Chapter-3 Angle Modulation Introduction to Communication Systems (CNET - 222) Mr. Haneef Khan Department of Computer Networks College of CS&IS Jazan University, Jazan.

Objectives 1. Analog Modulation and its types. 2. Basics of Sine and Cosine in term of amplitude, frequency and phase. 4. Frequency Modulation concept, equations and waveforms 5. Phase Modulation concept, equations and waveforms. 6. Numerical on FM and PM.

Introduction There are three parameters of a carrier that may carry information: Amplitude Frequency Phase Frequency and Phase modulation are closely related and grouped together as phase modulation.

These two constitute angle modulation. Types of Modulation Carrier Variations Amplitude Frequency Phase Types of Information Analog Digital These two constitute angle modulation.

Sine Signal And Cosine Signal Sine waveform Cosine waveform A sinusoid, meaning a sine wave -or- a cosine wave, is the basic building block of all signals.

What is Amplitude, Frequency, and Phase ? Vary one of these parameters Amplitude Frequency Phase Angle modulation is a variation of one of these two parameters.

Difference between Amplitude, Frequency and Phase

Understanding Phase vs. Frequency To understand the difference between phase and frequency, a signal can be thought of using a phasor diagram. The distance from the center is the signal's amplitude. The angle from the positive horizontal axis is the phase. phase V

Understanding Phase vs. Frequency (change phase)/(change time) The change in the phase over time (the phase velocity) is the signal's frequency.

Signals vs NASCAR F In signals, we track the signal by its phase. This is its position on the phasor diagram. In NASCAR, we track each car by its position on the track.

Signals vs NASCAR In NASCAR, we track a car's velocity by how fast it goes around the track. In signals, we track the signal's velocity by its frequency. This is how fast it goes around the phasor diagram.

Frequency Modulation(FM) FM is technique of transmitting message signal using a radio-frequency carrier signal. The frequency of the carrier signal is varied accordance with the amplitude of the message signal, the amplitude of the carrier signal remain unchanged.

FM Waveform

Equations Message Signal vm = Vm sin(ωm + ϕm) 2. Carrier Signal vc = Vc sin(ωct + ϕc) Where, vm , vc = Instantaneous value of message and carrier signal. ωm , ωc = Angular velocity ϕm , ϕc = Phase Angle ωt represent angle in radian.

3. Modulated Signal vFM = Vc sin(ωct + mf cos ωmt) Where, δf = Maximum deviation mf = Modulation Index = δf /fm

Advantages of FM Disadvantages of FM 1. Resilient to noise. 2. Resilient to signal strength variations. 3. Does not require linear amplifiers in the transmitter. 4. Enables greater efficiency than many other modes. Disadvantages of FM 1. Requires more complicated demodulator. 2. Much more Bandwidth 3. Sidebands extend to infinity either side.

Phase Modulation Phase modulation is a technique or a system in which the amplitude of the carrier signal is kept constant, while phase and rate of phase change are varied with accordance of message signal. The amount by which the carrier phase is varied from its original value, called as the phase deviation.

Waveform of PM

Equations Message Signal vm = Vm sin(ωm + ϕm) 2. Carrier Signal vc = Vc sin(ωct + ϕc) Where, vm , vc = Instantaneous value of message and carrier signal. ωm , ωc = Angular velocity ϕm , ϕc = Phase Angle ωt represent angle in radian.

3. Modulated Signal vPM= Vc sin(ωct + ϕc +mp cos ωmt) Where, mp = Modulation Index) = δp δp = Maximum deviation

Advantage of PM Disadvantages of PM 1.Phase modulation is increased immunity to noise. 2.Phase modulator is used in determining velocity of moving target by extracting Doppler information. Disadvantages of PM 1. Phase ambiguity comes if we exceed its modulation index pi radian(180 degree). 2. We need frequency multiplier to increase phase modulation index.

Examples

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