This article discusses the ability to improve the resolution of range and azimuth angle measurements by an interferometric localization system used to locate beacons within its line of sight (LoS) by exploiting stepped frequency signals Impulse Radio - Ultra WideBand (IR-UWB) centered on 2 frequencies. This improvement does not require increasing the frequency bandwidth used. This solution uses a phase correlation (PC) method, usually applied to continuous wave (CW) signals, adapted to Ultra WideBand (UWB) pulse signals. The results obtained are compared with those computed by a classical method of energy detection (ED) by exploiting the same frequency band.