IC Substrate - Monolithic microwave integrated circuit

Monolithic microwave integrated circuits are integrated circuit (IC) devices that operate 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. The input and output on a single-chip microwave integrated circuit device are usually matched with a characteristic impedance of 50 ohms. This makes them easier to use, as cascaded monolithic microwave integrated circuits do not require an external matching network. In addition, most microwave testing equipment is designed to operate in a 50-ohm environment.

Sometimes also known as Radio Frequency Integrated Circuit (RFIC), it is a type of high-frequency amplification device that has emerged with the development of semiconductor manufacturing technology, especially the improvement of ion doping control level and the maturity of transistor self-assembly technology. In this type of device, each resistor used as a feedback and DC bias component adopts a thin film resistor with high-frequency characteristics and is packaged on a chip together with each active device, making there almost no connection between the components, thereby minimizing the inductance of the circuit and minimizing the distributed capacitance. Therefore, it can be used in single-chip microwave integrated circuit amplifiers with high operating frequency and bandwidth.

Monolithic microwave integrated circuits are very small in size (from 1 square millimeter to 10 square millimeters) and can be mass-produced, making high-frequency devices such as mobile phones popular. Monolithic microwave integrated circuits were originally manufactured using gallium arsenide (GaAs), a type of III-V compound semiconductor. Compared with the traditional material silicon (Si) used to implement ICs, it has two basic advantages: device (transistor) speed and semi-insulating substrate. Both of these factors contribute to the design of high-frequency circuit functions. However, as the characteristic size of transistors decreases, the speed of Si-based technology gradually increases, and now Si technology can also be used to manufacture monolithic microwave integrated circuits. The main advantage of Si technology is its lower manufacturing cost compared to GaAs. The diameter of silicon wafers is larger, resulting in lower chip costs, which helps to reduce the cost of ICs.

The Use of Monolithic Microwave Integrated Circuits

Monolithic microwave integrated circuits have become an important pillar in the development of various high-tech weapons, and have been widely used in various advanced tactical missiles, electronic warfare, communication systems, land, sea, and air-based phased array radars (especially airborne and spaceborne radars). They are also used in mobile phones, wireless communication, personal satellite communication networks, and global positioning systems A huge market is rapidly developing in areas such as live satellite reception and millimeter wave automatic collision avoidance systems.

Characteristics of Monolithic Microwave Integrated Circuits

1) Due to the high electron mobility, wide bandgap, wide operating temperature range, and good microwave transmission performance of substrate materials such as GaAs and InP, monolithic microwave integrated circuitshave the characteristics of low circuit loss, low noise, wide frequency band, large dynamic range, high power, high additional efficiency, and strong resistance to electromagnetic radiation.

2) Single-chip microwave integrated circuits have a flexible design, high component density, and few leads and solder joints. Compared with microwave/millimeter wave circuits made of discrete components or hybrid circuits, they have advantages such as small size, lightweight, high reliability, wide operating frequency band, and low power consumption. They can be used in integrated electronic warfare systems, airborne synthetic aperture radar, satellite communication system terminals, and precision-guided ammunition terminal control devices.

According to the differences in manufacturing materials and internal circuit structures, monolithic microwave integrated circuits can be divided into two categories: one is MMICs based on silicon transistors, and the other is monolithic microwave integrated circuits based on gallium arsenide field-effect transistors (GaAs FETs). GaAs FET type monolithic microwave integrated circuits have the characteristics of high operating frequency, wide frequency range, large dynamic range, and low noise, but they are expensive and therefore have few applications; The single chip microwave integrated circuit of silicon transistor has excellent performance, convenient use, and low price, making it widely used.