Paraboloid

The Paraboloid Command

The Paraboloid command is a specialized tool for creating parabolic reflectors, the most common geometry for high-gain dish antennas used in satellite communications, radar, and radio astronomy.

To open the tool, navigate to Draw > Wire Grid / Solid Surface > Paraboloid.

Defining the Geometry

In the Paraboloid tab, you configure the mathematical curve and physical size of the reflector:

• Vertex Coordinates (Vx, Vy, Vz): The coordinates of the bottom-most point (the center) of the dish (Figs. 1 and 2).
• Focal Length: The distance from the vertex to the focal point where the feed antenna is typically placed. This determines the “deepness” of the dish.
• Aperture Radius: The distance from the central axis to the outer rim of the dish.
• Orientation (Theta and Phi): These angles define the direction of the paraboloid’s axis of symmetry. For a dish pointing directly upward, set Theta = 0 deg.

Curvature Options

• Curved Segments: This utilizes the exact mathematical parabolic curve. It is highly recommended for reflectors, as even small polygonal errors in the surface can lead to significant phase errors in the reflected wave at high frequencies.
• Straight Segments: Approximates the parabolic surface using a series of flat facets made of linear wires.

Faceting and Mesh Attributes

In the Attributes tab, you define the computational density of the reflector:

• Facets: Specify the number of divisions along the Radial (from vertex to rim) and Azimuthal (around the $360^{\circ}$ circumference) directions.
• Wire Grid: Select Circular cross-section to create a “mesh dish.” This is often used for lower-frequency antennas to reduce wind load and weight.
• Solid Surface: Select Flat or Rectangular cross-sections to model a solid metallic dish for maximum gain and front-to-back ratio.

Materials

The Materials tab allows you to set the resistivity of the reflector surface. While most reflectors are modeled as Perfect Electric Conductors (PEC), you can specify materials like Aluminum or Steel to account for ohmic losses in the reflector itself.