In this paper, an analytical framework is presented for device detection in an impulse radio (IR) ultra-wide bandwidth (UWB) system and its performance analysis is carried out. The Neyman– Pearson (NP) criteria is employed for this device-free detection. Different from the frequency-based approaches, the proposed detection method utilizes time domain concepts. The characteristic function (CF) is utilized to measure the moments of the presence and absence of the device. Furthermore, this method is easily extendable to existing device-free and device-based techniques. This method can also be applied to different pulse-based UWB systems which use different modulation schemes compared to IR-UWB. In addition, the proposed method does not require training to measure or calibrate the system operating parameters. From the simulation results, it is observed that an optimal threshold can be chosen to improve the ROC for UWB system. It is shown that the probability of false alarm, P FA, has an inverse relationship with the detection threshold and frame length. Particularly, to maintain P FA < 10 −5 for a frame length of 300 ns, it is required that the threshold should be greater than 2.2. It is also shown that for a fix P FA, the probability of detection P D increases with an increase in interference-to-noise ratio (INR). Furthermore, P D approaches 1 for INR > −2 dB even for a very low P FA i.e., P FA = 1 × 10 −7. It is also shown that a 2 times increase in the interference energy results in a 3 dB improvement in INR for a fixed P FA = 0.1 and P D = 0.5. Finally, the derived performance expressions are corroborated through simulation.