The incoming radio frequency and local oscillator frequency mix in the crystal diode detector. Ī major application of the heterodyne process is in the superheterodyne radio receiver circuit, which is used in virtually all modern radio receivers.įessenden's heterodyne radio receiver circuit. Heterodyne frequencies are related to the phenomenon of " beats" in acoustics. Typically, only one of the heterodynes is required and the other signal is filtered out of the output of the mixer. The new signal frequencies are called heterodynes. In the most common application, two signals at frequencies f 1 and f 2 are mixed, creating two new signals, one at the sum of the two frequencies f 1 + f 2, and the other at the difference between the two frequencies f 1 − f 2. The two input frequencies are combined in a nonlinear signal-processing device such as a vacuum tube, transistor, or diode, usually called a mixer. Heterodyning is used to shift signals from one frequency range into another, and is also involved in the processes of modulation and demodulation. Frequency mixer symbol used in schematic diagramsĪ heterodyne is a signal frequency that is created by combining or mixing two other frequencies using a signal processing technique called heterodyning, which was invented by Canadian inventor-engineer Reginald Fessenden.
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