1. Sistem Telekomunikasi, Sukiswo, ST, MT Sukiswo sukiswok@yahoo.com
Digital Modulation
Sukiswo
Sistem Telekomunikasi, Sukiswo, ST, MT

2. Sistem Telekomunikasi, Sukiswo, ST, MT
Outline
Digital modulation and digital radio
Information Capacity
bit, bitrate, baud and minimum bandwidth
M-ary encoding
ASK, FSK, PSK, QPSK and DPSK
Sistem Telekomunikasi, Sukiswo, ST, MT

3. Analog – Digital Communication
Analog Communications :Transport of analog information: i.e. base-band analog modulated CW carrier or pulse modulation
Digital Communications Transport of digital information: i.e. digital modulated CW carrier or pulse-code modulation
Sistem Telekomunikasi, Sukiswo, ST, MT

4. Sistem Telekomunikasi, Sukiswo, ST, MT
Modulation Principle
Change parameters of a carrier
Information signal: Ac(t)
fc(t)
(t)
Ac(t) : amplitude modulation AM ASK
fc(t) : frequency modulation FM FSK
(t) : phase modulation PM PSK
Ac(t) and (t)  QAM (Digital)
Analog
Digital
Sistem Telekomunikasi, Sukiswo, ST, MT

5. Block diagram of a digital radio system
Sistem Telekomunikasi, Sukiswo, ST, MT

6. Sistem Telekomunikasi, Sukiswo, ST, MT
Bandwidth and information capacity
Hartleys law 1920
I = information capacity
B = system bandwidth (Hertz)
t = transmission time (seconds)
Sistem Telekomunikasi, Sukiswo, ST, MT

7. Sistem Telekomunikasi, Sukiswo, ST, MT
Bandwidth and information capacity
Shannon limit for information capacity
I = information capacity (bit/second)
B = system bandwidth (Hertz)
S/N = signal-to-noise power ratio (unitless)
Sistem Telekomunikasi, Sukiswo, ST, MT

8. Sistem Telekomunikasi, Sukiswo, ST, MT
M-ary Encoding
N = number of bits necessary
M = number of conditions, levels, or combinations possible with N bits
Sistem Telekomunikasi, Sukiswo, ST, MT

9. Sistem Telekomunikasi, Sukiswo, ST, MT
Baud and Minimum Bandwidth
baud = symbol rate (baud per second)
ts = time of one signaling element (second)
symbol = one signaling element
What is the difference between baud and bits per second (bps)
Sistem Telekomunikasi, Sukiswo, ST, MT

10. Sistem Telekomunikasi, Sukiswo, ST, MT
Baud and Minimum Bandwidth
fb = channel capacity (bps)
B = minimum Nyquist bandwidth (hertz)
M = number of discrete signals or voltage levels
N = number of bits encoded into each sysmbol 2
Sistem Telekomunikasi, Sukiswo, ST, MT

11. Sistem Telekomunikasi, Sukiswo, ST, MT
Binary data sequence signaling t 1
On-off
Polar
Return-to-zero
Bipolar Tb A
Sistem Telekomunikasi, Sukiswo, ST, MT

12. Sistem Telekomunikasi, Sukiswo, ST, MT
Polar signal spectrum
1/T
2/T
3/T
-3/T
-2/T
-1/T
Sistem Telekomunikasi, Sukiswo, ST, MT

13. Amplitude Shift Keying (ASK)
vASK(t) = amplitude-shift keying wave
vm(t) = digital information (modulating) signal (+1 or -1 volt)
A/ = unmodulated carrier amplitude (volt)
c = analog carrier radian frequency (rad/sec)
ASK is sometimes referred as OOK (on-off-keying)
Sistem Telekomunikasi, Sukiswo, ST, MT

