Issue link: https://iconnect007.uberflip.com/i/1534120
APRIL 2025 I DESIGN007 MAGAZINE 29 oritize the design of your RF layout first. ese are the most critical nets due to their open-air radiation. If these are not routed correctly, the range and accuracy will be negatively affected. RF layout rules include having enough ground stitching vias along the transmission line, avoiding parallel placement of inductive components, and separating RF analog and digital ground nets by employing a star con- figuration. For the best results, avoid exces- sively long RF trace paths. RF traces should be short, direct, and have a width correspond- ing to the desired impedance from the RF source to the antenna. ere are a few rea- sons why this is recommended: reduction of loss, impedance variation, and harmful interference involving the RF trace. Harm- ful interference is also why it's important to keep high-speed nets away from the RF trace. Shielding Traces with Transition Vias ere are times when longer RF traces are needed, such as when a specific impedance is required. In these cases, proper shielding is key to protect both the RF and high-speed nets from each other. A common way to shield an RF line is to employ transition vias to bring the RF down between two ground planes, shield- ing it top and bottom from possible EMI. e transition vias should maintain the impedance from the trace, as any impedance bumps will affect the signal and cause signal degradation. Other reasons for shielding are to prevent EMI from disrupting the other concurrent wireless and high-speed nets, as well as pre- venting the emission of unintentional radiation that could negatively impact the FCC com- pliance requirements. is is the most com- mon reason for shielding, putting a metal box around the circuitry like a Faraday cage to pro- vide EMI protection to and from the circuit. Simulate Early and Often It's important to know if your near-field and far-field are appropriate without spending the time and money on multiple respins, we highly recommend simulating your design. Whatever simulation tool you use, it's important to sim- ulate the circuit for several parameters—for both far-field and near-field—to catch poten- tial problems. It is costly to respin PCBs mul- tiple times. e use of simulation tools is rec- Figure 2: A complex via design created in Xpedition Layout to shield a critical trace.