A Three Element Planner Antenna Array in

Golden Ratio with 2:1:1 Corporate Feeding

Rabindra K. Mishra, Subhendra K. Dash Electronic Science Department

Berhampur University Bhanja Bihar, Berhampur 760 007, Orissa (INDIA)

e-mail: r.k.mishra@ieee.org

Abstract- 3 element planner antenna arrays with uniform and non-uniform spacing are compared. The non-uniform spacing uses the Golden Ratio. Simulated and experimental results are presented.

I. INTRODUCTION

In the nature as well as in many ancient & modem architecture the presence of Golden Ratio is prominent. When a given length is divided into two parts such that the ratio of the length to the larger part is same as the ratio of the larger part to the smaller part, then the ratio is known as Golden Ratio or the Magic Number. It is an irrational number, numerically equal to ("'5+ 1)/2 or approximately 1.618. For example, in the human body parts of arm, limbs are in golden ratio [1].

This work is an effort at exploring the use of Golden Ratio in antenna technology. A 2:1:1 power divider is used to feed lX3 microstrip antenna array. Results of Uniform patch [2-7] array (UPA) is compared with Golden Ratio Patch Array (GRPA).

II. DESIGN PRINCIPLE

To start with a 3-element uniform array of E-Patch Antennas is designed. For the E-Patch, the middle finger is so designed that its characteristic impedance is 50 ohm. Also, the depth of the gap is so adjusted that 50 ohm impedance is obtained at the end of the middle finger. This antenna element is supposed to exhibit dual band characteristics. A corporate feed is designed starting at the source and terminating at each of the middle fingers of the array elements. The path length to each of the terminating finger from the source is constant to maintain in-phase excitation of the array elements.

For 1:1:1 feeding, the impedances of the two lines, terminating at the 33.3 ohm, are in the 2: 1 ratio (i.e. 50 ohm & 100 ohm). A quarter-wave transformer converts the 33.3 ohm point to 50 ohm source point. Due to 2:1 impedance ratio, the power towards the left (i.e. 100 ohm) arm is half of the power towards the right. The power towards the right side is again divided equally between the two elements. Thus, the power division from the source is equal to each of

978-1-4244-7917-71101$26.00 ©2010 IEEE

Pradyumna K. Patra Electronics & Communication Engineering Department

National Institute of Science & Technology Palur Hills, Berhampur, Orissa (INDIA)

Shyam S. Pattnaik ETV Department

NITTTR, Chandigarh

the antenna element. For 2:1:1 feeding, the impedances of the two lines,

terminating at the 50 ohm source, are in the 1: 1 ratio (i.e. 100 ohm & 100 ohm). Due to 1:1 impedance ratio, the power towards the left (i.e. 100 ohm) arm is equal to the power towards the right. The power towards the right side is again divided equally between the two elements. Thus, the power division from the source is in the 2: 1 : 1 ratio to the antenna

Figure 2: Fabricated Prototypes (Left: UA & Right: GRA)

The procedure of feeding is illustrated in figure 1 for all configurations. Photographs of fabricated prototypes are shown in figure 2.

III. RESULTS AND DISCUSSIONS

A dielectric substrate of thickness l.5mm and dielectric constant 2.8 is used for simulation and fabrication. The antenna element was designed for 8.5GHz and IOGHz operation. After optimization the patch size were found to be 5.8mm x 8.8 mm. The gap depth is 1.089 mm and the mid­finger width is 2.731 mm. The prototype array length is 36 mm.

The antennas were simulated using le3D and the data were stored in data files. S-parameter variation with frequency is depicted in figure 3. It shows dual band operation of the arrays as expected. Then the fabricated arrays were tested for their S-parameter variation using Agilent VNA (Fig.4). The measured results are shown in Fig. 5 & 6 respectively for the UP A and GRP A. Figures 7 & 8 show the simulated radiation

pattern for the UP A and GPRA respectively. It is expected that the pattern in the GRP A will get distorted due to increased mutual coupling between the left two elements. But, it is observed that for GRP A the radiation pattern is not distorted from that of the UP A. A detailed parametric study is being undertaken to look into the reasons for such deviation.

IV. ACKNOWLEDGEMENT

The authors are thankful to Er. Sngram Mudali, the Director and Dr. Ajit Ku. Panda, the Dean of NIST, Orissa for providing the Lab facility at NIST. The authors also like to thank Er. Rajesh Ku. Dash, of NIST, for his support during fabrication and measurement.

REFERENCES

[I] http://milan.milanovic.org/math/english/goldenlgolden2.html

[2] Hsiuan-ju Hsu, Michael 1. Hill, Richard W. Ziolkowski, and John Papapolymerou "A Duroid-Based Planar EBG Cavity Resonator Filter With Improved Quality Factor" IEEE Antennas and Wireless

d,

2:1:1 Uniform Array Antenna

IUAA)

500

d, d,

500

2:1:1 Golden RatIO Array Ant.nna (GRAA)

500

Propagation Letters, Vol. I, 2002.

[3]P.K.Patra, Dr.S.S.Pattnaik, etal "Bandwidth Enhancement & Multi resonance" International Journal of Microwave and Optical Technology Letters, USA, Vol. 3, March 2008.

[4] D. M. Pozar, Microwave Engineering, 2nd ed. New York:Wiley, 1998.

[5] Garg, R., P. Bhartia, I. Bahl, and A.Ittipibon, MicrostripAntenna Design Handbook, Artech House, Boston, London, 200 I.

[6] Chung, Y., S. Jeon, D. Ahn, J. Choi, and T. itoh, "High isolation dual polarized patch antenna using integrated defected ground structure," IEEE Microw. Component Lett. Vol. 14, No. 1, 4-6, Jan. 2004.

[7] Yu, A. and X. Zhang, "A novel method to improve the performance of microstrip antenna arrays using dumbbell EBG structure," IEEE Antennas and Wireless Propagat. Lett., Vol. 2,2003.

d,

1:1:1 Uniform Array Antenna IUAA)

500

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1:1:1 Golden Ratio Arr.yAntennl

IGRAA)

Fig\: The Diagram of 2:1:1 UAA, 2:I:IGRPA, I:I:IUAA and 1:1:1 GRPA

Figure 3: Experimental Setup

COMAPRISION

"",;---,';;..5---;----;; .... 5 --;;;"--,*,,.'5 ----;';----;,7;1.5,---�· Fl8quency(GHz)

Figure 4: Simulated S-Parameters of the UP A and GRP A

Figure 5: Measured S-Parameters of GRP A (Feed 2: I: 1)

----4----P'f-10(GHz).E-tOfalpl.·O(IIeU) -----r'.10iGHz). E-tOlill. ph'-go (deu) -+---f""r-10.01(GHz). E-iotaL ph'-O (deu) ----rr-tO.01(GHz). E-Iotal. pl.-go (deDI --rr-tO.02(GHz). E-total phi-o (deU. ----rr-10.02(GHz). E.totat. phi-go (deo)

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Figure 7: Gain Pattern GRPA (Feed 2:1:1)

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Figure 6: Measured S-Parameters of UPA (Feed 2: I: 1)

'-10(f.ltll..[,,, ... phteG(dt-g) --r'·10(GHU. E ,ot& ptrto (1Itg) ---1'--1f .. 10, I(GHI). f.tpf,,," phH (lkg) ----rf-tO. HGHl). £.IaI,'" ph;-to fd.eul

'-10.1 1(Gbl. ["'Ofaf. pW-<l IdttII --f'"'-10.111f.JHZ .. E'OUi.Ph!ofil!ltg.

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Figure 8: Gain Pattern UPA (Feed 2:1:1)