CSN08704

Data, Audio, Video and Imageshttp://asecuritysite.com/comms

Telecommunications

Prof Bill Buchanan

3. Modulation and Multiplexing

CSN08704

Data, Audio, Video and Imageshttp://asecuritysite.com/comms

Telecommunications

Prof Bill Buchanan

3. Modulation and Multiplexing:

Modulation

Amplitude Modulation

carrier

signal

V

Vm

AM

• 10Hz carrier.

• 1Hz signal.

• m=0.5.

• Link.

http://www.asecuritysite.com/comms/plot02

FM

• 10Hz carrier.

• 1Hz signal.

• Link.

http://www.asecuritysite.com/comms/plot02?m=0.5&freq=10&freqs=5&type=fm

CSN08704

Data, Audio, Video and Imageshttp://asecuritysite.com/comms

Telecommunications

Prof Bill Buchanan

3. Modulation and Multiplexing: Digital

Modulation

ASK, PSK and FSK

1 1 0 1 0

ASK

PSK

FSK

ASK

• 15Hz.

• Link.

http://www.asecuritysite.com/comms/plot03

FSK

• 15Hz.

• Link.

http://www.asecuritysite.com/comms/plot03

PSK

• 15Hz.

• Link.

http://www.asecuritysite.com/comms/plot03

M-ary modulation

Amplitude 1

Amplitude 2

Amplitude 3

Amplitude 4

Phase 1

Phase 2Phase 3

90°

0°180°

270°

FDM and TDM

Radio

station 3

Radio

receiver

Receiver tuned to

pick-up only in a range

of carrier frequenciesRadio

station 1

Radio

station 2

Time slot 1

Time slot 2

Time slot 3

Time-division multiplexor

Source 1

Source 2

Source 3

CSN08704

Data, Audio, Video and Imageshttp://asecuritysite.com/comms

Telecommunications

Prof Bill Buchanan

3. Modulation and Multiplexing: Digital

Carrier Frequencies

Carrier Frequenciesf

u

Cosmic

rays

Gamma

rays

X-rays Ultra-

violet

Light Infra-

red

Micro-

waves

Radio

waves

0.3-3 GHz UHF (ultra-high frequencies)

3-30 MHz SHF (super-high frequencies)

30-300 GHz EHF (extremely high frequencies)

400 nm 700 nm3 nm

30-300 Hz ELF (extremely low frequencies)

0.3-3 kHz VF (voice frequencies)

3-30 kHz VLF (very low frequencies)

30-300 kHz LF (low frequencies)

0.3-3 MHz MF (medium frequencies)

3-30 MHz HF (high frequencies)

30-300 MHz VHF (very high frequencies)

30 Hz300 MHz300 GHz3 pm

r

cu

CSN08704

Data, Audio, Video and Imageshttp://asecuritysite.com/comms

Telecommunications

Prof Bill Buchanan

3. Modulation and Multiplexing