A miniature single-layer CPW-fed monopole antenna with triple-band operation for wireless local area network (WLAN) and worldwide interoperability for microwave access (WiMAX) applications is presented. The proposed antenna, comprising a planar rectangular patch element embedded with dual U-shaped slot, is capable of generating three distinct operating bands, 2.37 - 2.53, 3.34 - 3.82, and 4.23 - 6.88 GHz covering all the 2.4/5.5/5.8 GHz WLAN bands and the 3.5/5.5 GHz WiMAX bands. The designed antenna has a simple uniplanar structure and occupies a small size of 25×18 mm2 including the finite ground CPW feeding mechanism. Moreover, the proposed antenna shows good monopole-like radiation patterns with small cross-polarization and stable antenna gains across the three operating bands.

In this paper, we present a comprehensive framework from synthesis to implementation of active matched filters for UWB Impulse Radio. The method delays and sums UWB pulses coherently to strengthen the signal over white Gaussian noise. Theoretical analysis shows that the signal peak is maximized against noise, and an arbitrary transfer function could be realized by adjusting filter parameters. To verify the concept, a four-stage matched filter operating in 3-5 GHz with 360 degrees phase delay is demonstrated first. It is implemented in a commercial 2-μm GaAs HBT process and achieves a power gain of 13.8 dB with a 10 dB bandwidth of 1.3 GHz. Based on a similar architecture, another design is presented but with only half of the delay. It has a power gain of 15.9 dB at the center frequency of 4 GHz and a 10 dB bandwidth of 2.3 GHz. An advantage of the proposed method is a precise control of the impulse response that can be matched to either symmetrical or asymmetrical UWB pulses by taking a time domain design approach.

In this paper, a high gain, low side lobe level Fabry Perot Cavity antenna with feed patch array is proposed. The antenna structure consists of a microstrip antenna array, which is parasitically coupled with an array of square parasitic patches fabricated on a FR4 superstrate. The patches are fabricated at the bottom of superstrate and suspended in air with the help of dielectric rods at 0.5λ₀ height. Constant high gain is obtained by resonating parasitic patches at near close frequencies in 5.725-5.875 GHz ISM band. The structure with 9 × 9 square parasitic patches with 1.125λ₀ spacing between feed elements is fabricated on 5λ₀ × 5λ₀ square ground. The fabricated structure provides gain of 21.5 dBi associated with side lobe level less than -25 dB, cross polarization less than -26 dB and front to back lobe ratio of more than 26 dB. The measured gain variation is less than 1 dB and VSWR is less than 2 over 5.725-5.875 GHz ISM band. The proposed structures are good candidates for base station cellular systems, satellite systems, and point-to-point links.

This paper reports algorithm and technique for the accurate phase calibration in order to measure current and voltage waveforms at the terminals of two-port microwave devices. The calibration approach presented in this paper does not require any multi-harmonic coherent signal generator and golden standard, reported in earlier papers, thus allowing the system to be more reliable, generic and accurate. The results achieved using the reported calibration algorithm on a developed measurement setup shows good agreement with those obtained on a standard commercial scope. In the end, it has been shown that the developed algorithm and measurement setup can be adapted for carrying out waveform engineering which clearly identifies the application of this work in the characterization and measurement of microwave devices.

This paper presents an extended delay-rational macromodel for electromagnetic interference analysis of mixed signal circuits. Firstly, an S-parameter matrix based delay-rational macromodel of the associated microwave network or system is established. Then, we extend the macromodel to include the external electromagnetic interference effects. The forced waves induced by the excitation fields are computed using full-wave method and treated as additional equivalent sources. Next, the macromodel is modified to embed the additional sources at each corresponding port. Finally, the resulting macromodel is converted into equivalent circuit for circuit analysis with the corresponding linear and non-linear port terminations. Several examples are computed by using the proposed method and the numerical results are compared with those obtained by 3-D FDTD method only. They are all in a good agreement that validate this method.

This paper presents a compact microstrip-fed slot antenna with triple-frequency operation. The proposed antenna structure consists of a cross-shaped microstrip feed line and multiple open-ended slots on the ground plane. By properly selecting shapes and dimensions of these embedded slots, the triple-resonance situations at 2.4/3.5/5.8GHz are obtained. Meanwhile, the cross-shaped feedline with shorting pin makes a joint benefit to adjust the matching condition and impedance bandwidth. The numerical and experimental results exhibit the designed antenna operates over triple frequency ranges and covers numbers of useful frequency bands for present wireless communication systems. In addition, acceptable radiation characteristics are obtained over the operating bands.

