978-1-6654-7962-2/22/$31.00 ©2022 IEEE

Two-dimensional arraying of unbalanced MACKEY
Hajime Suzuki
Department of Electrical andElectronic Engineering
Kanazawa Institute of Technology
Nonoichi,Ishikawa,Japanb1845590@planet.kanazawa-it.ac.jp

Hayato Ide
Department of Electrical andElectronic Engineering
Kanazawa Institute of Technology
Nonoichi,Ishikawa,Japanb1914111@planet.kanazawa-it.ac.jp

Michinori Yoneda
Department of Electrical andElectronic Engineering
Kanazawa Institute of Technology
Nonoichi Nonoichi,Ishikawa,Japanb1812587@planet.kanazawa-it.ac.jp

Koki Iijima
Department of Electrical andElectronic Engineering
Kanazawa Institute of Technology
Nonoichi,Ishikawa,Japanb1813979@planet.kanazawa-it.ac.jp

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

Kenji Itoh
Department of Electrical andElectronic Engineering
Kanazawa Institute of Technology
Nonoichi Nonoichi,Ishikawa,Japanitoh.kenji@neptune.kanazawa-it.ac.jp

Abstract—In this study, we examine a compact and thinmetasurface-inspired antenna chip developed by the KIT EOELaboratory (MACKEY) that can operate in free space and on
metals. In particular, MACKEY II is examined when it isconverted to a two-dimensional array with element spacing λ/4
and λ/2.

XZ(1)Grid Plate

With recent advancements in the Internet of Things, themetasurface-inspired antenna chip developed by the KIT EOELaboratory (MACKEY) [1] has been established as a compact
antenna that is less susceptible to the influence of thesurrounding metal. In this study, we investigated MACKEY
arraying to improve the gain and change directivity of wirelesspower transmission, that is, a technology that wirelesslytransmits power. MACKEY can be easily arrayed with anelement spacing of λ/4.

①②③Feeding point

L=2×g + s=67.8

w=1.5

W=37
gw=30

g

s=0.5
①Grid plateℓ=23.9copper

L=2×g + sFeeding point②Antenna plate

Port5Port7
Port60.06

t=2.0

tt=1.0Feeding point
ww=1.1

L=160.8

W=118.81

g=36.27

(1)
(2)
(3)

ℓ=36.26

Port2Port4Port1Port3

Copper
NPC-F260A
R1661

s=5(2)Antenna Plate(3)Metal Plate

Fig. 3. Element spacing λ/2 model diagram

Fig. 1 shows a model diagram of MACKEY II for theWiFi 2.4 GHz band modeled in this study. In particular,
MACKEY II [2] was arrayed into two dimensions withelement spacings λ/4 and λ/2, as shown in Figs. 2 and 3. Theelement spacings λ/4 and λ/2 have 16 and 4 elements,respectively. The element spacing λ/4 allows for twopolarization sharing. The dipole elements were arrayed in theZ direction. In this study, the difference in element spacing
was examined.

g=33.65(3)Metal Plateh=1.0(1)Grid Plate

h=1.0

R1661

Fig. 2. Element spacing λ/4 model diagram

II. CONSIDERATION OF ONE-DIMENSIONAL ARRAY

t=2.0(2)Antenna Plate

CopperNPC-F260A
Port8

ww=0.8

Port4Port2
s=5Port1ℓ=33.26

W=117.4

I. INTRODUCTION(2)(3)

Feeding point

L=158.2
g=35.8

Keywords—MACKEYⅡ, WiFi-2.4GHz, array

(1)

0.06

h=1.0
tt=1.0

Port3

t=2.0

Y

③Metal plate

NPC-F260AFig. 1. Model diagram of MACKEYⅡThis work was supported by JST CREST (Grant Number
JPMJCR20Q1), Japan.

