Oscillator – What is Meant by ‘Local’ in Local Oscillator?

oscillatorterminology

We know that a local oscillator (LO) is an electronic oscillator used with a mixer to change the frequency of a signal.

  • But what do we mean by 'local'?
  • How is 'local oscillator' different from normal oscillator?
  • Why can't a normal oscillator, like an LC-tank circuit or an opamp circuit, be used in a heterodyne receiver?

Best Answer

You got that wrong: The "local" in oscillator doesn't describe the kind of oscillator used. It could just be an LC-tank, it could be a crystal-derived oscillator, it could be something synthesized from a reference clock or something recovered from the data stream received:

The "local" in oscillator refers to the fact that it's what the mixer uses locally to mix down or up, as opposed to the oscillator at the other end of the communication, which simply isn't the same oscillator.