Feasible study of MACKEY II type R with
Enhanced Robustness on metal
Keisuke Miyashita，Shigeru Makino，Kenji ItohKanazawa Institute of Technology
7-1 Ogigaoka, NonoichishiIshikawa, 921-8501 Japanb1613494@planet.kanazawa-it.ac.jp
Abstract— In this study, a meta-surface-inspired antenna chip,developed by KIT EOE Laboratory (MACKEY), that issufficiently robust to a metal object and MACKEY II type R withenhanced robustness against metal is proposed. Moreover, theantenna width was optimized to obtain a wider operating
bandwidth.

II. NOVEL MACKEY II R TYPE WITH ENHANCED ROBUSTNESS

Keywords—MACKEY; WiFi-2GHz; Meta-surface inspiredantenna; AMC substrate; robustness

I. INTRODUCTION
A meta-surface-inspired antenna chip developed by KIT
EOE Laboratory (MACKEY) basic-type electrically small
antenna that is sufficiently robust to a metal object has been
proposed [1]. In addition, MACKEY II is proposed as a reducedthickness model of the MACKEY basic-type [2].
Fig. 1(a) shows the MACKEY II which is designed for theWi-Fi 2.4 GHz band. The model has a three-layer structure
comprising a grid plate, an antenna plate, and a metal plate indescending order, with a dielectric filled between them. Inaddition, Fig. 1(b) shows the model of the patch antenna with asimilar structure as a planar antenna. It’s designed to have thesame size as MACKEY II shown in Fig.1. Moreover, Fig.2
depicts the analysis results of VSWR characteristics in freespace and on metal of two models. The analysis results in Fig. 2
show that both MACKEY II and the patch antenna operates infree space and on metal.
g=33.85g=33.85①②

L=2×g + s=68.2③

w=1

εr=2.58tanδ=0.0014
εr=2.58tanδ=0.0014

W=30AMC
substrate

h=1.0

t=2.0Antenna
substrate①Grid plateℓ=29.1②Antenna plate③Metal plate(a)MACKEY II
W=45.2

Feeding point
Side view

W=45.2②

Metal plate

w=36.25εr=2.58tanδ=0.0014

W=45.2w=36.25①
t=2.0

L=2×g + s=68.2

s=0.5

Feeding point
Side view

DielectricUnit[mm]②Metal plate①Antenna plate(b)Patch Antenna

VSWRFig. 1. Model diagram of the MACKEY II and the patch antenna
10987654321

MACKEY_air
MACKEY_metal
Patch_air
Patch_metal

2.2

2.3

2.4

2.5

2.6

Section 1 showed that MACKEY II and the patch antenna
operates not only in free space but also on metal. However, there
is a frequency shift in the metal compared to that in free space.
Therefore, they do not fully satisfy the Wi-Fi 2.4 GHz
bandwidth (2.4–2.5 GHz) in free space or on metal. In a
conventional study, it was revealed that the effect on the metal
could be reduced by varying the vertical length of the antenna,
while the grid vertical width is fixed in the basic type [3].
Therefore, a similar study was performed on MACKEY II toreduce the frequency shift in free space and on metal. Fig. 3
illustrates a structural diagram of the MACKEY II type R(robustness type). In this study, as shown in Fig. 3, theoptimization of the vertical length of the antenna is performed
for front and back feed types, which enable feeding throughholes in MACKEY II, in consideration of actual modeling. Inthe two models, the grid vertical width gw was fixed at 30 mm,
and the antenna vertical length W was changed from 30 mm to
40 mm in increments of 1 mm. Thus, it is possible to determine
the vertical width of the antenna that represents the optimal
operating bandwidth. Here, the operating bandwidth indicatesthe relative bandwidth of the metal minus the frequency shift
between the free space and metal. Therefore, when thefrequency shift is small and the relative bandwidth is wide, theoperating bandwidth is also large. In addition, in this study,
impedance matching was performed on the metal, and the model
was analyzed in free space to examine the operating bandwidth.

2.7

2.8

Fig. 4 depicts the frequent shifts of the two models. As
shown in Fig. 4, the frequency shift decreases in both the models
as the substrate height W is increased; however, when the shift
decreases to a certain level, it generally levels off. In addition,Fig. 5 shows the operating bandwidth of the two models. As
shown in Fig. 5, the operating bandwidth increases as W
increases, but decreases slightly after increasing to a certainlevel, similar to the frequency shift shown in Fig. 4. When
comparing the frequency shift and operating bandwidth of thefront and back feed types, the front-feed type has better overall
performance; however, after W=37 mm, both models are
generally consistent.
Based on the results in Fig. 5, in this study, a model with anantenna width of W=37 mm is designed for both models tocreate a model with the smallest size possible and a wide
operating bandwidth.

