Military and communications applications of millimeter wave devices
Since the early 1980s, the United States Department of Defense Advanced Technology Research Project (DARPA) and the National Aeronautics and Space Administration (NASA) have been focusing on the research of millimeter wave solid-state devices and circuits, and have achieved remarkable results, which have been applied to new weapons and equipment, as shown in the following table. For silicon devices, which operate at frequencies up to the GHz range, the materials used for W-band or higher MMIC are primarily InP-HBT, HEMT, or GaAsMHEMT. Among them, the newly reported InP MMIC low noise amplifier is in the W band, and the noise coefficient is between 2-5dB. However, In resources are gradually decreasing, while InP single crystal growth is difficult, fragile, and difficult to further improve the mobility of its device performance has been close to the limit level, people have been looking for higher mobility and thermal conductivity of materials, the emergence of wafer scale graphene is expected to solve these problems.

The ultra-high speed mobility of graphene can improve the operating frequency of the device to reach the millimeter band, and the design of double-layer graphene can effectively avoid the Haug rule to achieve ultra-low noise characteristics, which is self-evident. At present, the United States DARPA program has set the direction of graphene research as millimeter wave low noise amplifiers. In order to keep pace with The Times, support the future modernization of national defense, achieve flexible mobile, rapid response, safe and concealed military and aerospace communications, and meet the needs of the new peace cause and the development of the world situation in the 21st century, the development of graphene UHF and low noise devices is extremely necessary.

 

If a high-performance low noise amplifier is connected at the front end of the receiving system, the noise of the back-end circuit can be suppressed if the gain of the low noise amplifier is large enough, then the noise factor of the whole receiver system mainly depends on the noise of the amplifier. If the noise figure of the low noise amplifier is reduced, the noise figure of the receiver system will also be smaller, the signal-to-noise ratio will be improved, and the sensitivity will be greatly increased. It can be seen that the performance of low noise amplifier restricts the performance of the whole receiving system, and also plays a decisive role in improving the technical level of the whole receiving system.

Low noise amplifier is the key component of radar, electronic countermeasures and telemetry remote control receiving system. L and S band low noise amplifiers are generally used in telemetry and remote control systems. In electronic countermeasures, radar reconnaissance, because the frequency range of the signal to be received is unknown, in fact, the frequency range is also one of the contents of the reconnaissance, so the frequency of the receiving system is required to be wide enough, then the frequency of the amplifier is also required to be wide enough. Moreover, radar reconnaissance receives refracted waves emitted by radar, which is one-way reception; The radar receives the target echo, so that the reconnaissance aircraft can detect the radar target far beyond the radar's range. The detection distance of the receiver with high sensitivity is far, such as the super-heterodyne receiver with high sensitivity can achieve ultra-long-range reconnaissance to monitor the launch of the enemy long-range missile, so to increase the detection distance, it is necessary to improve the sensitivity of the receiver, which requires a high-performance low noise amplifier.

In international satellite communication applications, the main development requirements of low noise amplifiers are improved performance and reduced cost. As the volume of international traffic increases rapidly year after year, the increasing communication requirements must be met by improving the performance of low noise amplifiers. Therefore, continuous efforts should be made to extend the bandwidth and reduce the noise temperature of the band low noise amplifier. From an economic point of view, the cost of the entire system of satellite communications must be reduced to a level that makes it competitive with submarine cable systems. Reducing the noise temperature of a low noise amplifier is one of the most effective ways to reduce the cost of a satellite communication system, because the diameter of the ground station antenna can be reduced by improving the noise temperature performance. On the other hand, in domestic satellite communication applications, emphasis has been placed on the maintenance-free characteristics of low noise amplifiers as well as low noise and broadband performance, because unmanned operating modes are increasingly widely used in these systems, especially in television receiving ground stations.

Low noise amplifiers for satellite communication can be divided into two types - low noise parametric amplifiers and field effect transistor low noise amplifiers. These low noise amplifiers are used in several frequency bands, including 4GHz, 12 GHz and millimeter wave bands. There are many types of broadband low noise amplifier implementations. SiGe process has excellent radio frequency performance, and because of its high cost performance, it is widely used in mobile communications, satellite positioning and RFID markets. The SiGe process can also be integrated with conventional digital analog circuits to produce fully functional SoC chips.

At present, the use of SiGe materials to make RF integrated circuits has become an international research hotspot. Implementing front-end low noise amplifiers is one of the challenges in the recently emerging ultra-wideband RF communication systems. The industry has been pursuing fully integrated ultra-wideband communication system SOC, compared with other processes, CMOS process is easier to integrate the system, so people have designed a lot of CMOS process ultra-wideband low noise amplifier. The 4GHz band is currently the most common frequency band for satellite communications, which is used for international satellite communications and domestic satellite communications, including TV receiving ground stations. In these fields, a variety of low noise amplifiers have been developed and have been applied.

At present, millimeter wave devices have been used in existing equipment abroad, radar, precision guidance system, smart weapon seeker, military secure communication system and electronic warfare countermeasures system based on millimeter wave solid-state devices began to be equipped with a large number of U.S. troops, and achieved good actual combat results in the two Gulf Wars and the Kosovo War.