A circular polarization multiplexing metasurface beam splitter operating at 15 GHz with polarization conversion effect is proposed. The unit cell is formed by alternately stacking 4 layers of metal and 2 layers of dielectric substrates cascaded along the propagation direction, separated by air. The resonant phase of the unit cell can be changed by changing the size parameters of the two arms of the metal cross patch, and the phase coverage of nearly 360° can be achieved in the direction of the two orthogonal linear polarization components, while transmission coefficient is above 85%. The circular polarization geometric phase covering 360° can be achieved by rotating the metal patch. The polarization conversion of the circularly polarized wave can be realized by setting the phase difference of the two orthogonal linear polarization components to 180°, and the polarization conversion ratio (PCR) at the working frequency is greater than 90%. The simulation and test results show that when the circularly polarized electromagnetic wave is perpendicularly incident on the metasurface beam splitter, the transmitted wave is divided into two circularly polarized waves with different exit angles and orthogonal to the polarization direction of the incident wave. This work may provide new ideas for the integration and miniaturization of traditional beam splitting devices and have important application prospects in fields such as multiple input multiple output (MIMO) systems.

A new compact CPW fed dual-band circularly polarized (CP) antenna for a broadcasting satellite application is presented. The proposed dual-band CP antenna consists of modified CPW ground structure by loading stub/slots/inverted L-strip and modified cross-shaped patch. A modified CPW ground structure can generate circular polarization (CP). The proposed antenna design provides the simulated impedance bandwidth (IBW) (S₁₁ < -10 dB) of 81.42% (3.16-7.5 GHz) and 20.53% (11.8-14.5 GHz), respectively, and the 3-dB axial ratio BW (3-dB ARBW) for two bands are 29% (4.18-5.6 GHz) and 8.86% (11.86-12.96 GHz), respectively. The proposed CP antenna provides a maximum gain about 3.8 dBi and 5 dBi in lower and upper bands, respectively, with right hand circular polarization (RHCP) radiations. The overall size of the CP antenna is 27 × 27 × 1 mm³.

Designing a multi-band bandpass filter (BPF) with controllable bandwidths is an alternative process to several technologies suggested by researchers. Hence, this paper presents a tri-band BPF in microstrip technology where T-shaped short-and-open stubs have alternating positions to use the maximally flat theory, based on the overall ABCD parameters of the circuit. The combination of the design Q-factor and the operating frequency to mismatch the design is the technique basis. The proposed structure comprises the quarter wavelength (λ/4) line section to develop a tri-band BPF frequency. All stubs are symmetrical relative to the center axis, while the prototype has been fabricated on a wafer of 22.42x7.62 mm². Using an FR4 HTG-175 with a thickness of 1-mm, dielectric constant ε_r=4.4, and loss tangent tanδ=0.02, the (4.06-4.283) GHz, (5.877-6.408) GHz, and (14.281-14.589) GHz are obtained referring to a 10-dB of the return loss. In contrast, the insertion losses at the center frequencies are 2.107/1.354/4.08 dB and the fractional bandwidths of 2.134%, 5.346%, and 8.645%, respectively. These covers WAS (including RLAN), ISM, and 5G applications. However, the attenuation coefficient is between 1.326 dB and 4.368 dB. The tri-band BPF prototype was validated using the Anritsu MS4642B 20 GHz Vector Network Analyzer. The measured and E-simulated results have been compared with good agreement.

A four-level iterated cantor set fractal antenna for Internet of Things (IoT) applications is proposed in this work. The proposed antenna operates at 2.4 GHz and for the range of 5 GHz to 8.5 GHz. In the 5 GHz to 8.5 GHz range it covers a Wi-Fi802.11 Standard (4.9 GHz, 5 GHz, 5.9 GHz, 6 GHz), 6.56 GHz, and at the lower band it covers WiMax (2.5-2.7 GHz). The proposed antenna offers a gain up to 4 dBi with an efficiency up to 90%. The designed antenna is experimented with a partial ground plane, with and without notch to perceive its effects on S₁₁ parameters. The antenna and its feed location is optimized for improved performance. The proposed antenna is analysed using the theory of characteristics mode analysis. The antenna is fabricated on a low-cost FR4 substrate with a dielectric constant of 4.4 anda substrate height of 1.6 mm. The antenna performance in terms of S₁₁, VSWR, and Gain is validated by measuring the performance in an anechoic chamber with Agilent N5247A Vector Network Analyser (VNA). The antenna is designed and optimized in mentor graphics software and CST Studio. The results show good agreement between the simulated and measured performances of the antenna. The optimized geometry of the antenna is compact having overall dimensions of 32 mm×22 mm×1.6 mm and suitable for short-range IoT applications.

