Planck satellite 70 GHz receiver noise tests

The LFI (Low Frequency Instruments) receivers in the coming Planck satellite are of continuous comparison type and use low noise amplifiers based on high electron mobility transistors manufactured from indium phosphide substrate (INP-HEMT-MMIC-LNAs). This article describes the 1/f-noise tests and the associated test system for the 70 GHz demonstrator receiver, which can either use single or dual channel phase switcher methods. The 1/f knee frequency is shown to depend on the calculation method of the r-value. A minimum 1/f knee frequency around 10 mHz has been achieved with full two channel foxtrot and individually adopted r-values for each phase states while a straightforward single phase technology cannot go below 40 mHz.