Rejection and crosstalk measurements on the X-IFU warm front-end readout using lock-in amplifier up to 50 MHz

In the context of the ATHENA X-ray space mission, the X-ray integral field unit (X-IFU) warm front-end electronic (WFEE) is a multichannel differential readout sub-system. As part of the verification of the performance several measurements are carried out, initially on the demonstrator model of X-IFU’s WFEE, and later for the production models. The transfer function from the 8 channels included in a demonstrator are measured, for excitation from a few 10s of Hz up to 50 MHz. Over the same frequency range, the inter-channel coupling and cross-talk are measured at a level below -80 dB. We also measure the power supply rejection ratio. For these purposes, a lock-in amplifier is used in differential mode, especially to extract the small cross-talk signals which are at the same frequency as the input excitation. We discuss the design of the demonstrator model mitigating cross-talk and the way we measure in differential the residual channels coupling.