Microwave integrated circuits, or MICs, are a type of microchip semiconductor designed to operate specifically over microwave frequencies, often at 1 gigahertz (GHz) or higher. The specific ability to transmit over microwaves is usually what differentiates MICs from other types of integrated circuits. MICs are widely-used in small electronic devices that function via electronic and electromagnetic frequencies, such as cell phones, GPS devices, remote-controlled systems, and imaging devices. Their small size allows them to be used in multiple handheld, wireless devices, and the nature of the MIC is such that one chip can operate as a self-contained device, using only a single semiconductor wafer.
MICs were first designed in the 1940s, and evolved from the basic microwave circuit as demand and technologies of the time enabled advances in wafer-based circuit fabrication. Since then, microwave integrated circuits have matured from simple, single-function circuits to complex, multi-function circuits of increasingly small sizes and complex capabilities. They form the root of the microwave and semiconductor manufacturing industries, and many types of MICs can be cheaply and efficiently mass-produced for use in consumer electronics, science, and industry.
Specialized types of MICs have different benefits and applications, which are often determined by their method of fabrication. Hybrid microwave integrated circuits (HMICs) are made by placing discrete components on a circuit board, referred to as a substrate. The individual components can be capacitors, resistors, transistors, or other chips. Together, they form the entire MIC. The materials used in fabrication and component soldering can affect the frequency, electrical properties, and overall performance of the circuit.
Monolithic microwave integrated circuits, also known as MMICs, require a more complex design, in which the entire circuit is designed as a single chip and all components are fabricated on the semiconducting substrate. MMICs are often used in satellite systems that require small, inexpensive circuits that still offer high speed and performance. These circuits operate at bands anywhere from 300 megahertz (MHz)to 300 GHz, and are capable of multiple frequency and power manipulation functions.
Many users find MMICs to offer significant advantages over hybrid circuits due to the design differences and performance capabilities. The modern concept of the microwave integrated circuit generally refers to the MMIC — which is considered an advance over the original, larger, heavier MIC — despite MMIC limitations, which can include functional inflexibility after initial fabrication. For more robust, scalable, and flexible circuit designs, many integrate multiple multi-function, specialized MMICs into larger, more complex microwave integrated circuits.