Equivalent circuit model for closely coupled symmetrical two-port MIMO antennas in small volume

This paper proposes an equivalent circuit model for handset electrically small symmetrical two-port MIMO antennas. In limited volume of mobile devices only exploitation of orthogonal modes of radiation can lead to low coupling and low correlation between antennas. This paper explains the principle of operation for small MIMO antennas by means of common and differential mode excitation. A circuit model is introduced, validated based on full-wave simulations of an antenna prototype and used to aid MIMO antenna design for PCS band (1850-1990 MHz).