Study of MACKEY Type H Antenna Miniaturized
Using Slits
Kota Hakamata1, Keisuke Miyashita1, Keito Yokoe1, Shigeru Makino1, Kenji Itoh1
1

Kanazawa Institute of Technology, 7-1 Ogigaoka, Nonoichishi, Ishikawa 921-8501, Japan, b745887@planet.kanazawa-it.ac.jp

Abstract—The metasurface inspired antenna chipdeveloped by the KIT EOE Laboratory (MACKEY, RFID 920MHz) is an electrically small antenna that is sufficiently robust
to metal objects. However, there have been demands forminiaturization of the available model, which has a length of200 mm at 920 MHz. Therefore, a new model called theMACKEY type H (RFID 920 MHz band) is proposed herein
and is miniaturized to the size of a card. The type H antenna
can extend the current path in a meandered manner throughslits cut along the long sides of the grid plate. This paper
presents the characteristics of the MACKEY type H antenna
and its measurement results.
Index Terms—MACKEY, RFID 920 MHz, metasurface
inspired antenna, artificial magnetic conductor substrate,robust.

I.

INTRODUCTION

Communication technologies, such as smart phones andtablets, have spread rapidly in recent years, and furtherdevelopments are expected with advancements in theInternet of Things (IoT). Hence, there is a need to endow
domestic appliances, such as televisions and air conditioners,
with communication functions for remote operation. The
antennas on such devices should be small, thin, and flexible
enough for installation regardless of the presence ofsurrounding metal components. Metasurface technology is a
key development that contributes to the miniaturization andthinning of antennas placed on metals. One such example isthe artificial magnetic conductor (AMC) substrate, whichreflects the incident electric field in the same phase using
dielectric and metal plates. There are several reported studies
on this AMC substrate [1]–[3]; in the present study, acapacitance grid [4] is used as the AMC substrate.
The metasurface inspired antenna chip developed by theKIT EOE Laboratory (MACKEY) [5] is an antenna design
based on the AMC substrate technology; it is an electricallysmall antenna that has sufficient robustness to metal objects.
There are reports that the basic design suffers from very little
degradation of the impedance and radiation characteristics
not only in free space but also on metals. In addition, theMACKEY II has been proposed as a reduced-thickness
model [6] that is designed to operate in the radio frequency
identification (RFID) 920 MHz band (below VSWR3).
However, the MACKEY II has a reported length of 200 mm;
thus, the antenna length must be reduced for placement ondevices.
This paper presents a new model called the MACKEY II
type H (henceforth referred to as “type H”) in which slits are

cut along the long sides of the lattice plate and the current
path is meandered and extended to obtain a smaller size thanthe MACKEY II antenna.
II.

CONVENTIONAL MACKEY IIFig. 1 illustrates the MACKEY II back-feed-type model
designed for the RFID 920 MHz band; as shown in the figure,the antenna plate is placed inside the AMC substrate to thin
the structure. Additionally, the MACKEY II is a three-layer
structure consisting of an antenna plate, a grid plate, and a
metal plate in descending order, with a dielectric material
filled in between them. Impedance matching is performed onthe basis of the grid length g and antenna length ℓ; thus, thethickness, length, and width of the model are 2 mm, 50 mm,and 196.2 mm, respectively. Feeding is done by two-port
measurement using the S-parameter method.
Fig. 2 shows the measured results of the VSWR
characteristics in free space and on a metal. To study thebehavior on the metal, a 366 mm × 366 mm metal plateshown in Fig. 3 is used to ensure sufficient size. The
measured results in Fig. 2 demonstrate that the MACKEY II
operates not only in free space but also on metals; thefrequency is slightly shifted between that in free space andon the metal, but the VSWR is less than 3 in both cases.
However, the model length L of the MACKEY II is 196.2mm, and the main problem here is that the board is large.
Therefore, we studied a new model for the MACKEY II in
the 920 MHz band for size reduction.
III.

PROPOSED MINIATURIZED MACKEY II ANTENNA

Fig. 4 shows the current distribution on the grid substrate.
The MACKEY radiates radio waves from the edge of thelattice plate where the current flows strongly [5]. In theconventional MACKEY, the length L of the grid plate edgeis λ/2 and depends on the designed frequency. Thus, the baselength L of the 920 MHz band MACKEY II is 190 mm,
which is large, and we reduce the this size by cutting slits
along the length of the grid plate to ensure a current path of
λ/2 or more even with a short L.
Fig. 5 shows the miniaturization principle. By cutting
slits along the long sides of the grid plate, the current path(blue line in Fig. 5) is extended in a meandered pattern. Thisensures electrically securing a current path of λ/2 or moreeven for a physically reduced L. The MACKEY II design
with this structure is designated as MACKEY II type H.

