Monolithic Microwave Integrated Circuit
Encyclopedia
A Monolithic Microwave Integrated Circuit, or MMIC (sometimes pronounced "mimic"), is a type of integrated circuit
(IC) device that operates at microwave
frequencies
(300 MHz to 300 GHz). These devices typically perform functions such as microwave mixing
, power amplification, low noise amplification
, and high frequency switching. Inputs and outputs on MMIC devices are frequently matched to a characteristic impedance
of 50 ohms. This makes them easier to use, as cascading of MMICs does not then require an external matching network. Additionally most microwave test equipment is designed to operate in a 50 ohm environment.
MMICs are dimensionally small (from around 1 mm² to 10 mm²) and can be mass produced, which has allowed the proliferation of high frequency devices such as cellular phones. MMICs were originally fabricated using gallium arsenide
(GaAs), a III-V compound semiconductor. It has two fundamental advantages over Silicon
(Si), the traditional material for IC realisation: device (transistor
) speed and a semi-insulating substrate
. Both factors help with the design of high frequency circuit functions. However, the speed of Si-based technologies has gradually increased as transistor feature sizes have reduced and MMICs can now also be fabricated in Si technology. The primary advantage of Si technology is its lower fabrication cost compared with GaAs. Silicon wafer diameters are larger (typically 8" or 12" compared with 4" or 6" for GaAs) and the wafer costs are lower, contributing to a less expensive IC.
Other III-V technologies, such as Indium Phosphide (InP), have been shown to offer superior performance to GaAs in terms of gain, higher cutoff frequency, and low noise. However they also tend to be more expensive due to smaller wafer sizes and increased material fragility.
Silicon Germanium
(SiGe) is a Si-based compound semiconductor technology offering higher speed transistors than conventional Si devices but with similar cost advantages.
Gallium Nitride
(GaN) is also an option for MMICs. Because GaN transistors can operate at much higher temperatures and work at much higher voltages than GaAs transistors, they make ideal power amplifiers at microwave frequencies.
Integrated circuit
An integrated circuit or monolithic integrated circuit is an electronic circuit manufactured by the patterned diffusion of trace elements into the surface of a thin substrate of semiconductor material...
(IC) device that operates at microwave
Microwave
Microwaves, a subset of radio waves, have wavelengths ranging from as long as one meter to as short as one millimeter, or equivalently, with frequencies between 300 MHz and 300 GHz. This broad definition includes both UHF and EHF , and various sources use different boundaries...
frequencies
Radio frequency
Radio frequency is a rate of oscillation in the range of about 3 kHz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals...
(300 MHz to 300 GHz). These devices typically perform functions such as microwave mixing
Frequency mixer
In electronics a mixer or frequency mixer is a nonlinear electrical circuit that creates new frequencies from two signals applied to it. In its most common application, two signals at frequencies f1 and f2 are applied to a mixer, and it produces new signals at the sum f1 + f2 and difference f1 -...
, power amplification, low noise amplification
Low-noise amplifier
Low-noise amplifier is an electronic amplifier used to amplify possibly very weak signals . It is usually located very close to the detection device to reduce losses in the feedline. This active antenna arrangement is frequently used in microwave systems like GPS, because coaxial cable feedline is...
, and high frequency switching. Inputs and outputs on MMIC devices are frequently matched to a characteristic impedance
Characteristic impedance
The characteristic impedance or surge impedance of a uniform transmission line, usually written Z_0, is the ratio of the amplitudes of a single pair of voltage and current waves propagating along the line in the absence of reflections. The SI unit of characteristic impedance is the ohm...
of 50 ohms. This makes them easier to use, as cascading of MMICs does not then require an external matching network. Additionally most microwave test equipment is designed to operate in a 50 ohm environment.
MMICs are dimensionally small (from around 1 mm² to 10 mm²) and can be mass produced, which has allowed the proliferation of high frequency devices such as cellular phones. MMICs were originally fabricated using gallium arsenide
Gallium(III) arsenide
Gallium arsenide is a compound of the elements gallium and arsenic. It is a III/V semiconductor, and is used in the manufacture of devices such as microwave frequency integrated circuits, monolithic microwave integrated circuits, infrared light-emitting diodes, laser diodes, solar cells and...
(GaAs), a III-V compound semiconductor. It has two fundamental advantages over Silicon
Silicon
Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...
(Si), the traditional material for IC realisation: device (transistor
Transistor
A transistor is a semiconductor device used to amplify and switch electronic signals and power. It is composed of a semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current...
) speed and a semi-insulating substrate
Wafer (electronics)
A wafer is a thin slice of semiconductor material, such as a silicon crystal, used in the fabrication of integrated circuits and other microdevices...
. Both factors help with the design of high frequency circuit functions. However, the speed of Si-based technologies has gradually increased as transistor feature sizes have reduced and MMICs can now also be fabricated in Si technology. The primary advantage of Si technology is its lower fabrication cost compared with GaAs. Silicon wafer diameters are larger (typically 8" or 12" compared with 4" or 6" for GaAs) and the wafer costs are lower, contributing to a less expensive IC.
Other III-V technologies, such as Indium Phosphide (InP), have been shown to offer superior performance to GaAs in terms of gain, higher cutoff frequency, and low noise. However they also tend to be more expensive due to smaller wafer sizes and increased material fragility.
Silicon Germanium
SiGe
SiGe , or silicon-germanium, is a general term for the alloy Si1−xGex which consists of any molar ratio of silicon and germanium. It is commonly used as a semiconductor material in integrated circuits for heterojunction bipolar transistors or as a strain-inducing layer for CMOS transistors...
(SiGe) is a Si-based compound semiconductor technology offering higher speed transistors than conventional Si devices but with similar cost advantages.
Gallium Nitride
Gan
Gan may refer to:-Computing and telecommunications:*.gan, the file extension for documents created by GanttProject*Generic Access Network formerly known as Unlicensed Mobile Access *Global Area Network- Mythology :...
(GaN) is also an option for MMICs. Because GaN transistors can operate at much higher temperatures and work at much higher voltages than GaAs transistors, they make ideal power amplifiers at microwave frequencies.
See also
- Integrated CircuitIntegrated circuitAn integrated circuit or monolithic integrated circuit is an electronic circuit manufactured by the patterned diffusion of trace elements into the surface of a thin substrate of semiconductor material...
- Hybrid Integrated Circuit
- Transmission lineTransmission lineIn communications and electronic engineering, a transmission line is a specialized cable designed to carry alternating current of radio frequency, that is, currents with a frequency high enough that its wave nature must be taken into account...
- HEMTHEMTHigh electron mobility transistor , also known as heterostructure FET or modulation-doped FET , is a field effect transistor incorporating a junction between two materials with different band gaps as the channel instead of a doped region, as is generally the case for MOSFET...