A Three-Element Biomimetic Antenna Array With an Electrically Small Triangular Lattice

We present a three-element biomimetic antenna array (BMAA) with an electrically small triangular lattice. The proposed array consists of three identical quarter-wavelength-long monopoles each positioned at a corner of an equilateral triangle whose side length is 0.05λ
₀
, where λ
₀
is the free-space wavelength. Using a triangular lattice allows for maximizing the phase sensitivity of the array over a 360° angular range. Moreover, it will allow for resolving ambiguities when such BMAAs are used in small-aperture direction finding systems. The three strongly coupled antennas are connected to an external coupling network with three inputs and three outputs. This network augments the mutual coupling between the strongly coupled antennas and is designed to maximize the output phase difference between each two antenna elements without sacrificing the output power level of the array compared with a conventional array occupying the same aperture. A modal analysis technique is also presented and used to design a prototype of the proposed array operating at 600 MHz. This prototype was fabricated and experimentally characterized. Measurement results are shown to be in very good agreement with theory.