Aladin Kamel

UWB antipodal vivaldi antennas with protruded dielectric rods for higher gain, symmetric patterns and minimal phase center variations

In this paper, the authors proposed a technique to improve the gain, narrow the H-plane beamwidth, and minimize the phase center variations with frequency by utilizing Vivaldi antenna with a protruded dielectric rod. A sample antenna was fabricated and measured, and preliminary measured results are very promising, and in good agreement with the simulation results.

Electromagnetic fields in the presence of an infinite dielectric wedge

Electromagnetic fields excited by a line source in the presence of an infinite dielectric wedge with refractive index N are determined by application of the Kontorovich–Lebedev transform. Singular integral equations for spectral functions are solved by perturbation procedure, and the solution is obtained in the form of a Neumann series in powers of . The devised numerical scheme permits evaluation of the higher-order terms and, thus, extends the perturbation solution to values of N not necessarily close to unity. Asymptotic approximations for the near and far fields inside and outside the dielectric wedge are derived. The combination of the Neumann-type expansion of the transform functions with the representation of the field as a Bessel function series extends solutions derived with the Kontorovich–Lebedev method to the case of real-valued wavenumbers and arbitrarily positioned source and observer. Numerical results showing the influence of wedges with various values of dielectric and magnetic constants on the directivity of a line source are presented and verified through finite-difference frequency-domain simulations.

Microwave Bessel Beams Generation Using Guided Modes

A novel method is devised for Bessel beams generation in the microwave regime. The beam is decomposed in terms of a number of guided transverse electric modes of a metallic waveguide. Modal expansion coefficients are computed from the modal power orthogonality relation. Excitation is achieved by means of a number of inserted coaxial loop antennas, whose currents are calculated from the excitation coefficients of the guided modes. The efficiency of the method is evaluated and its feasibility is discussed. Obtained results can be utilized to practically realize microwave Bessel beam launchers.

A highly efficient Vivaldi antenna array design on thick substrate and fed by SIW structure with integrated GCPW feed

A compact Vivaldi antenna array printed on thick substrate and fed by a substrate integrated waveguide (SIW) structure is presented here. The array utilizes an SIW binary splitter to significantly minimize the feed structure insertion losses. Meanwhile, the splitter is fed with an integrated CPW to sustain a good input match and prevent higher order modes excitation over wide band operation. Extensive simulation and measurements were carried out and was presented here with a comparison to previously developed arrays.

Analysis and Design of Wide-Scan Angle Wide-Band Phased Arrays of Substrate-Integrated Cavity-Backed Patches

A class of wide-scan angle wide-band microstrip patch phased arrays is proposed. The proposed phased arrays are composed of probe-fed microstrip patches backed by substrate-integrated cavities. First, a simplified 2-D numerical analysis based on Floquets theorem is presented to qualitatively demonstrate the E-plane scan performance of the cavity-backed structure compared to that of the conventional microstrip patch phased array. Second, the 3-D scan performance of the proposed phased arrays is thoroughly investigated varying both the substrate thickness and dielectric constant using commercially available EM simulation tools, which is followed by presenting simple design guidelines for the cavity, patch and substrate. A 7 × 7 prototype phased array of the proposed SIW cavity-backed patch structure was fabricated and its measured results agree well with our theoretical prediction and indicate a relatively wide-scan performance when compared to the corresponding microstrip patch phased array without cavities.

Experimental development of a circularly polarized antipodal tapered slot antenna using SIW feed printed on thick substrate

In this paper, we propose a SIW fed circularly polarized (CP) tapered slot antenna which have a good return loss and a wide band axial-ratio. The performance of the antenna has been extensively optimized based on both CST Microwave Studio and Ansoft-HFSS simulation to obtain wide band CP operation. In the following sections, we introduce the theory of operation, the details of the design and the measured results.

On the use of Kontorovich-Lebedev transform in electromagnetic diffraction by an impedance cone

We consider the boundary-value problem for the Helmholtz equation connected with an infinite circular cone with an impedance boundary on its face. The scheme of solution includes applying the Kontorovich-Lebedev (KL) transform to reduce the problem to that of a KL spectral amplitude function satisfying a singular integral equation of the non-convolution type with a variable coefficient. The singularities of the spectral function are deduced and representations for the field at the tip of the cone and in the near and far field regions are given together with the conditions of validity of these representations.

Network theoretical transient analysis of signal transmission over evanescent modes

A network theoretical transient analysis of waveguide transmission of modulated signals with carrier frequencies below cutoff is presented. Both matched and mismatched terminations are considered. It is clearly shown that recent publications reporting on signal transmission faster than c (light velocity in free space) are based on erroneous interpretations of the measured results. It is also shown that the information capacity of tunneling systems is extremely low, which makes their use as communication channels unfavorable. A number of numerical experiments has been carried out. The achieved results justify the presented analysis and give the proper interpretations to the seemingly faster-than-c transmission reported recently.

Electromagnetic fields in the presence of an infinite metamaterial wedge

Electromagnetic fields, excited by an electric line source in the presence of an infinite metamaterial wedge, are determined by application of the Kontorovich–Lebedev transform. Uncoupled singular integral equations for the spectral functions are derived and a numerical scheme is devised and implemented to solve them. Numerical results showing the influence of a metamaterial wedge presence on the directivity of a line source are presented and verified through finite-difference frequency-domain simulations.

Microcontroller based neural network for landmine detection using magnetic gradient data

Landmines are affecting the live and livelihood of millions of people around the world. In this paper, we have developed a new method for detection of landmines using Hopfield neural network as applied to gradiometer magnetic data. The Hopfield Neural Network is used to optimize the magnetic moment of dipole source representing the landmine at regular locations. For each location, Hopfield neural network reaches its stable energy state. The location of the landmine corresponds to the location yielding the minimum Hopfield energy. Output results include position in two dimensions, horizontal location and depth of the landmine. Furthermore, the proposed algorithm was implemented on a microcontroller, to be suitable for real time detection. Theoretical and actual field examples prove the effectiveness of using the microcontroller based Hopfield neural network as an objective tool for detection of landmines.