Reduced log-periodic dipole antenna using a cylindrical-hat cover

A technique to decrease the size of log-periodic dipole array (LPDA) antennas employing inductive loads on its elements is introduced. This technique consists of adding a short-circuited cylindrical hat cover at the end of each arm of the antenna. Simulation and measurement results show that the total area, if considered as a trapezoid, of a fabricated LPDA antenna, based on the proposed technique, is approximately 50% smaller than the size area of a reference antenna using a conventional technique. The parameters of the reduced antenna are slightly modified, preserving the bandwidth, impedance, polarisation and radiation pattern shape. The drawback of this technique is the small reduction of gain, from 7.5 dB for the conventional antenna to 6.4 dB for the reduced prototype in the middle operation band.