# Test and Measurement World

## Test and Measurement World Terminology Section

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## Noise Spectral Density(N0),Carrier to Noise Spectral Density Ratio(C/N0)

This page describes Noise Spectral Density(N0) vs Carrier to Noise Spectral Density Ratio(C/N0). It mentions basic difference between N0 (Noise Spectral Density) and C/N0(Carrier to Noise Spectral Density Ratio).

### Noise Spectral Density( N0 ) • It is defined as amount of (white) noise energy per bandwidth unit (Hz).
➤ N0 = N/B
• It can also be expressed as follows.
➤ N0 = K*T
Where,
K = Boltzmann's constant in J/K
T = Receiver system noise temperature in K
• Units of No are Joules (J) or Watts/Hz or Watts*s.

### Carrier to Noise Spectral Density Ratio( C/N0 ) • It is the ratio of power level to noise power spectral density (i.e. normalized noise level relative to 1 Hz) in a system.
• C/N0 is similar to C/N but it does not factor the actual noise bandwidth.
• It simplifies analysis of systems where variation of (utilized) BW may apply.
• Both C/N ratio and C/N0 are determined using BER plots or BER meters.