III. ANALYSIS RESULTS
For analytical conditions, we assumed an ideal powerfeeding circuit with an equal amplitude and in-phase. Theanalysis software used was HFSS from Ansys. Fig. 4compares the reflection loss for element spacings λ/4 and λ/2when the antenna length ℓ was varied. When the antenna
length ℓ was 33.26 mm, the element spacing λ/4 exhibited thelowest reflection loss. However, when the antenna length ℓ
was 36.26 mm, the element spacing λ/2 exhibited the lowest
reflection loss. Fig. 5 shows the reflection loss with varying
antenna width, ww, for antenna lengths of 33.26 mm and36.26 mm with element spacing of λ/4 and λ/2, respectively.
The lowest reflection loss was observed for element spacing
λ/4 when the antenna width was 0.8 mm, and for element
spacing λ/2 when the antenna width was 1.1 mm. Figs. 6 and7 show the power standing wave ratio (VSWR)
characteristics. The element spacing λ/4 satisfied the wifi 2.45
GHz bandwidth, and the length of the grit plate was changed
to 35.8 mm. Therefore, both λ/4 and λ/2 satisfied the wifi 2.45
GHz bandwidth. Figs. 8, 9, and 10 show the radiation patternsof the composite arrays. The gains when feeding the dipole
elements in the Z direction with element spacing λ/4 were.

473

11.09 dBi in free space and 11.46 dBi on metal. The gains
when feeding the dipole elements in the Y direction were 8.31
dBi in free space and 11.41 dBi on metal. The gain in the Zdirection feeding was higher than that in the Y-direction. Thiscan be attributed to the larger side lobes in the Y-direction.
The gains for the element spacing λ/2 were 9.61 dBi in freespace and 12.08 dBi on the metal. Both λ/4 and λ/2 element
spacing improved the gain on the metal, as in conventional
MACKEY. The aperture efficiency calculated from theformula 4πS/λ^2 using the antenna area S was 93.02 and 69.70% when feeding the dipole elements in the Z- and Ydirections, respectively, and 79.92 % with element spacing
λ/2.

151050-5-10-15-20

X

151050-5-10-15-20

YfreeZ

Xon metal

2Return Loss [dB]Fig. 8. Radiation pattern when fed in Z direction with element spacing λ/4
1.5151050-5-10-15-20

10.5
025.26

30.26

35.26

40.26

Z

15
1050-5-10-15-20

XX

Y

Antenna Length ℓ [mm]Element spacing λ/2

Element spacing λ/4

Fig . 4. Reflection loss when antenna length changes

Return Loss [dB]

2free

1.5

on metalFig. 9. Radiation pattern when fed in Y direction with element spacing
λ/4

10.515 X
1050-5-10-15-20

00.5

1

1.5

2Antenna Width ww [mm]Element spacing λ/2

Element spacing λ/4

Fig. 5. Reflection loss when antenna width changes
9988775VSWR10VSWR

104

43

322615 Z
1050-5-10-15-20YX6free51
2.2

2.3

2.4

2.5

Frequency [GHz]port1

2.6Fig. 10. Radiation pattern with element spacing λ/2

12.7

2.2

port4

port3

2.3

2.4

2.5

Frequency [GHz]

port6

2.6

2.7

10109988775

VSWRVSWR44332We examined the element spacings λ/4 and λ/2 ofMACKEY II, which were particularly converted to a 2dimensional array. Both λ/4 and λ/2 have sharper directivity
and higher gain than the conventional MACKEY II, thereby
suggesting that arraying was effective. The gain in the frontal
direction was higher for the element spacing λ/4 than for λ/2,but the reflection loss was smaller for λ/2.

265

REFERENCES

11
2.2

2.3

2.4

2.5

Frequency[GHz]

2.6

2.7

port1

IV. CONCLUSIONS.

port8

Fig. 6 VSWR characteristics of element spacing λ/4

6on metal

2.2

2.3

2.4

2.5

Frequency[GHz]

port3

2.6

2.7

[1]
[2]

Fig. 7. VSWR characteristics of element spacing λ/2474

T.MOROYA et al, “AMC Inspired Small Antenna MACKEY,”
IEICE. Trans. Commun, vol. J99-B, no. 9, pp. 786794, Sep. 2016.
K.Miyashita, S.Makino, and K.Itoh, “Feasibility study of anunbalanced MACKEY type R with enhanced robustness on metal,” inISAP 2021, October