Note for COMMUNICATION SYSTEM ENGINEERING - CSE By Muzehe Dieudonne

Topics ( 6 )

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Communication Systems • Chap 1 Linear Modulation/Amplitude Modulation Need for modulation-Bandpass systems and signals-modulation index-maximum allowable modulation-power calculation-signals and spectra of AM, DSB, SSB and VSB signals-generation of AM waves: product modulator-square law and balanced modulatorswitching modulator-Detection of AM: envelope detection and synchronous detection-Modulation and demodulation methods of DSB-SC, SSB, and VSB. • Chap2. Exponential Modulation/Angle Modulation Frequency modulation-phase modulation-relation between FM and PM-compare FM and AM-spectra for FM-power and bandwidth of FM signals-phasor diagram of FM signals-effect of the modulation index on bandwidth-generation of FM signals-indirect (Armstrong) method-direct method-demodulation of FM-narrowband and wideband modulation-compare NBFM and WBFM.

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Content cont’d • Chap 3 Noises Theory Sources of noise - shot noise - resistor noise - calculation of noise in linear systems - noise bandwidth - available power - noise temperature - noise in two-port networks – noise figure-measurement of noise figure - signal in presence of noise - narrow band noises. • Chap 4. Radio Transmitter and Receiver AM and FM radio transmitter-super heterodyne principle-broadcast receiver-communication receiver-Automatic gain control (AGC) Automatic frequency control (AFC). • Chap 5. Noise Performance of AM and FM Receivers Noise in AM receivers threshold effect, Noise in FM receivers capture effect, FM threshold effect, FM threshold reduction, Pre-emphasis and deemphasis in FM, Comparison of performance of AM and FM systems.

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A Communication System • conveys information from its source to a destination some distance away.

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A communication system • Purpose of a communication system: convey information through a medium or communication channel. • The information is often represented as a baseband signal , i.e. a signal whose spectrum extends from 0 to some maximum frequency. • Proper utilization of the communication channel often requires a shift of the range of baseband frequencies into other frequency ranges suitable for transmission, and a corresponding shift back to the original frequency range after reception. • A shift of the range of frequencies in a signal is accomplished by using modulation, which is defined as the process by which some characteristic of a carrier is varied in accordance with a modulating (signal)