Herein is presented a two-dimensional negative permittivity unit cell for coaxial notch filter applications. This novel unit cell is developed through simulation in the context of an ideal infinite parallel plate waveguide, and preliminary implementation is demonstrated through simulation and measurement in a finite parallel plate waveguide. Finally, the unit cells are incorporated as an in-line notch filter in a coaxial transmission line, and their efficacy is demonstrated through simulation and measurement. The unit cell developed for this application was formed as a broadband fractal expansion of the traditional capacitively loaded strip. A partial repetition of the basic CLS I-shape was inserted in the capacitive gap on either side of the structure. This new unit cell was developed and simulated in HFSS using an incident TEM wave excitation in a parallel plate waveguide, and was shown to have two resonant frequencies of interest. The first resonance produces a wide bandwidth of negative permittivity (29.5%) from 1.3 GHz to 1.75 GHz; the second produces a region of negative permeability from 2.05 GHz to 2.45 GHz, a bandwidth of 17.8%. The current on the structure at each of these frequencies is presented, along with the pertinent fields in the waveguide. The effects of various alterations to the basic shape of the unit cell are also presented.
Desire for a broadband, high gain, unidirectional and low cost antenna in the field of communications is everlasting. In this paper, a novel broadband high gain antenna is presented using a suspended cylinder and a ground connected cylinder geometry. The bandwidth of the proposed antenna is enhanced by shorting these two cylinders with a pin in the direction orthogonal to the plane of coaxial probe. This low profile antenna structure is simple and easy to fabricate. The cylinders, shorting pin and ground plane are fabricated by a copper sheet of thickness 0.4 mm. Shorting pin and SMA connector provide mechanical support to the suspended cylinder. Simulations are done to analyze the radiation performance of the antenna. Prototype of the antenna is fabricated, and the measured results show good agreement with the simulated ones to confirm the enhanced bandwidth offered by the proposed antenna. We achieve impedance bandwidth of 63% (2.6-5 GHz) with the peak broadside gain of 9.87 dB. The bandwidth of the proposed antenna can be tuned by changing the radius of the shorting pin. The designed antenna possesses broadband high gain with stable broadside unidirectional radiation pattern which is suitable for Base station antenna such as WiMax (Worldwide Interoperability for Microwave Access) and LTE (Long Term Evolution). The metallic antenna has high power handling capacity as compared to microstrip and dielectric antennas.Therefore, this antenna can also be used for high power transfer application.
This paper presents a novel topology of a dual-rotor hybrid excitation motor (DRHEM), which combines outer permanent magnet synchronous motor (PMSM) and inner doubly salient electromagnetic motor (DSEM). The structure and combination criterion of the DRHEM are introduced and studied. A new type of intermediate stator structure has been adopted and fixed in the form of stator fasteners. The electromagnetic field of the motor is analyzed, and optimization methods are proposed for reducing the cogging torque and superimposing the back electromotive force. Furthermore, to verify the theoretical analysis, experimental tests are conducted, and the torque-speed and output power-speed characteristics are compared under various speeds conditions. The results verify the electromagnetic design well.
This paper analyzes the influence of simplifications in electromagnetic models used in the design of protections against High-Intensity Radiated Field (HIRF) threats. Both conductive and radiated effects are evaluated, covering the wide frequency range between 1 MHz and 6 GHz. A real and complex test case such as the power plant of an A400M aircraft was simulated using FDTD method so as to analyse the impact of different simplification approaches. The parameters studied are the inclusion/removal of installations, modification of electrical contacts, material properties, and changes in the cable features. In consequence, we can conclude that for the frequency range around tens or hundreds of megahertzs every detail is important (all the pieces of the model, accurate bundle routes and cable properties), while for higher frequencies only the details nearby the analyzed point are relevant for the results and it is not necessary to distinguish between different materials which are good conductors at this frequency range.
