A 7x7 elements Q-band feed-horn array for the LSPE-STRIP experiment

We present the design, manufacturing and performance verification of the Q band feed-horn array to be employed in the focal plane of the STRatospheric Italian Polarimeter (STRIP) instrument, on board the Large Scale Polarization Explorer (LSPE) balloon experiment, funded by the Italian Space Agency (ASI). LSPE will measure the polarization of the Cosmic Microwave Background (CMB) looking for the B-modes on large angular scales. The 49 feed-horns of the STRIP instrument are arranged in seven hexagonal modules of seven elements each, built in platelets technique. Measured beam patterns of each horn are highly consistent with each other and in very good agreement with simulations, at the level of fractions of a dB up to the first side-lobe. Measured crosspolarization and return loss levels are better than -37 dB and 35 dB, respectively, on a 20% bandwidth.