Magnetic gear has high torque density and efficiency, and has a good application prospect in the field of low speed and high torque transmission. Accurate calculation of its air gap magnetic field is the key to analyze and design the magnetic gear. In order to improve the output torque of magnetic gear, the inner rotor is slotted, and copper bar is added in this paper. The air gap magnetic field of magnetic gear with rotor copper bar is calculated by two-dimensional analytical method. The solution domain is divided into four sub-domains, i.e., permanent magnets, air gaps, slots, and rotor copper bars. The solutions of Laplace's equation, Poisson's equation, and Helmholtz's equation are obtained by boundary conditions and continuity conditions. The distributions of air gap magnetic field, the induced current of rotor copper bars, and electromagnetic torque are obtained. The calculation results of this method are basically consistent with those of the finite element method, which proves the correctness and rationality of the analytical model.

To further improve the sensitivity of liquid dielectric constant measurements, a cylindrical container-type dielectric constant sensor is proposed in this paper. The container of the sensor consists of a substrate integrated waveguide (SIW) loaded with complementary split ring resonators (CSRRs) and a microstrip line. In order to solve the problem that the electric field distribution of the traditional container liquid dielectric constant sensor is only in a single plane, which cannot obtain good resonance characteristics, the sidewall of the sensor container is surrounded by a flexible material loaded with CSRR-SIW. Higher sensitivity can be obtained from measuring dielectric constant with more concentrated electric field distribution. The simulation results show that when the permittivity of the liquid under test (LUT) changes from 1 to 10, the resonance frequency of the sensor changes from 4.50 GHz to 2.94 GHz. The resonance frequency shift with unit dielectric constant greater than 150 MHz is realized. Using the relationship between the fitting permittivity and resonance frequency, the measurement of the known liquid permittivity of the standard sample is carried out. The test results show that the relative error is less than 2%, and the test sensitivity is 3.85%.

This paper proposes a dual-band circularly polarized antenna with ``X'' parasitic structures applied in the Beidou satellite navigation system. The innovation of this paper is to introduce the radome with ``X'' parasitic structures to broaden the beam width of the L-band and to improve the low-elevation gain of the antenna. Furthermore, high dielectric constant materials are used to realize the miniaturization and embedded application of the antenna. The measured results show that the VSWR of the L-band is 1.09 at 1616 MHz, and the VSWR bandwidth (VSWR<2) is 45 MHz (1589 MHz-1634 MHz). The VSWR of S-band antenna is 1.24 at 2492 MHz, and the VSWR bandwidth (VSWR<2) is 54 MHz (2471 MHz-2525 MHz). By adding the designed radome, the 20-degree elevation gain of the L-band is increased by 3.755 dBic. The measured results show that the gain variation at 20-degree elevations of the antenna at 1616 MHz and 2492 MHz are 4.981 dBic and 3.7 dBic, respectively. Moreover, the beam widths of the antenna at 1616 MHz and 2492 MHz are 130 degrees and 104 degrees, respectively. The antenna has an improved gain and a good roundness at low elevation angles, thus providing a favorable choice for navigation antenna solutions.

