Receiver noise power
NPOWER = noisepow(NBW,NF,REFTEMP)
returns
the noise power, NPOWER
= noisepow(NBW
,NF
,REFTEMP
)NPOWER
, in watts for a receiver.
This receiver has a noise bandwidth NBW
in hertz,
noise figure NF
in decibels, and reference temperature REFTEMP
in
degrees kelvin.

The noise bandwidth of the receiver in hertz. For a superheterodyne receiver, the noise bandwidth is approximately equal to the bandwidth of the intermediate frequency stages [1]. 

Noise figure. The noise figure is a dimensionless quantity that indicates how much a receiver deviates from an ideal receiver in terms of internal noise. An ideal receiver only produces the expected thermal noise power for a given noise bandwidth and temperature. A noise figure of 1 indicates that the noise power of a receiver equals the noise power of an ideal receiver. Because an actual receiver cannot exhibit a noise power value less than an ideal receiver, the noise figure is always greater than or equal to one. 

Reference temperature in degrees kelvin. The temperature of the receiver. Typical values range from 290–300 degrees kelvin. 

Noise power in watts. The internal noise power contribution of the receiver to the signaltonoise ratio. 
Calculate the noise power of a receiver whose noise bandwidth is 10 kHz, noise figure is 1 dB, and reference temperature is 300 K.
npower = noisepow(10e3,1,300);
[1] Skolnik, M. Introduction to Radar Systems. New York: McGrawHill, 1980.