A novel ultra wideband (UWB) multiple-input-multiple-output (MIMO) antenna with different polarizations and band-notch characteristics is proposed in this letter. The antenna consists of two monopole antenna radiating elements with gradual change structure, which are placed perpendicularly to each other and printed on each side of the substrate to achieve a wide bandwidth and different polarizations. Band-rejected filtering property in the WLAN band is achieved by etching a H-shaped slot and employing a resonant L-shaped strip on two antenna elements. The proposed antenna has a small size of 27×37×1 mm³ with a bandwidth of 128.6% (2.35-10.82 GHz). Within the required band, the isolation for the two ports exceeds 18 dB. The envelope correlation coefficient is also measured.

Circularly polarized graphene based transmitarray for terahertz applications is proposed. The characteristics of the graphene material is explained. The cell element of the transmitarray is made of square Quartz cell. Dual circular graphene rings are printed on both sides of the Quartz substrate. The graphene ring radius is varied to change the transmission coefficient phase and magnitude. The effect of the graphene chemical potential on the transmission coefficient is demonstrated. Transmitarray is composed of 9×9 unit cell elements. A circularly polarized circular horn is used to feed the transmitarray at f=6 THz. The left- and right-hand field components in the E- and H-plane are determined. The variation of the gain and the axial-ratio with the frequency are explained. The peak gain is 18.63 dB and 1-dB gain bandwidth is 6.8%. The transmitarray produces a circular polarization from 5.5 THz to 6.5 THz.

The recent extension of the orbital angular momentum (OAM) concept from optical to microwave frequencies has led some researchers to explore how well established antenna techniques can be used to radiate a non-zero OAM electromagnetic field. In this frame, the aim of the present paper is to propose a new approach to generate a non-zero OAM field through a single patch antenna. Using the cavity model, we first analyze the radiated field by a standard circular patch and show that a circular polarized (CP) TM_nm mode excited by using two coaxial cables generates an electromagnetic field with an OAM of order ±(n-1). Then, in order to obtain a simpler structure with a single feed, we design an elliptical patch antenna working on the right-handed (RH) CP TM₂₁ mode. Using full-wave simulations and experiments on a fabricated prototype, we show that the proposed antenna effectively radiates an electromagnetic field with a first order OAM. Such results prove that properly designed patch antennas can be used as compact and low-cost generators of electromagnetic fields carrying OAM.

This paper presents a new method for antenna pattern retrieval from reflection coefficient measurements. A reflective load with known reflective properties is placed close to the aperture of the antenna under test. The reflection coefficient of the antenna is measured at the antenna feed with multiple different reflective loads. The antenna pattern is then solved from the measurements with an inversion method. This paper derives and verifies the analytical foundations needed to implement the method, and demonstrates the method both by simulations and experiments for a pyramidal horn antenna at 30 GHz.

In this paper, a new approach for the radar cross section (RCS) reduction of patch array antenna is proposed. Complementary split-ring resonators (CSRRs) are etched on the ground of the proposed patch antenna array. A conventional 1 × 4 patch antenna array is designed with the central frequency of 5.0 GHz. The monostatic RCS of the patch antenna array with CSRRs can be reduced as much as 14 dB compared to that of the conventional array while maintaining almost the same radiation characters. For the case of φ-polarized incident wave, the RCS has been reduced in the angular range of -90° ≤ θ≤+90° in xoz-plane and this angular range is usually less than ±45° when using conventional methods of RCS reduction.

Due to the traditional recognition researches prevalently fastening on HRRP's amplitudes while almost completely neglecting the phases, this paper attempts to directly prove the discriminant availability of HRRP's phases via two proposed fusion recognition strategies. The first strategy includes three sub-processes, respectively, based on phase cosine, phase sine and their fusion. The second strategy also includes three sub-processes, respectively, based on phases, amplitudes and their fusion. Additionally, a trigonometric function couple (TFC) method is used to reduce the phase sensitivity. Several measured experimental results indicate as follows. Firstly, employing TFC can perform much better. Secondly, the two fusion recognition sub-processes apparently outperform the corresponding subprocesses constructing them. Finally, phase information usually has a better noise immunity compared with amplitude information, and fusing phase information into amplitudes may improve the traditional recognition performance. Therefore, the availabilities of HRRP's phases and the two fusion strategies have been experimentally proven.

