Create Cassegrain antenna
cassegrain object creates a Cassegrain antenna. A
Cassegrain antenna is a parabolic antenna using a dual reflector system. In this
antenna, the feed antenna is mounted at or behind the surface of the main parabolic
reflector and aimed at the secondary reflector. For more information see, Architecture of Cassegrain Antenna.
Cassegrain antennas are used in applications such as satellite ground-based systems.
conical horn fed Cassegrain antenna with a resonating frequency of 18.51
GHz. This antenna gives maximum gain when operated at 18 GHz.
ant = cassegrain
creates a Cassegrain antenna, with additional Properties
specified by one or more name–value arguments.
ant = cassegrain(Name=Value)
the property name and
Value is the corresponding value.
You can specify several name-value arguments in any order as
ValueN. Properties not
specified retain their default values.
ant = cassegrain(Radius=[0.4 0.22])
creates a Cassegrain antenna with the main reflector with radius 0.4 m and
the secondary reflector with radius 0.22 m.
Exciter — Antenna or array to use as exciter
hornConical (default) | antenna object | array object |
measuredAntenna object | empty array
Exciter antenna or array type, specified as an antenna object, an array object, measured pattern data of an antenna, or an empty array. Except for reflector and cavity antenna elements, you can use any Antenna Toolbox™ antenna or array element as an exciter. To create the reflector backing structure without the exciter, specify this property as an empty array.
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.
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 sub-reflector.
Load — Lumped elements
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 is the object for the load created
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.
TiltAxis=[0 1 0;0 1 1]
tilts the antenna at 90 degrees about the two axes defined by the
TiltAxis — Tilt axis of antenna
[1 0 0] (default) | three-element vector | 2-by-3 matrix |
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.
"z"to describe a rotation about the x-, y-, or z-axis, respectively.
For more information, see Rotate Antennas and Arrays.
[0 1 0]
[0 0 0;0 1 0]
SolverType — Solver for antenna analysis
"MoM-PO" (default) |
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
|Display antenna, array structures, shapes, or platform|
|Access FMM solver for electromagnetic analysis|
|Axial ratio of antenna|
|Beamwidth of antenna|
|Charge distribution on antenna or array surface|
|Current distribution on antenna or array surface|
|Design prototype antenna or arrays for resonance around specified frequency or create AI-based antenna from antenna catalog objects|
|Electric and magnetic fields of antennas or embedded electric and magnetic fields of antenna element in arrays|
|Input impedance of antenna or scan impedance of array|
|Mesh properties of metal, dielectric antenna, or array structure|
|Change meshing mode of antenna, array, custom antenna, custom array, or custom geometry|
|Optimize antenna or array using SADEA optimizer|
|Plot radiation pattern and phase of antenna or array or embedded pattern of antenna element in array|
|Azimuth plane radiation pattern of antenna or array|
|Elevation plane radiation pattern of antenna or array|
|Calculate and plot radar cross section (RCS) of platform, antenna, or array|
|Return loss of antenna or scan return loss of array|
|Calculate S-parameters for antennas and antenna arrays|
|Voltage standing wave ratio (VSWR) of antenna or array element|
Default Cassegrain Antenna and Radiation Pattern
Create and view a Cassegrain antenna.
ant = cassegrain
ant = cassegrain with properties: Exciter: [1x1 hornConical] Radius: [0.3175 0.0330] FocalLength: [0.2536 0.1416] Tilt: 0 TiltAxis: [1 0 0] Load: [1x1 lumpedElement] SolverType: 'MoM-PO'
Plot the radiation pattern of the antenna at 18.3 GHz.
Create Array-fed Cassegrain Antenna
Create a rectangular array of crossed dipole antennas.
e = dipoleCrossed(Tilt=90,TiltAxis=[0 1 0]); arr = rectangularArray(Element=e,Rowspacing=0.03,ColumnSpacing=0.03);
Use the rectangular array
arr to excite a Cassegrain antenna.
ant = cassegrain(Exciter=arr)
ant = cassegrain with properties: Exciter: [1x1 rectangularArray] Radius: [0.3175 0.0330] FocalLength: [0.2536 0.1416] Tilt: 0 TiltAxis: [1 0 0] Load: [1x1 lumpedElement] SolverType: 'MoM-PO'
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. Cassegrain provides an option to increase focal length, reducing side lobes. Such type of antennas can be used in satellite communications and Astronomy and other emerging modes of communications
Architecture of Cassegrain Antenna
Cassegrain antenna consists of three structures:
Primary parabolic reflector
Hyperbolic concave sub-reflector
Focus of the main reflector and the near focus of the sub-reflector coincides. The energy is transmitted from the subreflector to the primary parabolic reflector. The parabolic reflector converts a spherical wavefront into a plane wavefront as the energy directed towards it appears to be coming from focus.
Cassegrain Antenna in Receive Mode
In the receive mode, consider that energy in the form of parallel waves is incident up on the reflector system. This energy is intercepted by the main reflector, a large concave surface,and reflected towards the sub-reflector. The convex surface of the sub-reflector collects this energy and directs it towards the vertex of the main dish. If the rays directed towards this main dish are parallel, then the main reflector is parabolic and the sub-reflector is hyperbolic and the rays will focus on a single point. You then place the receiver at this focusing point.
Cassegrain Antenna in Transmit Mode
In the transmit mode, repeat the experiment to find the focusing point as in the receive mode. Place the feed at the focusing point. The feed is usually small and the sub reflector is in the far-field region of the feed. The size of the sub-reflector is large enough that it intercepts most of the radiation from the feed point. Because of the geometry and the shape of the main reflector and the sub-reflector the rays from the main dish are usually parallel.
 Dandu, Obulesu. "Optimized Design of Axillary Symmetric Cassegrain Reflector Antenna Using Iterative Local Search Algorithm"
 Balanis, C.A. Antenna Theory: Analysis and Design. 3rd Ed. New York: Wiley, 2005.
Introduced in R2019b