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.

In this paper, a novel circular slot UWB antenna with dual notched frequency band is presented and investigated. A C-shaped slot is inserted into the fed element, and a parasitic strip is printed in the circular slot, so that the proposed antenna achieves dual band-notched characteristics, respectively. The measured and simulated results show that the proposed antenna meets the requirement of wide working bandwidth of 3.1-10.6 GHz with VSWR < 2, while avoiding the interference with the 3.5 GHz WiMAX and 5.5 GHz WLAN band. Study of transfer function (amplitude of S₂₁/group delay) and time domain characteristic (radiated pulses/power spectrum density (PSD)) correspond well with the VSWR, which indicate the dual band notched characteristic of the antenna.

This paper presents study of controllable leaky wave modes in various planar transmission lines operating at millimetre wavelengths. Leaky wave regime is achieved by exploitation of periodic inclusions. The main goal is to obtain the scanning of the radiation angle from forward to backward direction and rather broad range of scanning angles at a given operation frequency corresponding to the mm-wave range. For this purpose we suggest to use MEMS capacitors combined with shunt strap inductors, probably grounded. This design solution allows one to significantly reduce the losses in the loaded line compared to known scanning leaky-wave antennas based on varactors or on magnetized ferrites. The design of the unit cell is done using global optimization method, and the dispersion is investigated analytically. After analytical modeling and optimization, full wave analysis is done using Ansoft HFSS v.11 environment. After the leaky wave regimes are verified, an example of a leaky-wave antenna is introduced in order to confirm possibility of beam scanning.

A non-resonant microwave method has been proposed for accurate complex permittivity determination of low-loss materials. The method uses two measurement data of the magnitude of transmission properties of the sample. While the first datum must correspond to a frequency point resulting in a maximum magnitude of transmission properties, the other can be any datum at a frequency different than the first datum and not far distant from the first datum. Two closed-from expressions are derived for a good initial guess using the above data. The limitations of each expression are discussed. The method has been validated by transmission measurements at X-band (8.2-12.4 GHz) of a low-loss sample located into a waveguide sample holder.

A compact microstrip bandpass filter (BPF) with multispurious suppression is presented. The filter consists of two coupled half-wavelength stepped impedance resonators (SIRs) and tapped input/output (I/O) lines. With tuning the impedance ratio (K) and length ratio (α) of SIRs, a very wide stopband can be easily achieved. The filter is designed at 2.4 GHz (f₀) with a wide stopband to 20 GHz (8.16f₀) and an average rejection level better than 25 dB. This study provides a simple and effective method to achieve a filter with very wide stopband and compact circuit size simultaneously. Good agreement between the full-wave electromagnetic (EM) simulation and measurement is compared.

In this paper, extending the design technique presented by the authors in a previous work, we propose the study of a new family of polygonal patch antennas for portable devices of communication systems. Such antennas are suitable to be mounted in modern terminals, enabling wideband/multi-frequency operation and new multimedia features. The desired electromagnetic behaviour of the proposed radiators is obtained by adding either shorting posts, properly located between the polygonal patch and the ground plane, or circular slots, drilled at the appropriate position on the patch surface. Circular slots are also useful to easily accommodate a photo-camera in the terminal, in order to enable multimedia services and video calls. Some practical layouts of polygonal patch antennas to be used in: a) modern PDAs and Smart Phones integrating cellular phone operation and wireless functionalities; b) UMTS terminals integrating also GSM functionalities, are, finally, presented. The effectiveness of the proposed designs is confirmed through proper full-wave numerical simulations.

A novel type of wideband SICC filter using TM₀₁ mode coupling by the circular hole between the SICCs is proposed. Of circular symmetry, the TM₀₁ mode in SICC demonstrates the advantages of compact and high flexibility of the filter's input and output setting. In order to validate the new proposed topology, three filter prototypes with different included angle between input and output have been designed and manufactured. The filters exhibit a low insertion loss of -1 dB in the 12.8 to 20 GHz, a wide relative bandwidth of 54.5% at -3 dB, high flexibility and very good agreement with simulation data.

