Documentation

monopoleTopHat

Create capacitively loaded monopole antenna over rectangular ground plane

Description

The monopoleTopHat object is a top-hat monopole antenna mounted over a rectangular ground plane. The monopole always connects with the center of top hat. The top hat builds up additional capacitance to ground within the structure. This capacitance reduces the resonant frequency of the antenna without increasing the size of the element.

The width of the monopole is related to the diameter of an equivalent cylindrical monopole by the expression

$w=2d=4r$

,where:

• d is the diameter of equivalent cylindrical monopole

• r is the radius of equivalent cylindrical monopole.

For a given cylinder radius, use the cylinder2strip utility function to calculate the equivalent width. The default top-hat monopole is center-fed. The feed point coincides with the origin. The origin is located on the X-Y plane. Creation

Description

example

mth = monopoleTopHat creates a capacitively loaded monopole antenna over a rectangular ground plane.

mth = monopoleTopHat(Name,Value) creates a capacitively loaded monopole antenna with additional properties specified by one or more name-value pair arguments. Name is the property name and Value is the corresponding value. You can specify several name-value pair arguments in any order as Name1, Value1,..., NameN, ValueN. Properties not specified retains their default values.

Properties

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Monopole height, specified as a scalar in meters. By default, the height is chosen for an operating frequency of 75 MHz.

Example: 'Height',3

Data Types: double

Monopole width, specified as a scalar in meters.

Note

Monopole width should be less than 'Height'/4 and greater than 'Height'/1001. 

Example: 'Width',0.05

Data Types: double

Ground plane length along x-axis, specified as a scalar in meters. Setting 'GroundPlaneLength' to Inf, uses the infinite ground plane technique for antenna analysis.

Example: 'GroundPlaneLength',4

Data Types: double

Ground plane width along y-axis, specified as a scalar in meters. Setting 'GroundPlaneWidth' to Inf, uses the infinite ground plane technique for antenna analysis.

Example: 'GroundPlaneWidth',2.5

Data Types: double

Top hat length along x-axis, specified as a scalar in meters.

Example: 'TopHatLength',4

Data Types: double

Top hat width along y-axis, specified as a scalar in meters.

Example: 'TopHatWidth',4

Data Types: double

Signed distance from center along length and width of ground plane, specified as a two-element vector.

Example: 'FeedOffset',[2 1]

Data Types: double

Lumped elements added to the antenna feed, specified as a lumped element object handle. For more information, see lumpedElement.

Example: 'Load',lumpedelement. lumpedelement is the object handle for the load created using lumpedElement.

Example: mth.Load = lumpedElement('Impedance',75)

Tilt angle of the antenna, specified as a scalar or vector with each element unit in degrees. For more information, see Rotate Antennas and Arrays.

Example: 'Tilt',90

Example: 'Tilt',[90 90],'TiltAxis',[0 1 0;0 1 1] tilts the antenna at 90 degree about two axes, defined by vectors.

Data Types: double

Tilt axis of the antenna, specified as:

• Three-element vectors of Cartesian coordinates in meters. In this case, each vector starts at the origin and lies along the specified points on the X-, Y-, and Z-axes.

• Two points in space, each specified as three-element vectors of Cartesian coordinates. In this case, the antenna rotates around the line joining the two points in space.

• A string input describing simple rotations around one of the principal axes, 'X', 'Y', or 'Z'.

For more information, see Rotate Antennas and Arrays.

Example: 'TiltAxis',[0 1 0]

Example: 'TiltAxis',[0 0 0;0 1 0]

Example: ant.TiltAxis = 'Z'

Object Functions

 show Display antenna or array structure; Display shape as filled patch info Display information about antenna or array axialRatio Axial ratio of antenna beamwidth Beamwidth of antenna charge Charge distribution on metal or dielectric antenna or array surface current Current distribution on metal or dielectric antenna or array surface design Design prototype antenna or arrays for resonance at specified frequency EHfields Electric and magnetic fields of antennas; Embedded electric and magnetic fields of antenna element in arrays impedance Input impedance of antenna; scan impedance of array mesh Mesh properties of metal or dielectric antenna or array structure meshconfig Change mesh mode of antenna structure pattern Radiation pattern and phase of antenna or array; Embedded pattern of antenna element in array patternAzimuth Azimuth pattern of antenna or array patternElevation Elevation pattern of antenna or array returnLoss Return loss of antenna; scan return loss of array sparameters S-parameter object vswr Voltage standing wave ratio of antenna

Examples

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Create and view a top hat monopole with 1 m length, 0.01 m width, groundplane dimensions 2mx2m and top hat dimensions 0.25mx0.25m.

th = monopoleTopHat
th =
monopoleTopHat with properties:

Height: 1
Width: 0.0100
GroundPlaneLength: 2
GroundPlaneWidth: 2
TopHatLength: 0.2500
TopHatWidth: 0.2500
FeedOffset: [0 0]
Tilt: 0
TiltAxis: [1 0 0]

show(th) Calculate and plot the impedance of a top hat monopole over a frequency range of 40MHz-80MHz.

th = monopoleTopHat;
impedance(th,linspace(40e6,80e6,41)); Impedance comparison between a monopole of similar dimensions and the top hat monopole in example 2.

m = monopole;
figure
impedance(m,linspace(40e6,80e6,41)); Balanis, C.A. Antenna Theory. Analysis and Design, 3rd Ed. New York: Wiley, 2005.

 Volakis, John. Antenna Engineering Handbook, 4th Ed. New York: Mcgraw-Hill, 2007.