Showing 3 results for Ebrahimzadeh
A. Ebrahimzadeh, S. A. Seyedin,
Volume 1, Issue 4 (October 2005)
Abstract
Automatic signal type identification (ASTI) is an important topic for both the
civilian and military domains. Most of the proposed identifiers can only recognize a few
types of digital signal and usually need high levels of SNRs. This paper presents a new high
efficient technique that includes a variety of digital signal types. In this technique, a
combination of higher order moments and higher order cumulants (up to eighth) are
proposed as the effective features. A hierarchical support vector machine based structure is
proposed as the classifier. In order to improve the performance of identifier, a genetic
algorithm is used for parameters selection of the classifier. Simulation results show that the
proposed technique is able to identify the different types of digital signal (e.g. QAM128,
ASK8, and V29) with high accuracy even at low SNRs.
P. M. Farahabadi, H. Miar-Naimi, A. Ebrahimzadeh,
Volume 5, Issue 1 (March 2009)
Abstract
New equations are proposed for frequency and amplitude of a ring oscillator.
The method is general enough to be used for all types of delay stages. Using exact largesignal
circuit analysis, closed form equations for estimating the frequency and amplitude of
a high frequency ring oscillator are derived as an example. The method takes into account
the effect of various parasitic capacitors to have better accuracy. Based on the loop gain of
the ring, the transistors may only be in saturation or experience cutoff and triode regions.
The analysis considers all of the above mentioned scenarios respectively and gives distinct
equations. The validity of the resulted equations is verified through simulations using
TSMC 0.18 µm CMOS process. Simulation results show the better accuracy of the
proposed method compared with others.
M. Sefidgaran, M. Mirzaie, A. Ebrahimzadeh,
Volume 6, Issue 2 (June 2010)
Abstract
Reliability of a power system is considerably influenced by its equipments.
Power transformers are one of the most critical and expensive equipments of a power
system and their proper functions are vital for the substations and utilities. Therefore,
reliability model of power transformer is very important in the risk assessment of the
engineering systems. This model shows the characteristics and functions of a transformer in
the power system. In this paper the reliability model of the power transformer with ONAN
cooling is obtained. The transformer is classified into two subsystems. Reliability model of
each subsystem is achieved. Markov process representation and the frequency/ duration
approach are employed to obtain a complete reliability model of the subsystems. By
combining these models reliability model of power transformer is obtained. The reliability
model associated with the transformer is then proposed combining the models of
subsystems. The proposed model contains five states. To make the model more applicable,
the 5-state model is alleviated to a 3-state one. Numerical analysis and sensitivity analysis
relevant to the proposed reliability model are performed for evaluating the numerical values
of the model parameters and the impact of different components on the reliability of the
model.
