Editor-in-Chief Lecture
Shahriar Shirvani Moghaddam
Original Research Paper
M. Zahiry; S.M. Hashemi; J. Ghalibafan
Abstract
In this paper, a new method for designing an active dual-band dipole antenna is proposed. The operating frequencies of the proposed antenna are 150 and 450 MHz that are usually used in military applications. Using a series stub is the main idea in the proposed dual-band antenna, where it makes an independent ...
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In this paper, a new method for designing an active dual-band dipole antenna is proposed. The operating frequencies of the proposed antenna are 150 and 450 MHz that are usually used in military applications. Using a series stub is the main idea in the proposed dual-band antenna, where it makes an independent resonance frequency higher than the main resonance frequency of a conventional dipole. To make appropriate matching impedance in the two frequency bands, the technique of creating an internal coaxial cable is used. Furthermore, to improve the antenna gain, an amplifier is in series part connected to the proposed dipole antenna. The simulated and measured results of the return loss, radiation patterns and antenna gain show that this antenna has a good operation in both resonance frequencies.
Original Research Paper
R. Kazemi
Abstract
This paper presents an element of a 2×2-element array antenna for Inmarsat BGAN/GPS applications. The element is an axial mode printed quadrifilar helical antenna that has been integrated with a compact feed network to provide sequential phase rotation for circular polarization (CP) radiation. ...
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This paper presents an element of a 2×2-element array antenna for Inmarsat BGAN/GPS applications. The element is an axial mode printed quadrifilar helical antenna that has been integrated with a compact feed network to provide sequential phase rotation for circular polarization (CP) radiation. The novel integrated lumped-element feed network is designed to provide a balanced RF power to the four helix arms with a 90° sequential phase difference between them. The design maintains a low cross polarization, and accordingly, a high quality of RHCP up to ±66° over the transmit frequency band of 1616 MHz to 1626 MHz. The gain in this frequency range is higher than 3.5 dB with a return loss better than 11 dB and a perfect circular polarization performance (axial ratio ~0 dB). The proposed antenna has small size, light weight, low cost, almost hemispherical radiation pattern and excellent circular polarization that can become a good candidate in satellite L1-band and BGAN satellite communications.
Original Research Paper
M. Shakibmehr; M. Lotfizad
Abstract
In this paper, an ultra-low-noise amplifier with frequency band switching capability is designed, simulated and fabricated. The two frequency ranges of this amplifier consist of the 2.4 to 2.5 GHz and 3.1 GHz to 3.15 GHz frequency bands. The designed amplifier has a noise figure of less than 1dB, a minimum ...
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In this paper, an ultra-low-noise amplifier with frequency band switching capability is designed, simulated and fabricated. The two frequency ranges of this amplifier consist of the 2.4 to 2.5 GHz and 3.1 GHz to 3.15 GHz frequency bands. The designed amplifier has a noise figure of less than 1dB, a minimum gain of 23 dB and a VSWR of less than 2 in the whole frequency band. The design process starts with increasing the stability factor in the source through manipulating the inductor placement technique. Then the input and output matching circuits for the first frequency band are designed. This process is completed by utilizing two similar stages placed successively in order to achieve the desired gain level. Since no degradation of the noise figure is observed and acceptable values are also obtained for other parameters, switching the elements in the output matching circuit can be a good idea for avoiding the use of a similar circuit for the second frequency band. The optimum secondary values for the mentioned elements are obtained through the analyses performed using the ADS software. For changing the values of the mentioned elements two MOSFETs are used for adding capacitance and inductance to the matching circuit. In the next step, the designed amplifier is finalized and optimized after adding a suitable bias circuit to it. Moreover, The designed amplifier is fabricated and a good agreement between the measurement, analysis, and simulation results is observed.
Original Research Paper
A. Ahmadipour; H. Tezkhan; H. Soofi
Abstract
Due to the growing demand for higher bandwidth, employing optical devices instead of electronic devices in data transmission systems has attracted much attention in recent years. Optical switches, modulators and wavelength converters are a few examples of the required optical devices. CMOS compatible ...
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Due to the growing demand for higher bandwidth, employing optical devices instead of electronic devices in data transmission systems has attracted much attention in recent years. Optical switches, modulators and wavelength converters are a few examples of the required optical devices. CMOS compatible fabrication of these devices, leads to much more growing of this technology. Optical pulse compression, is required for generating ultra-short pulses for high bandwidth optical transmission systems. In this work, we present a CMOS fabrication process compatible, integrated optical pulse compressor. A Silicon waveguide coated by MoS2 for nonlinearity enhancement is used for self-phase modulation and a chirped Bragg grating utilizing corrugated silicon waveguides is employed to achieve the required anomalous dispersion. Low power and high compression ratio were considered in this work. We achieved a compression ratio of 3.5 by using a relatively low power optical pulse of 8W and a short waveguide length of 1mm.
Original Research Paper
N. Morshedian; M. Aram; A. Mehramiz; N. Jahanian
Abstract
In this report, the distribution and deviation of electric field in the active medium of the TE CO2 laser has been investigated due to the injection of net electron charge beam as a plasma generator. Some parameters of system have been considered, such as density and mean-free-path of injected charge ...
