Feed network for antenna decoupling

A decoupling network for improving the isolation between two highly coupled antennas is proposed. In this method the input signals are combined linearly so that the mutual coupling between the ports becomes zero. The scattering matrix of the network is found using a mathematical procedure and has been demonstrated in this paper for a previously developed integrated wide/narrow band antenna. For this antenna the network can be realised using a rat race coupler and phase shift elements. Measurement results show that the mutual coupling has improved by 30 dB.