heterodyne

(hĕt'ər-ə-dīn')
adj.
Having alternating currents of two different frequencies that are combined to produce two new frequencies, the sum and difference of the original frequencies, either of which may be used in radio or television receivers by proper tuning or filtering.

tr.v., -dyned, -dyn·ing, -dynes.
To combine (a radio-frequency wave) with a locally generated wave of different frequency in order to produce a new frequency equal to the sum or difference of the two.

[HETERO- + -dyne, power, frequency (from Greek dunamis, power; see dynamic).]

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The mixing of two electrical or acoustic signals to produce a third equal to either the sum of or the difference between their frequencies. For example, if a signal with a frequency of 1000 Hz were to be mixed with another signal of 600 Hz, besides the original two frequencies two new frequencies will be produced: 1600 Hz (1000 + 600), and 400 Hz (1000 − 600). Radar receivers are of the heterodyne type (as contrasted to the superregenerative type) because the very high radio frequencies used in radar are difficult to amplify. A target signal is heterodyned with a current of lower frequency produced by a klystron oscillator and the resulting intermediate-frequency signal can then be highly amplified for subsequent presentation or analysis.

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