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Polar NRZ-L, NRZ-I, RZ schemes

Polar NRZ-L, NRZ-I, RZ schemes. The voltages are on the both sides of the time axis NRZ-L (Non Return to Zero-Level): The level of the voltage determines the value of the bit NRZ-I (Non Return to Zero-Invert): If the bit is 0 there is no change; if the bit is 1 there is a change

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Polar NRZ-L, NRZ-I, RZ schemes

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  1. Polar NRZ-L, NRZ-I, RZ schemes The voltages are on the both sides of the time axis NRZ-L (Non Return to Zero-Level): The level of the voltage determines the value of the bit NRZ-I (Non Return to Zero-Invert): If the bit is 0 there is no change; if the bit is 1 there is a change RZ (Return to Zero): The signal changes during the bit

  2. Figure 4.6 Polar NRZ-L and NRZ-I schemes

  3. Figure 4.7 Polar RZ scheme

  4. Note In NRZ-L the level of the voltage determines the value of the bit. In NRZ-I the inversion or the lack of inversion determines the value of the bit.

  5. Note NRZ-L and NRZ-I both have an average signal rate of N/2 Bd.

  6. Note NRZ-L and NRZ-I both have a DC component problem.

  7. Example 4.4 A system is using NRZ-I to transfer 10-Mbps data. What are the average signal rate and minimum bandwidth? Solution The average signal rate is S = N/2 = 500 kbaud. The minimum bandwidth for this average baud rate is Bmin = S = 500 kHz.

  8. Polar Biphase schemes: Manchester and Differential Manchester Manchester: RZ + NRZ-L Differential Manchester: RZ + NRZ-I

  9. Figure 4.8 Polar biphase: Manchester and differential Manchester schemes

  10. Note In Manchester and differential Manchester encoding, the transition at the middle of the bit is used for synchronization.

  11. Note The minimum bandwidth of Manchester and differential Manchester is 2 times that of NRZ.

  12. Note In bipolar encoding, we use three levels: positive, zero, and negative.

  13. Bipolar schemes: AMI and pseudoternary In Bipolar encoding ( multilevel binary) there are three voltage levels: +ve, -ve, and 0 AMI (Alternate Mark Inversion): AMI means alternate 1 inversion. Zero voltage represents 0. Pseudoternary: The 1 bit is encoded as a zero voltage and the 0 bit is encoded as alternating positive and negative voltages

  14. Figure 4.9 Bipolar schemes: AMI and pseudoternary

  15. Note Multilevel Schemes: In mBnL schemes, a pattern of m data elements is encoded as a pattern of n signal elements in which 2m ≤ Ln.

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