Noise spectral density

In communications, noise spectral density, noise power density, or simply noise density (N₀) is the power spectral density of noise or the noise power per unit of bandwidth. It has dimension of power over frequency, whose SI unit is watts per hertz (equivalent to watt-seconds). It is commonly used in link budgets as the denominator of the important figure-of-merit ratios, such as carrier-to-noise-density ratio as well as E_b/N₀ and E_s/N₀.

If the noise is one-sided white noise, i.e., constant with frequency, then the total noise power N integrated over a bandwidth B is N=BN₀ (for double-sided white noise, this is doubled, so N is BN₀/2). This is utilized in signal-to-noise ratio calculations.

For thermal noise, its spectral density is given by N₀ = kT, where k is Boltzmann's constant in joules per kelvin, and T is the receiver system noise temperature in kelvin.

References

Jerry C. Whitaker (27 April 2005). The Electronics Handbook, Second Edition. CRC Press. p. 636. ISBN 978-1-4200-3666-4.

Noise (physics and telecommunications)

General	Acoustic quieting Distortion Noise cancellation Noise control Noise measurement Noise power Noise reduction Noise temperature Phase distortion

Noise in...	Audio Buildings Electronics Environment Government regulation Human health Images Radio Rooms Ships Sound masking Transportation Video

Class of noise	Additive white Gaussian noise (AWGN) Atmospheric noise Background noise Brownian noise Burst noise Cosmic noise Flicker noise Gaussian noise Grey noise Jitter Johnson–Nyquist noise (thermal noise) Pink noise Quantization error (or q. noise) Shot noise White noise Coherent noise Value noise Gradient noise Worley noise

Engineering terms	Channel noise level Circuit noise level Effective input noise temperature Equivalent noise resistance Equivalent pulse code modulation noise Impulse noise (audio) Noise figure Noise floor Noise shaping Noise spectral density Noise, vibration, and harshness (NVH) Phase noise Pseudorandom noise Statistical noise

Ratios	Carrier-to-noise ratio (C/N) Carrier-to-receiver noise density (C/kT) dBrnC E_b/N₀ (energy per bit to noise density) E_s/N₀ (energy per symbol to noise density) Modulation error ratio (MER) Signal, noise and distortion (SINAD) Signal-to-interference ratio (S/I) Signal-to-noise ratio (S/N, SNR) Signal-to-noise ratio (imaging) Signal to noise plus interference (SNIR) Signal-to-quantization-noise ratio (SQNR)

Related topics	List of noise topics Acoustics Colors of noise Interference (communication) Noise generator Radio noise source Spectrum analyzer Thermal radiation

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Noise spectral density

See also

References