A method to enhance gain of a circularly polarized (CP) microstrip patch antenna is proposed. We etch coupled square-shaped split ring resonators (CSSSRRs) on both sides of a superstrate which is separated from the patch by an air layer. Thickness of the air layer is around 0.1λ, which keeps the radome in low profile. Open gaps of each CSSSRR on opposite sides of the superstrate are orthogonally oriented to each other. This unique orientation allows the radome not only enhance gain but also maintain good CP performance.

The common approaches to sample a signal generally follow the well-known Nyquist-Shannon's theorem: the sampling rate must be at least twice the maximum frequency presented in the signal. A new emerging field, compressed sampling (CS), has made a paradigmatic step to sample a signal with much less measurements than those required by the Nyquist-Shannon's theorem when the unknown signal is sparse or compressible in some frame. We call a compressed-sampling filter (CSF) one for which the function relating the input signal to the output signal is pseudo-random. Motivated by the theory of random convolution proposed by Romberg (for convenience, called the Romberg's theory) and the fact that the signal in complex electromagnetic environment may be spread out due to the rich multi-scattering effect, two CSFs via microwave circuit to enable signal acquisition with sub-Nyquist sampling have been constructed, tested and analyzed. Afterwards, the CSF based on surface acoustic wave (SAW) structure has also been proposed and examined by the numerical simulation. The results has empirically shown that by the proposed architectures the S-sparse n-dimensional signal can be exactly reconstructed with O(Slogn) real-valued measurements or O(Slog(n/S)) complex-valued measurements with overwhelming probability.

This paper presents a dual-band dual-polarized antenna array design for WLAN applications. Four double-dipole elements are orthogonally interleaved to facilitate operation in both the standard WLAN frequency bands (IEEE 802.11b and IEEE 802.11a) simultaneously. The two linear polarizations have separate ports. The presented design is characterized by dual-band operation, reasonably good front-to-back ratios, average gains of 5.2 dBi and 6.2 dBi over the 2.4 and 5.2 GHz bands respectively, stable end-fire radiation patterns and very low cross-polarization levels.

This is a presentation of an innovative technique of rigid body estimation for use with laser high-range resolution profile (LHRRP) simulations. The theory of pulse beam scattering from random rough surface is used to build a theoretical model which computes simulations for the laser pulse HRRP of the whole dimension target. As two especial cases, the LHRRP of sphere and cone are simulated in detail. We discuss and analyze some influential factors on laser radar HRRP imaging such as their dimensions, correlation length and height root mean square of the rough surface, refractive index of the material and width pulse. The simulated results suggest that the reliable identifications are possible provided in some aero and aerial recognized applications with higher resolution by laser radar.

The Finite Volume Time-Domain (FVTD) method finds limited application in the simulation of electromagnetic scattering from electrically large scatterers because of the fine discretization required in terms of points-per-wavelength. An efficient implementation of a higher-order FVTD method is proposed for electrically large, perfectly conducting scatterers. Higher-order and fine-grid accuracy are preserved, despite using only a first-order spatial accuracy and a coarse grid in substantial parts of the FVTD computational domain, by partially incorporating a time-domain Physical Optics (PO) approximation for the surface current. This can result in considerable savings in computational time while analyzing geometries containing electrically large, smooth sections using the FVTD method. The higher-order FVTD method in the present work is based on an Essentially Non-Oscillatory (ENO) reconstruction and results are presented for two-dimensional perfectly conducting scatterers subject to Transverse Magnetic (TM) or Transverse Electric (TE) illumination.

Based on a new concept, i.e., charge moment tensor and the rotational equation of a charged dielectric rigid body about a fixed-point under a uniform external magnetic field, one symmetrical case has been rigorously solved. The rotational stability has been analyzed in detail for two cases, general and symmetrical, respectively, by means of some techniques of matrix analysis.

An accurate 2D steady state mathematical model for induction heating process is described and additional results of electromagnetic field, eddy currents distribution and volumetric heat generation have been computed for a sample setup using a finite element method. For the calculations, the input voltage of induction coil is set to be 200 ν with a frequency of 10 kHz. It was shown that for the case considered here, the distribution of eddy currents density along the radius/thickness of the workpiece has a damped sinusoidal wave-shaped form.

