Mahmoud Fallah | Iran University of Science and Technology (IUST) (original) (raw)
Fields of interest:
Metamaterials, Metasurfaces, Wave propagation, Advanced Materials, Frequency Selective Surface, Numerical Calculations, Numerical Method, FDTD, MOM, Moment method, Slot array antenna, slotted waveguide antenna, metamaterial, metasurface, scattering, electromagnetic, fields and wave, finite difference time domain, Finite-difference time-domain, numerical calculation, FSS, meta-waveguide, metawaveguide, patch-strip, Analytical method, unit cell, Anisotropic Media, impedance surface, impedance boundary, inhomogeneous media, periodic structure, antenna, microwave, Computational Electromagnetics, waveguide, rectangular waveguide, electromagnetic source, Line Source Excitation, PEMC, Coated Cylinder, reflect-array antennas, computer-aided, Fabry-Perot, cavity antennas, equivalent circuit , Electromagnetic Waves, Non-Homogeneous
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Papers by Mahmoud Fallah
Journal of Microwaves, Optoelectronics and Electromagnetic Applications, 2019
In this paper, a new multiband fractal frequency selective surface (MF-FSS) is proposed. The work... more In this paper, a new multiband fractal frequency selective surface (MF-FSS) is proposed. The work presents a new fractal design methodology for FSSs with Swastika fractal patch elements. The proposed MF-FSS includes periodic arrays of metallic patches, printed on a single layer substrate. The structure parametric analysis is carried out in terms of fractal iterations, geometry elements, and unit-cell size. The simple controllable feature of the proposed structure lets us tune the given parameters of FSS geometry to achieve adjustable bandstop filter. The fractal geometry allows us to design compact structures (CP = 54%) that behave like dual-polarized bandstop filters. The designed structure is validated by means of an excellent agreement between the simulation and measurement results. Also, results show the proposed structure presents the most desirable features like fractal compactness, multiband response, dual polarization, excellent angular stability, and controllability. This work presents a fundamental structure that can be applied into the more complex and sophisticated designs in future.
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Journal of Microwaves, Optoelectronics and Electromagnetic Applications, 2018
Researchers have always been in favor of path loss calculation in different media for application... more Researchers have always been in favor of path loss calculation in different media for applications such as telecommunication link design. Wave propagation calculations in large spaces using the FDTD method is time-consuming and imposes a great computational burden. For this reason, to replace the classical FDTD method for wave propagation simulation and path loss calculation in large spaces, optimized methods, namely TDWP, have been provided. In this paper, the use of the TDWP method for wave propagation simulation and path loss calculation above a terrain is investigated. Longitudinal components of ground-waves are taken into account (including direct waves, ground reflections, and surface waves). Propagation space is longitudinally divided into smaller FDTD windows with finite length. The electromagnetic pulse travels through these windows from left to right to the desired point. But despite its capability in reducing computational burden and increasing processing speed, TDWP has lower precision in instantaneous field simulation and calculation of propagation coefficients, so that results obtained from FDTD and TDWP are clearly different. In this paper, some efficient methods are proposed, which yield an increase in method accuracy.
Bookmarks Related papers MentionsView impact
AEU - International Journal of Electronics and Communications, 2018
this paper presents a comprehensive and accurate algorithm based on circuit model to design refle... more this paper presents a comprehensive and accurate algorithm based on circuit model to design reflect-array antennas (RAAs). The proposed algorithm can extract geometry of RAA structure corresponding to radiation parameters without employing any approximation or optimization intervention into the algorithm. Simulation results for some comprehensive examples, verify the validity of the proposed algorithm. This method is simple, fast, accurate, and can be expanded to all species of RAAs with arbitrary geometries. One of the main problems confronted in RAAs is low bandwidth characteristics. To attain wide bandwidth, we exploited the proposed algorithm with combination of multi-layer design of RAAs and subwavelength element. Convergence is observed between simulation and fabrication results, asserting good accuracy in method. In 10-15 GHz band, the maximum gain and-1dB bandwidth of two-layer antenna is 31.4 dB and 18.5%, respectively.
