Infinitesimal Dipole Modeling from Sparse Far-field Patterns for Predicting Electromagnetic Characteristics of Unknown Antennas

The identification of unknown antennas and analysis of electromagnetic wave vulnerability are important for effective attacks and/or protection in high-power electromagnetics (HPEM). Using electromagnetic clues, antenna modeling becomes possible, and its electromagnetic properties can be analyzed by predicting area-wide radiation patterns. To model an antenna, an infinitesimal dipole modeling (IDM) technique, utilizing clues from sparse far-field patterns, was used in the present study. The IDM approach obtained the equivalent ID for the antenna configuration current using Green's function. The sparse far-field pattern was determined for a movement trajectory, using air reconnaissance. Random far-field data acquisition paths were considered cumulatively in the 1-10 range in this case. The approach also used external exposure information about the antenna, such as the operating frequency and size. For simulations and measurements, a ridged-horn antenna operating at 2.4 GHz was used. The overall radiation pattern reconstructed using the IDM approach was correlated at 0.78 when one path was considered in the simulations. As the considered paths were accumulated, the correlation tended to increase, with the correlation for 10 paths exceeding 0.98. The estimated radiation pattern characteristics of antennas can be utilized for communication reception characteristics and/or electromagnetic wave vulnerability analysis.