Miniaturization of a patch antenna by thin film materials

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The First National Conference on Electronics and New Technologies (NCENT’2015)

May 19-20, M'Sila, Algeria

Miniaturization of a patch antenna by thin film materials

A.REDDAFâ*,F.MEDJILIâ,Y.FACIâ,NacerddineBouzit^b a- Welding and NDT Research Centre (CSC), BP 64 Cheraga, Algeria

Thin Films and Application Unit (U.D.C.M.A)-Sétif.

b-Laboratoire d’Instrumentation Scientifique (LIS), Université Ferhat Abbas, 19000-Sétif Algeria.

Abstract— The miniaturization of printed antennas is made possible by changing the volume of the antenna with high permittivity materials, ferroelectric, ferromagnetic, magneto-dielectric, etc. More traditionally, the dielectric having a high permittivity were employed to decrease the physical dimensions of antenna patch. The problems often encountered with high permittivity substrates are, degradation of the gain and the bandwidth and therefore the efficiency of the antenna. The use of magnetic materials would be an interesting solution for the miniaturization of antennas without degrading performance due to the significant value of permeability.

Keywords- patch antenna, magneto-dielectric materials, HFSS ,thin films.

I. INTRODUCTION

The patch antenna was introduced by John Q.

Howell in 1972 [1]. Using a high-k dielectric material is the most common method to reduce the size of the antenna [2-3]. In this work, we will show firstly reducing antenna size for a planar antenna printed on a dielectric substrate and secondly on a substrate integrated magneto- dielectric material in a thin layer.

II. PATCH ANTENNA

The micro strip antenna is a transmission line consisting of a thin metallic conductor (typically from 17.5 to 35μm thick microwave) called radiating element, it is of arbitrary form, deposited on a thick substrate used to increase the power radiated and reduce the losses by the Joule effect and improve the bandwidth of the antenna, the lower side is entirely metalized to provide a ground plane, and is shown in Fig. 1. this transmission line cannot support the pure Electric- magnetic transverse (TM- TE) of the transmission, since the phase velocities are different in the air and the substrate, for this purpose the dominant mode of propagation is the quasi-TEM mode. the optimization of the dimensions is done using a program developed in MATLAB when the input data are: The frequency of operation ,the substrate (thickness, electric

permittivity and loss tangent), where the thickness of the substrate must be satisfy the equation (1)[5].

ℎ ≤

_{4𝑓𝑓√𝜀𝜀−1}^𝑐𝑐 ^. ⁽¹⁾

Where:

ε = dielectric constant of the substrate h = height of the substrate.

c = the air velocity f= operating frequency

Thus, the effective dielectric constant εeff must be obtained to account for fringing and wave propagation in the line.

The εeff value is slightly lower εr because the fringing fields around the periphery of the label are not confined in the dielectric substrate, but are also distributed in the air. The effective dielectric constant has values in the range of 1 < εeff <εr. but when the dielectric constant of the substrate is much larger than unity (ε𝑟𝑟 »1), the εeff value will be closer to the value εr of the substrate [2].

where:

w/h> 1

𝜀𝜀𝜀𝜀𝑓𝑓𝑓𝑓=𝜀𝜀𝑟𝑟+ 1

2 + 𝜀𝜀𝑟𝑟 −1

2��1 + 12ℎ 𝑤𝑤�

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where:

εeff = effective dielectric constant εr = dielectric constant of the substrate h = height of the dielectric substrate

the dimensions of the patch antenna along its length were extended at each end by Δ𝐿𝐿 distance, which is based on the effective dielectric constant εeff and aspect ratio.

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The First National Conference on Electronics and New Technologies (NCENT’2015)

May 19-20, M'Sila, Algeria

∆𝐿𝐿= 0.412ℎ(𝜀𝜀𝜀𝜀𝑓𝑓𝑓𝑓+ 0.3)�𝑤𝑤ℎ+ 0.264�

(𝜀𝜀𝜀𝜀𝑓𝑓𝑓𝑓 −0.258)�𝑤𝑤ℎ+ 0.8� (3) The effective length of the antenna is:

𝐿𝐿𝜀𝜀𝑓𝑓𝑓𝑓=𝐿𝐿+ 2∆𝐿𝐿 (4) the width which results in a good efficiency, and good radiation yields:

𝑤𝑤= 1

2𝑓𝑓𝑟𝑟�𝜇𝜇0𝜀𝜀0� 2 𝜀𝜀𝑟𝑟+ 1

The actual length of the patch can then be determined by

𝐿𝐿= 1

2𝑓𝑓𝑟𝑟�𝜇𝜇0𝜀𝜀0�𝜀𝜀𝜀𝜀𝑓𝑓𝑓𝑓−2∆𝐿𝐿

The conductance of the patch can be represented in the form [2]:

𝐺𝐺1 =� 1 90�𝑤𝑤

𝜆𝜆0�² 𝑤𝑤 ≪ 𝜆𝜆0 1

120�𝑤𝑤

𝜆𝜆0�² 𝑤𝑤 ≫ 𝜆𝜆0

𝑍𝑍𝑍𝑍𝑍𝑍= 1

𝑌𝑌𝑍𝑍𝑍𝑍=𝑅𝑅𝑍𝑍𝑍𝑍= 1 2𝐺𝐺1

Figure1. rectangular patch antenna

III. MINIATURIZATION OF PATCH ANTENNA (HFSS SOFTWARE)

We consider the patch antenna shown with dimensions optimized for a 10 GHz resonance frequency and a substrate relative permittivity ὲ=

2.1.

