This paper presents the design, fabrication and measurement of a polarization insensitive microwave absorber based on metamaterial. The unit cell of the metamaterial consists of four-fold rotational symmetric electric resonator and cross structure printed on each side of a print circuit board to realize both electric and magnetic resonances to achieve efficient absorption of the incident microwave energy. Both the full wave electromagnetic simulation and the measurement on the fabricated absorber demonstrate high microwave absorption up to 97% for different polarized incident electromagnetic waves. To understand the mechanism, analysis is carried out for the electromagnetic field distribution at the resonance frequency which reveals the working mode of the metamaterial absorber. Moreover, it is verified by experiment that the absorption of this kind of metamaterial absorber remains over 90% with wide incident angle ranging from 0° to 60° for both transverse electric wave and transverse magnetic wave.

In this study, annular-ring microstrip patch on uniaxial medium is analysed in Hankel Transform Domain. Equivalent models of the structure are obtained depending on the TE and TM mode decomposition in this domain. For the simplification of the tensor form formulations, equivalent matrix operators are defined in cylindrical coordinates instead of the differential ones. Then, resonant characteristics of the structure is determined via the application of the moment method and compared with the isotropic case for different anisotropy ratio values and structural parameters. Equivalent circuit models for the case of multilayered substrates and superstrates are given in order to be used in the following studies on annular-ring microstrip patch.

This paper presents a simple and innovative deterministic approach to the synthesis of uniformly excited thinned arrays able to fulfill constraints concerning both the sidelobe level and the value of the radiated far field (and/or of the directivity) in a set of given directions. Starting from a reference regular (periodic or even aperiodic) lattice and from an optimal continuous reference source fulfilling at best the required specifications, the proposed approach finds out both the number and the location of the isophoric (i.e., equi-amplitude) radiating elements to withdraw in a fast and effective fashion. In fact, it is based on a deterministic best-fitting procedure which takes inspiration from existing density taper techniques. Examples are provided with reference to the synthesis of large circular arrays and confirm the interest of the proposed procedure.

In this paper, a half mode substrate integrated with folded waveguide (HMSIFW) and a HMSIFW partial H-plane bandpass filter are proposed. The proposed filter employs H-plane slot of open-ended evanescent waveguide and H-plane septa of short-ended evanescent waveguide as admittance inverter and impedance inverter, respectively. The filter has advantages of convenient integration, compact size, low cost, mass-producibility and ease in fabrication. In order to validate the new proposed topology, a four-pole ultra-narrowband bandpass filter, with quarter wavelength resonators, is designed and fabricated using standard printed circuit board process. The tapered line is used as transition between HMSIFW and microstrip-line for easy integration and measurement. The measured results are in good agreement with simulated ones, and good selectivity is achieved.

In this paper, we propose a circularly polarized (CP) stacked annular-ring microstrip antenna (SARMSA) with an integrated feeding network in the UHF RFID band. A circular parasitic patch is suspended above the annular ring to improve the impedance matching and bandwidth. Through the parametric studies on SARMSA, the CP characters of the entire antenna are well understood，and an optimized CP character is obtained. Prototypes are fabricated to confirm the theoretical results. The experimental results indicate the impedance bandwidth for S₁₁<-10 dB is 870-967 MHz (10.6% at 915 MHz)，and the 3 dB AR bandwidth is 893-948 MHz (6%). Meanwhile, the measured CP gain reaches 8.9 dBic at 915 MHz.

We present the design, processing and testing of a W-band finite by infinite and a finite by finite Grounded Frequency Selective Surfaces (FSSs) on infinite background. The 3D full wave solver Nondirective Stable Plane Wave Multilevel Fast Multipole Algorithm (NSPWMLFMA) is used to simulate the FSSs. As NSPWMLFMA solver improves the complexity matrix-vector product in an iterative solver from O(N²) to O(N log N) which enables the solver to simulate finite arrays with faster execution time and manageable memory requirements. The simulation results were verified by comparing them with the experimental results. The comparisons demonstrate the accuracy of the NSPWMLFMA solver. We fabricated the corresponding FSS arrays on quartz substrate with photolithographic etching techniques and characterized the vector S-parameters with the free space Millimeter Wave Vector Network Analyzer (MVNA).

