line coding (unipolar, polar)

1. Line Coding
By
Md. Fazle Rabbi
16CSE057

2. 4.2
 What is LINE CODING
• The process of converting digital data to digital signals.

3. 4.3
 Types of line Coding

4. 4.4
 Topics discussed in this section

5. 4.5

6. 4.6
Unipolar

7. 4.7
Unipolar

8. 4.8
Unipolar
• Traditional NRZ scheme
bit 1  positive voltage
bit 0  zero voltage

9. 4.9
Example

10. 4.10
Figure 1 Unipolar NRZ scheme

11. 4.11
Advantages Disadvantages
Unipolar

12. 4.12

13. 4.13
Polar
• The voltages are on both sides of the time axis.

14. 4.14
Polar NRZ
• There are two versions:
• NRZ - Level (NRZ-L)
• NRZ - Inversion (NRZ-I)

15. 4.15
Polar NRZ-L
bit 1  negative voltage
bit 0  positive voltage

16. 4.16
Example

17. 4.17
Figure 2 Polar NRZ-L schemes

18. 4.18
Polar NRZ-I
bit 1  change
bit 0  no change

19. 4.19
Example

20. 4.20
Figure 3 Polar NRZ-I schemes

21. 4.21
Comparing NRZ-L and NRZ-I
• NRZ-L and NRZ-I both have a DC component problem and baseline
wandering, it is worse for NRZ-L.
• Both have no self synchronization & no error detection.
• Both are relatively simple to implement

22. 4.22
Polar - RZ

23. 4.23
Polar - RZ

24. 4.24
Polar - RZ
uses three voltage levels: +v, 0, -v
bit 1  starts at +V
bit 0  starts at -V

25. 4.25
Example

26. 4.26
Figure 4 Polar RZ scheme

27. 4.27
Advantages Disadvantages
Polar

28. 4.28
Polar - Biphase

29. 4.29
Polar - Biphase:
• Manchester
coding consists of combining the NRZ-L and
RZ schemes.
• Differential Manchester
coding consists of combining the NRZ-I and
RZ schemes.

30. 4.30
Manchester
Bit 1  starts at –V and moves +V in the
middle of bit interval.
Bit 0  starts at +V and moves -V in the
middle of bit interval.
coding consists of combining the NRZ-L and RZ schemes.

31. 4.31
Example

32. 4.32
Figure 5 Polar biphase: Manchester schemes

33. 4.33
Differential Manchester
Bit 1  no transition
Bit 0  transition
Always has a transition of middle of each bit period
Transition or no transition.
coding consists of combining the NRZ-I and RZ schemes.

34. 4.34
Example

35. 4.35
Figure 5 Polar biphase: differential Manchester schemes

36. 4.36
Thank you