In this paper, a coplanar waveguide fed (CPW-Fed) ultra-wideband (UWB) antenna with dual band-notched characteristics is proposed. Two symmetrical slots are etched from the ground plane to achieve the notched band at 5.5 GHz. The other notched band at 3.5 GHz is obtained by etching a split ring slot in the radiator. The simulation and measurement show that the proposed antenna achieves an impedance bandwidth of 3.1-10.6 GHz with VSWR < 2, except in the bands of 3.2-3.8 GHz and 4.8-6.2 GHz. A nearly omnidirectional radiation pattern and stable gain with variation less than 3 dB are also observed except in the two notched bands. Moreover, time-domain characteristics of the antenna are analyzed and discussed as well.

A split-band directly modulated fiber optical CATV system employing -1 side-mode injection-locked and semiconductor optical amplifier (SOA)-based optical single sideband (SSB) modulation techniques is proposed and experimentally demonstrated. For our proposed systems, it is relatively simple to implement as only one SOA is required. Excellent performances of carrier-to-noise ratio (CNR), composite second order (CSO), and composite triple beat (CTB) were achieved over a-100 km single-mode fiber (SMF) transmission.

This paper presents a novel technique to improve the cross-polarization and the beam efficiency of an offset parabolic reflector antenna used for space borne radiometric applications. A special multi-mode primary feed (tri-mode conjugate matched feed) is used to illuminate the offset parabolic reflector antenna. The simulated data on the radiation characteristics of the offset parabolic reflector antenna with a matched feed has been compared with that of a conventional Potter horn. It is observed that the tri-mode feed suppress the unwanted high cross-polarization of an offset reflector antenna and improves the beam efficiency.

This paper shows that an optimal antenna pattern for active phased array synthetic aperture radar (SAR) has been synthesized to meet the best performances based on particle swarm optimization (PSO) and adaptively selected weighting factors. Because the antenna radiation pattern has a very close relation with the performance of an active phased array SAR system, the authors derived the multi-objective cost functions on the basis of the system performance measures such as the range-to-ambiguity ratio, noise equivalent sigma zero, and radiometric accuracy. The antenna mask templates were derived from the SAR system design parameters in order to optimize the system requirements. To effectively minimize the cost functions and to search for the amplitude and phase excitations of an active phase array SAR antenna, the authors applied the PSO technique to SAR antenna pattern design and also carefully selected weighting factors to improve the fitness of the cost functions on the basis of the SAR performance.

In this paper, the architecture of a smart antenna prototype is described and its functionality assessed. The system prototype is composed by an 8-elements linear array of dipoles with a finite reflecting plane and the adaptive behavior is obtained modifying a set of array weights with electronically-driven vector modulators. In order to real-time react to complex interference scenarios, the system is controlled by a software control module based on a Particle Swarm Optimizer. To demonstrate the feasibility and the effectiveness of the proposed implementation, a set of representative results concerned with different interference scenarios is reported and discussed.

A hybrid electromagnetic-network analysis of the antennas-channel multiple input multiple output (MIMO) communication subsystem is presented. The analysis is based on the antenna effective and realized effective length matrices, which relate in a compact mathematical way the radiated and received electric field intensities to the network characteristics of actual and coupled transmitting (Tx) and receiving (Rx) multi-element antenna (MEA) systems. The effective length matrices are calculated via the active power gain and phase antenna patterns obtained by means of any full wave computational electromagnetics (CEM) field solver. It is shown that the realized effective length matrix is suitable for the S-parameter analysis of a MIMO communication link, while the effective length matrix is convenient for its Z-parameter analysis. The effective length matrix framework is applied to a free space 2x2 coupled dipoles MIMO system and its results are in excellent agreement to those obtained by a Method of Moments (MoM) based field solver.