This paper's copyright is held by the author(s). It is published in these proceedings and included in any archive such as IEEE
Xplore under the license granted by the "Agreement Granting EurAAP Rights Related to Publication of Scholarly Work."

Feeding point
L=2×g + s=196.2mm
W=50

g=97.85mm

w=1mm

g=97.85mm

s=0.5mm①Grid plate

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

Copper
NPC-F260A
Fig. 1. Model diagram of the MACKEY II antenna.
10g=39.75mmg

L=2×g + s=80mm

tg

9s=0.5mm

8ℓFeeding point③Metal plate

Fig. 6. Model diagram of the MACKEY II type H antenna.

65950

43In free space

2On metal

10.88 0.89

0.9

0.91 0.92 0.93 0.94 0.95 0.96

Frequency[GHz]Fig. 2. VSWR characteristics of the MACKEY II antenna.

366mm

Resonant frequency [MHz]VSWRL②Antenna plate①Grid plate

7(1)In (1), L was fixed at 80 mm, and the dielectric length(tg) was obtained by determining the metal length (ℊm). Fig.
7 shows the relationship between gm and resonant frequency.
The type H shows a resonant frequency at 920 MHz for gm ≈5.8 and gm ≈ 13.9, and the lowest resonant frequency is at gm≈ 10.0 mm.

w=1mm

AMC substrate

W=50mmtt=1.0mm

L=2*tg+4*ℊm+s

Antennasubstrate

hg=4mmt=2.0mmε=2.58tanδ=0.0014
ε=2.58tanδ=0.0014

h=1.0mm

940
930
920
910
900
890
880
870
56789101112131415Metal width gm[mm]Fig. 7. Relationship between gm and resonant frequency at L = 80 mm.

V. ANALYTICAL AND MEASURED RESULTS FOR TYPE H
Fig. 3. Model installed on a metal plate.

Fig. 4. Current distribution on the grid substrate at 920 MHz.

L ≒ λ/2

Cut N slits in thegrid plate.

L＜ λ/2

Fig. 5. Miniaturization principle.

IV.

CONSIDERATIONS FOR MINIATURIZATION

Fig. 6 shows the model diagram of the type H antenna. In
this study, the substrate length L and height W are fixed at 80mm and 50 mm, respectively, since the expected size is thatof a card. The relationship between the base length L anddesign parameters is shown in (1).

The designed type H and conventional models arecompared herein. The type H was designed for thespecifications indicated by the black circle in Fig. 7. Fig. 8shows the designed type H model, with L × W = 80 mm × 50mm, and the model volume is reduced to about 40% of thatof the MACKEY II. Because the stacking structure of thetype H is identical to that of the MACKEY II, the feed issupplied at the back of the model via mounted holes. The
VSWR characteristics and specific bandwidth in free space
are shown in Fig. 9 and Table I, and those on metal are
shown in Fig. 10 and Table II, respectively. The black lines
represent MACKEY II and red lines represent type H. The
solid and dotted lines represent the analytical and measured
values, respectively. The type H operates in both free spaceand on metal, and the measured results for these are observed
to be shifted towards lower frequencies compared with theanalytical results. The type H characteristics are narrower
than those of the MACKEY II both in free space and onmetal. The radiation patterns and gains are shown in Fig. 11and Table III, respectively. The black and red lines represent
the MACKEY II and type H, respectively; the solid anddotted lines represent the analyzed and measured values,respectively. The radiation patterns appear at the frequency
where the VSWR is lowest; these patterns are observed to bealmost identical between the measured and analytical results.
The gain is generally consistent between the measured andanalytical results; the type H has lower gains in free spaceand on metals than the MACKEY II. The analysis value ofThis paper's copyright is held by the author(s). It is published in these proceedings and included in any archive such as IEEE
Xplore under the license granted by the "Agreement Granting EurAAP Rights Related to Publication of Scholarly Work."

①h=1.0mm

Z②Y③Feeding point
Side viewhg=4mm
=13.65mm

Actual model diagramg

Bandwidth
Analysis[%]Measure[%]Bandwidth
Analysis[%]Measure[%]

L=80mmℓ=41.1mmType H
0.432
0.450
10 X
50-5-10-15-20XFeeding pointZ

s=0.5mm①Grid plate

Type H
0.613
0.696

MACKEY II
2.58
2.59

TABLE II. RELATIVE BANDWIDTHS OF TYPE H AND MACKEY II ON
METALS.

