Energy Selective Surface Superstrate on Antenna both Gain

Enhancement and HPM Protection

Adem Kocyigit

1,2 a

, Burak Çelik

, Mahmut Burak Karadeniz

, Onur Arsalı

Ebru Efeoğlu

and Bahattin Turetken

Institute of Science, Electronics and Telecommunication Engineering, Kocaeli University, Umuttepe, Kocaeli, Turkey

Department of Electronics and Automation, Bilecik Seyh Edebali University, Gulumbe, Bilecik, Turkey

Department of Electronics and Telecommunication Engineering, Kocaeli University, Umuttepe, Kocaeli, Turkey

Department of Software Engineering, Kütahya Dumlupınar University, Kütahya, Turkey

Keywords: Energy Selective Surfaces, ESS, Superstrate, HPM Protection.

Abstract: Energy selective surfaces (ESS) have gained great interest for one decade to protect vulnerable electronic

devices due to their adaptive surfaces against the power of electromagnetic waves. In this study, we designed

a double layer ESS structure both to enhance gain of an antenna in the case of low power electromagnetic

waves and to protect it against high-power microwave (HPM) or electromagnetic pulse (EMP). The antenna

was designed by using Rogers RT5880 substrate as rectangular patch with a line feed for the 2.45 ISM

(Industrial, Scientific, and Medical) band. The ESS layers as arrays were placed on the antenna as superstrate

by a distance. The design results revealed that ESS superstrate layers can increase gain of antenna in the

transmission band and protect antenna in the case of HPM. The ESS layers can be act as both superstrate and

protection layers at the same time.

1 INTRODUCTION

Antennas need to be protected against HPM and EMP

because they are the opening door to the outside of

the electronic parts of vehicles such as aircraft and

unmanned aerial vehicles (Huang et al., 2022). These

are realized with materials such as active absorber

metasurfaces (Luo et al., 2023), frequency selective

surfaces (FSS) (Chatterjee et al., 2024), plasma

confinements (L. Wang et al., 2022), ceramic-based

film materials (Zurauskiene et al., 2013) and large

magnetoresistive materials (Pannetier-Lecoeur et al.,

2007). The ESS is a field-induced surface sensitive to

the field intensity of the incident wave, is first

proposed by Liu et al. in a patent in 2009, and it has

been published as a paper in 2013 (Yang et al., 2013).

ESS structures which are typically designed as a two-

dimensional array, are integrated into the front end of

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a radar system or as a protective layer on an antenna,

operating as a power-dependent switch in free space

(Qin & Zhang, 2019). These structures have been

quite popular since 2017 and have attracted the

attention of many scientists (Gong & Zhang, 2021;

Hu et al., 2024; Zhang et al., 2019).

Metamaterials (MTM), FSS or partially selective

surface (PRS) periodic structures are used as antenna

superstrate layers to enhance the performance of

planar antennas (K & Pradeep, 2022; Kangeyan &

Karthikeyan, 2024). The efficiency, bandwidth, and

gain of planar patch antennas can be successfully

increased with antenna superstrates, and that these

antennas can be easily used in a wide variety of

applications, such as health monitoring and

communications (K.Sumathi et al., 2021; Melouki et

al., 2022). Sumathi et al. (2021) showed that the

operating frequency of the antenna can be configured

by using MTM multilayered superstrates and adding

176

Kocyigit, A., Çelik, B., Karadeniz, M. B., Arsalı, O., Efeo

glu, E. and Turetken, B.

Energy Selective Surface Superstrate on Antenna both Gain Enhancement and HPM Protection.

DOI: 10.5220/0014364000004848

Paper published under CC license (CC BY-NC-ND 4.0)

In Proceedings of the 2nd International Conference on Advances in Electrical, Electronics, Energy, and Computer Sciences (ICEEECS 2025), pages 176-181

