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.

In this article，a printed ultra-wideband (UWB) monopole antenna with dual band-notched characteristics of size 26 mm×35 mm is presented. The prototype consists of pincers-shaped radiation element and corner rounded ground plane. By inserting a pair of flexuous slots on the radiation element and a C-shaped slot on the ground plane, the 3.5/5.5 GHz dual band-notched characteristics are achieved, respectively. Moreover, good radiation patterns and gains within the operating band have been obtained. The detailed design and experimental results are discussed in this article.

A large bandwidth wide-slot antenna, fed by coplanar waveguide (CPW), is proposed. Experimental investigations and detailed simulations are conducted to understand its behavior and to optimize for broadband operation. The impedance bandwidth, determined by 10-dB return loss of the proposed slot antenna using both measurement and simulation, is about 131% (2.8 to 14 GHz). In addition to be small in size, the antenna has low cross polarization, relatively high gain, and it exhibits stable far-field radiation characteristics in the entire operating bandwidth. The design with very wide operating bandwidth and improved radiation pattern is obtained by properly choosing the suitable slot shape, selecting similar feed patch shape, and tuning their dimensions. Numerical sensitivity analysis has been used to understand the effects of changes of various antenna dimensions and to optimize the performance of the designed antenna. Based on our computer simulations it is shown that the antenna dimensions parameters have uncorrelated effects on the upper edge of the bandwidth. Simulation results show that the impedance matching of this kind of antenna is sensitive to the feed-slot combination and feed gap width. The simulated and measured results for return loss, far-field E-plane and H-plane radiation patterns, and gain of the designed antenna are presented and discussed.

A new defected ground structure (DGS) is firstly proposed in this paper, which has better slow-wave effect than that of cross or dumbbell one. Using the model of transmission line, its equivalent parameters are extracted. With good omni-directional properties, the proposed DGS is then used in the design of a proximity coupled antenna for its miniaturization. The size of the developed antenna is about 68% smaller than that of the conventional one. Further, two artificial cells are added on the feed line to reduce the protrudent stub length from 26.9mm to 18.94 mm. With the utility of the DGS and artificial cells, the size of proximity coupled antenna is reduced significantly. By introducing a PIN diode at the end of feed line, the antenna is switchable in both x- and y-direction linear polarizations. Such miniaturization in antenna size has little negative effect on its cross polarization, with both simulated and experimental results presented for comparison.

In this paper, a stacked ring-patch two layer planar artificial substrate is analyzed numerically and is shown to possess the properties of a high impedance surfaces (HIS). Its properties are evaluated by investigating the surface wave propagation and plane wave reflection characteristics. Its application to reduce the mutual coupling of microstrip antennas and to improve the radiation pattern are investigated by simulation tool CST microwave studio. Experimental measurements using a pair of monopoles are used to confirm the surface waves suppression band. One of the main advantages of the proposed geometry is that it is simple and planar in nature, without the need for any via connections across dielectric layers and thus can be realized by planar technologies. Another advantage is that it exhibits over lapped surface wave suppression and in-phase reflection bands. Also it can be scalable to operate in different frequency range.

This paper presents a novel method of cavity filter tuning with the usage of an artificial neural network (ANN). The proposed method does not require information on the filter topology, and the filter is treated as a black box. In order to illustrate the concept, a feed-forward, multi-layer, non-linear artificial neural network with back propagation is applied. The method for preparing, learning and testing vectors consisting of sampled detuned scattering characteristics and corresponding tuning screw deviations is proposed. To collect the training vectors, the machine, an intelligent automatic filter tuning tool integrated with a vector network analyzer, has been built. The ANN was trained on the basis of samples obtained from a properly tuned filter. It has been proved that the usage of multidimensional approximation ability of an ANN makes it possible to map the characteristic of a detuned filter reflection in individual screw errors. Finally, after the ANN learning process, the tuning experiment on 6 and 11-cavity filters has been preformed, proving a very high efficiency of the presented method.

