Broadband, Small-Aperture Direction-Finding Array With Azimuth and Elevation Estimation Capability

A broadband (VHF-UHF), compact antenna array capable of estimating the elevation and azimuth angles of arrival of an electromagnetic wave is presented. Small-aperture direction-finding (DF) arrays are widely used at lower frequency bands (e.g., HF and VHF bands) where the electromagnetic wavelength is large and the physical size needed to accommodate the array is generally small. To design the proposed small-aperture DF array, we examined different array topologies that provide elevation and azimuth estimation capabilities and that are immune to errors caused by cross polarization. All of these potential candidates occupy the same volume of 14 × 14 × 5.5 cm
³
corresponding to a maximum linear dimension of 19 cm. Subsequently, we adopted the topology that provides the lowest Cramer-Rao bound (CRB). The topology of this array was further optimized to efficiently utilize an available volume, and its DF performance was characterized over a wide frequency range from 30 to 2000 MHz using computer simulations. A prototype of the array was also fabricated and characterized using field tests at a number of discrete frequencies within this band. The measurement results show very good agreement with simulations and validate the DF capabilities and the expected accuracy levels predicted by the theoretical analyses.