Development of MACKEY II type M miniaturizedusing multiple slits
Kota Hakamata, Keisuke Miyashita，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 operates in free spaceand on a metal plate, was investigated in this study. We propose amethod for reducing the size of MACKEY II of the 920 MHz bandto the card size.

II. PROPOSAL FOR MINIATURIZATION OF MACKEY II
In 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. Therefore, we attempted to reduce
the size of MACKEY II by cutting a slit in its grid plate to secure
the current path of λ/2 or more, even if L is shortened.

Keywords—MACKEY; RFID-920MHz; Meta-surface inspired
antenna; AMC substrateI. INTRODUCTION

Figure 3 shows the miniaturization principle. By cutting theslits along the long side of the grid plate, the current path (theblue line in Fig. 3) is extended in a meander-like pattern. This
makes it possible to electrically secure a current path of λ/2 ormore, even if the width L is reduced physically. MACKEY II
designed using this structure will be analyzed as MACKEY IItype M (multiple-slit type).

An electrically small antenna known as MACKEY basictype, which is sufficiently robust to metal objects, has beendeveloped [1]. In addition, the MACKEY II has been proposed
as a reduced-thickness model [2].

h=1.0mm
tt=1.0mm

ε=2.58tanδ=0.0014
ε=2.58tanδ=0.0014

L ≒ λ/2

s=0.5mm①Grid plate

L=2×g + s=196.2mm
w=1mm

W=50

g=97.85mm

When the number of type M slits is varied, the metal width
gm that can be matched for each number of slits is determined.
The number of slits was matched from 24 to 72 in increments of
8. The substrate width L was fixed at 80 mm, and the antenna
length ℓ was fixed at 40 mm.

NPC-F260A

Figure 4 depicts the relationship between the metal width gm
and the frequency at which the real part of the impedance of theanalysis results intersects at 50 Ω for each number of slits.

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

There are several gm values for which the real part is 50 Ωat 920 MHz, indicating that several gm values can be matched
for each number of slits. However, when the number of slits isfewer than 40, an optimal gm that minimizes the frequency
exists.

Fig. 1. Model diagram of the MACKEY II-back feed type109876543in_free_space
2on_metal
10.88 0.89 0.9 0.91 0.92 0.93 0.94 0.95 0.96 0.97 0.98

VSWR

Therefore, gm can be reduced by increasing the number ofslits because it can be matched at a lower frequency when gm isthinner.

Frequency[GHz].

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 MACKEYbasictype.
978-1-7281-4670-6/21/$31.00©2021 IEEE

L＜ λ/2

III. ANALYSIS OF MACKEY II TYPE M

Feeding point

g=97.85mm

Cut N slits in thegrid plate.

Fig. 3. Miniaturization principle

Copper

0.076mmt=2.0mmFig. 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
consisting of an antenna plate, a grid plate, and a metal plate indescending order, with a dielectric material filled in between
them. Impedance matching is performed based on the grid width
g and antenna length. Fig. 2 depicts the measurement results ofthe voltage standing-wave ratio (VSWR) characteristics in freespace and on the metal. The measurement results in Fig. 2demonstrate that the MACKEY II-back feed type operates inboth free space and the metal.

949

APS 2021

1098765432
10.88 0.89 0.9 0.91 0.92 0.93 0.94 0.95 0.96

1000

960

VSWR

Frequency[MHz]

980

940
920
900

880
860

Frequency[GHz]840

MACKEY Ⅱ

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 4.8 524 slits
56 slits

Metal width gm[mm]32 slits
64 slits

40 slits
72 slits

VSWR

ANALYSIS OF PROTOTYPE MODEL OF ANTENNA FOR
RFID TAGS

Because the stacking structure of MACKEY II type M isthe same as that of MACKEY II, the feed can be supplied at theback of the model by mounting through holes.

MACKEY Ⅱ

10 X
0-10-20

XY面
10 X
0-10-20

W=50mmhg=4mmZLℓ=39.95mm

hg=4mm

W=50mm

L=2×g + s=80mm

X

M type,32 slits_Theta
M type,48 slits_Theta

VI. ACKNOWLEDGMENTS

Z

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

③Side viewg=39.75mmg

s=0.5mm=2.7mm①Grid plateX② Y

Feeding point

w=1mm

t=2.0mmFig.5 Model diagram of 32 slits-type M①Y

MACKEY Ⅱ_Theta

In this study, to reduce the size of the conventional
MACKEY II, we applied the MACKEY II type M, which cansecure the current path in a small area by cutting slits along thelong sides of the grid plate. It was shown that the impedance
could be controlled by changing the number of slits, and the size
could be reduced. Furthermore, a prototype model of the antenna
for RFID tags was investigated, and a card-sized antenna wasproduced. Two type M models, one with 32 slits and the otherwith 48 slits, were developed, and the analysis results of VSWR
characteristics and radiation patterns were obtained. The size ofthe two proposed models was approximately 40% of that ofMACKEY II, indicating that the MACKEY II type M can besmaller than MACKEY II.

②Antenna plate ③Metal plate
Copper
NPC-F260A

h=1.0mm

XZ面10 Z0-10-20

on_metal

V. CONCLUSION③s=0.5mm=3.58mm①Grid plate

XXFig.9 Radiation patterns

Y

L=2×g + s=80mm
w=1mm

t=2.0mm

Feeding point
Side viewg=39.75mm gYZThe frontal gain of type M was lower than that of MACKEY
II, and the gain in the frontal XY-direction of the free space wasapproximately −2 dB for both models (Fig. 9). The frontal XY
gains on the metal were −0.97 dB for 32 slits and −2.32 dB for
48 slits. A possible reason was the decrease in radiation
efficiency owing to the generation of the slits.
X10 Z0-10-20YThe bandwidths of both models were narrower than that ofMACKEY II but still satisfied the 920 MHz bandwidth in freespace (Figs. 7 and 8).

①M type, 48 slits

Fig.8 VSWR characteristics on metal

Figures 7 and 8 show the analyzed values of the VSWR
characteristics for MACKEY II, 32 slits, and 48 slits. Figures 9shows the analyzed values of radiation patterns for MACKEY
II, 32 slits, and 48 slits. The radiation pattern appears at thefrequency where the VSWR has the lowest value.

②Frequency[GHz]M type, 32 slits

100-10-20
XY面 in_free_space
XZ面Figures 5 and 6 depict two design models with 32 and 48
slits, respectively, in the grid plate (red circle in Figure 4). For
both models, the gm parameters were matched with L = 80 mm
× W = 50 mm, resulting in a smaller model volume ofapproximately 40% of the MACKEY II volume.

h=1.0mm

M type, 48 slits

1098765432
10.88 0.89 0.9 0.91 0.92 0.93 0.94 0.95 0.96

48 slits

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

M type, 32 slits

Fig.7 VSWR characteristics in free space

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

Fig.6 Model diagram of 48 slits-type M

950

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 anew structure,” IEEE APS-2020, pp599-600, Jul.2020