In satellite communication, what is the primary function of a transponder?
Electronics and Communication Engineering
Satellite Communication
Difficulty: Easy
Choose an option
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AReceives a signal from the Earth station and amplifies it
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BChanges the frequency of the received signal
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CRetransmits the received signal
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DPerforms all of the above-mentioned functions
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EOnly amplifies and retransmits without frequency conversion
Answer
Correct Answer: Performs all of the above-mentioned functions
Explanation
Introduction / Context:A transponder is the key electronic subsystem onboard a communication satellite. It acts as a repeater in space, enabling signals from Earth stations to be amplified, frequency shifted, and retransmitted to wide areas on Earth.
Given Data / Assumptions:
- Signal received from Earth = uplink frequency.
- Transponder = receiver + frequency converter + amplifier + transmitter.
- Output = downlink frequency to avoid interference.
Concept / Approach:The transponder ensures that signals transmitted by an Earth station are not only repeated but also shifted in frequency to prevent interference between uplink and downlink signals.
Step-by-Step Solution:
Step 1: Receive uplink signal at high frequency (e.g., 6 GHz).Step 2: Convert frequency down (e.g., 4 GHz downlink).Step 3: Amplify the signal to compensate for path losses.Step 4: Retransmit the signal towards designated Earth coverage area.Verification / Alternative check:
All textbooks define transponder as "receiver, frequency converter, and transmitter" combined.Why Other Options Are Wrong:
Each option covers a part of the function, but only "all of the above" captures the full role.Common Pitfalls:
Thinking transponders only amplify; frequency conversion is equally critical.Final Answer:
Performs all of the above-mentioned functions