ChapterPDF Available
Performance Enhancement of Rectangular
Microstrip Antenna by Inserting Notches
and Slits
Raj Gaurav Mishra, Ranjan Mishra, Piyush Kuchhal and N.Prasanthi Kumari
1 Introduction
In recent years, the wireless communication society has been grown very rapidly.
Antenna, as one of key components, nds an intensive research and development to
sustain the growth. In communication using wireless systems, the information
signals are radiated in space as an electromagnetic wave by using an antenna and
the radiated signal is intercepted by a receiving antenna. An antenna serves as a
device that is used for radiating or receiving electromagnetic waves [1].
Microstrip antennas, being the one of the suitable and useful for this, nd many
hopeful claims in this area [2]. Its utility and usefulness lies in its potential attractive
features [3]. However, the wide use is also restricted by its low bandwidth (around
5%) and low efciency. This main disadvantage of microstrip antenna possesses its
inadequacy for various wideband applications nowadays. In its simple form, a
microstrip antenna comprises of a radiating patch and a ground plane, both are of
conductor, along with a dielectric substrate in between them. The shape of the upper
surface is of various regular geometrical forms. Recently, various methods have
reported for improving the performance of the impedance bandwidth of microstrip
antenna. The report includes the effect by inserting slots on the radiating structure
[47]. Besides these parasitic element [8], partial ground plane [9], open-loop
resonator effect [10] are also reported. Recently, researchers included broadband
optimization by inserting slot on planer rectangular antenna [11,12].
The outline of the paper is comprised of four sections: The introduction is
presented in Sect. 1; Sect. 2is regarding the antenna structure and its dimension; a
R. G. Mishra (&)R. Mishra N. Prasanthi Kumari
Department of Electronics, Instrumentation and Control, CoES,
University of Petroleum and Energy Studies, Dehradun, India
P. Kuchhal
CoES, University of Petroleum and Energy Studies, Dehradun, India
©Springer Nature Singapore Pte Ltd. 2018
N. A. Siddiqui et al. (eds.), Advances in Health and Environment Safety,
Springer Transactions in Civil and Environmental Engineering,
brief analysis of the impedance calculation antenna is carried out in Sect. 2; results
are discussed in Sect. 3, and the conclusion is carried out in Sect. 4.
2 Antenna Structure and Design
The structure of the rectangular antenna is dependent on three parameters. These are
operating frequency (f), dielectric constant of the substrate material (e
), and its
height (h). In the present discussion, the mid-operating frequency is 8 GHz,
dielectric constant of the FR4 epoxy substrate is 4.4, and the height is 1.6 mm. The
upper range in the height of the substrate is taken because this adds on the band-
width and also avoids any bulkiness in the structure of the antenna [13]. Length and
width of the rectangular antenna are calculated by the set of equations [1,2].
Consider the impedance matching with the line, the length and width are come out
to be 12 and 16 mm, respectively, after slight optimization. The analysis is per-
formed in advanced design software (ADS) using method of moment.
In this present study, the inductive effect is done by inserting notches and slits on
the radiating structure. These have been sliced out normal to the axis of resonating
length. The notches are the structure at the corners, and the slits are over the length.
The structure of them is also rectangular in shape. The analysis is carried out by
varying the dimensions of these structures, and in the report, the suitable size is kept
which present the best result. The dimension of these structures is symmetrical in
nature. The dimensions of notches and slits are 2 mm by 0.5 mm. The feeding to
the antenna is provided by microstrip line having a 50 Xload for good impedance
matching. A symbolic structure of the antenna with notches and slits are shown in
Fig. 1.
Fig. 1 Planer structure of rectangular microstrip antenna with anotches and bslits
392 R. G. Mishra et al.
3 Results and Discussion
The effect of notches and slits on the microstrip antenna is observed and analyzed
separately with reference to the plain microstrip antenna of same dimensions. The
microstrip antenna is of dimension 15 mm 12 mm 1.5 mm with FR4 epoxy
substrate and is fed with microstrip line of dimension 12 mm 4 mm. This
feeding is the most suitable for compact structure [3]. The plain structure gives a
low return loss of the order of 20% and bandwidth of 19%. The next observation
and analysis is with notches. A notch is a small grove cut along the corner of the
edge. A symmetrical notch structure is chosen. The most signicant result is
observed with four notches at four corners. The dimension of each symmetrical
notch is 2 mm 0.5 mm. The impedance bandwidth has been signicantly
enhanced to 37% with this. This rise in bandwidth is quite noteworthy. Also the
return loss has been in excess of 30 dB. Return loss plot (S
plot) with this
structure is shown in Fig. 2. The maximum of return loss is at the frequency of
8 GHz with the 10 dB bandwidth of 1.5 GHz.
The nal analysis is done by observing the effect of slits on the radiating surface.
