This paper presents and compares the parametric modeling of several types of antennas designed for IR (Impulse Radio) and MB-OFDM (Multi-Band Orthogonal Frequency Division Multiplexing) UWB systems. Parametric models, based on the singularity expansion method, are computed in order to model the transfer functions and the impulse responses of antennas. Thus, the complexity and the accuracy of time/frequency models of diverse UWB antennas are analyzed.