Page 105 - 2023-Vol19-Issue2

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tennas can enable devices to operate at different frequency
bands or communication protocols according to the varia-
tion of environmental conditions. The design of a frequency-
reconfigurable multimode antenna requires careful consider-
ation of several factors, including the frequency range, size,
bandwidth, gain, radiation pattern, impedance matching, cost,
and tuning methods. The antenna should be able to switch
between different configurations quickly and efficiently while
maintaining high performance in terms of gain, efficiency, and
radiation pattern [13]. Generally, the frequency reconfigurable
multimode antennas are a promising solution for wireless com-
munications in IoT devices, which enable devices to operate
at multiple frequency bands and modes as well as their ability
to adapt the system to the fluctuated channel conditions. Some
of the most important examples of IoT applications that use
reconfigurable antennas are listed below [14], [15], [16], [17]: a gain of 1.2 to 3.6 dBi and an efficiency of 84% and with an
1. Smart homes and buildings: Reconfigurable antennas
can adapt to different wireless communication standards, such
as Wi-Fi, ZigBee, or Bluetooth to ensure reliable wireless
communication between IoT devices.
2. Industrial IoT: Reconfigurable antennas can enable
wireless communication in harsh environments with high lev-
els of interference or signal attenuation by adjusting the an-
tenna’s radiation pattern or frequency band.
3. Healthcare: Reconfigurable antennas can be used in
wearable medical devices, such as biosensors, to improve
wireless communication reliability and reduce interference
from other sources.
4. Agriculture: Reconfigurable antennas can improve
wireless communication in agricultural IoT systems, such as
precision farming, by adjusting the antenna’s radiation pattern
to focus the energy in a specific direction.
The design of reconfigurable antennas for IoT applica-
tions requires careful consideration of the communication
standards, frequency bands, and environmental conditions in
which the antenna operates. The use of multimode reconfig-
urable antennas for IoT applications has been the subject of
extensive research in recent years. These antennas can operate
on multiple frequency bands and communication protocols,
making them suitable for various IoT applications.
In [14], the authors propose a frequency-reconfigurable
antenna with a combination of an open loop filter and a hair-
pin bandpass filter. The reconfigurability is achieved by PIN
diodes for various switching conditions, the designed antenna
resonates at 2.47 GHz, 7.18 GHz, 12.14 GHz, 3.42 GHz, 14.55
GHz, and 8.4 GHz. A reconfigurable pattern multifunctional
compact antenna was proposed in [18]. The feeding network
changes and the ground plane is used as a reflector to make
the pattern changeable. To make it compatible with brand-new
Internet of Things devices, the antenna is reformed to be like a
credit card. The proposed reconfigurable antenna is achieved
Abdulzahra, Alnahwi & Abdullah
with four PIN diodes, and the configuration efficiencies are
achieved with a low-cost, lossy FR-4 substrate. In [19], a
reconfigurable printed antenna for portable IoT applications
was proposed. A design for an air gap-separated smart-printed
monopole antenna and a hexagonal matching load (HML) is
suggested. A coplanar waveguide supplies the patch, and two
PIN diodes connect the HML to the ground plane to control
the surface current motion and enable antenna reconfiguration.
A microwave frequency band-operating low-profile frequency
reconfigurable monopole antenna was suggested in [20]. The
proposed structure is printed on an FR-4 substrate, and four
PIN diodes are embedded between transmitting patches for
exchanging the different working modes. The proposed de-
sign covers single, dual, and triple bands. At the appropriate
resonant frequency (or frequencies), the designed antenna has
overall size of 40 × 32 × 1.6 mm3. The antenna is usable in
both IoT-enabled systems in smart cities and modern handheld
fifth-generation (5G) devices due to its relatively small size
and its support for multiple wireless standards.
In general, these studies demonstrate the potential of mul-
timode reconfigurable antennas for IoT applications. The
reconfigurability of these antennas enables them to operate
at multiple frequency bands and communication protocols,
as well as to improve their flexibility and versatility. The
compact size and wideband operation of these antennas also
make them suitable for various IoT devices. However, further
research is needed to optimize the design and performance of
these antennas and to evaluate their performance in real-world
IoT applications.
In this article, a compact frequency reconfigurable antenna
for IoT applications is suggested. A single PIN diode is
used to modify the current of the radiating patch to ensure a
wideband mode at the ON state. The OFF state of the PIN
diode results in two monopoles with different lengths that
make the antenna operate in dual-band mode. The diode is
positioned on a slit engraved on the antenna patch to change
the electrical length of the radiating element by altering the
distribution of the surface current according to its state. The
whole size of the antenna is (26×19×1.6) mm3 with two modes
of operation. The operational range for the ON-state is (2.95-
8.2) GHz, whereas the OFF-state provides bi-band operation
of 3 GHz and 6 GHz for WiMAX and WLAN applications.
The proposed frequency reconfigurable antenna design
steps are discussed in Section II. Section III illustrates the
PIN diodes configurations, their states, and their operating
modes. In order to find the optimal parameter values for
the proposed design, a parametric study has been carried out
in Section IV. The proposed antenna simulated results are
discussed in Section V in addition to a comparison with some
relevant works. Section VI summarized this work with a brief