Stadler, M. Keil, B. Marcellini, F. Marinkovic, G. JACoW Geneva, Switzerland 978-3-95450-192-2 10.18429/JACoW-IBIC2017-TUPCF18 English 255-258 TUPCF18 ion pick-up FEL undulator electron Contribution to a conference proceedings 2018 2018-03 https://doi.org/10.18429/JACoW-IBIC2017-TUPCF18 http://jacow.org/ibic2017/papers/tupcf18.pdf In 10/2016, PSI started the beam commissioning of Aramis, the hard X-ray undulator line of the SwissFEL free electron laser. The injector, linac and transfer line BPMs have 3.3 GHz low-Q cavity BPMs to support 2-bunch operation with 28ns bunch spacing. In contrast, Aramis as well as the future 2nd soft X-ray undulator line called "Athos" are eqipped with 4.9 GHz high-Q cavity BPMs, since the undulators will only be operated with single bunches by means of a fast beam distribution kicker system. The undulator BPM system uses 4.9GHz double-resonator pickups having a nominal loaded-Q of 1000. The associated front-end electronics applies single-stage analog downconversion to a 135 MHz IF frequency, subsampling ADC and digital quadrature downconversion. A detailed description of the BPM pickup and front-end design and signal processing will be given. Laboratory test and calibration methods and results of pickups and electronics will be compared with first beam measurements.