Build Your Own Transistor Radios

Chapter 14Mixer Circuits and Harmonic Mixers

An idealized mixer is a multiplier circuit that takes two signals and literally multiplies the values of each signal to provide an output. In one sense, this concept is easier to understand with multiplication of numbers. For example, there are two analog signals, each connected to an analog-to-digital converter (ADC). The digital outputs from the two ADCs then provide numbers from each signal, and these numbers are updated over time. If the outputs of the ADCs are fed to a digital multiplier, then the output of the digital multiplier will provide a stream of numbers that are the product of the two streams of numbers from the outputs of the ADCs. The output of the digital multiplier then is connected ...