communications
Jaafar Bazrafshan; Fatemeh Sadeghikia; Ali Karami Horestani; Mohamed Himdi
Articles in Press, Accepted Manuscript, Available Online from 25 September 2023
Abstract
This paper presents a novel approach for designing a reconfigurable and steerable antenna utilizing plasma dielectric slabs along the aperture of a pyramidal horn antenna. The antenna offers electronic control over both the radiation gain and the direction of the main beam. The proposed configuration ...
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This paper presents a novel approach for designing a reconfigurable and steerable antenna utilizing plasma dielectric slabs along the aperture of a pyramidal horn antenna. The antenna offers electronic control over both the radiation gain and the direction of the main beam. The proposed configuration consists of four plasma slabs aligned perpendicular to the horn aperture along the horn axis, complemented by four diagonally connected plasma slabs. Each plasma slab can be independently switched ON or OFF, enabling dynamic adjustment of the radiation gain and steering of the main beam. Numerical investigations demonstrate that toggling the plasma slabs or controlling the plasma frequency of these slabs allows for fine-grained control over the radiation gain and beam steering of the pyramidal horn antenna. The selection of appropriate dimensions and angles for the plasma slabs plays a crucial role in achieving the desired beam steering angle and radiation gain control. To validate the concept, the proposed antenna configuration is designed and numerically simulated at a frequency of 10 GHz. The results indicate that the radiation gain of the antenna can be significantly enhanced, reaching up to 6.5 dBi. Additionally, the main beam direction can be steered within a range of ±12 degrees.
Space subsystems design: (navigation, control, structure and…)
Fatemeh Asdaghpour; Fatemeh Sadeghikia; Mohammad Ali Farsi
Volume 15, Issue 2 , June 2022, , Pages 103-113
Abstract
Antennas, which are usually installed on the outer shell of these systems, are therefore always exposed to the thermal fluctuations of the space environment. Thermal fluctuations cause the antenna surfaces to expand, contract and distort and can cause the antenna to malfunction. In this paper, the effects ...
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Antennas, which are usually installed on the outer shell of these systems, are therefore always exposed to the thermal fluctuations of the space environment. Thermal fluctuations cause the antenna surfaces to expand, contract and distort and can cause the antenna to malfunction. In this paper, the effects of thermal expansion and contraction due to an LEO orbital mission on the radial characteristics of two X-band reflective antennas, one broadband antenna and the other narrowband, And the resulting radiation characteristics are compared with the characteristics of equivalent sample antennas at ambient temperature. Analyses show that narrowband antennas are very vulnerable to thermal fluctuations and, therefore, it is necessary to choose the material of the antennas from materials whose thermal expansion coefficient is very small. In addition, choosing the appropriate protection method to maintain the optimal performance of the antenna is one of the most essential activities in the construction of space antennas.
Fatemeh Sadeghikia; Ali Karami Horestani
Volume 11, Issue 2 , September 2018, , Pages 55-59
Abstract
The aim of this study is to examine the effects of diameter of ground conductor in an axial mode helical antenna on some of the characteristics of the antenna. It is shown that a proper ratio of diameter of ground plane to diameter of helix can be chosen to make a trade-off between the performance of ...
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The aim of this study is to examine the effects of diameter of ground conductor in an axial mode helical antenna on some of the characteristics of the antenna. It is shown that a proper ratio of diameter of ground plane to diameter of helix can be chosen to make a trade-off between the performance of helical antenna and its mass budget. It is shown through computational analysis that this optimum ratio is about 1.5. The results show that an increase in this ratio increases the mass budget, but it does not improve the antenna performance significantly. The simulation results also indicatethat this ratio is independent of the number of helix turns. After measurement, it was found that the simulation results of the antenna well agreed with its measured results acquired at the anechoic chamber.
fatemeh Sadeghi-kia
Volume 10, Issue 1 , June 2017, , Pages 27-34
Abstract
This study focuses on the characteristics of plasma antennas for their application in space communication systems. Structural and functional characteristics of plasma antenna are presented to evaluate their capability of being used in space missions. Numerical and experimental analysis results of the ...
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This study focuses on the characteristics of plasma antennas for their application in space communication systems. Structural and functional characteristics of plasma antenna are presented to evaluate their capability of being used in space missions. Numerical and experimental analysis results of the plasma antenna show that the resonant frequency of the antenna is controllable by changing the applied power, thus allowing different transmitting frequencies with a single element. This property leads to the reduction of the antenna elements in a limited area and the simplification in the layout of onboard communication systems as well as a decrease in the interferences of the electromagnetic waves. Analysis of the circular array of plasma antenna shows a novel beam forming mechanism with a high directivity in the space.
Fateme Sadeghikia; Farokh HojatKashani; Jalil RashedMohasal; S. Javad Giyome- Bozorgi
Volume 5, Issue 3 , October 2012, , Pages 59-66
Abstract
Numerical investigation has been made on a linear array of surface wave driven plasma monopole antenna using finite difference time domain simulation. Variations of the excitation power can be used for construction of a dynamically reconfigurable antenna. Plasma elements in the nominal pressure of 0.4 ...
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Numerical investigation has been made on a linear array of surface wave driven plasma monopole antenna using finite difference time domain simulation. Variations of the excitation power can be used for construction of a dynamically reconfigurable antenna. Plasma elements in the nominal pressure of 0.4 mb are fed through an RF power at 500 MHz using an equal power divider. The results show that while the variations of the excitation power shift the array resonant frequency between 50 MHz to 120 MHz, the array gain and directivity remain approximately unchanged in the new resonant frequency. Since efficiency is critical to communication systems, the total efficiencies of the reconfigurable array were analyzed from the least to the highest excitation power. The highest efficiency belongs to the array which the separation between elements is a quarter of wavelength. Using this cutting edge technology in space application, it will be possible to transmit through an antenna in a multiple frequency avoiding interference between adjacent antennas.
F. Sadeghikia; S. Amin; K. Raisi; M. Bahrami
Volume 1, Issue 2 , December 2008, , Pages 57-60
Abstract
This paper provides an instruction for designing and building of an Inverted F antenna mounted on a cylindrical conducting body with a conical nose. Designed antennas were simulated using a full wave simulator HFSS based on the finite element method and their radiation patterns and return loss were studied. ...
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This paper provides an instruction for designing and building of an Inverted F antenna mounted on a cylindrical conducting body with a conical nose. Designed antennas were simulated using a full wave simulator HFSS based on the finite element method and their radiation patterns and return loss were studied. The simulated data were compared with measurement results.