Linear embedding via Green's operators (LEGO) is a diakoptics method that employs electromagnetic ``bricks'' to formulate problems of wave scattering from complex structures (e.g., penetrable bodies with inclusions). In its latest version the LEGO integral equations are solved through the Method of Moments combined with adaptive generation of Arnoldi basis functions (ABF) to compress the resulting algebraic system. In this paper we review and discuss the convergence properties of the numerical solution in relation to the number of ABFs. Besides, we address the issue of setting the threshold for stopping the generation of ABFs in conjunction with the adaptive Arnoldi algorithm.

A multilayer dual-mode complementary filter is developed based on substrate integrated circular and elliptic cavity (SICC and SIEC) in this paper. The filter is constructed with two different kinds of cavities, and each cavity supports two degenerate modes, which can be generated and controlled by the coupling aperture and slot located between layers. Detailed design process is introduced to synthesize an X-band dual-mode complementary filter. It not only has good performance, but also reduces the circuit size much more. Moreover, Sharp transition characteristic both in the lower and upper sidebands demonstrates high selectivity of the filter. Good agreement is obtained between the simulated and measured results of the proposed structure.

A novel nano-antenna system design using photonic spin in a PANDA ring resonator is proposed. This photonic spins are generated by a soliton pulse within a PANDA ring, in which the transverse electric (TE) and a transverse magnetic (TM) fields are generated. The magnetic field is introduced by using an aluminum plate coupling to the microring resonator, in which the spin-up and spin-down states are induced, where finally, the photonic dipoles are formed. In operation, the dipole oscillation frequency is controlled by a soliton power, coupling coefficients, and ring radii. The obtained results have shown that THz frequency source can be generated by the proposed system. The advantage of proposed system is that the simple and compact nano-antenna with high power pulse source can be fabricated, which can generate and detecte the THz frequency in a single system.

A new CPW-fed dual-band circularly-polarized (CP) annular slot antenna with two perturbation strips is proposed. The structure of the annular slot, along with two concentric annular-ring patches, can achieve dual-band input impedance matching. And circular polarization at the operation bands can be achieved by using the two perturbation strips placed on the backside of the antenna. To reduce the resonant frequencies, a third strip protruded from the ground plane is introduced. Both the simulated and measured results show that the impedance bandwidths determined by 10-dB return loss are about 29.1% for the lower band (1.92-2.61 GHz) and 12.1% for the upper band (3.21-3.65 GHz). And the AR bandwidths are about 7.5% and 11.0%, respectively.

Linear magnetic gears take the definite merit of direct force amplification or speed reduction without using any bulky, inefficient rotary-to-linear mechanism. In this paper, an analytical calculation approach to determine the performance of linear tubular magnetic gears is proposed. The key is to adopt the concept of anisotropic magnetic permeability to handle the field-modulation region which consists of iron rings and airspaces in a zebra-striped manner. By solving the Laplace's and Poisson's equations in the linear tubular magnetic gear, the corresponding magnetic field distributions can be analytically determined. Finally, the analytical calculation results are compared with the numerical results obtained from the finite element method, hence verifying the validity of the proposed analytical field calculation.

A new adaptive beamforming technique based on neural networks (NNs) is proposed. The NN training is accomplished by applying a novel optimization method called Mutated Boolean PSO (MBPSO). In the beginning of the procedure, the MBPSO is repeatedly applied to a set of random cases to estimate the excitation weights of an antenna array that steer the main lobe towards a desired signal, place nulls towards several interference signals and achieve the lowest possible value of side lobe level. The estimated weights are used to train efficiently a NN. Finally, the NN is applied to a new set of random cases and the extracted radiation patterns are compared to respective patterns extracted by the MBPSO and a well-known robust adaptive beamforming technique called Minimum Variance Distortionless Response (MVDR). The aforementioned comparison has been performed considering uniform linear antenna arrays receiving several interference signals and a desired one in the presence of additive Gaussian noise. The comparative results show the advantages of the proposed technique.

A novel basis function, called as the Modified Phase Extracted (MPE) basis function, has been proposed to analyze three-dimensional scattering problems for electrically large, thin dielectric-coated targets. The MPE basis function, which can be defined on large (e.g., a wavelength or more) curvilinear geometrical elements, is developed for quadrilateral cells. Consequently, combining with the thin dielectric sheet (TDS) approximation, the MPE basis function solves the scattering problem accurately with fewer unknowns than the solutions based on the conventional basis functions. In order to improve the accuracy of the solution solving the problem which has thicker dielectric coatings, some modifications about the TDS approximation model are made. Numerical examples demonstrate that the validity of the proposed approach in solving the scattering from electrically large, thin coated objects.

