ORIGINAL_ARTICLE
Extension of the Coverage Region of Multiple Access Channels by Using a Relay
From practical and theoretical viewpoints, performance analysis of communication systems by using information-theoretic results is important. In this paper, based on our previous work on Multiple Access Channel (MAC) and Multiple Access Relay Channel (MARC), we analyze the impact of a relay on the fundamental wireless communications concept, i.e., coverage region of MARC, as a basic model for uplink communications between a base station and users with the help of a relay. This analysis includes the coverage region for the MAC as a special case. Considering rate regions for the Gaussian MARC and fading Gaussian MARC, it is proved that in a fixed transmission rate, the relay extends coverage region of the MARC. Numerical illustrations confirm our theoretical results.
https://jce.shahed.ac.ir/article_324_53881c808ccf98515a921b16064b0202.pdf
2015-01-01
1
20
10.22070/jce.2016.324
multiple access relay channel
Coverage region
Fixed desired transmission rates
Cellular network
Ehsan
Moeen Taghavi
e.mtaghavi@gmail.com
1
AUTHOR
Ghosheh
Abed Hodtani
ghodtani@gmail.com
2
LEAD_AUTHOR
ORIGINAL_ARTICLE
Theoretical Analysis of Polarization Rotation angle in Dual Reflector Antenna
Because of special structure, a dual reflector antenna has beam rotation capability in azimuth and elevation directions. In this structure, the antenna beam can be placed in any point in the space by mechanical movement of twist reflector which it is the most important ability of the antenna. Due to the antenna structure, if the polarization of incident wave is linear, it is expected that the polarization of propagated wave is linear and in the direction of desired design. In this paper, for the first time, a nonlinear relation is extracted that it shows the propagated beam polarization has a polarization rotation. This formula is a mathematic closed form relation. These structures are very useful in airborne radar systems.
https://jce.shahed.ac.ir/article_327_026c2a9d03aaeb0eddbbaf535e78d809.pdf
2015-01-01
21
28
10.22070/jce.2016.327
Antenna
beam
dual reflector
feed horn
polarization
trans
reflector
twist reflector
Shervin
Amiri
amiri@irost.ac.ir
1
Dept. of Electrical and Computer Eng.
AUTHOR
Ali
Imani
imani@shahed.ac.ir
2
School of electrical engineering
LEAD_AUTHOR
Mohammad
Soleimani
soleimani@iust.ac.ir
3
School of electrical engineering
AUTHOR
ORIGINAL_ARTICLE
Square Lattice Elliptical- Core Photonic Crystal Fiber Soliton-Effect Compressor at 1550nm
In this paper, we investigate the evolution of supercontinuum and femtosecond optical pulses generation through square lattice elliptical-core photonic crystal fiber (PCF) at 1550 nm by using both full-vector multipole method (M.P.M) and novel concrete algorithms: symmetric split-step Fourier (SSF) and fourth order Runge Kutta (RK4) which is an accurate method to solve the general nonlinear Schrodinger equation (GNLSE). We propose a novel square lattice PCF structure featuring a minimum anomalous group velocity dispersion (GVD), nearly zero third-order dispersion (TOD) and enhanced nonlinearity for efficient soliton–effect compression of femtosecond optical pulses and supercontinuum generation(SCG) with lowest input pulse energies over discrete distances of the fiber.
https://jce.shahed.ac.ir/article_336_10d0c36a84117e9bbedff9bae496a67c.pdf
2015-01-01
29
40
10.22070/jce.2016.336
Multipole
Photonic
Soliton
Compression
Supercontinuum
Dispersion
Ali
Sadr
sadr@iust.ac.ir
1
0
AUTHOR
Ashkan
Ghanbari
ghanbari.ashkan@yahoo.com
2
0
LEAD_AUTHOR
Alireza
Kashani nia
3
0
AUTHOR
ORIGINAL_ARTICLE
Improvement the reflection coefficient of Waveguide-Fed Phased-Array Antenna utilizing Liquid Crystal
Abstract— This work investigates the improvement of the active reflection coefficient of waveguide-fed phased-array antenna using liquid crystal layers. The anisotropy properties of liquid crystal layer can be employed to eliminate blind scan angle and improve the wide angle impedance matching of the waveguide-fed phased array antennas. The authors have expressed the modal analysis of the waveguide-fed phased-array antenna, which is covered with uniaxial anisotropic liquid crystal layers. The analytical method can be used to optimize the wide angle impedance matching over broad angular range of the array. The analytical method is assumed for infinite arrays. The analytical results have been verified using simulation software. In this paper it is proposed to use anisotropic liquid crystal to improve the reflection coefficient of waveguide-fed phased-array antennas. Also it is proposed to employ the reconfigurable properties of liquid crystal to engineering the analytical optimization.
https://jce.shahed.ac.ir/article_326_1879251d50aefd6a7b1a55f882f72f5a.pdf
2015-01-01
41
54
10.22070/jce.2016.326
modal analysis
waveguide
fed phased
array antenna
liquid crystal
ORIGINAL_ARTICLE
Tracking performance of incremental LMS algorithm over adaptive distributed sensor networks
in this paper we focus on the tracking performance of incremental adaptive LMS algorithm in an adaptive network. For this reason we consider the unknown weight vector to be a time varying sequence. First we analyze the performance of network in tracking a time varying weight vector and then we explain the estimation of Rayleigh fading channel through a random walk model. Closed form relations are derived for MSE, MSD and EMSE of analyzed network in tracking Rayleigh fading channel and random walk model. Comparison between theoretical and simulation results shows a perfect match and verifies performed calculations.
https://jce.shahed.ac.ir/article_325_6bf8c67189fd61f5a29615f9ba5b744a.pdf
2015-01-01
55
66
10.22070/jce.2016.325
distributed estimation
incremental strategies
non
stationary environment
Rayleigh fading
Mehdi
Chehel Amirani
m.amirani@urmia.ac.ir
1
Urmia university
AUTHOR
Changiz
Ghobadi
ch.ghobadi@urmia.ac.ir
2
Urmia university
AUTHOR
Javad
Nourinia
j.nourinia@urmia.ac.ir
3
Urmia university
AUTHOR
ehsan
mostafapour
e.mostafapour@urmia.ac.ir
4
Urmia university
LEAD_AUTHOR
ORIGINAL_ARTICLE
A New Design of Log-Periodic Dipole Array (LPDA) Antenna
This paper presents a new approach for design of the log-periodic dipole array antenna (LPDA) based on using of different design parameters in the LPDA elements to control the antenna behavior. In the proposed procedure, the design parameters can control the value of forward gain over the operating frequency range, and also adjust the gain flatness. Furthermore, this design procedure can decrease the LPDA dimensions in compared to the conventional design. Based on the proposed design method, several LPDA antennas are designed and simulated numerically by the method of moment. The simulation results show that this LPDA design procedure can be a good candidate for design of optimized antenna in different frequency band.
https://jce.shahed.ac.ir/article_328_692cef4eaa4cc8bc6ed499878bf06a4e.pdf
2015-01-01
67
75
10.22070/jce.2016.328
Gain control
gain flatness
log
periodic dipole array
miniaturized LPDA
Javad
Ghalibafan
1
AUTHOR
Seyed Mohammad
Hashemi
2
AUTHOR
Seyed Hassan
Sedighy
sedighy@iust.ac.ir
3
LEAD_AUTHOR