ISBN: 978-989-758-783-2

diodes to them, and the gain can be increased from

3.66 dB to 7.36 dB by configuring the diodes

(K.Sumathi et al., 2021). In a study carried out by Dey

and Dey (2023), a broad-band miniaturized Fabry-

Perot cavity resonator antenna fabricated of a new

electromagnetic band gap (EBG) superstrate as a

rectangular patch antenna supported by PRS and

reactive impedance surface (RIS) was used, with a

bandwidth between 9.91 and 12.71 GHz (24.8) and a

gain increase of 6.59 dB compared to the reference

antenna was achieved (Dey & Dey, 2023). Abdelaziz

et al. (2023) designed a multiple-input multiple-

output (MIMO) circular spiral patch antenna using a

bifacial logarithmic spiral metamaterial superstrate

which acts as new planar concave-concave lens for

circularly polarized (CP) antenna system which are

used in 5G applications and the proposed top layer

increased the isolation, gain and bandwidth of the

antenna by about 32 dB, 3.47 dB and 900 MHz

respectively (Abdelaziz et al., 2023). Nguyen and Seo

(2023) demonstrated 33% bandwidth, -14.3 dBi

maximum peak gain, and a low specific absorption

ratio (SAR) by integrating a drilled ground plane

(DGS) and a holed dielectric superstrate layer

operating at a center frequency of 2.4 GHz to achieve

CP characteristics of an ultraminiature antenna and

gain enhancement (Nguyen & Seo, 2023).

According to our best knowledge, there are no

studies in the literature that use ESS structure as the

antenna top layer which both to protect the antenna

from high power electromagnetic waves and to

improve its performance. This study aims to improve

antenna performance while protecting antenna from

HPM or EMP by using ESS surfaces as the

superstrate. In this study, we have designed a patch

antenna for 2.45 GHz ISM band and superstrate ESS

layer to improve antenna properties at transmission

band and to protect antenna from HPM when the

diodes are in the ON state.

2 DESIGN OF ANTENNA AND

ESS STRUCTURES

In the modelling of ESS structures, a standard FSS or

metamaterial structure is constructed, and the patch

elements of these structures are connected to each

other by lumped diode elements exhibiting nonlinear

properties. Figure 1A shows the equivalent

capacitance and inductance model of a structure

designed as an ESS in an electromagnetic wave

environment. As can be seen here, the gaps between

the metal conductors exhibit capacitance properties,

while the metal conductors exhibit inductance

properties. Figure 1B shows the equivalent circuit

model of the PIN diodes used in ESS structures and

simplified representations of them in the OFF and ON

states. Here, the diodes are represented by a

capacitance when OFF state, and when the diodes are

triggered or ON state by the HPM, they are

represented by an inductance and a low resistance

connected in series (K. Wang et al., 2017).

Figure 1: A) Representation of the structures of the ESS

surface in the electromagnetic wave environment with

equivalent capacitance and inductance. B) Equivalent

circuit model of a PIN diode, simplified circuit

representation in the OFF and ON states, from left to right,

respectively (K. Wang et al., 2017).

The model of antenna and ESS were designed by

using CST Microwave Studio. Antenna was designed

on the Rogers RT5880 with the thickness of 1.52 mm.

Top view of antenna and other related design

specifications are displayed in Figure 2.

Figure 2: Top view of the antenna and its dimensions.

OFF

(A)

(B)

Energy Selective Surface Superstrate on Antenna both Gain Enhancement and HPM Protection

177

The ESS structure has been designed on the FR-4

substrates with 1.6 mm thicknesses as double layers.

While Figure 3A display ESS unit cell for 3D and side

views, Figure 3B indicates front-back and middle

layers. The dimension of the substrate was

determined as 12 mm. The cross length and width on

the front surface were 6.5 mm and 3.5 mm. The radius

of side circles was 6.5 mm. The distance between the

layers, which are diode placed, is 0.8 mm. The square

ring width in middle is determined 0.5 mm after

optimization of all parameters. The unit cell was used

to obtain superstrate array with 12 × 12 on the antenna

to test antenna performance in the case of

transmission and reflection.

Figure 3: A) 3D (left) and side (right) view and B) front-

back and middle layers of the designed ESS unit cell

3 RESULTS AND DISCUSSION

The return loss (S

) graph of antenna has been

illustrated in Figure 4. The inset of Fig. 4 exhibits

polar radiation pattern of antenna for 2.45 GHz centre

frequency. The main lobe magnitude for linear

scaling is 6.45 with 5 degrees direction. Side lobe

level of the antenna is -20 dB. The efficiency of the

antenna was determined to be 88.25%.

The transmission characteristics of ESS unit cell

is shown in Figure 5 with return loss and transmission

coefficient (S

) in the case of when the diodes are in

the OFF and ON states. The equivalent capacitance

these states. The ESS has two transmission bands in

the centre frequency of 2.40 GHz and 4.05 GHz.

