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How can we get some loss reduction in this trace without somehow changing the loss tangent? The answer lies in the skin effect in the conductor. Once the nearest ground layer is cleared below the microstrip and the trace is referenced to the next ground layer, the width of the trace can be comfortably increased as this will help the trace hit its impedance target. The loss experienced by the signal will depend on the density of field lines around the microstrip line, but it is not necessarily because the loss tangent changes. Using a Ground Cutout to Reduce Conductor Losses I’ve included a small taper in the transition region, which ideally should be electrically short (about 10% of the operating wavelength for RF signals). This allows you to reduce total insertion losses in the cleared region without creating new return losses at the interface between these regions. When the trace enters the region with cleared ground, the trace width needs to be widened within the cleared region to set the impedance in both regions to be equal. When clearing out some ground in the region below the destination component, you now have to adjust the width of the microstrip trace on the surface layer so that you can maintain consistent impedance. Only 4 layers are indicated explicitly, but there could be additional layers on the interior of the stackup between the indicated GND layers. Example with skip routing into a connector. In this way, the transmission line impedance is now referenced to the next nearest layer in the stackup as long as the two ground regions are set to the same potential. This occurs because the act of shifting the ground plane away from the trace modifies the field distribution around the microstrip transmission line. Once the signal travels into the region with the ground clearance, the signal will experience lower losses. Skip routing involves clearing out some ground in the reference layer for a microstrip transmission line at the load end of a route. In this article, we’ll take a look at this routing method and explain how it can help recover some loss budget in a lossy interconnect. The name refers to skipping reference layers at the load end of an interconnect, thereby modifying the field distribution around a microstrip trace and reducing total losses. This is a technique that was described to me as skip reference routing, or just skip routing. There's one trick that you can use with microstrip lines that is implemented by 5G equipment/handset designers. What else can you do if losses are a problem on these long interconnects? Most designers will tell you to just use an alternative low-loss/RF material that has a lower loss tangent whenever losses are excessive on high-speed/high-frequency interconnects. When you have to route a long trace or a long differential pair to a connector or another component, what can you do if you're reaching the end of your loss budget? Controlled impedance routing at high frequencies is difficult enough, and it's important to make sure that you stay within your loss budget on long routes or in lossy media.