Digital carrier modulation -...
Transcript of Digital carrier modulation -...
Overview
PPT is for demonstration, not for learning!
Review
– Analog modulations (AM, PM, FM)
– Digital baseband modulations (PAM, PPM, PDM)
Digital carrier modulations: – Basic types:
ASK, OOK
PSK, BPSK, MSK, QPSK, 8PSK, 16PSK, …
FSK, AFSK, MFSK, DTMF, ...
– Quadrature Amplitude Modulation:
2-QAM, 4-QAM, 8-QAM, 16-QAM, 32-QAM, 64-QAM … 4096-QAM
Bálint TÓTH – BME TMIT 2
Basic types of digital carrier modulation
ASK
FSK
PSK
???
Bálint TÓTH – BME TMIT 3
a)
b)
c)
d)
t
t
t
t
0 T 2T 3T 4T 5T
1 0 1 1 0
FSK: Frequency Shift Keying
More noise-
roboust than
ASK.
Example:
High-frequency
radio.
Bálint TÓTH – BME TMIT 6
Spectral Power Density Function of the Binary FSK Signal
Bálint TÓTH – BME TMIT 7
f
fc
fc
fc
fc
fc
fc
fc
- - - + + +1/T 1/T0.5/T 0.5/T1.5/T 1.5/T
G (f)s
f = 0.25/T
f = 0.75/T
f = 0.35/T
d
d
d
f =d
d
f = cc
QAM: Quadrature Amplitude Modulation
Modulating the amplitude of two signals with
different phases.
Block diagramm.
Constellation diagram.
Variants:
– 4-QAM
– 8-QAM
– 16-QAM
– …
– 4096-QAM
Bálint TÓTH – BME TMIT 8