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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. The most common form of log-periodic antenna is the log-periodic dipole array or LPDA, The LPDA consists of a number of half ...
The "Log-Periodic Dipole Array" [17] or "Log-Periodic Dipole Antenna" [18] (LPDA), is a practically modified self-complementary antenna. LPDA has transposed excitation [19] for the dipole array resulted from folding up [20] the antenna structure to obtain unidirectional radiation, that is inevitable outcome of the modification.
The driven element is often a dipole. The parasitic elements act as resonators and couple electromagnetically with the driven element, and serve to modify the radiation pattern of the antenna, directing the radio waves in one direction, increasing the gain of the antenna. An antenna may have more than one driven element, although the most ...
A modern high-gain UHF Yagi television antenna with 17 directors, and one reflector (made of four rods) shaped as a corner reflector. Drawing of Yagi–Uda VHF television antenna from 1954, used for analog channels 2–4, 54–72 MHz (U.S. channels). It has five elements: three directors (to left) one reflector (to right) and a driven element ...
Antennas can be classified in various ways, and various writers organize the different aspects of antennas with different priorities, depending on whether their text is most focused on specific frequency bands; or antenna size, construction, and placement feasibility; or explicating principles of radio theory and engineering that underlie, guide, and constrain antenna design.
The "Tri-Boom" is three Yagis. X-Beam The elements in the "X-beam" antenna (lower right), driven and parasitic, are "bowtie" ("butterfly") dipoles made of a pair of V-shaped elements. These same type of elements are used in reflective array UHF TV antennas; their wide BW is enough to cover the band.
AN/FLR-9 in Elmendorf, Alaska c. 1964. The AN/FLR-9 is a type of very large circularly disposed antenna array, built at eight locations during the Cold War for HF/DF direction finding of high priority targets. The worldwide network, known collectively as "Iron Horse", could locate HF communications almost anywhere on Earth.
An antenna array (or array antenna) is a set of multiple connected antennas which work together as a single antenna, to transmit or receive radio waves. [ 1 ] : p.149 [ 2 ] The individual antennas (called elements ) are usually connected to a single receiver or transmitter by feedlines that feed the power to the elements in a specific phase ...