Eigenvalue mode confirmation in a mutually coupled active antenna chain array

Arrays of coupled active antenna oscillators can be used for power-combining at microwave and millimetre-wave frequencies. It is known that the relative phase angle between active antenna oscillators placed in an array and hence their far-field radiation pattern can have certain discrete values depending on the separation distance between elements. Thus in order to characterise an active array an accurate method of evaluating the coupling between oscillators and a knowledge of the available modes that exist within the array are required. In this paper the available modes for an array of mutually coupled active antenna elements are evaluated by examination of the eigenvectors of the impedance matrix of the passive element components in the active array. Time domain numerical simulations are performed and the resulting predictions compared to those obtained by experiment and by the eigenvalue approach.