This paper proposes a noncoherent Rake receiver structure in M-ary code shift keying (CSK) direct sequence ultra-wideband (DS-UWB) communication systems. The proposed Rake receiver contains a selection combining of in-phase and quadrature components of each resolvable path at the matched filter output. Simulation results show that the proposed Rake receiver demonstrates superior error rate performance comparing with conventional noncoherent Rake receiver.