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In this report, the distribution and deviation of electric field in the active medium of the TE CO2 laser has been investigated due to the injection of net electron charge beam as a plasma generator. Some parameters of system have been considered, such as density and mean-free-path of injected charge beam. The electric potential and electric field distribution have been simulated by solving the Poison’s equation using the method of successive over relaxation (SOR) numerical method. The electrode potential and the number of injected charged particles are respectively considered to be +75 kV and 108 mm-3. In these conditions, the maximum energy of the electrons beam would be at the order of 1-2 eV. Deviation of the electric field with different mean-free-path of electrons beam with Gaussian density distribution has been numerically calculated. It has been concluded that if the net charge density is increased then the field deviation would grow. Moreover, if the mean-free-path of the electrons is decreased, subsequently, the electric field deviation is increased.
Original Research Paper
M. Maleki; S.H. Mohseni Armaki; E. Hamidi
Abstract
ince many applications rely on the knowledge of the electromagnetic material properties of ferrites, such as ferrite phase shifters, this paper presents an algorithm for characterizing ferrite materials in a single frequency using a rectangular waveguide system. In this method, the extraction of ferrite ...
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ince many applications rely on the knowledge of the electromagnetic material properties of ferrites, such as ferrite phase shifters, this paper presents an algorithm for characterizing ferrite materials in a single frequency using a rectangular waveguide system. In this method, the extraction of ferrite parameters is implemented through minimizing the difference between the measured data and the results from modal analysis of the system. The main advantage of this method compared tothe other ones is that the proposed method only needs the amplitude of the reflection and transmission coefficients to estimate the parameters of ferrite materials. This makes the implementation easy and eliminates the problems associated with phase calibrations and measurements. This validation is achieved by simulation and experimental tests. The proposed algorithm is validated by characterizing YIG and SL-470 ferrites.
Original Research Paper
M. KHadir; K. Forooraghi; Z. Atlasbaf
Abstract
In this paper, a new method for radar cross section reduction of a monopole antenna is proposed. In this method, a plasma helix like fluorescent bulbs is placed around the antenna element. The selected plasma parameter for this medium acts as an absorber without disturbing the antenna performance. The ...
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In this paper, a new method for radar cross section reduction of a monopole antenna is proposed. In this method, a plasma helix like fluorescent bulbs is placed around the antenna element. The selected plasma parameter for this medium acts as an absorber without disturbing the antenna performance. The simulations show that radar cross section of simulated antenna is reduced in a wide frequency range. In this paper, the plasma parameter is chosen in such a way that reduces RCS at 4GHz. At this frequency, the radar cross section reduction is about 10dBsm. Due to the frequency dependent of the plasma medium, the plasma parameter must be changed for better result in the other frequencies. This change can be performed electrically without any change in the antenna structure. In this simulation, a PEC rode with 3cm diameter and 15cm height is chosen for the monopole antenna element. This monopole antenna resonates at 630 MHz. After placing the plasma helix around the antenna element, there is no significant change in the antenna performance.
Original Research Paper
M. Samadpour Hendevari; M. Bemani; S. Nikmehr
Abstract
In this paper, the possible realization of the electromagnetic (EM) absorber as a thin metasurface is considered. The metasurface is based on establishing a passive surface of electric and magnetic currents using the Huygen’s principle. So, the absorber is named Huygens Absorber (HA). The metasurface ...
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In this paper, the possible realization of the electromagnetic (EM) absorber as a thin metasurface is considered. The metasurface is based on establishing a passive surface of electric and magnetic currents using the Huygen’s principle. So, the absorber is named Huygens Absorber (HA). The metasurface can be designed using split meander lines with spiral rings. In this way, both sides of the substrate must be patterned to obtain electric and magnetic currents. In this paper, it is shown that the currents can be obtained using appropriate cells based on bi-anisotropic media theory. It is shown that to obtain a normal absorber, appropriate omega particles can be used. It is worth noting that the proposed absorber does not need any lossy material to absorb the waves which is a unique and excellent property of this kind of absorber. It is a thin groundless surface which makes it possible to design a double-sided metasurface.
Original Research Paper
F.S. Mohseni Armaki; S.A. Mohseni Armaki
Abstract
In this paper, the design and implementation of plasma antenna array with beam forming is discussed. The structure consists of a circular array of plasma tube enclosed in a unipolar UHF band monopole antenna. Beam forming is possible by stimulated plasma tubes. The combination of the above antenna with ...
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In this paper, the design and implementation of plasma antenna array with beam forming is discussed. The structure consists of a circular array of plasma tube enclosed in a unipolar UHF band monopole antenna. Beam forming is possible by stimulated plasma tubes. The combination of the above antenna with plasma excitation controller makes a beam forming smart antenna. An experimental model in UHF band is fabricated that shows a good agreement between the simulated and measured results.
Original Research Paper
N. Rezazadeh; A. Kianvash
Abstract
In this research work cobalt-ferrite (CoFe2O4) nanoparticles were synthesized by a simple, general sol-gel auto-combustion method. For this study, electromagnetic (EM) wave absorbing coatings with different weight fractions of nano-carbon and CoFe2O4 (which, arises from both dielectric and magnetic contributions) ...
