In this paper, an equivalent circuit model for special type of planer transmission lines with defected ground structures (DGS) is presented. This structure has multi stop bands in its frequency behaviour. The proposed circuit is very simple compared to the previously published works. It is considered as simplified form of the model found in [8]. Using sensitivity analysis on model [8], some circuit parameters can be omitted without significant influence on the response of the model. The modified model is easily extracted from the full-wave EM simulations. An excellent agreement is obtained between S-parameters of the simplified equivalent circuit and their counterpart of full wave EM simulators.

This paper proposes parallel-coupled stepped impedance resonators (SIRs) used for wideband bandpass filters with reduced size and improved spurious response suppression in out-of-band. The filter design concept is demonstrated by both two- and four-parallel coupled line resonator structures with the same fundamental frequency (f₀) of 6.5 GHz. The first bandpass filter has been designed using two resonators with λg/4 slot and embedded slot feeds for spurious response suppression at 2f₀ and 3f₀, respectively. The measured insertion loss is around 0.3 dB and the operation band is from 4.4 to 9.2 GHz (FBW = 73.8%). For the second bandpass filter, the embedded slot feeds and additional loaded open-stubs have been utilized to improve the wide spurious response suppression and sharp skirt characteristic in the passband. The measured passband of frequency response is from 4.2 to 8.6 GHz (FBW = 67.7%). The insertion loss of passband is lesser than 0.25 dB and the return loss is better than 15 dB. The filter designs are described in details. The simulated and experimental results are demonstrated and discussed.

An efficient numerical solution is been developed to compute the impedances of rectangular transmission lines. Method of moments is applied to integral equations for the current density, where the cross section is discretized, to improve the convergence, by a nonuniform grid that obeys the skin effect. Powerfulness of this approach up to rather high frequencies is verified by comparing with asymptotic formulas and other references. Detailed discussion is given for the current density distribution and its effect to the impedance, especially for a high frequency range.

We introduce an electromagnetic investigation of the complex experimental setup used in studying the Ratchet Effect at low We introduce an electromagnetic investigation of the complex experimental setup used in studying the Ratchet Effect at low temperature. This investigation, based on intensive electromagnetic simulations, shows that a compromise has to be taken into consideration between the physical aspects, the technological and the practical restrictions as well as the electromagnetic conditions of the observed phenomenon. By improving the electromagnetic response of the whole system, the Ratchet induced photovoltage can be increased, and hence the Ratchet device can be used for practical applications in wireless communications.

An ultra-wideband microwave imaging system that employs a heterogeneous breast phantom and covers the ultra-wideband (UWB) frequency range (3.1 GHz to 10.6 GHz) is presented. The platform scanning system allows monostatic and bistatic mode of operation. In this work, developed heterogeneous phantoms are used to mimic the realistic breast tissues. A utilized tapered slot antenna array allows for a high resolution hemispherical scan, achieved by rotating the imaged object on a turntable. Full design details of the scanning system and the utilized post-processing algorithm are explained. To validate the reliability of the presented system, the results of several imaging cases, including the challenging low dielectric contrast case, are presented.

The characteristics of guided modes in the circular waveguide consist of uniaxial chiral medium have been investigated. The characteristic equation of guided modes is derived. The dispersion curves and energy flux of guided modes for three kinds of uniaxial chiral media are presented. Unusual dispersion characteristics and negative energy flux are found, i.e., backward wave is supported in the uniaxial chiral waveguide.

A novel hydrostatic pressure sensor based on a gold-coated fiber modal interferometer (FMI) is proposed and demonstrated. Two single mode fibers (SMFs) are spliced with a lateral offset which forms a single-end FMI. The single-end FMI is gold-coated to enhance the reflectivity and to avoid the influence of any unwanted light from getting into the sensor. Relative reflection spectra of the proposed FMIs with different sensing SMF lengths or different lateral offsets are experimentally investigated. A high hydrostatic pressure sensor test system is proposed for the testing of the proposed FMI pressure sensor. The performance of a gold-coated FMI pressure sensor based on a 12-mm sensing SMF has been experimentally investigated. The proposed pressure sensor has a sensing range from 0 to 42 MPa and a sensitivity of 53 pm/MPa.

