Lecture 4 Analog Modulation - Weber State Universityfaculty.weber.edu/snaik/ECE4900_ECE6420/04Lec04_AnalogMod.pdf · ... Digital Communications Lecture 4 Analog Modulation. 2 EE4900/EE6720

1

EE4900/EE6720 Digital Communications Suketu Naik

EE4900/EE6720: Digital Communications

Lecture 4

Analog Modulation

2


Block Diagram of Communication System

Generic Communication SystemQualcomm MDM9635M LTE Modem in iphone6

3


Analog Communication System

Informatio

n (sound,

video, text,

data, …)

Transducer &

A/D Converter Modulator

Output

Signal

D/A Converter

and/or output

transducer

Demodulator LNA,

Filter,

etc.

Channel

= Focus of this lecture

Block Diagram of Communication System

Power

Amplifier +

Filter etc.

4


Basics of Modulation

Wave Equation of the Carrier

Can manipulate either the amplitude, or the

frequency or the phase to carry the information

Amplitude Modulation (AM): Change Amplitude of the Carrier Wave

Frequency Modulation (FM): Change Frequency of the Carrier Wave

Phase modulation (PM): Change Phase of the Carrier Wave

5


Basic Analog Modulation Schemes

Amplitude Modulation (AM)

Information

(baseband signal at

lower frequency)

Carrier signal

at higher

frequency

Up-converted

Baseband

Signal

Simulink Model (In-class exercise)

Hardware Demo (N/A)

Ref: Data Communications, Kwangwoon University

6



Amplitude Modulator Circuit

7



Amplitude Modulation (AM) Equations

m(t)=analog or digital data to be

transmitted=modulating signal

s(t)=output signal=modulated

carrier wave

Ac=RMS level [V]

fc=carrier frequency [Hz]

How can we de-modulate the transmitted AM signal?

Amplitude of the carrier

Wave is modulated

8


AM Demodulation Technique

Local

Oscillator

Received

Signal

Mixer

(Multiplier)

Low

Pass Filter


Remove

DC

Demodulated

Signal

Same Frequency

As the Carrier Signal

9



Frequency Modulation (FM)

Information

(baseband signal at

lower frequency)

Carrier signal

at higher

frequency

Up-converted

Baseband

Signal

Simulink Model (In-class exercise)

Hardware Demo (N/A)


10



Frequency Modulator Circuit

11



Frequency Modulation (FM) Equations

m(t) (=m(σ))=analog or digital data to be


Df=frequency deviation constant [rad/V-s]

Ac=amplitude level [V]


How can we de-modulate the transmitted FM signal?

Frequency of the carrier

wave is modulated

12



FM Demodulation Technique (in DSP!)

Ref: https://www.veron.nl/wp-content/uploads/2014/01/FmDemodulator.pdf

13



Phase Modulation (PM)

Information

(baseband signal at

lower frequency)

Carrier signal

at higher

frequency

Up-converted

Baseband

Signal


14



Phase Modulation (PM)

Binary Phase Shift Keying (BPSK)

15



Phase Modulator Circuit

16



Phase Modulation (PM) Equations

m(t)=analog or digital data to be


Df=frequency deviation constant [rad/V-s]

Ac=amplitude level [V]


How can we de-modulate the transmitted PM signal?

Phase (and frequency) of the

carrier wave is modulated

s(t)

m(t)

17


Assignment 2 [20]

Simulate AM and FM Communication using Simulink

Submit the following:

1) Simulink models

2) Time-domain plots

3) Frequency domain plots

Documents

Lecture 4 Analog Modulation - Weber State Universityfaculty.weber.edu/snaik/ECE4900_ECE6420/04Lec04_AnalogMod.pdf · ... Digital Communications Lecture 4 Analog Modulation. 2 EE4900/EE6720