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In this research work cobalt-ferrite (CoFe2O4) nanoparticles were synthesized by a simple, general sol-gel auto-combustion method. For this study, electromagnetic (EM) wave absorbing coatings with different weight fractions of nano-carbon and CoFe2O4 (which, arises from both dielectric and magnetic contributions) and polymeric epoxy resin were prepared and their characteristics were fully investigated. In this research, the physical properties of current products have been improved drastically. Values of reflection loss (RL) below -5dB can be obtained at the frequency range of 8-12 GHz for the composite with 1%wt nano-carbon and 59%wt CoFe2O4. As the weight fraction of nano-carbon in the composites is increased, the minimum reflection loss is reduced with a matching thickness of 1mm. This investigation concludes that hybrid EM absorbents in the form of paints, consisting of nano-sized CoFe2O4 and nano-carbon show excellent broad bandwidths of absorption. The structure, morphology and absorption properties are studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and vector network analyzer (VNA).
Original Research Paper
S. Mohanna; A. Tamandani; S. Soltani
Abstract
Some useful features of microstrip patch antennas are low profile, low weight and easy fabrication. However this type of antenna suffers from having a low gain, caused by propagation surface waves. In this paper, a new near zero refractive index metamaterial (MTM) unit cell is designed and fabricated ...
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Some useful features of microstrip patch antennas are low profile, low weight and easy fabrication. However this type of antenna suffers from having a low gain, caused by propagation surface waves. In this paper, a new near zero refractive index metamaterial (MTM) unit cell is designed and fabricated as a superstrate over a Rectangular Microstrip Patch Antennas (RMPA). In order to obtain a maximum gain, the distance between the superstrate and the microstrip of the antenna has been optimized. Additionally, the feed position has been optimized to minimize the return loss. The operation frequency set at 10.3GHz and there are two resonance frequencies, one at f1=10.1GH and the other at f2=11.68GHz. The simulations and measured results indicated that the superstrate MTM structure, designed to place horizontally over the antenna, increases the gain to almost 2.4dB and 2.62dB at 10.1GHZ and 11.68GHZ respectively. Moreover, the radiation efficiency and directivity of the antenna are improved significantly.
Original Research Paper
A. Amn-e-Elahi; P. Rezaei
Abstract
An axially corrugated horn antenna with an elliptically shaped taper is proposed for satellite communication applications. This structure is a good candidate for the feed of reflectors and also for improving the electrical properties of reflector antennas. A tapering method is used to justify the horizontal ...
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An axially corrugated horn antenna with an elliptically shaped taper is proposed for satellite communication applications. This structure is a good candidate for the feed of reflectors and also for improving the electrical properties of reflector antennas. A tapering method is used to justify the horizontal location of the corrugation profile which improves the electrical performance of the presented antenna. The simulation results of a conventional axial corrugated horn antenna with a linear taper are compared to those of the proposed antenna. These results illustrate that the cross-polarization, side-lobe level and return loss of our antenna are improved by about 16dB, 4dB and 9dB, respectively. The axial corrugated horn antenna with an elliptical tapering function is simple and low-cost as compared to the other corrugated horn antennas such as scalar (vertically) corrugated horn and subsequently, it could be preferred in commercial applications.
Original Research Paper
A. Sotoudeh; A. Rajabi; M. Amirmazlaghani
Volume 5, Issue 1 , January 2017, Pages 71-77
Abstract
In this paper, photodetection properties of a Graphene-based device at the third telecommunication window have been reported. The structure of the device is a Graphene-silicon Schottky junction which has been simulated in the form of an infrared photodetector. Graphene has specific electrical and optical ...
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In this paper, photodetection properties of a Graphene-based device at the third telecommunication window have been reported. The structure of the device is a Graphene-silicon Schottky junction which has been simulated in the form of an infrared photodetector. Graphene has specific electrical and optical properties which makes this material a good candidate for optoelectronic applications. Photodetection characteristic of Graphene-silicon Schottky junction is investigated by measuring the (current-voltage) curve at the third telecommunication window under 1550nm radiations. The DC electrical characteristic of the device is calculated. The simulated rectifier junction has a potential barrier of 0.31eV, the ideality factor of 2.7 and the saturation current of 10-11A. The detector responsivity under 1550nm radiations is measured about 20mA/W which is an order of magnitude larger than other Si-based detectors in this wavelength. The internal quantum efficiency (QEin) is calculated about 60% while the external quantum efficiency (QEex) is measured to be 1.6%. A comprehensive theoretical justification is presented based on Fowler theory which allows comparison between the simulation results and the theoretical predictions. For simulating Graphene, a user-defined material is introduced to TCAD-SILVACO software which includes all electrical and optical properties of this novel 2D material. Graphene optical properties, specifically at near-IR region(up to 2um wavelength), have been extracted from the real measurement results. Graphene is a Si-compatible material which can provide a sensitive IR detector integrated with other Si-based devices