The miniaturization of conventional ring resonators is demonstrated by forcing a voltage minimum at one end of the resonator. In addition, the resonator is loaded with a capacitance to achieve further miniaturization and reducing its sensitivity to substrate thickness tolerance. The final resonator is 73% smaller than a conventional ring resonator and has a tenfold decrease in sensitivity to substrate thickness variations. Using this resonator a 4-pole quasi-elliptic filter is fabricated showing good agreement between simulation and experimental results.

In this paper, the electromagnetic field of a horizontal infinitely long magnetic line source over the dielectric-coated earth is treated analytically, and the complete approximate solution for the radiated field under the far-field conditions is outlined. The total field is composed of four modes: the direct wave, the ideal reflected wave or image wave, the trapped surface wave, and the lateral wave. In particular, the complete analytical formulas are obtained for both the trapped surface wave and the lateral wave. The trapped surface wave is determined by the sum of residues of the poles. When the infinitely long magnetic line source or the observation point is away from the planar surface of the dielectric-coated earth, the trapped surface wave deceases exponentially in the z direction, and the total field is determined primarily by the lateral wave. When the conductivity of the earth is large, and both the infinitely long magnetic line source and the observation point are on or close to the air-dielectric boundary, the total field is determined primarily by the trapped surface wave.

This paper describes the investigation of broadband interaction and harmonic suppression. A special dispersion shape used in broadband traveling-wave tubes (TWT) is obtained. The theoretical and simulation studies of negative dispersion are presented. On the basis of these studies, a broadband TWT used in microwave power module (MPM) is designed. Compared with the old TWT with flat dispersion, the new one with negative dispersion decreases the second harmonic content about 10 dB and improves the fundamental efficiency about 5% at the low end of the band. The new one operates with the beam voltage of 3600 V and current of 250 mA. The modified TWT is fabricated and the simulation results meet the measurements very well.

This paper presents a design of circularly polarized dielectric resonator antenna (DRA) array. The dielectric resonators (DRs) were excited by rectangular aperture coupling slots feed with a linear microstrip. The slot positions were determined based on the characteristic of standing wave ratio over a short ended microstrip to deliver the maximum amount of coupling power to the DRs, in order to improve the array gain. Each DR element was rotated 45ᵒ with respect to the sides of the exciting slot to generate circular polarization pattern. The DRA array was modeled and simulated as a parallel RLC input impedance component using Agilent (ADS) software, since that will ensure the resonant frequency of the antenna as primary design step before simulating in (CST) software and doing the measurements. The results of the return loss, gain, radiation and pattern axial ratio are shown. The gain of the proposed array in X band was about 8.5 dBi, while the 3dB axial ratio bandwidth started from 8.14 to 8.24 GHz. The impedance bandwidths started from 8.14GHz to 8.26GHz. The proposed DRA exhibited an enhancement of the gain in comparison to a single pellet DRA. The size of the whole antenna structure is about 40 mm X 50 mm and can potentially be used in wireless systems.

The capabilities and operation of electromagnetic devices can be dramatically enhanced if artificial materials that provide certain prescribed properties can be designed and fabricated. This paper presents a systematic methodology for the design of dielectric materials with prescribed electric permittivity. A gradient-based topology optimization method is used to find the distribution of dielectric material for the unit cell of a periodic microstructure composed of one or two dielectric materials. The optimization problem is formulated as a problem to minimize the square of the difference between the effective permittivity and a prescribed value. The optimization algorithm uses the adjoint variable method (AVM) for the sensitivity analysis and the finite element method (FEM) for solving the equilibrium and adjoint equations, respectively. A Heaviside projection filter is used to obtain clear optimized configurations. Several design problems show that clear optimized unit cell configurations that provide the prescribed electric permittivity can be obtained for all the presented cases. These include the design of isotropic material, anisotropic material, anisotropic material with a non-zero off-diagonal terms, and anisotropic material with loss. The results show that the optimized values are in agreement with theoretical bounds, confirming that our method yields appropriate and useful solutions.

Microstrip patch antennas have several advantages over conventional antennas including their low profile structure, light weight and low cost. As such, they have been widely used in a variety of applications. However, one of the major drawbacks of this antenna is the low bandwidth. In this paper, bandwidth of a dual patch antenna is improved by etching dummy EBG pattern on the feedline. Effects of different positions of the feedline on the bandwidth are also studied. A good improvement in bandwidth for the antenna with the dummy EBG pattern when compared to the reference antenna is obtained for all the feedline positions.

This paper reports the modeling and characterization of interdigitated rows of carbon nanotube electrodes used to address a liquid crystal media. Finite Element Method modeling of the nanotube arrays was performed to analyze the static electric fields produced to find suitable electrode geometry. A device was fabricated based on the simulation results and electro optics characteristics of the device are presented. This finding has applications in the development of micron and submicron pixels, precise beem steering and nanotube based active back planes.