This article proposes a compact microstrip four-port dual circularly polarized (CP) multiple-input multiple-output (MIMO) antenna with polarization diversity for Sub-6G band. The proposed MIMO antenna consists of four antenna elements, two of which are left-hand circular polarization (LHCP), and the other two are right-hand circular polarization (RHCP). The circular polarization of each antenna element of the MIMO antenna is achieved by a microstrip feed line and a slotted ground plane with two rectangular strips. A novel decoupling element of the antenna composed of I-shaped and II-shaped metal strips is cross-connected and merged between the ground planes of the antenna to obtain wide axial ratio bandwidth and high isolation. The size of the proposed antenna is 55×55×1.6 mm³. The antenna of the impedance bandwidth (S₁₁ ≤ -10 dB) is 3.28-3.80 GHz (14.6%), and the axial ratio bandwidth (AR ≤ 3 dB) is 2.85-3.87 GHz (30.3%). Inter-element isolation less than -16 dB and the envelope correlation coefficient (ECC) less than 0.07 are achieved between the ports of the antenna. The proposed MIMO antenna achieves full coverage of CP characteristics within the impedance bandwidth. The proposed antenna is beneficial to the application of Sub-6G band. At the same time, it is also suitable for dual circular polarization communication and polarization diversity system.

A higher degree of miniaturization technique is presented based on frequency reduction method for a rectangular patch antenna by introducing slot on the radiating patch with unchanged antenna configuration. To realize the frequency reduction technique, a rectangular patch is design to operate at the fundamental frequency. Then a slot on the radiating patch is introduced and as an effect of slot, fundamental resonant frequency is shifted in left side in reflection coefficient plot. The percentage of reduction resonant frequency is 65.80% where 2.31 GHz is the fundamental frequency, and 790 MHz is the operating frequency of slot integrated patch geometry. In addition, we introduced another similar slot on the ground plane, and as a result, resonant frequency shifted from 790 MHz to 729 MHz caused by 68.44% reduction in resonant frequency with unchanged antenna dimension. Equivalent circuits have been analyzed for each antenna topology. To verify the simulated results, prototypes are fabricated and complied with measured results.

This study provides an alternative and straightforward approach to determining buried dielectric objects underground by employing the method of auxiliary sources. In the direct scattering problem, the Brewster angle is determined, and then the electromagnetic properties of the ground are determined. Later, the scattered field above the ground due to the buried object is evaluated. The localization of the buried object is obtained by the continuity of the field components while solving the inverse problem. The numerical experiments are done, and outcomes of the numerical experiments are compared with a commercial full-wave computational electromagnetic software. The outcomes reveal less than 1% deviation between the proposed approach and the commercial tool.

The impact of permanent magnet (PM) properties such as magnetremanence and coercive force or coercivity on the electromagnetic output of flux-switching permanent magnet machine having C-core stator topology is presented and compared in this work. A two-dimensional finite-element analysis (2D-FEA) approach is implemented using ANSYS-MAXWELL software package. Three-dimensional (3D) FEA calculations are also conducted, in order to realize more accurate results, and its results are compared with the 2D-FEA predicted results. The investigated machine elements are: airgap flux-density, torque ripple, total harmonic distortion (THD) of the voltage, cogging torque, unbalanced magnetic pull (UMP) or force, winding inductances, direct- and quadrature-axis flux, electromotive force and output torque. The analyses show that undesirable qualities such as large amount of cogging torque and UMP are predominant in the machine having rare-earth magnets i.e. neodymium and samarium-cobalt, although they have larger flux linkage and superior average torque compared to its non-rare-earth magnet equivalents i.e. the ferrite- and alnico-made machines. Moreover, the alnico- and ferrite-made machines exhibit larger winding inductance values, and consequently lower saturation withstand capability, though with better field-weakening capability. Further, the predicted efficiencies of the compared machine types having alnico, ferrite, neodymium and samarium materials, at rated current and speed conditions are: 79.8%, 75.76%, 87.22% and 86.58%, respectively. More so, the generated electromagnetic output power of the compared machine types at the operating base speed is: 206.57 Watts, 186.57 Watts, 449.67 Watts and 396.40 Watts, respectively. The investigated machine is suitable for high torque in-wheel direct-drive applications.

