Browsing by Author "Befekadu, Endale"

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    Frequency Hop Spread Spectrum System Communication System
    (Addis Ababa University, 2003-01) Befekadu, Endale; Gopal, Devrajan (Professor)
    Among the various types of the spread spectrum systems the slow frequency hop spread spectrum system is discussed.In the transmitter the data input ,which is, text is converted to binary data by the ASCII code conversion table.This binary data is modulated using the the FSK modulator.Then pseudo-random frequencies are generated from pseudo-random code generators and a frequency synthesizer. Using these generated frequencies the modulator output signal is hopped or spread to different frequencies. After the spreading process, the final signal output is then transmitted through a non Gaussian plus Gaussian noise channel. At the receiver before the demodulation process the initial estimate of the receiver phase is made using the sequential detection method. Using the intial estimate of the phase the rest of the received phase is tracked using a second order tracking loop. After tracking the phase at the receiver end the next step is to dispread the frequency hopped signal. Then demodulation is carried out using the matched filter FSK detector .After detection the data output of the demodulator is converted back to text using the ASCII code table. Finally the receiver gets back the text data which was sent at the transmitter