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Showing 6 results for Najafi

Dr. Esmaeil Najafi Aghdam, Mr. Mohammad Honarparvar,
Volume 2, Issue 1 (6-2014)

Asghar Charmin, Dr. Esmaeil Najafi Aghdam,
Volume 2, Issue 2 (1-2015)

In this study, a dual-mode Delta Sigma modulator for both ‎WLAN and GSM standards has been designed. In order to reduce the power consumption and to ‎optimize the chip area, a reconfigurable structure, which can be separately tuned for these two different ‎applications, is used. The proposed modulator is based on a multi-bit VCO instead of a conventional flash ‎quantizer. Due to the possibility of lower voltage application and lower power consumption, the VCO-‎based Delta Sigma modulator can be a good choice especially for sub-100nm technology, where the ‎performance of the analog circuits becomes limited, and conversely superior switching rates can be ‎achieved. The idea of VCO-based Delta Sigma converter has been recently developed, however the multi-‎mode reconfigurable structure is proposed and analyzed for the first time in this research. The proposed ‎modulator is dedicated to operate with the two major WLAN and GSM standards. It is designed at ‎system level in general, but the VCO part is implemented at transistor level using 180nm CMOS ‎technology. The simulations’ results show a saving of at least 86% of power consumption in the ‎VCO part, in the GSM standard compared to WLAN.‎
Eng. Mehdi Fallah, Dr. Rasool Kazemzadeh, Dr. Esmaeil Najafi Aghdam,
Volume 3, Issue 1 (9-2015)

Steady-state and transient response of the active power filter based on instantaneous power theory compensation method is dependent on the accurately and quickly extract the DC component of load active power. In this paper, for improving the response of this method, the numerical filter based on recursive least squares with variable forgetting factor in order to separation of DC component of load active power is proposed. Unlike conventional low-pass filters, the feature of designed numerical filter is independent of load harmonic components, quick and precision of the answer. Also, using wavelet transform the performance of active power filter under the non-ideal voltage condition is improved. Finally, the second order delta-sigma modulation is used to generate the switching pulses. Simulation results on MATLAB / SIMULINK software shows that the proposed method is properly.
Ph.d Student Tayebeh Azadmousavi, Ph.d Esmaeil Najafi Aghdam ‎, Professor ‎ Javad‎ Frounchi‎,
Volume 6, Issue 2 (2-2020)

This paper presents a new circuit to configure power amplifier (PA) for return-to-zero on-off-keying (RZ-OOK) transmitters. The proposed PA works as a multimode structure with configurable data rate and output power. The programmable data rate function is achieved by duty cycle adjustment of input data and producing input RZ-data by a simple circuit, which leads to a linear scale of data rate with power consumption. This implies that any desired level of output power can be transmitted with different power consumption according to the power budget. The RZ-data is also utilized to perform the output power reconfiguration. The PA represents data rate of 0.3Mb/s to 3Mb/s and it can deliver output power level from -23dBm to 0dBm. During data rate adjustment, power consumption varies from 0.099mW to 0.99mW when the output power is 0dBm. Also, PA consumes 0.07mW to 0.99mW at the output power tuning range with a data rate of 3Mb/s.
Dr Masoud Dashtdar, Dr Mojtaba Najafi, Dr Mostafa Esmaeilbeig,
Volume 7, Issue 1 (9-2020)

Away to decrease the costs of generation and improve the performance of the grid generator, solving the problem of OPF based on line congestion management. As the power flow equation is nonlinear, this paper has performed the PSO algorithm to solve the OPF problem. By considering two technique this paper has performed the PSO algorithm for improving the performance. The first technique is to use a chaos generator to prevent PSO particles from sticking to local minimum points and the second is to consider the GSF in the WPSO algorithm structure so that the power passing through network lines can be simultaneously calculated and real power flow. Finally, the result of  WPSO-GSF algorithm which includes the bus voltage values, line losses, injection power to b buses, power passing through lines, total generation cost, setting electricity prices in two ways, UMP or LMP, depending on filling line capacity and calculating generators' profits has carried out .and also, to check the accuracy of the algorithm, the proposed method has been tested on IEEE 14-BUS, 30-BUS, 57-BUS standard networks, the results which indicate an increase in the speed and accuracy of the WPSO-GSF algorithm compared to other methods in improving the OPF problem.
- Younes Gharedaghi, Dr. Javad Olamaei, Dr. Sajjad Najafi Ravadanegh,
Volume 7, Issue 2 (3-2021)

Robust algorithm is known as the one of high potential models for strengthening in optimization of large and complex distribution networks considering uncertainty. In this research we are looking for some suitable template and appropriate clustering pattern in order to analyze the operation of distribution network. The analysis of optimization process in both individual and adaptive cases of distributed generation sources applied to some standard distribution network shows that the adaptive case of DGs determines less partial and total operation cost. except in islanded case of DGs. The results of clustering approach based on choosing the candidate points which includes DGs and feeders are used in medium voltage (MV) network level. By investigating the software data in both single cluster with first up to fifth and tenth repeatition, one to five clusters and finally ten clusters case shows the superiority of mean data besed clustering. because of having the three following properties such as being sensitive to all weighted candidate points, the speed of acceptable operation and feeding the clusters in islanded case in multiplicity of clusters, it is suitable to designate the robust optimization method using pattern random clustering.

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سامانه های غیرخطی در مهندسی برق Journal of Nonlinear Systems in Electrical Engineering
نشریه سامانه‌های غیرخطی در مهندسی برق در خصوص اصول اخلاقی انتشار مقاله، از توصیه‌های «کمیته بین‌المللی اخلاق نشر» موسوم به COPE و «منشور و موازین اخلاق پژوهش» مصوب معاونت پژوهش و فناوری وزارت علوم، تحقیقات و فناوری تبعیت می‌کند.
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