Bookmarks Related papers MentionsView impact
International Journal of Microwave and Wireless Technologies, 2019
This paper presents a novel concept named meta-waveguide structures to design slot array antennas... more This paper presents a novel concept named meta-waveguide structures to design slot array antennas based on metasurface. The proposed method investigates the geometrical parameters of the embedded metasurface and their relations to build up the engineered electric and magnetic fields to introduce efficient slot array antennas. This approach eliminates the necessity of using the well-known offsets in typical slot arrays, which can be benefited from linear array theorem. This idea is realized by employing successive filed curvature along the propagation direction, utilizing periodic metasurfaces. Thereafter, a step-by-step algorithm is recommended to design an efficient slot array antenna. Finally, a prototype is fabricated and tested experimentally validating the theoretical calculations.
Bookmarks Related papers MentionsView impact
Electromagnetics, 2014
This article introduces analytical formulas to obtain frequency response for a periodic array of ... more This article introduces analytical formulas to obtain frequency response for a periodic array of hexagon metallic patches and strip cells. The validity of analytic expressions obtained from analysis is verified using full-wave simulations. The formulas are then employed for designing a first-order bandpass frequency selective surface. The proposed frequency selective surface is composed of a periodic array of metallic patches separated by thin air gaps backed by a wire mesh having the same periodicity. The array of metallic patches and the wire mesh constitute a capacitive surface and a coupled inductive surface, respectively, which together act as a resonant structure in the path of an incident plane wave. The frequency response of the proposed frequency selective surface is obtained for various angles of incidence. Moreover, principles of operation, detailed synthesis procedure, and designing guideline for this type of frequency selective surface are presented and discussed in this article.
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AEU - International Journal of Electronics and Communications, 2019
This paper presents Metawaveguide in designing slot antenna array based on Metasurface. The tange... more This paper presents Metawaveguide in designing slot antenna array based on Metasurface. The tangential components of the electric field do not have the obligation of being vanished on waveguide boundary. The proposed method studies Geometrical parameters relations' of two specific Metasurface and inner Electrical fields of Metawaveguide in designing slot antenna array. This approach eliminates the need for the offset of slot array which can be benefited from linear array theory. This idea realized by successive filed curvature in the direction of wave propagation in the Metawaveguide by the means of periodic elements on Metasurface. Finally, the step by step flowchart of slot array antenna design has been proposed. A slotted Metawaveguide is fabricated at frequency 10 GHz and then tested.
Bookmarks Related papers MentionsView impact
Applied Computational Electromagnetics Society Journal, 2016
An analytical solution is presented for line source excitation of a cylinder with perfect electro... more An analytical solution is presented for line source excitation of a cylinder with perfect electromagnetic conductor (PEMC) core which is coated with multilayer anisotropic materials. Exact solution is presented using analytical relations for scattering from cylindrical structures. For multilayer structures, we have to calculate the inverse of a matrix which is sparse, thus, we use recursive relations to calculate the fields. A recursive relation for solving the problem with PEMC boundary condition is presented. Finally, some examples are given using this method and the results are compared and validated with the simulation results and other works. The advantage of analytical relation proposed in this paper is much less run time compared to numerical simulation.
Bookmarks Related papers MentionsView impact
Microwave Opt. Technol. Lett., 2016
In this article, a new approach (not new technique) was introduced for designing frequency select... more In this article, a new approach (not new technique) was introduced for designing frequency selective surfaces (FSSs). They tried to compose the desired frequency response using the frequency response of each constituent FSS. Also, a new dual-band miniaturized frequency selective surface was proposed.
Bookmarks Related papers MentionsView impact
Iranian Journal of Electrical and Electronic Engineering, 2019
An intelligent design method of double screen frequency selective surfaces (FSSs) is addressed in... more An intelligent design method of double screen frequency selective surfaces (FSSs) is addressed in this paper. The employed unit cell is composed of two metallic screens, which are printed on both sides of a substrate. The presented non-trial-and-error approach is investigated based on the separate design of each screen. With the help of some physical intuition and an equivalent circuit model, it is shown that the conventional use of complement geometries restricts the final desired filtering response. Therefore, unlike the previous studies, the metallic screens are not geometrically complementary in this paper. An excellent agreement between the full-wave simulations and corresponding equivalent circuit models has been observed. Using standard lumped elements, a highly selective miniaturized FSS (0.06λ0 ~ 0.08λ0) with two closely-spaced pass bands is designed, for GSM and WLAN frequencies. Simulation results show a dual-polarized characteristic with a good angular stability performance for the proposed structure.
