This document discusses different types of line coding used to convert digital data to digital signals for transmission. It describes unipolar coding, which uses a single voltage level, and polar coding, which uses both positive and negative voltages. Polar coding includes NRZ-L, NRZ-I, RZ, Manchester, and differential Manchester schemes. Manchester coding combines NRZ-L and RZ, using positive-to-negative or negative-to-positive transitions to indicate bits. Differential Manchester combines NRZ-I and RZ, using transitions to indicate 1s and no transition to indicate 0s. The document provides examples and diagrams of each type of coding.

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