Directivity, Mutual Coupling, and Active Element Pattern of Phased Array Antenna

Mutual radiation resistance (MRR) is a real part of mutual impedance (MI) when the current on an antenna is expressed by a real function. Herein, we propose and verify a hypothesis stating that “the primitively estimated array gain with mutual coupling considered under the single-mode current assumption (PEAGMS) corresponds to the array directivity with an isolated element pattern used (ADIEU).” We found that PEAGMS agrees very well with ADIEU. Thus, from an engineering point of view, calculating directivity based on pattern integration is equivalent to considering mutual coupling under a single-mode current assumption. Furthermore, we analyzed the MRR between active element patterns and found that the MRR between active element patterns is smaller than that between isolated element patterns.