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36 DESIGN007 MAGAZINE I APRIL 2025 Feature Article by Cherie Litson EPTAC ere are many great books, videos, and information online about designing PCBs for RF circuits. A few of my favorite RF sources are Hans Rosenberg, Stephen Chavez, and Rick Hartley, but there are many more. ese PCB design engineers have a very good per- spective on what it takes to take an RF design from schematic concept to PCB layout. Here's a quick summary of the common sug- gestions that I've learned from them and oth- ers over time: • A schematic shows the "ideal" functional- ity of the RF circuit. When creating a sche- matic in the PCB layout, the "real" physics of the copper strips, dielectric material, and adjacent circuits and metal features create parasitic influences: resistance, inductance, and capacitance. • It is the responsibility of the layout engi- neer to minimize the differences between the "ideal" and "real." • Electronic devices and systems operate at frequencies ranging from a few mega- hertz to several gigahertz. Finding the best method to control the parasitic influences requires only a few basic guidelines. a. Identify and understand the current loops in the circuit b. e shorter the loop, the lower the impedance and resistance ratios c. Use an uninterrupted ground plane as close as possible to the referenced signal d. Give each ground connection its own via as close as possible to the pad To do this in a PCB, remember it is a 3D envi- ronment. Uninterrupted ground plane layers close to their signal, impedance calculations, material selection, copper thicknesses, trace thicknesses, shielding, and spacing become the tools to control the parasitic influences of the "real" circuit. RF PCB Design Tips and Tricks