Design of a wideband filtering power divider with good in-band and out-of-band isolations

In this article, a wideband filtering power divider with good in-band and out-of-band isolations is designed based on a hybrid Wilkinson and Gysel structure. To achieve a good in-band response, two additional in-band transmission poles can be introduced by installing the coupled-line structures at each port. By mounting a stepped impedance open stub at the input port, two transmission zeros are generated near the passband to improve the passband skirt. Furthermore, the out-of-band rejection and isolation are achieved by the other two transmission zeros, which are produced by the open stub and the three coupled-line sections mentioned above. Additionally, a good in-band isolation is realized by the isolation resistor between output ports. For the demonstration, a wideband filtering power divider centered at 1.5 GHz with a 56% fractional bandwidth and 20-dB isolation is designed and fabricated. The simulated and measured results are in good agreement with each other.