This paper presents a formulization of time domain (TD) discrete electromagnetic (EM) solution to provide an effective analysis over a variety of EM problems. This procedure first represents the time responses of EM fields in terms of a set of selected basis functions. Their coefficients are then employed to create matrix-form Maxwell's equations with forms analogous to frequency domain (FD) Maxwell's equations, which allows one to formulate TD solutions via utilizing their corresponding FD solutions that are existing and generally much mature. This work provides general characteristics with parts previously described in the discrete-time EM theory [20, 21] and, most importantly, provides rigorous theoretical derivations in formulating the TD solutions.

In this paper, we improve the Ge-Esselle's (GE's) method and apply it to calculate the multilayered Green's functions in the shielded structures. In the improved GE's method, 1) the poles are first extracted using a recursively contour integration method [1]; 2) then the general pencil-of-function (GPOF) [2] is performed to approximate the part of the spectral-domain Green's functions (with the poles contributions being extracted) just along the real axis of k_ρ plane instead of the rooftop shaped path defined in [3]; 3) Subsequently, the GE's analytical method is employed to obtain the spatial-domain Green's functions. In step 2), a smoothing procedure is also performed here to eliminate the abrupt peak of the sampled spectral-domain Green's function caused by the finite machine accuracy of the poles locations. The numerical results in this paper show that the improved GE's method can accurately and efficiently calculate the Green's functions in the shielded multilayered structure.

We have studied the problem of diffraction of plane waves by a finite slit in an infinitely long soft-hard plane. Analysis is based on the Fourier transform, the Wiener-Hopf technique and the method of steepest descent. The boundary value problem is reduced to a matrix Wiener-Hopf equation which is solved by using the factorization of the kernel matrix. The diffracted field, calculated in the far-field approximation, is shown to be the sum of the fields (separated and interaction fields) produced by the two edges of the slit. Some graphs showing the effects of slit width on the diffracted field produced by two edges of the slit are also plotted.

This work is about evaluating radar performance in detection of targets embedded in a clutter following Non centered chi-2 Gamma distribution model. This model, also called NG-distribution model, is able to fit high resolution sea radar clutter. In this paper, NG model is described. The performances of CA-CFAR radar, namely probability of detection and probability of false alarm, are calculated and closed forms of these probabilities are achieved. In order to evaluate the obtained results, simulation and analytical results are compared. Good matching between these results is achieved.

A compact Pi-structure transformer operating arbitrary dual band is proposed in this paper. To achieve the ideal impedance matching, the exact design formulas with no restrictions are obtained. In addition, it is found that there are infinite solutions for this novel transformer considering the fact that three independent variables exist in two equations. And to verify the design formulas, the reflection characteristics in different cases are shown by numerical simulations. The horizontal length of this transformer is half of the Monzon's dual band transformer. The proposed dual band transformer can be used in many compact dual band components design such as antennas, coupler and power dividers.

This paper studies the correlation of a receiving thin dipole with an arbitrary load in both anechoic chamber (AC) and reverberation chamber (RC). In both cases, the method of moments is employed to calculate the current distributions along a thin dipole induced by external fields. In AC, a plane wave with a fixed incident angle and polarization is illuminated on the dipole; whereas in RC, the field is represented by an appropriate superposition of many incident plane waves with stochastic incident angles, polarizations and phases. Numerical results for the current distributions of a thin dipole with different loads and electrical lengths are presented and discussed in both chambers. It is demonstrated that the ratios with respect to current magnitudes at the arbitrary load of the thin dipole between AC and RC are determined by its directivity. In particular, the ratios with respect to current magnitudes along the entire dipole whose electrical length is less than half a wavelength are nearly constants regardless of the terminating load, which indicates that results obtained in both chambers are well correlated.

We present here a new pattern with compact size of Ultra Wideband (UWB) microwave filter. The filter is based on quarter-wave length short-circuited stubs model. We introduced here a new schematic model by extracting all parasitic elements such as T-junction and discontinuity in our new pattern of UWB filter. This new filter has minimal number of vias and improved frequency bandwidth, insertion loss and return loss. It is fabricated on RT Duroid 5880 with 0.508mm of substrate thickness. The final dimension is measured as 21mm×14 mm. It is not only compact, but also delivers excellent scattering parameters with magnitude of insertion loss, |S₂₁| lower than 0.85 dB and return loss better than -11.6 dB. The fractional bandwidth is 109% from 3.06 GHz to 10.43 GHz. In the pass band, the measured group delay varies in between 0.47 ns to 0.32 ns, showing stability with minimum variation of only 0.15 ns.

