A log-periodic antenna (LP), also known as a log-periodic array or log-periodic aerial, is a multi-element, directional antenna designed to operate over a wide band of frequencies. It was invented by John Dunlavy in 1952.
Log‑Periodic Dipole Array Calculator by Serge Stroobandt, ON4AA and Michael McCue, W7YZT:
"A do-it-yourself" guide to design and construction of log periodic antennas:
Designing Log Periodic Antennas by Glen Dash, Ampyx LLC, GlenDash at alum.mit.edu: