H. Ragheb - Academia.edu (original) (raw)
Papers by H. Ragheb
IEEE Antennas and Propagation Society International Symposium 1997. Digest, 1997
The radiation from an open ended eccentric annular waveguide is examined here. The region between... more The radiation from an open ended eccentric annular waveguide is examined here. The region between the two circular conductors is assumed to have either symmetrical or anti-symmetrical TE field distribution. The cut-off wavenumber is first calculated and the unknown coefficients in the field are then obtained. It is found that for anti-symmetric field distribution the radiation pattern in the H-plane has a null which can be widely scanned by displacing the conducting core from the central axis. For the symmetrical field distribution a pair of symmetrical nulls in the E-plane are slightly scanned with the displacement of the conducting core. This type of waveguide antenna is useful for applications in phased and adaptive arrays which require null scanning
IEEE Antennas and Propagation Society International Symposium. 1996 Digest, 1996
ABSTRACT The cutoff wavenumbers of an eccentric dielectric loading a circular waveguide are calcu... more ABSTRACT The cutoff wavenumbers of an eccentric dielectric loading a circular waveguide are calculated. Analytical formulations are developed based on the boundary value method. The cutoff wavenumbers are then calculated as roots of the resulting characteristic determinant. Several examples for special cases are introduced for comparison followed by a general example
Radio Science, 1994
The scattering cross section of a dielectric elliptic cylinder coated with nonconfocal dielectric... more The scattering cross section of a dielectric elliptic cylinder coated with nonconfocal dielectric is investigated. An exact dual series solution based on the boundary value method and employing the addition theorem of Mathieu functions is derived. Both transverse magnetic and transverse electric cases are considered. The infinite series' of the solution are truncated after a finite number of terms to generate numerical data. A convergence check is built into the computer program, and the geometrical dimensions considered are within the low-frequency range. It is. shown that this solution is much more general than all other solutions given before because it can handle a variety of scattering geometries.
Proceedings of IEEE Antennas and Propagation Society International Symposium, 1993
ABSTRACT The boundary value method is used to derive a dual series solution of a plane wave incid... more ABSTRACT The boundary value method is used to derive a dual series solution of a plane wave incident on a dielectric coated conducting circular cylinder imbedded in a semicircular channel in a ground plane. The partial orthogonality of the trigonometric functions is used to obtain the scattering coefficients. The resulting infinite series is then truncated to a finite number of terms to produce numerical results. Special cases are first introduced for comparison with the corresponding published results. The comparison shows an excellent agreement in all cases. More general examples are then introduced.
Applied Computational Electromagnetics Society Journal
A microwave technique is used determine the liquid–gas ration inside the water/waste pipeline. Th... more A microwave technique is used determine the liquid–gas ration inside the water/waste pipeline. This technique is based on the change in the resonant frequency as the liquid gas ratio changes. The liquid layer height is then calibrated with the measured resonant frequency. This non-destructive technique is useful and highly accurate when the liquid layer is very thin. Experimental results agreed well with the predicted response.
Arabian Journal for Science and Engineering, 2014
IEEE Transactions on Microwave Theory and Techniques, 1995
... The author is with the Deptartment of Electrical Engineering, King Fahd IEEE Log Number 94107... more ... The author is with the Deptartment of Electrical Engineering, King Fahd IEEE Log Number 9410700. ... The total electric field in region 1 can be expressed as the sum of incident, reflected and diffracted electric fields, ie EL1) = EFr + Ez'f + x = E, [4jn Jrl(kr) sin 714, + A:"H!:)(X:r)] n=l ...
IEEE Transactions on Microwave Theory and Techniques, 2000
Arabian Journal for Science and Engineering, 2014
Anomalous weather conditions prevail in the Arab Gulf Area in the summer season as a result of th... more Anomalous weather conditions prevail in the Arab Gulf Area in the summer season as a result of the abnormal variations of the air temperature, pressure and relative humidity in the lower tropospherical area. These generate radio frequency refractive index N in space that deviates considerably from the standard atmospheric refractive index. Such anomaly in N could disrupt existing communication links rendering some links completely blind. In order to predict the form of the wave propagation in space and to identify locations of signal loss, complete spatial knowledge of N must be known. In this work, contours of N are presented covering vertically up to 1 km high and laterally the area around the Arab Gulf extending from Kuwait down to the Arab Emirates. Such contours are the result of data accumulated over 27 years. Further, limited representation of the communication coverage distribution under such weather anomaly is presented.
