Question

The main advantage of TDM over FDM is

• A. It needs less power
• B. It is simple circuitry
• C. It needs less bandwidth
• D. It gives better S/N ratio

Hint:

TDM: Signals share time slots. Simpler digital implementation. No frequency guard bands needed, but guard times may be.
FDM: Signals occupy different frequency bands. Requires modulators, demodulators, bandpass filters. Frequency guard bands often needed.
Main advantages of TDM often include simpler implementation for digital signals and flexibility.

Answer 1

The Correct Option is B

TDM (Time Division Multiplexing) and FDM (Frequency Division Multiplexing) are two common methods for combining multiple signals onto a shared medium.
TDM: Signals are interleaved in the time domain. Each signal is allocated specific time slots.
FDM: Signals are modulated onto different carrier frequencies and transmitted simultaneously in different frequency bands. Comparing TDM and FDM: (a) "It needs less power": Power requirements depend on many factors, not solely on TDM vs FDM. Not a universal main advantage. (b) "It is simple circuitry": TDM circuitry, especially for digital signals, can be simpler to implement using digital logic (multiplexers, demultiplexers, timing circuits) compared to FDM which requires precise modulators, demodulators, and sharp bandpass filters for each channel to prevent interference. This is often cited as an advantage of TDM, particularly in digital systems. (c) "It needs less bandwidth": This is generally FALSE. TDM systems typically require a wider bandwidth for the composite signal than a single channel, because multiple signals are being squeezed into time slots, effectively increasing the data rate if the per-channel rate is maintained. FDM requires a total bandwidth that is roughly the sum of individual channel bandwidths plus guard bands. The bandwidth comparison is complex and depends on the specifics. (d) "It gives better S/N ratio": S/N ratio depends on many factors including modulation scheme, channel noise, power, etc. TDM itself doesn't inherently guarantee a better S/N ratio than FDM. Considering the common advantages cited:
TDM is well-suited for digital signals and can be implemented with simpler digital circuitry.
TDM does not require guard bands between channels in the frequency domain (as FDM does), though it needs guard times between time slots.
TDM can be more flexible in allocating capacity (e.g., variable time slots).
Crosstalk in TDM is often less problematic than intermodulation distortion in FDM (if FDM uses non-linear amplifiers). Among the given options, "It is simple circuitry" (especially for digital TDM) is a recognized advantage of TDM over FDM, which involves more complex analog components like filters and modulators. \[ \boxed{\text{It is simple circuitry}} \]