A noise source is an enabling technology for passive millimeter-wave remote sensing applications such as atmospheric sounding, and precipitation and ice cloud measurements. NASA Goddard Space Flight Center has developed a packaged noise source that will allow calibration of the front end at the sensing frequency. This capability will eliminate or reduce the requirement of a clear view to cold space, which will reduce the mass and complexity as well as the total cost of the system.
A 160-210 GHz chip-waveguide noise source was designed on quartz implemented into waveguide housing. This noise source circuit consists of commercial millimeter-wave Schottky diodes, a low-pass filter for biasing the diodes with no high-frequency interference, a back-short designed at the center frequency of 183 GHz with vias, and a longitudinal chip/waveguide probe. The back-short is designed with multiple vias to aid with heat sinking the diodes; this feature allows continuous biasing rather than pulsing the circuit. The packaged noise source generates greater than ~10 ENR at 200 GHz.