Performance Verification of a Multimodal Interferometric DOA-Estimation Antenna

In our previous letter, a novel method of estimating the direction of arrival (DOA) of received signals was introduced. The method combines interferometry and multimodal principles to find the DOA in both elevation and azimuth. We also presented a new wideband waveguide-fed DOA-estimation (DOAE) antenna based on the new method. That antenna is simpler in its hardware than an earlier DOA-antenna published in 1957, and it has an added capability of DOAE in elevation. This letter describes a direction-finding (DF) test antenna that was designed, fabricated, and measured in order to verify the new DOAE method. The antenna´s measured results indeed validate the new DOAE method. Both azimuth and elevation DOAs of received signals were extracted correctly. As in our previous letter, the system herein consists of two subantennas positioned one above the other. The first is a biconical horn antenna feeding a thick coaxial-waveguide loaded by four feed-probes. The probes are connected to a printed RF-combiner comprising two output ports corresponding to ±1-order circular phase modes (CPMs). The second antenna is a vertical dipole outputting a signal that serves as a reference for interferometry in elevation, as well as a reference zero-order CPM for azimuth estimation.