In this study, we introduce various chiro-optical structures comprising single, dimer, or trimer ... more In this study, we introduce various chiro-optical structures comprising single, dimer, or trimer arrangements of plasmonic nanoantennas capable of actively modulating the chiral transmission of light through the application of an external magnetic field. Specifically, we explore monomers, dimers, and trimers of trapezoidal nanoantennas, as well as trimer configurations of triangular nanoantennas, with Au nanoparticles serving as the plasmonic elements. To enable active magnetic control over the chiro-optical response in these chiral plasmonic systems, Ni is incorporated as the active magneto-plasmonic element. Our findings not only confirm the chirality of all proposed structures but also demonstrate the feasibility of magnetically manipulating the chiro-optical response within these configurations. This study provides valuable insights into the field of chiral magneto-plasmonic nanophotonic systems.
This paper proposes a new framework based on the characteristic modes analysis (CMA) to design po... more This paper proposes a new framework based on the characteristic modes analysis (CMA) to design polarization conversion metasurfaces (PCMs). This approach relies on the information inferred from the characteristic currents of the dominant modes (DMs). To demonstrate the advantages of this strategy, a multi-functional PCM is designed for the Xband frequencies. Besides, this paper expands and develops the characteristic mode rotation (CMR) method to reveal the intrinsic behavior of PCMs in a new manner. In addition, the extended CMR method is utilized for the first time to investigate the physical concepts behind polarization purity and angular stability at the resonance frequencies. Finally, a prototype of the designed polarizer is fabricated and its reflection coefficients are measured. A great agreement between simulation and measurement results is obtained.
Abstract In this paper, the optical properties of several Plasmonic structures including single n... more Abstract In this paper, the optical properties of several Plasmonic structures including single nanodisk, Hexamer and Heptamer, using the Characteristic Mode Theory (CMT) are investigated. Single nanodisk and Hexamer have shown a bright mode with Lorentzian response. In Heptamer, a strong interaction is created between the nanoparticles and thus the Fano resonance occurs with a bright and a dark mode. Based on the CMT analysis and the definition of the Fano response, it has been observed that the collision of the modes in the modal significance diagrams is where the Fano response occurs. Due to the characteristic current distributions, bright and dark modes have been observed that are necessary to create a Fano response. So, using CMT, it can be determined whether the structure is capable of generating a Fano response or not. Also, the frequency of bright and dark modes and the Fano minimum can be obtained using CMT. Moreover, according to the characteristic currents, the structure can be modified to achieve a sharper Fano response. We have selected such structures to investigate this method in these types of Heptamers and it has been shown that the proposed method is applicable for such structures.
2017 Iranian Conference on Electrical Engineering (ICEE), 2017
In this paper, modeling of the rectangular substrate integrated waveguide (SIW)cavity backed narr... more In this paper, modeling of the rectangular substrate integrated waveguide (SIW)cavity backed narrow slot antenna for input impedance is developed by using the transmission-line model and lumped-element circuit. The model of a transverse slot in broad wall of the waveguide is used in the transmission-line model. The results based on transmission-line and circuit modeling are presented and compared with those obtained by full wave simulation. The proposed model gives, for the first time, some fundamental characteristics of the rectangular SIW cavity backed narrow slot antenna.
In this paper, for the first time, effects of external electromagnetic fields on a coplanar waveg... more In this paper, for the first time, effects of external electromagnetic fields on a coplanar waveguide (CPW) are numerically studied by means of the method of finite elements. Two CPW lines with different geometry and dielectric substrate permittivity are considered. Both lines have characteristic impedance of 50 Ω. Induced electric and magnetic fields on the two CPW lines are analyzed by illuminating the structure with a plane wave. The uniform plane wave with fixed frequency at 3 GHz is considered as the incident field. The influences of the incidence angle and dielectric substrate permittivity are investigated. For this purpose, two incidence planes are considered and, for each case, two polarizations, parallel and perpendicular, for incidence electric field relative to incidence planes are studied. According to the results, for the two CPW lines terminated with their characteristic impedance at both ends and the incident plane wave with electric-field intensity of 1 V/m at f = 3 ...
