In this paper, a novel high selectivity dual-wideband microstrip bandpass filter (BPF) is proposed using two stub-loaded triple-mode stepped-impedance resonators (SIR) which are the same type but with different sizes. The SIR is formed by attaching one T-type open stub at the center plane and two identical short-circuited stubs symmetrically to stepped-impedance open microstrip line. And it can generate one odd mode approximatively determined by the stepped-impedance microstrip line and two even modes flexibly controlled by the loaded stubs. Either of the SIRs in this filter can not only separately generate one passband but also control the passband performance. Due to the intrinsic characteristics of the SIR, four transmission zeros can be created to improve the selectivity. A dual-wideband filter with the fractional bandwidth 14.9% for the first band from 3.09 GHz to 3.58 GHz and 10.2% for the second band from 4.99 GHz to 5.53 GHz is designed and fabricated. The filter is evaluated by experiment and simulation with good agreement.

The time domain modeling and simulation of electromagnetic (EM) waves interaction with nanodevices, at high spatial and time resolution, requires high computational power. For the first time, in this paper we present an effective implementation of the Hertzian Potential Formulation (HPF) on the Graphics Processing Units (GPUs), through the NVIDIA's CUDA (Compute Unified Device Architecture) programming model. It accelerates the nanodevice EM simulations at nanometer scale harnessing the massive parallelism of the GPU based systems. This study is useful for similar electromagnetic codes including the Finite Difference approaches. The results demonstrate that this GPU tool outperforms the CPU based HPF implementation, reaching a speedup from 30× to 70×.

A correlation spectroscopy (COSPEC) based on a multi-wavelength fiber laser is first proposed for the detection of gas concentration. The lasing wavelengths are selected to match several characteristic absorption peaks of the gas under test, and the gas concentration is easily measured by correlating it with the reference gas. The present method is immune from the instability of the light source and the influence of other gases. The concentration measurement of C₂H₂ is demonstrated in the experiment in its near-infrared dominant absorption region. The technique has prospects for simultaneous detection of multiple gases, and the measurement of mixed gases of C₂H₂ and CO₂ is also analyzed.

In this paper, design and fabrication of a quad-band microstrip bandpass filter (BPF) using multi-layered stepped impedance resonators (SIRs) structure is proposed. One pair of SIR on the top layer is designed to operate at the 1st and 3rd passbands (1.56/3.57 GHz), and the other pair is at 2nd and 4th passbands (2.42/5.23 GHz) by tuning the impedance and length ratios of the SIRs. In order to find the desired coupling location between the SIRs located on different layers and the input/output (I/O) lines, the voltage, current and power wave on the I/O lines are analyzed. It is verified that the proposed quad-band filter has good passband performances with an excellent isolation between adjacent bands for GPS, WLAN, and WiMAX applications.

This work deals with an exact solution of cylindrical wave equation for electromagnetic field in fractional dimensional space. The obtained fractional solution is a generalization of the cylindrical wave equation from integer dimensional space to a fractional dimensional space. The resulting theoretical framework can be used to study the phenomenon of electromagnetic wave propagation in any fractal media because fractal media can be described as an ordinary media in a fractional dimensional space. The classical results are recovered from fractional solution when integer dimensional space is considered.

A subwavelength array of planar triangle monopole antennas is proposed and discussed in this paper. Each element of the array is etched with many cross slots which bring no effects to the element's performances of voltage standing wave ratio and far-field radiation patterns. An important property of this antenna is that if multiple such planar antennas are placed face to face, the proposed array can perform time-reversal far-field focusing with a super-resolution as small as one twentieth of a wavelength. The proposed subwavelength array is easy to design and convenient for integration.

In this paper, to calculate the salient pole machine inductances under radial and axial non-uniformity, a new method is developed. The method, an extension of the modified winding function theory to 3D, allows studying salient pole machines with radial and axial non-uniform air gap considering more realistic mean radius of the air gap. By using the developed method and a precise geometrical model, inductances of a salient pole machine with inclined rotor are calculated. Inductances are evaluated and effects of several asymmetries on inductances are shown. Calculated inductances are used in a coupled electromagnetic model, for simulation of a salient pole machine under healthy and different inclined eccentricity conditions. Simulation results show that the 19th stator current harmonic can be detected to alarm for inclined rotors. Experimental results that validate the theoretical and simulation results are presented.

