In this paper, an electromagnetically coupled two pair-slanted slot microstrip antenna (SSMSA) is presented to achieve multi-frequency operation with adequate impedance bandwidth and circular polarization (CP). The design consists of two pairs of slanted slots etched on the ground plane of the top surface of the substrate material and are excited by back microstrip line-feed which is placed at the bottom surface of the substrate material. This antenna operates at four bands of frequencies within X-band and shows the property of CP with minimum axial ratio. Such antennas can find application in satellite and radar communication systems.
Microstrip
antennas have a number of useful and interesting applications
in microwave communication systems. But the most serious limitation
is the narrow impedance bandwidth that resonates at single
frequency. Nowadays, the microstrip antennas have become quite
popular because of their properties such as low profile, lightweight,
compactness, conformable in structure and ease in fabrication.
Despite the narrow impedance bandwidth and efficiency, the
microstrip antenna will find potential application in various
diversified fields, especially, in high-speed space vehicles,
missiles, tanks and other strategic defense equipment. But
the microstrip antennas having multi-frequency operation and
circular polarization (CP) may find more useful applications
for this equipment. However, the multi-frequency operation
and CP property can be achieved with corrugated horn, dielectric
resonator antenna, helical antenna and slotted waveguide antenna,
etc., [1-4]. But these antennas are bulky, bigger in size
and cost more for their fabrication. It has been reported
that by loading a slot in microstrip patches of various shapes
[5-7], microstrip patch antennas can be operated at two or
more different frequencies. One resonant frequency is due
to the fundamental mode of the main patch; the others are
due to the fact that current along the edges of the slot introduce
an additional resonance [8]. CP is often the preferred choice
in satellite, radar, navigation and communication systems.
Here, the general limitation of the circularly polarized patch
antenna is its limited bandwidth. Various techniques have
been described in the literature, which can be used to generate
CP from microstrip antennas namely, aperture fed truncated
square patches, notches etched on circular patches [9], and
crossed slots [10]. In all these cases, the usable impedance
bandwidth is narrow. In view of this, we are presenting a
two pair-slanted slot microstrip antenna (SSMSA) for multi-frequency
operation with adequate bandwidth and CP property. |