Frequency[GHz]Fig. 2. VSWR characteristics of the MACKEY II and the patch antenna
In this study, MACKEY II type R was proposed, which has enhanced
robustness. It has been shown that MACKEY II type R reduced the frequency
shift978-1-7281-4670-6/21/$31.00
in free space and on metal compared ©2021
to the conventional
IEEE MACKEY.
941

APS 2021

gBack feed type
w=1mm

g

87766544L

33front_air
front_metal

2

12.2

②Antenna plate③Metal plateback_airback_metal

21ℓ

s=0.5mm①Grid plate

985③Metal plate②Antenna plate

gw=30W

s=0.5mm①Grid plate

109VSWRℓ

10VSWRw=1mmL

gw=30W

Front feed type

gg

2.3

2.4
2.5
2.6
Frequency[GHz]

2.7

2.8

2.2

2.3

(a)Front feed typeFig. 3. Structural diagram of MACKEY II type R

2.4
2.5
2.6
Frequency[GHz]2.7

2.8(b)Back feed typeFig. 7. VSWR characteristics of the MACKEY II type R

1.8

Frequency shift[%]

1.6X

Front feed type

1.4

1010

1.2

00

1-10-10

0.8

Y-20

0.6

ZX
X-20Z

Y

0.4
0.2

2.45GHz0303132333435363738W[mm]front_feed
back_feed

394010XBack feed type100-20

Theta_in_free_space-10-10-104Z00Fig. 4. Frequency shift of two models

XY面

10Y-20-20

X

Theta_on_metal

Operating bandwidth[%]

3.8
3.6
3.4

3.2
3Fig. 8. Radiation pattern of the MACKEY II type R

2.8
2.6

IV. CONCLUSION

2.4

2.2

In this study, a MACKEY II type R with enhanced
robustness on metal was proposed. When compared to the basicmodel, this model takes advantage of the feature of reducing thefrequency shift by varying the grid vertical width in the reducedthickness of MACKEY II. In this study, the antenna height wasoptimized by shifting the frequency and optimizing theoperating bandwidth, while the grid height was fixed at 30 mm
for the front and back feed types of MACKEY II. As a result,the antenna height of W=37 mm was determined to be the most
optimal for both models.

2303132333435363738
W[mm]front_feed
back_feed

3940

Fig. 5. Operating bandwidth of two models

III. DESIGHNED MACKEY II TYPE R
Based on the previous discussion, Fig.6 shows the model
diagram of the front-feed and back-feed types designed with
W=37mm. For both models, the AMC substrate thickness wasfixed at 2mm, and the antenna position was fixed to 1mm.
As a result of impedance matching of the two models, thewidth of the front feed type was 69.6 mm, and that of the backfeed type was 68 mm. Fig. 7 shows the analysis results of theVSWR characteristics of the two models. As shown in Fig. 7,
there is almost no frequency shift in free space and on the metal
for both models. However, while both models satisfy the Wi-Fi
2.4 GHz bandwidth in free space, they do not completely satisfy
the bandwidth of the metal. Fig. 8 shows the analysis results of
the radiation patterns of the two models. As shown in Fig. 8, theradiation is sufficient, both in free space and on metal.

②③g=33.75③Copper

REFERENCES

Back feed typeg=33.75

εr=2.58tanδ=0.0014②εr=2.58
tanδ=0.0014

ww=1①Grid plate

This work was supported by JST CREST Grant Number
JPMJCR20Q1, Japan.

ℓ=25.6②Antenna plate①Grid plate

ACKNOWLEDGMENT

L=69.6g=34.55

W=37
gw=30

t=2

①h=1

g=34.55

ww=1

①
W=37

εr=2.58tanδ=0.0014
εr=2.58tanδ=0.0014

gw=30

t=2

Front feed typeh=1

The analysis results for the front and back feed types almost
satisfied the Wi-Fi 2.4 GHz bandwidth in free space. Therefore,
the two designed models are found to have less frequency shift
than the conventional MACKEY II and wider bandwidth thanthe patch antenna. In addition, both models radiated well in freespace and on metal.

[1]③Metal plate
L=68

[2]

③Metal plate[3]ℓ=22.75②Antenna plate
Unit[mm]
NPC-F260A

Fig. 6. Model diagram of the MACKEY II type R

942

T. Moroya et al., “AMC inspired small antenna MACKEY,” IEICE Trans.
Commun., vol. J99-b, no. 9, p. 786794, Sep. 2016
K. Miyashita et al., “Mackey II model with reduced thickness,”, 2021 15th
Eur. Conference on Antennas and Propagation (EuCAP), pp. 1–4, Mar.
2021
T. Tamura et al., “Feasibility Study of MACKEY with improved
operation on metal,” IEEE APS, pp. 189–190, Jul. 2020