Design & Performance Analysis of Double U-Slot Microstrip...

International Journal of Advanced Research in Electronics and Communication Engineering (IJARECE)

Volume 3, Issue 8, August 2014

790

ISSN: 2278 – 909X All Rights Reserved © 2014 IJARECE

Design & Performance Analysis of Double U-Slot

Microstrip Antenna for WiMAX Application

M.Ravi kishore*, A.Janardhana*

*Assistant Professor , ECE Department, Sri Sivani College of Engineering, Srikakulam, Andhra pradesh.

Abstract This paper presents the numerical simulation of double U-slots

microstrip patch antenna for WiMAX application. In this design

two slots and one bridge elements have been applied to generate

the three frequencies bands. In addition, the antenna has

achievable return loss, radiation pattern and also bandwidths.

Due to the compact area occupied, the proposed antenna is

promising to be embedded within the different portable devices

employing WiMAX applications. A simple method to achieve the

multi band characteristic in a micro strip antenna is embedding a

slot in the patch. A U-shaped slot has been investigated in order

to broaden the bandwidth of an antenna. In this paper multi

band characteristics are achieved by embedding number of U-

shaped slots on the rectangular patch. Also, an L-probe is used to

realize matching between the feed systems and radiating system

in a wide frequency range. Radiation performance of the

designed antenna is simulated using the HFSS software.

Due to the compact area occupied, the pro-posed antenna is

promising to be embedded within the different portable devices employing WiMAX applications.

Keywords—Duel U Band, U-shaped slot microstrip,Rectangular

Patch,L-Probe, WiMAX, HFSS Software

I. INTRODUCTION

Wireless operators are increasingly pressured to enhance their

networks and service capabilities in order to keep pace with

the accelerating growth in wireless utilization and increasing

demand for high performing connections. As bandwidth

intensive, rich media applications are introduced, larger

volumes of subscribers consume ever-growing quantities of

data packets while continuing to utilize more minutes of voice. Simply acquiring more spectrum channels and deploying more

sites to resolve capacity issues can be decidedly inefficient and

costly. Revolutionary multiple antenna techniques at the base

station and end-user device, paired with sophisticated signal

processing, can dramatically improve the communications link

for the most demanding application scenarios including

heavily obstructed propagation environments and high speed

mobility service. Where conventional wireless network design

has long used base site sectorization and single, Omni-

directional antennas at the end-user device to serve the

communications link, with advanced multi-antenna implementations operators have a new suite of tools to

develop the robust wireless networks of the future.

The IEEE 802.16 working group has established a new

standard known as WiMAX (Worldwide Interoperability for

Microwave Access) which can reach a theoretical up to 30-

mile radius coverage. Moreover, in the case of WiMAX, the

highest theoretically achievable transmission rates are possible

at 70 Mbps. One of the potential applications of WiMAX is to

provide backhaul support for mobile Wi-Fi hotspots. A low

profile double U-slots antenna for WiMAX operation has low return loss and bandwidth[1]. Recently, proposed printed

antenna for WiMAX operation has the three frequencies bands

but the return loss not over -30dB. The broadband

characteristic of a microstrip patch antenna with U-shaped slot

has been confirmed by many published results[1] [4] [5]. Also,

several designs of broadband slots antenna have been reported.

A monopole antenna for WiMAX applications was proposed

in. In this project, two slots and one bridge elements have been

applied to generate the three frequencies bands to be used in

WiMAX technology. Basically WiMAX has three allocated

frequency bands called low band, middle band and high band. The low band has frequency from 2.4 GHz to 2.8 GHz, the

middle band has frequency from 3.2 GHz to 3.8 GHz and the

high band has 5.2GHz to 5.8 GHz. This project addresses the

numerical analysis of the proposed antenna for WiMAX

operation with acceptable return loss, gain and bandwidth. For

the numerical analysis we consider the substrate permittivity

of the antenna is ɛ r =4.4(FR4) with substrate thickness

1.2mm and feed by a 50 Ω microstrip line. The analysis is

performed numerically using HFSS software.

