In this paper, a new printed ultra-wideband (UWB) power divider with notched band using square ring multiple-mode resonator (SRMMR) is presented. The characteristics of the proposed SRMMR are investigated by using even- and odd-mode analysis. Then, the initial UWB performance is achieved by introducing SRMMR to the basic Wilkinson power divider. Finally, a pair of parallel coupled lines is embedded into the SRMMR to achieve a desired notched band inside the UWB passband. The central frequency and the bandwidth of the notched band can be easily controlled by the electrical length and coupling coefficient of the coupled lines. To validate the design concept, a novel printed UWB power divider with notched band centered at frequencies of 5.8 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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