In order to obtain a unified approach for the Finite-Difference Time-Domain (FDTD) analysis of dispersive media described by a variety of models, the coordinate stretched Maxwell's curl equation in time domain is firstly deduced. Then the FDTD update formulas combined with the semi-analytical recursive convolution (SARC) in Digital Signal Process (DSP) technique for general dispersive media are obtained. In this method, the flexibility of FDTD in dealing with complicated object is retained; the advantages of absolute stability, high accuracy, less storage and high effectiveness of SARC in treating the linear system problem are introduced, and a more unified update formulation for a variety of dispersion media model including Convolution Perfectly Matched Layers (CPML) absorbing boundary is possessed. Therefore it can be applied to analysis of general dispersive media provided that the poles and corresponding residues in dispersive medium model of interest are given. Finally, three typical kinds of dispersive model, i.e. Debye, Drude and Lorentz medium are tested to demonstrate the feasibility of presented approach.

In this paper, the design, simulation, and fabrication of a novel printed circular slot antenna with a band-notched function suitable for UWB application is presented and investigated. The band-notched characteristic is achieved and adjusted by inserting L-shaped branches into the ground plane. Experimental results show that the proposed antenna meets the requirement of wide working bandwidth of 3.1-10.6 GHz with return loss < -10 dB, while avoiding the interference with the 5-GHz WLAN band. The study of transfer function (amplitude of S₂₁/group delay) and time domain characteristic (fidelity/power spectrum density (PSD)) indicate a band-notched function of the antenna. The proposed antenna has a compact size, good radiation characteristics, ultra wide band-width, and good time-domain behaviors to satisfy the requirement of the current wireless communication systems.

In this paper, one 3×3 and one 5×5 antenna arrays are studied. In each array, one probe-fed circularly polarized (CP) microstrip patch antenna is placed at the center as the driven antenna and is gapped coupled to the remaining elements. It is investigated that CP performance of the patch can be proved by properly arranging these parasitic elements. The driven patch is a perturbed square one with two diagonal corners truncated. The remaining elements are square patches slightly smaller than the driven patch. The proposed antennas have been constructed and measured. The 3×3 array has a measured gain of 7.7 dBic with a 3 dB axial ratio bandwidth of 3.3%. The 5×5 array has a measured gain of 9.3 dBic with a 3dB axial ratio bandwidth of 8.1%.

A novel triple-mode hexagonal bandpass filter with capacitive loading stubs is introduced in this article. The technique, adding an open capacitive stub, is applied to enlarge the equivalent self-capacitance of the resonator, which declines its resonant frequencies. Three radial-line stubs in the center of top layer are used to implement this technique. One mode resonant frequency is varied with the radii of three radial-line stubs, while the other two modes are nearly not affected. This filter has a pair of transmission zeros which are close to the passband, thus it behaves with high selectivity. For method validation, a bandpass filter operating at 2.4 GHz is fabricated and measured. The experimental results are demonstrated and discussed.

A compact dual-band power divider for GSM/DCS applications is proposed in this letter. Novel planar artificial transmission lines are applied to miniaturize the power divider and achieve wideband response. The proposed dual-band power divider is about 37% of conventional one. The design principle, simulated and measured results are all discussed. The measured results show that good performance can be achieved at the operation frequencies.

Fractional rectangular impedance waveguide has been studied using fractional curl operator. Behavior of field inside the fractional rectangular impedance waveguide has been studied with respect to the original impedance of walls of the guide as well as fractional parameter. Analysis of the impedance of the walls as well as power distribution over the cross sectional plane of fractional impedance rectangular waveguide has been given. It has been found that fractional curl can be used to control the power distribution pattern over the cross sectional plane.

A novel wideband multilayered microstrip antennas with shorting pins and arc-shaped apertures loaded is designed and fabricated. The antenna consists of two dielectric substrates and a quasi H-shaped circular patch with five shorting pins and four arc-shaped apertures loaded on the upper layer. Multiple layers are employed to achieve wide bandwidth by stacked electromagnetic coupling. The arc-shaped apertures and shorting pins are used to excite multiple modes, which can change the cavity's electromagnetism characteristic with influencing the series-parallel connection inductance, so that the wide bandwidth is obtained. Effects of the key parameters on the wideband performance are also studied, and a set of optimum values is chosen for the antenna design. The impedance bandwidth (VSWR < 2.0) of the proposed antenna reaches 2.59 GHz with the measured results, which means the relative impedance bandwidth is expanded up to 34.7% across 6.17 to 8.76 GHz. Simulation results agree well with measured ones.