Design and Fabrication of Unbalanced Wilkinson Power Divider with Equal Port Impedances and Filtering Response with Coupled Metamaterial Transmission Lines
Yalda
Torabi
Department of Electrical and electronic engineering, Shahed University, Tehran, Iran.
author
Gholamreza
dadashzadeh
Department of Electrical and electronic engineering, Shahed University, Tehran, Iran.
author
text
article
2018
per
In this paper, an unbalanced Wilkinson power divider with small dimensions and equal port impedances is presented. The proposed structure is designed by employing two metamaterial coupled-line filters instead of two quadrature-wave impedance transformers in the conventional Wilkinson power divider with the capability of unequal power splitting and favorable selectivity with filtering response. Employing coupled metamaterial transmission lines without using any quadrature-wave impedance transformers in the input and output terminals leads to a significant (more than 65%) reduction in the size of proposed structure compared to the dimensions of its conventional type due to the equal port impedances of the terminals. The proposed power divider has been designed and simulated to work at 1.32 GHz in HFSS and ADS software, and a prototype has been developed and tested to verify the results. The good conformity between simulation and measurement results has been obtained indicating the suitability of the proposed structure and the design method.
Applied Electromagnetics
Imam Hussein University
2645-5153
6
v.
1
no.
2018
1
8
https://elemag.ihu.ac.ir/article_204544_bb088335d9e2dea3985434e39f42b543.pdf
Instability of ultrasonic waves in a semiconductor quantum medium
Ahmad
Mehramiz
Imam Khomeini International University, Qazvin
author
mona
hosseinzade firouzi
imam Khomeini international university
author
text
article
2018
per
Abstract- In this research, an analytical investigation has been performed on instability and excitation of ultrasonic waves in a semiconductor medium by the application of a high-frequency electric field. To this end, using a set of basic hydrodynamic equations including quantum corrections, dispersion relations of the ultrasonic waves in the presence of electric field calculated and the possibility of waves instability in the quantum regime is investigated. The results show that the high- frequency electric field, near the electron-plasma frequency, produces a nonlinear coupling between the ultrasonic waves and electron-plasma waves and leads to an instability which can be increased by quantum effects.
Applied Electromagnetics
Imam Hussein University
2645-5153
6
v.
1
no.
2018
9
14
https://elemag.ihu.ac.ir/article_204602_ea399f5ea1c188c492ee1be8b96560ac.pdf
Simulation and Fabrication of Tapered Fiber Optics Hydrogen Sensor
Ali
Riahi
Imam Hossein University
author
Mahdi
Heydari-Dayeni
School of Physics, Iran University of Science and Technology
author
mohammad
vahedi
Iran University of Science and Technology
author
Javad
Khalilzadeh
ihu
author
yadollah
shahamat
ihu
author
text
article
2018
per
In this paper, we report simulation and fabrication of a gas sensor based on tapered fiber by measuring the output power in the presence of different hydrogen concentrations. The fibers were tapered to 15.5 μm and 26.6 μm by using oxy-butane torch and the output spectrum is obtained using a 1550nm laser source and an optical spectrum analyzer (OSA) and the sensitivities of the tapered fiber sensors were determined. It is shown that by increasing the percentage of the hydrogen in the surrounding environment, the output power is changed by 7% and 2.3% in the presence of 4% hydrogen for tapered fibers of diameter 15.5μm and 26.6 μm respectively. The response time of the aforementioned sensors were 13 and 17.6 seconds respectively. In addition, the repeatability tests of the fabricated sensors demonstrates acceptable results. Simulation of the tapered fiber sensors demonstrates good agreement with experimental results. The obtained sensitivity makes hydrogen detection below 4% easy and accurate.
Applied Electromagnetics
Imam Hussein University
2645-5153
6
v.
1
no.
