A single-feeding port HF-UHF dual-band RFID tag antenna

Abstract

In this paper, a dual-band high frequency (HF) and ultra-high frequency (UHF) radio-frequency identification (RFID) tag antenna is presented that operates in the 13.56 MHz band as well as in the 920 MHz band. A spiral coil along the edges of the antenna substrate is designed to handle the HF band, and a novel meander open complementary split ring resonator (MOCSRR) dipole antenna is utilized to generate the UHF band. The dual-band antenna is supported by a single-feeding port for mono-chip RFID applications. The antenna is fabricated using an FR4 substrate to verify theoretical and simulation designs, and it has compact dimensions of 80 mm × 40 mm × 0.8 mm. The proposed antenna also has an omnidirectional characteristic with a gain of approximately 1 dBi.

Full text

JOURNAL OF ELECTROMAGNETIC ENGINEERING AND SCIENCE, VOL. 17, NO. 4, 233~237, OCT. 2017
https://doi.org/10.26866/jees.2017.17.4.233
ISSN 2234-8395 (Online) ∙ ISSN 2234-8409 (Print)
233
I. INTRODUCTION
Radio-frequency identification (RFID) is an emerging tech-
nology and is one of the most rapidly growing segments of to-
day’s automatic identification and data collection industry [1].
High frequency (HF) and ultra-high frequency (UHF) bands
have many advantages over other bands that are frequently used
in RFID. In terms of operating frequency bands, HF bands are
widely applied in short-distance reading applications because
they provide improved security and greater information storage
capability because of their near-field operation. UHF bands
offer better speed and are often applied in long-distance reading
applications [2]. In some special cases, such as logistics, invent-
tory management and bioengineering, both short- and long-
distance reading are needed. Therefore, a single RFID antenna
with a dual operating frequency band is required. Combining
both RFID standards on the same tag would increase this an-
tenna’s capabilities and could lead to new applications. However,
the use of two chips for two bands would increase the cost of
the tag. In this paper, a single-feeding port for an application
specific integrated circuit (ASIC) mono-chip is used for the
dual-band RFID tag antenna.
Prior research on HF-UHF dual-band antennas has already
been published [3–6]. Typically, the spiral coil is used for the
HF antenna to operate at 13.56 MHz. UHF bands vary widely
because of the frequency allocations of different countries. In
Korea, based on the Korea Communications Commission,
UHF bands from 917 MHz to 923.5 MHz are used [7]. A me-
ander-line dipole is often used to generate the UHF antenna
placed inside or outside of the HF coil. However, the current on
the vertical conductor of each dipole arm is in the opposite di-
rection to the current on each adjacent vertical conductor. This
results in a far field that is canceled by these elements. Thus, the
radiation from the meander-line dipole is mainly due to the
A Single-Feeding Port HF-UHF Dual-Band
RFID Tag Antenna
Nam Ha-Van · Chulhun Seo*
A
bstract
In this paper, a dual-band high frequency (HF) and ultra-high frequency (UHF) radio-frequency identification (RFID) tag antenna is
presented that operates in the 13.56 MHz band as well as in the 920 MHz band. A spiral coil along the edges of the antenna substrate is
designed to handle the HF band, and a novel meander open complementary split ring resonator (MOCSRR) dipole antenna is utilized to
generate the UHF band. The dual-band antenna is supported by a single-feeding port for mono-chip RFID applications. The antenna is
fabricated using an FR4 substrate to verify theoretical and simulation designs, and it has compact dimensions of 80 mm × 40 mm × 0.8
mm. The proposed antenna also has an omnidirectional characteristic with a gain of approximately 1 dBi.
Key Words: Compact Antenna, Dual-Band Radio Frequency Identification (RFID) Tag Antenna, Meander Open Complementary Split
Ring Resonator (MOCSRR) Structure, Omnidirectional Characteristic, Single-Port RFID Antenna.
Manuscript received May 12, 2017 ; Revised October 10, 2017 ; Accepted October 16, 2017. (ID No. 20170512-023J)
Department of Information Communication, Materials, and Chemistry Convergence Technology, Soongsil University, Seoul, Korea.
*Corresponding Author: Chulhun Seo (e-mail: chulhun@ssu.ac.kr)
This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits
unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
ⓒ Copyright The Korean Institute of Electromagnetic Engineering and Science. All Rights Reserved.

