gregorian

Create Gregorian antenna

Description

The default gregorian object creates a conical horn fed Gregorian antenna resonating around 18.2 GHz. 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 sub-reflector. This antenna is used in radio telescopes and communication satellites. For more information see, Architecture of Gregorian Antenna.

Creation

Syntax

ant = gregorian

ant = gregorian(PropertyName=Value)

Description

ant = gregorian creates a horn conical fed Gregorian antenna with default property values. The default dimensions are chosen for an operating frequency of around 18.2 GHz. This antenna gives maximum gain when operated at 18.3 GHz.

ant = gregorian(PropertyName=Value) sets properties using one or more name–value arguments. PropertyName is the property name and Value is the corresponding value. You can specify several name-value arguments in any order as PropertyName1=Value1,...,PropertyNameN=ValueN. Properties that you do not specify, retain their default values.

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 sub-reflector of focal length 0.22 m.

Properties

Exciter — Antenna or array to use as exciter

hornConical (default) | antenna object | array object | custom antenna object | measuredAntenna object | empty array

Exciter antenna or array type, specified as either:

• Antenna object from the catalog (except reflector type, cavity type and platform-installed antennas)

• Array object from the catalog (except conformal and infinite arrays)

• Custom antennas: customAntennaGeometry, customAntennaMesh, customAntenna

• Measured pattern data of an antenna or array: measuredAntenna

• Empty array

To create the reflector backing structure without an exciter, specify this property as an empty array.

Example: dipole

Example: linearArray(Element=patchMicrostrip)

Example: customAntenna

Example: measuredAntenna

Example: []

Radius — Radius of main and subreflector

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

Radius of the main and sub-reflector, 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 sub-reflector.

Example: Radius=[0.4 0.2]

Data Types: double

FocalLength — Focal length of main and sub-reflector

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

Focal length of the main and sub-reflector, 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]

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: lumpedElement(Impedance=75)

Tilt — Tilt angle of antenna

0 (default) | scalar | vector

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

Example: 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.

Data Types: double

TiltAxis — Tilt axis of antenna

[1 0 0] (default) | three-element vector | 2-by-3 matrix | "X" | "Y" | "Z"

Tilt axis of the antenna, specified as one of these values:

• 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, specified as a 2-by-3 matrix corresponding to two three-element vectors of Cartesian coordinates. In this case, the antenna rotates around the line joining the two points.

• "x", "y", or "z" to describe a rotation about the x-, y-, or z-axis, respectively.

For more information, see Rotate Antennas and Arrays.

Example: [0 1 0]

Example: [0 0 0;0 1 0]

Example: "Z"

Data Types: double | string

SolverType — Solver for antenna analysis

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

Solver for antenna analysis, specified as a string. Default solver is "MoM-PO"(Method of Moments-Physical Optics hybrid). Other supported solvers are: "MoM" (Method of Moments), "PO" (Physical optics) or "FMM" (Fast Multipole Method).

Example: SolverType="MoM"

Data Types: string

Object Functions

axialRatio	Calculate and plot axial ratio of antenna or array
bandwidth	Calculate and plot absolute bandwidth of antenna or array
beamwidth	Beamwidth of antenna
charge	Charge distribution on antenna or array surface
current	Current distribution on antenna or array surface
design	Create antenna, array, or AI-based antenna resonating at specified frequency
efficiency	Calculate and plot radiation efficiency of antenna or array
EHfields	Electric and magnetic fields of antennas or embedded electric and magnetic fields of antenna element in arrays
feedCurrent	Calculate current at feed for antenna or array
impedance	Calculate and plot input impedance of antenna or scan impedance of array
info	Display information about antenna, array, or platform
memoryEstimate	Estimate memory required to solve antenna or array mesh
mesh	Generate and view mesh for antennas, arrays, and custom shapes
meshconfig	Change meshing mode of antenna, array, custom antenna, custom array, or custom geometry
msiwrite	Write antenna or array analysis data to MSI planet file
optimize	Optimize antenna and array catalog elements using SADEA or TR-SADEA algorithm
pattern	Plot radiation pattern of antenna, array, or embedded element of array
patternAzimuth	Azimuth plane radiation pattern of antenna or array
patternElevation	Elevation plane radiation pattern of antenna or array
peakRadiation	Calculate and mark maximum radiation points of antenna or array on radiation pattern
rcs	Calculate and plot monostatic and bistatic radar cross section (RCS) of platform, antenna, or array
resonantFrequency	Calculate and plot resonant frequency of antenna
returnLoss	Calculate and plot return loss of antenna or scan return loss of array
show	Display antenna, array structures, shapes, or platform
solver	Access FMM solver settings for electromagnetic analysis
sparameters	Calculate S-parameters for antenna or array
stlwrite	Write mesh information to STL file
vswr	Calculate and plot voltage standing wave ratio (VSWR) of antenna or array element

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]
     SolverType: 'MoM-PO'

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