When the diodes are in the ON state, the ESS provides

Figure 4: S

graph of the antenna. The inset shows the polar

radiation pattern at 2.45 GHz

shielding efficiency less than -25 dB at approximately

2.40 GHz and less than -20 dB for a wide band of 0-

4 GHz. The insertion loss for transmission is obtained

to be -0.39 dB. The obtained results are good

agreement with literature (Zhou et al., 2021).

Figure 5: A) S

and B) S

graphs of ESS unit cell for

ON/OFF diode states.

012345

-30

-25

-20

-15

-10

-5

4.05 GHz

S11 (dB)

Frequency (GHz)

C=0.2 pF

C=0

2.40 GHz

012345

-60

-50

-40

-30

-20

-10

S21 (dB)

Fre

uenc

(

GHz

)

C=0.2 pF

C=0

(A)

(B)

(A)

(B)

ICEEECS 2025 - International Conference on Advances in Electrical, Electronics, Energy, and Computer Sciences

178

The ESS unit cells were transformed the array and

used as superstrate layer on the antenna by a distance

of 32 mm. Figure 6A shows S

graphs of the

reference antenna and antenna-superstrate system.

When the diodes are in the OFF state (C=0.2 pF), the

profile almost was not affected from the

superstrate layer and the radiation pattern almost did

not change much. Main lobe is increased from 6.45 to

6.71. In the case of triggering or in the ON state of the

diodes, the transmission is declined. Figure 6B shows

peak gain graphs of the reference antenna and

antenna-superstrate system. Whereas the gain of

reference antenna is obtained as 8.09 dBi, the peak

gain increased to 12.24 dBi with ESS superstrate for

diodes were in the OFF state. When the diodes are in

the ON state in the ESS superstrate, the protection

mode has been activated and gain decrease to 2.45

dBi as shown in the broadband gain graphs at 2.45

GHz frequency.

Figure 6: A) S

graphs of antenna with ESS superstrate. B)

Broadband gain graphs of reference antenna and antenna-

superstrate system for the case of diodes are in the ON and

OFF states.

Table 1 indicates performance of the reference

antenna and antenna-superstrate systems for diodes

are in the ON state. These values were obtained from

3D Farfield plots of antennas. While the resonance

frequency did not change with antenna types, the S

parameters and efficiency of antenna slightly changed

for superstrate layer with diodes were in the OFF

state. However, the S

parameter increased -4.13 dB

and gain decreased to 2.04 dBi with 175 degrees after

diodes were in the ON state (Inset of Figure 6B).

Furthermore, the bandwidth of the antenna increased

from 44.00 MHz to 48.40 MHz by ESS as superstrate

layer. These results confirm enhancement of the

antenna performance in the transmission states and

protection of antenna in case of HPM.

Table 1: Performances of the antennas with and without

superstrate for the diodes are in the ON or OFF states

Antenna

(dB)

Freq.

(GHz)

Efficiency

(%)

Gain

(dBi)

(MHz)

Reference

Antenna

-25.61 2.44 88.25 8.09 44.00

ntenna

with

Superstrate

(OFF State)

-22.28 2.46 79.23 8.26 48.40

Antenna

with

Superstrate

(ON State)

-4.13 2.46 30.84 2.04 -

4 CONCLUSIONS

We designed double-layer ESS structures was

motivated by two primary goals: enhancing the

antenna's gain in the presence of low-power

electromagnetic waves and ensuring its protection

against HPM or EMP attacks. The design of antenna

incorporates a rectangular patch with a line feed using

a Rogers RT5880 substrate for the 2.45 ISM band.

We placed the ESS layers with arrays above the

antenna as a superstrate layer. The results show that

ESS superstrate layers (diodes are in the OFF states)

can boost antenna gain up to 12.24 dBi in the

transmission band without change other antenna

parameters and shield antenna against HPM when the

diodes are in the ON state. Thus, the proposed ESS

structure serves as both a performance-enhancing

superstrate and a protective layer against high-power

electromagnetic threats.

(A)

(B)

Energy Selective Surface Superstrate on Antenna both Gain Enhancement and HPM Protection

179

ACKNOWLEDGEMENTS

Authors would like to thanks Kocaeli University BAP

Coordination Unit, project number FDK-2024-3576.

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