06-08-2013, 03:13 PM
Reduction of Sidelobes by Non-uniform Elements Spacing
[attachment=57021]
Abstract
The unwanted side effect of EBG structures when
integrated with microstrip antenna is investigated in this
paper. The main goal of using EBG structures in microstrip
antenna is to achieve better gain and efficiency, lower side-
lobes and back-lobes levels, and better isolations among array
elements, by suppressing surface wave modes. The two
dominating side effects may be named as parasitic loading
effect and cavity effect. The parasitic loading effect of EBG
structure causes the multi resonance antenna resulting in
larger bandwidth. Cavity effect on the other hand, is due to
reflecting energy from EBG toward antenna and results in a
larger Q value and so decreasing the bandwidth. These two
side effects are characterized in this work and the EBG
structure parameters and number of EBG rows is related to
these effects. The design parameters of EBG structures can be
managed such that the parasitic effect of EBG structure can
be the dominating effect and consequently results in larger
bandwidth.
INTRODUCTION
With the rapid growth of wireless markets, microstrip
antennas became more attractive in antenna community. These
antennas are low-profile, low cost and light weight. However,
Surface waves are a major drawback for this type of antenna
as they lower the antenna efficiency. A narrow impedance
bandwidth is another limitation of patch antennas. Two
techniques have been used to suppress surface wave
propagation, namely micromachining and periodic structures
called the electromagnetic band gap (EBG) structures [3{6]. In
microstrip antennas, EBG structures surrounding patch
element to suppress surface waves to achieve better side lobe
and back lobe levels and increased radiation efficiency. It has
been shown in article that, placing EBG cells in E-plane is
sufficient for surface wave reduction and it is not required to
have H-plane EBG cells.
CONCLUSIONS AND SUMMARY
In this paper, the unwanted side effects of EBG structures
which integrated with microstrip antenna is investigated by
using parametric analysis. Based on the results obtained in
this work, the following can be concluded from the
parametric analysis:
1) Increasing the EBG rows results in lower side and back
radiation and so better radiation efficiency in the cost of
antenna size enhancement.
2) As EBG rows increased from one to four rows, parasitic
effect is dominant, but bandwidth improvement is
negligible.
3) As EBG rows increases beyond 4 rows, cavity effect
becomes dominant and bandwidth suddenly decreases.
[attachment=57021]
Abstract
The unwanted side effect of EBG structures when
integrated with microstrip antenna is investigated in this
paper. The main goal of using EBG structures in microstrip
antenna is to achieve better gain and efficiency, lower side-
lobes and back-lobes levels, and better isolations among array
elements, by suppressing surface wave modes. The two
dominating side effects may be named as parasitic loading
effect and cavity effect. The parasitic loading effect of EBG
structure causes the multi resonance antenna resulting in
larger bandwidth. Cavity effect on the other hand, is due to
reflecting energy from EBG toward antenna and results in a
larger Q value and so decreasing the bandwidth. These two
side effects are characterized in this work and the EBG
structure parameters and number of EBG rows is related to
these effects. The design parameters of EBG structures can be
managed such that the parasitic effect of EBG structure can
be the dominating effect and consequently results in larger
bandwidth.
INTRODUCTION
With the rapid growth of wireless markets, microstrip
antennas became more attractive in antenna community. These
antennas are low-profile, low cost and light weight. However,
Surface waves are a major drawback for this type of antenna
as they lower the antenna efficiency. A narrow impedance
bandwidth is another limitation of patch antennas. Two
techniques have been used to suppress surface wave
propagation, namely micromachining and periodic structures
called the electromagnetic band gap (EBG) structures [3{6]. In
microstrip antennas, EBG structures surrounding patch
element to suppress surface waves to achieve better side lobe
and back lobe levels and increased radiation efficiency. It has
been shown in article that, placing EBG cells in E-plane is
sufficient for surface wave reduction and it is not required to
have H-plane EBG cells.
CONCLUSIONS AND SUMMARY
In this paper, the unwanted side effects of EBG structures
which integrated with microstrip antenna is investigated by
using parametric analysis. Based on the results obtained in
this work, the following can be concluded from the
parametric analysis:
1) Increasing the EBG rows results in lower side and back
radiation and so better radiation efficiency in the cost of
antenna size enhancement.
2) As EBG rows increased from one to four rows, parasitic
effect is dominant, but bandwidth improvement is
negligible.
3) As EBG rows increases beyond 4 rows, cavity effect
becomes dominant and bandwidth suddenly decreases.