Directional coupler with high isolation bandwidth using electrical balance

A directional coupler using edge coupled lines is designed and fabricated on a two-layer PCB with isolation being achieved through electrical balance. Measured results show 4dB coupling and 34dB isolation at a frequency of 2.5GHz with 16% matching bandwidth (-10dB). Isolation varies between 31dB to 36dB in the 2.3GHz to 3GHz frequency range.