Bookmarks Related papers MentionsView impact
Journal of Microwaves, Optoelectronics and Electromagnetic Applications, 2019
In this paper, a new multiband fractal frequency selective surface (MF-FSS) is proposed. The work... more In this paper, a new multiband fractal frequency selective surface (MF-FSS) is proposed. The work presents a new fractal design methodology for FSSs with Swastika fractal patch elements. The proposed MF-FSS includes periodic arrays of metallic patches, printed on a single layer substrate. The structure parametric analysis is carried out in terms of fractal iterations, geometry elements, and unit-cell size. The simple controllable feature of the proposed structure lets us tune the given parameters of FSS geometry to achieve adjustable bandstop filter. The fractal geometry allows us to design compact structures (CP = 54%) that behave like dual-polarized bandstop filters. The designed structure is validated by means of an excellent agreement between the simulation and measurement results. Also, results show the proposed structure presents the most desirable features like fractal compactness, multiband response, dual polarization, excellent angular stability, and controllability. This work presents a fundamental structure that can be applied into the more complex and sophisticated designs in future.
Bookmarks Related papers MentionsView impact
International Journal of Electronics and Communications (AEÜ), 2018
This paper presents a comprehensive and accurate algorithm based on circuit model to design refle... more This paper presents a comprehensive and accurate algorithm based on circuit model to design reflect-array antennas (RAAs). The proposed algorithm can extract geometry of RAA structure corresponding to radiation parameters without employing any approximation or optimization intervention into the algorithm. Simulation results for some comprehensive examples, verify the validity of the proposed algorithm. This method is simple, fast, accurate, and can be expanded to all species of RAAs with arbitrary geometries. One of the main problems confronted in RAAs is low bandwidth characteristics. To attain wide bandwidth, we exploited the proposed algorithm with combination of multi-layer design of RAAs and subwavelength element. Convergence is observed between simulation and fabrication results, asserting good accuracy in method. In 10–15 GHz band, the maximum gain and-1dB bandwidth of two-layer antenna is 31.4 dB and 18.5%, respectively.
Bookmarks Related papers MentionsView impact
International Journal of Electronics and Communications (AEÜ), 2018
In this paper, a fast, robust and accurate computer-aided procedure for design and analysis of hi... more In this paper, a fast, robust and accurate computer-aided procedure for design and analysis of highly efficient metasurface-assisted Fabry-Perot cavity antennas (FPCAs) is proposed. The automatic design algorithm is based on the equivalent circuit model (ECM) and it is capable of predicting the performances of FPCAs whose lateral walls are covered with a perfect electric conductor (PEC). In addition, it wipes out the computational burden arising from trial-and-error steps appearing in the conventional design techniques. As a prototype, according to the proposed design algorithm, a high gain FPCA with extremely high aperture efficiency is designed and fabricated for wireless applications. The equivalent circuit of the employed metasurface-based PRS is modified to enhance the accuracy of extracting the phase and magnitude of its reflection coefficient. To obtain the structural parameters of PRS, a hybrid optimization is applied to the proposed ECM. Simulated results show a maximum directivity of 18.6 dBi at 5.8 GHz leading to a high aperture efficiency of 126%. Experimental measurements on the fabricated prototype are also presented and the results confirm the theoretical and numerical predictions. The proposed design method is general and can be extended for other similar FPCA types exhibiting dual-, multi-and wide-band performances.
Bookmarks Related papers MentionsView impact
Journal of Microwaves, Optoelectronics and Electromagnetic Applications, 2016
A full-wave analytical method using the addition theorems and Hertzian potential functions are us... more A full-wave analytical method using the addition theorems and Hertzian potential functions are used to compute the radar cross section of a sphere coated by several layers composed of common materials and metamaterials. The minimization and maximization of radar cross section of a perfectly electric conductor sphere with such coatings are realized in a frequency band-width and in a wide interval of angles. One of the novelities of this contribution is, taking into dispersion relations of physically realizable metamaterials. So that the optimization procedure for RCS reduction is applied due to the coefficients describing dispersion characteristics. The method of least square is used for the design of a class of radar absorbing materials. The minimization of the error functions are performed by the combination of genetic algorithm and conjugate gradient method. It is shown that the proposed method of computation of radar cross section and its extremization effectively leads to the design of dispersive and isotropic metamaterials for the realization of radar absorbing materials.
