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This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI 10.1109/TAP.2017.2761987, IEEE
8 First Author et al.: Title
Abstract—As it is well known, the bandwidth of antenna will decrease
with the decrease of antenna size and this feature limits the design of
compact GNSS patch antenna (1.1GHz-1.6GHz). In this communication, a
novel wideband technique based on the mode analysis on the shorting load
patch antenna is proposed. By adjusting the position and the size of the
shorting load structure, the dominant resonant mode of patch antenna(TM
10
)
is divided into two secondary modes and these two modes are combined
together to form a wide operating band. It is proved that this new method
has better bandwidth enhancement effect than traditional methods. By
utilizing this proposed method, a compact circularly polarization(CP)
wideband patch antenna is designed for GNSS application, which has a
small electrical size of only 0.2λ
0
×0.2λ
0
×0.05λ
0
(λ
0
is the wavelength of low
band in free space). The simulated and measured results show that the
proposed antenna has good and stable performance over the whole
operating band, which means that it is quite an ideal compact antenna used
for GNSS satellite navigation applications.
Index Terms—circular polarization, microstrip antennas,
broadband antennas, shorting load, wideband patch antenna.
I. INTRODUCTION
As it is known, the satellite navigation system is quite vulnerable to
all kinds of jammers. In order to address this drawback, the adaptive
anti-jamming array is generally adopted in military system. Designing
such array demands miniature antenna elements(or small “footprint”
antenna) which take much less transverse space than conventional
antenna. Several small "footprint" antenna elements used for
anti-jamming array have been proposed [1, 2] recently. The transverse
size of these antenna is less than 0.2λ
0
(λ
0
is the wavelength of
working frequency in free space).
At the meantime, Global Navigation Satellite System(GNSS) with
bandwidth cover all the spectra (1.164GHz-1.610GHz) of the four
operating systems has drawn great attentions [3]. Hence, wideband
GNSS anti-jamming array naturally become a research hotspot and
wideband small footprint GNSS antenna element is in urgent needed.
Designing a small footprint GNSS antenna element which has
transverse size less than 0.2λ
0
, is the goal of this communication.
Besides that, the height should be less than 0.05λ
0
in order to limit the
surface wave.
Patch antenna is a better candidate for small “footprint” GNSS
antenna than other antenna forms(spiral antenna [4] or cross dipole [5])
due to its easy to achieve compact size(almost all the reported small
Manuscript received June 13, 2017; revised July 26, 2017; accepted October
1, 2017; Date of publication XXXXX; date of current version XXXX. This
work was supported in part by the National Natural Science Foundation of
China under Grant 61627901, in part by the Doctoral Scientific Research
Foundation of Yulin Normal University under Grant 2017002.
C. Sun and B. W. Bai are with the School of Aerospace Science and
Technology, Xidian University, Xi’an 710071, (e-mail:
sunchao1989913@163.com; bwbai@xidian.edu.cn).
Z. Wu is with the college of Physical Science and Technology, Yulin
Normal University, Yulin 537000, (e-mail:kianty@163.com)
footprint anti-jamming array antennas are patch antennas). By
utilizing high dielectric substrate or shorting load technique, the size
requirement is easy to fulfill. However, small size and wideband are
two contradictory demands for antenna and either miniature method
will lead to dramatical decrease of bandwidth, which means that for
GNSS small footprint antenna, bandwidth enhancement method is
needed to compensate this decrease of bandwidth.
Many techniques have been proposed for bandwidth enhancement
of patch antenna. Firstly, L-probe feed or capacitance feed is the most
common seen wideband method [6]. The feeding structure is coupled
to the patch instead of directly connecting to the patch, the inductance
of feed probe is counteracted by the capacitance and the impedance
matching is achieved. Secondly, U shape slot technique is also a
conventional wideband method [7], by etching U shape slot on the
patch, the current on the patch changed and another resonance is
generated. Two resonance are combined together to form a wideband.
Third, dual layer patch antenna or parasitic element method is also a
quite common seen method [8]. Another resonance is brought by the
parasitic element and two resonances are combined together to form a
wideband. Besides that, stepped-impedance resonator(SIR) technique
is adopted in reference [6]. By combining two resonances modes of
patch antenna, 15% bandwidth is achieved. Last, folded patch
antennas are reported in reference [7], although the bandwidth meet
the GNSS requirement, the dimension is too large, the radiation
pattern and antenna structure is not symmetry, which is not suitable for
CP GNSS antenna.
TABLE I
THE SUMMARIZED OF WIDEBAND TECHNIQUE FOR PATCH ANTENNA
The size and bandwidth of patch antenna using these above
technique is summarized as Table I. It can be seen that, if the
dimension of antenna are restrained by 0.2λ
0
×0.2λ
0
×0.05λ
0
, none of
these antennas which employed the above wideband techniques are
capable of achieving the desired GNSS bandwidth(32%). It is due to
the bandwidth enhancement effect of these traditional method is not
insufficient. That’s why almost all of the reported small "footprint"
antenna are designed for single narrow band [8] or dual narrow bands
[9]. On the other side, no matter what wideband method is adopted,
almost all the transverse size of reported GNSS patch antenna is larger
than 0.3λ
0
[10]. A new wideband method which has better bandwidth
enhancement effect is needed to achieve the goal of this
communication.
Shorting load is quite a conventional miniature technique for patch
antenna and many researches on shorting load are focus on the
miniaturization issue of patch antenna. However, in this
communication, a research on the shorting loaded patch antenna is
done in order not to decrease the size but to increase the bandwidth of
patch antenna, which is rarely seen before. In section II, a detailed
mode analysis on shorting load on the patch is done and a new