Double Balanced Mixer
In electronics a mixer or frequency mixer is a nonlinear electrical circuit that creates new frequencies from two signals applied to it. In its most common application, two signals at frequencies f1 and f2 are applied to a mixer, and it produces new signals at the sum f1 + f2 and difference f1 - f2 of the original frequencies.
Schematic diagram of a double-balanced passive diode mixer. There is no output unless both f1 and f2 inputs are present, though f2 (but not f1) can be DC.
The first two signals in the above image are sine waves (blue and magenta). The blue Sine wave frequency is at 10MHz and the magenta at 12MHz. The third signal (cyan) is a double balanced mixer of signal one and two. This means that it is both the sum and differences of the two frequencies. This can be seen clearly in the frequency spectrum on the right side of the above image.
The first signal in the above image is a sine wave with a frequency of 5MHz. (yellow). The second wave (gray) is a red noise wave with minimum frequency at 1MHz and maximum frequency at 2MHz. The third signal (red) is a double balanced mixer of signal one and two. This means that it is both the sum and differences of the two frequencies. This can be seen clearly in the frequency spectrum on the right side of the above image.
The first signal in the above image is a sine wave with a frequency of 50MHz. (green). The second wave (white) is a blue noise wave with minimum frequency at 10MHz and maximum frequency at 20MHz. The third signal (yellow) is a double balanced mixer of signal one and two. This means that it is both the sum and differences of the two frequencies. This can be seen clearly in the frequency spectrum on the right side of the above image.