Increased access to wireless data has rapidly transformed the way people live and work. Wireless customers now demand access to wireless data from anywhere at any time and they are consuming more bandwidth than ever before. The rapid advancement of AI and the transition to a more automated society will only further this demand, pushing our wireless infrastructure to operate at higher frequencies to support higher data throughput in combination with lower latency. One part of the wireless infrastructure playing a key role in supporting this demand is satellite communications (satcom).
The satcom industry has seen tremendous growth in recent years due to a combination of lower launch costs combined with reduced satellite manufacturing costs. It is expected that 50,000 satellites will be launched over the next decade. The number of ground terminals needed to support these satellites is estimated in the millions and these terminals vary from large gateway terminals to small portable user terminals. The fastest-growing segment of the satellite market is Ka-Band, which uses the 17.3 to 21.2 GHz frequency band for downlink and the 27.5 to 31.0 GHz frequency band for uplink. It is this uplink frequency band and the ground terminal market that Nxbeam supports with its line of high-power Ka-Band MMIC products.
KA-BAND GAN POWER AMPLIFIER PRODUCTS
To support the Ka-Band ground terminal market, Nxbeam offers a full suite of high fidelity power amplifier (PA) MMICs focused on increasing data throughput. As shown in Table 1, the Ka-Band PA MMIC products range from 7 to 40 W of output power, making them suitable for a wide range of ground terminals. Nxbeam entered this market and focused first on the higher-power products to support the gateway market. Building on that success, Nxbeam moved down in power to support smaller ground terminals.
The company’s latest product offering is the NPA2050-QF, which is a 7 W Ka-Band PA in a QFN package. This product was designed specifically for the high volume, low-cost Ka-Band ground terminal market. The challenge with this specific market has been the need for a very low-cost PA. Until now, it has been a challenge for GaN to achieve the necessary price point, but by implementing a new innovative design approach, Nxbeam has been able to significantly reduce the cost for this power level.
Figure 1 NPA2050-QF measured output power versus input power.
Figure 2 NPA2050-QF measured IM3 versus total output power.
Figure 3 NPA2050-QF measured spectral regrowth versus total output power.
The cost of a GaN PA is directly proportional to the GaN semiconductor area of the MMIC. By decreasing this area, more chips can be fabricated from one wafer, which decreases the overall product cost. Nxbeam has used an innovative design approach to reduce the GaN semiconductor area of the NPA2050-QF by more than 50 percent. This dramatic decrease in the semiconductor area has enabled the design to achieve the desired price points.
PA DESIGN AND PERFORMANCE
Like all of Nxbeam’s Ka-Band PA products, the NPA2050-QF offers the same high performance with high reliability. As with other Nxbeam MMIC amplifiers, it is a three-stage design with the capability to control the quiescent current of each stage independently. This has proven to be essential to many customers as they use this feature to tailor the linear power performance to their specific needs through bias control.
The NPA2050-QF operates from 27.5 to 31.0 GHz and provides 7 W of saturated output power, 23 dB of linear gain and 25 percent power-added efficiency. Figure 1 shows the output power versus input power curves. The bias for all measurement results shown was 26 V and 525 mA quiescent current with all gates at the same voltage. For ground terminal use, the fidelity of the PA is critical, so its linear power capability is more important than pure saturated output power.
Figure 2 shows the measured IM3 curves for this specific bias with a frequency spacing of 10 MHz. As seen in this figure, an output power of 4 W can be achieved at an IM3 level of -20 dBc. This is just one set of IM3 curves and by adjusting the bias for each stage, linear power performance can be tailored for specific use cases. Figure 3 shows the linear power performance in terms of spectral regrowth for a QPSK modulation at 10 MSPS and alpha = 0.2.
FUTURE WIRELESS SYSTEMS
As the world advances toward a more AI-driven automated society, access to wireless data from anywhere at any time will require wireless infrastructure capable of higher data rates and satellites along with their supporting ground terminals, will play a key role. There is already work at higher frequencies beyond Ka-Band, like V-Band and E-Band, to support future wireless data needs. While Nxbeam is currently supporting the Ka-Band ground terminal market, the company also supports these future bands and will be continuously releasing new products to support them.
Nxbeam Inc.
Los Alamitos, Calif.
www.nxbeam.com