices has received considerable attention. In particular, careful attention should be devoted to human protection from electromagnetic field issues among people with medical implants. Considering the electromagnetic coupling between a human aortic valve metal stent (AVS) and the leakage field, this study establishes a numerical simulation model of the electromagnetic exposure of a human implanted with AVS to the leakage electromagnetic field of EV-WPT on the basis of human medical ethics. Given the existence of many uncertainties in actual WPT charging, which may cause damage to a human heart implanted with AVS, an orthogonal matching pursuit sparse generalized polynomial chaos expansion (OMP-sgPCE) method is developed to conduct an uncertainty quantification of the maximum induced electric field intensity (E_max) of a human heart implanted with AVS. Results indicate that the induced Emax obtained by this method can exceed the ICNIRP guideline limit and may seriously endanger human heart safety. This study also adopts the Sobol method to obtain the degree of influence of the coil group's spatial location parameters and the AVS geometric parameters on the induced Emax, thereby providing a reasonable theoretical basis and scientific guidance for the optimal design of EV-WPT devices and AVS.

We propose a compact dual-band MIMO antenna for GSM 1800 MHz and WLAN applications. A novel single branch dual band antenna consisting of a quarter annular ring and an inverted U-shaped strip is designed by decreasing the electromagnetic coupling between higher order modes of an annular ring ultra-wideband (UWB) antenna, and a simple technique of slots and I and L-shaped stubs protruding from ground plane is employed to achieve high isolation. S₁₁ < -10 dB over 1.704-1.934 GHz and 5.66-6.25 GHz frequency range and mutual coupling S₁₂ < -20 dB and < -28 dB over the two bands are achieved. The radiation pattern, envelope correlation coefficient (ECC), total active reflection coefficient (TARC), diversity gain (DG), and mean effective gain (MEG) conform to MIMO specifications. The prototype antenna is fabricated on a 0.244λ₀ × 0.17λ₀ FR4 substrate, where λ₀ is the free-space wavelength at 1.7 GHz. The antenna offers stable radiation patterns. The antenna is compact, simple to design, easy to fabricate, and low in cost. These characteristics depict the suitability of this antenna for portable wireless devices.

In this paper, a method of designing a SIW (Substrate Integrated Waveguide) bandpass filter with high selectivity is proposed. Four resonant cavities of the proposed filter are arranged in straight line. The microstrip gradient line is directly fed into the cavities. Two U-shaped slots are etched on the top face of each cavity which will result in the resonant modes reduced and the high modes of SIW cavity pushed far away from the dominant resonant mode. Thus the filter will have both the features of compact size and wide stopband. The center frequency of the filter is designed at 5.2 GHz. The measured results are highly matched with the simulated ones.

Flux reversal permanent magnet machine (FRPMM) has been widely used because of its high efficiency, simple structure and high fault tolerance. However, the torque of the FRPMM is restricted by its longer equivalent length of air gap. To further improve its torque density, this paper presents two novel FRPMMs with auxiliary teeth and different magnetization modes. Both machines use auxiliary teeth without permanent magnet (PM), and both machines have three PM blocks on each main tooth. The difference of two machines is that they have different order of arrangement of PM. The design parameters of two machines are optimized based on genetic algorithm (GA). Finally, the back EMF and torque of the two machines are compared with the conventional FRPMM to show the superiority of the two machines. At the same time, the other important performances of the two machines are compared and analyzed, and their respective advantages and disadvantages are obtained as a reference for selecting the respective appropriate application scenarios.

In order to meet the requirements for the suppression of mirror frequencies in the 5G RF front end, this paper proposes a novel miniaturized image rejection bandpass filter by loading Stepped-Impedance Resonators (SIR). By analyzing the relationship between the impedance ratio of a half-wavelength SIR and its electrical length, we have designed an improved second-order bandpass filter, which reduces the size by 34.3% compared to traditional five-order hairpin filters. In order to further enhance the performance of the filter, the use of a radial stub, as opposed to the traditional rectangular open stub, allows for the generation of a wider band transmission zero, which can be analyzed using lumped equivalent circuits. This integration improves the stopband rejection of the filter. The results show that the passband range is 5.35 GHz-6.64 GHz; the rejection in the stopband range 8.10 GHz-11.98 GHz is over 45 dB; and the size is only 0.385λ_g×0.295λ_g.