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July-2013

Volume: 15, Issue: 1, July 2013

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Overshoot Improvement for Indirect Frequency  Synthesizer Phase Locked Loop

Authors: Akram Al-Harasees, Ghadah O. Al-maaitah

Abstract:

This paper presents an model for indirect frequency synthesizer, besides a simulation model by using ORCAD simulator. The main purpose in this paper is to make tradeoffs between settling time and overshoot of frequency synthesizer’s output signal. The simulation results at 1KHz input frequency give a good a accuracy when the simulator behaviour is compared with a practical model. The proposed method has the capability to reduce the maximum overshoot of the PLL output signal. Finally some approval results in MATLAB model are presented.

(pp. 777-782)                    Download PDF

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Design and Development of Programmable Pulse Generator with decrease in rise and fall Times Using CPLD

Authors: D.Sri Silpa, Dr.P.Narsimha Reddy, Dr.S.Venkatramana Reddy

Abstract:

Pulse generators use digital techniques, analog techniques or combination of both to form output pulse sequences. Simple pulse generators usually allow control of pulse repetition rate (frequency), pulse width and high and low voltage levels of the pulses.  Sophisticated pulse generators may allow control over the rise and fall times of the pulses of the order of nano seconds along frequency, amplitude and low pulse width. Two types of Pulse generators by name (i) programmable and (ii) non-programmable are there. The first ones are software controlled and the other ones are hardware controlled. The hardware controlled pulse generators have fixed modes of operation. In software controlled pulse generators modes of operation can be changed easily. They are flexible. Here we developed a programmable Pulse generator system to produce pulse sequences with variable pulse widths, pulse repetition and height to be used in Deep Level Transient Spectroscopy (DLTS) for characterizing the deep levels in semiconductor materials/junctions. The Pulse generator has been developed using CPLD. The advantage of our Pulse generator is it produces pulses with sharp rise and fall times, with variable pulse width and height. We used VHDL to develop the program. The details of the design and development of the Pulse generator is discussed in the paper. The pulse widths can be varied in Nanoseconds .Fall and rise times can be decreased with the help of DAC AD7302.


(pp. 783-786)                    Download PDF

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