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

Development of Scanning Spot Beam
Reflectarray Antenna
Yusuke Kaimori
Kanazawa Institute of Technology
7-1 Ogigaoka, Nonoichishi,
Ishikawa 921-8501, Japanb1714005@planet.kanazawa-it.ac.jp

Shigeru Makino
Kanazawa Institute of Technology
7-1 Ogigaoka, Nonoichishi,
Ishikawa 921-8501, Japanmakino@neptune.kanazawa-it.ac.jp

Shinichi Yamamoto
Mitsubishi Electric Corporation
5-1-1 Ofuna, Kamakura
Kanagawa 247-0056, Japan
Yamamoto.Shinichi@dr.MitsubishiEle
ctric.co.jp

Yasuhiro Nishioka
Mitsubishi Electric Corporation
5-1-1 Ofuna, KamakuraKanagawa 247-0056, Japan
Nishioka.Yasuhiro@bx.MitsubishiElect
ric.co.jp

Masayoshi Takao
Kanazawa Institute of Technology
7-1 Ogigaoka, Nonoichishi,
Ishikawa 921-8501, Japanb1833012@planet.kanazawa-it.ac.jp

TABLE I. ELEMENT DESIGN PARAMETERS

Abstract—
Conventional
multispot
beams
andmultiscanning beams have been developed using a single
reflector by combining the characteristics of reflectarray
antennas, which change the beam direction, depending on thefrequency and polarization. In this study, we developed a design
method and obtained measurement results of a scanning spotbeam reflectarray antenna whose beam direction is changed by
the frequency in the elevation direction and polarization in theazimuth direction.
Keywords— reflectarray antenna, scanning spot beam,polarization, frequency

Element spacing PX = PY

0.38λ0Element length lA, lB

0.01–0.87λ0, 0.01–1.01λ0

Line width w

0.02λ0Line spacing SB

0.05λ0Thickness hA, hB

0.15λ0, 0.02λ0

Dielectric constant εr2.56, 2.59

tan δ0.0015, 0.0017

I. INTRODUCTION
In a multi-beam communication system with reflectarrayantennas, covering a service area using a few mirror planes
can be achieved by changing the beam direction based on thepolarization and frequency [1][2][3]. In this paper, we present
the measurement results of a reflectarray fabricated using thedesign method described in a previous report [4].
II. ELEMENT DESIGN
A. Design modelFig. 1 shows the linear element employed to change thephase according to the reflectarray polarization [5][6]. Table Ⅰ
lists the element parameters. The lengths of the three linear
elements were extended to achieve gradual phase control asfollows: lA1 and lB1 to 0.36λ0, lA2 to 0.25λ0, and lB2 to 0.32λ0.
Let the total element lengths be lA and lB, respectively, and let
lA = lA1 + 2lA2 and lB = lB1 + 2lB2.

B. Design results
The H-polarization element length was fixed at lB = 1.01λ0,
and that for the V-polarization, lA, ranged from 0.01λ0 to0.87λ0. Similarly, the V-polarization element length was fixed
at lA = 0.87λ0, and that for the H-polarization, lB, was varied
from 0.01λ0 to 1.01λ0. Figs. 2 and 3 show the respective
analysis results. Both polarizations covered a phase region of360° or larger. When the element length of the H-polarization
was changed, the V-polarization phase changed by amaximum of approximately 0.53°. When the element lengthof the V-polarization was changed, the H-polarization phasechanged by a maximum of approximately 2.04°. Therefore, it
can be inferred that the interference between the elements wasslight, and independent phase control was possible for eachpolarization.

Fig. 2. Reflection phase characteristics of V-polarization

Fig. 1. Element design385

V. MEASUREMENT RESULTS
A contour map at 35 dBi is shown in Fig. 6. Measurements
were taken in the near filed and results are shown in terms ofdirectivity gain. The desired area was efficiently covered bya single reflectarray, as indicated by the measurement results.
However, the directivity gain at a high frequency (fH) of the
H-polarization was low. The beam directions at frequencies fH
and fL were radiated ±1 beam width away from the beam at thecenter frequency when observed in the elevation plane. The
V-polarized beam was emitted in the −0.67° direction, and theH-polarized beam was emitted in the +0.76° direction whenobserved in the azimuth plane (f0). The V-polarized beam wasgenerally consistent with the analytical results; however, theH-polarized beam changed by +0.11° compared with theanalytical results.

Fig. 3. Reflection phase characteristics of H-polarization

III. REFLECTOR DESIGN
The mirror surface was fabricated using the design values
obtained in a previous study [4]. Fig. 4 shows the computeraided design (CAD) of the mirror surface of the reflectarraywith the respective elements. The aperture diameter is 41.2λ0.
Two CAD drawings are depicted in Fig. 4; however, because
they are superposed on two layers, they appear as a single
mirror surface. The image on the left is the mirror surface ofthe V-polarization, printed at the back of dielectric layer B.
The image on the right is a mirror surface of the Hpolarization, printed on the surface of dielectric layer B.

Fig. 6. 35dBi contour map

VI.

Fig. 4. CAD data of reflectarray

IV. ANALYSIS RESULTS
A contour map at 35 dBi is shown in Fig. 5. The analysis
was performed using the aperture distribution method. In
addition, ideal elements were used. The results confirmed thatthe desired area was efficiently covered.

CONCLUSION

The results of a study on reflectarrays with different beam
directions based on the polarization and frequency arepresented. The measurement results show that the beamchanges with frequency in the elevation direction and withpolarization in the azimuthal direction. Thus, it is feasible tocover the desired area efficiently using a single reflectarray.
However, the gain decreased at high frequencies in the Hpolarization. We believe that this may be due to the fact thatthe elements affecting the H and V polarization are separated
by layer in the elements. In future studies, we will consider
elements that do not induce gain reduction.
This study was supported by JSPS (20K04491).
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Fig. 5. 35dBi contour map

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