Cutoff wavenumbers corresponding to two circular dielectric cylinders loading a conducting circul... more Cutoff wavenumbers corresponding to two circular dielectric cylinders loading a conducting circular waveguide are investigated. An analytical solution based on boundary value method is employed here. Fields of hybrid modes were expressed in terms of local and global cylindrical coordinates specified in the geometry of the problem. The addition theorem of Bessel functions is then used to transfer the fields from one coordinate system to the other in order to apply the boundary conditions. A MATLAB computer program based on the analytical formulation is then developed to obtain numerical values for the cutoff wavenumbers for different geometrical parameters.
Microwaves, Antennas and Propagation, IEE Proceedings H
The scattering of a long dipole antenna field by many conducting infinitely long circular cylinde... more The scattering of a long dipole antenna field by many conducting infinitely long circular cylinders has many engineering applications, such as the simulation of a cylindrical reflector antenna by circular cylinders, in which the feed is a long dipole. The dipole field is considered as incident on the cylinders, resulting in multiply-scattered fields between the cylinders, as well as between each cylinder and the dipole. A self-consistent method is employed for calculating the multiply-scattered fields among the cylinders, while an iterative procedure is used for the multiple scattering between the cylinders and the dipole. Examples illustrating the radiation pattern of simulated parabolic cylindrical, and corner reflector, antennas are shown. The field of a long dipole antenna perturbed by one or two cylinders is given. The paper also shows how one can improve the simulated reflector pattern over the solid reflector by proper choice of the radii and positions of the simulating cylin...
IEEE Transactions on Antennas and Propagation, 1987
ABSTRACT A cylindrical reflector is simulated by N parallel circular conducting cylinders of arbi... more ABSTRACT A cylindrical reflector is simulated by N parallel circular conducting cylinders of arbitrary radius and distribution along the trajectory of the continuous reflector surface. The resulting radiation pattern of the transmitting reflector antenna is computed as the backscattering pattern of the circular cylinders due to a line source excitation. The results for large N are compared with published data for a cylindrical parabolic reflector by Kinzel and for a corner reflector by Tsai. It is shown that the beamwidth and first sidelobe level can be improved by using cylinders of unequal radii and spacing but that, contrary to expectation, further improvement by increasing the number of cylinders is not necessarily possible.
IEEE Transactions on Antennas and Propagation, 1983
ABSTRACT The inverse black body radiation, which is the problem of determining the area-temperatu... more ABSTRACT The inverse black body radiation, which is the problem of determining the area-temperature distribution of a black body from its measured radiated power spectrum, was recently solved by Bojarski. His solution employs the inverse Laplace transform to reconstruct the area-coldness distribution from an integral equation based on Planck's law. Our solution is similar but restricted to microwave frequencies and employs the Rayleigh-Jeans approximation to yield the corresponding portion of the area-coldness distribution using the inverse Laplace transform but avoiding the iterative procedure of Bojarski.
