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.
