It is widely known that the use of microstrip antennas is often limited by its
low bandwidth. Several schemes have been suggested to improve the bandwidth of
these antennas, including the use of (i) stacked dielectric arrangement, usually with
multiple metal layers; (ii) slots of various shapes on the patch
[1]; (iii) meandered probe feed [5];
or (iv) capacitively-coupled feed [2, 6]. While some of these were indeed easy to
fabricate, they do not offer enough bandwidth required in several applications. Others like
stacked arrangements with multiple layers provide good bandwidth. However, they occupy more
space. Guo et al .[3] have used many techniques, including the use of high-dielectric substrate,
short circuit and shorting pin, to miniaturize the antenna. Recently, Deshmukh and Kumar [1]
have shown that the size of the patch antennas can be reduced by using either T or
P shaped slots in the patch [1].
In this paper, we present a comparative study of Compact Stacked Rectangular
Microstrip Antenna (CSRMSA) with a pair of T-slots. Here, three types of CSRMSA are studied
and compared, i.e., CSRMSA with embedded T-slots in (a) lower patch (CSRMSA-TLP);
(b) upper patch (CSRMSA-TUP); and (c) both lower and upper patches
(CSRMSA-TLUP). These antennas are fabricated on glass epoxy substrate and are
fed using co-axial probe feed. The total height of the
stacked configuration in all three cases is very small, i.e., h = h1 + h2 = 3.2 mm. Here, all the antennas
are first simulated using Zeland IE3D software package version 12.1,
and an experimental verification is made with Vector
Network Analyzer. For the simulation of all the microstrip antennas,
an infinite ground plane has been assumed. However, for
the measurement of return loss, Voltage Standing Wave
Ratio (VSWR), input impedance and radiation pattern, the size of
the ground plane is taken more than six times the substrate
thickness in all directions with respect to the fed patch dimensions in
order to reduce the effect of the finite ground plane [4]. |
