Q7Satellite Communication
Question
Q.7. What is the importance of LNA in satellite link design?
Answer
The Low Noise Amplifier (LNA) is the first active stage in an earth station receiver and is critical because it dominantly determines the overall system noise temperature (per Friis' formula), directly setting the achievable link's carrier-to-noise ratio and hence the smallest usable satellite signal that can be reliably received.
The Low Noise Amplifier (LNA) is the first active amplification stage in a satellite earth station's receive chain, positioned immediately after the antenna feed, and its noise performance is critically important because, per the Friis noise formula for cascaded stages, the noise contribution of the first stage dominates the overall system noise temperature (subsequent stages' noise contributions are progressively divided down by the gain of all preceding stages). A low-noise-temperature LNA therefore directly minimizes the overall receive system noise temperature, which in turn maximizes the achievable carrier-to-noise ratio (C/N) for a given received satellite signal power — since satellite downlink signals arrive at the earth station extremely weak (having traveled tens of thousands of kilometers and having limited satellite transmit power), a high-quality, low-noise LNA is essential to reliably recover usable signal from an otherwise very low signal-to-noise link budget.