Off-Body Antenna Dual-Beam Linear to Circular
Polarization Converter Based on Quarter-wave
Cross-Slot Frequency Selective Surface
Amine Habani, Mourad Nedil
Engineering School, UQAT, LRTCS
Val d’Or, Canada
amine.habani@uqat.ca, mourad.nedil@uqat.ca
Tayeb A.Denidni
INRS, Montréal, Canada
denidni@emt.inrs.ca
Larbi Talbi
UQO, Quebec, Canada
larbi.talbi@uqo.ca
Abstract—This paper presents a dual-beam wearable antenna
based on AMC-FSS technology with a transmission type polarizer to
convert linear to circular polarization at 5 .8 GHz. The design is
composed of 3 layers, an AMC substrate, a planar monopole and a
tilted 45° cross-slots FSS superstrate. The structure provides a 1.69
dB of axial ratio purity polarization and a valuable gain of 7.32 dBi
at the ISM band. T he dual beam radiation pattern makes the
antenna a good candidate for Off-Body underground
communications.
Keywords—Wearable antenna; AMC substrate ; polarizer; FSS
superstrate; circular polarization
I. INTRODUCTION
In the last decade, Wireless Body Area Network (WBAN) has
received an increased attention in underground mine applications
to improve the safety of the miners [1 – 2]. In fact, the miner’s
garment is fully equipped with several sensors collecting
dangerous gases rate and vital body parameters which are then
transmitted to a command station [3]. Off-Body antennas are used
for this purpose, since they are known to be in a compact size,
light weight, low profile and low cost.
High two dimensional grating surfaces impedance have
emerged as a new technology for developing Off-Body antennas
[4]. These periodic structures act as Perfect Magnetic Conductors
(PMC) within a specific frequency range. These surfaces achieve
a high front to back ratio (FBR) and immunity toward the human
body tissue.
However, Off-Body linear polarization antennas can no longer
be used for applications where the polarization tilt is unknown or
is dynamically changing due to miners movements. Thus, circular
polarization is required in these cases, for its susceptibility to
multipath, atmospheric absorptions, reflections and hazardous
conditions in underground mines [5]. The approaches adopted
consist of converting an antenna array radiating linearly polarized
into a CP wave with a polarizer positioned in front of the antenna
by phase shifting one component of the linear electric field by
(90º). The polarizer used to perform this conversion can be
realized in different ways such as: Dielectric, grid-plate and
meander-line polarizers [6 -7]. Superstrates, such as Frequency
Selective Surfaces are a viable solution for generating CP waves
for its low profile and ease fabrication [8].
This paper proposes a combination of AMC structure with
polarizer-based FSS quarter-wave cross-slots in the OFF-Body
antenna in order to have the both performances (Higher FBR and
CP polarization with higher gain).
Fig 1. Layout of the proposed AMC-FSS based polarizer antenna.(all dimensions
are in mm) a. AMC structure, b. planar monopole, c. Polarizer, d. antenna
topography(Gx=Gy=63,Lc=13.5,Wc=1,g=0.5,Ga=6,Ax=38,Ay=30,gnd=11.5msl
=10,msw=0.96,ml=23,mw=23,e=3.5,Wp=45,Lp=48,bx=12,by=3,h1=3.175,h2=0.
508,hp=1.905,d1=3,d2=20,𝜀𝑟=12.96 (F/m)
II. ANTENNA DESIGN
The proposed antenna is composed of three substrates
components separated by a foam spacer as follows: First, an
anisotropic AMC structure (dielectric TMM4), having a 3x3 Four-
arm square spiral array with metallic sheet backing is placed on
the bottom layer as illustrated in Fig. 1 (a). Second, as proposed in
[9], a planar monopole antenna fed by a microstrip line is located
on the middle layer as denoted in Fig 1.(b). Third, a polarizer
2031978-1-5386-7102-3/18/$31.00 ©2018 IEEE AP-S 2018
