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

Circular Polarization of MACKEY Q-Type
Koki Iijima
Electrical and Electronic Engineering
Kanazawa Institute of Technology
Nonoichi, Ishikawa, Japanb1813979@planet.kanazawa-it.ac.jp

Keito Yokoe
Electrical and Electronic Engineering
Kanazawa Institute of Technology
Nonoichi, Ishikawa, Japanb1995149@planet.kanazawa-it.ac.jp

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

Hajime Suzuki
Electrical and Electronic Engineering
Kanazawa Institute of Technology
Nonoichi, Ishikawa, Japanb1845590@planet.kanazawa-it.ac.jp

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

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

Abstract—The
metasurface-inspired
antennachipdeveloped by KIT EOE Laboratory (MACKEY) is a small
antenna that is not affected by metals. The MACKEY Q-type
was developed based on MACKEY. It was miniaturized to asquare of side λ/4. This study proposes an antenna that canradiate circularly polarization by cutting into the grid plate.

5VSWR

43
2Keywords—MACKEY, metasurface-inspired antenna, twopolarizations, λ/4 squared

12.3I. INTRODUCTION

3The metasurface-inspired antenna chip developed by theKIT EOE Laboratory (MACKEY) is a small antenna thatremains unaffected by surrounding metals [1]. The MACKEY
II unbalanced type, which is a thinner version of MACKEY
and uses an inverted L-shaped antenna as a feeding element
for unbalanced power supply, was also developed [2]. TheMACKEY Q-type was developed based on the MACKEY II
unbalanced type [3]. It was miniaturized to a square with aside length of λ/4, using two shorting plates.

2.4
2.5
Frequency [GHz]In free space
On metal

2.6

Fig. 2. VSWR characteristics of MACKEY Q-type

II. PROPOSAL OF CIRCULARLY POLARIZED MACKEY QTYPE

A. Principle of MACKEY Q-type
The principle of the MACKEY Q-type system is
discussed in this sub-section. Power is supplied from thesecond layer of the antenna plate and the supplied power istransmitted between the shorting and grid plates. Radio waves
are radiated at the left and bottom edges of the grid plate.
Because the radio waves radiating from each side areorthogonal with equal amplitudes and phases, the combined
wave radiates a linearly polarized wave with φ = 135°, and thegain is 3 dB greater than that at φ = 90°, where φ is the angleof rotation along the x-axis.

Fig. 1 shows the model diagram of the MACKEY Q-type
designed for Wi-Fi 2-GHz band. The model consists of threelayers: metal, antenna, and grid plates, with a dielectric filling
the gap between the plates. The grid and metal plates act as
artificial magnetic conductor substrates for working on themetal, and the grid and antenna plates act as antenna
substrates for radiation. Fig. 2 shows the voltage standing
wave ratio (VSWR) characteristics of this model. This model
works in both free space and in metal.

#1#2

Phase[deg]Amplitude

B. Circularly polarization design method
Fig. 3 shows the amplitude and phase frequency responsesof the circularly polarized MACKEY Q-type. Orthogonalmodes #1 and #2 are generated on the grid plate. To radiate
circularly polarized waves, the relative phases of the twomodes should be 90°. By making a cut at the bottom edge ofthe grid plate, the resonant frequency of mode #1 becomes
lower than that of mode #2. Therefore, by varying the depthof the cut d, the relative phases of modes #1 and #2 aredesigned as 90°.

f1 f0 f2
Frequency [Hz]Fig. 1. Model diagram of MACKEY Q-type

#190°

#2#2
df1 f0 f2
Frequency [Hz]Fig. 3. Amplitude and phase frequency response
JST CREST, Japan (Grant Number: JPMJCR20Q1)

471

#1

III. ANALYSIS RESULTS

Axial Ratio

The results of the analysis of the circularly polarized
MACKEY Q-type are discussed in this section. The analysis
was performed using an electromagnetic field simulator(ANSYS HFSS) based on the finite element method. The
diagram of the model used for the analysis is shown in Fig. 4.
Matching was performed by varying the grid plate height W,grid plate width g, and antenna length ℓ. Fig. 5 shows theVSWR characteristics in free space and on the metal. Fig. 6shows the amplitude and phase of the far field in the Z-axis
direction in free space and on the metal. Fig. 7 shows the axial
ratio characteristics in the Z-axis direction in free space andon the metal. Fig. 8 shows the radiation patterns at 2.45 GHz
for the cut planes φ = 0° and φ = 90°.