AEU - International Journal of Electronics and Communications, 2021
Abstract In this paper, a method is presented for antenna beamforming based on characteristic mod... more Abstract In this paper, a method is presented for antenna beamforming based on characteristic mode theory. A multi-mode antenna with two elements and four significant orthogonal modes is presented in 5 GHz. Feed positions of the proposed antenna to excite its four characteristic modes are determined; Then with the help of characteristic mode analysis and the reciprocity theorem, amplitude and phase of the excitation coefficients of the proposed antenna are found to change the antenna beam direction in whole azimuth plane. Moreover, changing the weights of the antenna feeds enables elevation beamforming of the proposed antenna.
AEU - International Journal of Electronics and Communications, 2018
A complete equivalent-circuit model of input impedance is developed for a hybrid antenna, which c... more A complete equivalent-circuit model of input impedance is developed for a hybrid antenna, which consists of a Half Mode Substrate Integrated Waveguide (HMSIW) resonator and a microstrip patch. An accurate circuit model is derived using Transmission Line (TL) model and lumped-element. The results based on the circuit modeling are presented and compared with those obtained using full-wave simulation. The proposed model, for the first time, clarifies fundamental characteristics of the input impedance of the hybrid antenna, which are verified by the results of a full-wave simulation and those obtained by measurement.
Abstract This article presents two new cavity-backed slot antennas utilizing substrate-integrated... more Abstract This article presents two new cavity-backed slot antennas utilizing substrate-integrated waveguide technology and offering high gain. Radiation performances of the proposed antennas are experimentally and numerically evaluated. Using two slots backed by a circular cavity, one can improve antenna gain by 2 dB over the gain of a single-slot antenna. Then a 2 × 2-slot antenna array backed by two cavities is presented, which offers a gain of 9.2 dBi, which is 4.2 dB and 2.2 dB higher than the gain of single- and two-slot antennas, respectively. All the proposed antenna structures are made on a single-layer substrate, and a low-cost printed circuit board process is used for fabrication.
AEU - International Journal of Electronics and Communications, 2019
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
AEU - International Journal of Electronics and Communications, 2020
Background: Right hepatectomy (RH) is the most common type of major hepatectomy and can be achiev... more Background: Right hepatectomy (RH) is the most common type of major hepatectomy and can be achieved without portal triad clamping (PTC) in non-cirrhotic liver. The present study reviews our standardized policy of performing RH without systematic PTC. Methods: One hundred and eighty-one consecutive RH were performed in non-cirrhotic patients, with division of the right afferent and efferent blood vessels prior to transection, without systematically using PTC. Prospectively collected data were analysed, focusing on the following endpoints: need for salvage PTC, ischaemic time, blood loss and post-operative outcome. Results: Extra-hepatic division of the right hepatic vessels was feasible in all patients, but was ineffective in 48 patients (26.5%) who required salvage PTC during transection. In those patients, the median ischaemic time was 20 min. The median blood loss was 500 ml (50-3000). Six patients (3.3%) experienced post-operative liver failure. Overall morbidity, severe morbidity and mortality were 42%, 12.1% and 1.6%, respectively, with peri-operative transfusion rate (16.6%) being the only factor associated with morbidity. Discussion: By performing RH with extra-hepatic vascular division prior to transection, PTC can be safely avoided in the majority of patients.
IEEE Transactions on Antennas and Propagation, 2016
It has come to our attention that Eq. (1) in [1] contains two small typos. In the denominator, a ... more It has come to our attention that Eq. (1) in [1] contains two small typos. In the denominator, a factor "2" has been omitted. In the numerator, "2.404" should read 2.405." The correct form is presented here.
2014 22nd Iranian Conference on Electrical Engineering (ICEE), 2014
In this paper, novel cavity-backed slot antennas based on substrate-integrated waveguide (SIW) fo... more In this paper, novel cavity-backed slot antennas based on substrate-integrated waveguide (SIW) for dual frequency and bandwidth enhancement are proposed. Their performance is numerically evaluated by means of the method of finite elements. Using metalized via holes at the middle of a SIW cavity, resonate frequency of TM010 mode is shifted up. With placing a slot at one side of the cavity, electromagnetic fields are radiated thorough the slot at two resonate frequencies of TM010 and TM110 modes. Proposed antenna operate at 9.68 GHz and 10.28 GHz with impedance bandwidths of 60 MHz and 80 MHz for S11<;-10 dB respectively and it provides gain of at least 4.6 dB. Moreover, by merging two modes, bandwidth of the structure would be improved. All antenna structures are made of a single-layer substrate and are fed by a 50 Ω microstrip line. The proposed antennas are compact, low-cost and present high radiation efficiency.
