In this paper, a novel printed monopole antenna for ultra wideband applications with variable frequency band-notch characteristic is presented. The proposed antenna consists of a stepped square radiating patch with modified W-shaped slot and a ground plane with rectangular sleeve and pair of L-shaped resonator which provides a wide usable fractional bandwidth of more than 130% (3.05-14.7 GHz). By cutting a modified W-shaped slot with variable dimensions on the radiating patch frequency band-stop performance is generated and we can control its characteristics such as band-notch frequency and its bandwidth. The designed antenna has a small size of 12×18 mm² while showing the band rejection performance in the frequency band of 5.08 to 5.91 GHz.

The angle-dependent properties of wave reflection in the lossy single-negative (SNG) materials are theoretically investigated. A model structure of SNG bilayer consisting of a lossy epsilon-negative (ENG) material and a lossy mu-negative (MNG) is considered in this work. The wave properties are investigated based on the calculated reflectance for the s wave (transversal electric wave) and the p wave (transversal magnetic wave) in addition to the degree of polarization. It is found that the angle-dependent reflectance of p wave is larger than that of s wave, which is contrary to the usual material with both positive epsilon and positive mu. The effects of losses coming from the ENG and MNG materials are specifically explored and the roles played by their thicknesses are also numerically elucidated.

In this work, an analytic expression to define the effective plasma frequency of an one-dimensional periodic system containing alternating dielectric and metallic slabs is proposed. Such metallic elements are considered to have a Drude dielectric function. The effective plasma frequency is obtained as a simple average of the constitutive materials, and its cutoff frequency for the propagating modes is compared with band structure calculations. We also explore the role of absorption in the transparency frequency cutoff.

This paper proposes a multilevel Green's function interpolation method (MLGFIM) to solve electromagnetic scattering from objects comprising both conductor and bi-isotropic objects using volume/surface integral equation (VSIE). Based on equivalence principle, the volume integral equation (VIE) in terms of volume electric and magnetic flux densities and surface integral equation (SIE) in terms of surface electric current density are first formulated for inhomogeneous bi-isotropic and conducting objects, respectively, and then are discretized using the method of moments (MoM). The MLGFIM is adopted to speed up the iterative solution of the resultant equation and reduces the memory requirement. Numerical examples are presented to show good accuracy and versatility of the proposed algorithm in dealing with a wide array of scattering problems.

Born approximation is widely used in (inverse) scattering problems to alleviate the computational di±culty, but its validity and applicability are not well defined. In this paper, a universal criterion to identify the validity of Born approximation is put forward based on applying the operator theory on the scattering integral equation. In comparison with the traditional criteria, the new one excels in its ability to give a wider and more rigorous valid frequency range, especially while non-uniform scatterers are under consideration. Numerical examples verify the validity and advantage of the new criterion.

This paper presents the design, fabrication and measurement of a dual band switchable metamaterial electromagnetic absorber. The unit cell of the metamaterial consists of dipole mode electric resonators coupled by microwave diodes on one side of a dielectric substrate and metallic ground plane on the other side. Simulation and measurement results show that by forward or reverse biasing the diodes so as to change the coupling between the resonators, the absorber can be dynamically switched to operate in two adjacent frequency bands with nearly perfect peak absorption. Field distribution reveals the physical origin of the switchable performance based on the dipole mode of the electric resonator in the unit cell. It is also demonstrated that the frequency difference between the two bands can be tuned by adjusting the loading positions of the diodes with unchanged high absorption, which helps to design absorbers with specific switchable working frequencies in practical applications.

A wide open slot antenna with a pair of symmetrical L-strips for dual-band WLAN applications is proposed in this paper. A T-shaped monopole is used to cover 5.15~5.825 GHz. To achieve dual-band characteristic, a pair of symmetrical L-strips is embedded in the wide open U-slot to generate another band covering 2.4~2.48 GHz. The two bands are relatively independent from each other. The proposed antenna has the advantages of simple structure and excellent performance on the WLAN 2.4/5.2/5.8 GHz bands. The measured results of the fabricated antenna show that the impedance bandwidths are 150 MHz from 2.37 to 2.52 GHz and 1270 MHz from 4.83 to 6.10 GHz, which cover all the desired operating bands. Furthermore, the antenna design and some significant parametric studies are also described in detail.

Vibrations and noise in electrical machines are directly related to the characteristics of the radial forces on one hand, and mechanical behavior on the other. The characteristics of these forces depend on the air gap flux density, and they are influenced by other factors such as stator slots and poles, saturation level, winding type and certain faults. The aim of this work is to investigate the effect of eccentricity faults on electromagnetic noise generated by the external surface of PM synchronous machine (PMSM). For this purpose an analytical electromagnetic vibroacoustic model is developed. The results confirm the effect of eccentricity fault in generating some low modes radial forces. An experimental device is installed to validate the results of the analytical model.

