Nikolaev V. A., Timasheva T. G.

An inclined distributing feeder is used in symmetric ultrawideband logoperiodic vibrator antennas applied for surface wave excitation to stabilize their phase center position and radiation pattern in all frequency range. Since vibrators in antennas with inclined feeder are vertical, they are non-orthogonal to the distributing feeder and induce parasitic currents running along both feeder wires and exciting parasitic synphase wave. As a result, the feeder begins to radiate that worsens external characteristics of the antenna and its matching. That is why it is interesting to study conditions of parasitic synphase wave appearance and its influence on radioengineering characteristics: matching, gain factor, and radiation pattern. The problem is solved by numerical modeling of an antenna. A logoperiodic vibrator antenna with T-shapped shortened vibrators is considered as an example. Logoperiodic vibrator antennas with straight and inclined distributing feeders are compared. It is shown that the band of synphase wave parasitic radiation does not excttd 1.5%.