Development of Circular Polarization MACKEY
Keito Yokoe, Keisuke Miyashita，Kota Hakamata，Shigeru Makino，Kenji ItohKanazawa Institute of Technology
7-1 Ogigaoka, NonoichishiIshikawa, 921-8501 Japan
C6101374@planet.kanazawa-it.ac.jp
Abstract— In this study, a meta-surface-inspired antenna chipdeveloped by the KIT EOE Laboratory (MACKEY) that is
sufficiently robust to a metal object, has been proposed. The
MACKEY transmits circularly polarized signals by combining
multiple antennas and substrates.
Keywords— MACKEY; WiFi-2GHz; meta-surface inspiredantenna; AMC substrate; circularly polarized wave;

I. INTRODUCTION
An electrically small antenna, named MACKEY basic-type,which is sufficiently robust to a metal object, has been proposed[1]. In addition, a reduced-thickness model, MACKEY II has
been proposed [2].

II. PROPOSAL FOR THE CIRCULAR POLARIZATION
MACKEYTo radiate a circularly polarized wave, it is necessary to add
a 90° phase difference between two orthogonal linearlypolarized waves. The normal MACKEY II is an antenna thatradiates the linearly polarized waves. Hence, two MACKEY IIs
of the same size were combined in an orthogonal arrangement.
The two antennas share a part of the grid plate, as shown in Fig.
3. By feeding them with a phase difference, it is believed thatcircularly polarized waves can oscillate. In this study, animpedance matching model was used with a single-port power
supply having aligned grid plate length and width.

AMC
substrate

h=1.0mmεr=2.58tanδ=0.0014
εr=2.58tanδ=0.0014①②③68.2mm

2.0mm

Antennasubstrate

t=2.0mmFig. 1 illustrates the MACKEY II designed for the Wi-Fi
2.4GHz band. The model is a three-layered structure comprisinga grid plate, an antenna plate, and a metal plate in descendingorder, with a dielectric filled between them. Impedance
matching is performed based on the grid width g and antenna
length ℓ. Fig.2 depicts the analysis results of the voltage standing
wave ratio (VSWR) characteristics in free space and on metal.
The analysis results in Fig.2 demonstrate that the MACKEY II
operates in both free space and metal.

Bird’s eye view

Feeding point
Side viewg=33.85mm

w=1mm

L=2×g + s=68.2mm

W=30mmg=33.85mm

L=2×g + s=68.2mmℓ=29.1mm

Fig. 3. Simplified diagram of the circularly polarized antenna

s=0.5mm①Grid plate②Antenna plate③Metal plate
Metal plate
DielectricFig. 1. Model diagram of the MACKEY II back feed type10987654321To feed the two antennas, a 0° current was applied to feed
point 1, and a 90°current was applied to feed point 2, as shownin the lower part of Fig. 3.

VSWR

III. DESIGHNED CIRCULARLY POLARIZATION MACKEY.

in_free_space
on_metal
2.2

2.3

2.4
2.5
2.6
Frequency[GHz]

2.7

2.8

Fig. 2. VSWR characteristics of the MACKEY basic typeIn this study, MACKEY that transmits circularly polarized waves bycombining multiple antennas and substrates is proposed.

Based on the aforementioned proposal, a model with three
grid plates and two antennas is shown in Fig. 4. The stacked
structure is the same as in the MACKEY II, with an AMC
substrate having thickness 2 mm and an antenna position of 1mm. A current with a phase of 0°and 90° is supplied to each of
the two feed points shown in the figure.
Impedance matching is performed by varying the length ℓ of
the antenna and the height and width g of the grid. In addition,
the slit width s was varied to adjust the axis ratio.

As a result, the top and bottom widths of the antenna substrate
denoted by L are 81.2 mm and the antenna length ℓ is 29 mm.

Fig.4 Model diagram of circularly polarization MACKEY

Fig.6 Axial ratio characteristic.

The results of the analysis of the VSWR characteristics areshown in Fig. 5. The results in free space are depicted by theblack lines, and the results for metal are depicted by the red lines.
The VSWR is less than 3 dB in both free space and on metal,
and there is no significant difference in the specific bandwidth.
Therefore, the Wi-Fi 2GHz bandwidth is generally satisfied.
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 can beobserved that the metal is not affected by the axial ratio
characteristics.
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 is 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.

IV. CONCLUSION
In this paper, a circularly polarized MACKEY is proposed.
This model functions 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 metal, which was the original
feature of the basic-type MACKEY. Future studies will include
the feeding circuit for this antenna.
V. ACKNOWLEDGMENTS
This work was supported by the JST CREST Grant Number
JPMJCR20Q1, Japan.
REFERENCES[1][2]
Fig.5 VSWR characteristic.

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 model with reduced thickness,”2021 15th European Conference on Antennas and Propagation (EuCAP),
pp1-4, Mar.2021