This document describes techniques and systems of an exposed portion of a PCB configured to provide isolation among radar antennas. The described radar system includes an exposed portion of a surface of a printed circuit board (PCB) positioned between a first antenna and a second antenna. The PCB includes a metal plating on the surface of the PCB. A width of the exposed portion can delay a phase of electromagnetic (EM) energy conducted by the metal plating relative to a phase of EM energy that does not traverse the exposed portion. A height of the exposed portion can cause an amount of the EM energy conducted by the metal plating to be approximately equal to an amount of EM energy that traverses the exposed portion. In this way, the described systems and techniques can reduce signal-coupling among radar antennas without additional hardware costs and distance between the antennas.