Communications I Dr. Mohammed Hawa Introduction to Digital - FET

Polar NRZ CodePolar RZ CodeIn addition, the rms value of polar signals is bigger than unipolar signals, whichmeans that polar signals have more power than unipolar signals 9 , and hence havebetter SNR at the receiver. Actually, polar NRZ signals have more power comparedto polar RZ signals.The drawback of polar NRZ, however, is that it lacks clock information especiallywhen a long sequence of 0‟s or 1‟s is transmitted. This problem does not exist inpolar RZ signals, since the signal drops to zero in the middle of each pulse period.The power spectral densities (PSD) of both polar NRZ and polar RZ are shownbelow.S m (w)Polar NRZPolar RZ-8pf 0 -4pf 0 -2pf 0 0 2pf 0 4pf 0 6pf 0 8pf 0w-6pf 0f-4f 0 -3f 0 -2f 0 -f 0 0 f 0 2f 0 3f 0 4f 0Signals transmitted on a computer motherboard often use Polar NRZ code. Anotheruseful application of this encoding is in Fiber-based Gigabit Ethernet (1000BASE-SXand 1000BASE-LX).9 2Remember that the average power in a signal is the square of its rms value (P x = x rms ).10