Development of MACKEY II type M miniaturizedusing multiple slits
Kota Hakamata, Keisuke Miyashita，Yokoe Keito, Shigeru Makino，Kenji ItohKanazawa Institute of Technology
7-1 Ogigaoka, Nonoichishi
Ishikawa, 921-8501 Japanb1745887@planet.kanazawa-it.ac.jp
Abstract— A meta-surface-inspired antenna chip developed by
KIT EOE Laboratory (MACKEY), which can operate in freespace and on a metal plate, was investigated in this study. We
propose a method to reduce the size of MACKEY II for the 920
MHz band to that of a card.
Keywords—MACKEY; RFID-920MHz; Meta-surface inspiredantenna; AMC substrate

I. INTRODUCTION
An electrically small antenna, known as MACKEY basictype, sufficiently robust to interact with metal objects, wasdeveloped in [1]. Subsequently, MACKEY II was proposed as amodel with small thickness in [2].
Fig. 1 depicts the MACKEY II back-feed-type model(MACKEY II) designed for the radio-frequency identification(RFID) 920 MHz band. The model is a three-layer structure
comprising an antenna plate, a grid plate, and a metal plate indescending order, with a dielectric material in between theseplates. Impedance matching was realized based on the grid
width g and antenna length. Fig. 2 shows the measured voltage
standing wave ratio (VSWR) characteristics in free space and on
the metal. The results in Fig. 2 demonstrate that the MACKEY
II operates in both free space and the metal.

VSWR

10987
6543
in_free_space2
on_metal
10.88 0.89 0.9 0.91 0.92 0.93 0.94 0.95 0.96 0.97 0.98

h=1.0mm
tt=1.0mm

ε=2.58tanδ=0.0014
ε=2.58tanδ=0.0014

0.076mmt=2.0mm

Frequency[GHz]Fig. 1. Model diagram of the MACKEY II-back feed type
Copper
NPC-F260A

Feeding points=0.5mm①Grid plate

w=1mm

L=2×g + s=196.2mm

g=97.85mm
W=50

g=97.85mm

L=2×g + s=196.2mmℓ=69mmFeeding point②Antenna plate③Metal plate

Fig. 2. VSWR characteristics of the MACKEY basic typeIn this study, MACKEY II is proposed, which is fed inside the AMC
substrate. It has been shown that MACKEY II is thinner than the MACKEY
basic type.

II. PROPOSAL FOR MINIATURIZATION OF MACKEY IIIn the conventional MACKEY II, the width L is λ/2,depending on the design frequency. Therefore, the base width Lof the 920 MHz band MACKEY II is 190 mm, a problem
associated with its large size. Thus, we attempted to reduce thesize of MACKEY II by cutting a slit in its grid plate to secure aminimum current path of λ/2, even if L decreases.
Fig. 3 illustrates the principle of miniaturization. By cutting
slits along the long side of the grid plate, the current path (blueline in Fig. 3) is extended to a meander-like pattern, thus
electrically securing a minimum current path of λ/2, even if L is
physically reduced. MACKEY II designed using this structure
will be analyzed as MACKEY II type M (multiple-slit type).
Fig. 3. Miniaturization principle

L ≒ λ/2

Cut N slits in thegrid plate.

L＜ λ/2

III. ANALYSIS OF MACKEY II TYPE M
When the number of type M slits is varied, the metal width
gm that can be matched for different numbers of slits isdetermined. The number of slits was matched from 24 to 72 inincrements of 8. The substrate width L was fixed at 80 mm, andthe antenna length ℓ at 40 mm.
Fig. 4 depicts the relationship between the metal width gm
and the frequency at which the real part of the impedance of theanalysis results reaches 50 Ω for each number of slits. Several
gm values exist for which the real part is 50 Ω at 920 MHz,
indicating that several gm values can be matched for different
numbers of slits. However, if the number of slits is fewer than40, an optimal gm that minimizes the frequency exists.
Therefore, gm can be reduced by increasing the number of slits,
because the thinner the gm, the lower are frequencies at which
it can be matched.

