06-11-2012, 05:19 PM
BANDWIDTH ENHANCEMENT OF MICROSTRIP ANTENNA
[attachment=38337]
Abstract
A novel microstrip antenna with wide bandwidth is
presented. Two different radiating elements connected together
through a matched section and are embedded on a single layer
structure. This new structure offers a dual-band microstrip antenna.
By controlling the two resonance frequencies of the two elements, a
wide frequency bandwidth of approximately 9% has been achieved.
A more bandwidth enhancement, up to 12%, has been achieved by
adding two parasitic elements to one element of the proposed antenna.
Fabrication and measurement of S11 for the proposed antenna has been
done. The measured results have been compared with the simulated
results using commercial software HFSS version-8.0.
INTRODUCTION
Microstrip Patch Antennas (MPA) are extremely attractive candidates
for use in many applications due to their interesting features such as
low cost, light weight, thin profile and conformability. On the other
side, the greatest disadvantage of MPA is its low bandwidth which
can be as low as 1% [1]. The most straightforward way to improve
the MPA bandwidth is to increase the patch-ground plane separation
by using a thicker substrate [2]. Unfortunately, the thick substrate
will support surface wave modes that will increase mutual coupling in
antenna arrays [3]. Mutual coupling will result in serious degradations
in impedance mismatch, large radiation loss, polarization distortion
and scan blindness in phased array antennas [4, 5].
DUAL-BAND MPA DESIGN
In this section, a novel dual-band MPA is described where two different
radiating elements connected together through a matched section and
is embedded on a single layer structure as shown in Figure 1. The first
element is a rectangular MPA with frequency f1 controlled by patch
dimensions L, and W and the second element is a printed dipole with
frequency f2 controlled by the dipole dimensions Ld, and Wd. The
structure is fed by a coaxial probe through the dipole element which is
direct coupled to the MPA by a quarter wave length matched section
with width Wm, and length Lm [2]. The computer simulation is done
using the commercial software HFSS version-8.0 with the fixed design
structure parameters given in Table 1 for a resonant frequency f1 of
the rectangular MPA at 10 GHz [1]. The simulated results are given in
Table 2 which shows that as the dipole length Ld increases, its resonant
frequency f2 get closer to the MPA resonant frequency f1 with slightly
decrease in the later resonant frequency. The simulated results of S11
for the antenna shown in Figure 1 are given in Figure 2 for only three
values of Ld (20, 24, and 28 mm).
CONCLUSION
Simulations and measurements on the new proposed antenna
configuration have provided a useful design for a wide bandwidth
MPA of 9%, or with a controllable frequency separation of the two
frequencies of the dual-element with f2/f1 = 1.38 : 1 for the given
construction. A 12% bandwidth enhancement has been achieved
with the two parasitic elements. With the simplicity of feeding
and fabrication, the investigated wide bandwidth antenna is a good
candidate for many wireless communications.
[attachment=38337]
Abstract
A novel microstrip antenna with wide bandwidth is
presented. Two different radiating elements connected together
through a matched section and are embedded on a single layer
structure. This new structure offers a dual-band microstrip antenna.
By controlling the two resonance frequencies of the two elements, a
wide frequency bandwidth of approximately 9% has been achieved.
A more bandwidth enhancement, up to 12%, has been achieved by
adding two parasitic elements to one element of the proposed antenna.
Fabrication and measurement of S11 for the proposed antenna has been
done. The measured results have been compared with the simulated
results using commercial software HFSS version-8.0.
INTRODUCTION
Microstrip Patch Antennas (MPA) are extremely attractive candidates
for use in many applications due to their interesting features such as
low cost, light weight, thin profile and conformability. On the other
side, the greatest disadvantage of MPA is its low bandwidth which
can be as low as 1% [1]. The most straightforward way to improve
the MPA bandwidth is to increase the patch-ground plane separation
by using a thicker substrate [2]. Unfortunately, the thick substrate
will support surface wave modes that will increase mutual coupling in
antenna arrays [3]. Mutual coupling will result in serious degradations
in impedance mismatch, large radiation loss, polarization distortion
and scan blindness in phased array antennas [4, 5].
DUAL-BAND MPA DESIGN
In this section, a novel dual-band MPA is described where two different
radiating elements connected together through a matched section and
is embedded on a single layer structure as shown in Figure 1. The first
element is a rectangular MPA with frequency f1 controlled by patch
dimensions L, and W and the second element is a printed dipole with
frequency f2 controlled by the dipole dimensions Ld, and Wd. The
structure is fed by a coaxial probe through the dipole element which is
direct coupled to the MPA by a quarter wave length matched section
with width Wm, and length Lm [2]. The computer simulation is done
using the commercial software HFSS version-8.0 with the fixed design
structure parameters given in Table 1 for a resonant frequency f1 of
the rectangular MPA at 10 GHz [1]. The simulated results are given in
Table 2 which shows that as the dipole length Ld increases, its resonant
frequency f2 get closer to the MPA resonant frequency f1 with slightly
decrease in the later resonant frequency. The simulated results of S11
for the antenna shown in Figure 1 are given in Figure 2 for only three
values of Ld (20, 24, and 28 mm).
CONCLUSION
Simulations and measurements on the new proposed antenna
configuration have provided a useful design for a wide bandwidth
MPA of 9%, or with a controllable frequency separation of the two
frequencies of the dual-element with f2/f1 = 1.38 : 1 for the given
construction. A 12% bandwidth enhancement has been achieved
with the two parasitic elements. With the simplicity of feeding
and fabrication, the investigated wide bandwidth antenna is a good
candidate for many wireless communications.