The Necessity of Impedance Matching for PCB Traces

Impedance matching is crucial for higher frequency circuits, but determining the cutoff point between low-frequency and high-frequency circuits is not clear. The popular rule of thumb that no impedance matching is needed if the critical length of a PCB trace is 1/10th of the wavelength may not be accurate. Calculations suggest that a 1/16th rule may be more appropriate for achieving a mismatch loss of less than 0.1 dB. It is important to consider the specific requirements of each design and conduct physical board measurements, as the dielectric constant of FR4 PCB material can vary between manufacturers and batches.