Articles in This Issue
Abstract
In recent years, symbolic analysis has become a well-established technique in circuit analysis and design. The symbolic expression of network characteristics offers convenience for frequency response analysis, sensitivity computation, and fault diagnosis. The aim of the paper is to present a method for symbolic analysis that depends on the use of the wavelet transform (WT) as a tool to accelerate the solution of the problem as compared with the numerical interpolation method that is based on the use of the fast Fourier transform (FFT).
Abstract
A theoretical analysis is presented to calculate the signal phase shift and the gain coefficient associated with two-wave mixing in photorefractive crystals subjected to an external electric field. The relative position of the induced-refractive index grating with respect to the fringe pattern of the two input optical beams leads to a coupling effect between the phase and intensity of these beams. An optical logic operation system that is based on photorefractive two-wave mixing is introduced. This system uses the fringe-shifting techniques that are executed by a Mach-Zehnder interferometer. The proposed system configurations are capable of producing all the basic 16 two-operand Boolean functions simultaneously at different output planes.
Abstract
A single phase boost rectifier circuit is studied with and without feedforward techniques. The circuit is implemented and tested experimentally. It can be operated at high power factor (greater than 0.99), and at line current total harmonic distortion (THD) (less than 0.06), by selecting a suitable control parameters at the desired output power.
Abstract
Soft commutation techniques have been of great interest during the last few years in power supply switching applications. The recently developed Zero-Voltage transition (ZVT) and Zero-Current transition (ZCT) pulse width modulation (PWM) technique incorporated soft-switching function into PWM converters, so that the switching losses can be reduced with minimum voltage/current stresses and circulating energy. The ZCT technique can significantly reduce the switch turn-off loss which is usually the dominant switching loss in high-power applications. In this paper the steady state analysis and design of the ZCT PWM boost converter are introduced. Control and drive circuit have been designed to drive a 100 Watt ZCT PWM boost converter to experimentally investigate its features and characteristics.
Abstract
Soft-switching technique can substantially improve the performance of power converters, mainly due to the increase of switching frequency, that result in better modulation quality. This is more concerned particularly in the high power applications, where devices [gate turn off (GTO) or something else similar) can not operate over a few hundreds of hertz in conventional hard switching converter structures. In this paper, design and analysis of moderate power ZCT three-phase PWM inverter has been presented. Also, the designed inverter and its novel control circuit is implemented experimentally to investigate its characteristics with this new zero-current transition ZCT technique.
Abstract
This paper presents a simplified control method for three-phase active power filter by calculating the required reactive and harmonics current of the load. The active power filter needs this current to correct the power factor and eliminate the generated harmonics by nonlinear loads. This method has the advantages of using only one current sensor and effectiveness in achieving the required compensation characteristics. The proposed circuit may be operate at frequencies ranging from 40 to 60 Hz, and it also responds very fast under sudden changes in the load conditions. The considered system is analyzed and a prototype is also developed and tested to demonstrate the performance of the implemented active power filter in the power factor improvement and harmonics elimination. Finally, predicted results are verified experimentally.
Abstract
Analysis and performance predictions of optical frequency division multiplexing (OFDM) receivers incorporating semiconductor optical amplifier (SOA) demultiplexer are presented. The analysis takes into account the influence of finite laser linewidth and various noise sources associated with the optically preamplified detection system. The results indicate clearly that the normalized crosstalk level must be kept below 10.8 dB to prevent the occurrence of a bit-error-rate (BER) floor at a level greater than $10^{-9}$
Abstract
The reliability and feasibility of optical coherent communication system are strongly conditioned by laser phase noise and fluctuations of the state of polarization (SOP) of the optical field at the output of conventional single mode fiber. The double frequency parameter shift keying (DFPSK) system has been proposed in the literature as an efficient scheme that allows compensation of both effects by sending a reference channel that is suitably frequency shifted by using polarization modulation. This paper presents a comprehensive theoretical analysis for the performance of this system in the presence of dichroism which is introduced when the transmission channel has polarization dependent losses or amplifications. The results indicate that the performance of DFPSK system is affected by dichroism even in the low noise frequency regime.
Abstract
Recently, Jones matrix parameter shift keying (JMPSK) technique has been proposed in the literature to achieve phase noise and polarization state insensitive optical communication systems. The aim of this paper is to examine the performance of this system in the presence of system impairments, namely channel dichroism. A comprehensive analysis is presented to assess the effect of dichroism on the bit-error-rate (BER) characteristics of JMPSK receiver.
Abstract
This paper presents a comprehensive analysis of a new direct detection polarization shift keying (DD POLSK) receiver structure that is based on Jones matrix technique. The bit - error rate (BER) characteristics of the receiver is examined under system impairments and the results are compared with those related to other DD POLSK receivers reported in the literature. The results indicate that Jones matrix receiver is less sensitive to optical amplifier gain variation when compared with other receivers.