Antenna (radio) - Wikipedia, the free encyclopedia. An antenna (plural antennae or antennas), or aerial, is an electrical device which converts electric power into radio waves, and vice versa. In transmission, a radio transmitter supplies an electric current oscillating at radio frequency (i. In reception, an antenna intercepts some of the power of an electromagnetic wave in order to produce a tiny voltage at its terminals, that is applied to a receiver to be amplified. Antennas are essential components of all equipment that uses radio. They are used in systems such as radio broadcasting, broadcast television, two- way radio, communications receivers, radar, cell phones, and satellite communications, as well as other devices such as garage door openers, wireless microphones, Bluetooth- enabled devices, wireless computer networks, baby monitors, and RFID tags on merchandise. Typically an antenna consists of an arrangement of metallic conductors (elements), electrically connected (often through a transmission line) to the receiver or transmitter. An oscillating current of electrons forced through the antenna by a transmitter will create an oscillating magnetic field around the antenna elements, while the charge of the electrons also creates an oscillating electric field along the elements. Watch TV for FREE with an indoor or outdoor HDTV antenna. Get up to 100 FREE HD channels. We have antenna ranges that cover up to 150 miles. Proud USA company and 100% FREE shipping. The D-Link ANT24-0801 is a Pico Cell Patch Antenna for wireless data transmission in indoor or outdoor environments. Antenna Patterns and Their Meaning. Home; Skip to content; Skip to footer; Worldwide. When the antennas are used in offices or in low hanging outdoor deployments. Manufacture outdoor wifi antenna, and much more! Buy outdoor wifi antenna from ZDA Communications today for a better deal A patch antenna (also known as a rectangular microstrip antenna) is a type of radio antenna with a low profile, which can be mounted on a flat surface. It consists of a flat rectangular sheet or 'patch' of metal, mounted over. These time- varying fields radiate away from the antenna into space as a moving transverse electromagnetic field wave. Conversely, during reception, the oscillating electric and magnetic fields of an incoming radio wave exert force on the electrons in the antenna elements, causing them to move back and forth, creating oscillating currents in the antenna. Antennas can be designed to transmit and receive radio waves in all horizontal directions equally (omnidirectional antennas), or preferentially in a particular direction (directional or high gain antennas). In the latter case, an antenna may also include additional elements or surfaces with no electrical connection to the transmitter or receiver, such as parasitic elements, parabolic reflectors or horns, which serve to direct the radio waves into a beam or other desired radiation pattern. The first antennas were built in 1. German physicist Heinrich Hertz in his pioneering experiments to prove the existence of electromagnetic waves predicted by the theory of James Clerk Maxwell. Hertz placed dipole antennas at the focal point of parabolic reflectors for both transmitting and receiving. He published his work in Annalen der Physik und Chemie (vol. The antenna in the center is two vertical metal rods, with an alternating current applied at its center from a radio transmitter (not shown). The voltage charges the two sides of the antenna alternately positive (+) and negative (. Loops of electric field (black lines) leave the antenna and travel away at the speed of light; these are the radio waves. The antenna consists of two metal rods connected to a receiver R. The electric field(E, green arrows) of the incoming wave pushes the electrons in the rods back and forth, charging the ends alternately positive (+) and negative (. Since the length of the antenna is one half the wavelength of the wave, the oscillating field induces standing waves of voltage (V, represented by red band) and current in the rods. The oscillating currents (black arrows) flow down the transmission line and through the receiver (represented by the resistance R). Terminology. Occasionally the term . However, note the important international technical journal, the IEEE Transactions on Antennas and Propagation. In the summer of 1. Marconi began testing his wireless system outdoors on his father's estate near Bologna and soon began to experiment with long wire . Marconi discovered that by raising the . Until then wireless radiating transmitting and receiving elements were known simply as aerials or terminals. Because of his prominence, Marconi's use of the word antenna (Italian for pole) spread among wireless researchers, and later to the general public. Especially at microwave frequencies, a receiving antenna may include not only the actual electrical antenna but an integrated preamplifier or mixer. Progress In Electromagnetics Research, Vol. Sim Syngenta Sensors University Innovation Center University of. An antenna, in converting radio waves to electrical signals or vice versa, is a form of transducer. Radio waves are electromagnetic waves which carry signals through the air (or through space) at the speed of light with almost no transmission loss. Radio transmitters and receivers are used to convey signals (information) in systems including broadcast (audio) radio, television, mobile telephones, Wi- Fi (WLAN) data networks, trunk lines and point- to- point communications links (telephone, data networks), satellite links, many remote controlled devices such as garage door openers, and wireless remote sensors, among many others. Radio waves are also used directly