Transponders for synthetic aperture radar (SAR) need to be extremely precise in order to qualify as absolute calibration
references for the increasingly demanding new SAR systems. To guarantee highest accuracy and stability even components
which normally are considered ideal, have to be be taken into account. This paper shows the environmental influence
on the antenna gain and thus on the overall transponder gain, compares two different housing designs and explains why
this particular design has been chosen for the new transponder currently being developed at the DLR