This study is designed mainly for dual band antennas of GSM/WiMAX operation in a wireless mobile communication device. This study proposes a matching technology for single path resonance in a basic monopole antenna running in dual-mode [1] and extends to a wide tuning range. The tuning of each frequency band is complicated under the constraint of the common path of dual-mode due to mutual interaction. This study proposes a refined process and new type of antennas for excellent dual-frequency matching. The incorporation of such a matching mechanism into a tuning monopole antenna enables the flexible operation bands. Moreover, the ground plane size can be shrunk to a reasonable size, and the details will be discussed in Section~6. As a result, antennas can achieve a tuning ratio of 1.6 (from 1825 to 2943 MHz). The total area of such a compact antenna including its ground can be effectively reduced to 0.018λ₀².

An integrated photonic True Time Delay phaser for phased array, based on an innovative technology, is here presented. The module versatility is showed by presenting more driving strategies matching different antenna features. The phaser insertion loss, the fluctuations of the excitation coefficients corresponding to the various driving configurations and the statistical modeling of the realization defects are also discussed.

The multi-frequency propagation in urban environment is investigated in this letter. An experimental measurement campaign is conducted to simultaneously measure the GSM-900, GSM-1800 and UMTS band of a cellular system in a suburban environment. The shadowing and small-scale fading parameters are extracted, and the correlation of these parameters across the different frequency bands is measured. It is shown that shadowing coefficients are highly correlated, while small-scale fading is completely uncorrelated between different frequency bands.

The lack of wave-plates for the terahertz region opens the way for novel components/devices enabling polarization control at these frequencies. With the aid of chiral metamaterials - a new class of metamaterials - novel possibilities for the fabrication of multilayer structures for the realization of polarization rotators emerge. In this study, we present design and analysis of a polarization rotator for the terahertz frequency regime based on a multilayer structure consisting of an alternating sequence of chiral-metamaterial- and dielectric-plates. The combination of chiral constituents with dielectrics permits optimization of the spectral-filter and polarization-rotation features. We can generate either polarization-rotation combs or narrow rotation bands with very good and broad sideband suppression, of interest for example for data transmission or sensing purposes.

The problem of direction-of-arrival (DOA) estimation by using spectral search for a non-uniform planar array is addressed. New search methods for DOA estimation based on piecewise interpolation are proposed. The relationships between these methods and Fourier-Domain (FD) root-MUSIC are discussed. The proposed methods are based on dividing the multiple signal classification (MUSIC) null-spectrum function into a number of equal subintervals. These subintervals are interpolated by using low-degree polynomials. Piecewise interpolation methods based on elementary functions are used to reduce the required computations of MUSIC null-spectrum function. This property reduces the computational complexity compared with line-search methods for DOA estimation. The Cramér Rao Lower Bound (CRB) is used as a benchmark to check the accuracy and validity of the proposed methods.

The complex permittivity of thickened waste activated sludge (WAS) was measured from 3 MHz to 40 GHz. The solid content of the thickened WAS sample was varied from 4.5% to 18% by weight. The permittivity spectra exhibit features typical of biological tissues that have a high water content. At high frequencies, a Debye type dispersion is observed with a relaxation rate of 19 GHz characteristic of the bulk water in the sample (γ-dispersion). At lower frequencies, the solid content of the samples determines the properties of the permittivity. The onset of the so-called β-dispersion, attributed to the charging of cell membranes, occurs between 10-100 MHz. For samples with higher solid concentrations, a weak dispersion of the real part of the permittivity, characteristic of bound water, was observed at intermediate frequencies (δ-dispersion).

A printed discone antenna with dual-band notched characteristics is presented for ultra-wideband applications. The proposed antenna consists of a radiation patch which has an outline expressed by binomial function and a trapeziform ground plane. Dual band-stop performance is achieved by etching a pair of Z-shaped slots on the ground plane and protruding a pair of π-shaped strips in the elliptical slot cut in the radiation patch, respectively, which can reject potential interference with the 3.25-3.8 GHz and 5-6 GHz bands. Surface current distributions and input impedance of the antenna are given to analyze the effects of the two resonant structures. The characteristics of the notched bands can be controlled independently by tuning related parameters. Moreover, the performances of the antenna are validated along with simulated and measured results.

