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IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS, VOL. 8, 2009
A Small Printed Quasi-Self-Complementary Antenna
for Ultrawideband Systems
Lu Guo, Student Member, IEEE, Sheng Wang, Xiaodong Chen, Senior Member, IEEE, and
Clive Parini, Member, IEEE
Abstract—A novel and simple ultrawideband (UWB) printed
quasi-self-complementary antenna is presented. The proposed
antenna, which is fed by a microstrip line, has been demonstrated
to provide an ultrawide 10-dB impedance bandwidth with satisfactory radiation properties. It also features both physically and
electrically small dimensions, 16 mm 25 mm in a physical size
and 0 24 in an electrical size, respectively. The key parameters
that affect the performance of the antenna are investigated. A
good agreement is achieved between the simulation and the measurement.
Index Terms—Printed circuit board (PCB) antenna, self-complementary antenna, small antenna, ultrawide band (UWB) antenna.
I. INTRODUCTION
INCE the approval by the Federal Communication Commission (FCC) of a 3.1–10.6-GHz frequency band allocation to the ultrawideband (UWB) radio technology, there have
been considerable research efforts dedicating to this promising
technology worldwide [1]. Consequently, as a critical part of the
entire system, UWB antennas have been receiving increasing
interest from both the academia and industries. Recent UWB
antenna designs mainly focus on miniaturized antennas due
to their ease of integration into space-limited systems [2]–[6].
Among those miniaturized UWB antennas, self-complementary
antennas [5], [6] have illustrated their promising prospects with
broadband characteristics. Recently, our group has developed
a printed quasi-self-complementary antenna that is fed by a
50– coplanar waveguide without using a matching circuit [7].
The antenna exhibits an ultrawide 10-dB impedance bandwidth
as well as reasonable radiation properties. However, it presents
a relatively large physical size that still could be a challenge for
integration into space-limited systems.
In this letter, a very small-size printed quasi-self-complementary antenna fed by a microstrip line is presented. A triangular
slot is inserted on the ground plane to enhance the impedance
matching of the antenna. It has been shown that the optimal design of this type of antenna can offer an ultrawide impedance
S
Manuscript received January 13, 2009; revised February 16, 2009. First published March 24, 2009; current version published June 24, 2009.
The authors are with the Department of Electronic Engineering, Queen
Mary, University of London, London E1 4NS, U.K. (e-mail: lu.guo@elec.
qmul.ac.uk; sheng.wang@elec.qmul.ac.uk; xiaodong.chen@elec.qmul.ac.uk;
c.g.parini@elec.qmul.ac.uk).
Color versions of one or more of the figures in this letter are available online
at http://ieeexplore.ieee.org.
Digital Object Identifier 10.1109/LAWP.2009.2018711
Fig. 1. Geometry of the proposed microstrip line-fed quasi-self-complementary antenna.
bandwidth with satisfactory radiation properties. Key parameters that influence the performance of the antenna are investigated. Most importantly, the proposed antenna features both
physically and electrically small dimensions, 16 mm 25 mm
in an electrical size, respectively.
in a physical size and
II. ANTENNA DESIGN AND PERFORMANCE
The proposed small printed quasi-self-complementary antenna is shown in Fig. 1.
A half-circular disc with a radius of and its complementary
magnetic counterpart are printed on the different side of the dielectric substrate (in this letter, the FR4 substrate of thickness
mm and relative permittivity
was used).
and
represent the length and the width of the dielectric substrate, respectively. In addition, a triangular notch is cut on the
ground plane in order to improve the impedance matching.
and
denote the width and height of the triangular notch, respectively.
The simulations are conducted using the CST Microwave
Studio package, which utilizes the finite integration technique
for electromagnetic computation [8].
1536-1225/$25.00 © 2009 IEEE
GUO et al.: QUASI-SELF-COMPLEMENTARY ANTENNA
555
Fig. 4. (color online) Simulated (blue line) and measured (red line) radiation
patterns with the optimal design at 3.07 GHz. (a) E-plane. (b) H-plane.
Fig. 2. The prototype of the proposed microstrip line fed quasi-self-complementary antenna, (a) front side and (b) back side.
Fig. 5. (color online) Simulated (blue line) and measured (red line) radiation
patterns with the optimal design at 9.31 GHz. (a) E-plane. (b) H-plane.
Fig. 3. (color online) Simulated (blue line) and measured (red line) return loss
curves of the proposed printed quasi-self-complementary antenna.
A prototype of the proposed printed quasi-self-complemm,
mentary antenna with optimal design—i.e.,
mm,
mm,
mm,
mm,
mm,
mm—is constructed in the Antenna Measurement Laboratory at Queen Mary, University of
London (QMUL), U.K., as shown in Fig. 2. The return losses
are measured by using a HP 8720ES network analyzer, and
the radiation pattern measurements are performed inside an
anechoic chamber.
Fig. 3 displays the simulated and the measured return loss
curves of the proposed antenna. The measured 10-dB return loss
bandwidth is from 2.86 to 10.7 GHz, while in simulation, from
2.8 to 11.3 GHz. The measurement confirms the UWB characteristic of the proposed printed quasi-self-complementary antenna, as predicted in the simulation. It is also noticed that the
antenna size is not only physically small, but also electrically
at 2.86 GHz.
small, only
Fig. 6. Simulated peak gain of the proposed antenna.
The measured and the simulated normalized radiation patterns at 3.07 and 9.31 GHz are plotted in Fig. 4 and 5, respectively. The patterns obtained in the measurement are close to
those in the simulation. It is observed that the H-plane patterns
are reasonable over the entire operating bandwidth. The simulated peak gain of the proposed antenna is plotted in Fig. 6; it is
seen that a satisfactory gain level is achieved through the whole
band.
