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.

To address the problems of torque ripple, vibration, and noise generated by cogging torque in a dual-stator single-rotor axial magnetic field permanent magnet motor, this article adopts an unequal thickness pole structure to reduce cogging torque. At first, the process of cogging torque generation is analyzed, followed by an examination of the mathematical formulation of cogging torque using the energy technique and the Fourier decomposition method. Then, the impacts of several pole optimization approaches on cogging torque reduction are then compared, and the findings are investigated using the finite element method to demonstrate the efficiency of the optimization method. The results show that the optimization effect of unequal thickness pole structure is the best. Lastly, the optimized motor's air-gap flux density, counter-electromotive force, harmonic content, and rotor mechanical strength were compared and studied to demonstrate that the unequal-thickness structure used in this research can increase motor performance. Finally, based on the determined motor parameters, experimental study of the prototype was carried out to verify the correctness of the motor structure and analysis.

Model predictive current control (MPCC) suffers from high computational effort, and control performance is affected by parameter mismatch. In this paper, a robust MPCC strategy with low complexity for permanent magnet synchronous motor (PMSM) is proposed, which reduces the computational complexity and improves robustness. First, a low-pass filter is used to obtain the current actual voltage, and the next-cycle voltage vector is obtained by angle compensation. And alternative voltage vectors (AVVs) are selected according to the location of the next-cycle voltage vector to reduce the control system computation. This part does not use motor parameters to avoid the influence of parameter changes. Then, the relationship between the current error and the input voltage and current sampling value is analysed. A low-complexity current prediction error compensation algorithm is designed to compensate the error caused by the mismatch of motor inductance and flux linkage, which enhances the robustness of the system. Finally, the experimental results demonstrate the correctness and effectiveness of the proposed strategy.

A Multi-Input Multi-Output (MIMO) dual-band antenna useful for advanced wireless services (AWSs) and wireless body area network (WBAN) applications is presented. To have dual bands of operation two techniques were used namely, Defective Ground Structure (DGS) and slotted patch. The lower operating band is spread over 108 MHz from 2.106 GHz to 2.214 GHz which covers AWS, UMTS, and LTE bands. The upper operating band is spread over 221 MHz from 4.141 GHz to 4.362 GHz which covers the WBAN band. The lower operating band is the result of perforation in the patch and inverted T-shaped ground, and the upper operating band is due to the two rectangular slots placed diagonal to each other in the patch and perforations in the ground. High isolation among MIMO elements is observed through a low Envelope Correlation Coefficient (ECC) of 0.0004. The design of a 2 × 2 MIMO antenna is realized using FR4 material with a size of 70 mm × 70 mm × 1.524 mm and Ansys HFSS tool. A high level of correlation between simulated and experimental results is observed which enables the presented MIMO antenna to be perfect for the proposed AWS and WBAN applications.

A super-wideband (SWB) antenna of enhanced performance is proposed to cover the frequency band from 3 to 30 GHz. The proposed antenna can be regarded as a two-arm antenna of fractal structure. Each of the antenna arms can be viewed as composed of multiple merged wideband fractal elements. Each fractal element is a wide-flare metallic sector-shaped radiator with circular (arc-shaped) edges to enhance the bandwidth over which the antenna impedance is matched to 50 Ω-feeder. A novel SWB balun is proposed for feeding the two-arm antenna of its balanced structure through the conventional coaxial feeder of its unbalanced structure. For experimental assessment of its performance, the proposed antenna is fabricated and measured by a vector network analyzer (VNA). The experimental results come in agreement with the results obtained by the CST® simulator. It is shown that the proposed antenna has a ratio bandwidth (RBW) of 10:1, percentage bandwidth (%BW) of 164%, and bandwidth-dimension ratio (BDR) of 1952. The efficiency of radiation of the proposed antenna is shown to begreater than 98% over most of the operational frequency band.

Advancement in radar component technology has led to a reduction in the size, weight, and power consumption of radar systems. Experimental radar systems can now be integrated onto smaller, maneuverable platforms, such as small unmanned aerial vehicles (sUAVs). Integration onto rotor-based sUAVs enables data collection over novel synthetic apertures which can be optimized for different scenarios. The design, simulation, and experimentation of a light-weight, ultra-wideband synthetic aperture radar (SAR) is presented here that will be used for the detection of obscured surface targets. The approach outlined herein uses 3-dimensional (3-D) imagery to vertically resolve clutter from the target. A vertical-grid aperture is presented which yields vertical resolution. Point spread functions are derived for both linear and vertical-grid apertures. The analytical expressions are verified using simulations. Finally, experimental data is used to form 3-D imagery and demonstrate the importance of vertical resolution in the discrimination between scatterers above the ground, as well as clutter mitigation.

A novel balanced-to-unbalanced (BTU) Bagley power divider (BPD) with input-reflectionless filtering characteristics is proposed. It features a balanced input port and three single-ended output ports, which is difficult to achieve by means of conventional BTU power dividers. The filtering characteristics are achieved by parallel coupled lines. To further improve the differential-mode filtering selectivity, stepped impedance resonators are applied to introduce two transmission zeros near the passband. The input-reflectionless characteristic in the bandstop region is achieved by loading absorptive branches. For verifying the proposed power divider topology, a prototype of microstrip BTU Bagley power divider operating at 1.0 GHz is designed and fabricated with 3-dB filtering bandwidth of 72%. Furthermore, 10-dB input-reflectionless bandwidth covers the full measurement frequency from 0 to 2.5 GHz. Good agreement between the simulation and measurement validated the proposed method.

In this paper, a wide harmonic suppression filtering antenna with high selectivity is designed. The filtering antenna adopts dual-layer structures. By introducing four parasitic patches around the top driven patch, the impedance bandwidth is widened. Moreover, the current directions on the driven patch and the parasitic patches are opposite in some frequency, so that the radiation null is introduced. In addition, a rectangular split ring DGS is etched in the middle of the ground plane, the lower sideband radiation null is introduced. Two sets of dumbbell-shaped defected ground structures are etched on the ground plane of the intermediate layer. The high-order harmonics are suppressed, and another radiation null is introduced. The experimental results show that the antenna operates at 2.46-2.66 GHz; the relative bandwidth is 7.8%; the peak gain is 3.8 dBi; and the S₁₁ is more than -3 dB at 3-13 GHz.