In this contribution, the problem of the synchronization for ultra wideband impulse radio (UWB-IR) systems, through the adoption of a multi-antenna platform working on multipath faded channels, is afforded. In this regard, we propose a novel UWB-IR synchronizer devoted to jointly estimate (according to the maximum likelihood (ML) criterium) the arrival times and their (Poisson distributed) number, composing a typical UWB-IR multipath faded channel. Such estimate is effected without any knowledge on the value of the channel paths (noncoherent ML synchronizer). The architecture of such synchronizer is based on a single-input multiple-output (SIMO) platform, instead of a multiple-input multiple-output MIMO one, according to a previous result in the literature. Related performance of this joint ML estimation is expressed in closed via the Cramer-Rao bound (CRB) and is tested by simulations, under acquisition and tracking conditions.