Chapter 4 : Amplitude Modulation and Demodulation, PPT, ADC, Semester, Engineering - Computer Science Engineering (CSE) PDF Download

Amplitude Modulation and Demodulation in MATLAB

The slides cover the following topics:

Characteristics of a Radio Signal

The Different Types of Analog Modulation

Definition of Modulation

Instantaneous Frequency

Amplitude Modulation

Block Diagram for AM/Large Carrier

Coherent Demodulation

Non-Coherent Demodulation

Non-Coherent Demodulation

Implementing Coherent Demodulator

Amplitude Modulation and Demodulation-------------------------Next Slide------------------Dr. Jay Weitzenn

Characteristics of a Radio Signal

• The purpose of telecommunications is to send information from one place to another
• To convey information, some characteristic of the radio signal must be altered (I.e., ‘modulated’) to represent the information
• The sender and receiver must have a consistent understanding of what the variations mean to each other
• RF signal characteristics which can be varied for information transmission:
– Amplitude
– Frequency
– Phase

Amplitude Modulation and Demodulation-------------------------Next Slide------------------Dr. Jay Weitzenn

The Different Types of Analog Modulation

• Any characteristic of a radio signal can be used as a vehicle for information
• AM has been used since the early days of radio
– simple to generate & detect
– vulnerable to interference,

– Examples: AM broadcasting, aeronautical radio, CB, TV picture
• FM has been used since 1950’s
– less vulnerable to interference & noise
– somewhat more complex to generate and detect
– Examples: FM broadcasting,

Amplitude Modulation and Demodulation-------------------------Next Slide------------------Dr. Jay Weitzenn

Definition of Modulation

• Let m(t) be an arbitrary modulating (information) waveform. (could be either analog or digital)
• Let c(t)=cos(ω_ct +φ) be the carrier

The argument of the sinusoid is the instantaneous phase (ω_ct +φ)
 

Amplitude Modulation and Demodulation-------------------------Next Slide------------------Dr. Jay Weitzenn

Instantaneous Frequency

• The instantaneous frequency is given by
d/dt (ω_ct +φ) = ω_c +d/dt(φ(t))
 

Amplitude Modulation and Demodulation-------------------------Next Slide------------------Dr. Jay Weitzenn

Amplitude Modulation

• X(t)=m(t) cos(ct +)
• If x(t)=(1+m(t)) cos(ct +) where |m(t)| < 1, and m(t) is analog, we have ordinary AM modulation as used in AM radios

Amplitude Modulation and Demodulation-------------------------Next Slide------------------Dr. Jay Weitzenn

Block Diagram for AM/Large Carrier

Amplitude Modulation and Demodulation-------------------------Next Slide------------------Dr. Jay Weitzenn

Coherent Demodulation
 

Amplitude Modulation and Demodulation-------------------------Next Slide------------------Dr. Jay Weitzenn

Non-Coherent Demodulation

Amplitude Modulation and Demodulation-------------------------Next Slide------------------Dr. Jay Weitzenn

Implementing Non-Coherent Demodulator

Amplitude Modulation and Demodulation-------------------------Next Slide------------------Dr. Jay Weitzenn

Implementing Coherent Demodulator