Drawing an Infinite Array in the Layout Editor

HFSS can model infinite, periodic structures where geometry drawn in a “unit cell” is repeated infinitely in the x and y directions. If you excite the infinite array with an edge port, the excitation radiates into free space. If you excite the array with a plane wave, the structure acts as a frequency-selective surface (FSS) or filter receiving the excitation.

1. Right-click the design in the project tree and select Infinite Array.
2. The array is drawn using a rectangular unit cell. Select the center point of the unit cell by typing its coordinates in the X and Y fields.
3. Specify the dimensions of the unit cell by typing its width in the a text box and its height in the b text box.

• Alternatively, click Autosize to give the rectangle the same dimensions as the model geometry.
  Note:

  You may draw geometry outside the unit cell. The mesh is automatically generated in a way that assures current continuity across the boundaries of the unit cell.

4. Select Turn on infinite array/FSS to activate the array in the project.

The array is stored with the project, whether or not it is active.

5. Type a Skew Angle (gamma) that represents how the array lattice is repeated between rows of cells.
6. If the infinitely periodic structure represents an infinite array, type the array’s Scan Angle values in the Theta and Phi fields.

The scan angle determines how the different cells of the array are excited periodically. Theta is the angle measured on the z-axis, which is the axis perpendicular to the plane of the work space, and must be from 0 to 180 degrees. Phi is the angle measured on the x-axis and can be from 0 to 360 degrees.

If the periodic structure represents an FSS filter, these values are not appropriate. The incident angle of the plane wave is defined in the Setup Plane Wave Excitation window.

7. Select a display color for the array.
8. Click OK.

The rectangular structure you drew and its associated excitation are repeated infinitely.