Remarkably, we find that this mode has the form of a uniform plane wave which propagates in the \(+\hat{\bf z}\) direction; i.e., squarely between the plates. Also, let us limit scope to the field dee...Remarkably, we find that this mode has the form of a uniform plane wave which propagates in the \(+\hat{\bf z}\) direction; i.e., squarely between the plates. Also, let us limit scope to the field deep within the “sandwich,” and neglect the region near the edges of the PCB. Therefore, the field deep inside the PCB may be interpreted as a single plane wave having the TM\(_0\) structure shown in Figure \(\PageIndex{1}\), propagating away from the source end of the PCB.