Azimuth Angle Estimation for a Reduced Radiation Region Formed by a Metaspiral Antenna

A two-arm metaspiral antenna is presented, where the feeding voltage sources are expressed using excitation amplitude r and deviation angle \delta . This excitation is decomposed into the odd mode and even mode components. The odd mode component forms a circularly polarized (CP) axial beam and the even mode component forms a CP conical beam, whose maximum intensity is off the antenna axis. Superimposing the conical beam onto the axial beam forms a reduced radiation region in the elevation plane. The reduced radiation region is used for minimizing transmission in a particular \phi _{\mathrm {FBD}} direction or the rejection of interference signals from the \phi _{\mathrm {FBD}} direction. This paper presents a formula that estimates the azimuth angle of the reduced radiation region. The formula features the excitation mode ratio, {m} , and the mode phase difference, \Delta \Phi . The formulated azimuth angle is validated by showing good agreement with the simulated azimuth angle obtained by searching for a null over the 3D radiation pattern. The formula is simple and hence supersedes the time-consuming 3D null search.