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9-3: Frequency Conversion
Mixers accept two inputs: The signal to be translated to another frequency is applied to one input, and the sine wave from a local oscillator is applied to the other input.
Like an amplitude modulator, a mixer essentially performs a mathematical multiplication of its two input signals.
The oscillator is the carrier, and the signal to be translated is the modulating signal.
The output contains not only the carrier signal but also sidebands formed when the local oscillator and input signal are mixed.