This paper presents a study about the design of an equally frequency limited set of orthogonal pulses, adequate for an Impulse Radio (IR) Ultra Wideband (UWB) communication system employing Pulse Shape Modulation (PSM). UWB systems have to face many spectrum restrictions like avoiding interference to existing systems or comply with spectrum mask regulations like the one emitted by the Federal Communications Commission (FCC). Then, UWB systems have to restrict their bandwidth and maximize its usage efficiency. The proposed set of pulses meets such requirements and provides additional robustness when interference to narrowband systems should be avoided. © 2004 IEEE.