gregorian

Create Gregorian antenna

Description

The gregorian object creates a horn conical fed Gregorian antenna. A Gregorian antenna is a parabolic antenna. In this antenna, the feed antenna is mounted at or behind the surface of the main parabolic reflector and aimed at the subreflector. This antenna is used in radio telescopes and communication satellites. For more information see, Architecture of Gregorian Antenna.

Creation

Syntax

ant = gregorian

ant = gregorian(Name,Value)

Description

ant = gregorian creates a horn conical fed Gregorian antenna with a default operating frequency of 18.48 GHz. This antenna gives maximum gain when operated at 18.3 GHz.

ant = gregorian(Name,Value) sets properties using one or more name-value pairs. For example, ant = gregorian('FocalLength',[0.4 0.22]) creates a Gregorian antenna with the main reflector of focal length 0.4 m and the subreflector of focal length 0.22 m.

Properties

Exciter — Antenna or array type used as exciter

hornConical (default) | antenna object | array object

Antenna type used as exciter, specified as an antenna or an array object.

Example: 'Exciter',dipole

Example: ant.Exciter = dipole

Example: ant.Exciter = linearArray('patchMicrostrip')

Radius — Radius of main and subreflector

[0.3175 0.0330] (default) | two-element vector

Radius of the main and subreflector, specified as a two-element vector with each element unit in meters. The first element specifies the radius of the main reflector, and the second element specifies the radius of the subreflector.

Example: 'Radius',[0.4 0.2]

Example: ant.Radius = [0.4 0.2]

Data Types: double

FocalLength — Focal length of main and subreflector

[0.2536 0.1416] (default) | two-element vector

Focal length of the main and subreflector, specified as a two-element vector with each element unit in meters. The first element specifies the focal length of the main reflector, and the second element specifies the focal length of the subreflector.

Example: 'FocalLength',[0.35 0.2]

Example: ant.FocalLength = [0.35 0.2]

Data Types: double

Load — Lumped elements

[1x1 lumpedElement] (default) | lumped element object

Lumped elements added to the antenna feed, specified as a lumped element object. You can add a load anywhere on the surface of the antenna. By default, the load is at the feed. For more information, see lumpedElement.

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

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

Tilt — Tilt angle of antenna

0 (default) | scalar | vector

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 degrees about the two axes defined by the vectors.

Note

The wireStack antenna object only accepts the dot method to change its properties.

Data Types: double

TiltAxis — Tilt axis of antenna

[1 0 0] (default) | three-element vector of Cartesian coordinates | two three-element vectors of Cartesian coordinates | 'X' | 'Y' | 'Z'

Tilt axis of the antenna, specified as:

• Three-element vector of Cartesian coordinates in meters. In this case, each coordinate in the 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: TiltAxis = 'Z'

Note

The wireStack antenna object only accepts the dot method to change its properties.

Data Types: double

SolverType — Solver for antenna analysis

'MoM-PO' (default) | 'MoM' | 'FMM'

Solver for antenna analysis, specified as the comma-separated pair consisting of 'SolverType' and 'MoM-PO' or 'MoM' (Method of Moments) or 'FMM' (Fast Multipole Method).

Example: 'SolverType','MOM'

Data Types: char

Object Functions

show	Display antenna, array structures or shapes
solver	Access FMM solver for electromagnetic analysis
axialRatio	Axial ratio of antenna
beamwidth	Beamwidth of antenna
charge	Charge distribution on antenna or array surface
current	Current distribution on antenna or array surface
design	Design prototype antenna or arrays for resonance around 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, dielectric antenna, or array structure
meshconfig	Change mesh mode of antenna structure
optimize	Optimize antenna or array using SADEA optimizer
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
rcs	Calculate and plot radar cross section (RCS) of platform, antenna, or array
returnLoss	Return loss of antenna; scan return loss of array
sparameters	Calculate S-parameter for antenna and antenna array objects
vswr	Voltage standing wave ratio of antenna

Examples

Default Gregorian Antenna and Radiation Pattern

Create and view a default Gregorian antenna.

ant = gregorian

ant = 
  gregorian with properties:

        Exciter: [1×1 hornConical]
         Radius: [0.3175 0.0330]
    FocalLength: [0.2536 0.1416]
           Tilt: 0
       TiltAxis: [1 0 0]
           Load: [1×1 lumpedElement]

show(ant)

Plot the radiation pattern of the antenna at 18.48 GHz.

pattern(ant,18.48e9)

Create Array-fed Gregorian Antenna

Create an array of vee dipole antennas.

e = dipoleVee('ArmLength',[0.03 0.03],'Width',0.01);
arr = rectangularArray('Element',e,'RowSpacing',0.05,'ColumnSpacing',0.05);

Create a Gregorian antenna with rectangular array as exciter

ant = gregorian('Exciter',arr);
show(ant)

More About

Parabolic Reflector Antennas

A typical parabolic antenna consists of a parabolic reflector with a small feed antenna at its focus. Parabolic reflectors used in dish antennas have a large curvature and short focal length and the focal point is located near the mouth of the dish, to reduce the length of the supports required to hold the feed structure. In more complex designs, such as the cassegrain antenna, a sub reflector is used to direct the energy into the parabolic reflector from a feed antenna located away from the primary focal point. Such type of antennas can be used in satellite communications and Astronomy and other emerging modes of communications

Architecture of Gregorian Antenna

Gregorian antenna consists of three structures:

• Primary parabolic reflector

• Hyperbolic convex subreflector

• Exciter element

Focus of the main reflector and the near focus of the subreflector in the region between the two dishes. Gregorian antenna forms a shorter focal length for the main dish.

Version History

Introduced in R2019b