Multilayered structures consisting of alternating negative-permittivity and dielectric layers are explored to obtain high-resolution imaging of subwavelength objects. The peaks with the smallest |k_y| (k_y is the transverse wave vector) on the transmission curves, which come from the guided modes of the multilayered structures, can not be completely damped by material loss. This makes the amplitudes of the evanescent waves around these peaks inappropriate after transmitted through the imaging structures, and the imaging quality is not good. To solve such a problem, the permittivity of the dielectric layers is appropriately chosen to make these sharp peaks merge with their neighboring peaks, whose corresponding guiding modes in the multilayered structure are cutoff. Wide flat upheavals are then generated on the transmission curves so that evanescent waves in a large range are transmitted through the structures with appropriate amplitudes. In addition, it is found that the sharp peaks with the smallest |k_y| can be eliminated by adding appropriate coating layers and wide flat upheavals can also be obtained.

This work presents a new technique that uses floating plate overlays to realize the open-loop resonator bandpass filter with characteristics of compact size and having four controllable transmission zeros to achieve the multispurious suppression. Three floating plate overlays are used to cover parts of the open-loop resonator filter to increase the coupling between resonators and move the transmission zeros to desired frequencies to enhance harmonic suppression. A design procedure that developed based on an equivalent circuit model of such a new type of filter is proposed. Two experimental prototypes are designed and fabricated to verify the proposed design method. The measured results agree well with the simulations. The measured insertion losses of the prototypes in passband are all less than 2 dB. One prototype is designed to suppress third, fourth, and fifth harmonics with the suppression greater than 30 dBc. Another prototype can suppress second, third, and fourth order harmonics below 20 dBc. In addition, prototype circuit areas are only about 50 percent of the conventional open-loop filter.

This paper investigates an H-fractal wideband microstrip filter with multi-passbands and a tuned notch band for wireless communication frequencies. The four different filter configurations explored are: symmetric with zero offset, symmetric with nonzero offset, asymmetric with zero offset, and asymmetric with nonzero offset. The effect of H-fractal iterations, fractal scaling parameters, and stub offset on the filter's multi-passband response is presented. A comparison is made to a non-fractal straight stub filter of equivalent length showing improved passband bandwidth while maintaining the same overall response. Then an asymmetry is introduced into the fractal geometry to produce a tuned notch band in the second passband. Two fractal scaling factors are shown to aid in the tuning of the filter notch band. Finally, an asymmetric filter is fabricated on FR-4 substrate and experimentally verified, illustrating that the filter has multi-passbands and can find applications in WiFi/WiMAX transponders. The fabricated filter's first two passbands (with respect to S₁₁ = -10 dB) are: from 2.09 GHz to 3.18 GHz (fractional bandwidth of 1.09 GHz, 41.36%) and from 4.1 GHz to 5.43 GHz (factional bandwidth of 1.33 GHz, 27.91%), both for WiFi applications along with a notch band (S₂₁ = -3 dB) from 3.3 GHz to 3.94 GHz (factional bandwidth of 0.64 GHz, 17.67%) to suppress co-site WiMAX transmission. The measured data agrees reasonably well with the simulated filter response.

A simplified extended composite right/left-handed (SE-CRLH) transmission line (TL) is proposed for dual-band applications. The dual-band bandpass behavior is realized with a simplified non-dual circuit with only two broadband balanced conditions. The dispersion relation and frequency response of SE-CRLH TL are analyzed by circuit analysis, Bloch-Floquet theorem, and full wave simulation. A demonstration of SE-CRLH structure is designed. The measurements are in agreement with simulations and theory.

In this paper, a new N-way multi-frequency unequal split Wilkinson power divider (WPD) is proposed. The dividers are composed of multi-section transmission line transformers (TLT) and isolation resistors, which provide high isolation and very good input/output ports matching simultaneously at arbitrary design frequencies. To verify the validity of the design, several multi-frequency power dividers are designed and simulated. Specifically, a 3-way unequal split dual-frequency WPD operating at 900 and 1800 MHz, a 3-way unequal split triple-frequency WPD operating at 1, 2, 3 GHz, and a 4-way equal split quad-frequency WPD operating at 1, 2, 3, 4 GHz, are designed.

Frequency shift of the spectrum of an incident optical pulse by an intense THz pulse inducing cross-phase modulation (XPM) in a nonlinear dielectric slab is analyzed. The effect is predicted with a high degree of accuracy using the well-known transmission line matrix (TLM) technique. In this research, to model the THzinduced temporal and spatial variation of the dielectric permittivity of the nonlinear dielectric slab, the transmission lines of the TLM method are loaded with open shunt stubs. The parameters of the stubs are modified in accordance with the refractive index variation of the dielectric slab, here ZnTe, induced by the strong THz pulse. The obtained numerical results are verified with a recently reported experimental work.

