Planar metamaterials with spiral elements are suggested in this paper to support multiple left-handed (LH) modes. Compared with previously proposed split-loop metamaterial, spiral arrays are found to support hybrid TE and TM LH modes. Dispersion diagrams and field distributions are carried out to demonstrate the existence of the hybrid LH modes. Array with double-spiral elements can be viewed as a spiral split-loop array, which leads a very interesting dual-LH-band feature. It can be explained as a combination of spiral and split-ring arrays has similar mechanism with the multiband frequency selective surfaces (FSS), which have multiple resonators in a single unit cell. The two LH modes are TE and TM modes respectively. Validations of the multiple LH modes are presented by means of full-wave simulation using commercial software (Ansoft HFSS).

In this paper we propose a digital beamformer utilizing the radar integrator method of detection. In the receive mode the digitized radar returns weights are allocate on the such a way that the first pulse reflect a SUM pattern and the subsequent three pulses reflect DIFFERENCE pattern. The pulses on DIFFERENCE pattern are added to each other and the net signal subtracted from signal received in SUM pattern. This results in very narrow beam which shows narrow spatial resolution. The schematic is presented and the results are shown.

In this paper, we introduce a new method: support vector regression (SVR) method to modeling low temperature co-fired ceramic (LTCC) multilayer interconnect. SVR bases on structural risk minimization (SRM) principle, which leads to good generalization ability. A LTCC based stripline-to-stripline interconnect used as example to verify the proposed method. Experiment results show that the developed SVR model perform a good predictive ability in analyzing the electrical performance.

Am ultiresolution frequency domain (MRFD) analysis similar to the finite difference frequency domain (FDFD) method is presented. This new method is derived by the application of MoM to frequency domain Maxwell's equations while expanding the fields in terms of biorthogonal scaling functions. The dispersion characteristics of waveguiding structures are analyzed in order to demonstrate the advantages of this proposed MRFD method over the traditional FDFD scheme.

A new technique to evaluate the dielectric constant and loss factor of a homogeneous dielectric material using rectangular shaped perturb cavity has been developed. The values of S-parameters are measured experimentally by placing the sample in the center of the cavity resonator. Sample under test is fabricated in the form of a cylinder. The real and imaginary part of the permittivity can be then calculated from the shift in the resonance frequency and Q-factor. The results of a Teflon sample are also tabulated.

An analytical model of composites made of a dielectric base and randomly oriented metal inclusions in the form of nanorods is presented. This model is based on the generalized Maxwell Garnett (MG) mixing rule. In this model, the nanorod particles are modeled as prolate spheroids with a statistically normal distribution of their aspect ratios. It is shown that parameters of the distribution laws affect the frequency characteristics of the composites both at microwave and optical frequencies. The results of computations are represented.

This paper investigates broadband planar antennas that consist of a wide rectangular slot with various tuning stubs. The antennas are fed by coplanar waveguides. Wide slots containing a single tuning stub, V-shaped stubs, as well as inverted F-shaped stubs are investigated. Despite using a high dielectric constant substrate, the proposed antennas exhibit very broad bandwidth. They also have broadside bidirectional radiation. The radiation pattern stability with frequency for the various configurations is presented. One of the proposed configurations, the inverted F stub in a wide rectangular slot, produced very stable radiation patterns over its entire impedance bandwidth of about 40%. Also, an impedance bandwidth of 44% was obtained for the V-shaped stub in a rectangular slot. Simulations as well as experimental results are presented.

This study analyzes polarizability properties of spherically layered small inclusions that possess negative permittivity. Conditions for invisibility to external electric fields are derived. The complementary principle for two-dimensional scatterers is used to derive special properties of self-complementary inclusions. A singular behavior between the limits of invisibility and infinite response is underlined for a hollow circular shell. A similar,although not as drastic,phenomenon is shown to take place for the three-dimensional hollow sphere.

Metamaterials with small electrical size are more feasible to be described by the macroscopic parameters and treated as an effective homogenous media. By using geometric optimization, we experimentally realize a metamaterial composed of crankled S-ring resonator,whose electrical size is 2.5 times smaller than the conventional S-ring resonator. The overall effective capacitance of the unit structure is greatly increased when viewed from an equivalent circuit model point of view,so the resonant frequency is decreased, and the metamaterial works at a much longer wavelength regime. In addition,w e summarize two kinds of other methods that could be used to reduce the electrical size of the structures. Experimental and simulation results are presented,sho wing the effectiveness of these methods in the metamaterial homogenization.

An efficient metal-insulator-metal (MIM) capacitor simple scalable model for use in monolithic-microwave integrated circuit (MMIC) design is presented in this paper. This model is based on transmission-line theory. Analytical expressions based on physical parameters have been given in detail. Nine different physical dimension capacitors are fabricated to verify the validity of the proposed model. A good agreement between measured result and simulated data is obtained.

This paper studies the performance appraisal of radiation performance of ultra low sidelobe level Active Phased Array Antennas in presence of Multilayer Flat Sandwich Radome. Further, the effect of errors introduced due to amplitude/phase quantisation and planarity of the array surface, on the radiation performance has been studied. Based on these errors, manufacturing tolerances of the Flat Sandwich Radome have been suggested to control the deterioration of radiation performance within tolerable limits. This work is expected to be useful in development/manufacturing of radomes for Active Phased Array Radars and similar applications where ultra low sidelobe levels are required to be maintained.

