Planck-LFI CPV: front end amplifier bias HYM_TUNING

Abstract

This document describes the results from the Hyper-matrix tuning activities. The Tuning is aimed at finding the optimal bias setting for the LNAs exploring the bias space changing simultaneously the four Vg bias (4-dimensional hypermatrix) powering each radiometer. The hypermatrixes come from the pre-tuning results, drawing for each of the 22 radiometers the bias space around the bias quadruplets expected to produce the best performance ( noise temperature and Isolation) . Since Isolation could not intrinsically be measured with the pre-tuning method, Isolation was measured for the first time only at the end of the HYM–TUNING. In addition, for a subset (15 bias quadruplets for each radiometer) of values expected, from pre-tuning results, to provide the best performance, also the drain voltage is tuned following a matrix scheme, changing the Vd on both the ACAs of the same radiometer. Hence, for this subset of values, the tuning is performed over a six-dimensional hyper space.