Compact and wideband modified wilkinson power dividers

Abstract

A Wilkinson power divider has ideal transmission characteristics and it enables easy realization in planar transmission line technology. However, the conventional Wilkinson power divider features a large component footprint because of its quarter-wavelength line components and narrow bandwidth. In this paper, two modified Wilkinson power divider are proposed in order to achieve size reduction and wide bandwidth. The first structure presents Wilkinson power divider using compact folded step impedance transmission lines (FSITL) rather than the uniform microstrip line design for operating center frequency of 3 GHz. While the second structure presents the FSITL with delta-stub for 2.4 GHz. The proposed folded microstrip line structure is capable of reducing the size of the power divider circuit. The impedance ratio of SITLs is taken into account as the total electrical length of the lines for every wavelength 01 and 02 in order to enhance size reduction to the optimum. The study managed to get an overall dimension of 15 mm × 9.5 mm for the first proposed design achieving a reduction of 75.6 % and bandwidth of 4 GHz. For the second proposed structure, the size was 15 mm × 15 mm with a reduction of 56 %. The proposed structures provided an extra 80 % fractional bandwidth based on the −15 dB return loss as a reference. The proposed power divider used RT/duroid 5880 substrate with 0.38 mm thickness. Simulation and measurement results indicated that the modified power divider showed equal power division, good phase balance, high isolation between output ports, and good return loss better than −15 dB covering the operating frequency range.