The basic element of DGS is a resonant
gap or slot in the ground metal, placed directly
under a transmission line and aligned for
efficient coupling to the line. Figure 1 shows
several resonant structures that may be used.
Each one differs in occupied area, equivalent
L-C ratio, coupling coefficient, higher-order
responses, and other electrical parameters. A
user will select the structure that works best
for the particular application.
The equivalent circuit for a DGS is a parallel-
tuned circuit in series with the transmission
line to which it is coupled [1] (see Figure 2). The
input and output impedances are that of the
line section, while the equivalent values of L, C
and R are determined by the dimensions of the
a microstrip (or stripline, or coplanar waveguide)
circuit is intentionally modified to
enhance performance.
The name for this technique simply means
that a “defect” has been placed in the ground
plane, which is typically considered to be an
approximation of an infinite, perfectly-conducting
current sink. Of course, a ground
plane at microwave frequencies is far removed
from the idealized behavior of perfect ground.
Although the additional perturbations of DGS
alter the uniformity of the ground plane, they
do not render it defective.fected Ground Structures