2022 IEEE International Workshop on Electromagnetics: Applications and Student Innovation Competition (iWEM), Narashino,Japan

Circularly Polarized MACKEY with Improved
Axial Ratio
Keito Yokoe
Department of Electrical andElectronic Engineering
Kanazawa Institute of Technology
Nonoichishi,Isikawa,Japanb1995149@planet.kanazawa-it.ac.jp

Kota Hakamata
Department of Electrical andElectronic Engineering
Kanazawa Institute of Technology
Nonoichishi,Isikawa,Japanb1745887@planet.kanazawa-it.ac.jp

Shigeru Makino
Department of Electrical andElectronic Engineering
Kanazawa Institute of Technology
Nonoichishi,Isikawa,Japanmakino@neptune.kanazawa-it.ac.jp

Kenji ItohDepartment of Electrical andElectronic Engineering
Kanazawa Institute of Technology
Nonoichishi,Isikawa,Japanitoh.kenji@neptune.kanazawa-it.ac.jp
Abstract— A MACKEY (Metamaterial Antenna Chipdeveloped by KIT EOE LaboratorY) that is sufficiently robust
to metal object proposed. By combining two such MACKEYs,
we develop an antenna that radiates circularly polarized waves
with a good axial ratio.
Keywords— MACKEY, circular polarization, metasurfaceinspired antenna, artificial magnetic conductor substrate

I. INTRODUCTION
A small electrical, termed MACKEY (MetamaterialAntenna Chip developed by KIT EOE LaboratorY) basictype, which is robust to metal object, has been proposed [1].
In addition, an unbalanced MACKEY, which is thinner andimproved as a one-port power feed, has been developed [2].
Fig. 1 shows the unbalanced MACKEY designed for theWi-Fi 2.4GHz band. It is a three-layered structure consistingof a grid plate, an antenna plate, and a metal plate indescending order, with dielectric-filled materials between
them. Impedance matching is performed based on the grid
width g and antenna length ℓ. Fig. 2 shows the analysis
results of the voltage standing wave ratio (VSWR)
characteristics in free space and on metal these results show
that. The unbalanced MACKEY works properly on metal.

II. PROPOSITION OF CIRCULAR POLARIZATION
MACKEYTo radiate a circularly polarized wave, a 90 ° -phasedifference needs to be added between two orthogonallinearly polarized waves. A typical MACKEY radiatedlinearly polarized waves. Hence, two unbalanced MACKEYsof the same size can be combined orthogonally to obtaincircularly polarized waves. Fig. 3 shows the two unbalanced
MACKEYs as part of the circular polarization system. By
feeding them with a phase difference, it was believed thatcircularly polarized waves could be oscillated. Three power
supply position patterns were compared, and the structurewith the best performance was adopted. [3]To feed the two antennas, current with a phase of 0° and90° were applied to feed point 1 and 2, respectively as shownin the lower part of Fig. 3.

Fig. 3. Simplified diagram of the circularly polarized MACKEY

III. STRUCTURE OF MACKEY C3 TYPE
Based on the aforementioned proposal, the model withthree grid plates and two antennas was termed MACKEY C3
type. The structure is shown in Fig. 4. The stacked structure is
the same as that in the unbalanced MACKEY, with anartificial magnetic conductor substrate with of 2 mm
thickness and an antenna position of 1 mm. In the actual
design, a hot melt bond film of 0.06mm (blue in the figure)was used as the adhesive. A current with a phase of 0°and 90°
was supplied to each of the two feeding points shown in thefigure.

Fig. 1. Model diagram of the unbalanced MACKEY

Fig. 2. Voltage standing wave ratio (VSWR) of the unbalanced MACKEY

978-1-6654-3238-2/22/$31.00 ©2022 IEEE

Impedance matching was performed by varying the lengthℓ of the antenna, and the height and width g of the grid. A122

2022 IEEE International Workshop on Electromagnetics: Applications and Student Innovation Competition (iWEM), Narashino,Japanadditionally, to reduce the interference of the current by thetwo feeding points, the slit width, s, was widened to 8 mm.
[4]. The slit width, s, was varied to adjust the axis ratio.
The top and bottom widths of the antenna substrate denotedas L were 81.2 mm and the antenna length ℓ was 29 mm.

Fig.6 Axial ratio characteristics of MACKEY C3.

Fig. 4. Model diagram of the MACKEY C3

IV. ANALYSIS RESULTS
Fig. 5 shows the results of the analysis of the VSWR
characteristics. The results in free space are indicated by blacklines, and the results for metal are depicted by red lines. TheVSWR was less than 3 dB both in free space and the metal,and the, difference in the specific bandwidth was insignificant.
Therefore, the Wi-Fi 2GHz bandwidth was satisfied.

Fig.7 Radiation patterns of MACKEY C3.

V. CONCLUSION

Fig.5 VSWR characteristics.

The axial ratio characteristics are shown in Fig. 6. Axial
ratio characteristics of less than 3 dB were obtained over awide range, both in free space and on metal. Therefore, themetal was not influenced by the axial ratio characteristics.
The diagram of the radial patterns obtained is shown inFig. 7. The solid and dashed lines indicate left-handed andright-handed circular polarization, respectively. The large
value of the solid line indicates that this antenna radiates lefthanded circularly polarized waves. In addition, the values ofradiation gain are good.

In this study, a circularly polarized MACKEY wasproposed. This model functioned as a circularly polarized
antenna by combining two unbalanced MACKEYs oriented
90° to each other and feeding each antenna with a phasedifference of 90°. The two unbalanced MACKEYs share agrid plate; however, the interference between them is reduced
by separating the feeding points this antenna could operate onmetals, which was the original characteristic of the basic-type
MACKEY. In the future, miniaturization of this antennashould be considered.
REFERENCES
[1]
[2]
[3]
[4]

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T.Moroya, et al., “AMC-inspired small antenna MACKEY,” IEICE.
Trans. Commun., vol. J99-B, no. 9, pp. 786–794, Sept
K.Miyashita et al,” Feasibility study of an unbalanced MACKEY type
R with enhanced robustness on metal” ISAP2021 oct.
K.Yokoe et al,” Considering of Circularly Polarized Antenna byCombining Two MACKEYs” IEEE AP-S2022 Jul.
K.Yokoe et al” Development of Circular Polarization MACKEY”
ICETC2021, #C000063, Dec.