Microchip strengthens GaN-on-SiC with MMIC for satellite and 5G



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Modern satellite systems are based on geostationary constellations that offer excellent coverage of the earth’s surface and fast broadband data transmission. The new MMIC power amplifier GMICP2731-10 from Microchip Technology utilizes the Ka-band and the high RF output power and helps to meet the stringent performance requirements of satellite communications through the use of GaN-on-SiC technology.

In an interview with the EE Times, Mike Ziehl, Senior Manager Product Marketing at Microchip Technology, highlighted the features of this new model and the upcoming applications in aerospace and 5G. The new device is Microchip’s first Gallium Nitride (GaN) monolithic microwave integrated circuit (MMIC) for the satellite communications market. The technology used is 0.15 µm GaN-on-SiC and offers an output power of up to 10 W in the 27.5 to 31 GHz band.

The satellite communications industry has gradually moved to higher frequency bands to support the growing demand for bandwidth, including the X, Ku, K, and Ka bands. At these frequencies, GaN supports high throughput, higher performance and a large bandwidth.

GaN-on-SiC for HF
RF architectures have to be scalable, efficient and extremely compact. 5G not only requires densification at the macro level with the installation of further base stations, but also a high power density at the device level. To meet the demands for lower power consumption, smaller form factors and better performance in terms of thermal management, GaN-based RF power amplifiers are expected to become mainstream in the market due to their improved performance.

“Our initial focus was on Ka-band satellites. But customers also found the product for 5G, which does not work at 30 GHz depending on the country, so gallium arsenide is a better comparison company as long as it is in the operating range, “says Ziehl.

Gallium nitride solutions have emerged as an important component for 5G RF and satellite communications. The question is which substrate to apply. GaN-on-SiC has three times the thermal conductivity of GaN-on-Si, which allows devices with a much higher voltage and higher power density to operate with less heat loss. In addition, the chemical structure of GaN-on-SiC allows devices to be fabricated without defects in the crystals, unlike silicon, which does not align well with GaN.

The improved energy density means that smaller solutions can be built, which saves not only costs but also weight, which is particularly important in aerospace applications. GaN-on-SiC is robust with minimal performance penalty. Technology research shows that while GaN offers slightly better efficiency than GaAs at a similar output power, the size reduction can be up to 70% due to the higher power density and thermal performance.

Microchip solution
The GMICP2731-10 operates over the 3.5 GHz bandwidth, and its power increase efficiency is 20% and it achieves a saturated output power of 39 dBm from 27.5-31 GHz and a return loss of 15 dB. A symmetrical architecture enables the GMICP2731-10 to be well matched to 50 ohms and includes integrated DC blocking capacitors at the output to simplify design integration.

“With a corresponding pin, it is possible to monitor the current output power so that a sensor or microprocessor acting on this pin can make appropriate decisions,” says Ziehl.

Figure 1: 27GHz- VD = 24V IDQ = 100mA temperature = 25ºC (source: Microchip)
Figure 2: 31GHz- VD = 24V IDQ = 100mA temperature = 25ºC (source: Microchip)

Complex modulation schemes such as 128-QAM and increasingly efficient demands on semiconductor technology have broken new ground for designers to meet market demands. The geometry used is chosen according to the operating frequency, in this case a layer of 0.15 µm is used to meet the satellite requirements.

Microchip highlighted that high-performance GaN MMICs can achieve more than 30 percent less power and weight than their GaAs counterparts, a win for satellite OEMs. Microchip is offering a demo board for those unfamiliar with the technology to help reduce the time to market for the product. “Figure 3 shows the board with its RFA connectors with a chip in the middle, relatively easy to connect and use. Raise the drain voltage to 24 volts, then adjust the gate more positive until you see about 110 milliamps of current. And then make sure you are below the current limit, which we say is five amps, ”said Ziehl.

Figure 3: GMICP2731-10 Evaluation Board (Source: Microchip)

Material suppliers are implementing new manufacturing solutions to provide lower costs and easier implementation. Further progress is expected, particularly in the manufacturing process for GaN compound semiconductors. Since silicon is reaching its application limits in both power and frequency, GaN and SiC technologies are positioned for predominance in power electronics applications, where their properties meet the requirements for compactness, low weight, high efficiency and high power density. There are still technological challenges, particularly in the areas of cost reduction and overall heat dissipation, which in semiconductors results from conduction and switching losses.



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