Question

What is the output of a mixer circuit?

(a) Sum of frequencies

(b) Difference of frequencies

(c) Sum and difference of frequencies

(d) Multiplication of frequencies

The question was posed to me in examination.

This question is from Communication Receivers topic in section Radio Transmitters, Communication Receivers, Multiplexing and Demultiplexing of Avionics

Answer 1

Right answer is (c) Sum and difference of frequencies

To explain: The key circuit is the mixer, which acts as a simple amplitude modulator to produce sum and difference frequencies. The incoming signal is mixed with a local oscillator signal to produce this conversion.