Relationship between Signal and Antenna Tabs

It is important to understand how options on different tabs—Signal and Antenna are interrelated and impact the overall extraction.

The Antenna tab in the Running step Extract form provides various calculation options for calculating the input, output, and tristate antenna pins and the antenna metal and side areas. If any one of the calculation options is selected, full extraction is performed for establishing antenna properties.

You must specify the polysilicon, contact cut, and diffusion layers, along with a suitable expression for the diffusion layer, such as (diffn (diffn andnot poly)), in the Layer Assignment Tables. If you do not provide this information, the extraction process will not be able to locate any polysilicon or diffusion geometry that is required to perform the subsequent antenna calculation and gate/drain recognition. It is not necessary to provide a complex expression for the polysilicon layer; it has to be listed as an extract layer. You should ensure that diffusion, contact, or polysilicon layer information is not entered in the pin layer field on the Map tab because you only want to extract through these layers and not create pins on them.

It is feasible to turn off the Extract signal nets option at this point. This would result in Abstract Generator performing a full extraction in the background to calculate the antenna properties specified in the Antenna tab. The result would be that the pins created would be the same as those created after the Pins step, that is, no new pins would be created. Effectively, in this scenario, a “behind-the-scenes” full extraction is being performed solely for the purpose of calculating antenna numbers. Alternatively, if the Extract signal nets option is turned on, full extraction will be performed and the geometry found during the extraction will be turned into pin geometry.

The table below shows the type of extraction that Abstract Generator would perform based on the options selected on the Signal and Antenna tabs in the Extract step.

''Extract signal nets'' option on the Signal Tab	Any ''Calculate'' option on the Antenna Tab	''Use different layer assignments for antenna calculations only'' option on the Antenna Tab	Type of Extraction Performed
Off	Off	Off	Preset pin extraction
On	Off	Off	Signal extraction only using the values specified in the Layer Assignment for Signal Extraction table.
Off	On	Off	Antenna extraction only using the values specified in the Layer Assignment for Signal Extraction table.
Off	Off	On	No extraction performed
On	On	Off	Antenna and signal net extraction using the values specified in the Layer Assignment for Signal Extraction table.
Off	On	On	Antenna extraction only using the values specified in the Layer Assignment for Signal Extraction table.
On	On	On	Signal and Antenna Layers are the Same The only extraction performed in this case is that using the values specified in the Layer Assignment for Signal Extraction table to calculate both antenna and signal nets extraction. Signal and Antenna Layers are Different Two extractions are performed in this case. Antenna extraction is performed first using the values specified in the Layer Assignment for Antenna Extraction table, followed by signal net extraction using the values specified in the Layer Assignment for Signal Extraction table.

The only other situation where two types of extractions are possible is when the Maximum depth option is set to a value different from the default value 20. In this situation, the rules mentioned in the table above would apply.

Virtuoso Abstract Generator User Guide
Product Version IC23.1, November 2023