Low Profile Dual-Polarized Wideband Antenna

Abdul Sattar Kaddour1, Serge Bories1, Anthony Bellion2 and Christophe Delaveaud1 1CEA, LETI, MINATEC Campus, Univ. Grenoble-Alpes, 38054 Grenoble, France

2CNES 18 avenue Edouard Belin, 31401, Toulouse, France

Abstract - A low profile dual-polarized unidirectional

wideband antenna based on two crossed magneto-electric dipoles is proposed. The antenna consists in folding the radiating element, the height of the radiation element is reduced to 0.11λ0

where λ0 is the wavelength at the lowest operation frequency for a standing wave ratio (SWR) <2 corresponding to a reduction factor of 37%. The antenna has been prototyped using 3D

printing technology and evaluated in an anechoic chamber. The measurement results are in excellent agreement with simulations. The measured input impedance bandwidth is 54.2% from 1.8

GHz to 2.9 GHz with SWR<2.

Index Terms — wideband antenna, magneto-electric dipole, dual polarized, unidirectional radiation, 3D printing.

1. Introduction

Recently, many efforts has been made to design wideband

antennas satisfying telecommunication requirements such as

wide impedance matching, unidirectional and stable radiation

pattern with low profile and light weight needs. The state of

art shows that “Magneto Electric” dipole antennas proposed

by K. M. Luk [1]-[2] are promising solutions with excellent

radiation characteristics and wide impedance matching. These

antennas are based on the concept of complementary antenna

or Huygens source [3]. However, these antennas suffer from

large height size. In order to reduce the antennas height many

techniques were proposed as dielectric loading materials [4]

or folding structure [5].

In this paper, we propose a method for reducing the height

of the dual-polarized wideband magneto-electric dipole

antenna presented in [2] by folding the antenna structure.

Antenna miniaturization can be achieved by increasing the

current path length. The height of the proposed radiating

element is only 0.11λ0, which is reduced by 37% comparing

with the original design.

2. Antenna Design

A 3D view of the proposed antenna is presented Fig. 1(a),

the antenna consists of four horizontal plates operate together

as two crossed electric dipoles. Each horizontal plate is

shorted to the ground plane through two vertical folded plates

Fig. 1(b). Each adjacent vertically oriented plates and the

ground between them act like a magnetic dipole. These

elements form two crossed magneto-electric dipoles

generating a dual polarization at ± 45°.

The antenna is excited by two “Г” shaped probes (Fig. 1.(c))

built using three portions of PCB on RT5870 substrate having

a thickness of 0.8 mm and relative permittivity of 2.3. These

probes are orthogonally placed in the gaps between the

vertical folded plates. The port 1 is the lower probe and the

port 2 is the higher probe. Two 50 Ω SMA connectors are

placed under the ground plane and connected to the two

feeding probes. The shorter and the higher probes excite the

+45° and -45° polarization respectively.

(a)

(b) (c)

Fig. 1. 3D view of the proposed antenna.

To improve the radiation characteristics the magneto-

electric dipoles are mounted on a square cavity. The position

and the dimension (, ) of the folded part of the vertical

plates are optimized to obtain a maximum impedance

bandwidth while maintaining an electrically small size of the

radiation element. Detailed dimensions of the antenna

structure are summarized in Table 1.

(a) (b)

Fig. 2. a) Photo of 3D printed horizontal and vertical

folded plates, b) Photo of the prototyped antenna.

Proceedings of ISAP2016, Okinawa, Japan

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Each horizontal plate and vertical plates where combined in

a single piece and fabricated by 3D printing technology (Laser

Sintering) in Plastic PC/ABS and electroplated with a 50 µm

copper thickness. These pieces have a granular finishing due

the 3D printing technique and a dark color caused by copper

oxidation see Fig. 2. The antenna total weight is 105 g.

TABLE I

Dimensions of the proposed antenna (mm)

Parameter G S L w ℎ ℎ

Value 112 47 6.5 27 14 2 16

Parameter t

Value 1 1 10 15.5 36 13 3

Parameter

Value 17.3 36 15 2.8 5 4.5 6.5

3. Results and discussion

The simulated and measured standing wave ratio (SWR)

and total realized gain from Port 1 and Port 2 are shown in the

Fig. 2. It can be seen that the antenna operates from 1.8 to

3.2 GHz with a bandwidth of 56% (SWR<2) and from 1.77 to

3.14 GHz with a bandwidth of 55.8% (SWR<2) for ports 1

and Port 2, respectively, the common bandwidth of the two

ports is 54.2% (SWR <2). Over the operating frequency the

measured broadside gain at ( = 0°) for port 1 and for port 2

are 7.2 dBi ± 1.5 dB. The difference of 1 dB between

simulation and measurement is probably due to the low

conductivity of copper used in fabrication process and the

difference between port 1 and Port 2 is due to the dissymmetry

between the two excitation probes. The coupling between Port

1 and Port 2 is below -25 dB in the operation band.

