Based on composite right/left-handed (CRLH) transmission line (TL),a novel series feed network for microstrip arrays is proposed and its theoretical analysis and experimental results are presented. In the present structure,p ower dividers and open-ended stubs are employed to even the amplitude distributions among different output ports,while CRLH TLs and short meandering lines are used to compensate the phase delay caused by the different lengths of righthanded (RH) TLs. Finally,an X-band series feed network is designed and fabricated as an example. The simulated and measured results indicate that the present design can achieve even amplitude and phase distributions among different output ports in the range of 8.8-9.6 GHz. And it has other advantages such as a compact size of 350mm×50mm and good return loss which is higher than 22 dB in the operation frequency.

The solution to the problem of far field radiation from an arbitrarily oriented Hertzian dipole in an electrically gyrotropic medium is found with the application of dyadic Green's function (DGF) technique. The form of the DGF, which is expressed as the sum of two single dyads, simplifies the derivation of the far fields significantly in comparison to the existing methods. The far field integral is evaluated analytically using the method of steepest descent. The numerical results for the radiation fields are presented in different frequency bandwidth using Clemmow-Mually-Allis (CMA) diagram. It is shown that the operational frequency bandwidth and the orientation of the antenna, which give the highest directivity and gain, can be determined when the CMA diagram is employed. Our analytical results are compared with the existing ones which were obtained using different techniques. Agreement is observed on all of them. The results presented in this paper can be used for radiation problems involving space exploration, radio astronomy or laboratory plasmas.

In this letter, we use two embedded isolation moats which have different size to obtain the wide stopband elimination performance. The proposed structure is realized by embedding the double isolation moats between power and ground planes. The suppression frequency range of the proposed structures is from 1.2 to 7.2 GHz and the peak noise improvement in time domain is 36%. Furthermore, the proposed structure uses two elimination cells to avoid the parasitic effect generated in the frequency range of several hundred MHz.

Bootlace lens is the most appropriate choice for multiple beam forming. A compact symmetric bootlace lens has been developed. Here, a theoretical modal is developed which predicts the primary amplitude distribution across the array port of the lens. Amplitude distribution depends upon the gain performance of array contour of the lens. This theoretical modal develops a symmetric bootlace lens without complex analysis.

This paper presents a numerical and experimental analysis of a horizontally polarized HF antenna?The antenna is aimed to be compact, wideband and high power gain. A V-shape wire-structured pentagonal antenna has acceptable performance in both aspects of gain and VSWR. The V-shape structure yields a comparatively high gain relative to the 27 m radiation arms. By incorporating both ground-loaded guys and convex pentagon-shape arms, the antenna can cover the whole HF band. The measured and simulated results show that the VSWR of this antenna is within 2.55:1 over 3~30 MHz and the average power gain is about 11 dBi.

ℜMulti-carrier system has been fuelled by large demand on frequency allocation, resulting in a crowded spectrum as well as large number of users requiring simultaneous access. Existing wireless systems may be utilized single frequency, single antenna and pulse for carrier transmission and reception. Problems of such system is that in case of failure the total system will become non operational. So we established a distributed system in terms of multi-carrier, multi-antenna and coded pulse can provide a more suitable communication and sensor gives rise to DSSS-OFDM-MIMO based hybrid technology is the ultimate solution. This technology is a promising technique for high-data-rate broadband wireless communications and radar because it can reduce interference, multipath effect, jamming and higher target resolution as compared to conventional communication & radar etc. The proposed techniques improve the performance of OFDM, DSSS and MIMO based wireless communications and sensing for ITS and other applications. Finally this system can be implemented using Software defined Radio to get continuous connectivity of the system.

Space-Time Adaptive Processing (STAP) is a well known technique in the area of airborne radars, which is used to detect weak target returns embedded in strong ground Clutter, Jammers, and receiver Noise. STAP has the unique property of compensating for the platform motion induced Doppler spread, thus making detection of slow targets possible. But there are others problems resulting from the characteristics of the airborne radar that may limit the performance of detection of the radar, for instance, the ambiguities (Range or Doppler ambiguities) which are dependent on the value of the pulse repetition frequency (PRF). When PRF is high, range ambiguities appear; when PRF is small, Doppler ambiguities appear; and both are present when PRF is medium. To resolve Doppler ambiguities staggering of PRF is used. And to resolve problem of high computational cost of optimal space-time processing, reduced-rank methods are used. In this paper, STAP processing on the airborne radar is briefly reviewed for motivation, and the effect of a radar parameter dimensionality set on the STAP and the Reduced-Rank STAP is discussed.

