Which set lists components of a typical space RF link budget and how they interact to determine link margin?

• A. Modulation type, coding rate, power supply voltage, and manufacturing date
• B. Transmit power, receiver bandwidth, satellite color, weather forecast
• C. Transmit power, transmitter antenna gain, receive antenna gain, free-space path loss, system losses, polarization mismatch, receiver noise figure and temperature, and required Eb/N0 to meet BER
• D. Frequency, modulation type, antenna size, operator mood

Answer: (C)

A space RF link budget is about balancing the energy that leaves the transmitter with what the receiver can reliably recover in the presence of noise. The amount of energy reaching the receiver is determined by the transmitter power and the gains of both antennas, while losses along the path and in the hardware reduce that energy. Specifically, higher transmit power and higher transmitter and receiver antenna gains push the link in the right direction, while free-space path loss, additional system losses, and any polarization mismatch reduce it. At the receiver, the signal must contend with noise described by the receiver’s noise figure and temperature, which set the noise floor. To know if the link will meet the desired quality, you compare the energy per bit you can extract from the signal, Eb, to the noise energy per bit, Eb/N0, and you have a target Eb/N0 required to achieve a given BER for the chosen modulation and coding. The link margin is simply the excess Eb/N0 you have above that requirement. All of these factors together form a typical space RF link budget, including transmit power, antenna gains, free-space path loss, system losses, polarization mismatch, receiver noise figure and temperature, and the required Eb/N0 to meet BER. The other options mix in irrelevant or non-physical factors (like color, weather, or mood) or omit the essential loss and noise terms needed to assess link performance.