1986 Antennas and Propagation Society International Symposium, 1986
ABSTRACT First Page of the Article
Antennas and Propagation Society Symposium 1991 Digest, 1991
ABSTRACT Scattering from a perfectly conducting strip arbitrarily embedded inside a dielectric cy... more ABSTRACT Scattering from a perfectly conducting strip arbitrarily embedded inside a dielectric cylinder of circular or elliptical cross-section is investigated. Numerical results are obtained, and their accuracy is investigated for a variety of physical and electric parameters by comparing the scattered field pattern with numerical results obtained using other techniques. It is found that the numerical computations based on this analysis are rapidly convergent and few terms are needed to obtain reasonably accurate results
Digest on Antennas and Propagation Society International Symposium, 1989
A general solution for the scattering of a plane wave by nonconfocal dielectric-coated conducting... more A general solution for the scattering of a plane wave by nonconfocal dielectric-coated conducting elliptic cylinders is presented. To check the accuracy of the computation, the backscattering echo width of a plane wave incident on a dielectric-coated conducting circular cylinder is considered. The radius of the conducting cylinder is taken to be 0.15 λ, while the outer radius of the
IEEE Transactions on Antennas and Propagation - IEEE TRANS ANTENNAS PROPAGAT, 1987
ABSTRACT A modification to the Hamid-Ragheb approximation leads to a new approximate formula for ... more ABSTRACT A modification to the Hamid-Ragheb approximation leads to a new approximate formula for the Planck's radiation law valid at all frequencies. The modified regime is useful in solving the inverse black body radiation problem in closed form. The absolute percentage errors in constructing the area-coldness distribution due to the proposed and previous approximations are presented. The results suggest that our modified approximation to Planck's law is more suitable than all other approximations at all frequencies.
Journal of Electromagnetic Waves and Applications, 2001
The elliptical waveguide loaded with non-confocal metallic core was analyzed as a boundary value ... more The elliptical waveguide loaded with non-confocal metallic core was analyzed as a boundary value problem. An infinite determinant which represents the characteristic equation is obtained. To obtain the cutoff wavenumbers for both TE and TM cases of such a structure, the infinite determinant is truncated. Convergence when truncating was observed. Numerical results for the special case of suspended strip inside an elliptical waveguide is produced first, for comparison with published data. Results of other general cases are then presented.
International Journal of Electronics, 1985
The scattering pattern and back-scattering cross-section, due to an E-polarized plane wave incide... more The scattering pattern and back-scattering cross-section, due to an E-polarized plane wave incident on N circular parallel conducting cylinders in an arbitrary configuration, is computed by the boundary-value method. The results compare favourably for thin cylinders with an approximate solution based on an extension of the Karp–Russek technique for large separation between any two adjacent cylinders relative to the larger
IEEE Antennas and Propagation Society International Symposium 1997. Digest, 1997
The radiation from an open ended eccentric annular waveguide is examined here. The region between... more The radiation from an open ended eccentric annular waveguide is examined here. The region between the two circular conductors is assumed to have either symmetrical or anti-symmetrical TE field distribution. The cut-off wavenumber is first calculated and the unknown coefficients in the field are then obtained. It is found that for anti-symmetric field distribution the radiation pattern in the H-plane has a null which can be widely scanned by displacing the conducting core from the central axis. For the symmetrical field distribution a pair of symmetrical nulls in the E-plane are slightly scanned with the displacement of the conducting core. This type of waveguide antenna is useful for applications in phased and adaptive arrays which require null scanning
IEEE Antennas and Propagation Society International Symposium. 1996 Digest, 1996
ABSTRACT The cutoff wavenumbers of an eccentric dielectric loading a circular waveguide are calcu... more ABSTRACT The cutoff wavenumbers of an eccentric dielectric loading a circular waveguide are calculated. Analytical formulations are developed based on the boundary value method. The cutoff wavenumbers are then calculated as roots of the resulting characteristic determinant. Several examples for special cases are introduced for comparison followed by a general example
Radio Science, 1994
The scattering cross section of a dielectric elliptic cylinder coated with nonconfocal dielectric... more The scattering cross section of a dielectric elliptic cylinder coated with nonconfocal dielectric is investigated. An exact dual series solution based on the boundary value method and employing the addition theorem of Mathieu functions is derived. Both transverse magnetic and transverse electric cases are considered. The infinite series' of the solution are truncated after a finite number of terms to generate numerical data. A convergence check is built into the computer program, and the geometrical dimensions considered are within the low-frequency range. It is. shown that this solution is much more general than all other solutions given before because it can handle a variety of scattering geometries.
