Planck low frequency instrument (LFI) 70 GHz receiver modules

Elegant Breadboard Model of an ultra low noise 70 GHz continuous comparator total power radiometer with 20 % frequency bandwidth has been built for the ESA Planck Mission. The receiver consists of two separate modules: Front End Module (FEM) and Back-End Module (BEM). The FEM is cooled to 20 K physical temperature while the BEM is operating at room temperature. This continuous comparison receiver is based on use of a structure of similar to a balanced amplifier in the FEM. The FEM LNAs are based on state-of-the-art InP HEMTs processed at NGST (ex. TRW). In addition to this, phase shifters are placed between the FEM hybrids to facilitate DPDT-switching capability. The switching capability is used to remove 1/f noise at the Back-End Module (BEM) amplifier chain. The switching rate is 1 kHz. ehkä More than 35 dB gain and an average 25 K noise temperature was measured at 20 K physical temperature in the Front-End Module (FEM). A 20 dB isolation between the signal and reference channel has been obtained at 20 K physical temperature. A Back-End Module (BEM) having 20 dB RF gain and 20 dB post detection voltage gain has also been built and measured with the FEM.