2. line coding (unipolar, polar)

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  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