for measurements in technologies including radar, GPS, and radio astronomy. In each and every case, the transmitters and receivers involved require antennas, although these are sometimes hidden (such as the antenna inside an AM radio or inside a laptop computer equipped with Wi- Fi). Whip antenna on car, common example of an omnidirectional antenna. According to their applications and technology available, antennas generally fall in one of two categories: Omnidirectional or only weakly directional antennas which receive or radiate more or less in all directions. These are employed when the relative position of the other station is unknown or arbitrary. They are also used at lower frequencies where a directional antenna would be too large, or simply to cut costs in applications where a directional antenna isn't required. Directional or beam antennas which are intended to preferentially radiate or receive in a particular direction or directional pattern. In common usage . A dipole antenna is similar but consists of two such conductors extending in opposite directions, with a total length that is often, but not always, a half of a wavelength long. Dipoles are typically oriented horizontally in which case they are weakly directional: signals are reasonably well radiated toward or received from all directions with the exception of the direction along the conductor itself; this region is called the antenna blind cone or null. Both the vertical and dipole antennas are simple in construction and relatively inexpensive. The dipole antenna, which is the basis for most antenna designs, is a balanced component, with equal but opposite voltages and currents applied at its two terminals through a balanced transmission line (or to a coaxial transmission line through a so- called balun). The vertical antenna, on the other hand, is a monopole antenna. It is typically connected to the inner conductor of a coaxial transmission line (or a matching network); the shield of the transmission line is connected to ground. In this way, the ground (or any large conductive surface) plays the role of the second conductor of a dipole, thereby forming a complete circuit. Explore discounts on Outdoor dbi directional patch antenna. Compare Prices, & Save Money on brands such as CP Technologies at Bizrate.com. Compare 26 Patch Antenna products at SHOP.COM, including Laird 1850-1990 Mhz 7.5dB Gain Patch Antenna, LevelOne WAN-1112 12dBi Directional Indoor Patch Antenna - 12 dBi - Patch, TerraWave Patch Antenna - 13 dBi - 1 x RP-SMA. Patch Antenna, Wholesale Various High Quality Patch Antenna Products from Global Patch Antenna Suppliers and Patch Antenna Factory,Importer,Exporter at Alibaba.com.Since monopole antennas rely on a conductive ground, a so- called grounding structure may be employed to provide a better ground contact to the earth or which itself acts as a ground plane to perform that function regardless of (or in absence of) an actual contact with the earth. Antennas more complex than the dipole or vertical designs are usually intended to increase the directivity and consequently the gain of the antenna. This can be accomplished in many different ways leading to a plethora of antenna designs. The vast majority of designs are fed with a balanced line (unlike a monopole antenna) and are based on the dipole antenna with additional components (or elements) which increase its directionality. The increased power in the desired direction is at the expense of that in the undesired directions. Power is conserved, and there is no net power increase over that delivered from the power source (the transmitter.)For instance, a phased array consists of two or more simple antennas which are connected together through an electrical network. This often involves a number of parallel dipole antennas with a certain spacing. Depending on the relative phase introduced by the network, the same combination of dipole antennas can operate as a . Antenna arrays may employ any basic (omnidirectional or weakly directional) antenna type, such as dipole, loop or slot antennas. These elements are often identical. However a log- periodic dipole array consists of a number of dipole elements of different lengths in order to obtain a somewhat directional antenna having an extremely wide bandwidth: these are frequently used for television reception in fringe areas. The dipole antennas composing it are all considered . On the other hand, a superficially similar dipole array, the Yagi- Uda Antenna (or simply . The Yagi antenna has similar looking parasitic dipole elements but which act differently due to their somewhat different lengths. There may be a number of so- called . Since high directivity in an antenna depends on it being large compared to the wavelength, narrow beams of this type are more easily achieved at UHF and microwave frequencies. At low frequencies (such as AM broadcast), arrays of vertical towers are used to achieve directionality . For reception, a long Beverage antenna can have significant directivity. For non directional portable use, a short vertical antenna or small loop antenna works well, with the main design challenge being that of impedance matching. With a vertical antenna a loading coil at the base of the antenna may be employed to cancel the reactive component of impedance; small loop antennas are tuned with parallel capacitors for this purpose. An antenna lead- in is the transmission line (or feed line) which connects the antenna to a transmitter or receiver. The antenna feed may refer to all components connecting the antenna to the transmitter or receiver, such as an impedance matching network in addition to the transmission line.
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