link budget of satellite communication?

How to calculate the carrier to interference ratio (C / I) in link budget of satellite communication?

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  • Where in the chain do you wish to know ? - the levels vary as the signal progresses through the RX.

    Noise and interference are two different things, and need to be calculated separately.- an out of band interferer is (hopefully) not amplified as much as the wanted signals, assuming the designer has their filtering strategy correct. Noise (in band) once accompanying the signal cannot be removed. In a well-designed system the RX noise level is set by the front end devices, as after that the signal level is high enough that the noise of successive stages has only a small additional effect.

    The other part is the link budget of course is the level of  the wanted signal. How much is transmitted and what (very small) fraction of that is intercepted by the RX antenna..

    Satellite links are one of the few cases when an unobstructed path can be assumed and the inverse square law actually applies - so you need the altitude and the TX power.

    Antena 'gain', or more accurately "directivity" can be converted to an equivalent capture area.
    Mike.

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  • Where in the chain do you wish to know ? - the levels vary as the signal progresses through the RX.

    Noise and interference are two different things, and need to be calculated separately.- an out of band interferer is (hopefully) not amplified as much as the wanted signals, assuming the designer has their filtering strategy correct. Noise (in band) once accompanying the signal cannot be removed. In a well-designed system the RX noise level is set by the front end devices, as after that the signal level is high enough that the noise of successive stages has only a small additional effect.

    The other part is the link budget of course is the level of  the wanted signal. How much is transmitted and what (very small) fraction of that is intercepted by the RX antenna..

    Satellite links are one of the few cases when an unobstructed path can be assumed and the inverse square law actually applies - so you need the altitude and the TX power.

    Antena 'gain', or more accurately "directivity" can be converted to an equivalent capture area.
    Mike.

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