Mobile WiMAX has offered the industry a very capable

platform by which to deliver the demanding service requirements for wireless access today and tomorrow. With

the added support for a variety of advanced multi-antenna

implementations, Mobile WiMAX offers the wireless operator

considerable relief in meeting their growing network demands

with higher performance, fewer sites, less spectrum, and

reduced cost.

II. METHODOLOGY

A. Design of Single U-Slot Antenna

The configuration of the proposed antenna is shown in Fig. The substrate used for this design is RF-35 with relative permittivity of 3.5, loss tangent of 0.0018 and thickness of h1 = h2 = 1:524 mm. Dimensions of the ground plane are also 100mm X 100 mm



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Figure1: Configuration of the proposed antenna, and top view of the radiating patch and side view of the whole antenna structure

Ground Plane Length

100mm Patch Width(W)

30mm

Ground Plane Width

100mm 𝒘𝒔 10mm

𝒉𝟏 1.524mm 𝒍𝒔 10mm

𝒉𝟐 1.524mm 𝒅𝟏 1.5mm

Substrate Length

60mm 𝒅𝟐 1.5mm

Substrate Width

60mm 𝒑𝒍 15mm

Patch Length(L)

30mm 𝒑𝒘 2.5mm

𝒑𝒔 1.75mm 𝒑𝒅 7.05mm

Table 1: Antenna Design Parameters for U-slot Antenna

As shown in Figure2 the radiating element is a square patch. Electromagnetic coupling probe, known as L-probe .By using

the slot, the dual band operation of the antenna can be

achieved. In general, the First resonant frequency is associated

with the size of the square patch and the second resonant

frequency is associated with the U-slot parameters[7]. The

other parameters in Fig.6.2(Pd, Pw, Pl, Ps)are optimized to

achieve good impedance matching at both resonant

frequencies. For obtaining two resonant frequencies at 2.25

GHz and 3.8 GHz, optimum values of the structural

parameters of the antennas are as follows. By using the above

configuration the proposed antenna is like as the below fig. The total view of a simple u-slot patch antenna is designed by

using HFSS software. In this we use a coaxial feeding with

aperture type. The aperture slab is at the height of 1.542mm

from the ground. The main purpose of this is to improve the

matching between the feeding and the radiating element[8].

The single u-slot antenna not accurately suitable for WiMAX

applications because of its multiple band characteristics. Using

the single slot we got only dual band characteristics but to

access multiple band structures we insert another slot within the slot. B. Design of Double U-Slot Patch Antenna

A low profile double U-slots antenna for WiMAX operation

has low return loss and bandwidth. It has a triple band of

frequency the propose antenna[1][2]for specific WiMAX

application is shown below figure 6.5

B

Figure 2: Design structure of the single u-slot patch

antenna W 40mm C1 5mm

L 47mm C2 3mm

L1 20mm Substrate Thickness

3.048mm

W1 30mm Substrate length

47mm

W2 15mm Substrate Width

40mm

L2 15mm Ground Length 47mm

W3 2mm Ground Width 60mm

L3 20mm

Table 2 : Antenna Design Parameters for Double-U band

Patch antenna.

C. Return Losses

Return loss is defined as

𝑅 = 20𝑙𝑜𝑔 Γ Where Γ is Reflection Coefficient



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The resonant frequencies can be calculated approximately as follows

𝑓1

=𝑐

2 𝜖𝑒𝑓𝑓𝐿1 (1)

𝑓2

=𝑐

2 𝜖𝑒𝑓𝑓𝐿2 (2)

WhereL1 and L2 are the average lengths for current paths

of the 1st and 2nd resonant modes and c is the free space

velocity of light. The effective permittivity is also given by

𝜖𝑒𝑓𝑓 =𝜖𝑟+1

2+𝜖𝑟−1

2(1 +

10𝑕

𝑤)−0.555

(3)

Where h and Ware height of the substrate and width of the patch, respectively. The above equation, which is given is

valid for single layer substrates[3] [2]. However, while the

effect of L-shaped feed system is negligible, this equation

can be used for two-layered substrates provided that the

parameter h is substituted by the total height of h1 +

h2.The average lengths for current paths of the 1st and 2nd

resonantmodes can be obtained by using the following

approximate relations:

