similar relative dielectric constant and substrate thickness as
well as feeding structure. As expected, microstrip antennas in
Table 1 that employed a coupled feed are observed from 0.65%
to 1.33% for the CP bandwidths. However, the proposed
antenna exhibits up to 3.79% of the 3-dB AR bandwidth by
only changing the feeding lengths without using any additional
design method. It is noted that the proposed antenna produces
improved CP bandwidths compared with the CP bandwidth
results shown in Table 1.
The far-field radiation patterns of the proposed antenna for
LHCP operation are shown in Figure 6. The CP radiation patterns
are measured at 2.46 and 2.51 GHz, respectively. As expected,
the radiation patterns at the two frequencies remained unchanged;
that is, the patterns are not degenerated. In addition, the CP sense
(LHCP in this case) is maintained at the two frequencies with
minimum ARs. The radiation patterns at each frequency are sym-
metric; that is, those in the yz-plane and the zx-plane are identical.
The results shown in Figures 4–6 demonstrate that the proposed
Y-shaped feed provides broad and symmetrical CP radiation
performance in the z-direction.
4. CONCLUSION
The simple design of the single asymmetrical feed structure is
analyzed and demonstrated for broad CP operation of a square
microstrip antenna. The proposed structure does not contain a
radiator perturbation element, a thick substrate with an air gap, or
employ a complex feed circuitry with a power diver and a phase
shifter. A single microstrip line with divided branch lines for
asymmetrical coupling can, therefore, be used to extend the 3-dB
AR bandwidths of the single-fed square microstrip antenna. As
such, the proposed feed design may prove to be a good candidate
for microstrip antennas that require broad impedance and AR
bandwidths in emerging wireless communications.
ACKNOWLEDGMENT
This research was supported by Basic Science Research Pro-
gram through the National Research Foundation of Korea (NRF)
funded by the Ministry of Science, ICT & Future Planning (No.
2014R1A1A1004241).
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V
C
2016 Wiley Periodicals, Inc.
A METAMATERIAL-INSPIRED WIDEBAND
HIGH-GAIN FABRY–PEROT RESONATOR
MICROSTRIP PATCH ANTENNA
Hang-Ying Yuan,
1
Shao-Bo Qu,
1
Jie-Qiu Zhang,
1
Jia-Fu Wang,
1
Hong-Ya Chen,
1
Hang Zhou,
1
Zhuo Xu,
2
and
An-Xue Zhang
3
1
College of Science, Air Force Engineering University, Xi’an, 710051,
China; Corresponding author: qushaobo@mail.xitu.edu.cn
Figure 6 Measured radiation patterns of the proposed antenna with
LHCP operation at 2.46 and 2.51 GHz. (a) yz-plane; (b) zx-plane
DOI 10.1002/mop MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 58, No. 7, July 2016 1675