The retrieval of the surface profile of a reflector antenna is an important task, mainly for radio-astronomical applications. The microwave holography retrieves the reflector profile starting from a set of measured far-field data. The main step of this technique is the computation of the induced currents on the reflector surface. This requires the solution of a linear inverse problem which is strongly illconditioned. We propose a new technique, based on the Singular Value Decomposition, for the solution of this linear inversion problem. This technique supplies a flexible regularization scheme, able to take into account also the noise level of the data. The proposed procedure has been tested on a number of different cases, with field data generated by a commercial software.

Analysis of U-slot loaded patch stacked with H-shaped parasitic elements is given in this paper. It is found that the antenna exhibits dual resonance and both the resonance frequency (upper and lower) depends directly on slot width and inversely on slot length. Both upper and lower resonance frequency increase with increasing the value of h₂. Typically the bandwidth at lower and upper resonance is found 3.66% and 10.25% respectively. The radiated power at higher frequency (beamwidth 64^o) is 0.73 dB as compared to lower resonance frequency (beamwidth 71^o). The theoretical results are compared with the simulated data obtained from IE3D.

To design less costly and time consuming Photonic Crystal Fibers it is better to use Empirical Relations Method instead of Scalar Effective Index Method. If we compare both empirical relations method and scalar effective index method by accurate and powerful methods like Full-Vector Finite Element Method, we find that empirical relations method has less error than scalar effective index method in calculating PCF parameters such as n_fsm, n_eff , and the second order dispersion. According to the investigations, we concluded, the inherent error of scalar effective index method approximately increases when pitch decreases. In large pitches the calculation of dispersion by scalar effective index method reveals less error in low wavelengths than high wavelengths and finally we calculated the third order dispersion which is important in some applications.

The approximate analytical solution of the integral equation concerning the current in a thin straight vibrator with complex surface impedance has been obtained. The vibrator is located in unlimited space and is excited in an arbitrary point along its length. The calculations have been made and the plots of electrodynamic characteristics of the vibrator, depending of the value and the type of its surface impedance and the excitation point location, are represented. The comparative analysis between the calculated and the experimental data and also the results, obtained by the method of moments, are represented for perfectly conducting vibrators.

Dual-band bandpass filters featuring compact size and flexible frequency choice are demonstrated using resonators based on slotted ground structures. Two resonators based on slotted ground structures form the basis of the filter design. The resonators allow the back-to-back and face-to-face embedding configuration, hence, greatly reduces the physical size of the filters. By changing the sizes of the two resonators independently, the lower and upper resonance frequencies can be adjusted to the desired values. A dual-band broadband bandpass filter was implemented with good compactness and low insertion loss. A good agreement is obtained between the simulation and measurement results.

A detailed study on the influence of an external magnetic field on a symmetrical gyrotropic slab in terms of Goos-Hanchen (GH) phase shifts is presented. The GH phase shifts at both boundaries of the slab are calculated, and the guidance condition is explained by means of them. It is found that the external magnetic field destroys the spatial symmetry of the field distribution, and we use the concepts of `penetration' distance as well as effective thickness to illustrate the phenomenon. In term of the GH phase shifts, the spatial distribution of the time-average Poynting power is also derived. We find that influenced by the external magnetic field, the positive and negative time-average Poynting power along the waveguide direction can exist simultaneously in the gyrotropic medium, depending on the transverse position.

This paper presents a novel band-notched elliptical slot antenna for Ultra Wide-Band (UWB) communication, which is printed on a dielectric substrate of RT/duroid 6006 with relative permittivity (ε_r) of 6.0, thickness of 1.27 mm, and fed by an elliptical open ended microstrip line connected to the 50Ω main line. This antenna is designed to be used in frequency band of 3.1-10.6 GHz. Bandnotched characteristics of antenna to reject the frequency band of 5.15-5.825 GHz, which is limited by IEEE 802.11a, is realized by parasitic inverted-U strip attached to the elliptical slot plane. Effects of varying the parameters of parasitic inverted-U strip on performance of proposed antenna have been investigated. The antenna with optimal parameters obtained from parametric study is fabricated and measured. It is observed that the simulation and experimental results have good agreements with each other.

The near and far field properties of the large-scale metal plate with slit array are studied by applying the finite-difference timedomain (FDTD) method. The far region scattering properties at different incident angles are also discussed. We find out the enhanced optical transmission (EOT) through the metal plate with suitable placed narrow slit array is excited by the interaction of the surface plasmon polarization (SPP) and the Fabry-Perot resonance (FPR), and the dielectric substrate has significant influence on the transmission properties by affecting the electromagnetic field distribution on the metal-dielectric interface. Furthermore, the scattering field would be reduced and the transmission efficiency could be improved by the phase shift caused by the dielectric substrate. These unusual properties suggest possible applications to light-transparent metal contacts, stealth materials, etc.

When a microstrip patch antenna is brought closer than 0.2λ to an identical patch the resonant frequency of that antenna changes from the designed frequency. In this paper numerical results for the resonant frequency are presented from a theoretical analysis of the mutually coupled H-plane microstrip patch antennas with confirming experimental results. We have also established the relation between resonant frequency of E-plane coupled and H-plane coupled microstrip patch antennas.

In this paper, we present two pre-processing based techniques in unitary transform-domain for narrow-band interference rejection in CDMA communication systems. In our techniques, by using Karhaunen-Loeve Transform (KLT) and Discrete Fourier Transform (DFT), at the transmitter, eigenvectors occupied by NBI are determined; then the energy of the transmitted signal is set to zero into the direction of those determined vectors. Hence, any information is not deleted by NBI through channel. As a result after applying these transforms, a major part of the processing would be shifted to the transmitter, and thus complexity of receiver is reduced. Our simulation results show that the proposed methods improve the performance of the CDMA communication systems in the presence of narrow-band interference.