This paper presents performance analysis of cellular CDMA in presence of beamforming and soft handoff. A stop and wait ARQ scheme has been assumed for data service. Joint effects of beamforming and soft handoff reduce delay, BER and increase throughput significantly. Impact of several parameters of soft handoff and beamforming on data performance has been evaluated. Both the cases of perfect and imperfect beamforming have been investigated. Effects of DOA (Direction of arrival) estimation error have also been indicated on data service.

In our previous works, we have presented one differential method for the efficient calculation of the modal scattering matrix of junctions in rectangular waveguides. The formalism proposed relies on the Maxwell's equations under their covariant form written in a nonorthogonal coordinate system fitted to the structure under study. On the basis of a change of variables, we show in this paper that the curvilinear method and the generalized telegraphist's method lead to the same system of coupled differential equations.

A validation process, in which simulations and measurements are compared, is necessary to have confidence in the results obtained by numerical methods that solve scattering problems. This paper presents Radar Cross Section (RCS) measurements of new targets suitable for electromagnetic software comparison and validation. These measurements can be used as an RCS reference data for testing existing and future codes, as well as for the analysis of the scattering mechanisms.

In this paper, we present a fast method to predict the monostatic Radar Cross Section (RCS) in high-frequency of a cavity, which can be modeled as a succession of bent waveguides of the same cross section and stuffed by a perfectly-conducting termination. Based on a modal analysis combined with the Kirchhoff Approximation, this method allows us to obtain closed-form expressions of the transmission matrix at each discontinuity. In addition, to improve the efficiency, a selective modal scheme is proposed, which selects only the propagating modes contributing to the scattering. Compared to the Iterated Physical Optics (IPO) method and the Multi-Level Fast Multipole Method (MLFMM, generated from the commercial software FEKO), this approach brings good results for cavities with small tilt angles of the bends, typically smaller than 2 degrees.

The phase noise is a very important index to wireless system, especially in millimeter-wave continuous wave radar systems. The phase noise of the signal, which is firstly leaked from transmitter and then mixed to intermediate frequency band by the local oscillator (Tx-IF), will worsen the sensitivity of supper heterodyne radar system used for Doppler velocity detection. In this paper, the coherent analysis is applied on the phase noise after nonlinear process, which shows that the phase noise of the Tx-IF is affected by those factors: the magnitude of the phase noise of the transmitter and that of the local oscillator, and the correlationship between each other. In practice, by reducing the phase noise of the transmitter and that of the local oscillator and ameliorating the correlationship of the two phase noises, the phase noise of the Tx-IF can be improved greatly. Such proposition is successfully applied in the design of a millimeter-wave Doppler radar working at 95 GHz. The experimental measurement shows that the sensitivity of this radar is better than -70 dBm.

Two focus-scanning schemes, viz. lens-fixed scanning scheme and lens-combined scheme, are proposed for near-field target detection and imaging. Specific lens size must be determined for future lens building in order to achieve desired imaging resolution and convenient data acquisition. Influence of LHM lens size on the performance of two different focus-scanning schemes are investigated and compared by simulating the detection of a perfect electric conductor target of diameter of 2 mm. Numerical simulations indicate that the lens-combined scanning system using thick LHM lens of thickness of two wavelengths requires at least a length of one wavelength to achieve resolution better than 0.4 wavelengths, while the lens-fixed scanning system requires a lens of lengthof approximately 3 wavelengths. When a thin LHM lens is used, high imaging resolution is not a consequent result for the focus-scanning approaches, although thin lens generally yields high focusing resolution. Some guidelines on the selection of length and thickness of flat LHM lens are reported.

