A novel complex structure of Printed Dielectric Resonator Monopole Antenna (PDRMA) with multi-bands operation is presented and investigated. In the proposed structure, a printed fork-like stepped monopole antenna is used for exciting two new modified hemi-cylindrical dielectric resonators with a great relative permittivity of 80. A narrow medium substrate with a low permittivity is also applied between two mentioned dielectric resonators and the monopole antenna, to improve the matching, especially at the lower frequencies. By using this novel designed antenna applying two dielectric resonators with very high permittivity, many frequency wide bands for VSWR < 2 are practically measured and supported which are as follows: 1.54--3.25 GHz (GPS, GSM, PCS, UMTS 2000, 2.4 GHz-Bluetooth, WLAN, WiMax), 3.3--3.6 GHz (WiMax), 3.8--4.4 GHz (C-band), 4.8--6.2 GHz (5.2, 5.5 & 5.8 GHz-WLAN & WiMax). Experimental and numerical results are carried out and discussed, showing good agreement.

A bidirectional directly modulated cable passive optical network (PON) based on a reflective semiconductor optical amplifier (RSOA) as a colorless modulator in the optical network unit (ONU) is proposed and demonstrated. Good performances of downstream carrier-to-noise ratio (CNR)/composite second-order (CSO)/composite triple beat (CTB) and upstream bit error rate (BER) were achieved over a 40-km single-mode fiber (SMF) transmission. This proposed directly modulated cable PON is simpler and cost lower than the externally modulated one.

Resonant modes of multi-layer structures which contain the regions of negative epsilon material (such as a metal in the visible range) are analyzed. Existence of two separate classes of resonant modes is demonstrated. One is related to the excitation of the surface mode at the interface of the regions with opposite signs of the dielectric constant and involve energy transport by evanescent modes throughout the whole structure. The second class involves propagating modes (which form the resonant standing wave) in some regions and the evanescent waves in other layers with ε＜0. It is shown that the resonant transmission is related to the existence of quasi-stationary leaky modes having a finite life-time and characterized by large wave amplitude in the trapping region. It is shown that both types of resonances can coexist in multi-layer structures. It is also shown that the interaction of the symmetric and anti-symmetric surface eigen-modes widens the resonant transmission region.

In this article, a time-domain calibration procedure is proposed for pulsed Terahertz Integrated Circuits (TIC) used in on-chip applications, where the conventional calibration methods are not applicable. The proposed post-detection method removes the unwanted linear distortions, such as interfering echoes and frequency dispersion, by using only one single-port measurement. The method employs a wave-transfer model for analysis of the TIC, and the model parameters are obtained by a proposed blind estimation algorithm. A complete implementation of the method is demonstrated for a fabricated TIC, when used in an on-chip sensing application. The features of interest in the measured signal, such as absorption lines, can be masked or weakened by the distortion of the THz signal happening in a TIC. The proposed signal recovery approach improves the detection of those otherwise hidden features, and can significantly enhance the performance of existing TICs. To show the effectiveness of the proposed de-embedding method, numerical results are presented for simulated and measured signals. The method presented in this article is enabling for accurate TIC applications, and can be utilized to optimally design novel TIC structures for specific purposes.

Planar waveguides with an isotropic chiral core, called chirowaveguides, support the propagation of elliptically polarized modes, making them natural candidates for chiral sensing. We investigate the potential of chirowaveguides as optical sensors responding to changes in the circular birefringence of a medium covering the waveguide. Using first order approximations, we derive expressions for the sensitivities to refractive index and to changes in circular birefringence. The chiral sensitivity is proportional to the achiral sensitivity and to the eccentricity of the mode under consideration. Possible combinations of materials and design conditions for chirowaveguide sensors are discussed with reference to these results. The motivation for this study, besides its theoretical and academic importance, comes from potential applications for enantiomeric integrated optical devices.

The aim of this paper is to discuss the effects of the exposure to Extremely Low Frequency ElectroMagnetic Fields (ELF-EMFs) on non- and excitable cells using in vitro cell models, namely neuron-like cell line (PC12), glioblastoma GL15 as glial model and C2C12 myocytes as muscle model, focusing our attention on standardized protocols for ELF-EMFs generation and exposure. A major issue in laboratory -and likely in natura- studies about possible biological effects of ELF waves is the difficulty in providing standard, reproducible environmental conditions. Hence, as part of the work we have developed an exposure system including a probing scanner, able to sample a given volume and to measure the time-varying magnetic field vector. The system allows detection, monitoring and removal of electromagnetic noise sources, as well as means to assess field homogeneity in terms of intensity and polarization.

The paper presents integrated probe for direct coupling to the WR-10 waveguide with the use of metal filled vias on both sides of the microstrip line. Design and optimization of this novel microstrip-to-waveguide transition has been performed using 3-D finite element method based software HFSS (High Frequency Structure Simulator). A back-to-back transition has been fabricated and measured between 75--110 GHz. The measured return loss is higher than 10 dB and the insertion loss for a single microstrip-to-waveguide transition is about 1.15 dB.

A novel of wideband monopole antenna with UTM-Logo shape is proposed to create specific wide band frequencies which can be applied in the cognitive radio. The antenna is designed to be operated between 1.98 to 6.46 GHz frequency bands (106.16%). It has been fabricated on 30×51 mm² FR4 board with thickness of 1.6 mm and the dielectric permittivity and tangent loss of 4.7 and 0.019, respectively. Two slots also been attached on the ground plane for the purpose of increasing the bandwidth of antenna. Simulation and measurement results show good agreement.

This paper investigates the application of frequency-selective surface (FSS) in reflectarray antennas for the purpose of reducing radar cross section (RCS) level. Different from previous reports, the presented band-stop FSS structure is also characterized by the suppression of surface waves, which makes a contribution to better radiation performance. Two 14 x 14 reflectarray antennas backed on the FSS ground and a solid ground are designed and fabricated. Simulated and measured results show that the FSS ground can improve the `in- band' gain by 1.1 dB, decrease the sidelobe level by 6.4 dB, and reduce the `out-of-band' RCS effectively when compared with the antenna with a solid ground plane of the same size.

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.