Gan solution: small package to meet the challenge of large radar
X-band (8 GHz to 12 GHz) radar is a key equipment suitable for commercial navigation. Aviation is a major field in which X-band radar equipment is widely used. At the same time, the equipment is also widely deployed in many application fields, including UAV, maritime ship traffic control, meteorological monitoring, bird activity monitoring near the airport and anti freezing remote sensing.
According to the report of strategy analytics, a market research organization, X-band radar is the largest radar segment. The sales of this band radar is close to US $6.3 billion in 2018, and the compound annual growth rate of corresponding expenditure is expected to be 3.4%, which will reach US $8.7 billion in 2028.
However, not any X-band radar has significant growth opportunities. Active electronic scanning array (AESA) system is more and more popular in research and development. The system is mainly used on large airborne platforms, as well as in land and maritime segments.
The AESA system uses active arrays, each with hundreds or even thousands of antennas. Each antenna has its own phase and gain control. The interference or superposition of a single wave array of antenna elements can generate plane waves, which can effectively generate radio beams moving in a specific direction. AESA radar system electronically controls the beam by transferring the phase of antenna elements.
The spacing of antenna elements is usually half wavelength to reduce exposure in the near field. AESA radar also often needs to diffuse signals in a wide range of high frequencies. This frequency agility allows the radar to quickly search for targets in the sector. This also makes them more difficult to detect in background noise. This allows ships and aircraft to send high-power radar signals while maintaining concealment and bringing better anti-jamming capability.
These requirements pose some challenges for Engineers: each antenna element must be small and light enough to accommodate small wavelength spacing, while making the overall system size and weight controllable for use in the air and at sea. However, according to different applications, the radar system must be strong enough to output power from hundreds of watts to up to 100 kW anywhere. Therefore, the radar system needs efficient heat dissipation, but this increases the size and weight.
In many of these use cases, you need to Size, weight, power and cost (swap-c) Evaluate the system. Replacing only a few components in the system will not have much impact on these considerations. Therefore, the technology that can enable AESA radar system must show significant advantages in swap-c improvement.
Enabling technology: Gan
Gallium nitride (GAN) is a technology that can help radar designers overcome many challenges such as power, heat dissipation, weight and size, and cost-effectiveness. This material has high electron mobility. Compared with silicon, Gan devices have low gate charge and low output capacitance, and can produce higher gain at higher frequency more efficiently.
Gan has a wide energy band gap and a very high critical breakdown electric field, which will bring excellent high-temperature reliability, excellent robustness under high supply voltage and excellent power density.
Using silicon carbide (SIC) as GaN substrate can achieve low thermal expansion, low lattice mismatch and excellent thermal conductivity, so as to give full play to the characteristics of GaN. The thermal conductivity of 4H semi insulating polytype SiC is 430 w / MK, while that of silicon is as low as 146 w / MK. This enables very high power density and efficient heat dissipation, avoiding extreme channel temperatures that make the equipment inoperable.
Therefore, the silicon carbide based gallium nitride (GaN on SiC) amplifier in AESA radar can achieve higher performance and equivalent output power in a smaller volume, while saving heat dissipation requirements. However, in order to significantly reflect the improvement advantages of swap-c, more needs to be done in device technology.
Encapsulation is the key
The further development of phased arrays such as AESA radar system needs to reduce the size and integrate the components more closely.
Monolithic microwave integrated circuit (MMIC) is one of such technologies. It can manufacture the complete functional modules of multiple components in a single device, so as to improve the circuit density. MMIC also has some additional advantages, including reducing component mismatch, reducing signal delay (due to the shorter distance between components on MMIC), and reducing overall bill of materials (BOM) costs.
MMIC adopts square flat pinless (QFN) package, which can further reduce cost and size. Because QFN package uses short bonding leads, which helps to reduce lead inductance, its exposed copper bare chip pad provides excellent thermal performance.
Wolfspeed cmpa901a020s device adopts 6 & times; 6 mm QFN package, this is a 20W Gan on SiC high power amplifier, which can operate in the frequency range of 9 GHz to 10 GHz. It is suitable for pulse radar applications such as marine meteorological radar. The amplifier has three-stage gain, can provide large signal gain greater than 30 dB and efficiency greater than 50%, can meet lower system DC power requirements, and support simplified system thermal management solutions.
Wolfspeed cmpa9396025s is another Gan MMIC, which can integrate many technologies to maximize the improvement of swap-c. The three-stage device is designed for 9.3-ghz to 9.6-ghz, using 6 & times; 6 mm QFN package,At 100 - & micro; The power is 25 W under the condition of s pulse width and 10% duty cycle.
Wolfspeed cmpa801b030 Series in MMIC Amplifier works in the frequency range of 7.9-ghz to 11 GHz and can support wider bandwidth and higher power in X-band. The typical output value is up to 40 W, the large signal gain is greater than 20 dB, and the power additional efficiency is up to 40%. The product series adopts 7 & times; 7 mm plastic secondary injection molding QFN also provides bare chip and 10 pin metal / ceramic mounting flange flanged package, resulting in more outstanding electrical and thermal performance.
▲ wolfspeed cmpa801b030 provides bare chip and highly compact package to maximize the improvement of swap-c
Note: eccn of all devices listed above are 3a001 b.2
Technical innovation of enabling radar
Strategy analytics believes that the above Gan devices are conducive to promoting the rapid adoption of AESA radar by various platforms, and the Gan expenditure of radar system will increase from US $171.8 million in 2018 to US $734.1 million in 2028.
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