A new compact ultra-wideband (UWB) bandpass filter (BPF) with triple sharply notched bands and good stopband performance has been studied and implemented using a triple-mode stepped impedance resonator (TMSIR). The proposed TMSIR is found to have the advantages of introducing triple-notched bands and providing a higher degree of freedom to adjust the resonant frequencies. To validate the design theory, a new microstrip UWB BPF with three notched bands respectively centered at 5.2 GHz, 6.8 GHz, and 9.2 GHz is designed and fabricated. The simulated and experimental results are provided with good agreement.

By exploiting the micro-motion features of fast rotating targets, wideband radar has been successfully applied to high resolution imaging. However, due to the traditional fixed pulse repetition interval (PRI), the target image may suffer from aliasing in some practical situations. In this paper, under the compressed sensing (CS) radar framework, an efficient wideband imaging scheme with random PRI signal is introduced for aliasing reduction. Considering that direct application of the CS theory will result in large-scale dictionaries and high computational complexity, we firstly generate a low resolution image by applying modified generalized Radon transform on range-slow time domain and then scale down the dictionary column by reserving the atoms corresponding to those strong scattering areas. Simulation results show that this scheme can achieve aliasing-free images with acceptable computational cost.

Metal nanowires have drawn much attention due to the highly confined electromagnetic waves and relatively low propagation loss. With the increasing application potentials, we desire deeper insight into the mode behavior guided by metal nanowires for routing and controlling SPPs modes. Here, we apply the analytical solution for analyzing SPPs modes of metal nanowires. Single mode propagation condition and modes number are studied based on the analytical model. A universal formula of field diameters for all guided modes is presented, and mode field diameters are investigated. Finally, the intensity profiles of allowed guided modes are studied for specific dimensions.

This paper illustrates how inverse source problems are aected by certain symmetry and support priors concerning the source space. The study is developed for a prototype conguration where the field radiated by square integrable strip sources is observed in far-zone. Three symmetry priors are considered: the source is a priori known to be a real or Hermitian or even (resp. odd) function. Instead, as spatial priors we assume that the source support consists of a single or multiple disjoint domains. The role of the aforementioned priors is assessed against some metrics commonly used to characterise inverse source problems such as the number of degrees of freedom, the point-spread function and the ``information content'' measured through the Kolmogorov entropy.

This paper proposes a 77GHz microstrip series-fed patch antenna arrays for automotive radar applications. Based on the Taylor Distribution Principle, we designed a six-units series-fed weighted antenna array. A Wilkinson 1∶8 un-equal divider is employed to connect eight antenna arrays to form a whole planar antenna. In antenna far-field patterns, the E-plane side-lobe level is approximately below -20.15 dB, and the H-plane side-lobe level is about -15 dB. Good accordance is obtained between simulated and measured results. The designed antenna has great value in the application fields of 77 GHz automotive radar antenna.

This paper presents the study of an artificial material, made up of a periodic structure, defined by a unit cell, consisting of a finite number N of periodic layers of thin conducting cylinders placed between two dielectric planes. These artificial materials known as metamaterials can be regarded as a homogeneous material with effective constitutive parameters impossible to achieve with naturally occurring materials, such as negative values for both magnetic permeability and electric permittivity. An analytical model has been developed to study the effective electric permittivity of the whole system in terms of the unit cell dimensions and the frequency of the incident electromagnetic wave. Simulations of the effective electric permittivity of the metamaterial were performed by varying the geometry of the metamaterial. This analysis enables the design and construction of structures with properties that make them an attractive candidate for shielding applications in the range of microwave frequencies. The metamaterial has been constructed with four rows of 5 bronze conducting rods each. We have made experimental measurements of the shielding effectiveness of these materials when subjected to a electromagnetic plane wave with electric field polarized along the direction of the conducting rods, and conversely, with electric field polarized perpendicular to the rods. Non-zero values for shielding effectiveness were observed in the first polarization, and zero values in the second case.

A MIMO/Diversity antenna with triple notch characteristics is proposed in this article. The proposed antenna has triple notches in the WiMAX band (3.3-3.6 GHz), WLAN band (5-6 GHz), and X-band satellite communication (7.2-8.4 GHz) band. Defected Ground Compact Electromagnetic Band Gap (DG-CEBG) is a design used to accomplish band notches. Defected ground planes are utilised so as to achieve compactness in conventional EBG structures. The proposed WiMAX band, WLAN band, and X-band satellite communication band DG-CEBG structures show a compactness of around 46%, 50%, and 48%, respectively, over a conventional EBG structure. In these structures, decoupling strips and a slotted ground plane are used to enhance the isolation between two closely spaced UWB monopoles. The individual monopoles are 90° angularly separated with a stepped structure which helps to reduce mutual coupling and also contributes towards impedance matching by increasing the current path length. |S₂₁| or mutual coupling is found to be less than 15 dB over the whole UWB frequency range. The Envelope Correlation Coefficient (≤0.5) is within the acceptable limits over the whole UWB frequency range. Notched frequency depends on the parameters of DG-CEBG structures; when there is a change in these parameters notch frequency is also changed. A low cost FR-4 substrate with thickness (h) = 1.6 mm, permittivity (ɛ) = 4.4 and loss tangent (δ) = 0.02 is used for the proposed antenna, and it has a compact size of 58×45×1.6 mm³.