Fig. 3. Simulated and measured SWRs and gains of the

low profile dual polarized antenna.

The proposed radiation element of the antenna has a

dimension of 0.36 × 0.36 × 0.11 compared to the

antenna in [2] where the radiation element has a dimension of

0.33 ×0.33 ×0.18where is the wavelength at the

lowest operation frequency for SWR<2 (without taking into

account the ground plane dimension).

The simulated and measured normalized realized gain

radiation pattern at 1.8 GHz and 3 GHz for port 1 and port 2

at = +45° and = −45° respectively are depicted in

Fig. 4. The radiation patterns are identical for both ports. At

1.8 GHz the -3dB beam for both ports is 72° and 75°

respectively. At 3 GHz, the antenna electrical size becomes

too large which explains the poor beam width of 45° and 43°

for port 1 and port 2 respectively. The cross-polarization level

is always less than -19 dB.

Fig. 4. Simulated and measured radiation patterns.

4. Conclusion

A low profile dual-polarized antenna based on magneto-

electric dipole antenna has been designed and prototyped.

Measured and simulated results are in good agreement, the

antenna has an impedance bandwidth of 54.2% with SWR<2

and a broadside gain varying from 6 to 9 dBi. These

performances prove the feasibility and reliability of the 3D

printing technology in wireless communication for low cost

fabrication. The radiation element height was reduced to

0.11λ0 corresponding to a reduction factor of 37% compared

to [2]. In the next prototypes, 3D printed pieces will be

electroplated with a better quality copper to improve the

conductivity of the radiation elements.

Acknowledgment

The authors wish to thank the CNES, French space agency

for partially funding this work.

References

[1] Luk, K. M., & Wong, H. (2006). A new wideband unidirectional

antenna element. Int. J. Microw. Opt. Technol, 1(1), 35-44.

[2] Mingjian Li and Kwai-Man Luk, "Wideband Magnetoelectric Dipole Antennas With Dual Polarization and Circular Polarization," in IEEE

Antennas and Propagation Magazine, vol. 57, no. 1, pp. 110-119, Feb.

2015. [3] A. Clavin, "A new antenna feed having equal E- and H-plane patterns,

"iRE Trans. Antennas Propag., vol. 2, no.3, pp. 113-119, Jul. 1954.

[4] Siu, L.,Wong, H., & Luk, K. M. (2009). A dual-polarized magneto-electric dipole with dielectric loading. Antennas and Propagation, IEEE

Transactions on, 57(3), 616-623.

[5] Mingjian Li; Luk, Kwai-Man, "A low-profile magneto-electric dipole antenna," in Electromagnetics; Applications and Student Innovation

(iWEM), 2012 IEEE International Workshop on , vol., no., pp.1-2, 6-9

Aug. 2012.

Sim. Co Polar Sim. Cx Polar Meas. Co Polar Meas. Cx Polar

Port 1 at 1.8 GHz

-20 -10 0 +90°

+60°

+30°

0°

-30°

-60°

-90°

-120°

-150°

+180°

+150°

+120°

dBi

-20 -10 0 +90°

+60°

+30°

0°

-30°

-60°

-90°

-120°

-150°

+180°

+150°

+120°

dBi

-20 -10 0 +90°

+60°

+30°

0°

-30°

-60°

-90°

-120°

-150°

+180°

+150°

+120°

dBi

-20 -10 0 +90°

+60°

+30°

0°

-30°

-60°

-90°

-120°

-150°

+180°

+150°

+120°

dBi

Port 2 at 1.8 GHz

Port 1 at 3 GHz Port 2 at 3 GHz

1.5 1.7 1.9 2.1 2.3 2.5 2.7 2.9 3.1 3.3 3.50

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

5.5

6

Frequency (GHz)

SW

R

1.5 1.7 1.9 2.1 2.3 2.5 2.7 2.9 3.1 3.3 3.50

1

2

3

4

5

6

7

8

9

10

11

12

Realiz

ed g

ain

at θ

=0°(

dB

i)

Sim. (Port 1) Sim. (Port 2) Meas. (Port 1) Meas. (Port 2)

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