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Ground Proximity and Spacing

High frequency devices need to have good ground management and to place the ground as close as possible to the point being used for the measurement launch. Good ground management can be realized in several ways:

 

The signal trace over the dielectric and the ground plane underneath a dielectric layer. (microstrip)

 

Surface waves and crosstalk are common problems with microstrip.

 

The signal trace over the dielectric with two ground traces paralleling the signal trace. (coplanar microstrip,coplanar waveguide, CPW)

 

Typically, the ground traces should be at least three times wider than the signal trace to reduce inductance, crosstalk, and fringing effects.

 

The signal trace embedded in the dielectric, the ground plane underneath a dielectric layer, the ground plane over a dielectric layer, creating a sandwich. (Stripline) (Multilayer)

 

The signal trace over the dielectric with one ground trace paralleling the signal trace. (Asymetric CPW)

 

The signal trace will have more crosstalk on the unguarded side and the ground line inductance is increased.