A novel design of feeding Microstrip Patch Antennas (MPAs) using Half Mode Substrate Integrated W... more A novel design of feeding Microstrip Patch Antennas (MPAs) using Half Mode Substrate Integrated Waveguide (HMSIW) technique is proposed. The design is based on the half-mode circular SIW cavity operating at TM010 mode. The proposed antenna structure is made of a single-layer substrate and fed by a 50 Ω microstrip line. This antenna has attractive features including wide bandwidth, low profile, and high radiation efficiency. Also, it is easy to integrate the MPA with planar circuits. The whole structure is numerically evaluated using HFSS software package. Results show a simulated impedance bandwidth (S11(dB) ≤ -10 dB) of 9.6%, gain up to 7.5 dB and radiation efficiency is around 95%.
- Two Dielectric Resonator Antenna (DRA) structures, Dielectric Image Line-slot and Microstrip-sl... more - Two Dielectric Resonator Antenna (DRA) structures, Dielectric Image Line-slot and Microstrip-slot fed, are numerically investigated using two commercial software, HFSS and CST. Radiation characteristics of both antennas including return loss, radiation patterns ...
A set of hybrid microstrip patch and semi-circular cavity antennas is introduced. The semi-circul... more A set of hybrid microstrip patch and semi-circular cavity antennas is introduced. The semi-circular cavity is implemented using Half-mode Substrate Integrated Waveguide (HMSIW) technique. Different shapes of the patch including rectangular, semi-circular and equilateral triangular are excited using proximity effect by the semi-circular SIW cavity at its TM010 mode. The proposed antenna structures have been excited using an inset 50 W microstrip line that leads to a facility of planar circuit integration. The inherent limited bandwidth of the conventional microstrip patch antenna and SIW cavity-backed slot antenna is improved about 6% to 10% depending on the type of the patch using the proposed structure. Additionally, the proposed hybrid antenna enhanced the antenna gain by about 1.5 dB in comparison with the half-mode cavity without patch. Meanwhile, the proposed hybrid antennas made on a single-layer substrate has a low fabrication cost using printed circuit board (PCB) process. Three hybrid antennas are numerically and experimentally investigated. A comparative study between the three different structures contains gain, bandwidth, Cross Polarization Level (CPL) and Front to Back Ratio (FBR) is presented.
In this study, we introduce various chiro-optical structures comprising single, dimer, or trimer ... more In this study, we introduce various chiro-optical structures comprising single, dimer, or trimer arrangements of plasmonic nanoantennas capable of actively modulating the chiral transmission of light through the application of an external magnetic field. Specifically, we explore monomers, dimers, and trimers of trapezoidal nanoantennas, as well as trimer configurations of triangular nanoantennas, with Au nanoparticles serving as the plasmonic elements. To enable active magnetic control over the chiro-optical response in these chiral plasmonic systems, Ni is incorporated as the active magneto-plasmonic element. Our findings not only confirm the chirality of all proposed structures but also demonstrate the feasibility of magnetically manipulating the chiro-optical response within these configurations. This study provides valuable insights into the field of chiral magneto-plasmonic nanophotonic systems.
This paper proposes a new framework based on the characteristic modes analysis (CMA) to design po... more This paper proposes a new framework based on the characteristic modes analysis (CMA) to design polarization conversion metasurfaces (PCMs). This approach relies on the information inferred from the characteristic currents of the dominant modes (DMs). To demonstrate the advantages of this strategy, a multi-functional PCM is designed for the Xband frequencies. Besides, this paper expands and develops the characteristic mode rotation (CMR) method to reveal the intrinsic behavior of PCMs in a new manner. In addition, the extended CMR method is utilized for the first time to investigate the physical concepts behind polarization purity and angular stability at the resonance frequencies. Finally, a prototype of the designed polarizer is fabricated and its reflection coefficients are measured. A great agreement between simulation and measurement results is obtained.
Abstract In this paper, the optical properties of several Plasmonic structures including single n... more Abstract In this paper, the optical properties of several Plasmonic structures including single nanodisk, Hexamer and Heptamer, using the Characteristic Mode Theory (CMT) are investigated. Single nanodisk and Hexamer have shown a bright mode with Lorentzian response. In Heptamer, a strong interaction is created between the nanoparticles and thus the Fano resonance occurs with a bright and a dark mode. Based on the CMT analysis and the definition of the Fano response, it has been observed that the collision of the modes in the modal significance diagrams is where the Fano response occurs. Due to the characteristic current distributions, bright and dark modes have been observed that are necessary to create a Fano response. So, using CMT, it can be determined whether the structure is capable of generating a Fano response or not. Also, the frequency of bright and dark modes and the Fano minimum can be obtained using CMT. Moreover, according to the characteristic currents, the structure can be modified to achieve a sharper Fano response. We have selected such structures to investigate this method in these types of Heptamers and it has been shown that the proposed method is applicable for such structures.
