In this paper, a novel ultra-wideband (UWB) power divider with dual notched bands using square ring multiple-mode resonators (SRMMRs) is presented. The characteristics of the proposed SRMMRs are investigated by using even- and odd-mode analysis. Then, the initial UWB performance is achieved by introducing SRMMRs to the basic Wilkinson power divider. Finally, two desired notched bands inside the UWB passband are achieved by embedding a pair of coupled dual-mode stepped impedance resonators (DMSIRs) into the SRMMRs. The central frequencies of the notched bands can be easily controlled by the electrical length of the DMSIRs. To validate the design concept, a novel compact UWB power divider with dual notched bands centered at frequencies of 5.8 GHz and 8.0 GHz is designed and measured. The simulated and measured results indicate that it has a low insertion loss and good return loss performance at all the three ports, and a high isolation between the two output ports across the UWB bandwidth from 3.1 to 10.6 GHz with a small size of 0.46λg×0.69λg, where λg is the guided wavelength at 6.85 GHz.
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