Considering of Circularly Polarized Antenna byCombining Two MACKEYs
Keito Yokoe (1), Kota Hakamata (1), Shigeru Makino (1), Kenji Itoh (1)(1) Kanazawa Institute of Technology 7-1 Ogigaoka, Nonoichishi Ishikawa, Japan
B1995149@planet.kanazawa-it.ac.jp
Abstract— Herein, a meta-surface-inspired antenna chipdeveloped by the KIT EOE Laboratory (MACKEY) which is
sufficiently robust to a metal object proposed. By combining two
MACKEYs, we propose an antenna that radiates circularly
polarized waves.

I. INTRODUCTION
An electrically small antenna, named MACKEY basictype, which is robust to a metal object, has been proposed [1].
In addition, a thinner and improved MACKEY II wasproposed [2].

that radiated linearly polarized waves. Hence, two MACKEY
IIs of the same size were combined in an orthogonalarrangement. As Fig. 3 shows, the two MACKEY IIs shared apart of the model. By feeding them with a phase difference, itwas believed that circularly polarized waves could oscillate. In
this study, an impedance matching model was used with asingle-port power supplied with an aligned grid plate length
and width.
To feed the two antennas, a 0° current was applied to feed
point 1, and a 90°current was applied to feed point 2, as thelower part of Fig. 3 shows.

Fig. 1 illustrates the MACKEY II designed for the Wi-Fi
2.4GHz band. The model is a three-layered structure
comprising a grid plate, an antenna plate, and a metal plate indescending order, with a dielectric filled between them.
Impedance matching is performed based on the grid width gand antenna length ℓ. Fig. 2 depicts the analysis results of thevoltage standing wave ratio (VSWR) characteristics in freespace and on metal. The analysis results in Fig. 2 show that
MACKEY II works well on metal.

Fig. 3. Simplified diagram of the circularly polarized antenna

III. STRUCTURE OF MACKEY C3 TYPE
Fig. 1. Model diagram of the MACKEY II

Based on the aforementioned proposal, the name of themodel with three grid plates and two antennas was theMACKEY C3 type, and Fig. 4 presents the structural diagram.
The stacked structure was the same as in MACKEY II, withan AMC substrate having a thickness of 2 mm and an antenna
position of 1 mm. A current with a phase of 0°and 90° wassupplied to each of the two feed points shown in the figure.
Impedance matching was performed by varying the length ℓof the antenna and the height and width g of the grid. Inaddition, the slit width s was varied to adjust the axis ratio.

Fig. 2. VSWR of the MACKEY Ⅱ

II. PROPOSAL FOR CIRCULAR POLARIZATION MACKEY
To radiate a circularly polarized wave, it was necessary toadd a 90° phase difference between two orthogonal linearlypolarized waves. The common MACKEY II was an antenna

The top and bottom widths of the antenna substrate denotedby L were 81.8 mm and the antenna length ℓ was 29 mm.

Fig.4 Model diagram of circularly polarization MACKEY C3IV. ANALYSIS RESULTS
Fig. 5 shows the analysis results of VSWR characteristics.
The results in free space are depicted by black lines, and theresults for metal are depicted by red lines. The VSWR was lessthan 3 dB in both free space and on metal, and there was nosignificant difference in the specific bandwidth. Therefore, theWi-Fi 2GHz bandwidth was satisfied.

Fig.6 Axial ratio characteristic.

Fig. 6 shows the axial ratio characteristics. Axial ratio
characteristics of less than 3 dB were obtained over a wide
range, both in free space and on metal. Therefore, it wasobserved that the axial ratio characteristics did not affect themetal.
Fig. 7 shows the radiation pattern diagram. The solid lines
indicate left-handed circular polarization, and the dashed lines
indicate right-handed circular polarization. Moreover, thedashed lines in the figure show that this antenna was a righthanded circularly polarized antenna. The radiation on the metalradiates in the x-direction, similar to the radiation in free space.

Fig.7 Radiation patterns of circularly polarized waves for two models.

V. CONCLUSION
Here, a circularly polarized MACKEY was proposed. Thismodel functioned as a circularly polarized antenna bycombining two MACKEYⅡs rotated by 90° and feeding eachantenna with a phase difference of 90°. It was also
demonstrated that this antenna could operate on a metal, which
was the original feature of the basic-type MACKEY. In thefuture, the miniaturization of this antenna should be considered.
ACKNOWLEDGMENT
This work was supported by JST CREST Grant Number
JPMJCR20Q1, Japan.
REFERENCES
Fig.5 VSWR characteristic.

[1]
[2]

T.MOROYA et al, “AMC Inspired Small Antenna MACKEY,”
IEICE. Trans. Commun, vol. J99-B, no. 9, pp. 786794, Sep. 2016
K.MIYASHITA et al, “MACKEY II with reduced thickness by using anew structure,” IEEE APS-2020, pp599-600, Jul.2020