The resonant frequency of a microstrip patch (rectangular, square, and circular) changes as soon as an identical patch is brought closer than 0.2λ. Closed form expressions are presented for the E-plane coupled configuration from which this altered resonant frequency may be easily computed. These expressions may be readily used in the computer aided design of microstrip antenna arrays.

In this paper, we model an array of pyramid electromagnetic wave absorbers and calculate the return loss of this array using the FDTD method. For modeling the frequency dependent of the absorber, the Debye model is used. In doing so, a 3 × 3 structure of nine pyramid absorber is chosen instead of the array. The results are compared with capacitance and homogenization methods using average values for ε [10]. The results clearly show that the FDTD is an accurate method for calculating the return loss of an array of pyramid absorbers as compared with three other existing methods, and can be used to simulate the array of pyramid absorbers with different sizes in a wide range of frequencies.

This paper presents the result for antenna factor of microstrip patch antenna when used as electromagnetic interference (EMI) sensor. Antenna factor is an important parameter of a sensor used for EMI measurements. The microstrip antenna has found wide application as transmit and receive antenna in modern microwave systems. In this paper, a new application of microstrip antenna as EMI sensor is presented. The result for antenna factor versus frequency of a microstrip patch antenna is presented using commercial software CST Microwave Studio. Also the experimental results for a prototype antenna are presented and compared with the simulated result.

Based on the theory about charge moment tensor and the magnetic moment of a rotational charged body, and by means of Eulor's equation for a rotational rigid body in classic mechanics, the Lagrangian and the dynamic equation of a charged dielectric rigid body under a uniform magnetic field has been derived; Also two symmetric simple cases have been solved or analyzed under condition of slow rotation and no gravitation, the corresponding invariants have also been found.

In the recent years, extensive studies have been done to design space-time codes appropriate for communications over fading channels in multiple input-multiple output (MIMO)systems. Most of these designs have been based upon the assumption that the channel fading coefficients are uncorrelated hence independent jointly Gaussian random variables. Naturally the best strategy in such situations that the elements of the channel matrix are independent is to employ diversity techniques to combat the adverse effects of these fading media and thus the most famous space-time codes, i.e., orthogonal and trellis codes have been designed with an eye to realizing the maximum attainable diversity order in a MIMO system. In this paper, we will remove this almost ever-present yet practically difficult to meet condition and shall introduce a new linear space-time block code that due to having some inherent redundancy as well as diversity is wellsuited to correlated fading channels. We will discuss the properties of the proposed code, derive its maximum likelihood (ML) decoder and provide simulation results which show its superiority to the highly used orthogonal space-time block codes in a wide range of signal to noise ratios in correlated fading channels.

Diffraction of an electromagnetic plane wave from a slit in an impedance plane has been presented. The method is based on Maliuzhinets technique for impedance surfaces. Comparison of the field patterns with different values of the face impedance are also presented.

The matched filter (MF) is known as the fastest method for acquisition of DS-CDMA signals. Power consumption of the MF is a key issue for realizing multimedia hand-held terminals. We proposed a new Analog Matched Filter using Sample-and-Hold (S/H) circuit, which performs correlation between an input signal and a filtering coefficient employed for modulation in fully analog domain, eliminating the need to Analog-to-digital (A/D) conversion, so reduces power consumption and chip area. Simulation results reveal that the proposed circuit dissipates 2.3 mW power consumption at a chip rate of 16.7 MHz with 3.3 V power supply for 15 taps configuration. The proposed analog architecture could improve the performance of mobile terminals.

A new canonical scattering problem consisting of the propagation of the dominant TEM mode at the finite-length impedance discontinuity in the outer conductor of a coaxial waveguide is solved. The contributions from the successive impedance discontinuities are accounted for through the solution of a modified Wiener-Hopf equation. Some graphical results displaying the reflection and transmission characteristic are presented.

The performance of wideband radar system may be degraded by signal distortion occurring in anyplace of the transmission channel of the system. If the amplitude response is not flat or the signal delay is not constant in the transmission of the wideband signal, then signal distortion will occur, which can reduce the SNR and resolution. The available theory indicates that a small sinusoidal ripple variation in either amplitude-frequency or phase-frequency response of a linear system will cause signal distortion and the phenomena of paired echoes in the output signals of the time domain. In this paper, whether a dispersive transmission line with discontinuities will lead to the phenomena of paired echoes is discussed by means of finite difference time domain (FDTD) method and theoretical analysis. The results show that the technique of paired echoes is unsuited to analyze the influence of dispersive transmission line with discontinuities on time domain pulse signal. The method of Taylor series expansion shall be chosen as a more appropriate method. Meanwhile, simulations also show that a pulse signal transmitting in dispersive transmission lines with discontinuities including passive components such as filters and directional couplers will not lead to the phenomena of paired echoes.

Rain rate and rain attenuation predictions are one of the vital steps to be considered when analyzing a microwave satellite communication links at the Ku and Ka bands. In this paper, tools for the prediction of rain rate and rain attenuation are presented in the form of contour maps for Nigeria using a massive rainfall data bank of 30 years which are taken from measurements made from the coast to the arid region of Nigeria. Rain-rate maps for the country of Nigeria were developed using the models purposely designed for tropical zones while ITU-R models were used for the rain-attenuation maps. The information from these maps will be a good preliminary design tools for both terrestrial and earth-satellite microwave links and also provide a broad idea of rain attenuation for microwave engineers.