Wireless communications need antennas of different sizes, shapes, frequency-bands, bandwidths, and radiation patterns due to technical requirements, physical constraints, and FCC (Federal Communication Commission) regulations. For example, S-band antennas (2 GHz~4 GHz) are used in navigation, C-band antennas (4 GHz~8 GHz) used in Air-borne RADAR, X (8~12) band antennas used in Satellite communications, and millimeter wave (40 GHz and above) antennas used in autonomous vehicles. Ultrawide Band (UWB) antennas of different frequency bands have also applications in different fields such as medical imaging, radar imaging, software defined radios, surveillance, and health monitoring of different equipment. Microstrip patch antennas of different gains, bandwidths, shapes, and radiation patterns will play a vital role in different wireless applications of future 6G systems. In this paper, we have discussed different novel designs of patch antennas at different frequency bands: V-shaped patch antenna at 2.4 GHz, and hexagonal slotted half-circular patch antenna at 4.29 GHz. We have designed antennas of different shapes for different frequencies since some applications require UWB; some applications require narrow band but higher gain; and some applications require different gain/radiation patterns at the same frequency. We have designed a patch antenna at 2.4 GHz that can be used in Wi-Fi, and UWB patch at 4.29 GHz with omnidirectional radiation pattern that can be used in energy harvesting or biomedical applications. In this paper, we have also discussed the prototype development and testing results of the novel hexagonal slotted half-circular patch antenna at 4.29 GHz.
In this paper, a novel magnetic gear motor (MGM) with nonuniform air gap Halbach array magnetization is proposed to study the influence of temperature change on its electromagnetic performance. The inner PM adopts the Halbach array magnetization structure, which makes the inner rotor air gap have an uneven air gap structure, thereby improving the air gap flux density. In addition, the air gap magnetic field of MGM is analyzed by the finite element method (FEM), and the 3D model of the motor is established. The main losses of the motor, including copper loss, eddy current loss, and hysteresis loss are coupled to each component as a thermal source and studied by magneto-thermal coupling. The transient variation characteristics of loss distribution during MGM operation are comprehensively considered. The temperature variation of each component of the MGM with time during load operation is studied in detail. The results show that the temperature of the PM of the MGM is close to 91.8˚C when the rated load is running, and the PM of the motor does not undergo irreversible demagnetization.
Multi-vector model predictive control (MPC) of permanent magnet synchronous motors (PMSM) has two issues: selecting the optimal voltage vector (VV) combination is very complicated, and multiple prediction calculations to minimize the cost function result in a heavy computational burden; applying a VV with a short duration may generate narrow pulses, while the effect of reducing torque ripples and stator current harmonics is not obvious. The hybrid-vector model prediction flux control (HV-MPFC) strategy considering narrow pulse suppression is proposed in this paper. First, the optimal VV combination is quickly identified by the sector where the stator flux error vector is located, which lowers the control complexity and computational burden. Secondly, by the relationship between the action time of three VVs and the set time threshold, the hybrid-vector strategy to switch among three VVs, two VVs, and a single VV is employed to prevent the generation of narrow pulses. Finally, experimental results show that, compared with the existing three-vector MPC strategy, the HV-MPFC strategy effectively suppresses the generation of narrow pulses and achieves smaller torque ripples and stator current harmonics at the same switching frequency.
In XLPE cables, partial discharge (PD) is often accompanied by the generation of ultrasonic waves, which can be used to estimate the location and size of PD. Studying the propagation law of ultrasound along the cable is of great significance for establishing the mathematical model of PD and the layout method of ultrasonic detection terminal. This article adopted simulation and experiment to study the propagation law of PD ultrasound in cables. The results indicated that the propagation process of ultrasonic waves can be divided into three stages when ultrasonic waves propagate along the cables: the diffusion process with the characteristics of spherical waves, the propagation process which is rather similar to plane waves, and the transition process of both. When propagating along the cable, the ultrasonic amplitude attenuates and exhibits multi-peak characteristics as the distance increases. By analyzing the signal strength of the experimental results, it was found that the ultrasonic amplitude decays exponentially with propagation distance due to viscous heat loss of materials and the air gaps between cable layers, which provided a reference to the placement of distributed ultrasonic terminal for insulation weakness and design of spatial localization algorithm for PD.
A Coplanar Waveguide (CPW) fed antenna with a T-type slot and Partially Reflecting Surface (PRS) for gain, bandwidth, and efficiency improvement is presented. The antenna is miniaturized to get size reduction of 46.50%. The miniaturized antenna covers frequencies in C band. The presented antenna structure is easy to design and has size of 0.682λg x 0.99λg x 0.053λg. The PRS with parasitic patches is placed on top of the antenna at a distance of 0.25λg. The presented antenna design has a bandwidth of 4.42 GHz (Antenna~1) and 3.87 GHz (Antenna~2) with a percentage bandwidth of 75.81% and 59.58% respectively having average radiation efficiency above 90%. The gains obtained are 7.03 dBi and 6.12 dBi for Antenna~1 and Antenna~2. The gain has < 3 dB variation over the complete band. The obtained results support the design and make the antenna suitable for C band applications.
A compact four-element multiple-input multiple-output (MIMO) antenna is proposed for 5G applications. The offset fed antenna structure is designed from a rectangular and semicircular monopole antenna. In this novel MIMO structure, the surface current and near fields of left element are mainly concentrated toward left and that of right element towards right, and thus high isolation is achieved between left and right elements even without using any isolation technique, whereas the little surface current at the nearby edges of top and bottom elements helps in achieving high isolation. The fabricated prototype has board dimensions of 0.374λ0×0.275λ0, where λ0 is the free-space wavelength at 3.3 GHz. The structure offers isolation > 20 dB between the elements over 3.3-6.3 GHz. The envelope correlation coefficient (ECC), diversity gain (DG), and mean effective gain (MEG) confirm to MIMO antenna specifications. The antenna offers stable nearly omnidirectional radiation patterns.
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 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.
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 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.
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.
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.