Spectrum sharing between wireless systems becomes a critical issue due to emerging new technologies and spectrum shortage. Recently, IMT-Advanced system has been allocated in the same frequency band (3500 MHz) along with fixed services on co-primary basis, which means that harmful interference probability may be transpired. Channel bandwidths (BW) and natural of deployment areas of wireless systems are of the main effective factors in spectrum sharing. Spectrum Emission Mask (SEM) model will be used to study these factors effects beside the interference to noise ratio (I/N) as a fundamental criterion for coexistence and sharing between systems. The frequency and distance separation and antenna high effects are essential to be investigated to achieve spectrum sharing.

Experimental study and SPICE simulation of CMOS digital circuits latch-up effects due to high power microwave interference are reported in this paper. As a traditional inherent destruction phenomenon, latch-up effect may jeopardize the correct function of the circuits, and could be triggered in various ways such as ESD pulse, cosmic ray, heavy ion particles etc. Through the directly injected experimental investigation of CMOS inverters, it is shown that the single short high power RF pulse not only could disturb and upset the inverters output logic voltage, but also might trigger CMOS latch-up effects. It is observed that the RF pulse leading to inverters latch-up effects have energy threshold characteristics, which means that the injected RF pulse power is inversely proportional to the pulse width. SPICE simulations indicated that the inverters maximum static consumption current in latch-up state will increase up to 6600 multiples compared to the normal value when input logic state is high. With the device scaling down, higher integration and higher working frequency, the power consumption problem plays a significant role, which makes CMOS logic circuits more vulnerable due to the latch-up effects under high power microwave threats.

This paper presents a hexagonal shape defected ground structure (DGS) implemented on two element triangular patch microstrip antenna array. The radiation performance of the antenna is characterized by varying the geometry and dimension of the DGS and also by locating the DGS at specific position which are found experimentally. Simulation and experimental results have verified that antenna with DGS had improved the antenna without DGS. Measurement results of the hexagonal DGS have axial ratio bandwidth enhancement of 10 MHz, return loss improvement of 35%, mutual coupling reduction of 3 dB and gain enhancement of 1 dB.

The paper describes a novel low profile circularly polarized antenna. The antenna is a single dipole over a particular wire formed panel with high impedance properties. Although the principles of operation for the antenna are general, in this work they are specifically applied to the design and optimization of a FM broadcasting antenna. The distinguishing feature of the design is that it incorporates the following interesting concepts simultaneously: artificial high impedance surfaces or artificial magnetic conductors, materials showing refractive indexes of less than unity (n < 1), and polarizing structures. Another advantageous aspect of the design is the computational efficiency emerging from this fact that the structure is entirely wire made. This way the relevant numerical analysis and optimization can be efficiently carried out by NEC, a one-dimensional (1D) MoM-based EM analyzer.

This paper presents an efficient meshless approach for solving electrostatic problems. This novel approach is based on combination of radial basis functions-based meshless unsymmetric collocation method with projection domain decomposition method. Under this new method, we just need to solve a Steklov-Poincare interface equation and the original problem is solved by computing a series of independent sub-problems. An electrostatic problem is used as an example to illustrate the application of the proposed approach. Numerical results that demonstrate the accuracy and efficiency of the method are stated.

This paper proposes two methods for increasing the Gain of Vlasov Antenna. The first method, using a Parabolic Cylinder Reflector, results in a 7dB increase in the Gain. The second method, constructing a Horn on the aperture, increases the Gain by about 5dB. The results were checked using a prototype antenna and there was a close agreement.

Abstract-Radiation characteristics of a probe-excited rectangular ring antenna are investigated by using the dyadic Green function approach. The radiation characteristics, such as radiation pattern, beam-peak direction, half-power beamwidth and directivity, are analyzed. For the specified operating frequency, the ring width and ring height are selected as the same crosssectional dimension of rectangular waveguide operated at the dominant mode. The effects of the excited probe and rectangular ring to the modal distributions are described. For the desired modal distribution, the directivity primarily depends on the ring lengths. For compact size of the proposed antenna, the ring length of 0.4λ is chosen to provide a bidirectional pattern with the calculated half-power beamwidth in E-plane and H-plane of 100 and 69 degrees respectively, and directivity of 4.43 dBi. Furthermore, the prototype antenna was fabricated and measured. The coincided results between the theory and the experiment are obtained.