Wideband out-of-phase power divider using tightly coupled lines and microstrip to slotline transitions

A broadband out-of-phase power divider in a compact structure employing a microstrip technology is presented. The proposed power divider consists of a T-junction of microstrip to slotline transition at the input ports along with a pair of tightly coupled microstrip lines at the two output ports. The main features of the proposed device are the employment of a dumbbell-shaped slot terminated with a chip resistor under the tightly coupled lines to improve the isolation between the output ports and shunt open-ended stubs at the output ports to improve their impedance matching. The overall size of the structure is 30 x 60 mm using the substrate Rogers RO4003C with a dielectric constant of 3.38 and thickness of 0.4 mm. The simulated and experimental results of the developed device show wide bandwidths (120% fractional bandwidth) with isolation >15 dB across the investigated band 1-4 GHz. In addition, the output ports are out-of-phase with <1 degrees phase imbalance across the whole frequency band.