A design for a six-port, high phase and amplitude balance, stripline coupler is presented. Both the predicted and the measured performance of a hardware prototype show phase and amplitude balance better than 0.2 dB and 0.9 at the design frequency of 2.46 GHz when fabricated on an FR-4 substrate.Introduction: During the course of our investigations into phased array calibration the requirement arose for a six-port directional coupler with high coupled-port phase and amplitude balance. This design is based on edge-coupled striplines which have varied little since their conception and characterisation [1,2]. Since then other coupler configurations have been proposed [3,4]