International Journal of Electronics Engineering Research.

ISSN 0975-6450 Volume 9, Number 7 (2017) pp. 957-969

© Research India Publications

http://www.ripublication.com

Designing Of Slotted Microstrip Patch Antenna Using

Inset Cut Line Feed For S, C And X Band

Applications

Navpreet Kaur

M.Tech Scholar

Department of Electronics & Communication Engineering,

Amritsar College of Engineering & Technology, Amritsar

Narinder Sharma

Associate Professor

Department of Electronics & Communication Engineering,

Amritsar College of Engineering & Technology, Amritsar

Abstract

The paper explicate an optimal design of multiband slotted Microstrip Patch

Antenna with etched slots for wireless applications. To accomplish multiband

frequency, proposed finite element method is employed to design the

rectangular Microstrip Patch Antenna (MPA). The rectangular shapes and a

circular slots are etched from the patch to improve the gain of antenna. It is

observed that gain is increased by increasing number of iterations. In the final

iteration, the proposed patch antenna can resonate at five unique frequencies

between 2 GHz and 9GHz and exhibits the gain of 1.07dB, 2.53dB, 5.94dB,

6.2dB and 9.3dB at 2.81GHz, 5.81GHz, 7.81GHz, 8.00GHz and 8.72GHz

respectively. The performance parameters like Return loss and gain for different

iterations are adhered and explained in this paper. The return loss for all the

resonant frequencies is less than -10 dB . This antenna can be used for wireless

applications like wireless broadband transceiver which is applicable to fixed

Wi-MAX, 802.16e, mobile Wi-MAX, 4G LTE system, GSM ,CDMA ,

958 Navpreet Kaur and Narinder Sharma

Bluetooth, transmitter design for 802.16, fixed CPE, Femto BTS,WLAN access

point. The (HFSS V13) High Frequency Structure Simulator is used to simulate

the proposed antenna. The proposed antenna is also fabricated and then tested

using VNA (Vector Network Analyzer) which shows that experimental results

are in a reasonable agreement with the simulated results.

Keywords: MPA, VNA, HFSS, Return loss

1. INTRODUCTION

A Microstrip Patch Antenna (MPA) comprises of metallic patch radiator on an

electrically thin dielectric substrate with the ground of metallic material such as copper,

gold. Now-a-days the need of wireless communication is in great demand

Nomenclatures

c Speed of light

fr Resonant frequency that is equal to 5 GHz

h Height of patch

w Width of patch

L Resonant length

Leff Effective length of patch

Greek Symbols

εreff Effective dielectric constant

𝜆 Wavelength of free space

𝜆 Wavelength of PC Board

εr Dielectric constant

Abbreviations

MPA Microstrip Patch Antenna

[1][2], and an antenna is the backbone of this system. Among various available

antennas, MPA is the major attraction for researchers over the last decades. The

microstrip patch structures are probably easy to fabricate. Research on microstrip

antenna in the 21st century centred at small sized, increased gain, wide bandwidth,

multiple functionality [3][4]. With the wide spread proliferation of wireless

Designing Of Slotted Microstrip Patch Antenna Using Inset Cut Line Feed… 959

communication technology in recent years, the importunity for compact, low profile

and broadband antennas has escalated significantly. To meet such features and

requirements, the MPA has been proposed because of its low profile, less cost and small

size. MPA consists of rectangular patch which is conductor in nature of length "L" and

width "W" on one side of dielectric substrate with the thickness of "h" and dielectric

constant "εr" with the base named ground. Commonly available shapes of microstrip

antenna are circular , elliptical , square, rectangular, but any other shape can also be

introduced by using regular shapes. The performance of antenna can be evaluated on

the basis of return loss, gain, bandwidth and VSWR. Return loss or reflection loss is

the reflection of signal power from the insertion of a device in a transmission line or

optical fibre [5]-[8]. Whereas, antenna gain is the ratio of maximum radiation intensity

at the peak of main beam to the radiation intensity in the same direction produced by

an isotropic radiator or omni - directional antenna having the same input power.

