# Glossary of Satellite Terms: Satellite Link Budget

A satellite link budget is a crucial component in the design and analysis of satellite communication systems. It is a comprehensive calculation that takes into account various factors to determine the overall performance and feasibility of a satellite link. Understanding the concept of a satellite link budget is essential for engineers and professionals working in the field of satellite communications.

In simple terms, a satellite link budget is a mathematical model that calculates the power budget of a satellite communication link. It considers the power transmitted by the satellite, the power received at the ground station, and all the losses and gains in between. The goal is to ensure that the received power is sufficient for reliable communication.

The link budget calculation starts with the transmitter power, which is the power generated by the satellite’s communication system. This power is then transmitted through the satellite’s antenna, which has a certain gain. The gain of the antenna determines how much power is radiated in the desired direction and how much is lost in other directions.

Once the power is transmitted, it travels through space and encounters various losses. These losses include free space loss, which is the loss of power due to the spreading of the signal over distance, and atmospheric losses, which occur due to absorption and scattering of the signal by the Earth’s atmosphere.

After traveling through space, the signal reaches the receiving antenna at the ground station. The receiving antenna also has a gain, which determines how much power is captured and directed towards the receiver. The captured power is then amplified by the receiver’s system, which has its own noise figure. The noise figure represents the amount of noise added to the received signal during the amplification process.

The received power, after all the losses and gains, is then compared to the minimum required power for reliable communication. This minimum required power is determined by the modulation scheme and the desired bit error rate. If the received power is higher than the minimum required power, the link is considered to be feasible. However, if the received power is lower, additional measures such as increasing the transmitter power or using a larger antenna may be required.

The satellite link budget also takes into account other factors such as rain attenuation, which is the loss of power due to rain droplets in the signal path, and interference from other satellites or terrestrial sources. These factors can significantly affect the performance of the satellite link and must be considered in the link budget calculation.

In conclusion, a satellite link budget is a vital tool in the design and analysis of satellite communication systems. It calculates the power budget of a satellite link, taking into account various factors such as transmitter power, antenna gains, losses in space and atmosphere, and receiver performance. By ensuring that the received power is sufficient for reliable communication, the link budget helps engineers and professionals in the field of satellite communications design and optimize satellite communication systems.