Proceedings of IEEE Antennas and Propagation Society International Symposium, 1993
ABSTRACT The boundary value method is used to derive a dual series solution of a plane wave incid... more ABSTRACT The boundary value method is used to derive a dual series solution of a plane wave incident on a dielectric coated conducting circular cylinder imbedded in a semicircular channel in a ground plane. The partial orthogonality of the trigonometric functions is used to obtain the scattering coefficients. The resulting infinite series is then truncated to a finite number of terms to produce numerical results. Special cases are first introduced for comparison with the corresponding published results. The comparison shows an excellent agreement in all cases. More general examples are then introduced.
Applied Computational Electromagnetics Society Journal
A microwave technique is used determine the liquid–gas ration inside the water/waste pipeline. Th... more A microwave technique is used determine the liquid–gas ration inside the water/waste pipeline. This technique is based on the change in the resonant frequency as the liquid gas ratio changes. The liquid layer height is then calibrated with the measured resonant frequency. This non-destructive technique is useful and highly accurate when the liquid layer is very thin. Experimental results agreed well with the predicted response.
Arabian Journal for Science and Engineering, 2014
IEEE Transactions on Microwave Theory and Techniques, 1995
... The author is with the Deptartment of Electrical Engineering, King Fahd IEEE Log Number 94107... more ... The author is with the Deptartment of Electrical Engineering, King Fahd IEEE Log Number 9410700. ... The total electric field in region 1 can be expressed as the sum of incident, reflected and diffracted electric fields, ie EL1) = EFr + Ez'f + x = E, [4jn Jrl(kr) sin 714, + A:"H!:)(X:r)] n=l ...
IEEE Transactions on Microwave Theory and Techniques, 2000
Arabian Journal for Science and Engineering, 2014
Anomalous weather conditions prevail in the Arab Gulf Area in the summer season as a result of th... more Anomalous weather conditions prevail in the Arab Gulf Area in the summer season as a result of the abnormal variations of the air temperature, pressure and relative humidity in the lower tropospherical area. These generate radio frequency refractive index N in space that deviates considerably from the standard atmospheric refractive index. Such anomaly in N could disrupt existing communication links rendering some links completely blind. In order to predict the form of the wave propagation in space and to identify locations of signal loss, complete spatial knowledge of N must be known. In this work, contours of N are presented covering vertically up to 1 km high and laterally the area around the Arab Gulf extending from Kuwait down to the Arab Emirates. Such contours are the result of data accumulated over 27 years. Further, limited representation of the communication coverage distribution under such weather anomaly is presented.
Cutoff wavenumbers corresponding to two circular dielectric cylinders loading a conducting circul... more Cutoff wavenumbers corresponding to two circular dielectric cylinders loading a conducting circular waveguide are investigated. An analytical solution based on boundary value method is employed here. Fields of hybrid modes were expressed in terms of local and global cylindrical coordinates specified in the geometry of the problem. The addition theorem of Bessel functions is then used to transfer the fields from one coordinate system to the other in order to apply the boundary conditions. A MATLAB computer program based on the analytical formulation is then developed to obtain numerical values for the cutoff wavenumbers for different geometrical parameters.
Microwaves, Antennas and Propagation, IEE Proceedings H
The scattering of a long dipole antenna field by many conducting infinitely long circular cylinde... more The scattering of a long dipole antenna field by many conducting infinitely long circular cylinders has many engineering applications, such as the simulation of a cylindrical reflector antenna by circular cylinders, in which the feed is a long dipole. The dipole field is considered as incident on the cylinders, resulting in multiply-scattered fields between the cylinders, as well as between each cylinder and the dipole. A self-consistent method is employed for calculating the multiply-scattered fields among the cylinders, while an iterative procedure is used for the multiple scattering between the cylinders and the dipole. Examples illustrating the radiation pattern of simulated parabolic cylindrical, and corner reflector, antennas are shown. The field of a long dipole antenna perturbed by one or two cylinders is given. The paper also shows how one can improve the simulated reflector pattern over the solid reflector by proper choice of the radii and positions of the simulating cylin...
