# 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.

Following are the links to other useful measurements available on Test and Measurement World website.
Difference between EVM vs subcarriers and EVM vs symbols
Current measurement vs Voltage measurement
Inductance measurement vs Capacitance measurement
Difference between Power and Energy measurements
EMC measurement vs EMI measurement
Electric and Magnetic Field Measurements