JOURNAL OF ELECTROMAGNETIC ENGINEERING AND SCIENCE, VOL. 17, NO. 4, OCT. 2017
234
small horizontal segments connecting each vertical segment [8].
In [8], a meander open complementary split ring resonator
(MOCSRR) particle was presented to overcome the restrictions
of the conventional meander-line dipole. In this paper, a novel
MOCSRR structure is presented to handle UHF bands.
This paper is organized as follows. The antenna’s structure
and dimensions are introduced in Section II. In Section III, the
design methodology and results are given from the analysis of
HF and UHF parts, respectively. The fabrication and mea-
surement results of the dual-band antenna are presented in Sec-
tion IV.
II. ANTENNA STRUCTURE AND DIMENSIONS
The proposed antenna structure is shown in Fig. 1. The HF
and UHF antennas are placed on two sides of the FR4 (ε = 4.4,
tanδ = 0.02) substrate with 1.2 mm thickness and the following
dimensions: 
 = 45 mm, and  = 82 mm. The proposed
antenna has a single-feeding port for mono-chip HF-UHF
bands that are connected by via with radius of  = 0.2 mm.
The dimensions of the feeding port are as follows: 
 = 1.8
mm,  = 5.4 mm, and  = 2 mm. The HF antenna is a
three-turn spiral coil with 
 = 42.2 mm,  = 77.2 mm, 
= 1 mm,  = 0.3 mm,  = 17.5 mm, and  = 4.9 mm.
The MOCSRR dipole UHF antenna structure parameters are

= = 28.2 mm,  = 0.7 mm,  = 0.3 mm,  = 2.8
mm, and A=B = 4.9 mm. It should be noted that the UHF
antenna has a diagonal symmetric structure. Two rectangular
slots in the two arms are used to fine-tune the impedance. The
dual-band RFID antenna was designed to match the ASIC
chip impedance, which has a standard impedance of 50 Ω. The
chip was self-designed to match the standard impedance at the
operating dual-band frequency. The design was simulated and
optimized in ANSYS HFSS software (ANSYS Inc., Ca-
Fig. 1. Proposed antenna structure with its dimensions.
nonsburg, PA, USA). A two-solution frequency at HF and
UHF bands was applied in the simulation software to obtain the
wide-band results from HF to UHF frequencies.
III. ANTENNA DESIGN AND ANALYSIS
The basic process of designing a dual-frequency antenna is to
create an HF and a UHF antenna separately and then join these
two antennas together with a single feeding-port. However,
since these two antennas are joined together in parallel, the
UHF antenna will affect the HF antenna’s operation and vice
versa. In the proposed antenna, the HF and UHF antennas are
placed on either side of the substrate to minimize the mutual
interaction and decoupling issues between the HF and UHF
antennas.
1. HF Antenna Design
For the design of the HF band antenna, a printed three-turn
spiral coil is used. It is important that the HF antenna coil is
placed at the outermost region of the available space in order to
collect more magnetic flux. For a combined HF and UHF chip
with a single port, a series capacitor that is tuned to the desired
resonant frequency presents a short circuit at the chip input for
UHF and thus inhibits operation [9]. In this paper, a set of
RLC components is used to tune the resonant frequency of
13.56 MHz and reduce the resistive losses in the antenna coil as
shown in Fig. 1.
2. UHF Antenna Design
Various antenna types are used for UHF band operating fre-
quencies, such as patch, slot, and meander-line antennas. The
planar meander-line antenna is the most useful because of its
advantages of size reduction and simple configuration. However,
the radiation from the meander-line dipole is restricted because
of the opposite direction of the current in each adjacent vertical
conductor. The MOCSRR particle was presented to improve
upon the conventional meander-line dipole in [8]. In this paper,
a novel and modified MOCSRR structure is used to generate a
UHF operating frequency fed with a 50-Ω microstrip feeding
line, as shown in Fig. 1.
3. Dual-Band HF-UHF Antenna Design
After completing the designs of the HF and UHF band an-
tennas separately, the combined HF and UHF band antenna is
implemented to become a single antenna with a single-feeding
port. However, the HF and UHF band antennas affect each
other, which is conducive to change of the antenna characteris-
tics. Therefore, the dual-band antenna is tuned and modified to
obtain the desired operation of both frequency bands.
The simulation results of the return loss S11 parameters for

