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.

The fading phenomenon resulting from standing waves is a factor in quality deterioration in mobile communication technologies (e.g., cellular phones and television receivers). Suppression of this fading phenomenon is needed for many kinds of technologies. A single-feed planar antenna composed of two antenna components, a Planar Monopole Antenna (PMA) and a Planar Slot Antenna (PSA), is proposed for reducing deterioration of reception due to the fading phenomenon. Reflection coefficient and radiation patterns are analyzed by the Finite Difference Time Domain (FDTD) method and compared with measured results. Results indicate that the proposed antenna has a resonant frequency with functions of the PMA and the PSA. The results of a field experiment at 583.76MHz in the Ultra High Frequency (UHF) band indicate that the proposed antenna efficiently suppresses the fading phenomenon resulting from multipath propagation.

The design and manufacture of a circular polarized aperture stacked patch circular microstrip patch antenna (CPASPA) at L-band is presented. The Wilkinson power divider is used to excite the stacked circular patches by two orthogonal $H$-shape slots, which can improve the operation bandwidth and circularly polarized performance. The design is optimized by a series of parametric study of the input impedance for the antenna. The measurements show that the CPASPA has a 3-dB axial ratio (AR) bandwidth of 55.0% and a 10-dB return loss (RL) bandwidth of 47.0%. The measured gain is more than 0 dBic over the bandwidth of 42.5%, in which the maximum is 9.4 dBic. The measurements agree very well with the simulation results.

This paper presents an extension of the recently-developed efficient semi-analytical method, namely scaled boundary finite element method (SBFEM) to analyze quadruple corner-cut ridged circular waveguide. Owing to its symmetry, only a quarter of its cross-section needs to be considered. The entire computational domain is divided into several sub-domains. Only the boundaries of each sub-domain are discretized with line elements leading to great flexibility in mesh generation, and a variational approach is used to derive the scaled boundary finite element equations. SBFEM solution converges in the finite element sense in the circumferential direction, and more significantly, is analytical in the radial direction. Consequently, singularities around re-entrant corners can be represented exactly and automatically. By introducing the "dynamic stiffness" of waveguide, using the continued fraction solution and introducing auxiliary variables, a generalized eigenvalue equation with respect to cutoff wave number is obtained without introducing an internal mesh. Numerical results illustrate the accuracy and efficiency of the method with very few elements and much less consumed time. Influences of corner-cut ridge dimensions on the cutoff wave numbers of modes are examined in detail. The single mode bandwidth of the waveguide is also discussed. Therefore, these results provide an extension to the existing design data for ridge waveguide and are considered helpful in practical applications.

Based on the Helmholtz integral equation and series expansion theory, a high order integral small perturbation method (HISPM) for studying electromagnetic wave scattering from the finite conducting rough surface with tapered transverse electric (TE) wave incidence is presented. The high order scattering coefficients are obtained by the series expansion, the validity and accuracy of HISPM is verified through numerical evaluation with classical small perturbation method (CSPM) and the method of moments (MOM). By comparing with CSPM for the infinite rough surface case with plane wave incidence, the presented HISPM can greatly reduce the edge diffraction effect. HISPM also shows advantages in the memory requirement and computational time, especially in calculating scattering coefficients with low grazing angle incidence. Numerical examples are given to show that with the increasing of the length of the rough surface, the memory requirements and the computation time of HISPM are dramatically reduced compared to those of MOM.

Non coaxial mutual inductance calculations, based on a Bessel function formulation, are presented for coils modelled by an explicitly finite number of circular turns. The mutual inductance of two such turns can be expressed as an integral of a product of three Bessel functions and an exponential factor, and it is shown that the exponential factors can be analytically summed as a simple geometric progression, or other related sums. This allows the mutual inductance of two thin solenoids to be expressed as an integral of a single analytical expression. Sample numerical results are given for some representative cases and the approach to the limit where the turns are considered to be smeared out over the solenoid windings is explored.