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Self-octuplexing substrate-integrated waveguide semi-elliptical-shaped slot antenna for multifunctional communication systems

Published online by Cambridge University Press:  27 March 2026

Swapnil Shekhar
Affiliation:
Department of Electrical Engineering, Indian Institute of Technology Delhi, New Delhi, India
Kundan Kumar*
Affiliation:
Department of Electronics and Communication Engineering, Dr. B. R. Ambedkar National Institute Technology, Jalandhar, India
Shruti Priya
Affiliation:
Department of Electronics Engineering, Indian Institute of Technology (ISM), Dhanbad, India
Nitesh Kashyap
Affiliation:
Department of Electronics and Communication Engineering, Dr. B. R. Ambedkar National Institute Technology, Jalandhar, India
Surinder Singh
Affiliation:
Department of Electronics and Communication Engineering, Sant Longowal Institute of Engineering and Technology, Sangrur, India
*
Corresponding author: Kundan Kumar; Email: kundansingh.singh5@gmail.com
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Abstract

This paper presents a novel self-octuplexing substrate-integrated waveguide (SIW) cavity-backed slot antenna for eight-band wireless communication services. This antenna employs eight semi-elliptical-shaped slots on an octagonal SIW cavity with different lengths to radiate at eight different frequencies. The eight radiating frequencies are 2.7, 3, 3.3, 3.6, 3.9, 4.2, 4.5, and 4.72 GHz, with impedance matching is less than −10 dB. Each radiator is backed by an eighth-mode SIW cavity and excited by a 50 Ω microstrip line. A designed prototype of the antenna is fabricated and tested. It has more than 34 dB measured isolation among any two ports. The maximum measured antenna gains are 4.4, 4.19, 4.11, 4.03, 4.19, 4.28, 5.2, and 5.44 dBi at the respective operating frequencies. It has a measured cross-polarization level of below −24.2 dB in the boresight direction and a front-to-back ratio of more than 10.4 dB in all the bands. All the slots can be tuned independently to radiate at the desired frequency band. This antenna can easily be integrated with other planar circuits due to an unperturbed ground plane.

Information

Type
Research Paper
Copyright
© The Author(s), 2026. Published by Cambridge University Press in association with The European Microwave Association.
Figure 0

Figure 1. (a) Schematic diagram and (b) exploded view of the proposed self-octuplexing antenna (S1 = 47.77, S2 = 42.74, S3 = 38.42, S4 = 34.74, S5 = 31.71, S6 = 29.29, S7 = 27.09, S8 = 25.37, a1 = 23.94, a2 = 21.64, a3 = 19.64, a4 = 17.94, a5 = 16.54, a6 = 15.34, a7 = 14.34, a8 = 13.64, b1 = 15.96, b2 = 14.2, b3 = 12.8, b4 = 11.6, b5 = 10.6, b6 = 10.2, b7 = 9.4, b8 = 8.4, k1 = 4.8, k2 = 3.7, k3 = 3.8, k4 = 3.8, k5 = 3.5, k6 = 3.2, k7 = 3, k8 = 3.2, p = 1.5, d = 1, wslot = 1.4, Gvia = 3, Gsloti = 1.94, winset = 0.7, wµsl = 2.2, LTOP = 14.74, LSUB = 41.37, RTOP = 43.23, and RSUB = 54.05; unit: mm).

Figure 1

Figure 2. Electric field distribution in SIW cavity in (a) fundamental mode, (b) one-eighth mode, (c) geometry of a single radiating element backed by OEMSIW cavity, and (d) one-eighth-mode radiator represented with electric wall and magnetic wall.

Figure 2

Figure 3. (a) Vector electric field distribution at 4.72 GHz for port 8 with a perfect electric and a perfect magnetic wall placed inside the OEMSIW cavity. (b) Reflection coefficient comparison when port 8 is excited.

Figure 3

Figure 4. Electric-field distributions when (a) port 1, (b) port 2, (c) port 3, (d) port 4, (e) port 5, (f) port 6, (g) port 7, and (h) port 8 are excited individually.

Figure 4

Figure 5. Vector electric-field distributions when (a) port 1, (b) port 2, (c) port 3, (d) port 4, (e) port 5, (f) port 6, (g) port 7, and (h) port 8 are excited individually.

Figure 5

Figure 6. Equivalent circuit of the proposed self-octuplexing antenna.

Figure 6

Table 1. Value of components of the circuit model

Figure 7

Figure 7. Reflection coefficient for EM and circuit simulation of the proposed antenna.

Figure 8

Figure 8. Isolation for (a)–(d) EM simulation and (e)–(h) circuit simulation of the proposed antenna.

Figure 9

Figure 9. Variation in reflection coefficient with Gslot1 keeping other dimensions constant (a) port 1, (b) magnified view of frequency variation.

Figure 10

Figure 10. Reflection coefficient for different values of RTOP.

Figure 11

Figure 11. Isolation for different values of RTOP.

Figure 12

Figure 12. Fabricated antenna structure (a) top view, (b) ground plane view, (c) diagram of measurement setup, and (d) measurement setup in anechoic chamber.

Figure 13

Figure 13. Simulated and measured (a) reflection coefficient and (b) gain and efficiency.

Figure 14

Figure 14. Simulated and measured isolation for the proposed antenna.

Figure 15

Figure 15. Simulated and measured radiation pattern at (a) 2.7 GHz, (b) 3.0 GHz, (c) 3.3 GHz, (d) 3.6 GHz, (e) 3.9 GHz, (f) 4.2 GHz, (g) 4.5 GHz, and (h) 4.72 GHz.

Figure 16

Table 2. Measured antenna parameters

Figure 17

Table 3. Comparison of the proposed self-octuplexing antenna with previous SIW antenna designs