A polarimetric scattering from two-dimensional (2-D) rough surface is presented by the finite-difference time-domain (FDTD) algorithm. The FDTD calculations with sinusoidal and pulsed plane wave excitations are performed. As the sinusoidal FDTD is concerned, it is convenient to obtain the scattered angular distribution of normalized radar cross section (NRCS) from rough surface for a single frequency. And the advantage of pulsed FDTD is to calculate the frequency distribution of NRCS from rough surface in a scattered direction of interest. A single frequency scattering from rough surface by sinusoidal FDTD is validated by the result of Kirchhoff Approximation (KA). And the frequency response of rough surface by pulsed FDTD is verified by that of sinusoidal FDTD, which requires an individual FDTD run for every frequency. To save computation time, the MPI-based parallel FDTD method is adopted. And the computation time of parallel FDTD algorithm is dramatically reduced compared to a single-process implementation. Finally, the polarimetric scattering of rough surface with the sinusoidal and pulsed FDTD illumination are presented and analyzed for different polarizations.

Design and optimization of high-power microwave (HPM) feed horn by combining the aperture field with radiation patterns are presented in the paper. The optimized feed horn in C band satisfies relatively uniform aperture field, power capacity higher than 3 GW, symmetric radiation patterns, low sidelobes, and compact length. Cold tests and HPM experiments were conducted to investigate the radiation patterns and power capacity of the horn. The theoretical radiation patterns are consistent with the cold test and HPM experimental results. The power capacity of the compact HPM horn has been demonstrated by HPM experiments to be higher than 3 GW.

In this paper we present a Lanczos-type reduction method to simulate the low-frequency response of multiconductor transmission lines. Reduced-order models are constructed in such a way that low frequencies are approximated first. The inverse of the transmission line system matrix is then required and an explicit expression for this inverse is presented. No matrix factorization needs to be computed numerically. Furthermore, computing the action of the inverse on a vector requires an O(N) amount of work, where N is the total number of unknowns, and the inverse satisfies a particular reciprocityrelated symmetry relation as well. These two properties are exploited in a Lanczos-type algorithm to efficiently construct the low-frequency reduced-order models. Numerical examples illustrate the performance of the method.

The paper deals with the evaluation of the far-field radiated emissions from high-speed interconnects when the frequencies are such that the distribution of the currents along the traces is no longer of TEM-type. Instead of a computationally expensive numerical full-wave model, here a generalized transmission line model is used to obtain the current distributions. This full-wave transmission line model is derived from an integral formulation and is here extended to include in efficient way the layered media Green's Functions. The proposed tool is successfully benchmarked to references given in literature and case-studies of practical interest are carried out, referring to a coupled microstrip, driven either by differential and common mode currents. This analysis highlights the existence of a transition range where the error made by evaluating the emission using the classical transmission line current distribution is still negligible. Here a rule of thumb is derived which provides a simple criterion to estimate this extension of the range of validity of the classical transmission line.

The excitation of an antisymmetric trapped mode on a symmetric metamaterial resonator is experimentally demonstrated. We use an active electronic device to break the electrical symmetry and therefore to generate this trapped mode on a symmetric spilt ring resonator. Even more, with such a tunable mode coupling resonator, we can precisely tune the resonant mode frequency. In this way, a shift of up to 15 percent is observed.

To overcome the Courant limit on the time step size of the conventional finite-difference time-domain (FDTD) method, some weakly conditionally stable and unconditionally stable FDTD methods have been developed recently. To analyze the relations between these methods theoretically, they are all viewed as approximations of the conventional FDTD scheme in present discussion. The errors between these methods and the conventional FDTD method are presented analytically, and the numerical performances, including computation accuracy, efficiency, and memory requirements, are discussed, by comparing with those of the conventional FDTD method.

In this paper, design, fabrication, and testing of Radio Frequency Identification (RFID) antennas for the European Telecommunications Standards Institute (ETSI) and Federal Communications Commission (FCC) bands are discussed. The designs proposed in this paper are for UHF RFID tag that conforms to EPCglobal C1G2 1.2.0. The exceptional characteristics of the RFID are investigated in terms of antenna-IC matching and radiation efficiency. The proposed RFID antennas have been fabricated on 5 mil thick Flexible Copper Clad Laminate and the read range of the proposed RFID antennas is experimentally tested. Measured free air read range of all proposed designs is over 4 m. The performance of the tag antenna design affixed to various objects is also tested with read range measurements. The results show that the antenna designs can be used for tagging cardboard and plastic objects.

