Progress In Electromagnetics Research Symposium Proceedings, KL, MALAYSIA, March 27–30, 2012 1341

Effects of Microstrip Feed Line Width on 1× 4 RectangularMicrostrip Antenna Array Electrical Parameters and Estimation

with Artificial Neural Networks

O. Dundar1, D. Uzer2, S. S. Gultekin2, and M. Bayrak3

1Electronic Communication ProgramEregli Kemal Akman Technical Vocational School of Higher Education

Selcuk University, Konya, Turkey2Department of Electrical and Electronics Engineering

Faculty of Engineering-Architecture, Selcuk University, Konya, Turkey3Department of Electrical and Electronics Engineering

Faculty of Engineering, Mevlana University, Konya, Turkey

Abstract— In this study, 1× 4 rectangular microstrip array antennas are designed at 16 GHzresonant frequency for KU Band usage on Duroid 5880 substrate that has a thickness of 0.254 mmand a dielectric constant of 2.2. Designs are simulated using HFSS v12. At these designs,by changing the feed line widths systematically, for each antenna, electrical parameters likeS11 response, directivity, gain, radiation efficiency etc. are investigated for 26 array antennasin simulation media. Also, directivity and gain values are predicted with an Artificial NeuralNetwork model. The network has four inputs as dielectric substrate thickness, resonant frequencyand dielectric constant of the substrate and three outputs as directivity, gain and radiationefficiency. Multilayer perceptron structure for Artificial Neural Network model and Levenberg-Marquart learning algorithm for training the network are used. The network model is trainedwith 20 of 26 design data and is tested with the rest 6 ones. It is seen that the results fromsimulations and the neural network model are compatible with similar studies in the literature.

1. INTRODUCTION

Microstrip antenna is simply a conductive radiating patch whose bottom surface covered withground plane and between two conductive surfaces there is a dielectric substrate layer [1]. Althoughthese types of antennas have lots of advantage and application areas, their electrical parametersare depend on antennas’ physical parameters.

Thanks to microstrip antenna arrays’ lightness, low profile and cost, they generally use inKu Band application like VSAT, Radiometric place based fire sensation and microelectromecanicsystems between a large space [2]. In this study, a single antenna was design by using formulas inliterature used for classic rectangular microstrip antenna design then a 1× 4 element patch arrayantenna was designed that between a 0.428λ wavelength space with antenna elements [2].

2. ANTENNA DESIGN

A single antenna, seen in Figure 1, was designed on Duroid 5880 dielectric substrate that has athickness of 0.254 mm and a dielectric constant of 2.2 with a length of 7.41 mm and a width of6.2mm using classic rectangular microstrip antenna design formulas in the literature [3–5]. Fromthis single patch design, a 1× 4 patch antenna array contained 4 same size elements was obtainedlike seen in Figure 2 and between these antenna elements there were 0.428λ spaces.

3. EFFECTS OF FEEDLINE WIDTH ON ELECTRICAL PARAMETERS OF A 1 × 4RECTANGULAR MICROSTRIP PATCH ARRAY

The feed line was connected to connector with a 50Ω coaxial cable. The patch side of the feedline had a 100 Ω impedance. In literature a traditional quarter wavelength converter was appliedbetween 100 Ω patches and the feed line [1]. From different the literature, in this study the linewidth between 100 Ω patch and 50 Ω feed input was changed 0.2 to 0.7 mm. At total 26 antennaarrays were designed and these antennas were simulated by HFSS software. The simulation resultsare given in Table 1. From Table 1, it is seen that S11 response, directivity, gain and radiationefficiency increase with the increased feed line widths. The largest S11 value is for values between0.50–0.60mm. It can be said that the most efficient values of S11 response, directivity, gain andradiation efficiency are for No. 18 array with a 0.54mm width. A comparison of S11 response,

1342 PIERS Proceedings, Kuala Lumpur, MALAYSIA, March 27–30, 2012

Figure 1: Single patch antenna. Figure 2: 1× 4 array antenna.

Table 1: Electrical parameters variation against feed line lengths.