Ha-Van and SEO: A SINGLE-FEEDING PORT HF-UHF DUAL-BAND RFID TAG ANTENNA
235
the dual-band antenna are shown in Fig. 2. The resonant fre-
quency of the HF band antenna is 13.52 MHz with a low re-
turn loss of -39.92 dB, whereas the resonant frequency of the
UHF band antenna is 921.2 MHz with a -43.19 dB return
loss. It is obvious that the dual-band antenna is a good match
for the feeding port impedance. The details of each band fre-
quency are plotted by two inset figures for the HF and UHF
bands, respectively. The -10 dB bandwidth of the UHF band
covers 914.3 MHz to 929.5 MHz, which includes the expected
frequency range. The simulated radiation pattern and the an-
tenna gain of the dual-band antenna at 921 MHz are illustrated
in Fig. 3. The gain of the proposed antenna is around 2 dBi. It
presents an omnidirectional characteristic of the antenna at the
φ = 90° plane.
IV. DUAL-BAND ANTENNA FABRICATION AND
MEASUREMENT RESULTS
From the analysis and design of the above sections, the pro-
Fig. 2. Simulated return loss S11 of the dual-band antenna.
(a) (b)
Fig. 3. Simulated radiation pattern in (a) a 2D view and (b) a 3D
view and the antenna gain at 921 MHz.
(a) (b) (c)
Fig. 4. Photograph of the manufactured antenna. (a) Top view, (b)
bottom view, and (c) measurement configuration of the
proposed antenna.
posed antenna was fabricated and measured to verify its perfor-
mance, as shown in Fig. 4. The dual-band antenna is printed on
a 1.2-mm thick FR4 substrate, and the overall size is 82 mm ×
45 mm. A coaxial cable is connected to the single-port dual-
band antenna. For a dipole antenna to operate properly, the
currents on both arms of the dipole should be equal in magni-
tude. Ideally, the current along the dipole arm that is connected
to the outer conductor of the coaxial cable should be equal to
the current on the other dipole arm [10]. However, some of the
current may travel down the outside of the outer coaxial cable,
leading to an unequal current magnitude between the two arms
of the dipole. In addition, because of several factors including
the fabrication tolerance, losses that occur during the measure-
ment process and upon exposure to the environment, and the
mismatch between the feeding line and the antenna in actual
fabrication, the dual-band frequencies shift and differ from the
simulation results. As a consequence, optimization is required to
ensure that the measurement results obtain the expected dual-
band frequency bands.
The coaxial cable of the dual-band antenna was connected to
a Protek A333 Network Analyzer to measure the return loss.
Fig. 5. Measured return loss S11 results of the dual-band antenna.

