Which statement describes a superheterodyne receiver and its purpose?

• A. A receiver that converts RF to a fixed intermediate frequency via mixing with a local oscillator to improve selectivity.
• B. A receiver that converts RF directly to baseband for processing
• C. Amplifies RF without frequency conversion
• D. Demodulates AM directly at RF

Answer: (A)

The main idea is that a superheterodyne receiver converts the incoming RF signal to a fixed intermediate frequency by mixing it with a locally generated oscillator signal. This fixed IF lets the receiver use highly selective, fixed-frequency filters and stages, so it can achieve sharp selectivity and good image rejection across a wide range of received frequencies. The mixer produces the IF as the difference (often) between the RF and LO frequencies, and the LO is set so that the desired channel lands on this constant IF. Once there, the signal is filtered, amplified, and then demodulated. That fixed IF is the core advantage, because it makes the filtering and amplification more effective than trying to filter at the original RF frequency.

Other approaches described wouldn’t provide that same fixed-IF advantage: converting directly to baseband bypasses the fixed filters, making selectivity more challenging; amplifying RF without any frequency conversion skips the benefit of a tunable, fixed IF altogether; demodulating directly at RF also bypasses the clear separation of tuning, filtering, and demodulation that the IF stage provides.