The 2×2 MMI polymer thermo-optic switch in a high refractive index contrast (0.102) with a new structure design is realized. This device was fabricated using standard fabrication techniques such as coating, photolithography, and dry etching. A crosstalk level of -36.2 dB has been achieved. Meanwhile the extinction ratio of 36.1 dB has been achieved in this device. The polarization dependent loss (PDL) of 0.3 dB and Insertion loss of 1.4 dB were measured at 1550 nm wavelength. In terms of wavelength dependency, the device shows a good performance within C-band wavelength with vacillation of the insertion loss value around 0.88 dB. The power consumption of 1.85 mW was measured to change the state of the switch from the cross to bar state. The measured switching time was 0.7 ms.

A finite length cylindrical FSS is proposed as a spatial filter for both transmitting and receiving antennas. This filter has the advantage of not perturbing the omnidirectional property of the enclosed antenna. The proposed surface is constructed up as cylindrical array of rectangular conducting patches. The strips are arranged periodically in the φ- and z-directions. The electric field integral equation (EFIE) approach is used for analyzing the characteristics of the proposed spatial filter. The Rao-Wilton-Glisson (RWG) basis functions are used for current expansion on the conducting strips. The mutual effects between the filter and the antenna can be accurately investigated. The effects of some dimensional parameters on the filter characteristics, such as, the axial and angular spacing between the array elements, the length and the radius of the cylindrical surface are studied over a wide frequency range. The oblique incidence of plane waves on such a cylindrical filter is studied with varying the direction of incidence. The performance of the proposed spatial filter is examined when operating with nearby antennas. The effects of such a filter on the input impedance, VSWR, and radiation pattern of an enclosed bowtie antenna are investigated over a wide frequency range.

Breast imaging using Confocal Microwave Imaging (CMI) has becoming a difficult problem, primarily due to the recently-established dielectric heterogeneity of normal breast tissue. CMI for breast cancer detection was originally developed based on several assumptions regarding the dielectric properties of normal and cancerous breast tissue. Historical studies which examined the dielectric properties of breast tissue concluded that the breast was primarily dielectrically homogeneous, and that and that the propagation, attenuation and phase characteristics of normal breast tissue allowed for the constructive addition of the Ultra Wideband (UWB) returns from dielectric scatterers within the breast. However, recent studies by Lazebnik et al. have highlighted a very significant dielectric contrast between normal adipose and broglandular tissue within the breast. Lazebnik also established that there was an almost negligible dielectric contrast between broglandular and cancerous breast tissue at microwave frequencies. This dielectric heterogeneity presents a considerably more challenging imaging scenario, where constructive addition of the UWB returns, and therefore tumor detection, is much more difficult. Therefore, more sophisticated signal acquisition and beamforming algorithms need to be developed. In this paper, a novel imaging algorithm is described, which uses a rotating antenna system to increase the number of unique propagation paths to and from the tumor to create an improved image of the breast. This approach is shown to provide improved images of more dielectrically heterogeneous breasts than the traditional fixed-antenna delay and sum beamformer from which it is derived.

In this paper, a new ultra wideband circular antenna array (UCAA) combining particle swarm optimizer (PSO) to minimize the bit error rate (BER) is proposed. The ultra wideband (UWB) impulse responses of the indoor channel for any transmitter-receiver location are computed by applying shooting and bouncing ray/image (SBR/Image) techniques, inverse fast Fourier transform and Hermitian processing. By using the impulse response of multipath channel, the BER performance of the binary pulse amplitude modulation (B-PAM) impulse radio (IR) UWB system can be calculated. Based on the topography of the circular antenna array, and the BER formula, the array pattern synthesis problem can be reformulated into an optimization problem and solved by the PSO. The novelties of our approach is not only choosing BER as the object function instead of sidelobe level of the antenna pattern, but also consider the antenna feed length effect of each array element. The strong point of the PSO is that it can find out the solution even if the performance index cannot be formulated by simple equations. Simulation results show that the synthesized antenna array pattern is effective to focus maximum gain to the LOS path which scales as the number of array elements. In other words, the receiver can increase the received signal energy to noise ratio. The synthesized array pattern also can mitigate severe multipath fading in complex propagation environment. As a result, the BER can be reduced substantially in indoor UWB communication system.

This paper presents a GPU-based multiresolution shooting and bouncing ray (MSBR) method with the kd-tree acceleration structure for the fast radar cross section (RCS) prediction of electrically large and complex targets. The multiresolution grid algorithm can greatly reduce the total number of ray tubes, as it adaptively adjusts the density of ray tubes for regions with different complexities of their structures, while the kd-tree acceleration structure can highly decrease the number of ray-patch intersection tests. The multiresolution grid technique and kd-tree traversal algorithm are fully implemented on the GPU to further accelerate the SBR by exploiting the massively parallel computing ability. Numerical experiments demonstrate that the proposed GPU-based MSBR can significantly improve the computational efficiency. It is about 40 times faster than the CPU MSBR, and at least 4.8 times faster than the GPU-based SBR without the multiresolution grid algorithm.