14. Amplitude-shift keying (ASK or OOK)1 Tb
unmodulated carrier
modulated carrier
Sistem Telekomunikasi, Sukiswo, ST, MT

15. Amplitude-shift keying spectrum
Sistem Telekomunikasi, Sukiswo, ST, MT

16. Sistem Telekomunikasi, Sukiswo, ST, MT
ASK Transmitter X
Binary
Data sequence in
Unipolar form
Accos(2fct)
Binary ASK
signal t
Sistem Telekomunikasi, Sukiswo, ST, MT

17. Sistem Telekomunikasi, Sukiswo, ST, MT
Coherent ASK Receiver X
Accos(2fct)
Binary ASK
wave
(amplitude A0)
Decision
device
Threshold = ¼ AcA0Tb
Choose 1 if > ¼ AcA0Tb
Choose 0 if < ¼ AcA0Tb
Sistem Telekomunikasi, Sukiswo, ST, MT

18. Different OOK ReceiversX
Accos(2fct)
Decision
device
()2
Coherent correlation receiver
Quasi coherent square law receiver
Filter tuned to fc
Envelope detector
Incoherent envelope receiver
Sistem Telekomunikasi, Sukiswo, ST, MT

19. Frequency-shift keying (FSK)
vFSK(t) = frequency-shift keying wave
vm(t) = digital information (modulating) signal (+1 or -1 volt)
Vc = carrier amplitude (volt)
fc = analog carrier frequency (hertz)
f = change (shift) in the carrier frequency (Hz)
Sistem Telekomunikasi, Sukiswo, ST, MT

20. Frequency-shift keying (FSK)1 Tb
Accos(2fc1t)
Accos(2fc2t) t
Sistem Telekomunikasi, Sukiswo, ST, MT

21. Frequency-shift keying spectrum
Sistem Telekomunikasi, Sukiswo, ST, MT

22. Binary FSK TransmitterX 
FSK
wave
Unipolar
Binary Data
sequence
Accos(2fc1t) +
Accos(2fc2t)
Inverter t
Sistem Telekomunikasi, Sukiswo, ST, MT

23. Coherent BFSK ReceiverX
Accos(2fc1t)
Binary FSK
wave
Decision
device
Threshold = 0
Accos(2fc2t)  - +
Choose 1 if > 0
Choose 0 if < 0
Sistem Telekomunikasi, Sukiswo, ST, MT

24. Noncoherent BFSK Receiver
Binary FSK
wave
Comparison
device
Choose 1 if S1>S2
Choose 0 if S1<S2
BPF
tuned to
fc1
fc2
Envelope detector
Sample at time t = kTb S1 S2
Sistem Telekomunikasi, Sukiswo, ST, MT

25. Binary Phase-Shift Keying BPSK1 Tb
Accos(2fct)
-Accos(2fct)
Sistem Telekomunikasi, Sukiswo, ST, MT

26. Sistem Telekomunikasi, Sukiswo, ST, MT
BPSK spectrum
Sistem Telekomunikasi, Sukiswo, ST, MT

27. Binary PSK TransmitterX
Binary
Data sequence in
polar form
Accos(2fct)
BinaryPSK
signal t
Sistem Telekomunikasi, Sukiswo, ST, MT

28. Coherent binary PSK ReceiverX
Accos(2fct)
Binary PSK
wave
Decision
device
Threshold = 0
Choose 1 if > 0
Choose 0 if < 0
Sistem Telekomunikasi, Sukiswo, ST, MT

29. Quadriphase-shift keying (QPSK)01 t 00 t 10 t 11 t t 1 1 1 1
Sistem Telekomunikasi, Sukiswo, ST, MT

30. Sistem Telekomunikasi, Sukiswo, ST, MT
QPSK spectrum
Sistem Telekomunikasi, Sukiswo, ST, MT

31. QPSK Transmitter Q=Quatenary=Quadrature Series to parallel converter
-90º X
Oscillator 
QPSK
signal
Acsin(2fct)
Binary
bipolar
data sequence
Accos(2fct) - +
Sistem Telekomunikasi, Sukiswo, ST, MT

