Article
Medium-Sized Highly Coupled Planar Arrays with Maximum
Aperture Efficiency
Peyman Pourmohammadi, Vladimir Volski and Guy A. E. Vandenbosch *
Citation: Pourmohammadi, P.;
Volski, V.; Vandenbosch, G.A.E.
Medium-Sized Highly Coupled
Planar Arrays with Maximum
Aperture Efficiency. Sensors 2021, 21,
5925. https://doi.org/10.3390/
s21175925
Academic Editor: Ángela María
Coves Soler
Received: 29 June 2021
Accepted: 31 August 2021
Published: 3 September 2021
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4.0/).
ESAT-WAVECORE Research Division, Katholieke Universiteit Leuven (KU Leuven), Kasteelpark Arenberg 10,
3001 Leuven, Belgium; peyman.pourmohammadi@esat.kuleuven.be (P.P.);
vladimir.volski@esat.kuleuven.be (V.V.)
* Correspondence: guy.vandenbosch@esat.kuleuven.be
Abstract:
This paper presents a technique to design strongly coupled planar arrays with very high
aperture efficiency. The key innovation is that, based on an irregular 2
×
1 array, very compact
medium-sized arrays of size 2
×
2, 2
×
4, and 2
×
6 are constructed with very strong and constructive
mutual coupling between the elements. In this way, a maximum aperture efficiency is reached for
a given footprint of the array. The occupied space of the antenna in comparison with conventional
linear patch arrays is studied. A prototype 2
×
4 array operating around 5.8 GHz is designed,
fabricated, built, and measured. The results show a large bandwidth of 20% and a very high aperture
efficiency of 100%, which is the largest found in the literature for similarly sized arrays. These results
are important in view of the future Internet of Things, where small and medium-sized arrays are
planned to be mounted on numerous devices where a very limited physical area is available.
Keywords:
antenna array; aperture efficiency; Internet of Things (IoT); multi input-multi output (MIMO)
1. Introduction
During the last decade, wireless devices such as mobile phones, navigation systems,
etc., have become an intimate part of our daily life. Hence, antennas as one of the key
components in wireless communication systems have received a lot of attention. Planar
(patch) antennas are one of the attractive candidates for wireless communications, thanks
to the lightweight, low profile, low cost, easy fabrication, and ability to integrate with
microwave circuits [1].
In many cases, it is required to design antennas with high gain. One of the easiest ways
to increase gain is to use an array structure [
1
]. However, due to the physically limited space
in small devices, the typically available footprint of the antenna is limited and the array
has to be miniaturized. High gain for a small footprint means a high aperture efficiency [
2
].
Aperture efficiency is a well-known quantity in the field of antennas. However, since it is
the core concept of this paper, for completeness we repeat its definition here. The aperture
efficiency of an antenna is the ratio of the effective receiving area of an antenna to the
physical area of the antenna, see Equation (1). In other words, this quantity describes how
effective an antenna is receiving power [
2
]. It is directly related to the gain of the antenna,
see Equation (2).
η =
A
eff
A
(1)
A
eff
=
λ
2
× G
4π
(2)
where
A
is the physical area of the antenna,
λ
is the wavelength in free space, and G is the
gain of the antenna. Note, since the directivity is not affected by losses in the antenna, the
gain is considered instead of directivity in Equation (2). The antenna gain is the product of
directivity and efficiency.
Sensors 2021, 21, 5925. https://doi.org/10.3390/s21175925 https://www.mdpi.com/journal/sensors