JOURNAL OF ELECTROMAGNETIC ENGINEERING AND SCIENCE, VOL. 17, NO. 4, OCT. 2017
236
The measured S11 parameters of the dual-band antenna are
shown in Fig. 5. The resonant frequencies in the measurement
results are slightly different from the ones in the simulation re-
sults, with an HF frequency of 13.62 MHz and a UHF fre-
quency of 922.5 MHz, respectively. Although the return losses
are also higher, they are acceptable for values lower than -10 dB.
The -10 dB bandwidth for the UHF band frequency covers
883 MHz to 938.2 MHz, which is larger than the bandwidth in
the simulation. Fig. 6 presents the measured radiation pattern
and gain of the dual-band antenna at 922 MHz. There is good
agreement between the simulation and measurement results of
the radiation pattern. In the Phi = 90o plane, the dual-band an-
tenna also presents an omnidirectional characteristic that is
clearly illustrated in the 3D view of the measured radiation pa-
ttern, as shown in Fig. 6(c). A comparison of antenna gain be-
tween the simulation and measurement results in a UHF fre-
quency range from 917 MHz to 923.5 MHz is shown in Fig.
6(d). This UHF frequency range is the one used in Korea based
on the Korea Communications Commission. The gain in
measurement is slightly lower than the gain in simulation be-
cause of the losses during the measurement process. A compari-
son of important factors, such as overall size, the number of
ports, the substrates used, and the number of turns, between the
proposed antenna and those of related works is presented in
Table 1. From this Table 1, it can be seen that the proposed
antenna size is significantly compact compared with the other
RFID antennas referenced. An FR4 substrate was used, which
can reduce the cost of antenna fabrication.
Fig. 6. Measured radiation pattern in a 2D view: (a) Phi = 0o and (b)
Phi = 90o. (c) A 3D view of the measured radiation pattern
at 922 MHz. (d) simulation and measurement results in a
UHF frequency range from 917 MHz to 923.5 MHz.
Table 1. A comparison of the proposed RFID antenna with those
of related works
Ref. Substrate
Overall size
(mm)
Number
of ports
[2] h = 0.7 mm, εr = 2.2 83 × 49
T
wo ports
[3] Roger 4003C, εr = 3.38 102.8 × 64.5 One port
[5] h = 0.7 mm, εr = 2.2,
ta
n
δ= 0.02
8
4
× 5
4
One port
[9] Coppe
r
-plated
polyimide substrate
71 × 46 One port
[11] FR4, εr = 2.2 110 × 100 One port
T
his work FR4, εr = 4.
4
82 × 45 One port
V. CONCLUSIONS
In this paper, a dual-band antenna with HF and UHF band
frequencies has been presented. The HF antenna at 13.62 MHz
was designed by a three-turn spiral coil, and a novel MOCSRR
dipole structure was used to handle the UHF band from 917
MHz to 923.5 MHz. The proposed antenna has a compact size
of 82 mm × 45 mm and is printed to both sides of an FR4 sub-
strate with a thickness of 1.2 mm. In addition, the dual-band
antenna presents an omnidirectional characteristic at the UHF
frequency and the gain is approximately 1 dBi in the desired
UHF frequency range.
T
his
w
ork was supported by the National Research Foun-
dation of Korea (NRF) grant, which is funded by the Korean
Government (MSIP) (No. NRF-2017R1A5A1015596).
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Nam Ha-Van
received a B.S. degree in electronics and telecommu-
nications from Hanoi University of Science and
Technology, Hanoi, Vietnam, in 2012. He is cur-
rently working toward an integrated M.S./Ph.D.
degree in the department of information communi-
cation, materials, and chemistry convergence tech-
nology at Soongsil University, Seoul, Korea. His
current research interests include wireless power
transfer, metamaterials, RFID antennas, phased array antennas, and power
amplifiers.
and Wireless Propagation Letters, vol. 9, pp. 1037–1040, 2010.
[9] L. W. Mayer and A. L. Scholtz, "A dual-band HF/UHF
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Chulhun Seo
received B.S., M.S., and Ph.D. degrees in the de-
partment of electronics engineering from Seoul Na-
tional University, Seoul, Korea, in 1983, 1985, and
1993, respectively. From 1993 to 1995, he was a
technical staff member with the Massachusetts Insti-
tute of Technology (MIT), Cambridge, MA, USA.
From 1993 to 1997, he was an Assistant Professor at
Soongsil University, Seoul, Korea. From 1999 to
2001, he was a Visiting Professor with MIT. From 1997 to 2004, he was
an Associate Professor with Soongsil University, where he has been a Pro-
fessor of electronic engineering since 2014. Currently, he is the Dean of the
Information and Telecommunications College, at Soongsil University. He
is also the Director of the Wireless Power Transfer Research Center, which
is supported by basic research laboratories through the National Research
Foundation grant funded by the Ministry of Science, ICT and Future
Planning. His research interests include wireless communication technolo-
gies, radio frequency power amplifiers, and wireless power transfer using
metamaterials. Dr. Seo was the IEEE MTT Korea Chapter Chairman
from 2011 to 2014. He is the President of the Korean Institute of Electro-
magnetic Engineering and Science.