A log periodic antenna is a directional antenna developed for use over a wide band of frequencies, built with an array of dipole elements. Log periodic antennas balance directivity, gain and a wide bandwidth, amplifying the strength of a signal. They are most commonly used in
radiated immunity EMC testing.
An antenna with log periodic properties can be designed in one of several formats, including zig zag, trapezoidal, v log, and slot log. Log periodic dipole arrays, known as LPDAs, are the most common variety. To achieve smoother frequency transitions, several dipole elements are integrated into the LPDA; different dipoles will activate as frequency fluctuates, with each designed for a specific frequency use.