RADIOENGINEERING, VOL. 18, NO. 4, DECEMBER, 2009 551
A CPW-Fed Novel Planar Ultra-Wideband Antenna
with a Band-Notch Characteristic
Fei YU, Chunhua WANG
School of Computer and Communication, Hunan University, Changsha 410082, P.R.China
yufeiyfyf@yahoo.com.cn, wch1227164@sina.com
Abstract. A coplanar waveguide (CPW) fed novel planar
ultra-wideband antenna with a band-notch characteristic
is presented. The proposed antenna consists of a rec-
tangular metal radiation patch and a tapered arc-shaped
ground plane. To achieve ultra wideband, three
modifications are introduced, the first one is to remove
a 90-degree fan angle on the upper corners of the patch,
the second one is to shape the bottom of the patch into an
arc, and the third modification is to remove a small fan
angle on each side of the ground plane near the feeding
line. Simulation results show that the proposed antenna
operates over 3.0 to 23 GHz for VSWR < 2. By embedding
a C-shaped slot in the radiating patch, a frequency band
notch between the bandwidth of 5 to 6 GHz for Wireless
LAN (WLAN) will be obtained. All simulations in this work
were carried out by using the electromagnetic software
Ansoft HFSS 11. Compared with the recently proposed
antennas, this antenna has advantages in wide bandwidth,
good band-notch characteristic, compact in size and easy
design. Details of the proposed antenna are presented, and
simulated results show that the antenna has stable
radiation patterns and good gain flatness over its whole
frequency band.
Keywords
Coplanar waveguide (CPW), ultra wideband (UWB),
planar UWB antenna, C-shaped slot, band-notched
characteristic.
1. Introduction
Since the first Report and Order by the Federal
Communications Commission (FCC) authorized the
unlicensed use of UWB which must meet the emission
masks on February 14, 2002, both industry and academia
have paid much attention to R&D of commercial UWB
systems [1]-[3]. In UWB systems, antenna design is one of
key technologies, and a suitable UWB antenna needs to
fulfill requirements set by UWB technology and by
portable devices alike, such as ultra wide bandwidth,
directional or omnidirectional radiation patterns, constant
gain and group delay over the entire band, high radiation
efficiency and small size. Meanwhile, planar UWB antenna
fed with a microstrip line or a coplanar waveguide (CPW)
has received much attention due to its advantages such as
wideband characteristic, bidirectional radiation patterns.
Especially, it is easy to integrate the CPW-fed antennas
with a UWB chip. Many CPW-fed antenna configurations
have been proposed and developed [3]-[7]. However, these
antennas for UWB communication also need a band-
rejection filter to avoid interference with existing wireless
networks with standards such as IEEE 802.11a in USA
(5.15 GHz - 5.35 GHz, 5.725 GHz - 5.825 GHz) and
HIPERLAN/2 in Europe (5.15 GHz - 5.35 GHz, 5.47 GHz
to 5.725 GHz) [4]-[7]. To avoid adding new circuits to the
communication system, band-notching technique can be
applied directly to various UWB planar antennas by
loading the UWB antenna with a resonant slot at the center
frequency of the stop band. Different configurations of this
slot have been introduced for this purpose such as U-shape
[4], C-shape [5], spoon-shape [6] and V-shape [7].
In this paper, a CPW-fed novel planar ultra-wideband
antenna with a band-notch characteristic is introduced. In
order to obtain ultra wideband and rejected band
characteristic, some modifications about the antenna are
introduced and a C-shaped slot is inserted in the radiating
patch. The simulated results show that the proposed
antenna presents a very wide impedance bandwidth and
a band-notch characteristic. Sec. 2 presents the details of
the antenna structure and the design procedure. Sec. 3
analyses the radiation patterns and current distribution. The
curve of frequency-gain is also given. Finally, the
conclusion is presented in Sec. 4.
2. Antenna Design
The geometrical configuration of the proposed
antenna is depicted in Fig. 1 and the parameters are
summarized in Tab. 1. This antenna is fed by a 50-Ω CPW
and has dimension of 28×30 mm that is fabricated on the
FR-4 substrate with a thickness (H) of 1.6 mm and relative
dielectric constant of 4.4, loss tangent tanδ = 0.02. The
proposed antenna is located in x-y plane and the normal
direction is parallel to z-axis. The proposed antenna is
composed of a rectangular metal radiation patch and
a tapered arc-shaped ground plane. Two modifications are