This paper presents a reconfigurable of multiple element microstrip rectangular linear array antenna integrated with radio frequency (RF) switches. The corporate feed design concept is used to excite the linear array antenna that consists of 8 elements of rectangular patches at 5.8 GHz. Two PIN diode switches were deployed at the feeding line to activate the two arrays of patches that is located on the left and right side of the antenna structure. The behavior of the reconfigurable multiple element linear antenna array system has been investigated with respect to the beam shaping characteristic. The comparisons of the performance between two structures, with Wilkinson Power Divider (WPD) and without WPD are discussed in this paper. Two different beam patterns were achieved through the reconfigurable antenna at different number of elements design that incorporates with PIN diode switches and modified WPD concept. The simulations and the measurement results for 4 and 8 elements array antenna structure are presented.

In this paper, direction-of-arrival (DOA) estimation of a single narrow-band source with uniform linear arrays is addressed. The basic idea is to convert the received data to a correlation sequence which can be modelled as a noisy sinusoid. Then the computationally attractive and accurate generalized weighted linear predictor frequency estimator is applied for DOA determination. The effectiveness of the proposed method is demonstrated via computer simulations.

Bismuth-based EDF (Bi-EDF) is comprehensively studied as an alternative medium for optical amplification. The bismuth glass host provides the opportunity to be doped heavily with erbium ions to allow a compact optical amplifier design. The gain spectrum of the Bi-EDF amplifier has a measured amplification bandwidth of 80 nm with a quantum conversion efficiency of 20% obtained using 1480 nm pumping and 215 cm long of doped fiber. A multi-wavelength laser comb is also demonstrated using a four-wave mixing effect in a backward pumped Bi-EDF. The laser generates more than 10 lines of optical comb with a line spacing of approximately 0.41 nm at 1615.5 nm region using 146 mW of 1480 nm pump power.

Electromagnetic scattering problems involving inhomogeneous objects can be numerically solved by applying a method of moment's discretization to the hypersingular volume integral equation in which a grad-div operator acts on a vector potential. The vector potential is a spatial convolution of the free space Green's function and the contrast source over the domain of interest. For electrically large problems, the direct solution of the resulting linear system is expensive, both computationally and in memory use. Conventionally, the fast Fourier transform method (FFT) combined Krylov subspace iterative approaches are adopted. However, the uniform discretization required by FFT is not ideal for those problems involving inhomogeneous scatterers and sharp discontinuities. In this paper, a nonuniform FFT method combined weak form integral equation technique is presented. The method performs better in terms of speed and memory use than FFT on the configuration involving both the electrically large and fine structures. This is illustrated by a representative numerical test case.

In this paper, Maslov's method has been used to obtain the high frequency field refracted by a hyperboloidal focusing lens. High frequency problem which contains caustic region is transformed into caustic free problem by transforming the situation into mixed domain. The high-frequency solution that includes the caustic region is obtained from geometrical optics. The defect in high frequency solution due to geometrical optics is overcomed by Maslov's method. Numerical computations are made for the field pattern around the caustic. The results are found in good agreement withobtained using Debye-Wolf focusing integral.

In this paper, we propose an efficient technique to mitigate the effects of both multiple access interference (MAI) and intersymbol interference (ISI) in downlink wireless CDMA systems. A hybrid scheme comprising beamforming at the base station and a regularized zero forcing equalizer at the mobile unit is suggested and studied. The proposed scheme uses the beamforming to reduce the effect of the MAI. Then, the regularized zero forcing equalizer is used to reduce the effect of ISI and provide a better estimate of the data. The performance of the proposed scheme is studied and compared with traditional schemes. Our simulation results show a noticeable performance improvement by using the proposed scheme with low complexity at the mobile unit.

A compact elliptic-function low pass filter using microstrip stepped-impedance modified-hairpin resonators is developed and a multiple cascaded filter using semi-hairpin resonators is designed, analyzed and tested. Sharpness of cut off frequency, low insertion-loss, enhancement of bandwidth and very compact size are features of the proposed low-pass filter. Size reduction of this filter is reported about 62% with 13% enhancement of bandwidth respects to the conventional filter with comparable performance. The measurement results are in good agreement with the theoretical ones.

A comprehensive energy model for wireless sensor networks is provided by considering seven key energy consumption sources some of which are ignored by currently available models. We demonstrate the importance of using such a comprehensive model by comparing it to other existing energy models in terms of the lifetime of a sensor node. We use our model to evaluate energy consumption and node lifetime for a sensor network with fixed configuration and we validate this evaluation by simulation. We show that existing energy models over-estimate life expectancy of a sensor node by 30-58% and also results in ``optimised" number of clusters which is too large. We further make the following two observations: 1) the optimal number of clusters increases with the increase of free space fading energy, 2) for sensor networks with 100 sensors over area of 10⁴-10⁵ [m²], finding the optimal number of clusters becomes less important when free space fading energy is very low (less than 1670 pJ/bit/m²), while for larger networks, on the other hand, cluster optimization is still important even if free space fading energy is low. Guidelines for efficient and reliable sensor network design as well as extension to a sensor network with rotating cluster heads are provided.

