A NEW APERTURE-COUPLED PATCH
ANTENNA
C. H. Cheng,
1
K. Li,
2
K. F. Tang,
2
and T. Matsui
2
1
Laboratory of Electromagnetic Field and Microwave
Department of Communications Engineering
Nanjing University of Posts and Telecommunications
Nanjing 210003, P. R. China
2
Millimeter-Wave Devices Group
Communications Research Laboratory (CRL)
4-2-1, Nukui-kita, Koganei
Tokyo, 184-8795, Japan
Received 1 February 2003
ABSTRACT: A new aperture-coupled patch antenna is presented, in
which the patch is surrounded by a conductor ground and the sides of
the dielectric substrate are covered with conductor walls. The antenna
was investigated numerically and experimentally. Result shows that the
antenna has a bandwidth of about 28% (for |S
11
| -10 dB) centered
at 10 GHz and an average gain of about 7.4 dBi over the operating
frequency range, which are better than that of a conventional aperture-
coupled patch with the same parameters. At the same time, the antenna
maintains a good radiation pattern. © 2003 Wiley Periodicals, Inc.
Microwave Opt Technol Lett 38: 422– 423, 2003; Published online in
Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.
11079
Key words: microstrip antennas; aperture-coupled patch; wide band-
width; high gain
1. INTRODUCTION
Aperture-coupled patch antennas exhibit a number of advantages
such as broad bandwidth, weak parasitic radiation in the useful
direction, and convenient impedance matching owing to the large
number of feed parameters [1– 4]. These features make it an
attractive structure for microwave and millimeter-wave applica-
tions. In this paper, we present a new aperture-coupled patch
antenna in which the patch is surrounded by a conductor ground.
The structure of this antenna was proposed in [5], and it is fed by
a coplanar waveguide (CPW). Compared with a conventional
patch, the new structure has the advantage of no surface-wave
problem. For conventional aperture-coupled patches, the surface
waves not only introduce power loss, but also produce reflection
and diffraction at the edges of the substrate.
However, parallel-plate modes will be excited between the two
conductor grounds, because the new patch is excited with an
aperture cut on the conductor background. The parallel-plate
modes will introduce power loss and produce reflection at the sides
of the dielectric substrate as well. Therefore, in order to reduce the
power loss introduced by the parallel-plate modes, in our design
the sides of the dielectric substrate are covered with four conductor
walls.
In this paper, a new aperture-coupled patch antenna is investi-
gated numerically and experimentally. The commercial software
IE3D is used for the antenna simulation over the frequency range
8 –12 GHz. Many samples have been fabricated and measured
according to the dimensions obtained in simulation. The parame-
ters measured include return loss, gain, and radiation pattern. Also,
the antenna is compared with a conventional aperture-coupled
patch with the same parameters. Result shows that the new patch
Figure 1 Geometrical configuration of a new aperture-coupled patch
antenna: (a) conductor ground, (b) patch: L
p
W
p
, (c) substrate 2:
r2
=
2.17, h
2
= 2.4 mm, tan
2
= 0.00085, (d) conductor walls (conductor
cavity: L
c
W
c
), (e) aperture: L
a
W
a
, (f) conductor background, (g)
microstrip feed-line: W
f
, L
s
, and (h) substrate 1:
r1
= 2.17, h
1
= 0.508
mm, tan
1
= 0.00085
Figure 2 Measured return loss | S
11
| of the two antennas over the
frequency range 8 –12 GHz ( L
p
= 7.6 mm, W
p
= 10.0 mm, L
a
= 7.4
mm, W
a
= 0.4 mm, W
f
= 1.6 mm, L
s
= 2.6 mm, L
c
= 22.0 mm, W
c
=
23.0 mm, W
s
= 3.0 mm)
Figure 3 Measured gain of the two antennas over the frequency range
8 –12 GHz
422 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 38, No. 5, September 5 2003