A novel design of Meandered Coplanar waveguide (CPW) fed CSRR loaded multiband antenna is presented in this paper. A compact triple band antenna is designed by etching CSRR slots on the radiating element. The proposed antenna shows good performance at all resonant frequencies. The simulation results are discussed and compared with the measured ones. The effects of CSRR loading on the radiating element are explained. Parametric studies are carried out and explained in detail. The proposed antenna is fabricated and measured, and the results are compared with the simulated ones. CSRR permittivity characteristics are explained to validate the results. The proposed antenna can be used for C-band, Wireless Local Area Network (WLAN) and International Telecommunications Union (ITU) applications.

This paper presents a compact slotted MIMO cube antenna operating at 5.8 GHz, consisting of three orthogonal slots, each with a distinct main direction of radiation. Each slot produces linear polarization enabling the structure to radiate three orthogonal polarizations. This provides spatial diversity which helps mitigating the effects of multipath propagation and enhances the diversity gain. The cube is filled with a dielectric with a relative permittivity, ε_r thus reducing the minimum dimension of the cube by a factor of 1/√ε_r . The antenna has a return loss of 20 dB and a coupling of less than -26 dB between the ports. This paper describes the principle operation as well as the design and manufacturing process of the proposed antenna.

A simple and compact diagonal matched feed structure is proposed for offset reflector antenna, which includes a square choke to radiate the desired conjugate mode (TE₄: a higher order rectangular coaxial cable mode) for suppressing the cross-polar power of an offset reflector antenna when the reflector is illuminated by the dominant diagonal mode (TE_V^D: a linear combination of rectangular TE₀₁ and TE₁₀ modes) radiated from the aperture of a central diagonal waveguide. Square choke is excited by two identical slots on the central diagonal waveguide using the longitudinal magnetic field of main operating mode TE_V^D. Wideband conjugate matching as well as impedance matching for broadband operation can be achieved by such radiating main mode and conjugate mode from apertures which are spatially separated. Based on the above configuration, a J-band matched feed structure is designed using HFSS software for a given offset reflector geometry. The proposed matched feed structure is fabricated and measured. The measured results are compared with simulated ones, and close agreements are found.

In this paper, three different types of graphene based tapered slot antennas are designed for ultrawideband (UWB) applications. The taper profiles for three antenna types are linear, exponential, and constant width. A single layer graphene sheet of 35 μm thickness is used to model the radiating element and feeding structure of the designed antennas. To feed the antennas, microstrip to slotline transition technique is adopted. An approximate analytical theory based on conical transmission line model is considered to authenticate the design of graphene based tapered slot antennas. Better impedance matching over 2-20 GHz is obtained by designing a balun in the form of a radial stub. Return loss, bandwidth, radiation pattern, and directive gain are the considered antenna performance parameters. Time domain solver of CST MWS software is used to evaluate the performances of linearly tapered slot antenna (LTSA), exponentially tapered slot antenna (Vivaldi), and constant width slot antenna (CWSA). The results obtained from CST are compared with that from HFSS to further validate the design. Simulation results with extensive parametric study confirm that the novel 2-D material graphene can be considered as a promising one to model UWB tapered slot antennas. Furthermore, the effectiveness of designed graphene based tapered slot antennas is revealed by comparing their performances with other existing UWB antennas. Moreover, as a UWB application, Vivaldi antenna shows promising results in microwave brain tumor detection.

The article presents a new topology of the high-speed synchronous electrical machines with permanent magnets with the tooth-coil windings with a stator magnetic core made of amorphous alloys for prospective unmanned aerial vehicles. This is a multidisciplinary design algorithm with optimization elements, which are proposed to design such machines. Based on the proposed algorithm, calculations of several topologies were performed by using computer simulation methods. In addition, the analysis of the rotor dynamics as part of the turbojet engine of the unmanned aerial vehicle and the calculations of the mechanical rotor strength were performed. To minimize the eddy-current losses in permanent magnets, the multicriteria optimization of the slotted zone was carried out by using genetic algorithms. A cooling system was proposed, and thermal calculations were performed. To verify the proposed design algorithm and to evaluate the efficiency of the amorphous alloy, a full-sized 5 kW experimental sample with a rotational speed of 60,000 rpm was created. Results can be used to create new promising UAVs and to design electrical machines for other industrial applications.

A method aiming to widen the upper stopband in a microwave bandpass filter based on two-conductor suspended-substrate stripline resonators is described in this letter. Applicability of the method is illustrated by simulating and fabricating fourth-order filter that has a very wide upper stopband: Δf_stop/f₀=7.92 measured at a level -50 dB, which is achieved because the widths of the inner resonators in the structure are 1.4 times greater than that of the outer ones.

