Compact front-end prototype for next generation RFI-rejecting polarimetric L-band radiometer

Realizing the need for lower noise figure and smaller physical size in todays highly sensitive radiometers, this paper presents a new compact analog front-end (AFE) for use with the existing L-band (1400-1427 MHz) radiometer designed and operated by the Technical University of Denmark. Using sub-harmonic sampling to sample directly at the RF-frequency, this radiometer obtains a fully polarimetric response and enables detection and removal of radio frequency interference (RFI). A more compact AFE will enable various desired features, as for example the ability to use the front-end with antenna arrays needing one receiver per antenna (synthetic aperture radiometer, SARad), reduced weight for airborne missions and an easy temperature stabilization, i.e. improved instrument stability. The new front-end possesses an improved system noise temperature of only 76 K (roughly 40 K improvement) measured at an AFE physical temperature of 44°C, thus making the radiometer even more sensitive.