Description: This proposal is responsive to NASA SBIR Subtopic S11.03: Technologies for Passive Microwave Remote Sensing (SBIR), Scope Title: Components or Methods to Improve Sensitivity, Calibration, or Resolution of Microwave/Millimeter-Wave Radiometers; specifically, the bullet item "Noise sources from G-band up to 1 THz with >6dB ENR (excess noise ratio)." Noise sources serve as calibration references for receiver systems used in radio astronomy and atmospheric remote sensing. The goal is to calibrate out the instabilities of the receiver system, for example, gain fluctuations in low noise amplifiers (LNAs). To achieve this the noise source must have sufficient power, expressed as the excess noise ratio or ENR. Generally, an ENR of about 10dB is sufficient, although greater ENR can enable improved performance for noise injection radiometers (e.g. by requiring reduced coupler factor) and in test and measurement (e.g. overcoming coupling loss to the device under test). The other primary requirement is that the noise source itself must have sufficient stability. VDI has recently demonstrated improved performance above 110 GHz using a new diode Schottky diode design. Specifically, ENR above 10dB up to 220 GHz and useful ENR to 330 GHz have been demonstrated. Through the proposed Phase I research VDI will demonstrate the feasibility of this technology to achieve NASA's stated goal, and to investigate how high in frequency this technology can be extended through Phase II research and development.

Benefits: Remote sensing radiometers play a key role in NASA's investigations of the Earth's atmosphere. This includes weather monitoring and prediction, climate change, heliophysics and tracing of trace constituents for pollution monitoring. Radiometers are also useful for exploring the atmospheres of other planets and moons. These radiometers generally use a diode-based noise source for calibration. However, suitable noise sources are not commercially available above 110 GHz. Through this effort, VDI will develop commercially viable noise sources for NASA applications. This Phase I effort seeks to develop and demonstrate noise sources with 10dB ENR up to 500 GHz. This will include the delivery of two prototype sources for use in NASA programs. This project will also investigate how high in frequency the new noise diodes can be extended through Phase II development, with the goal of achieving useful ENR to at least 1 THz. Beyond science applications, noise sources are also important for commercial test & measurement. For example, VDI Noise Sources are needed to accurately measure the noise figure of amplifiers, mixers and receivers that are being developed for Beyond-5G communications systems. In fact, now that 5G has become a commercial reality, all laboratories that were previously developing components and subsystems for 5G, have now begun working at much higher frequency. Research in the atmospheric window in the WR6.5 and WR3.4 bands is growing quickly, and the US military is strongly supporting the development of new amplifier technologies at 220 GHz and above. Electronics continues to move to higher frequency bands and the development of improved test & measurement is critical to this progress. It is also important to note that SmallSat and CubeSat technologies are enabling the commercial development of weather monitoring instruments in low Earth orbit. These new ventures will also become a substantial commercial market for high frequency noise diodes.