This article reports on the design of a wideband compact microstrip-fed tapered slot antenna aimed at microwave imaging of a brain stroke. The antenna is immersed in a carefully designed coupling liquid that is used to facilitate higher signal penetration in the brain and thus increased dynamic range of the imaging system. A parametric analysis is used to find out the required properties of the coupling liquid. A suitable mixture of materials is then used to implement those properties. In order to protect the antenna from the adverse effects of the coupling medium, dielectric sheets are used to cover the radiator and the ground plane. To verify the proposed design in brain imaging, the antenna is tested using a suitable head model. It is shown that the antenna with a compact size (24 mm × 24 mm) on RT6010 substrate (dielectric constant = 10.2) operates efficiently over the band from 1 GHz to more than 4 GHz with more than 10 dB return loss. The time domain performance of the antenna supports its capability to transmit a distortion-less pulse with a high fidelity factor inside the head tissues.

There is some evidence that exposure of various animals to a power-frequency magnetic field can cause increases in body mass. However, the precise nature of the relationship is not clear, particularly for long-term exposure. To clarify the relationship between long-term power-frequency magnetic field exposure (2 years) and animal body mass, we conducted a pooled analysis of data in two studies to examine the impact of power-frequency magnetic field exposure on body mass as compared with sham-exposed rats of both sexes. Relative body mass was the response variable, and the study duration (in weeks), magnetic flux density ($\upmu$T), and daily exposure time (hours/day) were the explanatory variables with adjustment for the study. We analyzed by sex. The P-value (P) was defined as the probability of having observed our data (or more extreme data) when the null hypothesis was true. In multiple linear regression analyses of male and female rats, performed separately, we obtained estimates of the effect on relative body mass of study duration (coefficients 0.0225 and 0.0201, respectively; both P<0.0001), magnetic flux density (coefficient 0.0002 for males, P<0.0001; coefficient -0.0002 for females, P=0.0015), and daily exposure time (coefficient 0.046 for males, P=0.0007; coefficient -0.072 for females, P<0.0001). Our pooled analysis has shown that there is a possible relationship between duration of exposure to power-frequency magnetic fields and body mass in rats.

In this paper, we propose a multi-beam and multi-range (MBMR) radar with frequency modulated continuous wave (FMCW) waveform and digital beam forming (DBF) algorithm to cover a detection area of long range and narrow angle (150 m, ±10°) as well as short range and wide angle (60 m, ±30°) as a single 24 GHz sensor. The developed radar is highly integrated with multiple phased-array antennas, a two-channel transmitter and a four-channel receiver using K-band GaAs RF ICs, and back-end processing board with subspace-based DBF algorithm. The proposed 24 GHz MBMR radar can be used for an adaptive cruise control (ACC) stop-and-go system which typically consists of three radars, such as two 24 GHz short-range radars for object detection in an adjacent lane and one 77 GHz long-range radar for object detection in the center lane.

Small size capacitor loaded ground plane slots are used to reduce the mutual coupling between elements in a microstrip antenna array design. The proposed compact slots are inserted between the adjacent E-plane coupled elements in the array to limit the propagation of surface waves between the elements of the array. In order to validate the feasibility of the proposed structure, a two-element array with 0.5λ_o distance between centers of two patches is designed, fabricated, and measured. The measured results show a reduction in mutual coupling of 17 dB obtained between elements at the operation frequency of the array.

Compact K-Band CMOS baluns are designed, fabricated and characterized in a 130 nm CMOS technology. These baluns include a tunable active balun, a L-C lumped element balun, and two asymmetric planar transformer baluns. The detailed design processes are presented, including the topology selection, the transistor, inductor and transformer sizing, and the layout considerations. These topologies are compared in various aspects such as insertion loss, phase and amplitude imbalance, bandwidth, chip area, power consumption, and the difficulty to design and integration. An impedance tuning approach is implemented to chose the proper balun topology and to simply the balun integration. The baluns are on-wafer characterized and the measurement results compare the state-of-the-art realizations..

This paper presents characterization and modeling of microwave characteristics of SiC foam material. Transmission and reflection measurements are performed in X, K and Ka band for the samples of two different pore sizes and three different thicknesses. Effective and frequency dependent dielectric permittivity is extracted for 50PPI 10 mm sample, while for the other samples it was not possible because of density gradient in the samples. By calculation of Mie scattering efficiencies approximate magnitude of dominant loss mechanism (scattering or absorption) at certain frequencies is predicted.