32. Sistem Telekomunikasi, Sukiswo, ST, MT
QPSK Transmitter
Sistem Telekomunikasi, Sukiswo, ST, MT

33. Sistem Telekomunikasi, Sukiswo, ST, MT
QPSK Transmitter
Sistem Telekomunikasi, Sukiswo, ST, MT

34. Sistem Telekomunikasi, Sukiswo, ST, MT
QPSK Transmitter
Sistem Telekomunikasi, Sukiswo, ST, MT

35. Sistem Telekomunikasi, Sukiswo, ST, MT
QPSK Transmitter
Sistem Telekomunikasi, Sukiswo, ST, MT

36. Sistem Telekomunikasi, Sukiswo, ST, MT
QPSK Transmitter
Sistem Telekomunikasi, Sukiswo, ST, MT

37. Sistem Telekomunikasi, Sukiswo, ST, MT
QPSK Transmitter
Diagram Konstelasi 10 11 01 00
Sistem Telekomunikasi, Sukiswo, ST, MT

38. Sistem Telekomunikasi, Sukiswo, ST, MT
Tugas
Tugas : Buat modulasi QPSK dan penjabarannya dengan carrier Ac Sin 2fct
Sistem Telekomunikasi, Sukiswo, ST, MT

39. Sistem Telekomunikasi, Sukiswo, ST, MT
QPSK Transmitter
Sistem Telekomunikasi, Sukiswo, ST, MT

40. Coherent QPSK ReceiverX
Accos(2fct)
QPSK
wave
Decision
device
Threshold = 0
Parallel to series converter
-90º
Binary Data
sequence
Sistem Telekomunikasi, Sukiswo, ST, MT

41. Sistem Telekomunikasi, Sukiswo, ST, MT
QPSK Receiver
Sistem Telekomunikasi, Sukiswo, ST, MT

42. Sistem Telekomunikasi, Sukiswo, ST, MT
QPSK Receiver
Sistem Telekomunikasi, Sukiswo, ST, MT

43. Sistem Telekomunikasi, Sukiswo, ST, MT
QPSK Receiver
Sistem Telekomunikasi, Sukiswo, ST, MT

44. Sistem Telekomunikasi, Sukiswo, ST, MT
QPSK Receiver
Sistem Telekomunikasi, Sukiswo, ST, MT

45. Sistem Telekomunikasi, Sukiswo, ST, MT
QPSK Receiver
Sistem Telekomunikasi, Sukiswo, ST, MT

46. Sistem Telekomunikasi, Sukiswo, ST, MT
QPSK Receiver
Sistem Telekomunikasi, Sukiswo, ST, MT

47. Sistem Telekomunikasi, Sukiswo, ST, MT
QPSK Receiver
Sistem Telekomunikasi, Sukiswo, ST, MT

48. Sistem Telekomunikasi, Sukiswo, ST, MT
QPSK Receiver
Sistem Telekomunikasi, Sukiswo, ST, MT

49. Sistem Telekomunikasi, Sukiswo, ST, MT
Tugas
Tugas : Buat Demodulasi QPSK dan penjabarannya dengan carrier Ac Sin 2fct
Sistem Telekomunikasi, Sukiswo, ST, MT

50. Differential Binary PSK TransmitterX
Binary
data
Accos(2fct)
DBPSK
wave
One-bit delay
Level shift
Encoded data
XNOR
Delayed Encoded data
Sistem Telekomunikasi, Sukiswo, ST, MT

51. Differential Binary PSK Transmitter
(Binary data) XNOR (Delayed Encoded data) = Encoded data
Binary data 1
Delayed Encoded data
Encoded data
Transmitted phase 
Transmitted level -1
Detected bit
Sistem Telekomunikasi, Sukiswo, ST, MT

52. Sistem Telekomunikasi, Sukiswo, ST, MT
Non-coherent Differential Binary PSK Receiver
Delay Tb X
DBPSK
wave
Decision
device
Choose 1 if > 0
Choose 0 if < 0
Threshold = 0
Sistem Telekomunikasi, Sukiswo, ST, MT