Yagi-Uda acronym list, terms and Definitions

Acronym and definition in use for Yagi-Uda and related antenna:

aerial. The same as antenna.

antenna. A means for receiving or radiating radio waves.

antenna pattern. The same as radiation pattern.

antenna resistance. The real part of the input impedance of an antenna.

aperture of an antenna. A plane surface near the antenna, perpendicular to the direction of maximum radiation, through which the major part of the radiation passes.

aperture blockage. A blocking of the radiation from part of the feed itself or the support structures.

area of an antenna. The same as effective area of an antenna.

array antenna. An antenna comprising a number of radiating elements to obtain a directional radiation pattern.

array element. In an array antenna the single radiating element that have a fixed relative excitation.

bandwidth of an antenna. The frequency range within which the performance of the antenna, with respect to some characteristic, conforms to a specified value.

beam of an antenna. The main lobe of the radiation pattern of an antenna.

beamwidth. The same as half power beamwidth.

circularly polarized plane wave. A plane wave in which the electric field is circularly polarized.

cross polarization. The polarization orthogonal to a reference polarization.

dipole antenna. In the common usage is the electrically half wave length metallic radiating structure in which the current has a node only at each end.

directional antenna. An antenna having the property of radiating or receiving electromagnetic waves more effectively in some directions than others.

directive gain. In a given direction, 4π times the ratio of the radiation intensity in that direction to the total power radiated by the antenna.

directive gain in physical media. In a given direction and at a given point in the far field, the ratio of the power flux per unit area from an antenna to the power flux per unit area from an isotropic radiator at the antenna terminal delivering the same power from the antenna to the medium.

directivity. The value of the directive gain in the direction of its maximum value.

director element. A parasitic element located forward of the driven element of an antenna, intended to increase the directive gain of the antenna in the forward direction.

doublet antenna. The same as dipole antenna.

driven element. A radiating element coupled directly to the feed line of an antenna.

effective area of an antenna. In a given direction is the ratio of the available power at the terminals of a receiving antenna to the power per unit area of a plane wave incident from that direction, with the same polarization that the antenna would radiate.

effective height of an antenna. The height of the antenna centre of the radiation above the ground level.

effective radiated power (ERP). In a given direction is the power gain of the antenna multiplied the net available power at the antenna terminals.

efficiency. See radiation efficiency.

element. See director; driven; parasitic; radiating; radiator; reflector.

E plane. The plane containing the electric field vector and the direction of maximum radiation in linearly polarized antenna.

fan-beam antenna. An antenna system producing a major lobe whose transverse cross section has a large ratio of major to minor dimension.

far-field region. That region of the field of an antenna where the angular field distribution is essentially independent of the distance from the antenna.

feed of an antenna. The part of the antenna coupled to the input/output terminals, the same as primary radiator.

folded dipole. A device composed of two or more parallel closely spaced dipole connected together at their ends to the dipole fed at its centre.

front to back ratio (F/B). The ratio of the directivity of an antenna to its directive gain in a specified direction towards the back.

front to rear ratio (F/R). The same as front-to-back ratio.

gain. See directive gain; directivity; power gain.

Gregorian antenna. A double reflector antenna with a sub reflector located at a distance greater than the focal length from the vertex of the main reflector.

ground plane (imaging plane). A conducting or reflecting plane functioning to image a radiating structure.

G/T ratio. The ratio of the maximum power gain to the noise temperature of an antenna.

half power beamwidth. In a plane containing the direction for the maximum radiation of a beam, the angle between the two directions in which the radiation intensity is one half the maximum value of the beam.

horizontally polarized field vector. A linearly polarized field vector whose direction is horizontal.

horizontally polarized plane wave. A plane wave in which the electric field is horizontally polarized.

H plane. For a linearly polarized antenna, the plane containing the magnetic field vector and the direction of maximum radiation.

Impedance. Input/Output impedance; intrinsic impedance; mutual impedance; self-impedance.

Input/Output impedance. The impedance presented by an antenna at its terminals.

interferometer antenna. An array antenna in which the inter element spacing are large compared to wavelength and element size so as produce grating lobes.

intrinsic impedance. The theoretical input/output impedance of an antenna for the basic radiating structure when idealized.

isolated impedance of an array element. The impedance of a radiating element of an array antenna with all other elements of the array absent.

isolation dB between antennas. The ratio of power input to one antenna to the power received by the other expressed in decibel.

isotropic radiator. A hypothetical antenna having equal radiation intensity in all directions.

linear array antenna. An antenna having the centre of the radiating elements lying along a straight line.

linearly polarized field vector. A field vector for which the polarization ellipse is a line segment.

linearly polarized plane wave. A plane wave in which the electric field is linearly polarized.

lobe. See beam of an antenna; major lobe; minor lobe; radiation lobe; side lobe.

log periodic antenna. Any one of the classes of antennas having a structural geometry such that its impedance and radiation characteristic repeat periodically as the logarithm of frequency.

long-wire antenna. A wire antenna of considerable length in comparison with the operating wavelength, which provides a directional radiation pattern.

main lobe. The same as major lobe.

major lobe. The radiation lobe containing the direction of maximum radiation.