In this paper, the mutual coupling from a multiple-input-multiple-output (MIMO) rim antenna has been utilized to control the level of specific absorption rate (SAR), when the mobile handset comes in close contact to the human body. The proposed antenna is capable of operating at 2.1 GHz and 4.3 GHz, respectively. A periodic defective ground structure (DGS) in conjunction with diodes and capacitors are used to manipulate the coupling between antenna elements. The working of the proposed dual band antenna design is validated using the characteristic mode analysis (CMA), and the current distribution. The MIMO performance is studied by using envelope correlation coefficient (ECC) and loss in capacity analysis. The effect of hand and LCD on the antenna performance is shown. The SAR analysis shows up to 30% reduction, in comparison to the baseline value of the SAR of the proposed antenna design.

A novel ultra-wideband (UWB) antenna with triple band rejection capabilities operating in quad bands is presented. The proposed UWB antenna is derived from a planar rectangular shaped monopole antenna. In order to improve the bandwidth ratio of the antenna, a partial ground is maintained with a slot at centre along with truncated slots made at bottom two corners and a rectangular slot at top side centre of the radiating patch. In order to achieve the required triple notch characteristics and the multiband operation, a single meander line slot is made in the middle of the patch. The dimensions of the meander line slot are varied to change the notch band characteristics of the antenna. The FR4 substrate with dielectric constant 4.4 with thickness of 1.6 mm is used to design the antenna. The overall size of the antenna is maintained compact with dimensions 40 mm×38 mm. The proposed UWB antenna rejects triple bands 3.29 GHz-4.83 GHz (WiMAX), 5.15 GHz-6.84 GHz (WLAN), & 7.94 GHz-8.49 GHz (X-band satellite uplink). The operational bands of the UWB antenna with triple notch bands are as follows, 2.38 GHz-3.29 GHz, 4.83 GHz-5.15 GHz, 6.84 GHz-7.94 GHz, and 8.49 GHz-13.15 GHz. The measured peak gains at 2.7 GHz, 5 GHz, 7.3 GHz, 8.7 GHz, and 11.5 GHz are 3.4 dBi, 2.8 dBi, 3.6 dBi, 3.3 dBi, & 3.88 dBi, respectively. The step-by-step implementation of the triple notch band UWB antenna and the comparative analysis is presented. The proposed antenna performance is presented with the help of reflection coefficient, VSWR, gain, field distributions and radiation pattern curves. The simulated and measured analysis comparison shows good agreement making the designed antenna a good candidate for UWB applications that require multiband operations with selected bands rejection.

Six-pole hybrid magnetic bearing is a multiple input-output system with strong coupling between the degrees of freedom, a state feedback linearization dynamically decoupling the fuzzy immune PID controller for the subsystem after linear resolution coupling is proposed in this paper. Firstly, the basic theory of linear resolving coupling is expounded. Secondly, the proposed decoupling theory and control strategy are simulated in Matlab. Finally, the experimental platform is built, and the suspension experiments and coupling experiments are performed. It can be seen that the fuzzy immune PID controller has good performance, and the state feedback linearization method can realize the decoupling between the radial degrees of freedom of six-pole magnetic bearings.

A fractal antenna with enhanced bandwidth (BW) from 2.62 GHz to 5.2 GHz is presented for Wi-Fi applications. The antenna is designed to achieve a wider BW, and it consists of a rectangular shape patch attached to a half circular disc. The antenna is fed by microstrip feed model. The ground plane of the antenna is maintained partial with a slot at centre. Double head arrow cross shaped slots are etched on the radiating element to form the proposed fractal antenna. While the centre slot is made to look like + symbol, the surrounding four fractal slots are made to look like × symbol. FR4 substrate with dielectric constant 4.4 with thickness 1.6 mm is used to design the antenna. The overall size of the antenna is maintained compact with dimensions 44 mm × 40 mm. The dimensions of the fractal slots are varied, and the operating band is tuned. The proposed antenna covers from 2.62 GHz to 5.2 GHz with BW 2.58 GHz. The step-by-step implementation of the fractal antenna and comparative analysis are presented with the help of reflection coefficient curves. While the proposed antenna covers wideband, it showed peak resonance at dual operating frequencies at 3.2 GHz and 4.8 GHz. The designed antenna-maintained gain of 2.96 dBi and 3.47 dBi at 3.2 GHz and 4.8 GHz frequencies, respectively. The proposed antenna performance is presented with the help of reflection coefficient, VSWR, gain, field distributions, and radiation pattern curves. The simulated and measured analysis comparison showed good agreement making the designed antenna a good candidate for wideband Wi-Fi applications.

