A Single-Layered Reflectarray Antenna
with Split Rectangular Loop Elements
Masayoshi Takao (1), Yusuke Kaimori (1), Shota Takino (1), Shigeru Makino (1),Hiromasa Nakajima (2), and Yasuhiro Nishioka (2)(1) Kanazawa Institute of Technology, 7-1 Ohgigaoka, Nonoichi-shi, Ishikawa, Japan(b1833012@planet.kanazawa-it.ac.jp)(2) Mitsubishi Electric Corporation, 5-1-1 Ofuna, Kamakura-shi, Kanagawa, Japan
Abstract— A metal plate loaded frequency selective reflector(FSR) was applied to a reflectarray antenna. Various beam shapes
can be obtained by appropriately selecting the arrangement anddimensions of the FSR resonant elements. Previous research has
shown that the attenuation of electromagnetic waves caused bydouble-layer structures results in low aperture efficiency, andalthough research has been conducted on single-layer structures,
360 [deg] phase region coverage has not been possible. This study
investigates the use of a resonant element shape with polarizationdependent beam orientation to cover a phase range of 360 [deg]with a single-layer antenna. The results show that a split-type
rectangular loop element is able to cover the target phase range.

where d is the resonant element spacing and θ is the maximum
incident angle. However, this condition (1) did not sufficiently
suppress the side lobes. Conversely, the condition for which thegrating lobes do not propagate in the dielectric:

I. INTRODUCTION

The conventional double-layer and single-layer models areshown in Fig. 1(a) and Fig. 1(b) respectively [5] [6]. In thedouble-layer model, three-line elements are placed in each layer
and the reflection phase is controlled by varying the elementlength. Using (2), we were able to satisfy element requirements,
but the lattice area was reduced to approximately 58.0% of thatin the previous study [2]. For the conventional single-layer
model, the element shape is the same as that of the double-layer
model. In addition, the single-layer elements are arranged suchthat the elements of each polarization do not overlap. The
design area of each polarization is limited by the diagonal linesof the lattice, as indicated by the dotted lines in Fig. 1(b). As aresult, the area available for each polarization element in asingle lattice is half that for a double-layer structure, and thelattice area is reduced to approximately 29.0% of that in theprevious study [2]. Consequently, as the available design area
was greatly reduced and the element length could not be
secured to the same level as before, the conventional singlelayer model could satisfy only requirement (A) for the elements.
Therefore, this paper proposes the use of split rectangular loop
elements to assemble a single-layer element shape that satisfies
both requirements.

Reflectarray antennas (hereinafter referred to as"reflectarray") have been studied as a low-cost and reliable
deployment antenna for satellites. A method has been proposed
to change the beam direction depending on polarization byappropriately selecting the array and dimensions of theresonating elements [1]. In this paper, we propose a single-layer
resonant element geometry that enables independent phase
control and covers a reflection phase area of 360 [deg], using aresonant element spacing able to inhibit propagation of grating
lobes through a dielectric.
II. ELEMENT REQUIREMENTS
Two properties are required for devices that exhibit
polarization-dependent beam orientations:(A) Independent phase control depending on polarization(B) Phase coverage range of 360 [deg] for each polarization
In addition, when designing the resonant element, it is important
to determine the element spacing d to achieve high-efficiency
and low side-lobe characteristics. In a previous study [2], adouble-layer structure model was adopted in which the layers of
the element were divided by polarization. When determining theelement spacing, the following condition was used to prevent thepropagation of grating lobes in free space [3]:d11 + sin d1 r + sin (2)where εr is the dielectric constant, is shown to sufficiently
suppress unwanted radiation, resulting in high efficiency andlow side-lobe characteristics [4]. Based on the aforementioned
discussion, in this study, the element spacing d was determinedusing (2), while the dielectric constant εr = 2.59 was used.

(1)(a) Double layer(b) Single layer

Fig. 1. Conventional model

III. ELEMENT DESIGN
The altered element shape is shown in Fig. 2, and the modelof the resonant element is shown in Fig. 3. The designparameters of the elements are listed in Table Ⅰ. To cover aphase region of 360 [deg] for both polarizations, the length ofeach element must be longer than that of the conventional
element. Therefore, the side elements were folded back andextended from the conventional element shape, as shown in Fig.
2 (steps 3 and 4).
①②③④Fig. 4. Reflection phase characteristic of H-polarization
Fig. 2. Variation of element shapeℓB1ℓB2

SBℓB4

ℓB3

ℓA4

ℓA2/2

ℓA1/2

PY

hAℓA3PX

Fig. 5. Reflection phase characteristic of V-polarization

Fig. 3. Model of resonant element

V. CONCLUSION

Table Ⅰ. Design parameters of element
BandKuLine width w

Thickness hA

0.127λInterval of line Sb

0.020λDielectric constant εr

2.59

Element length ℓA1 , ℓB10.004λ ~ 0.354λ

0.004λtanδ

0.0028Element length ℓA2 , ℓB20 ~ 0.235λAngle of incidence

25 [deg]

Element length ℓA3 , ℓB30 ~ 0.020λElement spacing PX , PY

0.394λElement length ℓA4 , ℓB40 ~ 0.107λ

IV. ANALYSIS RESULTFor each of the vertical and horizontal polarizations (V andH respectively), the total element length for the polarization
orthogonal to the main polarization (hereinafter referred to as theorthogonal polarization) was fixed at the maximum value of ℓ
=1.33λ, and the total element length for the main polarization ℓvaried between 0.004λ and 1.33λ. The reflection phasecharacteristics of the V and H polarization elements are shownin Figs. 4 and 5 respectively. These results confirm that theelements were able to cover the 360 [deg] phase range for bothpolarizations. Additionally, when the total element length of theorthogonal polarization was fixed at the maximum value, thephase change of the orthogonal polarization was less than 22[deg] in both cases.

This study demonstrated independent phase control and a360 [deg] phase region coverage for both polarizations, byarrangement of the split rectangular loop elements to eliminate
element overlap. We plan to next use these proposed elements
to build a prototype reflectarray and undertake measurements toverify the array utility.
This study was supported by JSPS (20K04491).
REFERENCES
[1]

[2]

[3]
[4]
[5]

[6]

S. Makino, H. Nakajima, and M. Takikawa, “A New Satellite Antenna
Concept Using Reflectarray Antennas,” ESA Antenna Workshop,
October, 2018.
R. Florencio, J.A.Encinar, R.R.Boix, V.Losada, and G.Toso,“Reflectarray Antennas for Dual Polarization and Broadband Telecom
Satellite Applications,” IEEE AP，VOL.63，No.4，April, 2015.
J. Huang, J.A.Encinar, “Reflectarray Antennas,” Wiley, New Jersey,
pp.83-84, 2007.
Y. Fuji, et al., “High-efficiency and Low-side-lobe Reflectarray Antenna,”
ISAP, December, 2014.
M. Fukaya, R. Obata, S. Makino, M. Takikawa, H. Nakajima,“Reflectarray antenna changing beam direction by polarization (2),”IEICE B-1-106, September, 2019．
S. Takino, S. Shigemitsu, Y. Kaimori, S. Makino, “A dual-polarized
single layer reflectarray antenna with changing beam-direction,” IEICE,
January, 2022.