Download - ASYMMETRICAL U-SLOTTED RECTANGULAR MICROSTRIP PATCH ANTENNA

7/30/2019 ASYMMETRICAL U-SLOTTED RECTANGULAR MICROSTRIP PATCH ANTENNA

http://slidepdf.com/reader/full/asymmetrical-u-slotted-rectangular-microstrip-patch-antenna 1/4

International Journal of Application or Innovation in Engineering& Management (IJAIEM)Web Site: www.ijaiem.org Email: [email protected], [email protected]

Volume 2, Issue 3, March 2013 ISSN 2319 - 4847

Volume 2, Issue 3, March 2013 Page 81

ABSTRACT

The Microstrip antennas are low profile, mechanically robust, inexpensive to manufacture, compatible with MMIC designs andrelatively light and compact. They are quite versatile in terms of resonant frequencies, polarization, pattern and impedance.

However, the major drawback is its narrow bandwidth and gain. As it is well known that the simple conventional microstripantenna has an impedance bandwidth of less than 2 % with low gain of 2 dB. In this paper, bandwidth of microstrip antenna is

increased by introducing a slot of U shape. The Ansoft HFSS 11 is used for the simulation .The antenna is fed by coaxial probe

feeding technique. The designed antenna provides the bandwidth of 300MHz (5.61GHz-5.91GHz) with return loss of -26.26db

at 5.76GHz and 310 MHZ (6.36GHz-6.67GHz) with return loss of -24.12db at 6.48GHz.VSWR is 0.82 at 5.76GHz and 1.03 at6.48GHz.

Keywords: Slotted Microstrip Antenna, VSWR, Return loss, Gain, HFSS

1. INTODUCTION

A microstrip antenna consists of conducting patch on a ground plane separated by dielectric substrate. Low dielectric

constant substrates are generally preferred for maximum radiation. The conducting patch can take any shape butrectangular and circular configurations are the most widely used shapes. A feed line is used to excite patch antenna to

radiate by direct or indirect contact. Four most popular methods are micro strip line feed, coaxial probe, aperture

coupling and proximity coupling [1]. In this paper, antenna is fed by coaxial probe feeding techniques. The microstrip

patch antenna in the basic form of a conducting patch in a grounded substrate is inherently narrowband and is not able

to meet the requirements of wireless communication systems. Whereas bandwidth can be increased by using lossy

substrates, this is usually not desirable as efficiency will be reduced. The methods developed for efficient wideband

patch antenna design are based on one or more of the following principles:

a) By means of parasitic elements or slots, additional resonances are introduced so that, in conjunction with the main

resonance, an overall broader band response is obtained.

b) Thick substrates of low permittivity are used

Loading specific slot on the conducting patch element of antenna, reduced size with improvement in bandwidth, gain

can be obtained [2]. The loading of slots on the conducting patch element can cause meandering of the excited patchsurface current paths and results in lowering of the resonant frequency, which corresponds to the reduced antenna size

compared to the conventional microstrip patch antenna at designed frequency. In this paper, study is made that by

loading slots on the conducting patch element with thick dielectric medium excited through single coax feed

arrangement providing improvement in antenna impedance bandwidth, gain with size reduction characteristics.

The impedance bandwidth is increase with substrate thickness t and inversely proportional to [3].

BW ~volume = area×height =length ×width ×height

~ × × =

Impedance Bandwidth of patch antenna varies inversely as Q of a patch antenna [4]. Therefore substrate such as

dielectric constant and thickness h can be varied to obtain different Q,and ultimately the increase in impedance

bandwidth Q of a resonator is defined as

Q=

ASYMMETRICAL U-SLOTTED

RECTANGULAR MICROSTRIPPATCH ANTENNA

Amit Khandelwal

Govt. Engineering College, Ajmer, Rajasthan






2. DESIGN

I) DESIGN FORMULA

A. Calculation of the Width (W):

The width of the Microstrip patch antenna is given by equation (1):

W= (1)

Where c is the velocity of light.

B. Calculation of Effective dielectric constant

= + [1+12 ] -1/2 (2)

C. Calculation of the Effective length ( ):

= (3)

D. Calculation of the Length Extension (ΔL):

(4)

E. Calculation of actual length of patch (L):

L= -2L (5)

I I) DESIGN SPECIFICATIONS

Figure 1Top view of Slotted Rectangular Microstrip Patch Antenna

In this design two different dielectric material i.e. Rogers RT/duriod 5880 ( = 2.2, h= 4.2 mm, tanδ=0.0009) and pec

material ( =1.00) was used.