The analysis of the scattering by a tilted perfectly conducting strip buried in a lossy half-space at oblique incidence is formulated as an electric field integral equation (EFIE) in the spectral domain and discretized by means of Galerkin's method with Chebyshev polynomials basis functions weighted with the edge behaviour of the surface current density on the strip. In this way, a convergence of exponential type is achieved. Moreover, a new analytical technique is introduced to rapidly evaluate the slowly converging integrals of the scattering matrix coefficients consisting of algebraic manipulations and a suitable integration procedure in the complex plane.

A compact coplanar waveguide (CPW) fed asymmetric slot antenna with dual operating bands is proposed. The slot is modified rectangular in shape and asymmetrically cut in the ground plane. A hexagonal patch fed by a two-step CPW is used to excite the slot. The feed itself is slightly asymmetric (shifted, with unequal ground planes). The asymmetric cuts on the slot together with the feed line asymmetry have helped in obtaining ultra wideband impedance matching. An extra resonance at 2.4 GHz for Bluetooth applications is obtained by cutting an additional meandered narrow rectangular shape slit in the ground plane. The prototype of the proposed antenna has been fabricated and tested. The measured 10 dB return loss bandwidth of the proposed antenna is 200 MHz (2.3-2.5 GHz) for the first band and 12.1 GHz (2.9-15.0 GHz) for the second band. The radiation patterns of the proposed antenna are obtained and found to be Omni-directional in H-plane and bi-directional in E-Plane. The measured and simulated results are in good agreement.

The design of a dual-frequency single-layer circularly polarized reflectarray with frequency selective surface (FSS) backing is presented in this paper. The proposed reflectarray consists of rotated cross dipole elements etched on an FSS-backed substrate. Compared with the conventional design, the FSS layer reduces the mutual effect between the elements of two bands between the elements of two frequencies. The technique of element rotation ensures the proposed reflectarray obtain excellent performance of circular polarization. A dual-frequency circularly polarized reflectarray with FSS backing is fabricated and tested. All the simulated and measured results demonstrate these advantages.

A miniaturized Gysel power divider/combiner(PDC) based on planar artificial transmission line (ATL) is presented in this paper. This planar ATL is composed of microstrip quasi-lumped elements and their discontinuities, and the ATL is capable of synthesizing microstrip line with various characteristic impedances and electrical lengths. For demonstration, the simulated and experimental results of the proposed PDC @1 GHz implemented on microstrip are given. Experimental results of the designed PDC agree well with the theoretical predictions. The proposed Gysel PDC circuit not only demonstrates low insertion loss at the fundamental frequency with compact size and high frequency suppression features, but also maintains Gysel PDC's high power-handling advantage. The occupied sizes of the proposed Gysel PDC are merely about 40% of the conventional Gysel PDC.

In this paper, initially a Planar Inverted Cone Metal Antenna (PICMA) is optimized for wideband wireless communication. Finally, a compact Shorted Planar Inverted Cone Metal Antenna (SPICMA) is developed by introducing a shorting strip on the radiating element of optimized PICMA. The PICMA is optimized to operate from 1.7 GHz to more than 20 GHz, and the SPICMA is optimized to extend the operating band from 1.05 GHz to more than 20 GHz resulting in size reduction of 38%. The proposed antenna yields bidirectional radiation pattern in E and H planes. Various characteristics of the antenna have been analyzed using Finite Integration Technique (FIT) based commercial software CST studio. The measured reflection coefficient agrees with the simulated result for the optimized SPICMA.

A broadband transition design between rectangular waveguide and GCPW is proposed and studied. The E-field of GCPW is designed to be gradually changed to that of waveguide via the simple tapered probes and metallic vias. The planar circuit of the transition is fabricated by low cost standard PCB process. The tolerance analysis for this transition is also given. A back-to-back transition prototype at Ka-band is fabricated and measured. The measurement results show that maximum insertion loss of 0.75 dB and return loss of better than 15 dB are obtained within a desired frequency range from 26.5 to 40 GHz. The measurement results agree well with simulation results, which validate the feasibility of this design.

An eight-way waveguide-based power combiner/divider is presented and investigated in the frequency range 7.5-10.5 GHz. A simple approach is proposed for design purposes. The measured combiner shows a good agreement between the simulated and measured results. Insertion loss is about -0.3 dB, return loss is less than -15 dB and isolation between adjacent output ports is better than -11 dB at 8.5 GHz and reaches about -14 dB at 9.5 GHz.

The hybrid approach based on the coupling of the Wave Concept Iterative Procedure method and the Frequency Domain Transmission Line Matrix method is improved. The proposed method reduces the computation time by solving waves at the planar circuit interface: the volumic method is replaced by an equivalent surface condition. Thanks to this new approach, planar circuits presenting inhomogeneous dielectric substrates are studied. The proposed approach is compared to other methods on several examples.

