A satellite in the geostationary orbit of the earth (36000 km above the earth) broadcasts a few watts of microwave signal over a wide footprint area the broadcast signal gets attenuated by approximately 200 dB and becomes very weak at the stationary reception centers on the earth. This weak signal has to amplified by means of sophisticated electronics for healthy signal reproduction. It is important to ensure that the amplifications do not contribute any significant amount of noise amplification; otherwise it degrades the signal of interest. Low Noise Amplifier (LNA) and Low Noise Block Converter (LNBC) are used for amplification and reproduction of weak signals.
Contrary to this, in terrestrial wireless communication, both the transmitter and receiver are mobile. The base station used in terrestrial mobile communication broadcasts signal in all directions simultaneously. This transmitted signal has high power. The signal transmitted is so powerful that it has capability of suturing ‘C’ band satellite receiving systems. That is, Low Noise Amplifier (LNA) and Low Noise Block Converter (LNBC) are saturated by high power signals (having same frequency). The probability of saturation of LNA and LNBC is nearly 100% due to their inherent characteristics. Saturation of receiving system will lead to total collapse of the ‘C’ band satellite network services.
Source: Science Reporter, January 2009 issue.
