Which device or technique splits a high-speed signal into multiple frequency bands so several channels can share the same medium simultaneously?
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At-switch
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Bmodem
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Cfrequency-division multiplexer
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Dtime-division multiplexer
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ENone of the above
Answer
Correct Answer: frequency-division multiplexer
Explanation
Introduction / Context:Multiplexing enables multiple independent signals to share one medium efficiently. Two classic families are Frequency-Division Multiplexing (FDM) and Time-Division Multiplexing (TDM), each using a different separation axis (frequency vs time).
Given Data / Assumptions:
- High-speed composite signal needs to be split into parallel channels.
- Separation is done by frequency bands, not time slots.
Concept / Approach:An FDM device (frequency-division multiplexer) divides available bandwidth into non-overlapping frequency bands, assigning each channel a separate band. Guard bands reduce interference between adjacent channels.
Step-by-Step Solution:
1) Identify requirement: concurrent channels using different frequencies. 2) Map requirement to FDM rather than TDM. 3) Select the device name: frequency-division multiplexer.Verification / Alternative check:Analog cable systems and some radio backhauls use FDM by modulating each channel onto a distinct carrier frequency. Spectrum analyzers show multiple peaks corresponding to channels.
Why Other Options Are Wrong:
- t-switch: Not a standard multiplexing device term.
- modem: Modulates/demodulates a single data stream, not a multi-channel frequency splitter by itself.
- time-division multiplexer: Separates channels into time slots, not frequency bands.
- None of the above: Incorrect because FDM exactly fits.
Common Pitfalls:Confusing TDM with FDM; assuming a modem inherently multiplexes many user channels in frequency; overlooking guard bands and channel spacing in FDM design.
Final Answer:frequency-division multiplexer