2017 Iranian Conference on Electrical Engineering (ICEE), 2017
In this paper, modeling of the rectangular substrate integrated waveguide (SIW)cavity backed narr... more In this paper, modeling of the rectangular substrate integrated waveguide (SIW)cavity backed narrow slot antenna for input impedance is developed by using the transmission-line model and lumped-element circuit. The model of a transverse slot in broad wall of the waveguide is used in the transmission-line model. The results based on transmission-line and circuit modeling are presented and compared with those obtained by full wave simulation. The proposed model gives, for the first time, some fundamental characteristics of the rectangular SIW cavity backed narrow slot antenna.
In this paper, for the first time, effects of external electromagnetic fields on a coplanar waveg... more In this paper, for the first time, effects of external electromagnetic fields on a coplanar waveguide (CPW) are numerically studied by means of the method of finite elements. Two CPW lines with different geometry and dielectric substrate permittivity are considered. Both lines have characteristic impedance of 50 Ω. Induced electric and magnetic fields on the two CPW lines are analyzed by illuminating the structure with a plane wave. The uniform plane wave with fixed frequency at 3 GHz is considered as the incident field. The influences of the incidence angle and dielectric substrate permittivity are investigated. For this purpose, two incidence planes are considered and, for each case, two polarizations, parallel and perpendicular, for incidence electric field relative to incidence planes are studied. According to the results, for the two CPW lines terminated with their characteristic impedance at both ends and the incident plane wave with electric-field intensity of 1 V/m at f = 3 ...
AEU - International Journal of Electronics and Communications, 2021
Abstract In this paper, a method is presented for antenna beamforming based on characteristic mod... more Abstract In this paper, a method is presented for antenna beamforming based on characteristic mode theory. A multi-mode antenna with two elements and four significant orthogonal modes is presented in 5 GHz. Feed positions of the proposed antenna to excite its four characteristic modes are determined; Then with the help of characteristic mode analysis and the reciprocity theorem, amplitude and phase of the excitation coefficients of the proposed antenna are found to change the antenna beam direction in whole azimuth plane. Moreover, changing the weights of the antenna feeds enables elevation beamforming of the proposed antenna.
AEU - International Journal of Electronics and Communications, 2018
A complete equivalent-circuit model of input impedance is developed for a hybrid antenna, which c... more A complete equivalent-circuit model of input impedance is developed for a hybrid antenna, which consists of a Half Mode Substrate Integrated Waveguide (HMSIW) resonator and a microstrip patch. An accurate circuit model is derived using Transmission Line (TL) model and lumped-element. The results based on the circuit modeling are presented and compared with those obtained using full-wave simulation. The proposed model, for the first time, clarifies fundamental characteristics of the input impedance of the hybrid antenna, which are verified by the results of a full-wave simulation and those obtained by measurement.
Abstract This article presents two new cavity-backed slot antennas utilizing substrate-integrated... more Abstract This article presents two new cavity-backed slot antennas utilizing substrate-integrated waveguide technology and offering high gain. Radiation performances of the proposed antennas are experimentally and numerically evaluated. Using two slots backed by a circular cavity, one can improve antenna gain by 2 dB over the gain of a single-slot antenna. Then a 2 × 2-slot antenna array backed by two cavities is presented, which offers a gain of 9.2 dBi, which is 4.2 dB and 2.2 dB higher than the gain of single- and two-slot antennas, respectively. All the proposed antenna structures are made on a single-layer substrate, and a low-cost printed circuit board process is used for fabrication.
