What receiver circuit actually produces the intermediate frequency (IF)?

• A. Mixer
• B. Amplifier
• C. Oscillator
• D. Filter

Answer: (A)

In a superheterodyne receiver, the intermediate frequency is created by the mixer. The incoming radio frequency signal is combined with a locally generated oscillator signal in the mixer, producing new frequencies that are the sum and the difference of the two. The fixed intermediate frequency is chosen by setting the local oscillator so that this difference equals the IF you design around. Once the IF is generated, it’s easier to filter and amplify than the original RF. The oscillator provides the reference frequency, but it’s the mixer that actually produces the IF. The filter then selects the IF component, and the amplifier boosts it, but neither generates the IF on its own.