In this paper, the closed-form design method of an N-way dual-band Wilkinson hybrid power divider is proposed. This symmetric structure including N groups of two sections of transmission lines and two isolated resistors is described which can split a signal into N equiphase equiamplitude parts at two arbitrary frequencies (dual-band) simultaneously, where N can be odd or even. Based on the rigorous even- and odd- mode analysis, the closed-form design equations are derived. For verification, various numerical examples are designed, calculated and compared while two practical examples including two ways and three ways dual-band microstrip power dividers are fabricated and measured. It is very interesting that this generalized power divider with analytical design equations can be designed for wideband applications when the frequency-ratio is relatively small. In addition, it is found that the conventional N-way hybrid Wilkinson power divider for single-band applications is a special case (the frequency-ratio equals to 3) of this generalized power divider.

A novel configuration for an end-wall microstrip-to-waveguide splitter transition is presented suitable for use in series fed microstrip arrays. The low price, simplicity, manufacturability, low sensitivity, and also wideband operation, up to more than 37%, is the result of positive interaction between double slots and double stubs. The transition is applied to a dual band 1 × 2 array. A wideband non-tilted pattern is achieved.

The dispersion relation is derived for the most general configuration of a passive and reciprocal periodically loaded transmission line in a unique and simple form by introducing two novel parameters. Based on this relation, the phase and group velocities are determined and a simple condition for phase reversal propagation is obtained. The two above mentioned parameters help us to develop a polar diagram to model the behavior of any two-port network as a function of frequency. By this diagram, we can determine the direction of the phase velocity and also the value of the propagation constant. Then, symmetrical cells and thereof the periodic structures composed of them are analyzed. For such structures, it will be shown that the dispersion relation can be rewritten in a form similar to the Lorentz transformation. We design and analyze a bandstop filter to verify the method.

Holography is a technique employed to make three dimensional images using electromagnetic waves. Holographic interferometry is one of the most important applications of holography. It is concerned with the formation and interpretation of fringe patterns, which appears when a wave generated at some earlier time and stored in a hologram is later reconstructed by interfering with comparison wave. We report a technique, which uses double exposure holographic interferometry together with simple mathematical interpretation, which allows immediate finding of stress, mass, fringe width and thickness of thin film. We tested different normalities of solutions. It is observed that increase in deposition time increases thickness and mass of thin film but decreases stress to substrate. The thin films are prepared using electrodeposition technique. The structural, optical and surface wettability properties of the deposited films have been studied using X-ray diffraction (XRD), optical absorption and contact angle measurement, respectively.

This paper presents a novel optimization technique biogeography based optimization (BBO) for antenna array synthesis. BBO is a relatively new evolutionary global optimization technique based on the science of biogeography. It is capable of solving linear and non-linear problems. In this paper, BBO algorithm is used to determine an optimum set of amplitudes of antenna elements that provide a radiation pattern with maximum side lobe level reduction and/or null placement in the specified directions. The results obtained show the effectiveness of the BBO algorithm, and they are better than previous published results.

In this paper, two full-wave simulators (one using finite difference time domain method and the other the method of moments) are developed, in order to analyze wireless communication in boxes with metallic enclosure based on time-reversal ultra-wideband (TR-UWB) technique. Impedance boundary conditions are exploited to model realistic metallic walls, and parallel computing is applied to relieve high computational resources requirements. Focusing on both space and time is exhibited by numerical results in arbitrarily shaped metallic boxes, which demonstrates the feasibility of TR-UWB communication in metallic boxes.

In this paper, we propose tunable optical interleaver filters based on the combined Michelson interferometer (MI) and the Gires-Tournois interferometer (GTI) with polarization diversity. The tuning capability is achieved by integrating liquid crystals into the interleaver. In addition to the tunability, it is also shown that the response for this proposed interleaver has a flat-top. Various GTIMI LC-based interleaver structures are discussed in this paper and their performance, in terms of the flat-top and the pass band ripple, are judged. These structures have the advantages of low operation voltage requirements and design simplicity. A GTI-MI interleaver has been fabricated and tested. The experimental results show that the interleaver has tunable response.