2018
15
21
https://elemag.ihu.ac.ir/article_204603_9cd83f5bde0d376bca1615dfdae2ac9c.pdf
Field Oriented Control of BLDC Motor Drive Using Space Vector Modulation
Hossein
Torkaman
Shahid Beheshti University
author
milad
bhnamfar
Shahid Beheshti University
author
text
article
2018
per
The space vector modulation in a brushless DC motor (BLDC) with a permanent magnetic rotor is different from conventional motors due to the silent phases and trapezoidal back EMF. To overcome this problem, in this paper, an SVPWM method is proposed for field-oriented control of the BLDC motor drive. The main differences in the implementation of this method are the torque estimation and the presentation of the space vectors of the inverter voltage specified. In order to control the effective and direct torque, the torque is calculated in terms of the electromagnetic force and the three-phase current. According to the torque error between the given torque and the reference torque, the best voltage vector is selected, which performs the dynamic performance of the BLDC motor as a direct torque control system. As a result, it is expected to have a better dynamic response to load variations.. . . . . . . . ..
Applied Electromagnetics
Imam Hussein University
2645-5153
6
v.
1
no.
2018
23
29
https://elemag.ihu.ac.ir/article_204604_4c8eba618e88e513e97ea6a003faa418.pdf
Beam width expansion of microstrip array antenna by wide angle impedance matching layer
mahboube
Safari Dehnavi
malek ashtar university of technology
author
sayed mohammad javad
razavi
malek ashtar university of technology
author
S. Hossein
Mohseni Armaki
malek ashtar university of technology
author
text
article
2018
per
In this paper, a new method for calculation the active reflection coefficient of an array antenna has been proposed, and accordingly an anisotropic wide angle impedance matching layer has been designed to mitigate blind spots. The designed antenna consists of a microstrip array with rectangular arrangement. The space between the elements in the mentioned array is equal with 0.63 wavelength in X band. In order to compensate the impedance mismatch near the blind spots between the antenna and the free space above the aperture and also to increase the antenna scan range, the anisotropic matching layer characteristics are extracted by genetic algorithm optimization method. Finally, its efficiency is investigated in CST Microwave Studio and HFSS software. Compared with other similar techniques, the proposed method is simpler, faster, and does not require to fabricate and coupling coefficients measurement. It is a powerful tool for deriving the active reflection of microstrip array antenna that is difficult to extract their analytical equations. The designed wide-angle impedance matching layer has increased the scan range of antenna from ±34° to ±42° by shifting blind spots.
Applied Electromagnetics
Imam Hussein University
2645-5153
6
v.
1
no.
2018
31
39
https://elemag.ihu.ac.ir/article_204605_1517acaded6411b172d6ce489b3417d1.pdf
EIT-based nanostructure detectors for detecting materials using terahertz waves
jalil
shiri
Imam Hossein Comprehensive University
author
Abdollah
Malekzadeh
Imam Hossein Comprehensive University
author
text
article
2018
per
Different materials have different absorption spectra of the terahertz (THz) radiation. So, by detecting the absorption spectra of THz radiation of different materials we can assess material substances. We propose and analyze an efficient way to detect the THz radiation in a magnetized graphene system via electromagnetically induced transparency (EIT). In this paper an all-optical method for THz signal detection in graphene nanostructure in core of a detector is investigated. Such a scheme for THz signal detection mainly relies on the measurement of probe transmission spectra, in which the behaviors of a weak-probe transmission spectrum can be controlled by switching on/off the THz signal radiation. Taking into account the tunable optical transition frequency between the Landau levels in graphene, our analytical results demonstrate that a broad frequency bandwidth of the THz signal radiation can be inspected and modulated by means of an external magnetic field. This feature being useful for detection of explosives with width absorption spectra of the optical terahertz signal. Common explosives such as RDX, TEND and Ammonium Nitrate in the spectral range of THz signal are widely used in a variety of explosives. Effects of parameters such as intensity of the terahertz radiation and relative phase between the fields on the absorption anddispersion of probe field hase been studied. Also, Detector sensitivity and rapid response to fluctuations of terahertz radiation by measuring the switching time of group velocity of probe field from subluminal to superluminal and vice versa hase been studied. The estimated range of the switching time is between 5 ps to 8 ps for subluminal to superluminal light propagation.Such all optical detectors can be well used in a wide range of THz spectroscopy for (explosive or forbidden) material detection.
Applied Electromagnetics
Imam Hussein University
2645-5153
6
v.
1
no.
2018
41
48
https://elemag.ihu.ac.ir/article_204606_db13dc74b5b12a8d6bd1a55f45571e67.pdf