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.

FM• 10Hz carrier.• 1Hz signal.• Link.

CSN08704

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

Telecommunications

Prof Bill Buchanan

3. Modulation and Multiplexing: Digital Modulation

ASK, PSK and FSK1 1 0 1 0

ASK

PSK

FSK

ASK• 15Hz.• Link.

FSK• 10/20Hz .• Link.

PSK• 15Hz.• Link.

M-ary modulation

Amplitude 1

Amplitude 2

Amplitude 3

Amplitude 4

Phase 1

Phase 2Phase 3

90°

0°180°

270°

FDM and TDM

Radiostation 3

Radioreceiver

Receiver tuned topick-up only in a rangeof carrier frequenciesRadio

station 1

Radiostation 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 Frequenciesfu

Cosmicrays

Gammarays

X-rays Ultra-violet

Light Infra-red

Micro-waves

Radiowaves

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

Circuit and Packet Switching

Circuit-switching

Packet-switching

possible routes

fixed routePSE

CSN08704

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

Telecommunications

Prof Bill Buchanan

3. Modulation and Multiplexing