Post on 01-Feb-2021
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