Calibration procedure, linearity tests and error analysis of microwave Dicke-type radiometers

The design, calibration, linearity tests, and error analysis of a multifrequency radiometer system are presented. The system consists of two L-band radiometers (with center frequencies of 0.96 GHz and 1.65 GHz) and one X-band radiometer (with center frequency of 9.4 GHz) for remote sensing applications such as soil moisture estimation and water salinity measurement. The radiometers were designed around the common concept of a Dicke-type superheterodyne radiometer with a built-in subsystem for internal calibration and unified low-frequency units. Special care is taken to ensure exact numerical correspondence between the values of the input and output signals. A formula for the absolute error estimation is obtained. (AIAA)