This paper presents a novel design of edge slot rectangular
microstrip antennas for wide impedance bandwidth. The effect
of slot in enhancing the impedance bandwidth is studied
by placing the slot at the edges of Rectangular Microstrip
Antenna (RMSA). The placement of four slots at all the edges
of RMSA reduces the overall size of antenna by 44.89% when
compared to the size of conventional RMSA. This compact
microstrip antenna gives an impedance bandwidth of 12.27%
and gain of 6.12 dB at X-band, which are 4 and 1.66 times
respectively more than the impedance bandwidth and gain
of conventional RMSA without changing broadside radiation
characteristics. These compact and wideband antennas may
find application in high frequency WLAN and mobile computing
networks.
In applications where size, weight, cost, performance,
ease of installation and aerodynamic profile are constraints,
low profile antennas like microstrip antennas are required.
Microstrip antennas have a number of useful properties but
one of the serious limitations of these antennas has been
their narrow impedance bandwidth characteristic. The impedance
bandwidth of a conventional microstrip patch is less than
1% to several percent for thick substrates [1]. Various
techniques are available in the literature for broadening
the impedance bandwidth of microstrip antennas. These include:
use of feeding technique, use of thicker dielectric substrates,
use of parasitic element gap-coupled to the radiating element,
incorporating slot, etc. The slot technique is simple and
straightforward in enhancing the impedance bandwidth of
microstrip antennas as compared to other techniques available
in the literature [2]. This technique has the freedom to
add a desired slot in the radiating element of microstrip
antenna for enhancing the impedance bandwidth. However,
the addition of slot does not change the overall size of
the antenna. Therefore, in this study, the slots are added
at the edges of RMSA in order to reduce its size and achieve
wide impedance bandwidth. These slots are considered as
wide slots as their width is comparable to their length.
The wide slots are selected because they are more effective
in enhancing the impedance bandwidth than the narrow slots
[3]. The study is carried out rigorously by placing wide
slots at the possible edges of RMSA to get the maximum impedance
bandwidth at X-band frequencies (8 to 12 GHz).
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