High frequency electromagnetic (EM) scattering analysis from the electrically large scatterers is important to the computational electromagnetics community. Meanwhile, the high frequency diffraction technique, like the uniform geometrical theory of diffraction (UTD), is very important when the observation point lies in the transition, shadow and deep shadow regions of the considered scatterer. Furthermore, the diffracted fields arising from the electrically large scatterers via the UTD technique are usually highly oscillatory in nature, which is named as the Fock type integrals with the Airy function and its derivative involved. In this work, we propose a Fourier quadrature method to calculate the Pekeris integrals. Moreover, we first adopt the Fourier quadrature technique to calculate the diffracted fields from the dielectric convex cylinder with impedance boundary conditions, like the creeping wave fields and NU-diffracted wave fields. On invoking the Fourier quadrature method, the results of total scattered fields at the fixed observation points could achieve 1 dB relative errors. Moreover, numerical results demonstrate that the computational efforts for the oscillatory Pekeris-integrals are independent of wave frequency with the fixed sampling density and integration limit.
In this paper, a simple and compact tri-band multiple-input-multiple-output (MIMO) antenna for wireless applications is proposed. The antenna is composed of two symmetric monopoles placed a distance of 0.106λ0 and occupies 0.26λ0×0.25λ0 board area. The tri-arm monopole offers operation over 2.1-2.7 GHz, 3.3-3.7 GHz and 4.9-5.35 GHz with percentage impedance bandwidth of 25%, 11.4% and 8.7%, respectively. An isolation greater than 20 dB is achieved by integrating a stub in the ground plane and adding a stub in the feed line. The structure exhibits stable gain and radiation patterns. Various performance metrics including envelope correlation coefficient (ECC), diversity gain (DG) and mean effective gain (MEG) are measured.
In this paper, B2-spline interpolation technique for Overset Grid Generation (OGG) and Finite-Difference Time-Domain (FDTD) method is developed. B2-spline or biquadratic spline interpolation offers better accuracy compared to the bilinear interpolation. The two-dimensional (2-D) numerical simulations are carried out for electromagnetic (EM) field analysis to measure the scattered fields for an unknown object in a free space and a dielectric medium. There are 2 antennas utilized in this work, each antenna will become transmitter sequentially to transmit a microwave pulses while another acts as receiver to collect the scattered fields in the OGG-FDTD lattice. In order to analyse the efficiency of proposed method, the scattered fields that collected by receiver antenna will be investigated with relative error. The results show that OGG-FDTD method with B2-spline interpolation gives lower relative error than bilinear interpolation with 0.0009% differences in a free space and 0.0033% differences in a dielectric medium. Hence, it proves that OGG-FDTD method with B2-spline interpolation has ability to measure the scattered fields around the unknown object efficiently. For future work, the proposed method can be applied to inverse scattering for detection and reconstruction of the buried objects with arbitrary shapes in a complex media.
A transmitting lens antenna using Huygens matematerials is proposed. The type of metamaterial has a 100% transmission. For obtaining a high gain antenna, a patch antenna is placed at the focal point of the metasurface as a feed source, and then quasi-spherical wave can be transformed to plane wave. As demonstration of the concept, a lens antenna, working at frequency of 10 GHz is designed, fabricated and measured. Numerical and experimental results agree well with each other. The measured results show that the gain has been enhanced about 11.2 dB.
A novel broadband ±45° dual-polarized magneto-electric (ME) dipole antenna is proposed for 2G/3G/LTE/5G (3.3-3.6 GHz)/WiMAX applications. The proposed antenna has Γ-shaped feeding strips to impart a wide impedance bandwidth for its special structure. Stable antenna gain and radiation pattern are realized by using a rectangular box-shaped reflector instead of planar one. The antenna is fabricated and measured. The measured results show that a common impedance bandwidth is 83% with standing-wave ratio (SWR) ≤ 1.5 from 1.59 to 3.83 GHz and port-to-port isolation larger than 25 dB within the bandwidth. The measured antenna gains vary from 8 to 10.8 dBi and from 8 to 10.6 dBi for port 1 and port 2, respectively. The antenna has nearly symmetrical radiation patterns with low back lobe radiation both in horizontal and vertical planes, and broadside radiation patterns with narrow beam can also be obtained. The proposed antenna can be used for multiband base stations in next generation communication systems.
