Due to its wide bandwidth and high data rate, the Ka-band opens up new applications, which include 5G mobile communications, fixed wireless access (FWA), low earth orbit (LEO) satellites as well as electronic warfare. Consequently, Ka-band receivers can be prone to interference, which demands highly linear and robust low noise amplifiers (LNAs) in today’s Ka-band systems.
Recently, we from our Joint Lab BTU-CS – FBH Microwave have presented a highly robust 28 - 32 GHz GaN-based LNA. We designed the 2-stage LNA using a 150 nm gate length and 4 x 50 μm gate width GaN HEMT on semi-insulating SiC substrate. The fabricated LNA with a chip area of 2.9 x 1.7 mm2 is displayed in Fig. 1. The measured small-signal gain and noise figure of two LNA samples are shown in Fig. 2 (in red).
Stress test results of the three LNA samples are shown in Fig. 3, indicating one burnt-out LNA after 34.3 dBm and two surviving LNAs up to the highest applied input power of 34.4 dBm at 30 GHz CW. The surviving LNAs were measured after roughly 2 hours, showing a positive threshold shift and a degradation of the small-signal gain and noise figure only by 0.2 - 0.6 dB and 0.1 - 0.2 dB, respectively (Fig. 2, in blue). The measured small-signal gain and noise figure (Fig. 2, in green) after readjusting the bias current lie close to the pre-stress values, and we observed no major change, thus demonstrating undamaged LNAs.
Therefore, this work reports the survivability of FBH GaN-based LNAs at high stress conditions in Ka-band receivers. It further establishes the FBH GaN HEMT technology in the mm-wave range. Compared to GaAs LNAs, the high ruggedness of GaN LNAs gives the opportunity to design receivers without input protection circuit, improving the receiver noise figure. Moreover, a compact and cost-effective single-chip integrated RF frontend based on GaN HEMT technology can be realized, thus facilitating applications like massive MIMO.
This work is funded by the German Ministry of Education and Research (BMBF) within the program ForMikro-LeitBAN, grant no. 16ES1112, and under the project reference 16FMD02 (Forschungsfabrik Mikroelektronik Deutschland).
S. Haque, C. Andrei, H. Yazdani and M. Rudolph, “On the Survivability of a 28–32GHz GaN Low Noise Amplifier,” 18th European Microwave Integrated Circuits Conference (EuMIC), Berlin, Germany, 2023.