Millimeter-Wave Antenna using Metamaterial ELC Resonators on Electro-Optics Substrate

Abstract

We propose and present millimeter-wave antennas using metamaterial ELC resonators on electro-optic substrates for wireless millimeter-wave receivers and optical modulators. Analysis for the antenna characteristics of the device are discussed at millimeter-wave frequency of 100GHz.

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CLEO-PR 2015
Copyright @ IEEE
Abstract
We propose and present millimeter-wave antennas using
metamaterial ELC resonators on electro-optic substrates for
wireless millimeter-wave receivers and optical modulators.
Analysis for the antenna characteristics of the device are
discussed at millimeter-wave frequency of 100GHz.
I. INTRODUCTION
Recently, there is an increasing interest in researching
millimeter-wave photonics for many applications
including broadband wireless access networks,
instrumentation, and warfare systems [1]. A fundamental
aspect of millimeter-wave photonics implementation is
creation of efficient interface between them, which will
allow us to obtain higher gain in the optical domain, thus
can reduce the need for optical amplification. It is
essential that the insertion loss of the interface is kept to a
minimum, as this will impact the dynamic range of the
system as well as the overall capacity.
Many techniques have been implemented to achieve
better wireless-lightwave interface, such as by combining
the planar antennas and electro-optic modulators [2], [3].
By using this technique, wireless signals can be received
using planar antennas and then converted to lightwave
signals using electro-optic modulators. Various
configurations using combination of the planar antennas
and the electro-optic modulators can be formed.
In recent paper, electro-optic modulators using
antenna-coupled resonant electrodes have been reported
[4], giving direct conversion of 15~60 GHz signals to
lightwave signals. Higher millimeter-wave frequency
range can also be obtained utilizing coupled-split ring
resonator (C-SRR) metamaterial for wireless antennas,
with result of over 100 GHz signals to lightwave
conversion [5].
In this paper, a millimeter-wave antenna using
metamaterial ELC resonators on an electro-optic
substrate is proposed and designed for two functionalities
as wireless millimeter-wave receiver and optical
modulator in radio-over-fiber systems. The proposed
device structure is promising for high frequency
operation in millimeter-wave or terra-hertz bands. It has
compact structure and also operates with no external
power supply. Antenna characteristics of the proposed
device with several variation designs are analyzed and
discussed in detail for millimeter-wave operational
frequency of 100GHz.
II. DEVICE STRUCTURE
The basic structure of the millimeter-wave antenna
using metamaterial ELC resonator is shown in Fig. 1,
with the whole view shown in Fig. 1a, unit cell in 1.b and
cross section in 1c. The ELC resonator structure consists
of inductive loops and a capacitive gap in the center, with
design parameter including box size (B) or unit cell,
electrode length (L), electrode wide (w), capacitor plate
(p) and the gap between capacitor plate (g). These
parameters are to be varied to analyze the functionality of
millimeter-wave antenna. The antenna is fabricated on an
electro-optic crystal (LiNbO3) as a substrate with a buffer
layer of 0.2μm silicon dioxide located on the substrate.
The gold material is chosen as its electrodes with the
thickness of 2μm. Variation of design parameters is
shown in Table I.
(a)
(b) (c)
Fig. 1. Basic structure of the proposed metamaterial antenna using ELC
resonators on EO substrate (a) whole view (b) unit cell (c) cross section
TABLE I. DESIGN PARAMETERS
Parameters
Value (μm)
Parameters
Value (μm)
Box Size
(B)
210, 230, 250
Capacitor
Gap (g)
5, 10, 15
Electrode
Length (L)
180, 190, 200
Capacitor
Plate (p)
70, 90, 110
Electrode
Wide (w)
25,30, 35
Substrate
Depth (s)
150, 200, 250
Millimeter-Wave Antenna using Metamaterial
ELC Resonators on Electro-Optics Substrate
A. A.Fathnan1*, Y.N. Wijayanto1,2 , P. Daud1, D. Mahmudin1, A. Kanno2 and T. Kawanishi2
1Research Center for Electronics and Telecommunication, Indonesian Institute of Science (LIPI)
Jl. Sangkuriang Bandung 40135 West Java Indonesia
2Photonic Network Research Institute, National Institute of Information and Communications Technology
4-2-1 Nukui-Kitamachi, Koganei, Tokyo 184-8795 Japan
*ashif.aminulloh.fathnan@lipi.go.id

