Communication Theory
Modulation and Channels
Modulation and Channels
Communication Theory
Slide 1
Communication System
 Today’s lecture: focus on dashed boxes
Modulation and Channels
Communication Theory
Slide 2
BFSK Modulator
 Choose between two frequencies
Modulation and Channels
Communication Theory
Slide 3
BPSK Demodulator
 Mix input with coherent reference
Modulation and Channels
Communication Theory
Slide 4
BPSK Modulator
 Choose between two phases
Modulation and Channels
Communication Theory
Slide 5
BPSK Demodulator
 Mix input with coherent reference
Modulation and Channels
Communication Theory
Slide 6
QPSK Modulator
 Transmit one of 4 symbols
– In-phase and quadrature components
Modulation and Channels
Communication Theory
Slide 7
QPSK Demodulator
 Evaluate in-phase and quadrature components
seperately using coherent reference
Modulation and Channels
Communication Theory
Slide 8
OQPSK Modulator
 Reduce intensity of phase change in QPSK
Modulation and Channels
Communication Theory
Slide 9
MSK Modulator
 Do away with sharp changes in phase
Modulation and Channels
Communication Theory
Slide 10
Pulse Shapes
 Combat ISI by replacing square pulses with
smoother ones
Modulation and Channels
Communication Theory
Slide 11