minor lobe. Any lobe except a major lobe.

noise temperature of an antenna. The temperature of a resistor having an available thermal noise power per unit bandwidth, equal to that at the antenna output, at a specified frequency. It depends on its coupling to all noise sources in its environment as well as noise generated within the antenna.

omnidirectional antenna. An antenna having an essentially non directional pattern in azimuth and a directional pattern in elevation.

orthogonal polarization. The same as cross polarization.

parasitic element. A radiating element which is not connected to the feed lines of an antenna and which materially affects the radiation pattern and/or impedance of an antenna.

pattern. The same as radiation pattern.

pencil-beam antenna. A unidirectional antenna having a narrow major lobe with approximately circular contours of equal radiation intensity in the region of the major lobe.

phased array antenna. An array antenna whose beam direction or radiation pattern is controlled primarily by the relative phase of the excitation coefficients of the radiating elements.

planar array. An array antenna having the centre of the radiating elements lying in a plane.

plane of polarization. A plane containing the polarization ellipse.

plane wave. A wave in which the only dependence of the field vectors on position is through the same exponential factor whose exponent is a linear function of position. See polarization of a plane wave.

polarization of an antenna. In a given direction, the polarization or the wave radiated by the antenna. Alternatively, the polarization of a plane wave incident from the given direction which results in maximum available power at the antenna terminals.

power gain. In a given direction, 4 π times the ratio of the radiation intensity in that direction to the net power accepted by the antenna from the connected transmitter.

power gain in physical media. In a given direction and at a given point in the far field, the ratio or the power flux per unit area from an antenna to the power flux per unit area from an isotropic radiator at a specified location with the same power input as the subject antenna.

primary radiator. A feed which illuminates a secondary radiator.

proximity-coupled dipole array antenna. An array antenna consisting of a series of coplanar dipoles, loosely coupled to the electromagnetic field of a balanced transmission line, the coupling being a function of the proximity and orientation of the dipole to the transmission line.

radiating element. A basic subdivision of an antenna that in it self is capable of effectively radiating or receiving radio waves. The dipole is the typical example of radiating antenna.

radiation efficiency. The ratio of the total power radiated by an antenna to the net power accepted by the antenna from the connected transmitter.

radiation, electromagnetic. The emission of energy in the form of electromagnetic waves.

radiation intensity. In a given direction, the power radiated from an antenna per unit solid angle.

radiation lobe. A portion of the radiation pattern bounded by regions of relatively weak radiated intensity.

radiation pattern (antenna pattern). A graphical representation of the radiation properties of the antenna as a function of space coordinates. Usually referred to the far-field region, properties include power flux density, field strength, phase and polarization.

radiation resistance. The ratio of the power radiated by an antenna to the square of the r.m.s. antenna current referred to a specified point.

radiator. Any antenna or radiating element that is a discrete physical and functional entity.

radome. An enclosure for protecting an antenna from the harmful effects or its physical environment, generally intended to leave the electrical performance of the antenna unaffected.

realized gain. The power gain of an antenna in its environment, reduced by the losses due to the mismatch of the antenna input impedance to a specified impedance.

reference boresight. A direction defined by an optical, mechanical, or electrical axis of an antenna established as a reference for the alignments. See electrical boresight.

reflector antenna. An antenna consisting of a reflector and a radiating feed.

reflector element. A parasitic element located in a direction other than forward of the driven element of an antenna intended to increase the directive gain of the antenna in the forward direction.

relative directive gain. In a given direction and at a given point in the far field, the ratio of the power flux per unit area from an antenna to the power flux per unit area from a reference antenna at a specified location and delivering the same power from the antenna to the medium.

relative power gain. The ratio of the power gain, in a given direction, to the power gain of a reference antenna, in its reference direction. Reference antenna is commonly an half-wave dipole.

resonant frequency. A frequency at which the input impedance of an antenna is non reactive.

rhombic antenna. An antenna composed of long-wire radiators comprising the sides as a rhombus. The antenna usually is terminated in a resistance.

side lobe. A radiation lobe in any direction other than that of the intended lobe.

side lobe level. Generally the relative level of the highest side lobe, expressed in dB.

spillover. That part of the power radiated by a feed not intercepted by the secondary radiator.

squint angle. A small difference in pointing angle between a reference beam direction and the direction of maximum radiation.

subreflector. A reflector which redirects the power radiated from the feed to the main reflector.

superdirectivity. The directivity of an antenna when its value exceeds the value which could be expected from the antenna on the basis of its dimensions and the excitation that would have yielded in-phase addition in the direction of maximum radiation intensity. Super directivity happens only at the cost of a large increase in the ratio of average stored energy to energy radiated per cycle.

turnstile antenna. An antenna composed of two dipole antennas, perpendicular to each other, with their axes intersecting at their midpoints. Usually, the currents on the two dipole antennas are equal and in phase quadrature.

V shape antenna. A V shape arrangement of conductor, balanced-fed at the apex and with included angle, length, and elevation proportioned to give the desired directive properties.

whip antenna. A thin flexible monopole antenna.

Yagi-Uda antenna. A linear end-fire array consisting of a driven element, one or more reflector elements, and one or more director elements.

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