NoThickness(t) (mm)

f r

(GHz)f rHF SS

(GHz)S11

(dB)Directivity(D) (dB)

Gain (G)(dB)

RadiationEfficiency(Re) (dB)

BW (%)

1 0.20 16 16.34 −13.07 11.52 10.95 0.88 3.312 0.22 16 16.31 −13.34 11.41 10.85 0.88 3.563 0.24 16 16.35 −14.30 11.47 10.94 0.88 3.624 0.26 16 16.32 −13.55 11.49 10.93 0.88 3.945 0.28 16 16.29 −13.68 11.45 10.92 0.88 4.066 0.30 16 16.28 −14.17 11.47 10.93 0.88 4.317 0.32 16 16.09 −14.95 11.45 10.88 0.88 4.278 0.34 16 16.14 −14.04 11.50 10.96 0.88 4.449 0.36 16 16.10 −14.84 11.49 10.94 0.88 4.4410 0.38 16 16.07 −15.53 11.49 10.96 0.88 6.7511 0.40 16 16.05 −16.80 11.50 10.97 0.89 4.1912 0.42 16 16.06 −16.96 11.50 10.99 0.89 4.3713 0.44 16 16.00 −17.30 11.46 10.91 0.88 4.3014 0.46 16 16.05 −18.68 11.53 10.98 0.88 4.1915 0.48 16 16.03 −19.44 11.50 10.97 0.89 4.1916 0.50 16 16.03 −19.91 11.51 10.97 0.88 4.3617 0.52 16 16.00 −20.95 11.57 11.00 0.88 3.9418 0.54 16 16.00 −22.61 11.54 11.02 0.89 3.8819 0.56 16 16.02 −22.97 11.47 10.93 0.88 4.2620 0.58 16 15.97 −25.63 11.52 11.01 0.89 3.8121 0.60 16 15.99 −26.97 11.48 10.94 0.89 3.8722 0.62 16 15.80 −23.30 11.42 10.90 0.89 1.8823 0.64 16 15.80 −31.34 11.38 10.88 0.89 2.1324 0.66 16 15.82 −22.97 11.46 10.92 0.88 1.9425 0.68 16 15.84 −17.09 11.43 10.90 0.89 1.5626 0.70 16 15.81 −19.43 11.45 10.92 0.89 1.75

directivity, gain and radiation efficiency values between No. 18 design and the design in literaturewith quarter wavelength converter is given in Table 2 [2].

Progress In Electromagnetics Research Symposium Proceedings, KL, MALAYSIA, March 27–30, 2012 1343

Table 2: Comparison of No. 18 design with [2].

AntennaParameters

S11 Response

1× 4 Patch

−3.70 dB

1× 4 Patch

−22.61 dBSimulation Frequency 16.10GHz 16.00GHz

Directivity 11.52 dB 11.54 dBGain 10.837 dB 11.02 dB

Radiation Efficiency 0.85 0,89

Table 3: Train and test data set for ANN model and iteration results.

No

Inputs Simulation Outputs ANN Outputs

f r

(GHz)

t

(mm)εr

h

(mm)

D

(dB)

G

(dB)Re

DANN

(dB)

