Power balance analysis of an infinite equispaced linear array composed of two alternating types of elements

This paper discusses a λ/4 spaced infinite linear antenna array consisting of identical two-element cells. Elements inside each cell are not necessarily the same. Minimal physical value of inter-element coupling is derived from per-cell power balance considerations for generic elements radiation patterns. It is shown that a lower limit on a coupling between the elements exists as a function of their respective radiation properties, reaching -6dB for an important special case of identical well-matched antennas. Conclusions regarding performance limitations of large interleaved TX/RX arrays are derived from this result.