What practical action is required at the receiver for DSB-SC to demodulate properly that is not required for standard AM?

What practical action is required at the receiver for DSB-SC to demodulate properly that is not required for standard AM?

• A. The transmitter includes a carrier.
• B. Carrier reinsertion is not needed for DSB-SC.
• C. Demod doesn't depend on reinsertion.
• D. Carrier reinsertion at receiver is required for DSB-SC demodulation.

Answer: (D)

Demodulating a DSB-SC signal requires coherent detection with a locally generated carrier. In DSB-SC, the transmitted signal has no carrier term, just m(t) cos(ωc t). Without a carrier in the received signal, an envelope detector won’t reliably recover the original modulation. To pull out m(t), the receiver must reinsert a carrier at the same frequency and (ideally) phase as the transmitted one and mix the received signal with it, then low-pass filter. This carrier reinsertion at the receiver is what enables proper demodulation of DSB-SC. The other ideas imply that reinserting the carrier isn’t needed or that the demodulation doesn’t depend on it, which would fail for this suppressed-carrier form.

Demodulating a DSB-SC signal requires coherent detection with a locally generated carrier. In DSB-SC, the transmitted signal has no carrier term, just m(t) cos(ωc t). Without a carrier in the received signal, an envelope detector won’t reliably recover the original modulation. To pull out m(t), the receiver must reinsert a carrier at the same frequency and (ideally) phase as the transmitted one and mix the received signal with it, then low-pass filter. This carrier reinsertion at the receiver is what enables proper demodulation of DSB-SC. The other ideas imply that reinserting the carrier isn’t needed or that the demodulation doesn’t depend on it, which would fail for this suppressed-carrier form.