EEE 400: Communications Systems I First Semester Examination

Communications paper. Describes modulation and demodulation, the modulating and the modulated signal and the analogue modulation systems, then calculates peak envelope power for an amplitude modulated wave with a 500 volt carrier and a message of 0.8 sine 2 pi 1000 t delivered to a 50 ohm load, both normalised and actual. Sets out the components of a basic communication system by block diagram, the bandwidth amplitude and frequency modulation each require, the transmission options open to a system and when each is appropriate, and three reasons for modulating. Continues with the complex envelope representation of a bandpass signal, modulation and demodulation of the double sideband large carrier system with equations, generation of the suppressed carrier form, generation of narrowband and wideband frequency modulation, deviation ratio and bandwidth for a 75 kilohertz deviation with a 15 kilohertz modulating signal, the power efficiency of an amplitude modulated system at modulation index m, the modulation index derived from maximum and minimum signal amplitudes, the synchronisation needed to detect a suppressed carrier, single sideband generation and demodulation, high and low level modulation in transmitters, and the channel allocation of the 530 to 1700 kilohertz amplitude band read against the 88 to 108 megahertz frequency band.