This paper presents an optimum design technique ofan asymmetric V-dipole antenna and it's a three-element Yagi-Uda array using Genetic Algorithm (GA). The optimization parameter for the V-dipole is the directivity and that for the Yagi-Uda array are the input impedance and directivity. The theoretical analysis has been done using a Moment-Method technique in a very simple step-by-step way, and subsequently the GA is applied for obtaining the optimized parameters. Comparative results are provided for 3-elements straight dipole Yagi and V-dipole Yagi array. Further, analysis for directivity with respect to included angle is given for the GA based optimization problem that gives an important aspect in the design of V-Yagi.

In this paper, a new tapered beamforming function for side lobe reduction in the uniform concentric circular arrays (UCCA)is proposed. This technique is based on tapering the current amplitudes of the rings in the array, where all elements in an individual ring are weighted in amplitude by the same value and the weight values of different rings are determined by a function that has a normalizedgaussian probability density function variation. This novel tapering window is optimized in its parameters to have the lowest possible side lobe level that may reach 43 dB below the main lobe and these optimum weights are found to be function of the number of elements of the innermost ring and the number of rings in the array. The proposed tapering window can be modified to compensate the gain reduction due to tapering when compared with the uniform feeding case.

A general circuit model is proposed for frequency domain analysis of inhomogeneous two-dimensional periodic gratings. Each component of electromagnetic fields is expressed by several spatial harmonic plane waves. Then, two differential equations and two boundary conditions are obtained for the electric and magnetic vectors. Finally a circuit model is introduced for the obtained equations. The circuit model consists of loaded and excited nonuniform coupled transmission lines (CTL).

A generalized equivalent circuit model for waveguide transverse slots is proposed for the efficient analysis of waveguide transitions and waveguide slot antennas and slot-excited antennas. The transverse slots on the broad and end waveguide walls analyzed in this paper are decomposed into three structures: two apertures and an auxiliary waveguide section. The slot aperture in the host waveguide is modeled as an inductance-capacitance-transformer (LCT) combination, for which the equivalent inductance and capacitance are determined by first considering the case of zero-thickness slot, then the transformer turns ratio is calculated for the slot on a finite thickness wall. The effect of the wall thickness is accounted for by a waveguide section having cross-sectional dimensions equal to those of the slot, and length equal to the wall thickness. The loaded slot aperture is modeled along with the external load as a lumped load impedance. Expressions for the inductance, capacitance and transformer turns ratio are obtained in terms of the slot length and width. The obtained expressions facilitate the design of a variety of structures, including waveguide couplers, feeding networks and radiators. The equivalent circuit model proved to be accurate compared to the method of moments solution over a wide frequency band. Comparison of the scattering parameters obtained from the circuit analysis, the method of moments, and the finite-difference time-domain solutions exhibit very good agreement.

A kind of microstrip array double-antenna (MADA) and its corresponding radar front-end are presented in this paper. The double-antenna comprises two individual 4-patch arrays which are coplanar in a round substrate with 25mm diameter and are used as receiver antenna and transmitter antenna respectively in 36 GHz radar front-end. Both simulation and test results of the antenna are exhibited, which shows better isolation between two arrays below −42 dB in a wide band. Test results of radar front-end with MADA are also presented, from which we can see perfect performance the system has. With improvement of radar system, a more compact MADA with 18.6mm diameter is designed, fabricated and measured, which shows a good response.

This paper discusses the analysis of a novel two-segment rectangular dielectric resonator antenna (DRA) for broadening of the impedance bandwidth. In the proposed configuration, two rectangular dielectric sections are used which are separated by a metal plate. With this configuration, it is possible to excite two adjacent resonant frequencies. Utilizing the two-segment thin DRA and skillfully varying its aspect ratio, an appropriate structure is obtained that illustrates more than 76.8% impedance bandwidth (for S₁₁>10 dB) at 3.32- 7.46 GHz frequency band.

In this paper, a new structure is proposed for microwave filters. This structure utilizes a waveguide filled by several dielectric layers. The relative electric permittivity and the length of the layers are optimally obtained using least mean square method. The usefulness of the proposed structure is verified using an example.

In the present paper the response of V transmission line to electromagnetic illumination has been obtained. Also in order to determine the VTL frequency operation band for both TE and TM modes a Gaussian pulse source has been applied to the structure. The VTL structure has received considerable attention in high frequency and microwave IC packaging. The purpose of this study is to determine high frequency design considerations in order to reduce the effects of electromagnetic interference (EMI) on the VTL structure and maintain the desired performance. It was observed that the effect of incident EM waves on the V lines performance is considerably lower than conventional microstrips, however the V lines are more sensitive to sources at close proximity. In addition, although the V lines show lower dispersion at higher frequencies, their frequency operation band is limited by a resonance like behavior which is directly related to the V groove dimensions. The full wave analysis is carried out using the Yee-cell based 2 Dimensional Finite Difference Time Domain method (2D-FDTD), while enforcing a very stable and efficient mesh truncation technique.

Space division multiple access (SDMA) is a promising can- didate for improving channel capacity in future wireless communication systems. Considering that discrimination performance of the user in the spatial domain depends on the array arrangement, and as a result the optimum element arrangement for SDMA should be defined, beam- forming play a very important role providing fundamental theory of design procedure. However the pattern of antenna array is determined by array geometry. Two-dimensional (2-D) spatial filters that can be implemented by microstrip technology are capable of filtering the re- ceived signal in the angular domain as well as the frequency domain. This paper focuses on various geometries of eight and nine elements antenna arrays using circularly patch elements as well as hexagonal ar- ray with seven elements. The network throughput is further analyzed to determine if using a fully adaptive pattern (LMS algorithm gener- ated pattern) results in a higher throughput with or without presence of mutual coupling effects.