In this paper, flux of permanent magnet tubular linear generator (PMTLG) is modeled and analyzed. With the model, air-gap leakage flux coefficient can be expressed analytically in terms of permanent magnet dimensions and air-gap width. The validity of analytical expression of air-gap leakage flux coefficient is verified by finite element analysis (FEA) with a maximum error of 6.8%. Furthermore, longitudinal end flux's influence on the detent force of PMTLG is analyzed in detail with the model. A detent force minimization technique is deduced from the analysis results, and confirmed by FEA. Finally, after optimization of air-gap leakage flux coefficient and detent force, a PMTLG is built and experimented.

In this paper, the author studies, through numerical simulation, the classical analog of the electromagnetically induced absorption/reflection (EIA) in a planar metamaterial structure in the near infrared spectral region. The structure is designed by transforming an electromagnetically induced transparency (EIT) structure into an EIA structure using Babinet's principle. The structure exhibits a coupling between a bright mode (a complementary ring resonator (CRR)) and a dark mode (pair of parallel straight slits) imprinted on a glass substrate. A narrow absorption window, induced in a wide transparent window, is achieved by the structure and the strength of coupling is tuned by the degree of breaking symmetry and relative displacement of the two mode elements.

In this paper, an improved robust minimum variance beamformer against direction of arrival (DOA) mismatch and finite sample effect is proposed. Multiple inequality magnitude constraints are imposed to broaden the main lobe of beampattern. The conjugate symmetric structure of the optimal weight is utilized to transform the non-convex inequality magnitude constraints into convex ones. A quadratic constraint on the norm of weight is introducing to make further improvement on robustness against DOA mismatch and finite sample effect. The proposed beamforming problem can be reformulated in the form of the second order cone programming and solved efficiently by interior point method. Simulation results show that the proposed beamformer outperforms several other adaptive beamformers.

In this paper, a combination of Lumped-Parameters Model, Quasi-Poisson's equations and Conformal Mapping methods is used for predicting radial and tangential air gap flux density of Interior Permanent Magnet Synchronous Machine for calculation of cogging torque. In the proposed method, Lumped Parameters Model is used for calculation of saturation and flux leakage. Quasi-Poisson's equation is used for forming radial and tangential flux density in slotless stator, and finally Conformal Mapping is used to account for slot effects. Using the results of this method, cogging torque waveform can be calculated using Maxwell stress tensor and virtual work methods. To validate the method, results are compared with Finite Element Method results for a candidate Interior Permanent Magnet Synchronous Machine.

Geometrical modeling of induction machines under eccentricity conditions involves a significant number of self and mutual inductances. These inductances are functions of rotor angular position, and calculating them at each time step requires solving computationally-intensive definite integrals. Conventional techniques use numerical look-up tables, or employ approximated analytical expressions such as limited-term Fourier series expression of turn functions. The former approach needs large memory volume given the size of inductance matrix. Moreover, numerical interpolations are needed upon model execution, which significantly slows down the simulation. The later technique is computationally tasking for a large set of Fourier series terms, or lacks sufficient accuracy if only a few terms are used. Alternatively, computationally efficient closed-form solutions for self- and mutual- inductance expressions are presented here. The step variations of turn functions are considered which streamlines the model formulation. The experimental results validate the proposed model. In particular, the frequency spectrum of the stator current illustrates the ability of proposed technique to detect eccentricity.

A novel omnidirectional circularly polarized (CP) antenna with single feed is proposed for 2.4 GHz WLAN applications. Based on the zeroth-order resonance (ZOR) mode of epsilon negative (ENG) transmission line (TL), the antenna excites uniform vertically polarized E-field just as the monopole does. A modified Alford loop with electromagnetic coupling fed by L-shaped strip consists of four curved branches, which is placed on the top of the antenna and generates an equivalent horizontally polarized magnetic dipole mode. Once the two orthogonally polarized components are equal in amplitude but different in phase by 90˚, omnidirectional CP wave can be obtained. The measured results show that the impedance bandwidth (S₁₁<-10 dB) is 6% (2.38-2.53 GHz), and the 3-dB axial ratio bandwidth in the azimuth plane is very wide which achieves 54% (1.60-2.80 GHz). Additionally, the 3-dB axial ratio beamwidth is over 50˚ for radiation pattern in elevation plane. Moreover, the antenna achieves excellent omnidirectional right-hand CP performance with a variation of 0.5 dB in the azimuth plane and an average gain over 1.5 dB across the operating band, which are well applied to the wireless system.