frequency mixing
In frequency mixing, signals of one frequency range are transferred to another frequency range without affecting the signal content.
In each frequency mixing, the frequencies to be mixed are mixed with a new frequency of an oscillator, always forming two frequency bands above and below the oscillator frequency, from the sum and difference of the oscillator frequency with the mixing frequency.
Example: If an oscillator frequency of 1 MHz is mixed with an input frequency of 10 kHz, then three signals are produced: the oscillator signal of 1 MHz, the difference signal of 990 kHz and the sum signal of 1.010 MHz. The same applies to mixing with frequency bands. This results in lower and upper sidebands.
When mixing, one of these two completely identical frequency bands can be used for further processing, amplification and demodulation. If one uses the lower sideband, i.e. the difference signal, one speaks of a downward mixing, in the other case of an upward mixing.