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2.3

2.4
2.5
Frequency [GHz]In free spaceOn metal

2.6Fig. 7. Axial ratio characteristics of circularly polarized MACKEY Q-typeZθ

φ = 90°φ = 0°

X2.45 GHz
θ = 0°

Yθ = 0°101000-10-20φ

Bird’s eye view-1090°-2090°LHCP in free space
RHCP in free space
LHCP on metal
RHCP on metal

Fig. 8. Radiation pattern of circularly polarized MACKEY Q-type

Fig. 5 shows that, although the circularly polarized
MACKEY Q-type has a narrow bandwidth, it operates at 2.45
GHz both in free space and on the metal. Fig. 6 shows that theresonance frequency is shifted at two polarizations, with a 90°
phase shift in free space at 2.45 GHz. Fig. 7 shows that theaxial ratio is less than 3 dB at 2.45 GHz in free space, but thebandwidth could not be satisfied owing to a slight frequency
shift on the metal. Fig. 8 shows that in free space, the mainpolarization, LHCP was 4.60 dBi in the frontal direction,
whereas RHCP, the circularly cross-polarized wave, hardlyradiated in the frontal direction. On metal, the frontal gain ofthe LHCP was 6.31 dBi, which is sufficient to radiate in thefrontal direction, but the RHCP was reflected by the metal andradiated in the frontal direction. This results in a larger axial
ratio of the metal.

Fig. 4. Model diagram of circularly polarized MACKEY Q-type

1098VSWR

7654IV. CONCLUSION

32In this study, the principle of operation of the MACKEYQ-type was explained, and a method for cutting a slit in thegrid plate to radiate circularly polarized waves was proposed.
The depth of cut “d” is an important parameter in designingcircularly polarized waves, determining the relative phases ofmodes #1 and #2. As the proposed antenna radiates circularlypolarized waves with a single-point feed, it was confirmedthat the antenna radiates circularly polarized waves at 2.45
GHz in free space, despite the narrow bandwidth. However,on the metal, the back lobe was reflected in the frontal
direction, resulting in a larger axial ratio. In the future studies,
we plan to consider the structures that are less susceptible tometal effects and bandwidth expansions.

12.3

2.4
2.5
Frequency [GHz]In free space
On metal

2.6

Fig. 5. VSWR characteristics of circularly polarized MACKEY Q

3012090

Amplitude[dB]2560

Phase[deg]

2015
1030
0-30 2.3

2.42.5

2.6-60

5-90
2.3

2.4
2.5
2.6
Frequency [GHz]rEPhi in free spacerETheta in free spacerEPhi on metalrETheta on metal-120

Frequency [GHz]rEPhi in free spacerETheta in free spacerEPhi on metalrETheta on metal

REFERENCES[1]

Fig. 6. Amplitude and phase of far field electric field

[2]

[3]

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S. Makino, T. Moroya, M. Kotaka, K. Itoh, K. Noguchi, and T. Hirota,“A proposal of AMC inspired small antenna MACKEY,” 2015 IEEEAPS Topical Conference on Antennas and Propagation in WirelessCommunications (APWC), Sep. 2015.
K. Miyashita, S. Makino, and K. Itoh, “Feasibility study of an
unbalanced MACKEY type R with enhanced robustness on metal,”
2021 International Symposium on Antennas and Propagation (ISAP),Oct. 2021.
Iijima et al., “MACKEY Q-Type Miniaturized Using Two Shorting
Plates,” in IEEE AP-S/URSI 2022, (to be presented)