High performance W-band GaN power amplifiers for cloud Doppler radar arrays

Needs: One of the NASA aerosol-cloud-ecosystems missions is to reduce the uncertainty about climate forcing in aerosol-cloud interactions and ocean ecosystem CO2 uptake in order to provide precise predictions of local climate change, including changes in rainfall. To provide more precise climate predictions, a simultaneous measurement of aerosol and cloud properties is required. However, current space borne radars do not address cloud particle size and phase information, and they do not provide cross-track imaging, limiting the capabilities of observing low-level clouds, mid/high-latitude precipitation and convection. Advances in radar technology are needed. In particular, a cross-track scanning cloud radar that can measure cloud droplet size, glaciation height, and cloud height, with channels at 94GHz (W-band) and possibly 34GHz (Ka-band) should be implemented. Objectives: Conventional radars rely on tube-based high peak power transmitters which are heavy and bulky, requiring high voltage power supplies leading to increased cost and reliability issues. Solid-state power amplifiers can be potentially used to mitigate these challenges. Among the semiconductors (Si, GaAs, InP, GaN) for solid-state power amplifiers, gallium nitride (GaN) devices offer high Johnson’s figure of merit, enabling the high performance in terms of speed and power. Additionally, they are immune to performance degradation at higher temperatures and ionizing radiation in the space environment. We propose to develop high performance W-band GaN power amplifiers for cloud Doppler radar arrays using Sci-I Zeng’s group recently developed high performance GaN high electron mobility transistors (HEMTs), which leverage the superior performance of GaN. Because of the low-cost silicon substrate and its scalability, we choose to develop the power amplifiers with GaN-on-Si HEMT technology. This is based on Zeng’s group’s recently demonstrated GaN-on-Si transistors with record high performance, which has been highlighted by “Semiconductor-Today” and other news media. Co-I Saxena has demonstrated expertise in high-speed CMOS and BiCMOS analog/RF integrated circuit design for fiber optic transmitters and receivers. To realize the goal, we will: (we will: (1) optimize the material epilayer structure by TCAD simulation for enhanced DC and RF performance (Zeng); (2) develop the HEMT device and on-chip passives fabrication process (Zeng); (3) develop amplifiers: build transistor simulation models using Keysight’s Advanced Design System (ADS) software (Zeng); Using the GaN-on-Si HEMT models and on-chip passives and transmission line data, design and layout W-band PA circuits for the targeted spaceborne Radar specifications (Saxena); fabricate PA ICs using the GaN-on-Si process (Zeng); Characterize the fabricated power amplifiers using W-band experimental setup (Saxena and Zeng). Significance: Our proposed work will enable the state-of-the-art GaN-on-Si high electron mobility transistors performances; it will provide high frequency GaN power amplifiers for W-band cloud radar applications with power gain >12dB, peak output power >30dBm. This will enable a radar instrument with high power efficiency, temperature robustness, radiation hardness and reduced size and weight, allowing for the simultaneous measurement of aerosol and cloud properties to provide more precise predictions of local climate change. We expect to bring this technology from TRL1 to TRL4. Successful completion of this work will contribute to the development of Delaware state research capability in high speed electronic devices and IC technology for reduced size, weight and power components of small spacecraft with high bandwidth communications, aligning well to the NASA missions and strengthening STEM education goal. It will help to develop partnerships research centers (i.e. GSFC, etc.) and expand the Delaware research infrastructure, science and technology capabilities.

This is a mature technology (TRL 7+) — the realistic path in is usually NASA's Technology Transfer Program: licensing an existing NASA patent, or a Space Act Agreement to use NASA facilities/expertise directly. NASA also runs a startup licensing program with no upfront fee for companies formed to commercialize a specific NASA technology.

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