Page 23 - Ten_HSD_Rules

iCD CPW Planner

Model microstrip Coplanar Waveguides to reduce radiation loss, of high-speed
serial links, significantly improving product performance

The classic coplanar waveguide (CPW) is formed by a microstrip conductor strip separated from a pair of
ground plane pours, all on the same layer, affixed to a dielectric medium. The impedance is determined
by the ratio of trace width to clearance, so size reduction is possible without limit, the only penalty being
higher losses. In addition, a virtual ground plane exists between any two adjacent lines, as there is no
field at that point. Hence crosstalk effects, between adjacent lines, are very weak.

An optional Dielectric Materials Library, of over 31,500 rigid and flexible materials up to 100GHz, can
optionally be incorporated to further improve accuracy. This can increase accuracy by up to 5%. This is
arguably the most comprehensive materials library in the PCB industry. This allows the creation of
realistic multilayer stackups using the same core, prepreg and solder mask materials stocked by the PCB
Fabricator so, what you calculate is what you get - not approximations!

The CPW offers several advantages over a conventional microstrip transmission line:

• Simplifies fabrication
• Facilitates easy shunt as well as series surface mounting of active and passive devices
• Eliminates the need for via holes and wraparound (ground plating on the edge of a substrate to
provide a low inductance path)
• Reduces radiation loss at very high microwave frequencies