IEEE Transactions on Antennas and Propagation, 1987
ABSTRACT A cylindrical reflector is simulated by N parallel circular conducting cylinders of arbi... more ABSTRACT A cylindrical reflector is simulated by N parallel circular conducting cylinders of arbitrary radius and distribution along the trajectory of the continuous reflector surface. The resulting radiation pattern of the transmitting reflector antenna is computed as the backscattering pattern of the circular cylinders due to a line source excitation. The results for large N are compared with published data for a cylindrical parabolic reflector by Kinzel and for a corner reflector by Tsai. It is shown that the beamwidth and first sidelobe level can be improved by using cylinders of unequal radii and spacing but that, contrary to expectation, further improvement by increasing the number of cylinders is not necessarily possible.
IEEE Transactions on Antennas and Propagation, 1983
ABSTRACT The inverse black body radiation, which is the problem of determining the area-temperatu... more ABSTRACT The inverse black body radiation, which is the problem of determining the area-temperature distribution of a black body from its measured radiated power spectrum, was recently solved by Bojarski. His solution employs the inverse Laplace transform to reconstruct the area-coldness distribution from an integral equation based on Planck's law. Our solution is similar but restricted to microwave frequencies and employs the Rayleigh-Jeans approximation to yield the corresponding portion of the area-coldness distribution using the inverse Laplace transform but avoiding the iterative procedure of Bojarski.
1986 Antennas and Propagation Society International Symposium, 1986
ABSTRACT First Page of the Article
Antennas and Propagation Society Symposium 1991 Digest, 1991
ABSTRACT Scattering from a perfectly conducting strip arbitrarily embedded inside a dielectric cy... more ABSTRACT Scattering from a perfectly conducting strip arbitrarily embedded inside a dielectric cylinder of circular or elliptical cross-section is investigated. Numerical results are obtained, and their accuracy is investigated for a variety of physical and electric parameters by comparing the scattered field pattern with numerical results obtained using other techniques. It is found that the numerical computations based on this analysis are rapidly convergent and few terms are needed to obtain reasonably accurate results
Digest on Antennas and Propagation Society International Symposium, 1989
A general solution for the scattering of a plane wave by nonconfocal dielectric-coated conducting... more A general solution for the scattering of a plane wave by nonconfocal dielectric-coated conducting elliptic cylinders is presented. To check the accuracy of the computation, the backscattering echo width of a plane wave incident on a dielectric-coated conducting circular cylinder is considered. The radius of the conducting cylinder is taken to be 0.15 λ, while the outer radius of the
IEEE Transactions on Antennas and Propagation - IEEE TRANS ANTENNAS PROPAGAT, 1987
ABSTRACT A modification to the Hamid-Ragheb approximation leads to a new approximate formula for ... more ABSTRACT A modification to the Hamid-Ragheb approximation leads to a new approximate formula for the Planck's radiation law valid at all frequencies. The modified regime is useful in solving the inverse black body radiation problem in closed form. The absolute percentage errors in constructing the area-coldness distribution due to the proposed and previous approximations are presented. The results suggest that our modified approximation to Planck's law is more suitable than all other approximations at all frequencies.
Journal of Electromagnetic Waves and Applications, 2001
The elliptical waveguide loaded with non-confocal metallic core was analyzed as a boundary value ... more The elliptical waveguide loaded with non-confocal metallic core was analyzed as a boundary value problem. An infinite determinant which represents the characteristic equation is obtained. To obtain the cutoff wavenumbers for both TE and TM cases of such a structure, the infinite determinant is truncated. Convergence when truncating was observed. Numerical results for the special case of suspended strip inside an elliptical waveguide is produced first, for comparison with published data. Results of other general cases are then presented.
International Journal of Electronics, 1985
The scattering pattern and back-scattering cross-section, due to an E-polarized plane wave incide... more The scattering pattern and back-scattering cross-section, due to an E-polarized plane wave incident on N circular parallel conducting cylinders in an arbitrary configuration, is computed by the boundary-value method. The results compare favourably for thin cylinders with an approximate solution based on an extension of the Karp–Russek technique for large separation between any two adjacent cylinders relative to the larger