Isotropic antenna is standardised to have a gain of unity. Various feeding mechanisms

can be used to excite Microstrip patch antennas. These techniques are categorised as

contacting and non-contacting technique. The contacting techniques are microstrip line

feeding and co-axial plane feeding [9]. On other hand, non- contacting techniques are

proximity coupled feeding, aperture coupled feed. In this paper, Slotted MPA with

inset-cut microstrip line feed technique has been introduced, the main benefits of this

antenna is that it is reliable and easy to fabricate [10]-[12].

2. ANTENNA DESIGN AND CONFIGURATION

In order to design slotted antenna, dimensions are chosen on the basis of frequency.

Square patch of dimension 37×24 mm2 is taken. FR-4 epoxy is used as substrate with

loss tangent of 0.02 and di electric constant of 4.4 with ground plane is of 55×35.5 mm2

size. Length and width of patch is calculated by using following equations:

W = 𝑐

2𝑓𝑟√

2

𝜖𝑟+1 (1)

Where 𝜖𝑟 is relative permittivity, 𝑓𝑟 is the resonant frequency and c is the velocity of

light, and the calculated W is 24mm. The effective dielectric constant of the microstrip

antenna is determined using:

𝜀𝑟𝑒𝑓𝑓 = 𝜀𝑟+1

2 +

𝜀𝑟−1

2[1 + 12

ℎ

𝑊]−

1

2 (2)

Calculation of the length extension (ΔL)

∆𝐿 =0.412h (𝜀𝑟𝑒𝑓𝑓+0.3)(

𝑊

ℎ+0.264)

(εreff−0.258)(𝑊

ℎ+0.8)

(3)

960 Navpreet Kaur and Narinder Sharma

Calculation of the Effective length ( Leff)

𝐿𝑒𝑓𝑓 = 𝐶

2𝑓𝑜√𝜀𝑒𝑓𝑓 (4)

Calculation of actual length of patch (L)

L = 𝐿𝑒𝑓𝑓 + ΔL (5)

The calculated value of L is 37mm

Table 1: Dimensions of Proposed antenna

PARAMETERS VALUES (mm)

Patch length (L) 37

Patch Width (W) 24

Insert fed gap (IG) 4

Insert fed distance (ID) 3.5

Feed Width (FW) 4.5

Feed Length (FL2) 7

Feed Length (FL3) 3.5

Ground length(GL) 55

Ground width(GW) 35.5

Height (H) 1.6

Diameter of circle (D) 10

Slotted rectangle area (A1s) 6×3

Slotted rectangle area (A2s) 5×5

Slotted circle’s diameter in 3rd iteration (d) 4

Designing an antenna in wireless application means that the antenna dimensions should

be small. Keeping this under consideration, design cogitation was taken from

broadband antennas with inset feed line technique.

Designing Of Slotted Microstrip Patch Antenna Using Inset Cut Line Feed… 961

Figure 1: 0th Iteration of Proposed Antenna

This is a type of microstrip line feeding technique, in which the width of conducting

strip is kept bantam as analogize to the patch and has the advantage that the feed can

provide a planar structure [13]. To avoid the need for any additional matching element

and enhance the performance parameters of antenna the inset-cut is introduced in the

patch as shown in Figure 1. The impedance matching can be attained by properly

acclimating the inset cut position and dimensions [14] [15], and can be treated as 0th

Iteration as shown in Figure 1.

Figure 2: 1st Iteration of Proposed Antenna

1st iteration is derived from 0th iteration by cutting slots area of patch . The circular

patch with diameter of 10 mm and rectangular slots with dimension of 6×3 mm2 is

introduced in the structure shown in Figure 2. which is helpful to enhance the gain and

S11 parameter.

962 Navpreet Kaur and Narinder Sharma

Figure 3: 2nd Iteration of Proposed Antenna

To further enhance the performance parameters the square shaped rectangular slot at

centre with the dimension of 5×5 mm2 has been introduced where, circular slot is

replaced by square shaped slot in the 2nd iteration to enhance gain of antenna. 2nd

iteration is attained from the 1st iteration by replacing the circular slot with the square

shaped slot.