Bookmarks Related papers MentionsView impact
Journal of Microwaves, Optoelectronics and Electromagnetic Applications, 2018
Researchers have always been in face of path loss calculation in different media for applications... more Researchers have always been in face of path loss calculation in different media for applications such as telecommunication link design. Wave propagation calculations in large spaces using the FDTD method is time-consuming and imposes a great computational burden. For this reason, to replace the classical FDTD method for wave propagation simulation and path loss calculation in large spaces, optimized methods, namely TDWP, have been provided. In this paper, the use of the TDWP method for wave propagation simulation and path loss calculation above a terrain is investigated. Longitudinal components of ground-waves are taken into account (including direct waves, ground reflections, and surface waves). Propagation space is longitudinally divided into smaller FDTD windows with finite length. The electromagnetic pulse travels through these windows from left to right to the desired point. But despite its capability in reducing computational burden and increasing processing speed, TDWP has lower precision in instantaneous field simulation and calculation of propagation coefficients, so that results obtained from FDTD and TDWP are clearly different. In this paper, some efficient methods are proposed, which yield an increase in method accuracy.
Bookmarks Related papers MentionsView impact
Journal of Communications Technology and Electronics, 2014
In this paper, using the method of moments to calculate the current density and monostatic and b... more In this paper, using the method of moments to calculate the current density and monostatic and
bi-static radar cross section of an unlimited strip by a non-homogeneous impedance. Here, incident wave is a plane wave. To authenticate the method, using the iterative method to solve the integral equations is engaged. Simulation results show that the surface with non- homogeneous impedance has reduced or increase in potential for bi- and mono-static radar cross section in certain azimuth.
Bookmarks Related papers MentionsView impact
Journal of Microwaves, Optoelectronics and Electromagnetic Applications , 2015
In this article, a high-order frequency selective band-stop EMC (electromagnetic compatibility) s... more In this article, a high-order frequency selective band-stop EMC (electromagnetic compatibility) shield is designed using multilayer square loop while each loop resonates at the specific desired frequency. The glass material is picked out as the preferred substrate for the designing process. In contrast to the computationally intensive numerical approaches (software), the equivalent circuit model offers a simple alternative method in FSS (frequency selective surface) analyses which is useful for quickly predicting the performance of FSS. The proposed FSS can be synthesized based on microwave filter theory and the synthesized FSS can control transmission-zero frequencies. A three zero-transmission transparent window is designed using the proposed method, in which 30dB insertion loss is achieved for 6 to 10 GHz bandwidth and optical opacity of the structure is 85%. The response of the analytical model is compared with the results of full-wave simulation. As a result, it predicts quite well the resonant frequencies of the designed FSS.
Bookmarks Related papers MentionsView impact
Journal of Microwaves, Optoelectronics and Electromagnetic Applications, 2019
In this paper, a new multiband fractal frequency selective surface (MF-FSS) is proposed. The work... more In this paper, a new multiband fractal frequency selective surface (MF-FSS) is proposed. The work presents a new fractal design methodology for FSSs with Swastika fractal patch elements. The proposed MF-FSS includes periodic arrays of metallic patches, printed on a single layer substrate. The structure parametric analysis is carried out in terms of fractal iterations, geometry elements, and unit-cell size. The simple controllable feature of the proposed structure lets us tune the given parameters of FSS geometry to achieve adjustable bandstop filter. The fractal geometry allows us to design compact structures (CP = 54%) that behave like dual-polarized bandstop filters. The designed structure is validated by means of an excellent agreement between the simulation and measurement results. Also, results show the proposed structure presents the most desirable features like fractal compactness, multiband response, dual polarization, excellent angular stability, and controllability. This work presents a fundamental structure that can be applied into the more complex and sophisticated designs in future.
Bookmarks Related papers MentionsView impact
Journal of Microwaves, Optoelectronics and Electromagnetic Applications, 2018
Researchers have always been in favor of path loss calculation in different media for application... more Researchers have always been in favor of path loss calculation in different media for applications such as telecommunication link design. Wave propagation calculations in large spaces using the FDTD method is time-consuming and imposes a great computational burden. For this reason, to replace the classical FDTD method for wave propagation simulation and path loss calculation in large spaces, optimized methods, namely TDWP, have been provided. In this paper, the use of the TDWP method for wave propagation simulation and path loss calculation above a terrain is investigated. Longitudinal components of ground-waves are taken into account (including direct waves, ground reflections, and surface waves). Propagation space is longitudinally divided into smaller FDTD windows with finite length. The electromagnetic pulse travels through these windows from left to right to the desired point. But despite its capability in reducing computational burden and increasing processing speed, TDWP has lower precision in instantaneous field simulation and calculation of propagation coefficients, so that results obtained from FDTD and TDWP are clearly different. In this paper, some efficient methods are proposed, which yield an increase in method accuracy.
