Types of Antenna

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Whip antenna A whip antenna is an antenna consisting of a single straight flexible wire or rod, often mounted above some type of conducting surface called a ground plane.[1] The bottom end of the whip is connected to the radio receiver or transmitter. They are designed to be flexible so that they won't break off, and the name is derived from their whip-like motion when disturbed. Often whip antennas for portable radios are made of a series of interlocking telescoping metal tubes, so they can be
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  Whip antenna A whip antenna is anantenna consisting of a single straight flexible wire or rod, often mounted above some type of conducting surface called a ground plane. [1]  The bottom end of the whip is connected to theradio  receiver or  transmitter .They are designed to be flexible so that they won't break off, and the name is derived from their whip-like motion when disturbed. Often whip antennas for portable radios are made of a series of interlocking telescoping metal tubes, so they can be retracted when not in use. They are the most commontype of  monopole antenna.These antennas are widely used for hand-held radios such ascell phones, cordless  phones, walkie-talkies, FM radios,boom boxes, Wifi enabled devices, andGPSreceivers, and also attached to vehicles as the antennas for car radiosandtwo way radiosfor police, fire and aircraft. The whip antenna can be considered half of adipole antenna, and like a vertical dipole hasan omnidirectional radiation pattern,radiating equal radio power in all azimuthal directions (perpendicular to the antenna's axis), with the radiated power falling off with elevation angle to zero on the antenna's axis. Verticalwhip antennas are widely used for nondirectional radio communication on the surface of the Earth, where the direction to the transmitter (or the receiver) is unknown or constantly changing, for example in portable FM  radioreceivers,walkie-talkies,andtwo-way radios in vehicles. This is because they transmit (or receive) equally well in all horizontal directions, while radiating little radio energy up into the sky where it is wasted. Length Whip antennas are normally designed asresonantantennas. Therefore the length of the whip antenna isdetermined by thewavelength of the radio waves used. The most common length is one-quarter of the wavelength, called aquarter-wave whip (although this type of antenna is often shortened by the use of a loading coil; see Electrically short whipsbelow). For example, the common quarter-wave whip antennas used on FM radios in the USA are approximately 75 cm long, which is roughly one-quarter the length of radio wavesin theFM radio band, which are 2.78 to 3.41 meters long. Half-wavewhip antennas are also common. Whip antennas are very common in hand-held radios. This is a variation called aRubber Ducky antenna on a handheld UHFCBtransciever.  Turnstile antenna A turnstile antenna is a set of two dipole antennasaligned at right angles to each other and fed 90 degrees out-of-phase. The name reflects that the antenna looks like a turnstilewhen mounted horizontally. When mounted horizontally the antenna is nearlyomnidirectionalon the horizontal plane. When mounted verticallythe antenna is directional to a right angle to its plane and iscircularly polarized.The turnstile antenna is often used for communication satellitesbecause, being circularly polarized, the polarization of the signal doesn'trotate when thesatellite rotates. The principles of the turnstile antenna are also applicable to Yagi andLog-periodic antennas. A random wire antenna (or  long-wire antenna ) is aradio frequency antenna consisting of a wire whose length does not bear a relation to thewavelength of the radio waves used, but is typically chosen more for  convenience. This type of antenna sometimes is called the zig-zag antenna, as it may be strung back andforth between trees just to get enough wire into the air. For example, an antenna for 3MHz might be 20 m(66 ft) - 40 m (131 ft) long. Such antennas are usually not as effective as antennas whose length isadjusted toresonateat the wavelength to be used. They are widely used as receiving antennas onthelong wave,medium wave, andshort wavebands, as well as transmitting antennas on these bands for  small outdoor, temporary or emergency transmitting stations, as well as in situations where morepermanent antennas cannot be installed. Random wire antennas are a type of monopole antennaand theother side of the receiver or transmitter antenna terminal must be connected to an earth ground. Radiation pattern Theradiation patternof a straight random wire antenna is unpredictable and depends on its electrical  length,it may have several lobes at angles to the antenna axis. [1] The radiation will drop off to zero on theaxis. A folded or zig-zag antenna will have an even more unpredictable pattern. Construction Usually, it consists of a long (at least one quarter wavelength) wire with one