A recently presented equivalent conductor (EC) method enables fast computation for the radar cross section (RCS) of a chaff cloud. Despite its good performance, the EC method is restrictively applicable due to the complex orientation distribution of chaff and the incident angle. In this paper, a generalized equivalent conductor (GEC) method is presented for estimating the RCS of an actual chaff cloud. The proposed method can be applied to any orientation distribution of the chaff cloud by using a weight function and a weighted average, as well as to any incident angle by employing a method of moment (MoM). Numerical results are presented for three scenarios and validated with results of the MoM.

A new method is presented for analysis of transient electromagnetic fields in regular structures with abrupt discontinuities. The method is based on mode expansion of the fields in the Time Domain. The modes propagate independently in the regular parts of the structure and are coupled at the discontinuity. The main idea consists in solving 1D FDTD equations for each independent mode channel in the regular waveguides and using mode-matching at the junction cross-section in order to relate the mode amplitudes in all the channels at the same time instant via imposing boundary conditions. As examples the problems of pulse signal diffraction at a step discontinuity in a parallel-plate waveguide, diffraction at a junction of circular and coaxial waveguides, and pulse radiation of a bi-conical antenna are considered. The latter problem is treated as a junction of two conical lines (one of which is the free space) that are regular in spherical coordinates.

In this paper, a large number of studies of the effect of the foliage on single or lines of trees on modern wireless communication systems are reviewed. The paper is focused on the experimental works mainly done for commercial applications such as cellular communication and high speed point-to-point fixed link at the microwave and millimeter wave frequencies. For this review study, the development of the foliage loss prediction methods and the factors influencing the tree-induced shadowing effect are highlighted. In view of current research work in this area, some possible future works are proposed to improve the performance of modern wireless communication systems with the effect of foliage.

Adaptive Neuro-fuzzy systems constitute an intelligent systems hybrid technique that combines fuzzy logic with neural networks in order to have better results. A study is presented to forecast the relative magnetic permeability using ANFIS. The global electromagnetic parameter, namely, the magnetic induction has been used as input to estimate the relative magnetic permeability. In this exceptional research, finite element simulations are carried out to build up a database which will be used to train ANFIS network. The ANFIS approach learns the rules and membership functions from training data. The hybrid system is tested by the use of the validation data. Performance of the trained ANFIS network was compared with the multilayer feed forward network model and experimental results. The results show the effectiveness of the proposed approach in solving inverse electromagnetic problem.

In this paper a multifunctional microstrip antenna is designed, fabricated and experimentally verified for operation in AWS, GSM, WiMAX and WLAN bands. This microstrip patch antenna has two U-shaped slots to achieve the dual wideband operation required to meet these specifications. The dimensions and locations of the U-slots are designed appropriately. The thick substrate used here helps in integrating the antenna with the existing aircraft panel material while achieving wide bandwidths. Experimental results of this single feed antenna indicate that it meets all current requirements for in-cabin wireless communication needs.

A capacitive method for measuring hand grip position on a mobile phone equipped with a dual-band planar inverted-F antenna (PIFA) and a monopole antenna was studied using different electrode arrangements. A capacitive sensor with a dual-electrode configuration and an antenna-integrated capacitive sensor for hand grip recognition were developed. The sensitivities of the sensors were measured along the front, side and back of the phone. The dual-electrode sensor configuration exhibited its best sensitivity of 29 fF at the bottom end of the phone. The PIFA antenna-integrated sensor proved to have sensitivity of 420 fF and the monopole antenna-integrated sensor had sensitivity of 115 fF, making them both reasonable solutions for hand grip sensors in mobile applications.

Shielding prevents coupling of undesired radiated electro-magnetic energy into equipment otherwise susceptible to it. In view of this, some studies on shielding effectiveness of different shields against angle of incidence with conductors and conductive polymers using plane-wave theory are carried out in this paper. The plane wave shield- ing effectiveness of new combination of these materials is evaluated as a function of angle of incidence for Single, Double and Laminated Shields. Conductivity of the polymers, measured in previous investigations by the cavity perturbation technique, is used to compute the overall reflection and transmission coefficients of single and multiple layers of the polymers. With recent advancements in synthesizing stable highly conductive polymers, these light-weight mechanically strong materials appear to be viable alternatives to metals for EM1 shielding. The analysis is done at a particular frequency for all three types of shields.

