Calibration switch of the spaceborne microwave radiometer

When the spaceborne microwave radiometer operates in orbit, the microwave switch allows for three different input sources: the observation antenna, the calibration antenna, and the matched load at ambient temperature. When one port of the switch is connected, the sources from the other two unconnected ports will leaks into the connected port if their isolations are not great enough. In this paper, the contributions from the unconnected ports to the connected port are analyzed and how to choose the isolation of the switch is considered.