Previous year question paper for ACS (B-TECH electronics and communication engineering 4th)

Unit I Base Band Signals and Systems: Introduction, Elements of communication system, Noise & its types; Noise

Figure & noise factor, Noise equivalent temperature. Modulation & Demodulation, Mixing; Linear & Nonlinear,

need of modulation, types of modulation systems, basic transmission signals, Frequency multiplexing

technique.

Unit II Analog Modulation Techniques: Introduction, theory of amplitude modulation; AM power

calculations, AM current calculations, AM modulation with a complex wave, theory of frequency modulation; 

mathematical analysis of FM, spectra of FM signals, narrow band of FM, Wide band FM, Theory of

phasemodulation, phase modulation obtained from frequency modulation, comparison of AM & FM,

Comparison of PM & FM.

Unit III AM Transmission: Introduction, generation of Amplitude Modulation, Low level and high level

modulation, basic principle of AM generation; square law modulation, Amplitude modulation in amplifier

circuits, suppressed carrier AM generation (Balanced Modulator) ring Modulator, Product Modulator/balanced

Modulator.

Unit IV AM Reception: Receiver Parameters; Selectivity, Sensitivity, Fidelity, Tuned Ratio Frequency (TRF)

Receiver, Super heterodyne Receiver; Basic elements of AM super heterodyne Receiver; RF Amplifier,

Neutralization of RF Amplifiers, Class of operation of RF Amplifiers, High power RF Amplifiers, Image

Frequency Rejection, Cascade RF Amplifier, methods of increasing Bandwidth, frequency Conversion and

Mixers; Additive Mixing, Bipolar Transistor Additive Mixer, self exicted Additive Mixers, multiplicative

mixing, Multiplicative Mixer using dual gate MOSFET, Tracking & Alignment, IF Amplifier, AM detector;

square law detector, Envelope or Diode detector, AM detector with AGC, Distortion in diode detectors, AM

detector Circuit using Transistor, Double hetro-dyne receiver, AM receiver using a phase locked loop (PLL),

AM receiver characteristics.

Unit V FM Transmission: FM allocation standards, generation of FM by direct method, varactor diode

Modulator, Cross by Direct FM Transmitter, Phase-Locked-Loop Direct FM Transmitter, Indirect generation of

FM; Armstrong method, RC phase shift method, Frequency stabilised reactance FM transmitter.

Unit VI FM Reception: Frequency demodulators, Tuned circuit frequency discriminators; Slope Detector,

Balance Slope Detector, Foster Seeley discriminator, Ratio Detector, FM detection using PLL, Zero crossing

detector as a Frequency Demodulator, quadrature FM demodulator, pre emphasis and de emphasis, limiter

circuits, FM Capture effect, FM receiver, FM stereo transmission and reception, Two way FM Radio

Transmitter and Receiver.

Unit VII SSB Transmission: Introduction, Single Side band systems, AM-SSB; Full carrier, Suppressed

carrier , reduced carrier, Independent side band, and Vestigial side band, Comparison of SSB Transmission to

conventional AM, Generation of SSB; Filter method, Phase Shift Method, Third Method.

Unit VIII SSB Reception: SSB Product Demodulator, Balanced Modulator as SSB Demodulator, Single Side band

receivers; Single side band BFO Receivers, Coherent Single side band BFO Receivers, Single Side band Envelop

detection receiver, Multi Channel Pilot Carrier SSB Receiver.

Unit IX Pulse Modulation Transmissions and Reception: Introduction, Sampling Theorem Pulse Amplitude

Modulation (PAM), Natural PAM Frequency Spectra for PAM , Flat-top PAM, Sample and hold circuits, Time

division Multiplexing, PAM Modulator Circuit, Demodulation of PAM Signals, Pulse Time Modulation

(PTM); Pulse Width Modulation(PWM), Pulse Position Modulation (PPM), PPM Demodulator