RF mixers are electronic devices used to convert signals from one frequency to another in RF and microwave communication systems. They operate by combining two or more input signals and producing an output signal containing the sum and difference frequencies of the input signals. RF mixers find applications in frequency conversion, modulation, demodulation, upconversion, downconversion, and heterodyning processes in wireless communication systems, radar systems, test and measurement equipment, and satellite communication systems. They play a critical role in translating signals between different frequency bands, enabling efficient signal processing and transmission in RF systems.