COMMUNICATION THEORY

Amplitude (Linear) Modulation Baseband and carrier communication, Generation of AM (DSBFC) and its spectrum, Power relations applied to sinusoidal signals, DSBSC-Multiplier modulator, Non-linear generation, Switching modulator, Ring modulator and its spectrum, Modulation index. SSBSC, ISB and VSB, Their generation methods and comparison, AM broadcast technical standards. Angle Modulation Instantaneous frequency, Concept of angle modulation, Frequency spectrum, Narrowband and wideband FM, Modulation index, Bandwidth, Phase modulation, Bessels function and its mathematical analysis, Generation of FM (Direct and indirect method), Comparison of FM and PM. AM and FM Receivers Block diagram of AM and FM receivers, Superheterodyne receiver, Performance characteristics: Sensitivity, Selectivity, Fidelity, Image frequency rejection, IFRR. Tracking, De-emphasis, Mixers. AM Detection : Rectifier detection, Envelope detection. Demodulation of DSBSC : Synchronous detection. Demodulation of SSBSC : Envelope detection. FM Detection using PLL. Noise Sources of noise, Types of noise, White noise, Thermal noise, Shot noise, Partition noise, Low frequency or flicker noise, Burst noise, Avalanche noise, Signal to noise ratio, SNR of tandem connection, Noise figure, Noise temperature, Friss formula for noise figure, Noise bandwidth. Behaviour of Analog Systems in Presence of Noise Baseband systems, Amplitude modulated systems - DSBSC, SSBSC and AM, Angle modulated systems - Phase modulation, Frequency modulation, Threshold in angle modulation, Pre-emphasis and De-emphasis in FM, Comparison of performance of AM and FM systems. Digital Transmission of Analog Signals Band limited and time limited signals, Narrowband signals and systems, Sampling theorem in time domain, Nyquist criteria, Types of sampling - Ideal, Natural, Flat top, Aliasing and aperture effect. Pulse analog modulation: PAM, PWM and PPM. PCM - Generation and reconstruction, Bandwidth requirement of PCM. Differential PCM, Delta modulation and adaptive DM. (Only block diagram treatment).