Analog Multipliers, Mixers, Modulators

Abstract

The multiplication of two analog, real-time signals is an important, required circuit function. A particular application concerns the translating of a frequency spectrum from one passband to another. This is often referred to by the term, mixing. In the early days of electronics, before the availability of reliable analog multipliers, two signals were combined (mixed) in a nonlinear device and the mixing (beating) of the two signals produced sum and difference components of the signals and their harmonics comparable to intermodulation distortion presented in Chapter 3. For IM2, the critical factor is the presence of the square-law term of the device transfer characteristic which leads to the (cross) product of the two signals. With a more complicated circuit, easily realizable in IC form, the multiplication can be achieved directly.