In this paper, the correlation coefficients of skewed dipole arrays for antenna diversity are analyzed theoretically for each polarization characteristic and in various propagation environments. The correlation is not simply increased by two closely located antennas with different polarization characteristics and it is not decreased by increased antenna distance. This result is interpreted from the correlation analysis of two skewed dipoles with different polarization characteristics. The embedded beam patterns of the two skewed dipoles are calculated using the mutual impedances derived using the effective length vector (ELV) method; then, the mutually coupled correlation coefficients for θ, ϕ, and total polarizations are effectively derived. The correlations are also analyzed for various realistic propagation environments using statistical channel models with angular density functions and cross polarization discriminations (XPDs). Finally, this paper provides an effective correlation analysis for two dipoles and proposes optimal geometries for the two skewed dipoles in various propagation environments for each polarization characteristic and with environmental variables.
This paper proves that the use of conventional diagnostic methods of rotor crack and local demagnetization based on the harmonic analysis of the output voltage or counter-electromotive force is effective only with a certain ratio of the number of slots and poles. This statement was proved experimentally. The diagnostic method of the rotor cracks and local demagnetization which is universal for all types of windings and the number of slots of 2-pole synchronous electric machines with permanent magnets is proposed. The mathematical apparatus for the implementation of the proposed method is developed and verified with the help of FEM and experimental studies. All the experimental studies have been carried out for various rotor magnetic systems and a different number of stator slots.
In this paper, we are interested in the design of a new Ultra-Wideband (UWB) directional Vivaldi antenna with narrow beam, in the frequency range of 1.17 to 4.75 GHz. The simulation of the designed antenna is carried out on Computer Simulation Technology Microwave Studio (CST-MWS). The mutual coupling effect reduction is considered. The designed antenna is tested for Ground Penetrating Radar (GPR) and Through the Wall applications. The emitted waveform is a Stepped Frequency Continuous Wave (SFCW) signal, generated by a Vector Network Analyser (VNA). The acquired raw data are focused by using back projection algorithm.
In this paper, a novel stabilization scheme to prevent parametric oscillations in power amplifiers is presented. Based on a new oscillation detection approach, the inductive degeneration technique was used, for the first time, to successfully stabilize a high-power amplifier and prevent parametric oscillations. A 0.15 um AlGaN/GaN Microwave Monolithic Integrated Circuit high power amplifier operating at 5.8 GHz with 10% fractional bandwidth was designed and successfully stabilized using this approach. The proposed (4.7 x 3.7) mm2 three-stage amplifier achieves a saturated output power of 35 W with 29% power added efficiency and a large-signal gain of 26 dB.
An optimized design of Microstrip Log Periodic Dipole Array (MLPDA) antenna with non-cross feed structure is reported in this paper. Particle Swarm Optimization (PSO) is utilized to reduce the size and enhance the bandwidth of proposed antenna. Proposed design employs an improved feed structure of non-cross feed array antenna to avoid complexity of conventional feeding with long coaxial line and creating Co Planar Waveguide (CPW) feed. A simple FR-4 substrate with thickness of 1 mm is utilized for simulation using CST. A fitness function based on S11 parameter is used to achieve the optimization goal. A prototype of proposed PSO optimized antenna is developed to validate the simulation results. The proposed antenna offers higher bandwidth and significantly smaller size than cross feed LPDA antennas, with less complexity and low cost through parameter optimization, while maintaining the log periodic nature and gain.
This paper presents an analysis of the manufacturing technologies for the high-speed electrical machine with stator core made of amorphous magnetic material, their trends and perspective of development. The most efficient technology is determined. A design technology of sectional stator cores made of amorphous magnetic material is proposed. In addition, the paper shows the design methodology of the high-speed electrical machine with stator core made of amorphous magnetic material. A distinctive feature of the proposed technology is the implementation of the stator core made of amorphous magnetic material and laminated in the axial and radial directions. The fill factor for magnetic cores realized by this technology reaches 75%. The design methodology was tested on three prototypes of the high-speed electrical machine including the 120-kW prototype. The prototype experimental research is also presented in the paper. The main contribution is the loss minimization in the stator core made of amorphous magnetic material by 200%.
A broadband circularly polarized microstrip antenna with stable phase center is proposed for multi-mode GNSS applications. The proposed antenna consists of two crossed slots on one side of PCB and a Γ-shaped microstrip feeding structure on the other side of PCB. Measurement of the designed antenna demonstrates a -10-dB impedance bandwidth of 76.7% and a 3-dB axial ratio bandwidth of 64% are realized, which cover all GPS, BeiDou, Galileo, and GLONASS bands ranging from 1.164 GHz to 1.612 GHz. In addition, stable phase center for orientation in the region above 10˚ elevation is realized for high-precision positioning. For each GNSS band, phase center variation with respect to its own mean phase center can be retained within 5˚. Over the whole GNSS bands, phase center variation with respect to the common mean phase center is retained within 6˚.