1098765432
10.89

1000

960
940
920
900
880
860
1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6 3.8 4 4.2 4.4 4.6 4.8 5

Metal width gm[mm]24 slits
56 slits

32 slits
64 slits

40 slits
72 slits

Figs. 5 and 6 depict two analytical models with 32 and 48
slits, respectively, in the grid plate (red circles in Fig 4). In theanalysis, the antennas were fed directly to each other. However,in the measurements, the antennas were back-fed using throughholes. For both models, the gm parameters were matched with L= 80 mm × W = 50 mm, resulting in a smaller model volume,i.e., approximately 40% the volume of MACKEY II.

XY面
10 X
0-10-20Figs. 7 and 8 shows the analyzed and measured values of theVSWR characteristics and the radiation patterns, respectively,
for 32 slits (a) and 48 slits (b). The radiation pattern appeared at
the frequency where the VSWR exhibited the lowest value.
Both in free space and on metal, the measured results arelower than the analyzed results, and the specific bandwidth wasslightly wider, as shown in Fig. 7. The reason for the discrepancy
between the measurement and analysis results may be that theprepreg and through-hole were not considered in the analysis.

t=2.0mm①h=1.0mm②Feeding point
Side viewg=39.75mm g

ZY③
L=2×g + s=80mm
w=1mm

W=50mmhg=4mmX

s=0.5mm=3.58mm①Grid plate

Lℓ=39.95mm②Antenna plate ③Metal plate
Copper
NPC-F260AFeeding point

L=2×g + s=80mm

W=50mmhg=4mm

0.91

0.92

0.93

Frequency[GHz]Analysis_free
Analysis_metal
Measure_free
Measure_metal

XZ面
0.90GHz 10 Z
0-10Y-20

X

XY面
10 X
0-10-20

XZ面
0.91GHz 10 Z
0-10Y-20

X

X

XY面
10 X
0-10-20

XZ面
0.90GHz 10 Z
0-10-20
YX

V. CONCLUSION
In this study, to reduce the size of the conventional
MACKEY II, we introduce the MACKEY II type M, which cansecure the current path in a small area owing to the slits present
along the long sides of the grid plate. The impedance can becontrolled by changing the number of slits, and the size can bereduced. Furthermore, a prototype antenna model for RFID tags
was investigated, and a card-sized antenna was produced. Twotype M models, one with 32 slits and one with 48 slits, weredeveloped, and the analysis results of the VSWR characteristics
and radiation patterns were obtained. The size of the two
proposed models was approximately 40% that of MACKEY II,indicating that MACKEY II type M can be smaller than
MACKEY II.
VI. ACKNOWLEDGMENTS③Side viewg=39.75mmg

s=0.5mm=2.7mm①Grid plate

0.9This work was supported by JST CREST Grant Number
JPMJCR20Q1, Japan.

Z

② Y

w=1mm

t=2.0mmh=1.0mmX

0.93(a)32 slits(b)48 slits
Fig.8 Radiation patterns

Fig.6 Model diagram of 32 slits-type M
①0.92

XZ面
XY面
0.91GHz 10 Z
10 X
00-10-10-20-20
Y

ANALYSIS OF PROTOTYPE MODEL OF ANTENNA FOR
RFID TAGSThe radiation patterns of the measurement and analysis
results were generally consistent. However, Fig. 8 shows that thegain in the frontal direction of the measurement results waslower than that of the analysis results.

0.91(a)32 slits(b)48 slits
Fig.7 VSWR characteristics

48 slits

Fig.4 Relationship between metal width gm and resonant
frequency for each model
IV.

0.9

Frequency[GHz]Analysis_free
Analysis_metal
Measure_free
Measure_metal

840

10987
6
54
32
10.89

VSWR

VSWR

Frequency[MHz]980

L

REFERENCES[1]ℓ=41.1mm[2]②Antenna plate③Metal plate
Copper
NPC-F260A

Fig.7 Model diagram of 48 slits-type M

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 a
new structure,” IEEE APS-2020, pp599-600, Jul.2020