A band-notched ultra-wideband 1 to 4 wilkinson power divider using symmetric defected ground structure

In this paper, we propose a novel ultra-wideband Wilkinson power divider with symmetric defected ground structure (DGS) having frequency band-notch characteristic. The Wilkinson power divider was invented in 1960 and has wide applications in microwave circuits and antenna feeds. But it has a narrow bandwidth. Several schemes have been devised to increase its bandwidth. The main proposal used series connection of several sections having considerably increased bandwidth and high isolation between outputs for equal power divider. We use connection of three sections to obtain the UWB Wilkinson power divider. It is well known that the DGS of the microstrip line is implemented by making artificial defect on the ground and the ground defect provides a resonance property in transfer characteristic. In the microstrip line, DGS on the ground plane provides band rejection characteristic at some resonance frequency corresponding to the size of defect on the ground. In this paper, band-notch characteristic is achieved by inserting a symmetric spiral DGS under the microstrip line of the power divider. Experimental results of the constructed prototype are presented.