A 50% size reduction of the rectangular dielectric resonator antenna (DRA) is achieved by introducing shorting posts at the edge of the DRA in this paper. By choosing proper height of the shorting posts, the radiation pattern in E-plane maintains almost the same shape as the conventional rectangular DRA. The cross polarization can also be controlled to be a relative low level. By adding an open stub in the feed line, the proposed antenna has almost the same resonant frequency with the conventional rectangular DRA. The measured results for the constructed prototype are also exhibited and discussed.

Reflectionless cylindrical concentrators have been designed up to now in an initially empty core space by applying forminvariant, spatial coordinate transformations of Maxwell's equations. We show that the reflectionless cylindrical concentrators in initially homogeneous and isotropic dielectric core media allow an enhanced concentration of the incident field. Designs of more complex reflectionless concentrators in initially inhomogeneous dielectric media represented by empty or dielectric-filled circular containers are also presented. The transformation equations are given explicitly, and the fields are expressed analytically. The functionality of these devices is illustrated by several examples.

In this letter, a novel compact broadband and high rejection bandpass filter (BPF) with the source-load coupling is proposed using the triple-mode stub-loaded resonator. The resonator is formed by attaching one T-type open stub at the center plane and two identical short-circuited stubs symmetrical to high impedance microstrip line. It can generate one odd-mode resonant frequency f_m2 and two even-mode f_m1, f_m3 in the desired band. The f_m2 can be approximately determined by the high impedance microstrip line. The short-circuited stubs and T-type open stub can be applied not only to separately adjust the f_m1 and f_m3 while the two other ones keep relatively stationary, but also to separately create transmission zero near the lower and upper cut-off frequencies, leading to a high rejection skirt. As a result of the source-load coupling, two transmission zeros in the upper-stopband are generated to deepen and widen the upper-stopband. A high rejection BPF with the fractional bandwidth 76% is simulated, fabricated and measured. The measured results agree well with the EM simulations.

A new dual-polarized horn antenna fed by a microstrip patch is proposed. The patch is excited in two orthogonal polarizations by small gaps between the patch edge and the microstrip open end. A horn antenna operating at 14.9 GHz is designed, fabricated and tested. Measurements show that the horn has a reflection coefficient of less than -10 dB, and a port isolation greater than 30 dB, over 14.6--15.2 GHz, and a gain of 12.34 dBi and 10-dB beamwidths of 87° and 88° at 14.9 GHz.

Planar microstrip filters are designed to have a quasi-elliptic function passband and extended upper stopband with a rejection level of 40 or 50 dB. The design employs stepped-impedance resonators in a compact 2×2 cross coupled configuration. The geometric parameters of the resonators are planned to shift the third resonance as high as possible, and then the transmission zeros created by the structure are devised to suppress the second resonance, so that a wide upper stopband up to more than 4.5 times the passband frequency can be achieved. By employing the skew-symmetric input/output feeds, three transmission zeros in the frequency band of interest can be created. The leading two zeros are allocated on the both sides of the passband, generating a quasi-elliptic function response with enhanced roll-off rate in the transition bands, and the last zero incorporating with a zero created by anti-coupled-line at higher frequencies are employed to extend the rejection bandwidth. The measurement data agree very well with the simulation responses.

An innovative way to analyze the design of beam-forming networks (BFN) for scannable multi-beam circular antenna arrays using the CORPS (Coherently Radiating Periodic Structures) concept is introduced. This design of CORPS-BFN considers the optimization of the complex inputs of the feeding network by using the Differential Evolution (DE) method. Simulation results for different configurations of CORPS-BFN for a scannable circular array are presented. The results shown in this paper illustrate certain interesting characteristics in the behavior of the array factor for the scannable circular array. The most significant aspect that is unique to this proposal is the simplification of the feeding network based on CORPS.

An ultra-compact dual-band printed antenna is proposed. Connective and concentric double split rings (CCDSR) are used to generate two resonant frequencies in wireless local area network (WLAN) frequency bands. Tuning arms are added to the microstrip fed line, which can be used to tune the upper frequency band. The dimension of this antenna is only 9×24×1mm³, much smaller than those reported antennas. The measured -10 dB bandwidth in the 2.44GHz band is 140MHz (2.37-2.51GHz) and in 5.34GHz is 1.23GHz (4.86-6.09GHz), covering the 2.4/5.2/5.8GHz WLAN operating bands. Good radiations at these bands are also observed.