A LOD-like method that characterizes the analytical solution is proposed to study the one-dimensional (1-D) chiral media. Through theoretical analysis and numerical simulation, it is found that the proposed scheme is unconditionally stable. This scheme employs the new mesh-dividing method for bi-isotropic media, in which the two sections on the right side of the rearranged curl equations are regarded as two directions and the LOD-like algorithm is used to deal with the equivalent two-dimensional (2-D) problem. In the first substep, the conventional LOD method is used in computation, while for the second substep, the analytical solution is employed instead. By simulating the polarization rotation of a mono-frequency linear polarized wave both in a 1-D homogeneous chiral media and through a chiral slab, the scheme is testified to be unconditionally stable.

The formation process of antenna mode scattering is analyzed, and a new prediction method to calculate the antenna mode scattering is proposed. Since the antenna mode scattering is essentially the reradiation of reflected energy, this reflected energy comes from the incident wave received by the antenna and reflects on the mismatched point of the feed network. Thus the calculation of the antenna mode scattering can be divided into three steps: 1. calculation of the antenna received energy; 2. calculation of the reflected energy from the feed network; 3. reradiation of this reflected energy. The numerical results of antenna mode scattering from a patch antenna and a dipole array are proposed to verify this approach.

A novel CPW-fed triple-band monopole antenna designed by embedding an S-shaped meander strip into a C-shaped strip is proposed for WLAN and WiMAX applications. The antenna with a very simple and compact structure is easy to be fabricated, and the prototype of the proposed antenna has been constructed and measured. The triple operating bands with 10-dB return-loss bandwidths of about 110 MHz centered at 2.45 GHz, 310 MHz centered at 3.55 GHz, and 39% ranging from 4.1 to 6.2 GHz, covering the required bandwidths of 2.4/5.2/5.8 GHz WLAN and 3.5/5.5 GHz WiMAX standards, are obtained. In addition, good radiation performance and antenna gain across the three frequency ranges have been obtained.

In this paper, a modified square monopole antenna with multi-resonance performance, for UWB applications is proposed. The proposed antenna consists of a square radiating patch with a pair of T-shaped slots and a ground plane with a pair of rectangular sleeve and a T-shaped resonator which provides a wide usable fractional bandwidth of more than 125% (3.05-13.57 GHz). By optimizing dimension of rectangular sleeves, T-shaped slots and resonator, the total bandwidth of the antenna is greatly improved. The designed antenna has a small size of 14×22 mm². Good return loss and radiation pattern characteristics are obtained in the frequency band of interest. Simulated and experimental results are presented to demonstrate the performance of a suggested antenna.

Shift-Operator Finite difference Time Domain (SO-FDTD) method is introduced as a new efficient technique for simulating electromagnetic wave interaction with chiral medium. The dispersive properties of this medium are presented as polynomials of jω. These polynomials are converted to time domain by replacing jω by the time derivative operator. Then this time derivative operator is converted to the corresponding time shift operator which is used directly to obtain the corresponding update equations of electric and magnetic field components. The resulting update equations do not require time convolution or additional vector components. The present analysis does not require also any transformation. Significant improvement is obtained in memory requirements by using this method while the computational time is nearly the same compared with other similar techniques like Z-transformation FDTD.

In the field of maritime surveillance, HF surface wave radars seem to be considered as an optimum and low cost solution. Nevertheless, the commonly used radiating elements of those radars are not yet able to only launch surface waves. We aim to design a specific radiating element optimized for exciting such waves. The first step of such an issue is to set thoroughly the problem. In this paper, surface waves on the boundary between two dielectric media are considered. Kistovich decomposition is applied in order to discuss the influence of the Zenneck wave on the field excited at the sea surface. It is shown that Zenneck approach and Norton's one are not contradictory. Above all, we point out that, using Kistovich decomposition to design radiating elements, we can expect a significant improvement of the surface wave intensity.

We extend our previously-derived generalized closed-form representation for spectral dispersing performance of the Virtually-Imaged-Phased-Array (VIPA) based on a 3D vectorial Gaussian beam formulation to demultiplexing application. To analyze VIPA in the demultiplexer scheme, a spherical lens is added after the VIPA, so that the device plane is superimposed on the focal plane of the lens. The calculated output profile at previous step is reformulated in a matrix form in this step. Finally, the derived closed-form is simulated, and the numerical outcomes are compared with the previous results. The 3D output radiation of VIPA demultiplexer pattern is also depicted and found to be very intuitive and promising for some applications especially WDM demultiplexer and optical Code Division Multiple Access (CDMA).