The use of discontinuities in ground planes or in microstrip
lines is currently employed to improve the performance of
different passive circuits, such as the size reduction of
amplifiers, the enhancement of filter characteristics[4][11]
and applications to suppress harmonics in patch antennas.
On the other hand, a new proposal, called defected
microstrip structure (DMS)[9], has been successfully used
in reducing the size of, and as a tuning technique for,
rectangular patch antennas The DMS is similar to the
structure called spurline. The spurline is a type of radiofrequency
and microwave distributed element filter with
band-stop (notch) characteristics, most commonly used with
microstrip transmission lines. Spurline usually exhibit
moderate to narrow-band rejection, at about 10% around the
central frequency. Since both are etched in the microstrip
line and behave as stop-band filters [12][13]. The main
difference, however, is that DMS achieves a greater
associated inductance. DMS also presents a greater slowwave
effect, since it has more discontinuities, providing a
longer trajectory to the electromagnetic wave.
Simultaneously, DMS also performs a greater stop-band
bandwidth compared to spurline, both having the same
dimensions. The use of DMS allows an increase in the slowwave
factor (SWF) in transmission lines in which they are
introduced. This phenomenon can be used to reduce the size