The enormous growth in the wireless communication industry and the need for low cost, high bandwidth, data links has resulted in a demand for active circuits that operate at microwave and millimeterwave frequencies. Systems operating at these frequencies are attractive because only a small fractional bandwidth is needed for a high data rate link. Also, they use antennas which can be both directive and small. Communications applications include cell phones, satellite communications, and deep space probes. Other applications include radars (navigational, weather, automotive), radiometers and global positioning systems.

The monolithic microwave ICs (MMICs) used in these applications are analog circuits which downconvert a modulated microwave signal to a baseband signal or upconvert the baseband signal to a microwave signal. The baseband signals are lower frequency and can be processed by conventional ICs. Since MMICs run at very high frequency, they are, debatably, the most high tech part of a cellular phone. Their performance sets the range of the wireless link and is one of the most important factors effecting battery life and call quality. They must be sensitive (for increased range), efficient (less battery and weight), and linear (higher channel density). MMICs often consist of several subcircuit types: low noise amplifiers, mixers, power amplifiers, oscillators, and switches.