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Circular Patch loaded Annular Ring Microstrip Antenna using L-probe Feed

A. K. Singh1,2, Ravi Kumar Gangwar2and Binod K. Kanaujia3

1Department of E.I. Engineering, F.E.T., M.J.P. Rohilkhand University, Bareilly, India, 243006, 2 Department of Electrics Engineering, I.S.M. Dhanbad, Jharkhand, India, 826004,

3 Department of Electrics Engineering, AIACTR, Geeta Colony, Delhi, India, 110031, Email: anilei76@gmail.com, ravi8331@gmail.com, bkkanaujia@ieee.org

Abstract— A coaxially stacked Annular Ring Microstrip Antenna (ARMSA) and Circular Microstrip Antenna (CMSA) using L-probe feed is designed and fabricated. Parametric analysis of the proposed antenna is carried out using commercially available Ansoft HFSS software. The experimental results of input characteristic is compared with simulated results and found good agreement.

Keywords— Microstrip Antenna, Annular Ring Microstrip Antenna, Stacked Antenna, L-probe feed, Orthogonal Slot, Multiband Antenna.

I. INTRODUCTION Microstrip antennas are attractive and used in most of the

wireless communication systems [1-6] due to its numerous advantages like compact size, light weight, low profile, easy to fabrication [7] etc. Modern communication system technology has been change completely from physical connection to wireless communication which required small size antenna, wideband and multiband antennas to communicate multiple devices simultaneously. Annular Ring Microstrip Antenna (ARMSA) is more appropriate antenna among the microstrip antenna, to meet the challenges of latest communication systems. Comparatively ARMSA has the lower resonance frequency of the same size than the other microstrip antenna [8], which fulfills the requirement of compact antenna. Further, a number of researchers are paying more concentration towards the reducing size of the antenna using different techniques like thick substrate [9], using shorting plate/pins [10], or by cutting slots in the radiating patch [11], defected ground plane [12]. To increase the bandwidth of microstrip antenna, several method have been employed like thick substrate having low permittivity, L-probe feeding [13]. Multiband antennas are also very much useful in present day wireless communication system, this important characteristic of the antenna is achieved by stacking [14] or gap coupled [15].

In this paper, circular patch loaded annular ring microstrip patch antenna using L-probe feed and orthogonally slot loaded at the inner periphery of the driven ARMSA is investigated, the effect of the variation in the horizontal probe length and height of the circular patch and is also analyzed. Simulated

results of the input characteristics are compared with the experimental results.

II. DESIGN CONSIDERATIONE Fig. 1 (a) shows the geometry of the proposed antenna.

Annular patch with an orthogonal slot at inner periphery is placed on the upper substrate of 1.59 mm thickness (Rogers RT/Duroid5880 with dielectric constant = 2.2) and the height of this substrate from the ground plane is h2. A circular patch on lower substrate of 1.59 mm thickness (Rogers

h1 h2

Z

X

Y

Annular Patch

Ground plane

L-probe

ws

y0

b a

Side view

Top view X

Circular Patch

H

d

Upper Substrate

Lower Substrate

t t

(a)

(b)

Fig.1. (a) Geometry and (b) top view of fabricated antenna (the drawing is not in the scale).

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RT/Duroid5880) is placed at a height of h1 (h1 <h2) from the ground plane, and in between of these two substrate a inverted L-shaped probe with a vertical height of H and the horizontal length of y0 is placed. The fabrication image of the proposed structure is shown in Fig. 1 (b). Design parameters of the proposed Antenna are: Inner radius of ARMSA (a) = 30 mm, Outer radius of ARMSA (b) = 60 mm, Radius of CMSA (d) = 28 mm, Substrate material used = Rogers RT/Duroid5880, Relative permittivity of Substrate = 2.2, Thickness of substrate (t) = 1.59 mm, Height of lower substrate from ground plane (h1) = 6 mm, Height of upper substrate from ground plane (h2) = 8 mm, Height of the vertical L-probe ( H) = 8 mm, Length of the horizontal L-probe (y0) = 67 mm, The width of the L-probe (ws) = 2 mm, Width of the slot = 8 mm, Length of slot = 20 mm.

