The FDM readout for the LSPE/SWIPE TES bolometers

We present the design and experimental demonstration of a 16-channel frequency domain multiplexing (FDM) readout for transition-edge sensor (TES) bolometers. This readout system is going to be implemented on the LSPE/SWIPE balloon-borne experiment, whose goal is to detect the polarization of cosmic microwave background (CMB) at large angular scales and whose launch is scheduled for December 2019. We describe the fabrication process of the Niobium superconducting inductors and the qualification tests performed in our 300 mK cryogenic facility in INFN Pisa of the boomerang shaped PCBs hosting the LC chains and the gradiometric SQUIDs, which are going to be mounted on the back of the SWIPE focal planes. The development of the warm readout electronics is presented, together with the firmware for the generation and readout of the biasing frequency comb.