An ultra wide band (UWB) band-pass filter (BPF) utilizing one modified composite-right/lefthanded (CRLH) unit cell is proposed. By introducing the capacitive cross coupling to the traditional CRLH structure, the phase shift in the right-handed pass-band can be controlled, meanwhile, the cross coupling has negligible effect on the left-handed pass-band. The appropriate cross coupling can create three controllable transmission zeros. Thus, an UWB BPF with high selectivity is developed using only one unit cell, which leads to low insertion loss (less than 1.35 dB) and compact size (0.47λ₀×0.28λ₀). The fabricated filter exhibits a rejection level higher than 20 dB at the stop-band from 11.95--16 GHz and flat group delay across the pass-band.

A toroidal field coil (TFC) is composed of several individual toroidal coils (ITCs), which are connected in a series and distributed in a toroidal and symmetrical form. Cross section of ITCs is rectangular or negligible. This paper presents analytical equations for mutual inductance of two ITCs applicable to Tokamak reactors using the filament method. These equations are based on those formulated by Neumann. The numerical analysis of the integrations resulting from these equations is solved using the extended three-point Gaussian algorithm. The finite element method (FEM) is employed to verify the mutual inductance equations of ITCs. The results obtained using the FEM, when dimensional parameters of ITCs are changed, confirm the analytical and empirical results showing an error of less than 0.2043% in the worst case. This indicates the reliability of the presented equations.

This paper presents a D-band power amplifier for high-speed communication system. The capacitive effect of interconnection via on transistor performance at high frequency is analyzed and a new via structure is employed to reduce the capacitive effect. The on-chip matching technique for high frequency amplifier is analyzed and the thin-film microstrip line matching network is used, which is combined with biasing network to reduce RF signal loss and silicon cost. The amplifier is fabricated in 0.13-μm SiGe BiCMOS process. The experimental results show a 7 dB gain at 130 GHz with 3-dB bandwidth of 30-GHz. The input return loss is better than 10 dB over 23 GHz. In addition, this amplifier achieves saturated output power (P_sat) of 4.5 dBm and input 1-dB gain compression point (P_1dB) of -4.5 dBm. The chip size of implemented power amplifier is only 0.22mm².

A thin Artificial Magnetic Conductor (AMC) structure for Radar Cross-Section (RCS) reduction applications is presented. The manufactured prototype, which combines two unit-cell metallization sizes, presenting two resonant frequencies, shows broad AMC operation bandwidth, polarization angle independency, and its angular margin when operating under oblique ncidence is also tested. It is shown that significant RCS reduction can be achieved with the proposed AMCs combination even if a 180º phaseshift between reflected waves is not met. Two designs are considered: the already mentioned design combining AMCs with overlapped frequency bands and the second one combining Perfect Electric Conductor (PEC) and AMC surfaces. A comparison between these two designs regarding RCS reduction, supported by measurements in an anechoic chamber, is presented.

Based on the active coupled line concept, a novel approach for efficient noise performance modeling of millimeter-wave field-effect transistors is proposed. This distributed model considers the effect of wave propagation along the device electrodes, which can significantly affect the noise performance especially in the millimeter-wave range. By solving the multi-conductor transmission line equations, using the Finite-Difference Time-Domain technique, this procedure can accurately determine the noise correlation matrix of the transistor and then its noise performance.

A novel compact fork-shaped ultrawideband (UWB) antenna with triple band-notched characteristics is proposed. By embedding a spade-shaped slot on the radiating patch as well as adding a separated strip and a C-shaped resonating structure on the front side of the reference UWB antenna, the triple notched frequency bands are realized. The measured impedance bandwidth defined by VSWR<2 of 7.8 GHz (3--10.8 GHz), with the triple notched bands of 3.3--3.7 GHz, 5.15--5.4 GHz, and 5.7--5.9 GHz, are obtained. The proposed antenna with an overall dimension of only 24×30 mm² is successfully simulated, designed and measured, showing broadband matched impedance and stable radiation patterns.

A novel Yagi-Uda antenna with dual-band (915-935MHz and 1760-1805MHz) is presented. Branch structures are used to realize dual-band performance. The geometrical parameters for the branch structures are optimized to explore the antenna to operate satisfactorily in the two bands. Prototype is manufactured and measured, and the results are in good agreement with the simulated ones. In the two operating bands, the proposed antenna achieves directional radiation and the performances that VSWR<2, gain 5-6.6 dBi and front-to-back ratio 6-9.1dB, making it suitable for the non-fixed base station backhaul in wireless communications.