Investigating adverse low-frequency effects of log-periodic dipole antenna resonant radiation

Log-periodic dipole antennas provide a series of regular resonances logarithmically spaced over the operating frequency band, but these are disturbed by mutual coupling in closely spaced arrays. We examine how such resonant features on the low-frequency range of a certain log-periodic design, the SKALA4.1, depend on the antenna reflection coefficient. We also propose a way of shifting the electric field peak frequency of these resonances and reversing the reflection coefficient by loading some of the antenna dipoles. The analysis is focused on one antenna, while mutual coupling of two antennas could potentially benefit from controlling such characteristics.