The multi-objective optimization of the six-pole outer rotor hybrid magnetic bearing (OSHMB) not only solves the nonlinear and strong coupling problems of the three-pole magnetic bearing (THMB), but also makes the magnetic bearing structure more compact and improves the maximum bearing capacity. Firstly, the structure and working principle of the OSHMB are introduced, and the mathematical models of suspension forces are established by the Maxwell tensor method. Secondly, the key parameters of the OSHMB are multi-objective optimized, and an optimal set of parameters is obtained through the sensitivity analysis, constructing the response surface model, and the multi-objective optimization based on the genetic algorithm. Based on the optimal parameters, the force current characteristics and maximum carrying capacity of the OSHMB are analyzed. Finally, the experimental platform is built. The suspension experiments, anti-interference experiments and load loading experiments are performed. It can be seen that the maximum bearing capacity of the OSHMB is about 9.6% higher than that of the SHMB.

For full duplex communication, a signal parallel transfer method based on partial power transmission couplers is proposed in this paper. The power transfer uses a serial LC compensation structure topology, and the data transmission channel adopts a double coupling resonant circuit. In terms of power transmission, some power coupling inductors and power compensation capacitors form a power resonance network with a high frequency trap function, which can isolate the influence of signal transmission. Therefore, there is no need for an additional trap, which reduces power loss and the space occupied by the structure. In terms of signal transmission, the partial coupling coil method can increase the coupling frequency and the data transfer rate. In addition, the signal transmission circuit has the characteristics of dual resonance frequencies. The forward and reverse signals modulate the carrier at different resonance frequencies to realize full duplex communication. Finally, the simulation results prove that the scheme is practicable for full duplex communication and parallel transmission of power, achieving anoutput power of 1.4 KW, and the highest transmission rate can reach 1 Mbps.

A dual-polarized wide-angle scanning array antenna is proposed in this paper. The proposed antenna array consists of sixteen elements with the working band from 9.5 to 10.5 GHz. A microstrip patch fed from two orthogonal directions is applied to achieve dual-polarization. In order to obtain good impedance matching and wide bandwidth of the antenna, capacitive coupling feeding is adopted. The measured results show that the proposed array can cover a wide scanning range of ±58°. The polarization isolations of antenna are higher than 17 dB. The isolations between receiving sub-array and transmitting sub-array are higher than 22.3 dB. The proposed array antenna is suitable for Van Atta applications.

In this paper, a novel tunable LC bandpass filter (BPF) based on LC magnetic-dominant mixed coupling is proposed. The design equations for the coupling coefficient and resonating frequency are given. The magnetic dominant coupling region and electric dominant coupling region are studied. The magnetic-dominant mixed coupling is used to compensate the bandwidth of the tunable filter, so that the tunable filter with constant absolute bandwidth can be obtained. The filter is designed, simulated and measured, and the measurement matches the simulation very well. The measurement shows that the central frequency tuning range is from 72 MHz to 222 MHz with -3dB bandwidth of 16.5±3.5 MHz.

This paper proposes a novel miniaturized interdigital capacitor loaded interdigital filter, which is applied in C-band (3.2 GHz~4.2 GHz). By loading an interdigital capacitor on the open end of the resonator of the interdigital filter, the length of the resonator is shortened by 28%. The resonant frequency offset caused by tap introduction is adjusted by using the method of impedance compensation at the open end of resonator 1 and resonator 5, which further reduces the size of the filter. The miniaturized filter is fabricated on a 0.254 mm-thickness alumina substrate with relative dielectric constant of 9.8 by thin film process. Measured results are as follows: the passband of the filter is 3.2 GHz~4.2 GHz; the insertion at center frequency is -1 dB; the return loss is less than -18.3 dB. The size of the filter is 4.98 mm*6.45 mm (0.15λ_g*0.20λ_g), which is 37.8% smaller than that of the traditional interdigital filter.