𝐿1 = 𝛼1𝑙𝑠 + 𝛼2𝑤𝑠 + 𝛼3𝑤 (4)

𝐿1 = 𝛽1𝑑1 + 𝛽

2𝑑2 + 𝛽

3𝑑3 + 𝛽

4𝑤𝑠 (5)

Based on results of several simulations, optimum values of 𝛽

and 𝛼 in the above equations are obtained as follows.

𝛼1 = 0.385;𝛼2 = 0.445;𝛼3 = 1.000;

𝛽1

= 1.097; 𝛽2

= 0.630; 𝛽3

= 0.876; 𝛽4

= 1.412

For the values of parameters the average lengthsof current

paths for the 1st and 2nd resonant modes are obtained asL1 = 38:3mm and L2 = 22.2 mm. Also, the effective

permittivityis obtained as 3.097. Thus, Equations give the

resonant frequencies of 2.25 GHz and 3.8 GHz,

respectively.

The below figure shows the whole designed structure of

theproposed single u-slot antenna in HFSS simulator.

Figure 3: design structure of the single u-slot patch antenna

The designed patch antenna with double u-slot had been given

below figure

Figure 4: design structure of the single u-slot patch antenna

III. RESULTS

A.Return loss characteristics

For Single U-Slot

Figure 5: Return losses for single U microstrip antenna

For Double U-Slot

The equations which is applicable to above is same for this

type antenna is

Figure 6: Return losses for Double-U microstrip antenna



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For double u-slot the return losses are small compared to the

single u-slot. This antenna will resonate at frequencies of 2.08

GHz, 4.6GHz and 6.6 GHz. The return losses at 2.08 GHz, 4.6

GHz and 6.6 GHz is -25dB,-10dB and -17dB respectively. It

has a high efficiency at this frequency.

B. Radiation Pattern

For Single U-Slot

Figure shows the measured co-polarization and cross-

polarization radiation patterns for both resonant modes. As shown in this figure, radiation pattern of the antenna is

broadside at both resonant frequencies. Also the cross-

polarization of the 1st mode is 17 dB less than the co-

polarization values in the angular region of μ <50mm. For the

2nd mode, the cross polarization level is considerably low in

the E-plane, and its values in the H-plane are acceptable in the

region of μ <20. Increasing the cross-polarization level of the

2nd mode in the H-plane is due to the large x-component of

the current density in the vicinity of the right and left edges of

the slot. Figure 4 shows simulated radiation efficiency. As

shown in this figure, the efficiency of designed antenna is better than 80% in both of1st and 2nd modes.

Figure7:2D-Radiation pattern for single u-slot

C. 3-D View Of Radiation Pattern

The radiation pattern is main concentration for the WiMAX

application. For WiMAX application [9] [4] the effect of the

radiation is up to 30 miles. The gain must be high for this type

of application the radiation pattern for single u-slot is

Figure 8:3D-radiation pattern for single u-slot

The gain of the u-slot antenna is 4 dB. Maximum in the

direction of perpendicular to the strip antenna. The side lobes

were negligibly small of -9dB.

For Double U-Slot

Figure 9:2D-radiation pattern

Figure10:3D-radiation pattern

The above Results are shown is is the radiation pattern for

double u-slot it has the gain of little small as compared to the

u-slot but the Bandwidth of this is high and it has a multiple resonance frequencies.



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D. Field Distribution

Figure 11: E&H-field distribution for single u-slot patch

antenna

For the view of field distribution there is no uniform

distribution in the single u-slot patch antenna. For non-

uniform distribution of these fields the return losses are

somewhat high. For decrease the return losses there must

perfect matching between coaxial system and the radiating

element then we can easily remove the return losses. The

below fig represents the E &H fields of the double u-slot

antenna.

Figure12: E&H field distribution of double u-slot antenna

The return losses for this are -25dB is because of the uniform

field distribution over the patch.