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IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS, VOL. 8, 2009
W =6
L = 4:8
Fig. 7. Simulated return loss curves for different widths of the ground plane
mm and
mm.
with
W = 16
L = 4 :8
W = 16
W =6
Fig. 8. Simulated return loss curves for different widths of the triangular slot
mm and
mm.
with
III. EFFECTS OF DESIGN PARAMETERS
It has been shown in the simulation that the operating bandwidth of the printed quasi-self-complementary antenna is primarily dependent on the width of the antenna , the width
, and the height of the triangular slot
of the triangular slot
. These parameters should be optimized for maximum bandwidth.
A. The Effect of Antenna Width
Fig. 7 plots the simulated return loss curves with different
15, 16, 20, and 24 mm) when
is
antenna widths (
fixed at 6 mm and
at 4.8 mm, respectively. It can be seen
that the return loss curves vary significantly and exhibit varis changed, the
ious shapes for the four different . When
first resonant frequency does not change much; however, the
higher resonant frequencies vary dramatically, leading to the
variations of the operating bandwidth of the antenna, as shown
in Fig. 7. It is also interestingly noticed that when the width
increases, the impedance matching at the lower band degrades.
This is due to the fact that the antenna will more and more
resemble a genuine self-complementary structure with the extension of the width . This results in the antenna impedance
approaching more to 188.5 and consequently the mismatch
of the input impedance to the microstrip line. Basically, the
slotted microstrip line serves as a built-in transformer between
the self-complementary structure and the SMA. The optimal anmm.
tenna width is found to be at
B. The Effect of the Width of the Triangular Slot
The simulated return loss curves with
mm and
of 16 mm for different triangular slot
optimal antenna width
widths
are presented in Fig. 8. It is observed in Fig. 8 that
the return loss curves change substantially with the variation
. When
increases from 2 to 6 mm, the impedance
of
matching of the antenna gets better; however, the higher edge of
from
the bandwidth decreases. With the further increase of
6 to 8 mm, the impedance matching of the antenna becomes
Fig. 9. Simulated return loss curves for different heights of the triangular slot
with
mm and
mm.
worse ,and the higher end of the bandwidth keeps reducing. The
mm.
optimized triangular slot width is found to be at
C. The Effect of the Height of the Triangular Slot
Fig. 9 shows the simulated return loss curves for different
triangular heights
when
mm and
mm,
respectively. It is observed that the impedance matching is also
greatly dependent on the height of the triangular slot. When
is equal to 4.8 mm, the 10 dB bandwidth covers an ultrawide
frequency band; when decreases to 2.8 and 0.8 mm, the lower
edge of the bandwidth increases, and the impedance matching
mm becomes worse. When
rises to 6.8 mm, the
for
lower edge of the bandwidth reduces; however, the impedance
matching for midband is degraded.
IV. CONCLUSION
A novel and small UWB printed quasi-self-complementary
antenna is investigated in this letter. A prototype with the op-
GUO et al.: QUASI-SELF-COMPLEMENTARY ANTENNA
timal design has been fabricated, and its electrical performances
have been examined. The antenna demonstrates an ultrawide
impedance bandwidth with satisfactory radiation patterns. It
also exhibits both physically and electrically small dimensions,
in an electrical
16 mm 25 mm in a physical size and
size, respectively. The critical parameters that affect antenna
behaviors have been analyzed. The results show this antenna is
a good candidate for UWB applications.
ACKNOWLEDGMENT
The authors would like to thank J. Dupuy of the Department
of Electronic Engineering, QMUL, for his help in the fabrication
and measurement of the antenna. The authors would also like
to acknowledge Computer Simulation Technology (CST), Germany, for the complimentary license of the Microwave Studio
package.
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REFERENCES
[1] L. Yang and G. B. Giannakis, “Ultra-wideband communications: An
idea whose time has come,” IEEE Signal Process. Mag., vol. 21, no. 6,
pp. 26–54, Nov. 2004.
[2] L. Guo, Z. Yang, J. Liang, X. Chen, and C. G. Parini, “An improved
design of orthogonal half disc UWB antenna,” in Proc. EuCAP, Nice,
France, Nov. 6–10, 2006.
[3] Z. Chen, T. See, and X. Qing, “Small printed ultrawideband antenna
with reduced ground plane effect,” IEEE Trans. Antennas Propag., vol.
55, no. 2, pp. 383–388, Feb. 2007.
[4] M. Sun and Y. Zhang, “Miniaturization of planar monopole antennas
for ultrawide-band applications,” in Proc. IEEE Int. Workshop on Antenna Technol.: Small Antennas and Novel Metamater., Cambridge,
U.K., Mar. 21–23, 2007, pp. 197–200.
[5] P. Xu, K. Fujimoto, and S. Lin, “Performance of quasi-self-complementary antenna using a monopole and a slot,” in Proc. IEEE Antennas Propag. Soc. Int. Symp., San Antonio, TX, Jun. 16–21, 2002,
pp. 464–467.
[6] K. Wong, T. Wu, S. Su, and J. Lai, “Broadband printed quasi-self-complementary antenna for 5.2/5.8 GHz WLAN operation,” Microw. Opt.
Technol. Lett., vol. 39, no. 6, pp. 495–496, Dec. 20, 2003.
[7] L. Guo, S. Wang, Y. Gao, Z. Wang, X. Chen, and C. G. Parini, “Study
of a printed quasi-self-complementary antenna for ultra wideband systems,” Inst. Elect. Eng. Electron. Lett., vol. 44, no. 8, pp. 511–512, Apr.
10, 2008.
[8] “User’s Manual,” CST-Microwave Studio, 2003.