Figure 3: 3rd Iteration of Proposed Antenna

In the 3rd iteration, 2nd iteration is considered as base design and six circular slots with

diameter 4mm are etched to improve gain of antenna. This is the finalised iteration as

Designing Of Slotted Microstrip Patch Antenna Using Inset Cut Line Feed… 963

the complexity of design increases with increase in number of iterations and it would

be cumbersome to fabricate the required antenna.

3. RESULTS AND DISCUSSION

The simulation results are carried out to test the performance of proposed patch antenna.

The simulation results of return losses versus frequency curves of 0th,1st, 2nd and 3rd

iteration of proposed antenna are discussed in Figure 4. Moreover return loss, VSWR,

Bandwidth and Gain for various resonant frequencies is given in Table 2. The outcome

of simulated results of return loss and gain confirms the optimal performance of the

proposed design of antenna.

Figure 4: Return loss v/s frequency curve of the proposed antennas

Maximum Gain of 0th Iteration at 8.9 GHz Maximum Gain of 1st Iteration at 8.72GHz

964 Navpreet Kaur and Narinder Sharma

Maximum Gain of 2nd Iteration at 2.90GHz Maximum Gain of 3rd Iteration at 8.72 GHz

Figure 5: 3D Maximum Gain Plots at various Resonant Frequencies

Gain is the significant parameter of antenna as it disports the directional capabilities

and efficiency of antenna. Gain above 3dB is prominent to make antenna work

effectually. The 3-D gain plot at resonant frequency of 5 GHz for 0th iteration, 1st

iteration, 2nd iteration and 3rd iteration of antenna is delineated in Figure5. The

maximum value of gain for 0th iteration, 1st iteration, 2nd iteration and 3rd iteration is 8.9

dB, 4.9 dB, 8.7 dB and 9.3 dB respectively.

Figure 6: VSWR of the proposed antennas

Voltage Standing Wave Ratio (VSWR) depicts the impedance matching of the antenna.

It is the measure of impedance mismatch between the antenna and feed line. For

practical use of antenna, it is required that value of VSWR should always be less than

or equal to 2.

The VSWR V/s frequency curves for 0th Iteration, 1st iteration, 2nd iteration and 3rd

iteration are shown in Figure 6, and the values of VSWR for all the iterations are shown

in Table 2. Moreover comparison of return loss and gain for various resonant

frequencies is given in Table 3. In this design return loss of -19.06 dB is achieved at

resonant frequency of 8.72 GHz.

Designing Of Slotted Microstrip Patch Antenna Using Inset Cut Line Feed… 965

Table 2: Return losses, gain, bandwidth and VSWR for various frequencies and their

uses in particular bands

Iteratio

n

Resonanc

e

frequency

(GHz)

Retur

n loss

(dB)

Gain(dB

)

Bandwidt

h (in

MHz)

Bandwidt

h (%age)

VSW

R

Band

s

0th

Iteration

2.90 -23.41 1.1 164 5.6 1.14 S

5.90 -16.25 2.8 232 3.9 1.3 C

7.72 -17.16 4.3 545 7.1 1.3 C

8.09 -16.83 5.1 545 6.7 1.3 X

8.90 -20.05 8.9 363 4.1 1.2 X

1st

Iteration

2nd

Iteration

2.7273 -15.88 -2 150 5.5 1.3 S

5.81 -30.23 3 180 3.2 1.06 C

7.45 -11.18 4.1 80 1.14 1.7 C

8.72 -16.46 4.9 230 2.6 1.3 X

2.90 -15.10 8.7 180 6.2 1.4 S

5.81 -15.59 2.8 230 3.9 1.3 C

7.63 -14.24 3.8 180 2.3 1.4 X

8.09 -14.37 8.05 140 1.7 1.4 X

8.63 -21.79 1.2 240 2.7 1.1 X

3rd

Iteration

2.81 -15.25 1.07 150 5.5 1.4 S

5.81 -13.27 2.53 230 3.9 1.5 C

7.81 -16.66 5.94 150 1.9 1.3 C

8.00 -18.00 6.2 140 1.75 1.2 X

8.72 -19.06 9.3 380 4.35 1.2 X

It is obvious from the Table 2 that 1st iteration has given the best return loss but gain

and bandwidth is not appropriate in comparison to the final iteration. But with increase

in iterations, we have attained best result at 8.72 GHz i.e. 9.3 dB with the bandwidth of

380 MHz and -19.06 return loss. Moreover VSWR calculated is also 1.2 which lie in

between 0 and 2 i.e; in acceptable range. All the designs of antenna shows their

applications in S, C, X bands.