In this paper, we presented the design of a high performance diplexer for applications of global positioning system (GPS) at 1.575 GHz and wireless local area network (WLAN) at 2.4 GHz, simultaneously. Two bandpass filters (BPFs) using the modified stepped-impedance resonators (SIRs) operated at 1.575 GHz and 2.4 GHz are main blocks for the proposed diplexer. By discussing and analyzing the admittance of the even and odd modes, the transmission zero of the modified SIR can be found, and the location of the transmission zero can be precisely predicted, thus having a wide and deep stopband for the BPFs, in turn the high performance diplexer. Furthermore, due to the appearance of the transmission zeros near the passband edges, the passband selectivity of the BPFs as well as the diplexer can be improved. By using the impedance matching between two BPFs, a high isolation of 50 dB between two channels is obtained. The proposed diplexer was designed, fabricated and measured. The simulated and measured results had a good agreement with the proposed design concept.

A compact balanced frequency MMIC doubler using compensated capacitive line in Marchand balun is proposed. With multi-coupled lines technology, the balun is applied to a balanced doubler successfully. Compared with the conventional Marchand balun, more than 55% reduction in the length of coupled line can be achieved. Implemented by a PHEMT process, the compact monolithic balanced frequency doubler with better performance can be obtained. An operation bandwidth from 20 to 44 GHz with the best conversion loss of 8.4 dB at 25GHz can be achieved. In addition, the fundamental frequency suppression is better than 28.9 dB, and the chip dimension is as small as 0.41 × 0.68 mm².

A novel compact Epsilon Near Zero (ENZ) tunneling circuit with microstrip coupling for high integrability applications is presented. Full design procedure, simulation and experimental results are shown, and a methodology to extract the effective permittivity and propagation constants in the tunnel is described. Detailed analysis of the dependence on external quality factor and tunnel to feed height ratio is investigated. Simulation and measurement results of the ENZ tunnel structure are in good agreement.

This paper presents an extension over a novel, three dimensional high frequency method for the calculation of the scattered electromagnetic (EM) field from a Perfect Electric Conductor (PEC) plate, which is based on the Physical Optics (PO) approximation and the Stationary Phase Method (SPM). This extension defines a new analytical method which is proved to be very efficient in computer execution time and enhances the accuracy of its predecessor around the area of the main scattering lobe. This new analytical method accomplishes high accuracy through the use of higher order approximation terms, which imply the use of Fresnel functions (SPM-F method). By using higher order Fresnel approximation terms, no impact on the time efficiency of the SPM method appears to occur, since the extended SPM-F method just removes the troublesome vanishing denominators when the stationary point coincides with the edges of the scatterer. The SPM-F results are compared to other straightforward numerical and exact solution methods for the same problem in the far field, Fresnel zone and the near field area of the scatterer.

This paper proposes a new electronic-continuously variable transmission (E-CVT) system for power-split hybrid electric vehicles (HEVs). The key is to integrate two permanent magnet motor/generators (M/Gs) together with a coaxial magnetic gear (CMG). By designing the modulating ring of the CMG to be rotatable, this integrated machine can achieve both power splitting and mixing, and therefore, can seamlessly match the vehicle road load to the engine optimal operating region. With the one-side-in and one-side-out structure and the non-contact transmission of the CMG, all the drawbacks aroused by the mechanical gears and chain existing in the traditional E-CVT system can be overcome. Moreover, the proposed E-CVT system possesses the merits of small size and light weight, which are vitally important for extending the full-electric drive range of HEVs. The working principle and the design details are elaborated. By using the finite element method (FEM), the electromagnetic characteristics are analyzed.

Using magnetic composite material as the substrate for RFID metal tag has several advantages over conventional metal tags, such as flexibility and miniaturized size. In this paper, the radiation intensity contributed by a half-wave dipole is derived based on the result of an ideal Hertzian dipole, which leads to a simple relation for thin substrate. Later on, the material constants of two materials are measured and the one capable of generating greater radiation intensity is used in the course of antenna design. A primitive pattern design demonstrates the metal tag has a satisfactory 2.7 m reading range, and a dimension of 80×22×2 mm³.

A compact microstrip-line-fed antenna designed by inserting two pairs of strips into a rectangular slot for achieving triple-band operation is proposed. The antenna, which occupies a small size of only 40×32×1.6 mm³, utilizes inserted strips to generate dual band-notched characteristics so that three operating bands are able to be achieved, which range from 2.2 to 2.7, 3.07 to 3.86, and 5.13 to 6.23 GHz, sufficiently covering both the 2.4/5.2/5.8 GHz WLAN and 2.5/3.5/5.5 GHz WiMAX bands. In addition, the measured results show good monopole-like radiation patterns and stable antenna gains across the three operating bands.