2022 International Conference on Emerging Technologies for Communications (ICETC 2022)
1

Circularly polarized antennas with degenerate separation
Koki IIJIMA†a), Student member, Keito YOKOE†, Student member, Shigeru MAKINO†, Fellow Member

2. Proposal for circularly polarized MACKEY Q typeFig. 1 shows the model diagram of circularly polarized
MACKEY Q-type designed for Wi-Fi 2-GHz band. The
model consists of three layers: metal, antenna, and gridplates, with a dielectric filling the gap between the plates.
The grid and metal plates act as artificial magnetic conductor
substrates for working on the metal, and the grid and antenna
plates act as antenna substrates for radiation. In order toradiate circularly polarized waves, orthogonal polarizations
must have equal amplitude and a phase difference of 90°.
Therefore, by changing the vertical slit width ssx andhorizontal slit width ssy, the propagation constant is changed,
and as a result, a phase difference can be added to thisantenna.

1098765432
1109876543210

Axial ratio[dB]

The meta-surface-inspired antenna chip developed by theKIT EOE Laboratory (MACKEY) is a small antenna thatremains unaffected by surrounding metals [1]. The
MACKEY Q-type was developed based on the MACKEY[2]. It was miniaturized to a square with a side length of λ/4,
using two shorting plates. In this study, it is proposed anantenna that radiates circularly polarized waves with a single
point feeding by using degenerate separation.

shows the radiation patterns at 2.45 GHz for the cut planes
φ = 0° and φ = 90°. From Fig. 2, it was found that the axial
ratio characteristic could not satisfy less than 3 at 2.45 GHz
on the metal, although it operated at 2.45 GHz in free space.
Fig. 3 shows that in free space, the main polarization, LHCP
was 5.01 dBi in the frontal direction. On metal, the frontal
gain of the LHCP was 6.42 dBi, which is sufficient to radiatein the frontal direction, but the RHCP was reflected by themetal and radiated in the frontal direction.

VSWR

1. Introduction

2.3

2.4
2.5
Frequency[GHz]In free space
On metal

2.6

2.3

2.4
2.5
Frequency[GHz]In free space
On metal2.6

Fig.2 VSWR and axial ratio characteristics
YZ plane
ZXZ plane10Z00-10-10-20Zθ10X-20

LHCP in free spaceXφY

RHCP in free space

YLHCP on metal
RHCP on metal

Bird’s eye viewFig.3 Radiation pattern

4. Conclusion
In this study, the authors proposed an antenna that radiates
circularly polarized waves by varying the width of thevertical and horizontal slit lines and by varying thepropagation constant. In free space, it operated at 2.45 GHz,but on metal, the axial ratio no longer satisfied thebandwidth due to backlobe reflection.
Acknowledgments
Fig. 1 Model diagram of circularly polarized MACKEY Q-type

3. Analysis results of Unbalanced Type Inverted FThis work was supported by JST CREST Grant Number
JPMJCR20Q1, Japan.
References

Fig. 2 shows the VSWR and axial ratio characteristics infree space and on the metal. Here, the axial ratio
characteristic shows characteristic in the Z direction. Fig. 3†The author is with Kanazawa Institute of Technology …

a)[1] 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.
[2] Iijima et al., “MACKEY Q-Type Miniaturized Using Two Shorting
Plates,” in IEEE AP-S/URSI 2022, (to be presented)

E-mail: b1813979@planet.kanazawa-it.ac.jp

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