Fig.4 shows the geometry and dimension of the UWB
antenna with band-notch characteristic from 5.04-5.81 GHz
band (denoted as antenna 2). By removing an U-shaped slot
from the stair cased rectangular-radiating patch of antenna 1, a
band notch function is created. It is noteworthy that when the
band-notched structure is applied to the antenna 1, there is no
redesigning work needed for the previously taken dimensions.
In general, the main aim behind the design methodology of the
notch function is to tune the total length of the U-shaped slot
approximately equal to the half guided wavelength (λg) of the
desired notch frequency, which provides the input impedance
singular. At the desired notch frequency, the current
distribution is around the U-shaped slot. Hence, a destructive
interference for the excited surface current will occur, which
causes the antenna to be non-responsive at that frequency.