Characteristics and Frequency considerations:
number of factors resulting from changes in the atmosphere have to be taken
into account when designing a satellite communications system in order to avoid
impairment of the wanted signal.
a margin in the required carrier-to-noise ratio is incorporated to accommodate
2. Radio Noise
noise emitted by matter is used as a source of information in radioastronomy and
in remote sensing. Noise of a thermal origin has a continuous spectrum, but
several other radiation mechanisms cause the emission to have a spectral-line
structure. Atoms and molecules are distinguished by their different spectral
other services such as satellite communications noise is a limiting factor for
the receiving system; generally, it is inappropriate to use receiving systems
with noise temperatures which are much less than those specified by the minimum
about 30 MHz to about 1 GHz cosmic noise predominates over atmospheric noise
except during local thunderstorms, but will generally be exceeded by man-made
noise in populated areas.
the bands of strong gaseous absorption, the noise temperature reaches maximum values
of some 290 K. At times, precipitation will also increase the noise temperature
at frequencies above 5 GHz.
6.1 gives an indication of sky noise at various elevation angles and