end connected to the radioand the other in free space, arranged in any way most convenient for the space available. Ideally, it is astraight wire strung as high as possible between trees or buildings, the ends insulated from supportswith strain insulators.Typically it is made from number 12 or 14 AWG (1.6 to 2.0 mm (0 in) diameter) copperclad wire. Folding (to fit in space available) will reduce effectiveness and make theoretical analysisextremely difficult. (The added length helps more than the folding typically hurts.)If used for transmitting, a random wire antenna usually will also require an antenna tuner ,as it has an unpredictableimpedancethat varies with frequency. [2]  One side of the output of the tuner is connecteddirectly to the antenna, without atransmission line,the other to a good earth ground. One- quarter  wavelengthworks best, and one half wavelength will work poorly with most tuners. [3][4] Since theantenna is located very close to the transmitter,RF feedback can be an issue. RF feedback can be minimized by selecting a wire length that causes the low feed-point impedance at a current loop to occur at the transmitter. [2]  Alternately, a remote tuner can be fed with feedline, and the tuner located on theantenna.  Horn antenna A horn antenna or  microwave horn is anantennathat consists of a flaring metal waveguideshaped like ahornto direct the radio waves. Horns are widely used as antennas at UHFandmicrowavefrequencies, above 300 MHz. [1] They are used asfeeders (calledfeed horns) for larger antenna structures such as parabolic  antennas, as standard calibration antennas to measure thegain of other antennas, and as directive antennas for such devices asradar guns, automatic door openers, and microwave radiometers. [2]  Their advantages aremoderate directivity (gain), low SWR, broadbandwidth,and simple construction and adjustment. [3] One of the first horn antennas was constructed in 1897 by Indian radio researcher  Jagadish Chandra Bosein his pioneering experiments with microwaves. [4] In the 1930s the first experimental research (Southworth andBarrow, 1936) and theoretical analysis (Barrow and Chu, 1939) of horns as antennas was done. [5] Thedevelopment of radar  in World War 2 stimulated horn research. The corrugated horn proposed by Kay in 1962 has become widely used as a feed horn for microwave antennas such as satellite dishesandradio telescopes. [5] An advantage of horn antennas is that since they don't have anyresonantelements, they can operate over awide range of  frequencies, a widebandwidth. The useable bandwidth of horn antennas is typically of the order  of 10:1, and can be up to 20:1 (for example allowing it to operate from 1 GHz to 20 GHz). [1]  The inputimpedance is slowly-varying over this wide frequency range, allowing low VSWRover the bandwidth. [1] The gainof horn antennas ranges up to 25dBi,with 10 - 20 dBi being typical. [1]  Parabolic antenna A parabolic antenna is anantenna that uses aparabolic reflector , a curved surface with the cross-sectional shape of a parabola,to direct the radio waves. The most common form is shaped like adish and is popularly called a dish antenna or  parabolic dish . The main advantage of a parabolic antenna is that it ishighly directive; it functions similarly to asearchlightor  flashlightreflector to direct the radio waves in a narrow beam, or receive radio waves from one particular direction only. Parabolic antennas have some of thehighest gains, that is they can produce the narrowest beam width angles, of any antenna type. [1]  In order toachieve narrow beamwidths, the parabolic reflector must be much larger than thewavelengthof the radiowaves used, so parabolic antennas are used in the high frequency part of theradio spectrum,  at UHFand microwave(SHF) frequencies, at which wavelengths are small enough that conveniently sized dishes can be used.Parabolic antennas are used as high-gain antennas for point-to-pointcommunication, in applications such asmicrowave relay links that carry telephone and television signals between nearby cities,wireless  WAN/LAN links for data communications, satellite and spacecraft communication antennas, andradio  telescopes.Their other large use is inradar antennas, which need to emit a narrow beam of radio waves to locate objects like ships and airplanes. With the advent of home satellite television dishes, parabolic antennas have become a ubiquitous feature of the modern landscape. Patch antenna A patch antenna (also known as a rectangular microstrip antenna ) is a type of radioantennawith a low profile,which can be mounted on a flat surface. It consists of a flat rectangular sheet or patch of metal, mounted over a larger sheet of metal called aground plane.The assembly is usually contained inside a plasticradome,which protects the antenna structure from damage. Patch antennas are simple to fabricate and easy to modify andcustomize. They are the original type of microstrip antennadescribed by Howell [1] ; the two metal sheets
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