Bird's-eye view

L=2×g + s

W=50mmg=39.75mm

TABLE I. RELATIVE BANDWIDTHS OF TYPE H AND MACKEY II IN FREESPACE.

X

w=1mm

t=2.0mmthe frequency response of the radiation efficiency is shownin Figure 12. Type H has a lower radiative efficiency than
MACKEY II. The lower gain of the type H over theMACKEY II is attributed to its lower radiative efficiency.

②Antenna plate

Copper③Metal plate

NPC-F260AY

MACKEYⅡ_analysis
MACKEYⅡ_measure 10 X
5Type H_analysis
0-5Type H_measure-10-15-20

VSWR

109876543210.88 0.89 0.9 0.91 0.92 0.93 0.94 0.95 0.96

ZX

Type H_analysis
Type H_measure

Fig. 9. VSWR characteristics of type H and MACKEY II in free space.

VSWR

109876543210.88 0.89 0.9 0.91 0.92 0.93 0.94 0.95 0.96

Frequency[GHz]Type H_analysis
Type H_measure

Fig. 10. VSWR characteristics of type H and MACKEY II on metals.

On metal

Y10 Z
50-5-10-15-20

XFig. 11. Radiation Patterns of Type H and MACKEY II.
TABLE III. . COMPARISON OF GAINSType HIn free space On metal
Analysis[dBi]-1.58-0.23
Measure[dBi]-0.63-0.48

Gain

Radiation Efficiency

Frequency[GHz]

MACKEYⅡ_analysis
MACKEYⅡ_measure

In free space
1050-5-10-15
Y -20

prepreg

Fig. 8. Type H design model.

MACKEYⅡ_analysis
MACKEYⅡ_measure

MACKEY II
1.18
1.1210.9
0.8
0.7
0.6
0.50.40.3
0.2
0.1
0.86 0.88

0.9

MACKEY II
In free space On metal
5.18
7.29
4.99
5.96

0.92 0.94 0.96 0.98

1Frequency[GHz]
MACKEYⅡ

Type H

Fig. 12. Frequency characteristics of the radiative efficiency of Type H
and MACKEY II (Analysis result)

VI.

CONCLUSION

In this work, the novel MACKEY II type H antenna is
proposed to reduce the length of the MACKEY II. In thetype H, the current path is extended and reduced by cutting
slits on the grid substrate, which is the radiating element.
From evaluation of the type H structure, the resonance points
at 920 MHz were found by fixing L = 80 mm. Based on theresults, the type H model was designed with a size smaller

This paper's copyright is held by the author(s). It is published in these proceedings and included in any archive such as IEEE
Xplore under the license granted by the "Agreement Granting EurAAP Rights Related to Publication of Scholarly Work."

than the MACKEY II, i.e., 80 mm × 50 mm. The type H isabout 40% of the size of the MACKEY II but has a narrower
bandwidth and lower gain owing to lower radiation
efficiency. The measured results in free space and on metal
are observed to be shifted towards lower frequencies
compared with the analytical results. The radiation patterns
between the measured and analytical results are observed tobe almost identical, while the gain is generally consistent.
ACKNOWLEDGMENT
This work was supported by the JST CREST, Grant Number
JPMJCR20Qa, Japan.
REFERENCES
[1]

[2]
[3]

[4]
[5]
[6]

Y. Zhang et al., “Planar articial magnetic conductors and patch antennas,” IEEE Trans. Antennas Propag., vol. 51, no. 10, pp. 2704–2712,
2003.
Y. Seki et al., “Reflection phase of frequency selective reflector withmetal sheet,” IEICE. Tech. Rep., AP2008-204, pp. 91–95, 2009.
K. Hayashi et al., “Reflection characteristics of a metal plate loaded
FSR using an equivalent circuit model and its application to the AMC
substrate,” IEICE Trans. Commun., vol. J96-B, no. 9, pp. 1010–1018,Sep. 2013.
S. Makino et al., “PMC characteristics of capacitance grid with metalplate,” in Proc. IEEE APWC, Cape Town, South Africa, 2012.
T. Moroya et al., “AMC inspired small antenna MACKEY,” IEICE
Trans. Commun., vol. J99-B, no. 9, pp. 786–794, 2016.
K. Miyashita et al., “MACKEY II with reduced thickness by using anew structure,” in Proc. IEEE APS-2020, Jul. 2020, pp. 599–600.

This paper's copyright is held by the author(s). It is published in these proceedings and included in any archive such as IEEE
Xplore under the license granted by the "Agreement Granting EurAAP Rights Related to Publication of Scholarly Work."