966 Navpreet Kaur and Narinder Sharma

To analyze the behaviour and the performance of proposed antenna and to determine

the different parameters, the proposed antenna is designed and simulated using HFSS

V13 software. The final iteration of designed antenna is then fabricated and tested using

Vector Network Analyzer (VNA, Antrisu MS46322A) to validate the simulated results

with the experimental results. The setup used for testing the proposed antenna is shown

in Figure 8.

Table 3: Comparison of simulated and measured results of proposed antenna

Antenna Frequency (GHz) Return loss (dB)

Simulated 2.81, 5.81, 7.81,

8.00, 8.72

-15.25, -13.27, -16.66, -

18.00, -19.06

Measured 2.77, 5.78, 7.69,

7.96, 8.5, 9.6

-10.16, -10.63, -23.57, -

13.52, -20.82, -10.92

Figure 8: Experimental Test Set up of Antenna

Figure 9: Return loss v/s frequency curve of the proposed antenna

Designing Of Slotted Microstrip Patch Antenna Using Inset Cut Line Feed… 967

As observed from the Figure 9 that measured results of proposed antenna exhibits that

it resonates at four different frequencies with return loss -10.16 dB, -10.63 dB, -23.57

dB, -13.52 dB, -20.82 dB and -10.92 dB . There are some variations have been noted

in the simulated and the measured results of the proposed antenna. This variation is due

to the uncertainty in the electrical properties of the substrate or the reflection from the

SMA connector. Simulated and measured results are juxtaposed in Table 3.

Table 4: Comparative Analysis of Proposed Antenna with Existing Antennas

Reference

s

Size of Antenna

(mm3)

Resonant Frequencies

(in GHz)

Gain in dB Bands

[10] 50×40×1.6 2.4/5.5 3 S,C

[12] 60×60×1.6 1.95/3.12/3.87/5.24/5.8

4

7.4 L, S, X

[15] 54.36×46.72×1.5

2

1.86/2.29/3.02/4.50 7.4 S,C

[16] 92.6×62.6×3 3.9/7.4/10.4 6.1/5.9/5.1 S, C, X

[17] 52×71×1.6 1.6/1.9/3.8 7.6 L, C

[18] 50×50×2.4 3.8/4.4/7.9 2.68/0.50/4.4 S,C

[19] 38.9×40×1.6 2.10/2.85/5.15/9.11 8.02 S,C,X

Proposed

Antenna

55×35.5×1.6 2.8/ 5.8 /7.8 /8.00 /8.72 1.07/2.53/5.94/

6.2/9.3

S, C, X

4. CONCLUSIONS

In this paper, an optimal design of slotted MPA with inset-cut line feed (used to improve

the gain) has been presented, and observed that the designed antenna resonates at five

different frequencies and the return loss is less than -10 dB for all the frequencies. Gain

is also more than 3dB which is also a acceptable value gain for the antenna to work

effectively, and it can be contemplated from the Table 2 that proposed design exhibits

the high gain i.e; 9.3 dB. The proposed antenna can be used for S,C and X band wireless

applications for e.g. wireless broadband transceiver which is applicable to 802.16e,

mobile Wi-Max, fixed Wi-Max, 4G LTE system (at 2.7GHz), GSM ,CDMA

,Bluetooth, GPS, WLAN 802.11a, Transmitter design for 802.16, fixed CPE, Femto

BTS,WLAN access point . Simulated and measured results of proposed antenna are in

a reasonable agreement with each other, and fabricated antenna resonates at six

968 Navpreet Kaur and Narinder Sharma

different unique frequencies which is premeditated in Table 3 .It can be adorned from

the Table 3 that proposed antenna is smaller in size in comparison to the existing

antennas except antenna mentioned in reference [19]. If we observe the gain in

reference [19], it is only 8.02 dB whereas it is 9.3 dB in proposed design. So, proposed

antenna can be declared as better antenna.

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