Antenna Ground

Ground surface has influence on ground signal’s stability. Improper ground structure causes ground fluctuation, signal distortion and EMI problems. In many high-speed design practices, all signal nets are routed first and then the ground structure is constructed by automatically filling copper in empty areas.

Sometimes this automatic feature leaves narrow copper shapes without enough via connecting to ground. Current density increases significantly and the long narrow section may become the primary source of EMI.

EMI can be reduced if the narrow and long section is connected to the ground using vias.
  • Item: Rule check item name that will be referenced in the report.

  • Net: GND net group.
  • Max Check Width: Width of a narrow section of GND shape that is considered as an antenna.
  • Ratio (%): Pass/Fail criteria. Ratio of area covered by vias on the antenna ground section to area of the antenna ground section in percent.
  • Exclude Option: Exclude a specific area.
    • Exclude Polygon (Net): Exclude specific polygon or net by area size or net length.
    • By Area: Define the area of small narrow section that can be ignored.
    • By Length: Define the length of short net that can be ignored.
    • Measure base: Select measure base of Net length.
      • Total Length of Net: Ignore if pattern length is shorter than specified length.
      • Longer side length of Net shape: Ignore if longer side length of Net shape is shorter than specified length.

        Figure 1. Longer side length of net shape
    • Exclude Bottleneck: Exclude short bottlenecks from checking.
    • Exclude Component Area: Exclude areas covered by components listed in the selected component group.

Figure 2.