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10.1109/LAWP.2015.2458351, IEEE Antennas and Wireless Propagation Letters
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Abstract—A Yagi-Uda antenna with a stepped-width reflector
is presented. Totally different with the traditional ones, the
proposed reflector is shorter than the driven element as a result of
the stepped-width structure. To further understand its working
mechanics, an equivalent circuit to a dipole with a parasitic
element is employed to explain the shortened length of the
stepped-width reflector. Then, the proposed stepped-width
reflector, shorter than the driven element, was applied to design,
fabrication and measurement of a Yagi-Uda antenna. Measured
results show a good agreement with the simulated ones. In
particular, the total length of the reflector employed in the
Yagi-Uda antenna is 50 mm and that of the driven element is 53
mm, which verifies the shorter length of the reflector and benefits
achieving a smaller size.
Index Terms—stepped-width structure, a dipole with a
parasitic element, equivalent circuit, Yagi-Uda antenna,
miniaturized reflector.
I. INTRODUCTION
arasitic element antenna (PEA), which is now widely used
for communication systems, has great potential in terms of
frequency and radiation pattern agility [1] [2]. Compared to a
single element antenna, PEA offers a greater degree of freedom,
and does not suffer from the bulky feed distribution network of
antenna arrays. Yagi-uda antenna is a typical type of PEA and
is widely used in modern communication systems [3]-[10]. In
precedent literatures, uniform-width structures were employed
in reflectors, directors and driven elements. The driven
elements were always longer than the directors as shown in
Fig.1 (a) and shorter than the reflectors as shown in Fig.1. (b).
When the reflectors were longer than driven elements, they
would inevitably increase the overall size of the antenna. For
minimization, cylindrical covers were employed to reduce the
size of antennas [11], but the structure was complex. A
stepped-width dipole was employed in [12] to reduce the size of
the driven element, but the reflector and the overall size of the
antenna was still large. In [13], the filter with stepped-width
was used in filter minimization. This method can also be
constructively used in designing miniaturized reflector.
In this paper, a stepped-width reflector is presented and
This work was supported in part by the National Natural Science Foundation
of China (61171029 and 61471172), Guangzhou Technology Project
(201300000029), Funds for the Central Universities (2013ZP0018), the State
Key Laboratory of Millimeter Wave (K201406).
The authors are with the School of Electronic and Information Engineering,
South China University of Technology, Guangzhou, China (e-mail:
luoy.lyu@mail.scut.edu.cn; qxchu@scut.edu.cn)
analyzed by an equivalent circuit. In the equivalent circuit, the
parasitic element is equivalent to a resistor loaded in a short
circuit line. The stepped-width structure applied in reflector
shortening the reflector in comparison to the driven element can
decrease the resonate frequency, as also the size of reflector. A
Yagi-Uda antenna, involving the proposed miniaturized
reflector, was designed, fabricated, and measured to confirm
the proposed concept.
A Yagi-Uda Antenna with a Stepped-width
Reflector Shorter than the Driven Element
Yu Luo, Student Member, IEEE and Qing-Xin Chu, Senior Member, IEEE
(a) a dipole with uniform-width director
(b) a dipole with uniform-width reflector
(c) a dipole with stepped-width reflector
Fig.1 A dipole width three different parasitic elements and their E-plane radiation
patterns.