The work presents a simple and novel design approach to extend the bandwidth of existing Dielectric Material Based Microwave Absorber (DMBMA). The design comprises planar square patches of DMBMA placed periodically on a metal-backed FR4 sheet. For demonstration purpose, the DMBMA is synthesized by adding conducting carbon fillers in polyurethane matrix, and its electromagnetic parameters are measured in X-band. A single reflection null is observed in DMBMA owing to λ/4 resonance. In comparison, the bandwidth of 8 GHz (10-18 GHz) is achieved for -10 dB reflection for square patch based DMBMA. The thickness of proposed absorber is 2.75 mm. An additional resonant mode is observed due to capacitive coupling between the square patches. The enhanced bandwidth is attributed to the overlapping of λ/4 resonance and induced coupling mode. A good agreement between the simulated and measured data is observed.

Electromagnetic levitation system is commonly used in the field of magnetic levitation system train. Magnetic levitation technology is one of the most promised issue of transportation and precision engineering. Magnetic levitation systems are free of problems caused by friction, wear, sealing and lubrication. In this paper, a new prototype of the magnetic levitation system is proposed, designed and successfully tested via SIMLAB platform in real time. In addition, the proposed system was implemented with an efficient controller, which is linear-quadratic regulator (LQR) and compared with a classical controller which is proportional-integral-derivative (PID). The present system has been tested with two different criteria: signal test and load test under different input signals which are Sine wave and Squar wave. The findings prove that the suggested levitation system reveals a better performance than conventional one. Moreover, the LQR controller produced a great stability and optimal response compared to PID controller used at same system parameters.

Nowadays everyone needs electronic gadgets in compact size, and single device should accomplish all the tasks. A compact MIMO antenna resonating at multi-band of frequencies is proposed in the current research work. The proposed MIMO antenna consists of two elements. The edge to edge separation between the two antennas is λ0/31 and still maintains low mutual coupling levels between the two antennas. The proposed MIMO antenna resonates at 4.75 GHz, 5.89 GHz, 6.74 GHz, 8.25 GHz and 9.82 GHz. The mutual coupling is reduced by -23.78 dB at 4.75 GHz, -25.71 dB at 5.89 GHz, -29 dB at 6.74 GHz, -32.79 dB at 8.25 GHz and -21.5 dB at 9.82 GHz, respectively. The performance of the proposed MIMO system was evaluated in terms of S-parameters, Envelope Correlation Coefficient (ECC), Voltage Standing Wave Ratio (VSWR), and Radiation Pattern. The measured and simulated results are presented.

In this paper, a 2 to 4 GHz Instantaneous Frequency Measurement (IFM) system is presented. The proposed design uses four band-pass filters to estimate the frequency value of an RF signal. The proposed design is an improvement of that presented in our previously published work. In this work, a new frequency estimator is developed, and a new methodology for designing the frequency response of the band-pass filters is proposed. These two improvements show better accuracy in estimating the frequency value. A closed form for the Standard Deviation (STD) and the bias of the new estimator were derived, and used to adjust the frequency response of the filters. The fabricated system showed a maximum error of about 11 MHz, for practical values of noise and measurements errors.

Understanding wireless channels in complex mining environments is critical for designing optimized wireless systems operated in these environments. In this paper, we propose two physics-based, deterministic ultra-wideband (UWB) channel models for characterizing wireless channels in mining/tunnel environments --- one in the time domain and the other in the frequency domain. For the time domain model, a general Channel Impulse Response (CIR) is derived and the result is expressed in the classic UWB tapped delay line model. The derived time domain channel model takes into account major propagation controlling factors including tunnel or entry dimensions, frequency, polarization, electrical properties of the four tunnel walls, and transmitter and receiver locations. For the frequency domain model, a complex channel transfer function is derived analytically. Based on the proposed physics-based deterministic channel models, channel parameters such as delay spread, multipath component number, and angular spread are analyzed. It is found that, despite the presence of heavy multipath, both channel delay spread and angular spread for tunnel environments are relatively smaller compared to that of typical indoor environments. The results and findings in this paper have application in the design and deployment of wireless systems in underground mining environments.

Matching networks for dual-band power amplifiers typically rely on complex, non-general techniques, which either use switches or result in large and lossy matching networks. In this work, mathematical optimization is employed to design the matching networks for multi-band power amplifiers. The theory of continuous modes is utilized together with accurate models for the device package to define the required impedance terminations theoretically thus allowing mathematical optimization to be used for the design. This technique depends on neither the network architecture nor the number of frequency bands. Therefore, simple and compact multi-band matching networks can be achieved. As proof of concept, a triple-band amplifier at 0.8, 1.8, and 2.4 GHz has been designed using the proposed method. The fabricated amplifier demonstrates maximum power added efficiencies of 70%, 60%, and 58% and output powers of 40 dBm, 41 dBm and 40 dBm for the three frequency bands, respectively. The presented design approach is highly suitable for the next generation of wireless systems.

The removal of ground surface influence from ground penetrating radar (GPR) signals in shallowly-buried objects is of great importance. The ultra-wideband (UWB) radar is a solution which uses short pulse to distinguish ground surface from shallowly-buried objects. In this paper, a novel method optimizes bandwidth based on designing a Gaussian signal. Experimental results confirm the proposed method efficiency.