A new wideband filtering power divider with ultra-wide stopband using microstrip/slotline transitions

In this article, a wideband filtering power divider (FPD) is proposed based on a new design scheme originating from the microstrip/slotline broadside-coupled structure. It is simply composed of one microstrip T-junction and two transmission lines on the top layer, and a pair of U-shape slotline resonators as well as one isolation resistor-loaded slotline stub with a circular slot terminal in the ground plane. The presented FPD stands out by much wider bandwidth, improved performance, and simple design layout. For verification, one prototype FPD is designed and fabricated with a center frequency of 4.0 GHz and a fractional bandwidth of 77.1%. Simulated results coincide well with the measured ones. Results indicate that the new wideband FPD exhibits not only a simple layout without additional loading elements, but also nice port-to-port isolation over a whole wide frequency band range, good return losses, and 20-dB harmonic suppression up to (2.5 f(0)).