Three-octave band in-phase power divider using loosely coupled microstrip lines and microstrip to slotline transitions

A planar microwave in-phase power divider operating over three-octave frequency band is presented. The proposed device is composed of two main parts. The first one is a pair of microstrip-slotline-microstrip transitions introduced to match the impedances at the input port. The second one is a pair of loosely coupled microstrip lines with two isolation resistors to provide improved isolation performance at the output ports over a wide range of frequency band. The device has a compact area of 40 x 40 mm using the substrate RO4003C (dielectric constant of 3.38 and thickness of 0.406 mm). The simulated and experimental results of the developed device show three-octave bandwidths (155% fractional bandwidth) with isolation >15 dB across the investigated band from 1 to 8 GHz. In addition, the device provides a <+/- 2 degrees differential phase between the in-phase output ports across the whole frequency band.