Question
Which of the following is characteristic of an inverting linear transponder?
Answer Options
- A) Doppler shift is reduced because the uplink and downlink shifts are in opposite directions
- B) Signal position in the band is reversed
- C) Upper sideband on the uplink becomes lower sideband on the downlink, and vice versa
- D) All these choices are correct
Correct Answer: D
Explanation
An inverting linear transponder is a type of satellite repeater that reverses the frequency relationship of signals it receives. This reversal is achieved through the mixing process used inside the satellite’s transponder. This configuration has several distinct effects on the signals received on Earth after being retransmitted by the satellite.
The characteristics include: signal position in the band is reversed (e.g., a signal appearing at the low end of the uplink spectrum appears at the high end of the downlink spectrum); Upper Sideband (USB) signals on the uplink become Lower Sideband (LSB) signals on the downlink, and vice versa; and importantly, the Doppler frequency shift is partially compensated. Since the uplink signal is shifted high and the downlink signal is shifted low (or vice versa, due to the satellite’s movement), the frequency reversal causes the two shifts to partially cancel each other, which simplifies tracking and tuning for ground stations.
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