First Demonstration of Distributed Amplifier MMICs With More Than 300-GHz Bandwidth

This article reports on the first demonstration of distributed amplifier monolithic microwave integrated circuits (MMICs) with a bandwidth (BW) of more than 300 GHz. The three presented circuits utilize a uniform traveling-wave amplifier topology with six, eight, and ten unit cells, respectively. In this article, the impact of the connection between the gate line and the transistors on the achievable performance is investigated. It is demonstrated that a short connection clearly provides a more favorable combination of BW, input matching, and losses on the gate line. Thus, it is possible to extend the BW beyond 300 GHz while utilizing transistors with a gate width of 2×10 μm. The MMICs are fabricated in a 35-nm gate-length InGaAs metamorphic high-electron-mobility transistor technology. The MMIC with six unit cells exhibits a noise figure (NF) between 3.5 and 8.2 dB for a noise-optimized bias from 1 GHz up to the measurement limit of 308 GHz. The MMIC with ten unit cells achieves a minimum NF of 2 dB for frequencies of around 50 GHz and stays below 10 dB for the entire band. Furthermore, for a power-optimized bias, the same circuit generates an output power between 8.7 and 14.8 dBm for a frequency range from 1 to 250 GHz.