AEU - International Journal of Electronics and Communications, 2019
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
AEU - International Journal of Electronics and Communications, 2020
Background: Right hepatectomy (RH) is the most common type of major hepatectomy and can be achiev... more Background: Right hepatectomy (RH) is the most common type of major hepatectomy and can be achieved without portal triad clamping (PTC) in non-cirrhotic liver. The present study reviews our standardized policy of performing RH without systematic PTC. Methods: One hundred and eighty-one consecutive RH were performed in non-cirrhotic patients, with division of the right afferent and efferent blood vessels prior to transection, without systematically using PTC. Prospectively collected data were analysed, focusing on the following endpoints: need for salvage PTC, ischaemic time, blood loss and post-operative outcome. Results: Extra-hepatic division of the right hepatic vessels was feasible in all patients, but was ineffective in 48 patients (26.5%) who required salvage PTC during transection. In those patients, the median ischaemic time was 20 min. The median blood loss was 500 ml (50-3000). Six patients (3.3%) experienced post-operative liver failure. Overall morbidity, severe morbidity and mortality were 42%, 12.1% and 1.6%, respectively, with peri-operative transfusion rate (16.6%) being the only factor associated with morbidity. Discussion: By performing RH with extra-hepatic vascular division prior to transection, PTC can be safely avoided in the majority of patients.
IEEE Transactions on Antennas and Propagation, 2016
It has come to our attention that Eq. (1) in [1] contains two small typos. In the denominator, a ... more It has come to our attention that Eq. (1) in [1] contains two small typos. In the denominator, a factor "2" has been omitted. In the numerator, "2.404" should read 2.405." The correct form is presented here.
2014 22nd Iranian Conference on Electrical Engineering (ICEE), 2014
In this paper, novel cavity-backed slot antennas based on substrate-integrated waveguide (SIW) fo... more In this paper, novel cavity-backed slot antennas based on substrate-integrated waveguide (SIW) for dual frequency and bandwidth enhancement are proposed. Their performance is numerically evaluated by means of the method of finite elements. Using metalized via holes at the middle of a SIW cavity, resonate frequency of TM010 mode is shifted up. With placing a slot at one side of the cavity, electromagnetic fields are radiated thorough the slot at two resonate frequencies of TM010 and TM110 modes. Proposed antenna operate at 9.68 GHz and 10.28 GHz with impedance bandwidths of 60 MHz and 80 MHz for S11<;-10 dB respectively and it provides gain of at least 4.6 dB. Moreover, by merging two modes, bandwidth of the structure would be improved. All antenna structures are made of a single-layer substrate and are fed by a 50 Ω microstrip line. The proposed antennas are compact, low-cost and present high radiation efficiency.
A novel design of feeding Microstrip Patch Antennas (MPAs) using Half Mode Substrate Integrated W... more A novel design of feeding Microstrip Patch Antennas (MPAs) using Half Mode Substrate Integrated Waveguide (HMSIW) technique is proposed. The design is based on the half-mode circular SIW cavity operating at TM010 mode. The proposed antenna structure is made of a single-layer substrate and fed by a 50 Ω microstrip line. This antenna has attractive features including wide bandwidth, low profile, and high radiation efficiency. Also, it is easy to integrate the MPA with planar circuits. The whole structure is numerically evaluated using HFSS software package. Results show a simulated impedance bandwidth (S11(dB) ≤ -10 dB) of 9.6%, gain up to 7.5 dB and radiation efficiency is around 95%.
- Two Dielectric Resonator Antenna (DRA) structures, Dielectric Image Line-slot and Microstrip-sl... more - Two Dielectric Resonator Antenna (DRA) structures, Dielectric Image Line-slot and Microstrip-slot fed, are numerically investigated using two commercial software, HFSS and CST. Radiation characteristics of both antennas including return loss, radiation patterns ...
A set of hybrid microstrip patch and semi-circular cavity antennas is introduced. The semi-circul... more A set of hybrid microstrip patch and semi-circular cavity antennas is introduced. The semi-circular cavity is implemented using Half-mode Substrate Integrated Waveguide (HMSIW) technique. Different shapes of the patch including rectangular, semi-circular and equilateral triangular are excited using proximity effect by the semi-circular SIW cavity at its TM010 mode. The proposed antenna structures have been excited using an inset 50 W microstrip line that leads to a facility of planar circuit integration. The inherent limited bandwidth of the conventional microstrip patch antenna and SIW cavity-backed slot antenna is improved about 6% to 10% depending on the type of the patch using the proposed structure. Additionally, the proposed hybrid antenna enhanced the antenna gain by about 1.5 dB in comparison with the half-mode cavity without patch. Meanwhile, the proposed hybrid antennas made on a single-layer substrate has a low fabrication cost using printed circuit board (PCB) process. Three hybrid antennas are numerically and experimentally investigated. A comparative study between the three different structures contains gain, bandwidth, Cross Polarization Level (CPL) and Front to Back Ratio (FBR) is presented.
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Papers by Hamideh Dashti