1. Digital Modulation Technique
Presented By:
Amit Degada.
Teaching Assistant,
SV NIT, Surat.

2. Goal of Today’s Lecture
Differential Phase Shift keying
Quadrature Phase Shift Keying
Minimum Phase Shift Keying
Introduction To Information Theory
Information Measure

3. Differential Phase Shift Keying (DPSK)
Why We Require?
To Have Non-coherent Detection
That Makes Receiver Design
How can we do?
0 may be used represent transition
1 indicate No Transition

4. DPSK Transmitter
What Should We Do to make Encoder?

5. DPSK Transmitter…………Modified

6. Differentially Encoded Sequence
Binary Data
Differentially Encoded Data
Phase of DPSK
π π π
Shifted Differentially encoded Data dk-1
Phase of shifted Data
π π π
Phase Comparision Output
Detected Binary Seq.

7. DPSK Receiver

8. Goal of Today’s Lecture
Differential Phase Shift keying
Quadrature Phase Shift Keying
Minimum Phase Shift Keying
Introduction To Information Theory
Information Measure

9. Quadrature Phase Shift Keying (QPSK)
Extension of Binary-PSK
Spectrum Efficient Technique
In M-ary Transmission it is Possible to Transmit M Possible Signal
M = 2n
where,
n= no of Bits that we Combine
signaling Interval T= nTb
In QPSK n=2 === > So M =4
and
signaling Interval T= 2Tb

10. Quadrature Phase Shift Keying (QPSK)
M=4 so we have possible signal are 00,01,10,11
Or In Natural Coded Form 00,10,11,01
-135
-45 45
135
Binary Dibit 00
Binary Dibit 10
Binary Dibit 11
Binary Dibit 01

11. QPSK Waveform

12. QPSK Signal Phase

13. Constellation Diagram

14. Quadrature Phase Shift Keying (QPSK)
The QPSK Formula
………………(1)
Where, ϕ(t)=135,45,-45,-135
Simplifying Equation 1
This Gives the Idea about Transmitter design

15. QPSK Transmitter

16. QPSK Receiver

17. Synchronization Circuit

18. Goal of Today’s Lecture
Differential Phase Shift keying
Quadrature Phase Shift Keying
Minimum Phase Shift Keying
Introduction To Information Theory
Information Measure

19. Minimum Shift Keying (MSK)
In Binary FSK the Phase Continuity is maintained at the transition Point. This type of Modulated wave is referred as Continuous Phase Frequency Shift Keying (CPFSK)
In MSK there is phase change equals to one half Bit Rate when the bit Changes 0 to 1 and 1 to 0.

20. Minimum Shift Keying (MSK)
Let’s take fc1 and fc2 represents binary 1 and 0 Respectively
Similarly
Where

21. Minimum Shift Keying (MSK)
The MSK Equation
where
For Symbol 0
For Symbol 1

22. Carrier Phase Coding
For dibit 00

23. Carrier Phase Coding
For dibit 10

24. Carrier Phase Coding
For dibit 11

25. Carrier Phase Coding
For dibit 01

26. Goal of Today’s Lecture
Differential Phase Shift keying
Quadrature Phase Shift Keying
Minimum Phase Shift Keying
Introduction To Information Theory
Information Measure

27. Information Theory
It is a study of Communication Engineering plus Maths
A Communication Engineer has to Fight with
Limited Power
Inevitable Background Noise
Limited Bandwidth

28. Information Theory deals with
The Measure of Source Information
The Information Capacity of the channel
Coding
If The rate of Information from a source does not exceed the capacity of the Channel, then there exist a Coding Scheme such that Information can be transmitted over the Communication Channel with arbitrary small amount of errors despite the presence of Noise

29. Goal of Today’s Lecture
Differential Phase Shift keying
Quadrature Phase Shift Keying
Minimum Phase Shift Keying
Introduction To Information Theory
Information Measure

30. Information Measure
This is utilized to determine the information rate of discrete Sources
Consider Two Messages
A Dog bites a man
A man bites a dog

31. Thank You