Bookmarks Related papers MentionsView impact
AEU - International Journal of Electronics and Communications, 2018
this paper presents a comprehensive and accurate algorithm based on circuit model to design refle... more this paper presents a comprehensive and accurate algorithm based on circuit model to design reflect-array antennas (RAAs). The proposed algorithm can extract geometry of RAA structure corresponding to radiation parameters without employing any approximation or optimization intervention into the algorithm. Simulation results for some comprehensive examples, verify the validity of the proposed algorithm. This method is simple, fast, accurate, and can be expanded to all species of RAAs with arbitrary geometries. One of the main problems confronted in RAAs is low bandwidth characteristics. To attain wide bandwidth, we exploited the proposed algorithm with combination of multi-layer design of RAAs and subwavelength element. Convergence is observed between simulation and fabrication results, asserting good accuracy in method. In 10-15 GHz band, the maximum gain and-1dB bandwidth of two-layer antenna is 31.4 dB and 18.5%, respectively.
Bookmarks Related papers MentionsView impact
International Journal of Microwave and Wireless Technologies, 2019
This paper presents a novel concept named meta-waveguide structures to design slot array antennas... more This paper presents a novel concept named meta-waveguide structures to design slot array antennas based on metasurface. The proposed method investigates the geometrical parameters of the embedded metasurface and their relations to build up the engineered electric and magnetic fields to introduce efficient slot array antennas. This approach eliminates the necessity of using the well-known offsets in typical slot arrays, which can be benefited from linear array theorem. This idea is realized by employing successive filed curvature along the propagation direction, utilizing periodic metasurfaces. Thereafter, a step-by-step algorithm is recommended to design an efficient slot array antenna. Finally, a prototype is fabricated and tested experimentally validating the theoretical calculations.
Bookmarks Related papers MentionsView impact
Electromagnetics, 2014
This article introduces analytical formulas to obtain frequency response for a periodic array of ... more This article introduces analytical formulas to obtain frequency response for a periodic array of hexagon metallic patches and strip cells. The validity of analytic expressions obtained from analysis is verified using full-wave simulations. The formulas are then employed for designing a first-order bandpass frequency selective surface. The proposed frequency selective surface is composed of a periodic array of metallic patches separated by thin air gaps backed by a wire mesh having the same periodicity. The array of metallic patches and the wire mesh constitute a capacitive surface and a coupled inductive surface, respectively, which together act as a resonant structure in the path of an incident plane wave. The frequency response of the proposed frequency selective surface is obtained for various angles of incidence. Moreover, principles of operation, detailed synthesis procedure, and designing guideline for this type of frequency selective surface are presented and discussed in this article.
Bookmarks Related papers MentionsView impact
AEU - International Journal of Electronics and Communications, 2019
This paper presents Metawaveguide in designing slot antenna array based on Metasurface. The tange... more This paper presents Metawaveguide in designing slot antenna array based on Metasurface. The tangential components of the electric field do not have the obligation of being vanished on waveguide boundary. The proposed method studies Geometrical parameters relations' of two specific Metasurface and inner Electrical fields of Metawaveguide in designing slot antenna array. This approach eliminates the need for the offset of slot array which can be benefited from linear array theory. This idea realized by successive filed curvature in the direction of wave propagation in the Metawaveguide by the means of periodic elements on Metasurface. Finally, the step by step flowchart of slot array antenna design has been proposed. A slotted Metawaveguide is fabricated at frequency 10 GHz and then tested.
Bookmarks Related papers MentionsView impact
Applied Computational Electromagnetics Society Journal, 2016
An analytical solution is presented for line source excitation of a cylinder with perfect electro... more An analytical solution is presented for line source excitation of a cylinder with perfect electromagnetic conductor (PEMC) core which is coated with multilayer anisotropic materials. Exact solution is presented using analytical relations for scattering from cylindrical structures. For multilayer structures, we have to calculate the inverse of a matrix which is sparse, thus, we use recursive relations to calculate the fields. A recursive relation for solving the problem with PEMC boundary condition is presented. Finally, some examples are given using this method and the results are compared and validated with the simulation results and other works. The advantage of analytical relation proposed in this paper is much less run time compared to numerical simulation.