In this letter, for the very first time, triple band rectangular patch antenna loaded with metamaterial has been reported. Maximum directivities demonstrated here for all the three bands are quite high in comparison with previously reported any kind of rectangular patch antenna. This unique triple band performance has been achieved with the help of newly produced TM_0δ0 (3<δ<4) mode, symmetric slot loading and parasitic patch adjustment. Application of etched slot and parasitic patch in DPS (double positive)-metamaterial juxtaposed layer loaded antenna has been also demonstrated for the first time. Considering the quite satisfactory performance (S-parameter, radiation pattern and radiation efficiency) of this novel design, we expect that our proposed ideas will be very effective to design all these metamaterial loaded novel rectangular patch antennas.

This paper presents a novel frequency selective window for waveguide filters. It has a resonant characteristic with two attenuation poles on both sides of a passband, that is, a dual-behavior resonance. Such frequency selective windows make it possible to construct a compact bandpass filter having multiple attenuation poles without any additional coupling structures. As design examples, we show 3-pole Chebyshev waveguide filters with six attenuation poles in both the microwave and the millimeter-wave regions. The validity of the present filters is proven by the comparison of the frequency characteristics between the calculated and the measured results.

A seven ports network is proposed to act as a six-way power divider/combiner. The proposed network structure consists of a set of λ/4 planar transmission lines at the design frequency and does not require any isolating resistor. The power divider is capable of providing various power ratios by judicious choice of the transmission lines characteristic impedances. Design equations are derived for arbitrary power ratios. Simulation results obtained from the ADS software proved the possibility of achieving preset power ratios with fairly linear phase response over a certain bandwidth. The latter depends on the chosen power ratios. Measured results of manufactured power dividers agree well with simulations and theory.

A simple low-cost Y-branch plastic optical fiber (POF) coupler which can be assembled easily by the end users has been developed. The acrylic-based Y-Branch POF coupler consists of input POF fiber, a middle high index contrast waveguide taper and output POF fibers. The optical device is based on a 1x2 Y-branch coupler design with a middle high index contrast waveguide taper. Non-sequential ray tracing has been performed on the device giving an insertion loss of 4.68 dB and coupling ratio of 50:50. The middle waveguide taper region is constructed on the acrylic block itself without using any additional optical waveguiding medium injected into the engraved taper region. Fabrication of the devices is done by producing the device structures on an acrylic block using high speed CNC machining tool. Input and output POF fibers are inserted in to this device structure in such a way that they are passively aligned to the middle waveguide taper structure. The first prototype device shows an insertion loss of 7.5 dB and a splitting ratio of 50:50. A second prototype device which includes additional U-groove slots for the jacketed fibers shows an insertion loss of 5.9 dB and a splitting ratio of 50:50.

This paper presents an UWB antenna concept adapted for a potential application of RFID in a severe multi-paths environment for European regulation (UWB-LDR 6--8.5 GHz). The UWB provides theoretically the signal integrity and designing the UWB antenna is compatible with low size, cost and low complexity consideration. Under the hypothesis of using the same antenna at both transmitting or receiving states, the 1/f² effect of free space attenuation can be minimised by a pre-emphasis included in the antenna design, that is to say an ``f-gain" antennas at both transmitting (Tx) and receiving (Rx) parts. As a result, the printed antennas described are neither constant aperture nor constant gain type.

A rigorous and efficient spectral domain formalism is presented of a plane wave-excited subwavelength circular aperture in a planar perfectly conducting metallic screen of infinitesimal thickness, based on the Bethe-Bouwkamp quasi-static model. The formulation utilizes a transmission line analogue of the medium, which facilitates the inclusion of planar multilayered material samples, where the latter may exhibit uniaxial anisotropy. The transmitted field components are expressed in terms of one-dimensional Hankel transform integrals, which can be evaluated by efficient numerical procedures. Sample results are presented showing the intensity profiles and polarization states of transmitted light penetrating into a semiconductor layer.