In this paper a new method is proposed to achieve a temperature insensitive, broad and flat gain C-band erbium-doped fiber amplifier (EDFA) with aid of macro-bending. This gain flattened C-band EDFA is demonstrated by utilizing 2.5 m macro-bent Erbium-doped fiber (EDF) at room temperature of 25℃. Further to this, it is shown that gain fluctuation at different temperatures is compensated in the proposed design. The EDFA performance at different temperatures is investigated for various macro-bending diameter and EDF length. The gain saturation and energy transfer from shorter wavelengths to longer wavelengths can be controlled by varying the bending radius and the length of the doped fiber, consequently, a flattened and broadened gain profile in the C-band region can be achieved. The amplifier uses a 2.5 m long EDF with 2000 ppm concentration and bending radius of 6.5 mm as a gain medium. The gain variation of the EDFA is obtained within ±0.5 dB over 35 nm bandwidth of C-band region.

Explicit Green's tensors for the diffusive electric field in a configuration with two homogeneous half spaces are of interest for primary-secondary formulations of frequency domain and time domain modeling schemes. We derive the explicit expressions for the Green tensor of the electric field generated by an electric dipole in space frequency and space time. Both source and receiver can have arbitrary positions in the vertical transverse isotropic (VTI) half space below a non conductive half space. Apart from their use in modeling schemes, the expressions can be used to understand the effect of the interface between the VTI and the non conducting half space. We show that the TE-mode refracts against the interface, and its effect in the VTI half space decays exponentially as a function of depth and is inversely proportional to horizontal distance cubed for horizontal source receiver distances larger than three times the source depth. In exploration geophysics, this part of the field is known as the "airwave". The contribution from the "airwave" has a late time behavior that differs from the other contributions to the electric field. This makes time domain systems relevant for exploration geophysical applications.

The small-scale fading behavior in common wireless communication systems can be predicted by a series of propagation models. Although these types of models are feasible and effective for the situations of transmitting/receiving (Tx/Rx) antennas in relatively open surrounding environments, they are unable to address the coupling between the antenna and environment. In order to overcome this difficulty, a full-wave numerical method is applied in terms of the advantage in considering the interaction between complicated environments and the Tx/Rx antennas, and it can take into account the effect of the interaction on signals. In this paper, an integrative modeling technique involving FDTD method, two-path propagation model and multi-path statistical distribution model is presented, which combines the deterministic and statistical methods. For achieving reliable communication especially in high-speed railway environment, high sampling rate and adequate sampling points are needed for analyzing the propagation properties of the radio frequency (RF) link. This can be easily achieved by the integrative modeling technique, and the output voltage and current of train antenna under the illumination of base-station (BS) antenna along the railway can be given in detail. Results obtained from the integrative simulation for three different multi-path statistical distribution models are presented and analyzed.

An inverse equivalent surface current method working with equivalent electric and/or magnetic surface current densities on appropriately chosen Huygens surfaces is investigated. The considered model with triangular surface meshes is compatible with the models known from method of moments (MoM) solutions of surface integral equations. Divergence conforming current basis functions of order 0.5 and of order 1.5 are considered, where the order 0.5 functions are the well-known Rao-Wilton-Glisson basis functions. Known near-field samples typically obtained from measurements are mapped on the unknown equivalent surface current densities utilizing the radiation integrals of the currents as forward operator, where the measurement probe influence is formulated in a MoM like weighting integral. The evaluation of the forward operator is accelerated by adaptation of the multilevel fast multipole method (MLFMM) to the inverse formulation, where the MLFMM representation is the key to full probe correction by employing only the far-field patterns of the measurement probe antennas. The resulting fully probe corrected algorithm is very flexible and efficient, where it is found that the computation speed is mostly dependent on the MLFMM configuration of the problem and not that much on the particular equivalent current expansion as long as the expansion is able to represent the currents sufficiently well. Inverse current and far-field pattern results are shown for a variety of problems, where near-field samples obtained from simulations as well as from realistic measurements are considered.

Omni-directional antennas are useful for variety of wireless communication devices as well as capable of handling the additional different frequency bands since the radiation pattern allows good transmission and reception from a mobile unit. However, to implement the two frequencies on a single antenna with wide bandwidth can be significant because of the presence of mutual coupling and interference effects between the two radiating elements. In this paper, a novel method of combining dual-band frequencies onto a single layer board with wide bandwidth is described. A dual-band printed dipole antenna is designed in this study by combining a rectangular and two "L" shaped radiating elements and are embedded on a single layer structure with relatively small size. The obtained results show that the proposed dual-band omni-directional microstrip antenna achieves high antenna efficiency and provides better bandwidth while maintaining the structural compact size.