The second multilayered microstrip line analyzed and simulated is the doublelayered microstrip shown in Fig. 2.This antenna contains two different dielectric materials between the top conductor and the lower ground plane.A conformal mapping technique determines the characteristic impedance and effective dielectric constant of the doublelayered microstrip[5]:

𝑞𝑞1 =ℎ1 2ℎ�1 +𝜋𝜋

4−ℎ 𝑤𝑤𝑙𝑙𝑍𝑍 �𝜋𝜋

ℎ𝑤𝑤𝑠𝑠𝑍𝑍𝑍𝑍 𝜋𝜋ℎ1 𝜋𝜋ℎ12ℎ

2ℎ +𝑐𝑐𝑐𝑐𝑠𝑠𝜋𝜋ℎ1

2ℎ ��

𝑞𝑞2 = 1− 𝑞𝑞1−1 2𝑙𝑙𝑍𝑍 �

𝜋𝜋ℎ 𝑤𝑤 −1 𝑤𝑤ℎ

�

𝜀𝜀𝜀𝜀𝑓𝑓𝑓𝑓=𝑥𝑥 − (𝑞𝑞1 +𝑞𝑞2)² 𝜀𝜀𝑟𝑟1𝑞𝑞2 +𝜀𝜀𝑟𝑟2𝑞𝑞1

𝑥𝑥= 1− 𝑞𝑞1− 𝑞𝑞2 +𝜀𝜀𝑟𝑟1𝜀𝜀𝑟𝑟2

To show the impact of a substrate ,we consider four types of materials for the substrate with the same dimensions than antenna 10 GHz. The next table summarizes the case of antenna to simulate

;after we use the software HFSS v13 for the simulation and see the behavior all antennas and compare with the first antenna for 10 GHz, here are all results:

TABLE 1 Results obtained in the simulation by HFSS

material Fr of

resonance

bandwidth reduction material 1 ὲ=2.1,µ=1 10 GHz 552 MHz 0%

material 2 ὲ=5.5,µ=1 9.5 GHz 201MHz 5%

material 1+1mil thin

film ὲ=2.1, µ=12 9.15 GHz 502MHz 8.5%

material 1+2mil thin

film ὲ=2.1, µ=12 8.60 GHz 402MHz 14%

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(10)

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The First National Conference on Electronics and New Technologies (NCENT’2015)

May 19-20, M'Sila, Algeria

Figure2. A multilayer antenna

Figure3 return loss of fundamental antenna

Figure4 return loss of all antennas

Figure5 gain of all antennas

Figure6 imaginary impedance of all antennas

Figure7 real impedance of all antennas

5.00 7.50 10.00 12.50 15.00

Freq [GHz]

-17.50 -15.00 -12.50 -10.00 -7.50 -5.00 -2.50 0.00

dB(St(1,1))

Patch_Antenna_ADKv1

Return Loss ANSOFT

Curve Info dB(St(1,1)) Setup1 : Sweep1

-200 -150 -100 -50 0 50 100 150 200

-25 -20 -15 -10 -5 0 5 10

GainTotal - Freq=10GHz (dB)

Theta [deg]

material 1 material 2 material 1+1mil thin film material 1+2mil thin film

8 9 10 11 12

-200 -100 0 100 200

im(Zt(patch_T1,patch_T1))

Frequence [GHz]

8 9 10 11 12

0 50 100 150 200 250 300 350

re(Zt(patch_T1,patch_T1))

Frequence [GHz]

4 5 6 7 8 9 10 11 12 13

-20 -15 -10 -5 0

(St(1,1)) (dB)

Frequence [GHz]

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The First National Conference on Electronics and New Technologies (NCENT’2015)

May 19-20, M'Sila, Algeria

TABLE 2 Results obtained in the simulation by HFSS

material Fr of

resonance Gain (dBi)

Impedance input material 1 ὲ=2.1,µ=1 10 GHz 6.65 35-j0.51 material 2 ὲ=5.5,µ=1 9.5 GHz 5 42-j5.18 material 1+1mil thin

film ὲ=2.1, µ=12 9.15 GHz 7.8 35-j0.51 material 1+2mil thin

film ὲ=2.1, µ=12 8.60 GHz 9 35-j0.51

we find that the added film is given a good result for the miniaturization and the improvement of the performance of the antenna.

IV. CONCLUSION

The antenna printed on the substrate material1 + 2mil thin layer is more efficient in terms of resonant frequency, as printed on the substrate material 2. This is explain by the fact that the effective permeability of the first substrate is larger compared to the other simulated materials, where magnetic and dielectric losses are lower or negligible.

References

[1] Howell, J., "Microstrip antennas,“ Microstrip Antennas”,1972, vol.10, no., pp.177,180, Dec 1972 [2] A H. Mosallaei and K. Sarabandi,“ -Dielectrics In

Electromagnetics: Concept And Applications”, IEEE Transactions on Antennas and Propagation, vol. 52, no. 6, pp. 1558– 1567, June 2004.

[3] H. Mosallaei and Y. Rahmat-Samii, “Band-Gap And Effective Dielectric Materials In Electromagnetics”, Characterization and applications in nanocavities and waveguides,” IEEE Trans. Antennas Propagat., vol. 51, pp.

549–563, Mar. 2003.

[4] T. Le Nadan, J. P. Coupez, S. Toutain, and C. Person,

“Optimization And Miniaturization Of A Filter/Antenna Multi-Function Module Using A Composite Ceramic-Foam Substrate,” in Proc. IEEE MTT-S Int. Symp., Anaheim, CA, June 12–19, 1999.

[5] R.C. Hansen and M. Burke, , “Antenna With Magneto- Dielectrics”,, Microwave and Optical Technology Letters, vol. 26, no. 2, pp. 75–78, 2000.

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