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

The configuration and design method of a compact broadband out of phase power divider employing a microstrip/slot technology is presented. To make it easy for integration with other devices, the proposed device employs a single substrate. A T-junction of microstrip-slotline-microstrip transitions at the input port and coupled microstrip lines with shunt open-ended stubs at the output ports of the top layer are used to achieve an out of phase signal division over a large frequency range. Moreover, a proper chip resistor is employed across a dumbbell-shaped slot underneath the coupled lines to improve the isolation between the output ports. The overall size of the structure is 0.18 λ_g × 0.31 λ_g, where λ_g is the guided wavelength at the lowest operating frequency. Following a proper theoretical method based on the even-odd mode approach and slotline design guidelines, the proposed structure is designed to operate across the band 1-4 GHz. The achieved simulated results show 123% fractional bandwidth assuming 15 dB of isolation as the reference. The proposed device has equal power division between the two output ports with less than 0.2 dB amplitude imbalance and less than 1° phase imbalance across the whole band.