III. RESULTS AND DISCUSSION The results of the proposed antenna, is discussed in this

section. Variation of |S11| parameter with frequency for different height of the lower substrate (h1) at d = 28 mm is shown in fig. 2. It is also observed that with increasing the height of the lower substrate having CMSA (keeping the upper substrate at fixed height), resonance frequency is decreasing due to increasing in the equivalent relative permittivity around the L-probe between upper and lower substrate.

Variation of |S11| parameter with frequency for different radius of CMSA (d) at h1 = 6 mm is shown in fig. 3. It is observed that the resonance frequency is decreased by increasing the radius of CMSA at f1, f2, f3 and increase the resonance frequency at f4 due to fringing field. Comparison of simulated and experimental results of the |S11| with frequency of the proposed antenna for is shown in fig. 4. Simulated results show good agreement with experimental results. The proposed antenna shows four resonance frequency at f1 = 1.88 GHz, f2 = 2.51 GHz, f3 = 3.81 GHz and f4= 4.88 GHz with 6.38%, 9.96%, 2.62% and 3.27% impedance bandwidth respectively.

IV. CONCLUSION The proposed antenna is designed and fabricated successfully. Simulated and measured results are close to each other. The proposed antenna realizes four resonance frequency in L-band

(1.88 GHz), S-band (2.51 GHz) and C-band (3.81 and 4.88 GHz) band with 6.38%, 9.96%, 2.62% and 3.27% impedance bandwidth respectively. This antenna can be used as Personal Communication Service in Digital Enhanced Cordless Telecommunications, ISM band shared with Wi-Fi, Bluetooth, Wi-MAX, and also as unlicensed spectrum devices such as cordless phones, wireless headphones, and video senders applications

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[4] EI-Khamy, S. E. EI-Awadi, R. M. and EI-Sharrawy, E-B. A., “Simple analysis and design of annular ring microstrip antennas”, IEE Proceedings, vol. 133-3, pp. 198-202, 1986.

[5] A. K. Bhattacharya and R. Garg, “Input Impedance of Annular Ring Microstip Antenna Using Circuit Theory Approach”, IEEE Transaction on Antenna and Propagation, vol. AP-33- 4, pp. 369-374, 1985.

1.5 2 2.5 3 3.5 4 4.5 5 5.5-40

-35

-30

-25

-20

-15

-10

-5

0

Frequency(GHz)

|S11

|(dB

)

SimulatedExperimental

Fig.4 Simulated and experimental results of the |S11| with frequency of the

proposed antenna at h1= 6 mm and d= 28 mm.

1.5 2 2.5 3 3.5 4 4.5 5 5.5-40

-30

-20

-10

0

Frequency(GHz)|S

11|(d

B)

d=22 mmd=25 mmd=28 mm

Fig.3 Simulated results of variation in |S11| with frequency for different

circular patch radius (d) at h1= 6 mm.

1.5 2 2.5 3 3.5 4 4.5 5 5.5-50

-40

-30

-20

-10

0

Frequency(GHz)

|S11

|(dB

)

h1=4 mmh1=5 mmh1=6 mm

Fig.2 Simulated results of variation in |S11| with frequency for different

height of lower substrate (h1) at d= 28 mm.

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[6] J.-M. Ribero, J.- P. Damiano and R. Staraj, “Accurate analysis and synthesis of annular ring microstrip antennas”, IEE Proc.-Microwave Antenna Propagation, vol. 144- 5, pp. 341-346, 1997.

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[10] H. Wong, K. K. So, K. B. Ng, K. M. Luk, C. H. Chan and Q. Xue, “Virtually shorted patch antenna for circular polarization”, IEEE Antennas and Wireless Propagation Letter, vol. 9, pp. 1213-1216, 2010.

[11] H. Iwasaki, “A circularly polarized small-size microstrip antenna with a cross slot”, IEEE Transaction on Antenna and Propagation, vol. 44-10, 1399-1401, 1996.

[12] A. K. Gautam, B. K. Kanaujia, “A novel dual-band asymmetric slot with defected ground structure microstrip antenna for circular polarization operation”, Microw. Opt. Technol. Lett., vol. 55, pp. 1198-1201, 2013.

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