Based on dielectric resonators, the design and implementation of planar left-handed metamaterials made of dielectric blocks are investigated in this paper. By etching simple metallic patterns on surface of the dielectric blocks, field distributions of the desired resonance modes can be enhanced while those of the undesired are suppressed. In this way, the resonance frequency of the desired mode can be tuned down to lower frequency range. A wide-angle polarization-independent planar left-handed metamaterial based on disk-like dielectric resonators is proposed and analyzed. Such a left-handed metamaterial is independent of the polarization of incident waves. Moreover, its double-negative property keeps almost the same under a wide range of incident angles. At the end, practical implementation of the lefthanded metamaterial by using flexible supporting slabs is given. Due to its polarization-independence, wide range of incident angle and high flexibility, the proposed left-handed metamaterial is ready to be used in various microwave components, such as antenna radomes, microwave filters and frequency selective surfaces.

Ultra-short pulse is a promising technology for achieving ultra-high data rate transmission which is required to follow the increased demand of data transport over an optical communication system. Therefore, the propagation of such type of pulses and the effects that it may suffer during its transmission through an optical waveguide have received a great deal of attention in the recent years. Our goal in this paper is to study the propagation characteristics of that pulse in a nonlinear optical fiber. In analyzing these characteristics, the nonlinear effects along with the dispersion are taking into account. Additionally, the considered nonlinear effects include self phase modulation (SPM) and stimulated Raman scattering (SRS). The problem to be processed is modeled using the finite difference time domain (FDTD) technique which represents an efficient tool in achieving the required purpose. Because of the symmetrical structure of the optical waveguide, the FDTD modeling of bodies of revolution (BOR) in cylindrical coordinates is the most preferable algorithm in analyzing our problem. The FDTD treatment of dispersion and nonlinearity of the optical waveguide is accomplished through the direct integration method. In addition, the Lorentzian model is chosen to represent the dielectric properties of the optical fiber. The azimuthal symmetry of optical fiber enables us to use a two-dimensional difference lattice through the projection of the three-dimensional coordinates (r, φ, z) into the (r, z) plane. Extensive numerical results have been obtained for various cavity structures.

We study the influence of the resistivity frequency dispersion effects on the magnetotelluric (MT) response. Impedivity is the term used to indicate the frequency dependent resistivity in rocks. The impedivity functions, used in this paper, have been derived from the general solution of the motion equation of a charge carrier, discussed in a previous paper. A 1D three-layered earth section, with the second layer assumed to be dispersive, is considered to analyze the distortions due to dispersion on the modulus and phase of the MT responses on the earth's free surface. The MT responses of the section, where the dispersive layer is attributed an impedivity function describing at first a positive, then a negative and finally a resonant dispersion model, are computed for various combines of the dispersion parameters. A general conclusion is that the dispersion effects can strongly influence the MT response either in recognizable or in subtle forms. In the former case, the distortions appear as either steeply rising and/or descending curve branches or spike-like deltas, not compatible with a dispersion-free section. In the latter case, instead, the MT curves preserve the typical behavior for a dispersion-free section, and may thus erroneously be modeled by a section, where the dispersive layer is totally suppressed. In both case, disregarding the distortion effects may lead to misleading conclusions as to the physical properties of the surveyed structures.

A planar Dual Exponentially Tapered Slot Antenna(DETSA) is presented in this paper. The DETSA is simulated and designed with the sofware Ansoft HFSS. The dimensions of the antennas and the exponential functions of tapered slot are also described. To verify the design, the DETSA is fabricated and measured, good impedance matching over a very wide bandwidth is achieved, measured radiation patterns of the proposed antenna is compared with the simulated one, good agreement is observed.

A novel composite right/left handed transmission line is presented which is synthesized by etching Koch fractal shape slot in the ground plane and series capacitive gap in the conductor strip. Unlike the structures loaded with complementary split ring resonators (CSRRs), the proposed structure can operate at very wide band and is used to design an ultra-wideband (UWB) filter. The UWB filter is fabricated and tested. The relative bandwidth of the -10 dB return loss is 128% and the insertion loss is larger than -1.5 dB except at high frequencies. The equivalent circuit model of the proposed structure is presented and the electrical parameters are also extracted. The circuit model results are compared with the simulation and measurement results which verify that not only the extracted parameters are exact but also the equivalent circuit model is reasonable.