The via fence 140 may include a fence pattern 141 that is configured to form a wall structure 144 having an individual chamber around each circuit module outside of the PWB. The wall structure 144 has a height H (FIG. 5) above the ground layer 110, as will be discussed in relation to FIG. 5. The wall structure 144 may include a plurality of vias 147 (FIG. 2B) formed through the wall structure 144, such that the via hole is orthogonal to the longitudinal length or parallel to the height H (FIG. 5) of the wall structure 144. The plurality of vias 147 may be spaced at substantially equidistant intervals, for example, along the walls of the wall structure 144. The plurality of vias 147 may be designed to provide a level of frequency isolation. The spacing distance between adjacent vias 147 may be reduced to vary the level of frequency isolation. Alternately or in addition to varying the spacing distance between vias, the size of the vias, such as the radius, may be varied to vary the level of frequency isolation. The spacing at any location of the via fence 140 may vary from another location of the via fence to vary the isolation for different parts of the circuit or for the frequency.