Bookmarks Related papers MentionsView impact
Microwave Opt. Technol. Lett., 2016
In this article, a new approach (not new technique) was introduced for designing frequency select... more In this article, a new approach (not new technique) was introduced for designing frequency selective surfaces (FSSs). They tried to compose the desired frequency response using the frequency response of each constituent FSS. Also, a new dual-band miniaturized frequency selective surface was proposed.
Bookmarks Related papers MentionsView impact
Iranian Journal of Electrical and Electronic Engineering, 2019
An intelligent design method of double screen frequency selective surfaces (FSSs) is addressed in... more An intelligent design method of double screen frequency selective surfaces (FSSs) is addressed in this paper. The employed unit cell is composed of two metallic screens, which are printed on both sides of a substrate. The presented non-trial-and-error approach is investigated based on the separate design of each screen. With the help of some physical intuition and an equivalent circuit model, it is shown that the conventional use of complement geometries restricts the final desired filtering response. Therefore, unlike the previous studies, the metallic screens are not geometrically complementary in this paper. An excellent agreement between the full-wave simulations and corresponding equivalent circuit models has been observed. Using standard lumped elements, a highly selective miniaturized FSS (0.06λ0 ~ 0.08λ0) with two closely-spaced pass bands is designed, for GSM and WLAN frequencies. Simulation results show a dual-polarized characteristic with a good angular stability performance for the proposed structure.
Bookmarks Related papers MentionsView impact
Journal of Microwaves, Optoelectronics and Electromagnetic Applications, 2019
In this paper, a new multiband fractal frequency selective surface (MF-FSS) is proposed. The work... more In this paper, a new multiband fractal frequency selective surface (MF-FSS) is proposed. The work presents a new fractal design methodology for FSSs with Swastika fractal patch elements. The proposed MF-FSS includes periodic arrays of metallic patches, printed on a single layer substrate. The structure parametric analysis is carried out in terms of fractal iterations, geometry elements, and unit-cell size. The simple controllable feature of the proposed structure lets us tune the given parameters of FSS geometry to achieve adjustable bandstop filter. The fractal geometry allows us to design compact structures (CP = 54%) that behave like dual-polarized bandstop filters. The designed structure is validated by means of an excellent agreement between the simulation and measurement results. Also, results show the proposed structure presents the most desirable features like fractal compactness, multiband response, dual polarization, excellent angular stability, and controllability. This work presents a fundamental structure that can be applied into the more complex and sophisticated designs in future.
Bookmarks Related papers MentionsView impact
International Journal of Electronics and Communications (AEÜ), 2018
This paper presents a comprehensive and accurate algorithm based on circuit model to design refle... more This paper presents a comprehensive and accurate algorithm based on circuit model to design reflect-array antennas (RAAs). The proposed algorithm can extract geometry of RAA structure corresponding to radiation parameters without employing any approximation or optimization intervention into the algorithm. Simulation results for some comprehensive examples, verify the validity of the proposed algorithm. This method is simple, fast, accurate, and can be expanded to all species of RAAs with arbitrary geometries. One of the main problems confronted in RAAs is low bandwidth characteristics. To attain wide bandwidth, we exploited the proposed algorithm with combination of multi-layer design of RAAs and subwavelength element. Convergence is observed between simulation and fabrication results, asserting good accuracy in method. In 10–15 GHz band, the maximum gain and-1dB bandwidth of two-layer antenna is 31.4 dB and 18.5%, respectively.
