Antenna technology ppt

[...]... 1.0–4 GHz Gain of dipole antennas length L in Gain Gain(dB) 0.1 1.50 1.76dB 0.5 1.64 2.15dB 1.0 1.80 2.55dB 1.5 2.00 3.01dB 2.0 2.30 3.62dB 3.0 2.80 4.47dB 4.0 3.50 5.44dB 8.0 7.10 8.51dB Quarter-wave antenna The antenna and its image form a dipole that radiates only upward The quarter wave monopole antenna is a single element antenna fed at one end, that behaves as a dipole antenna It is formed by... waveguide shaped like a horn to direct the radio waves Horns are widely used as antennas at UHF and microwave frequencies, above 300 MHz They are used as feeders (called feed horns) for larger antenna structures such as parabolic antennas, as standard calibration antennas to measure the gain of other antennas, and as directive antennas for such devices as radar guns, automatic door openers, and microwave... vertical axis, or a dial, which modifies the electrical properties of the antenna at each dial position Folded dipole Folded dipole antenna Another common place one can see dipoles is as antennas for the FM band - these are folded dipoles The tips of the antenna are folded back until they almost meet at the feedpoint, such that the antenna comprises one entire wavelength This arrangement has a greater... be used Whip antenna The whip antenna is probably the most common and simplest-looking antenna These are monopoles, and the most common and practical is the quarter-wave monopole which could be considered as half of a dipole using a ground plane as the image of the other half The commonly referred-to end-fed dipole is actually just a half-wave monopole whip antenna Dipoles versus whip antennas Dipoles... depending on the mission Note that a doublet antenna will not work with the standard SINCGARS radio when using frequency hopping(FH) but is effective for single channel (SC) A doublet antenna is more practical for radios not intended for FH Collinear antenna systems based on dipoles J-Pole Antenna Dipoles can be stacked end to end in phased arrays to make collinear antenna arrays, which exhibit more gain... length of pipe that will be needed Chapter 2 Horn Antenna Pyramidal microwave horn antenna, with a bandwidth of 0.8 to 18 GHz A coaxial cable feedline attaches to the connector visible at top This type is called a ridged horn; the curving fins visible inside the mouth of the horn increase the antenna' s bandwidth A horn antenna or microwave horn is an antenna that consists of a flaring metal waveguide... unbalanced feeder, common mode currents can cause the coax line to radiate in addition to the antenna itself, and the radiation pattern may be asymmetrically distorted This can be remedied with the use of a balun Common applications Set-top TV antenna A "rabbit-ears" antenna with a UHF loop antenna The most common dipole antenna is the type used with televisions, often colloquially referred to as "rabbit ears"... is often considered equal to 2.15 dBi From Babinet's principle, a dipole antenna is complementary to a slot antenna consisting of a slot the same size and shape as a dipole cut from an infinite sheet of metal; both give the same radiation pattern Dipole with baluns Coax and antenna both acting as radiators instead of only the antenna A dipole, being composed of two symmetrical ungrounded elements,... four times that of a half-wave dipole Shortwave antenna A DIY-made dipole antenna with mast Dipoles for longer wavelengths are made from solid or stranded wire Portable dipole antennas are made from wire that can be rolled up when not in use Ropes with weights on the ends can be thrown over supports such as tree branches and then used to hoist up the antenna The center and the connecting cable can... minute, its effective aperture is comparable to antennas many times its size Dipole as a reference standard Antenna gain is sometimes measured as "x dB above a dipole", which means that the antenna in question is being compared to a dipole, and has x dB more gain (has more directivity) than the dipole tuned to the same operating frequency In this case one says the antenna has a gain of "x dBd" More often, . Chapter 1 - Dipole Antenna Chapter 2 - Horn Antenna Chapter 3 - Radio Telescope Chapter 4 - Parabolic Antenna Chapter 5 - Antenna (Radio) Chapter 6 - Television Antenna Chapter 7 -. Omnidirectional Antenna & Directional Antenna Chapter 1 Dipole Antenna A schematic of a half-wave dipole antenna that a shortwave listener might build. A dipole antenna. Quarter-wave antenna The antenna and its image form a dipole that radiates only upward. The quarter wave monopole antenna is a single element antenna fed at one end, that behaves as a dipole antenna.