Table 1: Antenna dimensions

S. No. Antenna parameters Specification

1. Length of the Substrate (L) 78mm

2. Width of the Substrate (W) 78mm

3. Length of the Patch (L) 40mm

4. Width of the Patch (W) 40mm

5. Height of the Substrate (h) 4.2mm

6. Distance from Feed(F) 8.45mm

7. Length of U slot arm(U1) 16.9mm



10. Width of Slot(W1) 2.3mm






3. RESULTS & DISCUSSION

The Asymmetrical U-slot antenna of parameters listed in Table I has been fabricated and measured to compare the

simulated results. The bandwidth of 300MHz (5.2%) with return loss of -26.52db at 5.76GHz and 310 MHZ(4.7%)

with return loss of -24.12db at 6.48GHz. Simulated results for U slot probe feed patch antenna is shown Table 2.

Table 2: Simulated results for U slot probe feed patch antenna

Patch

Shape

Frequency Gain Return

Loss

VSWR Bandwidth

U Shape 5.76GHz 9.283d

B

-26.26dB 0.82dB 5.61GHz-5.91GHz

6.48GHz -24.12dB 1.03dB 6.36GHz-6.67GHz

3.00 3.50 4.00 4.50 5.00 5.50 6.00 6.50 7.00Freq [GHz]

-30.00

-25.00

-20.00

-15.00

-10.00

-5.00

0.00

d B ( S t ( C o a x_

P i n_

T 1 , C o a x_

P i n_

T 1 ) )

Ansoft Corporation HFSSDesign2XY P lot 1Curve Info

dB(St(Coax_Pin_T1,Coax_Pin_T1))

Setup1 : Sweep1

Figure 2Return losses vs. Frequency curve for proposed antenna

3.00 3.50 4.00 4.50 5.00 5.50 6.00 6.50 7.00Freq [GHz]

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

d B ( V S W R t ( C o a x_

P i n_

T 1 ) )

Ansoft Corporation HFSSDesign2XY Plot 3

m1

Curve Info

dB(VSWRt(Coax_Pin_T1))

Setup1 : Sweep1

Name X Y

m1 5.7600 0.8240

Figure 3VSWR for proposed antenna

VSWR is 0.82 at 5.76GHz and 1.03 at 6.48GHz obtained.






-30.00

-20.00

-10.00

0.00

90

60

30

0

-30

-60

-90

-120

-150

-180

150

120

Ansoft Corporation HFSSDesign2Radiation Pattern 1

Curve Info

dB(GainTotal)

Setup1 : LastAdaptive

Phi='0deg'

dB(GainTotal)

Setup1 : LastAdaptive

Phi='90deg'

Figure 4Radiation Pattern

The radiation Pattern with maximum gain of 9.283db is shown in figure 4.

4. CONCLUSION

In this paper, Small dual band for asymmetrical U-slotted rectangular micro strip patch antenna is designed. The probe

feed technique is used and simulation is performed and validated on HFSS11’ [5]. The parameters, such as gain,

VSWR, return losses etc. are taken for the consideration and are shown in the Table 2. The conclusion is that these

parameters are satisfactory for these bands. The antenna is designed to be used in WiMax and multi-band applications.

REFERENCES

[1] Constantine A. Balanis, ‘Antenna Theory, Analysis and Design’ (John Wiley & Sons)

[2] Kin-Fai Tong and Ting-Pong Wong, “Circularly Polarized U-Slot Antenna” IEEE Transactions on Antennas AndPropagation, Vol. 55, No. 8, August 2007

[3] K. F. Lee and K. F. Tong, “Microstrip patch antennas- Basic Characteristics and Some recent Advances” Proc.IEEE. December 13, 2011.

[4] Ramesh Garg, ‘Handbook of Microstrip Antennas[5] Ansoft Designer, www.ansoft.com.

AUTHOR

Amit Khandelwal did his B.E. in Electronics and Communication Engineering from University of Rajasthan, Jaipur, Rajasthan. He is doing M.Tech. in Electronics and Communication at Govt. Engineering College, Ajmer,Rajasthan from Rajasthan Technical University, Kota, Rajasthan. His research areas are DIGITAL

COMMU1NICATION.