7.4 VSWR

Fig7.8: VSWR for u-slot

The VSWR is very low at the resonant frequencies for U-slot

it is 10,2 at 2.25GHZ,3.8GHz respectively. For double U-slot it is 7,2 and 1 at 2.08 GHz, 4.6 GHz and 6.6 GHz respectively.

The return losses and VSWR are related to each other

Figure13: VSWR for double u-slot

E. Other Antenna Performance Parameters

For Single U-Slot

Table 3: Antenna performance parameter at different

frequencies for Single U-slot

For Double U-Slot

Table 4: Antenna performance parameter at different

frequencies for double slot



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F. Comparison of Parameters for Changing the

Substrate Thickness

For Single U-Slot

Table 5: Antenna performance parameters at diff substrate

lengths

G. Comparison of Parameters for Increasing Slot

Length

For U-Slot

Table 6: Antenna performance parameters at diff slot lengths

IV. CONCLUSION

In this paper we submitted the antenna simulation results

for WiMAX application of gain using single u-slot and double

u-slot is 7dB and 6dB respectively. By using array of this type

of antennas it is sufficient to acquire high gain. We got the

results of return losses for both type antennas is -25dB and-

23dB at a frequencies of 2.25GHz. These are very low losses

.The bandwidth for both are 2.2GHz and 2.1GHz. The

resonating frequency occurs at 2.25GHz and 3.38 GHz.

Finally we got beam width of antenna is 30 degrees. The efficiency of this antenna is 95.3% and 91.2%

This paper presented the simulation of the Microstrip patch

antenna with double U-slots. From two U- slots shape on the

patch, the three bands can be generated. By adding one bridge

the exact frequencies band for WiMAX can be achieved. The

three frequency band 2.25GHz, 4.50GHz and 6.6GHz has

been achieved as well as the bandwidth requirements for

WiMAX standards 4.22%, 1.87% and 3.51% respectively. The

re-turn loss for the triple bands are -25dB, -10dB and -17dB

respectively. The U- slot patch antenna is designed for

increasing the bandwidth and return loss but gain cannot

increase. If array of the U- slot patch antenna analysis used

then the gain can be improved. Therefore, the antenna will be

better work in the WiMAX applications and wireless communications system.

V. REFERENCES

[1] AbuTarboush,H.F. ; Al-Raweshidy,H.S. ; Nilavalan.R,

“Triple Band Double U-Slots Patch Antenna For Wimaxmobile

applications”Communications, IEEE Conference Publication, APCC 2008.

[2] W.L. Stutzman and G.A. Thiele, Antenna Theory and Design, 2nd ed.

New York: Wiley, 1998.

[3] C.A. Balanis, Antenna Theory, 2nd Ed. New York: John Wiley & sons,

Inc., 1997.

[4] Hattan F. Abu Tarboush, D. Budimir, R. Nilavalan “Connected U-slots

Patch Antenna for WiMAX Applications”. International Journal of RF &

Microwave CAF, 2008.

[5] H. F. AbuTarboush, H. S. Al-Raweshidy, “A Connected E-Shape and U-

Shape Dual- Band Patch Antenna for Different Wireless Applica-tions”, the

Second International EURASIP Workshop on RFID Tech-nology, July, 2008.

[6] M. Sanad, “Double C-patch antennas having different aperture shapes,” in

Proc. IEEE Antennas and Propagation Dig., June 1995, pp.2116–2119.

[7] Murad NA. “Microstrip U-shaped dual-band antenna,” Applied

Electromagnetic, 2005 APACE 2005 Asia-Pacific Conference on 2005:4 pp

[8] Hadian AM. “Wideband rectangular microstrip patch antenna with U-

slot,” Antennas and Propagation, 2007 EuCAP 2007 The Second European

Conference on. 2007:1-5.

[9] T. liu and L. L. Wong, “A wideband Stubby Monopole Antenna and a

GPS for WiMAX Mobile Phone with E911 Function,” Microwave and

Optical Technology Letter, Vol 46, 2005, pp.

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