In this paper, the power dissipated through different loss mechanisms including dielectric, conductor and radiation loss is calculated for the substrate integrated waveguide (SIW) and modified substrate integrated waveguide (MSIW). The applied computational method being appropriate for structures with periodic conducting parts allows one to calculate the integrals corresponding to these powers analytically and with high accuracy.
In this paper the phase centre of a pure mode, smooth wall, conical horn is studied. The method employed uses phase information obtained by aperture integration of the phase corrected mode field but differs from earlier presentations in first reducing the radiation integrals in terms of an identified family of functions prior to integration. The result is formulas for the principal plane radiation patterns that better exemplify operation of the antenna. The procedure uses these formulas together with least squares minimization to determine a best fit phase centre for each principal plane. It is shown that contrary to published results, even in its principal planes, there is no unique phase centre that is a property of the horn alone. The use of such a horn as the feed element of a radio-optical antenna system is then considered. It is shown that in situations where cost is paramount and the well known drawbacks of its unequal principal plane beamwidths and the diminished gain that results from lackof a uniquely defined phase centre can be tolerated, perhaps contrary to conventional wisdom, the pure mode, smooth wall, conical horn does have a useful role to play. This is illustrated by a design example in which such a horn was used to feed a 6.4 m. dish working in X-band with a Gregorian feed system. The result is confirmation of the usefulness of the method presented here for location of a best fit phase centre.
Water bolus is used in microwave hyperthermia of cancer treatment to control the body surface temperature. In this paper the effect of water bolus on SAR distribution is investigated in the muscle layer of a three layered tissue model. Both the SAR penetration depth and the effective field size (EFS) are computed and compared in presence and in absence of the water bolus. Results are provided for distilled and fresh water with three different thicknesses of water bolus. All numerical simulations are performed using the Ansoft HFSS software. Numerical simulation results are in good agreement with published results.
On the base of the binary search algorithm of backtracking, an enhanced binary anti-collision search algorithm for radio frequency identification (RFID) system is presented in this paper. With the method of transferring the collision bit in place of the ID of the tag, the proposed algorithm can improve identification efficiency significantly. Mathematical simulation result shows that compared with the binary search algorithm, dynamic binary search algorithm and the binary search algorithm of backtracking, the proposed algorithm outperforms the three algorithms previous when handling multiple RFID tags simultaneously.
A fast and accurate near-field-far-field transformation technique with helicoidal scanning is proposed in this paper. It is tailored for elongated antennas, since a prolate ellipsoid instead of a sphere is considered as surface enclosing the antenna under test. Such an ellipsoidal modelling allows one to consider measurement cylinders with a diameter smaller than the antenna height, thus reducing the error related to the truncation of the scanning surface. Moreover, it is quite general, containing the spherical modelling as particular case, and allows a significant reduction of the number of the required nearfield data when dealing with elongated antennas. Numerical tests are reported for demonstrating the accuracy of the far-field reconstruction process and its stability with respect to random errors affecting the data.
Wireless channel identification and equalization is one of the most challenging tasks because broadcast channels are often subject to frequency selective, time varying fading and there are several bandwidth limitations. Furthermore, each receiver channel has vastly different types of channel characteristics and signals to noise ratio. Here in this paper we consider channel equalization and estimation problem from trans-receiver perspective, specifically we try to estimate blind equalization schemes particularly using constant modulus Algorithm (CMA). We try to estimate a linear channel model driven by a QAM source and adapt a FSE (T/2) using CMA. It has been shown CMA-FSE successfully reduces the cluster variance so that transfer to a decision directed mode is possible and simultaneously error is reduced.
The scattering characteristic of paraxial gaussian beam from two dimensional dielectric rough surfaces is studied in this paper. The modification of the Kirchhoff approximation theory for rough surface scattering by an incident gaussian beam instead of a plane wave are developed based on conventional Kirchhoff scattering theory and plane wave spectrum expansion method. The coherent and incoherent scattered intensity and cross section of two dimensional dielectric rough surfaces is derived in detail. As a application, under incidence wave length λ = 1.06 μm, we calculate the coherent and incoherent scattered intensity and cross section of Gaussian beam scattering from plating aluminium dielectric rough surfaces change with the scattering zenith angles in different rough surface correlation length, rough surface height root mean square and other conditions. In the same scattering conditions, we compare the coherent and incoherent scattered section between the gaussian beam and plane wave to prove that our methods and programming cods is correct. The numerical results are shown that the incident gaussian beam size is much larger compared with the surface height correlation length, the normalized scattering cross section is the same as for an incident plane wave. The ratio between the beam size and the surface height correlation length play an important role in the scattering characteristic of the gaussian beam from two dimensional dielectric rough surfaces. The ratio is bigger, the coherent and scattered intensity and section is more remarkable and on the contrary the incoherent scattered intensity and section is relatively smaller.
The paper describes the propagation of a thin laser beam which passes through a hot turbulent jet, perpendicularly to the flow direction, using geometrical optics approximation. From the modelling of the random propagation direction of the laser beam along its whole path, the diffusion coefficient of the turbulent jet is determined by means of a shape optimization technique in which a genetic algorithm is used. The results obtained from the GA are then improved by the Golden Section method.
A full wave spectral domain method of moment along with reciprocity theorem analysis of finite phased array of aperture coupled circular microstrip patch antennas is presented. Both the electric surface currents on the patches and the equivalent magnetic current on the apertures are considered. Results of reflection coefficient magnitude, active input impedance, active element gain, efficiency and pattern are provided for different array size and element separations. By optimizing the parameters of the array, a better scan performance can be achieved. Furthermore, a comparison is made between array of rectangular and circular patches, with equal patch surface area, and it is shown that the array of circular patches provide a better scan performance than the array of rectangular patches.