Here, the best result is obtained with four symmetrical slits, two each on the
radiating edges of the antenna. Here too, a good return loss and increases in the
bandwidth with respect to planer structure is obtained. Also the slit shifts the central
frequency to around 9 GHz; this is due to slight overall change in the radiating
dimension of the antenna.
The S
(return loss) plot with both notches and slits is shown in Fig. 2. In both
cases, with notches and slits, an enhancement in the return loss and bandwidth is
achieved with respect to the planer structure. Only the gain is marginal low and this
Fig. 2 Return loss plot showing bandwidth
Performance Enhancement of Rectangular 393
reduction in gain is due to the increase in the bandwidth. A summarization and
comparison with various parameters is shown in Table 1.
The current distribution over the patch with notches and slits is shown in Fig. 3
Fig. 3reveals that a noteworthy amount of current is present at the junction
portion of radiating surface of the microstrip antenna and the microstrip line. In case
of slit-loaded antenna, current ow is minimum at the corners of the edges, and the
same low current is along the non-radiating far edge of the antenna. But with the
introduction of notches, it is found that in the junction point, there is a drop in the
distribution of the current ow, whereas it increases at the four edges. This results a
better impedance matching and ultimately and enhancement in the bandwidth and
good return loss with notches. There is a weak current ow at the edges with the
slits, but it is high at the portion where the slits engraved the radiating portion.
Therefore, an introduction of small slit of proper length increases the ow of current
over the radiating portion of the antenna. This causes an enhancement in the
bandwidth and the return loss. This enhancement is more than the plain structure
but slight less than with the notches. The radiation pattern for the two aforesaid
cases is shown in Fig. 4.
The radiation pattern reveals a broad distribution of the energy on the two side
lobes. Since the gain with notches and slits is more than those obtained with planar
structure, an identical radiation pattern is observed.
Table 1 Performance
parameter with different
Plain Notch Slit
Efciency 28.71 37.31 34.48
Directivity (dB) 7.47 7.41 7.42
Gain (dB) 2.37 2.08 1.92
Bandwidth (%) 19 37 37
Fig. 3 Current distribution in aplain microstrip antenna bnotches loaded microstrip antenna
cslits loaded microstrip antenna
394 R. G. Mishra et al.
4 Conclusions
The rectangular microstrip antenna has been analyzed with the insertion of sym-
metrical notches and slits on the radiating surface. It is established that there is an
enhancement in the performance of the antenna parameter especially the bandwidth
up to the order of 37%. It has also seen that the insertion of notches has more
profound effect than the slits. Hence, it is concluded that an appropriate selection of
the dimension and position of the notches and slits effectively enhanced the per-
formance and the antenna can be a good choice for various wideband applications
in the lower frequency range of X-band and nds useful application in earth
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Fig. 4 Radiation pattern of aplain microstrip antenna bnotches loaded microstrip antenna cslits
loaded microstrip antenna
Performance Enhancement of Rectangular 395
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... Microstrip antennas have certain restrictions like polarization problems, low gain, single operating frequency, low impedance bandwidth, and narrow bandwidth [2]. There are some techniques which have improved the performance capabilities of antenna parameters, which are fractal geometry [3], metamaterial [4][5][6][7], array configuration [8], Electromagnetic Band Gap structures (EBGs) [9], Substrate Integrated Waveguides (SIWs) [10], Defected Ground Structures (DGSs) [11,12], different feeding techniques [13], multilayer antennas [14], Defected Microstrip Structures (DMSs) [15], Frequency Selective Surfaces (FSSs) [16], W shape slots, M-slots, and eight shape with proper location in a patch [17][18][19], and distinctive shapes or a combination of them are inserted as slits and notches on the surface of the patch to enhance the performance of a antenna [20]. The equivalent circuit of a DGS is composed of a tuned parallel LC resonating circuit which is series with a microstrip line. ...
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