CLEO-PR 2015
Copyright @ IEEE
III. RESULT AND ANALYSIS
Analysis of the proposed device has been done using
3d planar electromagnetic simulation. It is understood
that when resonator size is much smaller than its
operating wavelength, ELC Resonator can be
approximated by the inductance and capacitance in the
form of an LC resonance circuit as shown in Fig. 2. The
circuit yields an electric resonance f0, where:
(1)
L in the proposed device consists of self-inductance of
each ELC Resonator and mutual inductance between
nearby ELC Resonator. C consists of capacitance of ELC
Resonator, and coupling capacitance formed between
nearby ELC Resonator. The ELC Resonator design
provides strong electric field confinement between the
capacitor gaps, which can be collected through EO
modulation using the Pockels effects of the LiNbO3
crystal.
As shown in Fig. 2, the calculated frequency
responses of S11 and S12 results in operational frequency
of the metamaterial antenna near 100GHz, with the
resonance f0 of S12 falls in 84GHz. Variation of the
design parameters change its characteristics as explained
by equation (1). Adding the value of electrode wide (w)
can increase self-inductance of the resonator, making
resonance frequency higher. Adding the value of
capacitor gaps (g) can lower its capacitance, thus making
the resonance frequency higher. Contrarily, for capacitor
plate (p) adding the value can increase its capacitance
thus decreases resonance frequency. The corresponding
graph can be seen from Fig. 3a to 3c.
For the substrate depth variation, Fig. 3d shows how
resonance frequency slightly decreases with increasing
substrate depth. It indicates that by increasing substrate
depth the coupling capacitance become slightly higher,
leading to lower resonance frequency. Ultimately, to
further improve the detection sensitivity of millimeter-
wave metamaterial antenna or to increase its operational
frequency until > 100GHz, we can refine and optimize
the antenna by setting its design parameter.
Fig. 2. S11 and S12 responses with insight of ELC Resonator equivalent
circuit and current density by 3d planar em simulation
60 80 100 120
-16
-12
-8
-4
0
S12(dB)
Freq (GHz)
w=25
w=30
w=35
(a) (b)
60 80 100 120
-16
-12
-8
-4
0
S12(dB)
Freq (GHz)
p=70
p=90
p=110
(c) (d)
Fig. 3. S12 vs Frequency result with the variation of; (a) electrode
width, (b) capacitor gap, (c) capacitor plate, (d) substrate depth
IV. CONCLUSION
We have proposed and discussed a millimeter-wave
antenna using metamaterial ELC resonators on an electro-
optic substrate. The proposed device structure can be
used for receiving wireless millimeter-wave signal (over
100GHz) by utilizing properties of metamaterial
structure. The antenna characteristics were analyzed for
100GHz millimeter-wave bands using 3d planar
electromagnetic simulation with several design variation.
It can also operate as optical modulator since electro-
optic crystal is used as its substrate.
REFERENCES
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[2] S. Shinada, T. Kawanishi, T. Sakamoto, M. Andachi, K.
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[3] Bridges, F. Sheehy and J. Schaffner, "Wave-Coupled
LiNbO3 Modulator for Microwave and Millimeter-Wave
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[4] Y. N. Wijayanto, H. Murata, and Y. Okamura, "Electro-
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[5] N. Suenari, H. Murata, Y. Okamura “100 GHz-Band
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2014, pp. 75-78
50 60 70 80 90 100 110 120
-25
-20
-15
-10
-5
0
S Parameters (dB)
Frequency (GHz)
S11
S12
60 80 100 120
-16
-12
-8
-4
0
S12(dB)
Freq (GHz)
g=5
g=10
g=15
60 80 100 120
-16
-12
-8
-4
0
S12(dB)
Freq (GHz)
s=150
s=200
s=250