Based on theoretical calculations, the field intensity resulting from a transmitter of medium wave (waves propagation) enjoys a significant increase in the paths where ground conductivity increase and in special environmental conditions even if far away from the transmitter. This phenomenon distinguishes coverage areas of a transmitter from common procedures of determining coverage. This article examines and observes the above-mention issue and its results.
In this paper a novel approach based on Asymptotic Iteration Method (AIM) is presented to solve analytically the light propagation through one-dimensional inhomogeneous slab waveguide. Practically implemented optical slab waveguides based on traditional techniques are usually inhomogeneous and numerical methods are used to obtain guided wave characteristics. In this work, we develop analytical method for modal analysis includes Eigen modes (electric and magnetic fields distribution) and Eigen values (guided wave vector) using AIM. The developed method is applied to some especial examples.
The calculation method for radar cross-section (RCS) of reflector antenna placed under cone-shape dielectric radome has been proposed. The method based on the integral representations for a desired scattering field with using Lorenz lemma. These integral equations considered electromagnetic interaction between an antenna screen and a radome. The analysis of RCS calculation results for model antenna system with a conic dielectric radome has been carried out.
A theoretical analysis of a gap-coupled stacked annular ringmicrostrip antenna with superstrate is performed in order to obtain wider bandwidth operation. The effects of air gap, superstrate thickness and feedingp oint location on the antenna performance are analyzed in TM_{11} mode usingequiv alent circuit concept. It is noted that the proposed antenna is very sensitive to the feedingp oint location in TM_{11} mode while annular ringmicrostrip patch antenna is independent of feed point in that mode. The optimized proposed antenna shows an impedance bandwidth of 13.96% whereas the antenna without air-gap has 8.75% bandwidth and without superstrate it has bandwidth of 10.89%. The theoretical results are compared with simulated and experimental results.
A general formulation of Dyadic Green's function for a point source above a two-dimensional periodic boundary is presented in spectral form. This formulation is simplified by considering only the zero term of the infinite Floquet modes. Then it is applied to obtain the Dyadic Green's function of a printed source above a dielectric slab with periodically defected ground plane by using a generalized equivalent network of this defected ground plane. This equivalent network is obtained from the reflection coefficients of the defectedgrounded slab for different angles of incidence. This network includes equivalent impedances of the periodic surface for both TE and TM incident waves. In addition, it includes coupling impedance between the equivalent TE and TM networks. By determining the generalized equivalent network of the ground plane, the problem of the Green's function can be formulated by coupled TE and TM transmission line networks.
In this paper, RFID reader-to-reader interference is analyzed from the point of view of interrogation range. To evaluate RFID interference quantitatively, the new figure-of-merit, interrogation range reduction ratio (IRRR), is defined. In order to show the usefulness of IRRR, its value is calculated in various environments. Additionally, the calculated IRRR values are verified by measurements using two RFID readers and an RFID tag. IRRR can be referred to an important design parameter to analyze more complex interfering problems in instances of actual RFID system deployment.
This paper presents a general inequality for the grating lobes of the planar phased array, whether rectangular lattice or triangular lattice. And for the planar phased array with grating lobes, the maximum scanning angle is given.
The translational addition theorems for the spherical scalar and vector wave functions are derived in a novel, unified way based on the simple and well-known concepts of the radiation and incoming wave patterns. This approach makes the derivation simpler and more transparent compared to the previous approaches. As a result, we also obtain alternative and partly simpler expressions for the translation coefficients in the vector case.
In this paper, the angular side-play amount created by radiation pressure acting on active space object has been detailed investigated based on the physical optics, and the results are compared with the results by Mie theory; the correctness of the physical optics model is validated. The curves of angular side-play amount varied with the energy density of incident wave, mass of the object, and the angular between the direction of incident wave and initial velocity of the space etc. Using the results having been calculated, we analyzed the detectable conditions of angular side-play amount. A new method, which identifies different active object in space, has been taken out.
This article discusses the-state-of-the-art of the vaneloaded gyrotron traveling wave tube (gyro-TWT) amplifier, which is device of increasing importance for high resolution radar and high information density communication systems because of its high-power and broad bandwidth capabilities. Vane loading is identified as a means to achieve a low-beam energy, high-harmonic, low-magnetic field, mode-selective and stable operation of a gyro-TWT. Thus, the development of a simple approach to the analysis of the interaction structure of vane-loaded gyro-TWT has been identified as a problem of practical relevance.
A proposed sensor for landmines detection consists of two parallel microstrip antennas placed on the same ground plane and with defected ground structure between them has been investigated. The microstrip patch array with defected ground structure has the advantage of a low mutual coupling compared with the classic one. The Finite-Difference Time-Domain (FDTD) is used to simulate the sensor for landmines detection.
In this paper, the vector parabolic equation method (VPEM) is used to investigate the Shannon capacity of multiple-input multiple-output (MIMO) communication systems in indoor corridors. This deterministic three-dimensional (3-D) full-wave method is capable to demonstrate the effects of antennas and propagation environment on the channel capacity. The VPEM can model any field depolarization effects which are caused by the corridor walls. This method is particularly useful for evaluation of MIMO channel capacity in corridors with local narrowing of cross section. The channel capacity is computed for both single and hybrid polarizations and simulation results are compared with those obtained by the ray tracing method.
In this paper, a virtual cathode oscillator (VCO) is simulated based on FDTD algorithm. The geometrical structure is coaxial. Electromagnetic fields and current graphs are calculated. For the first time it has been shown that the delay between input pulse and output microwave signal originate from the waveguide transition delay time and the virtual cathode generation loop delay time.