antenna siminar

Antenna characteristics Antenna characteristics: it is a definition of various necessary parameters. To d escribe the performance of an antenna. Some of these parameters may by interrelated (one dependent of on other parameters) 1. Antenna Patter n : An antenna radiation patter n or antenna patte rn is de ﬁned as “mathematica l function or a graphical representation of the radiation properties of the antenna as a function of space coordinates. In most cases, the radiation pattern is determined in the far ﬁeld region and is rep res ent ed as fun cti on of the dir ectional coordinates.in a polar parameters (r, À )..,..antenna pattern may sub classified into: A. Fi el d pat tern (in linear scale ): Ty picall y repres ents a plot of th e mag nitude of th e Elect ric or magnetic field as a function of the angular space . (r, À ) and (r , Í ) B. power patt ern (i n line ar sca le) ty pica lly rep rese nts a p lot of the sq uare of the Magnitude of the electric or magnetic field as a function of the angular space. (r, À ) and (r, Í ) C. power patt ern (in dB) repre sen t the magnitude of th e el ectric or mag neti c field , in decibels, as a function of the angular space. Where: r: represent the magnitude of the Power in P-patt ern or the value of the electrical or magn etic in Field pattern À : Elevation angle Í : Azimuth angl e But all of this these def initions (A, B, C) has an obvious defect, whe n the source increase the feeder current to the antenna, this will increase the power and the Electrical and magnetic Field; i.e. this will increase “r” in the plot while the antenna is the same! , so we will use more strike definitions which is: normalized field pattern and normalized power pattern: Note that both the numerator and denominator have the same r dependence, and hence the ratio is independent of r Example: plot the field and power pattern for hertz ian dipole if F farfield ={ Z o jI o dl βe -jβr sin( À )}/4 Лr Solution to simplify the plot of the pattern 1-find the symmetry of the F ( À ) about the axis 2-Find the max imum and min imum values of F ( À ) b y equa ting F ( À ) to zer o (d F ( À )/d À =0) and solve for À 3-Find the nulls of F( À ) equating F( À ) to zero(F( À ) =0) and solve for À

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8/2/2019 Antenna Siminar

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Antenna characteristicsAntenna characteristics: it is a definition of various necessary parameters. To describe the

performance of an antenna. Some of these parameters may by interrelated (one dependent ofon other parameters)

1. Antenna Patter n : An antenna radiation pattern or antenna pattern is de fined as

“mathematical function or a graphical representation of the radiation properties of the

antenna as a function of space coordinates. In most cases, the radiation pattern is

determined in the far field region and is represented as function of the directional

coordinates.in a polar parameters (r, À )..,..antenna pattern may sub classified into:

A. Field pattern (in linear scale): Typically represents a plot of the magnitude of the Electric or

magnetic field as a function of the angular space . (r, À ) and (r ,Í )B. power pattern (in linear scale) typically represents a plot of the square of the

Magnitude of the electric or magnetic field as a function of the angular space. (r, À ) and (r, Í )

C. power pattern (in dB) represent the magnitude of the electric or magnetic field, in decibels, as a function of the angular space.

Where: r: represent the magnitude of the Power in P-pattern or the value of the electrical or magnetic inField patternÀ: Elevation angleÍ : Azimuth angle

But all of this these definitions (A, B, C) has an obvious defect, when the source increase the

feeder current to the antenna, this will increase the power and the Electrical and magnetic Field;i.e. this will increase “r” in the plot while the antenna is the same! , so we will use more strike

definitions which is: normalized field pattern and normalized power pattern:

Note that both the numerator and denominator have the same r dependence, and hence

the ratio is independent of r

Example: plot the field and power pattern for hertzian dipole if F farfield = Z o jI odl βe-jβr

sin( À)/4 Лr

Solution

to simplify the plot of the pattern

1-find the symmetry of the F (À) about the axis

2-Find the maximum and minimum values of F (À) by equating F (À) to zero (d F (À)/d À =0) and solve forÀ3-Find the nulls of F(À) equating F(À) to zero(F(À) =0) and solve for À