Rejection and cross-talk 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’s (X-IFU) Warm Front- End Electronics (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 tens 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 can also measure the power supply rejection ratio. For these purposes, a lock-in amplifier is used in differential mode, especially to extract the small crosstalk signals which are at the same frequency as the input excitation. We discuss the design of the demonstrator model, mitigating cross-talk, and our measurement of the residual coupling between differential channels.