Envelope detection works best when a carrier is present; AM includes carrier; easier demod. Which option correctly states this idea?

Envelope detection works best when a carrier is present; AM includes carrier; easier demod. Which option correctly states this idea?

• A. Envelope detection requires high RF frequency.
• B. Envelope detection works best when a carrier is present; AM includes carrier; easier demod.
• C. Envelope detection is best for carrierless signals.
• D. Envelope detection is not used in AM.

Answer: (B)

Envelope detection works by rectifying the RF signal and then filtering to follow the slowly varying envelope, which carries the information. This approach only makes sense when there is a carrier component, because the envelope—the varying amplitude of the carrier—directly represents the modulating signal. In standard AM, the carrier is present, so the envelope is well-defined and proportional to the message, making a simple diode detector plus an RC filter an easy, reliable way to recover the audio. If the carrier is absent or minimized (as in some suppressed-carrier schemes), there isn’t a stable envelope to follow, and envelope detection becomes ineffective. That’s why the statement that envelope detection works best with a carrier present and that AM includes a carrier, making demodulation easier, is the best description. The other choices misstate the role of the carrier or imply requirements (like high RF frequency) that aren’t the main factor for envelope detection.

Envelope detection works by rectifying the RF signal and then filtering to follow the slowly varying envelope, which carries the information. This approach only makes sense when there is a carrier component, because the envelope—the varying amplitude of the carrier—directly represents the modulating signal. In standard AM, the carrier is present, so the envelope is well-defined and proportional to the message, making a simple diode detector plus an RC filter an easy, reliable way to recover the audio. If the carrier is absent or minimized (as in some suppressed-carrier schemes), there isn’t a stable envelope to follow, and envelope detection becomes ineffective. That’s why the statement that envelope detection works best with a carrier present and that AM includes a carrier, making demodulation easier, is the best description. The other choices misstate the role of the carrier or imply requirements (like high RF frequency) that aren’t the main factor for envelope detection.