Anna University Regulation 2017 IT EC8394 ADC Notes, Analog Digital Circuits Engineering Lecture Handwritten Notes for all 5 units are provided below. Download link for IT 3rd SEM EC8394 Analog Digital Circuits Engineering Lecture Handwritten Notes are listed down for students to make perfect utilization and score maximum marks with our study materials.

1. Define Modulation.
Modulation is defined as the process by which some parameter of a high frequency carrier signal such as amplitude, frequency or phase is varied in accordance with the instantaneous value of low frequency message signal (modulating signal).

2. List out the reasons for using modulation.
The reasons for using modulation are:
(a) Size of antenna increases as frequency decreases.
(c) Less Noise and Interference.
(d) Bandwidth gets increased.
(e) Transmitting power gets decreased.
(f) Frequency re-allocation is possible.

3. Define amplitude Modulation.
Amplitude Modulation is the process of changing the amplitude of a relatively high frequency carrier signal in proportion with the instantaneous value of the modulating signal.

4. Define Modulation index and percent modulation for an AM wave.

Modulation index is a term used to describe the amount of amplitude change present in an AM waveform. It is also called as coefficient of modulation.

Mathematically modulation index is m

m = Em/Ec

where m = modulation coefficient

Em = Peak change in the amplitude of the output waveform voltage.

Ec = Peak amplitude of the unmodulated carrier voltage.

m = ( Vmax-V Vmin) )/(Vmax +Vmin)

m gives the amount of amplitude change in the modulating signal

Percent modulation gives the percentage change in the amplitude of the output wave when the carrier is acted on by a modulating signal.

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