A microstrip-fed two-port multiple-input-multiple-output (MIMO) antenna has been designed for triple-band applications covering the entire ultra-wideband (UWB) with one band-notched characteristic. A defected ground structure (DGS) has been used to obtain a wideband resonance. A crescent ring has been etched on each of the two circular patch antennas to produce a band-notch characteristic centered at 5 GHz, ranging from 3.96 to 6.2 GHz. These introduce notches at 5.2/5.8 WLAN, 5.5 WiMAX, LMI C-Band and also reject the large capacity microwave relay trunk network, ranging from 4.40 to 4.99 GHz, such as in the Indian national satellite (INSAT) system operating between 4.5 and 4.8 GHz, thus making our MIMO antenna immune to many unlicensed bands. The proposed MIMO antenna elements have been isolated by more than 16 dB throughout the operating band using a modified inter-digital capacitor (MIDC) placed between the circular patch antennas. The MIDC also helps in achieving a center-band, ranging from 6.2 to 8.93 GHz, and is useful in IEEE INSAT/Super Extended C-band. The lower-band ranges from 3.08 to 3.96 GHz and covers 3.5 GHz WiMAX while the upper-band, ranging from 10 to 16 GHz, is useful for X-band and Ku-band applications. Finally, the MIMO antenna has been fabricated on an FR-4 substrate of dimensions 50×30×1.6 mm3 with a compact antenna area of 0.158λ02. All results along with the diversity performance have been experimentally verified.
In this paper, wideband high-efficiency Fresnel zone plate (FZP) reflector antennas are investigated and developed. Two simple dual-dipole unit cells with different periodicity sizes are first characterized for the design of Fresnel zone plate reflector antennas. The gain bandwidth of the FZP reflector antennas is then theoretically investigated using the two unit cells. Based on the results, a wideband high-efficiency FZP reflector containing 15 correcting zones is designed using the unit cell with a smaller size and quarter-wavelength correction phases. A standard pyramidal horn and a slot-fed patch antenna are applied to feed the FZP reflector alternately. With a feed horn, the wideband high-efficiency radiation performance including a peak gain of 32.1 dBi and an aperture efficiency of 58.2% can be achieved. By using the designed planar feeder, a compact FZP reflector antenna can be obtained with compromised radiation performance. All are demonstrated by experiments.
A broadband monopole antenna is presented, with a radiating body consisting of a fractal tree with three-dimensional conical branches. The effect on polarization and return loss of varying the number of branches, as well as the number of fractal iterations, is explored and presented. The best-case antenna, having five branches and three fractal iterations, was fabricated using a 3D-printed form covered in conductive spray paint. The return loss of this antenna was shown in both simulation and measurement to be better than -10 dB from 1.22 GHz to 24.1 GHz, a bandwidth of more than 180%.
The paper presents a novel design technique for reflection-type varactor analog phase shifters based on tunable reflective loads. The reflective load comprises two similar tuning stubs with incorporated varactor diodes, where each varactor can be tuned independently. It is shown that by an appropriate losses equalization method applied together with a specific independent varactors control algorithm it is possible to achieve the desired 360° phase shift with stabilized losses, which are significantly lower compared to the well-known single-channel design. We derive and discuss in details main design relations arisen from the complex plane reflection coefficient consideration. The presented technique is first verified by circuit simulation in ADS, and comparison with the classical single-channel design is also considered. Next, we develop experimental prototypes of a reflective load and a full phase shifter based on a packaged silicon varactor diode for operation in C-band with 5.8 GHz central frequency. Experimental and theoretical results are in perfect agreement. Moreover, we have found that the bandwidth of the proposed phase shifter can be greatly enhanced if the reflective loads are tuned at each sub-band using a unique optimal tuning path. The suggested reflective load demonstrates the total bandwidth of 10.3% and the instantaneous bandwidth of 1.7% (sub-band), where inside each sub-band measured ripple at the central frequency is around 0.5 dB, and the maximum overall ripple is below 0.8 dB.