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Reducing the interference between ultra wideband (UWB) and other existing signals is an important issue in UWB systems and devices design. In this study, we propose a 2-stage 1 to 4 power divider (PD) which enables the suppression of 802.11a standard's frequency (5.2GHz) by means of a symmetric spiral defected ground structure (DGS) in the first stage. To avoid extra loose of UWB signal information, the notch shouldn't be very wide. So, the quality factor (Q) of involved resonator is an important criterion. The Q can be controlled by line width. The analysis proves that a 50-100-50 ohm transformation in PD structure provides the required line widths for a high Q factor. This configuration also eliminates the matching loop needed in the first PD stage and consequently results a smaller and simpler design. A three-section 1 to 2 100-50Ω PD forms the second cascading stage. The constructed PD with a small size of 6.2×6.5cm2 operates well in the designated frequency band with good matching and isolation. The measured Q factor is 14.857 which provides more than 30 dB suppression.