Bookmarks Related papers MentionsView impact
International Journal of Electronics and Communications (AEÜ), 2018
In this paper, a fast, robust and accurate computer-aided procedure for design and analysis of hi... more In this paper, a fast, robust and accurate computer-aided procedure for design and analysis of highly efficient metasurface-assisted Fabry-Perot cavity antennas (FPCAs) is proposed. The automatic design algorithm is based on the equivalent circuit model (ECM) and it is capable of predicting the performances of FPCAs whose lateral walls are covered with a perfect electric conductor (PEC). In addition, it wipes out the computational burden arising from trial-and-error steps appearing in the conventional design techniques. As a prototype, according to the proposed design algorithm, a high gain FPCA with extremely high aperture efficiency is designed and fabricated for wireless applications. The equivalent circuit of the employed metasurface-based PRS is modified to enhance the accuracy of extracting the phase and magnitude of its reflection coefficient. To obtain the structural parameters of PRS, a hybrid optimization is applied to the proposed ECM. Simulated results show a maximum directivity of 18.6 dBi at 5.8 GHz leading to a high aperture efficiency of 126%. Experimental measurements on the fabricated prototype are also presented and the results confirm the theoretical and numerical predictions. The proposed design method is general and can be extended for other similar FPCA types exhibiting dual-, multi-and wide-band performances.
Bookmarks Related papers MentionsView impact
Journal of Microwaves, Optoelectronics and Electromagnetic Applications, 2016
A full-wave analytical method using the addition theorems and Hertzian potential functions are us... more A full-wave analytical method using the addition theorems and Hertzian potential functions are used to compute the radar cross section of a sphere coated by several layers composed of common materials and metamaterials. The minimization and maximization of radar cross section of a perfectly electric conductor sphere with such coatings are realized in a frequency band-width and in a wide interval of angles. One of the novelities of this contribution is, taking into dispersion relations of physically realizable metamaterials. So that the optimization procedure for RCS reduction is applied due to the coefficients describing dispersion characteristics. The method of least square is used for the design of a class of radar absorbing materials. The minimization of the error functions are performed by the combination of genetic algorithm and conjugate gradient method. It is shown that the proposed method of computation of radar cross section and its extremization effectively leads to the design of dispersive and isotropic metamaterials for the realization of radar absorbing materials.
Bookmarks Related papers MentionsView impact
Journal of Microwaves, Optoelectronics and Electromagnetic Applications, 2018
Researchers have always been in face of path loss calculation in different media for applications... more Researchers have always been in face of path loss calculation in different media for applications such as telecommunication link design. Wave propagation calculations in large spaces using the FDTD method is time-consuming and imposes a great computational burden. For this reason, to replace the classical FDTD method for wave propagation simulation and path loss calculation in large spaces, optimized methods, namely TDWP, have been provided. In this paper, the use of the TDWP method for wave propagation simulation and path loss calculation above a terrain is investigated. Longitudinal components of ground-waves are taken into account (including direct waves, ground reflections, and surface waves). Propagation space is longitudinally divided into smaller FDTD windows with finite length. The electromagnetic pulse travels through these windows from left to right to the desired point. But despite its capability in reducing computational burden and increasing processing speed, TDWP has lower precision in instantaneous field simulation and calculation of propagation coefficients, so that results obtained from FDTD and TDWP are clearly different. In this paper, some efficient methods are proposed, which yield an increase in method accuracy.
Bookmarks Related papers MentionsView impact
Journal of Communications Technology and Electronics, 2014
In this paper, using the method of moments to calculate the current density and monostatic and b... more In this paper, using the method of moments to calculate the current density and monostatic and
bi-static radar cross section of an unlimited strip by a non-homogeneous impedance. Here, incident wave is a plane wave. To authenticate the method, using the iterative method to solve the integral equations is engaged. Simulation results show that the surface with non- homogeneous impedance has reduced or increase in potential for bi- and mono-static radar cross section in certain azimuth.
Bookmarks Related papers MentionsView impact
Journal of Microwaves, Optoelectronics and Electromagnetic Applications , 2015
In this article, a high-order frequency selective band-stop EMC (electromagnetic compatibility) s... more In this article, a high-order frequency selective band-stop EMC (electromagnetic compatibility) shield is designed using multilayer square loop while each loop resonates at the specific desired frequency. The glass material is picked out as the preferred substrate for the designing process. In contrast to the computationally intensive numerical approaches (software), the equivalent circuit model offers a simple alternative method in FSS (frequency selective surface) analyses which is useful for quickly predicting the performance of FSS. The proposed FSS can be synthesized based on microwave filter theory and the synthesized FSS can control transmission-zero frequencies. A three zero-transmission transparent window is designed using the proposed method, in which 30dB insertion loss is achieved for 6 to 10 GHz bandwidth and optical opacity of the structure is 85%. The response of the analytical model is compared with the results of full-wave simulation. As a result, it predicts quite well the resonant frequencies of the designed FSS.
Bookmarks Related papers MentionsView impact