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Radiation pattern

The Radiation Pattern tab shows the antenna far field as a 2D polar plot and a 3D lobe over the geometry, one pattern per simulated frequency. It fills in when a run finishes with the radiation pattern enabled.

Where the data comes from

The solver wraps the structure in a Huygens surface and records the near field on it during the run, then transforms that near field to the far field. Turn it on with enable_nf2ff (the Compute Radiation Pattern output toggle). The transform runs at a set of frequencies spread across the band, so every result below is available at each of those points. In auto mode the frequency count comes from the quality preset. In advanced mode nf2ff_num_freqs sets it directly, default 51, up to the backend ceiling of 512 points.

The far field is defined only when the box radiates into open space, so the run needs at least one PML face. Any mix of PML, PEC, and PMC on the remaining faces works. A PEC face acts as an infinite ground plane by image theory. Two cases are refused before the solve: a box with no PML face (a closed cavity, no radiated power), and a PEC or PMC pair on both faces of one axis (that axis is closed, so the pattern is undefined). See Boundaries.

Polar view

The polar view draws the two principal cuts, the E-plane and the H-plane. The right panel holds a frequency selector, a metrics block, and toggles for the two traces.

The frequency slider and the linked GHz spinbox pick which stored pattern to show. The dB scale is fixed across the slider (floor at -25 dB, ceiling a little above the peak directivity of the whole band) so the traces stay comparable as you scrub. The title reads the frequency and the peak directivity in dBi.

The metrics block reports:

  • Directivity max. Peak directivity at the selected frequency, in dBi.
  • HPBW theta and HPBW phi. Half-power beamwidth of the E-plane and H-plane cuts, in degrees, measured across the connected -3 dB region around the peak.
  • Sidelobe. Level of the largest lobe outside the main lobe, in dB relative to the peak, measured on the plane cut that carries the global peak.
  • F/B ratio. Peak gain minus the gain in the opposite direction on that same cut, in dB.

3D view

The 3D view draws the pattern as a colour-mapped lobe with the geometry overlaid at scale, so the beam direction reads against the antenna. Radius and colour both follow directivity over a 40 dB window below the peak, and the scalar bar is labeled in dBi.

Two opacity sliders set the alpha blend between the lobe and the geometry, and either can be hidden with its visibility toggle. Position and scale each have an auto mode and a manual mode:

  • Auto position centers the lobe on the geometry. Turn it off to set the X, Y, and Z origin directly in millimetres.
  • Auto scale sizes the lobe so its tip-to-tip diameter matches the longest dimension of the geometry. Turn it off to set the scale directly, which holds a fixed lobe size while you step across frequencies.

Split View shows the polar and 3D views side by side with a draggable splitter, both driven by the one frequency slider. With split off, the Polar Pattern and 3D Pattern buttons switch between the two panels.

Export to CSV

Export CSV asks what to write, then a save path. The scope dialog offers two choices:

  • E-plane and H-plane cuts writes only the two displayed curves. Columns: theta_deg, phi_deg, gain_dBi, plane.
  • Full 3D pattern writes every theta/phi sample the run holds for that frequency, with no resampling. Columns: theta_deg, phi_deg, gain_dBi.

Both files open with comment lines naming the frequency, the run, and the project. The export covers the frequency selected in the tab.

The CLI writes a flat table across the whole band instead, straight from the backend columns:

freq_hz,theta_deg,phi_deg,D_total_dBi,D_theta_dBi,D_phi_dBi

D_total_dBi is the total directivity, D_theta_dBi and D_phi_dBi the two polarization components, all in dBi.

From the CLI

rayrf run writes the same patterns headless: --export-polar for the polar PNG, --export-rad3d for the 3D PNG (add --export-rad3d-vtk for the surface as VTP), and --export-rad-pattern for the flat CSV above. --polar-freq-mhz and --rad3d-freq-mhz pick the frequency, defaulting to the band centre. Full flag list on the CLI reference.