13-03-2012, 03:38 PM
A NEW REDUCED SIZE MICROSTRIP PATCH ANTENNA WITH FRACTAL SHAPED DEFECTS
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Abstract—With development of communication with integration
technology, size reduction of microstrip antennas is becoming an
important design consideration for practical applications. Here a new
microstrip antenna with Koch shaped fractal defects on the patch
surface is presented. Using this method, the overall electric length
of the antenna is increased largely and hence the size of antenna is
reduced to 85%, compared to an ordinary microstrip antenna with the
same resonance frequency. Antenna is simulated using high frequency
structure simulator (HFSS) V.10 which is based on finite element
modeling (FEM). Finally antenna is fabricated on RO4003 substrate.
Measurement results are in good agreement with simulated results.
INTRODUCTION
Microstrip antennas are investigated vastly due to their properties,
such as lowprofile, lowcost, conformability and ease of integration
with active devices. The size of antenna is extremely important
for most wireless communication systems. But it is desired that
the reduced size antenna have equivalent operation in comparison
with ordinary developed antennas. There are limits to how small an
antenna can be, however the most important of them are bandwidth
and gain. Fortunately a lot of communication systems don’t require
large bandwidths; therefore, it is not an important problem.
ANTENNA GEOMETRY AND OPERATION
MECHANISM
Here a newreduced size microstrip antenna with ultra lowprofile
features is presented. This antenna configuration is shown in Fig. 1.
The patch has dimensions of W × L. The RO4003 substrate which
has a relative permittivity εr = 3.38 and thickness 0.762mm (30 mil)
is used. The ground plane dimensions are Wg × Lg = 10cm×10 cm.
The antenna is fed by a microstrip line with characteristic impedance
50Ω and width Wf = 1.7 mm, that is placed at the center of the patch
Progress In Electromagnetics Research B, Vol. 11,200931
radiating edge. Four fractal defected microstrip structures (DMS) are
excoriated from the patch’s surface. The lengths of these DMS’s are
Ld and their width are Wd, and all have the same dimensions. These
DMS’s are placed at equal distances from each other. Table 1 shows
the designed dimensions that are used for the antenna.
MEASUREMENT RESULTS
Finally antenna is fabricated and tested. The following measurement
results showa good agreement with the simulations. The fabricated
prototype is shown in Fig. 6. The measured radiation pattern is shown
in Fig. 7. Back lobe in radiation pattern is because of small ground
plane.
