Noise sources for internal calibration of millimeter-wave radiometers

We have developed noise sources at 90 GHz, 130 GHz and 168 GHz each using a custom-designed beam-lead noise diode from M-Pulse Microwave Inc. These noise sources measure a high excess noise ratio (ENR) of 17 dB, 9.6 dB and 6 dB at 90 GHz, 130 GHz and 168 GHz, respectively and are to be used for internal calibration in the high-frequency millimeter-wave nadir-viewing radiometers, which are expected to provide increased spatial resolution of wet-tropospheric path delay correction for coastal regions and inland water. The noise sources meet the ENR, radiometric stability, mass and size requirements, which enables us to achieve internal calibration for the high-frequency millimeter-wave channels. Furthermore, we have developed a novel approach that utilizes a MMIC LNA as a noise source in the 168 GHz frequency band. Both of these noise sources have demonstrated excellent stability of 0.07% per hour. This translates to < 0.1K per hour T
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stability for cold ocean scene.