GANN

(dB)Re

Train

Set

1 16 0.20 2.2 0.254 11.5200 10.9500 0.8800 11.5200 10.9500 0.8800

2 16 0.22 2.2 0.254 11.4100 10.8500 0.8800 11.4100 10.8500 0.8800

3 16 0.24 2.2 0.254 11.4700 10.9400 0.8800 11.4700 10.9400 0.8800

4 16 0.26 2.2 0.254 11.4900 10.9300 0.8800 11.4900 10.9300 0.8800

5 16 0.28 2.2 0.254 11.4500 10.9200 0.8800 11.4500 10.9200 0.8800

6 16 0.30 2.2 0.254 11.4700 10.9300 0.8800 11.4700 10.9300 0.8800

7 16 0.32 2.2 0.254 11.4500 10.8800 0.8800 11.4500 10.8800 0.8800

8 16 0.34 2.2 0.254 11.5000 10.9600 0.8800 11.5000 10.9600 0.8800

9 16 0.36 2.2 0.254 11.4900 10.9400 0.8800 11.4900 10.9400 0.8800

10 16 0.38 2.2 0.254 11.4900 10.9600 0.8800 11.4900 10.9600 0.8800

11 16 0.40 2.2 0.254 11.5000 10.9700 0.8900 11.5000 10.9700 0.8900

12 16 0.42 2.2 0.254 11.5000 10.9900 0.8900 11.5000 10.9900 0.8900

13 16 0.44 2.2 0.254 11.4600 10.9100 0.8800 11.4600 10.9100 0.8800

14 16 0.46 2.2 0.254 11.5300 10.9800 0.8800 11.5300 10.9800 0.8800

15 16 0.48 2.2 0.254 11.5000 10.9700 0.8900 11.5000 10.9700 0.8900

16 16 0.50 2.2 0.254 11.5100 10.9700 0.8800 11.5100 10.9700 0.8800

17 16 0.52 2.2 0.254 11.5700 11.0000 0.8800 11.5700 11.0000 0.8800

18 16 0.54 2.2 0.254 11.5400 11.0200 0.8900 11.5400 11.0200 0.8900

19 16 0.56 2.2 0.254 11.4700 10.9300 0.8800 11.4700 10.9300 0.8800

20 16 0.58 2.2 0.254 11.5100 11.0100 0.8900 11.5100 11.0100 0.8900

Test

Set

21 16 0.60 2.2 0.254 11.4800 10.9400 0.8800 11.5133 11.0048 0.8795

22 16 0.62 2.2 0.254 11.4200 10.9000 0.8900 11.4479 10.8504 0.8592

23 16 0.64 2.2 0.254 11.3800 10.8800 0.8900 11.3387 10.6007 0.8969

24 16 0.66 2.2 0.254 11.4600 10.9200 0.8800 11.2747 10.5991 0.9949

25 16 0.68 2.2 0.254 11.4300 10.9000 0.8900 11.2661 10.5997 1.0066

26 16 0.70 2.2 0.254 11.4500 10.9200 0.8900 11.2655 10.5997 1.0074

4. ESTIMATION OF DIRECTIVITY, GAIN AND RADIATION EFFICIENCY WITH ANARTIFICIAL NEURAL NETWORK MODEL

Directivity, gain and radiation efficiency of the designed a 1×4 array patch antenna was estimatedwith a four input-three output ANN model for constant width, frequency thickness and dielectricvalue [7, 8]. The ANN model had a Multi-Layer Perceptron (MLP) structure and for training thestructure, Levenberg-Marquardt (LM) algorithm was used [7–10]. MLP structure and ANN modelare given in Figure 3. Train and test data set for ANN model and iteration results are given inTable 3.

In Table 3, given ANN inputs are resonant frequency (fr), feed line width (t), dielectric constantof the substrate (εr) and dielectric substrate thickness (h), while outputs are directivity (D), gain(G) and radiation efficiency (Re). ANN-LM network has a 4 × 9 × 10 × 3 structure and epochnumber is 205. Train performance of the network is 2,34.10–31. Train and test graphics obtainedfrom train results are given in Figure 4.

1344 PIERS Proceedings, Kuala Lumpur, MALAYSIA, March 27–30, 2012

(a) (b)

Figure 3: Multilayer perceptron structure and ANN model structure.

Figure 4: Train and test graphics obtained from iterations.

5. CONCLUSION

In this study, 26 1×4 patch antenna arrays were designed. When the electrical parameters of theseantennas were investigated, it was shown in Table 1 that No. 18 design had the best performancecompared to the literature from Table 2. This study was presented as an alternative of traditionalquarter wavelength converters in the literature.

Also, the obtained antenna parameters were used for an ANN model testing and it was seenfrom the graphics, directivity, gain and radiation efficiency values were estimated. It is observedfrom the results that this estimation is enough successful.

ACKNOWLEDGMENT

This study is supported by Scientific Research Project Office of Selcuk University.

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1989.5. Green, D. W., “Broadbanding of microstrip antenna,” www.cwnp.com/learning center/se-

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Progress In Electromagnetics Research Symposium Proceedings, KL, MALAYSIA, March 27–30, 2012 1345

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