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Development and Assessment of Flexible Uniplanar SSPP-Based Endfire MIMO Antenna for B5G Radio Stripe Network Applications

Year: 2025

Type: article

Abstract: An effective way to implement cell-free massive multiple-input-multiple-output (CF-mMIMO) networks is through the radio stripe network (RSN) concept, in which all access points (APs)-containing antennas and signal processing units required to serve user equipment (UE)-share a common stripe that can be easily deployed over existing infrastructures. This article proposes, for the first time, a MIMO antenna that satisfies all RSN application requirements, such as a flexible and ultra-thin profile, extremely low volume, and an endfire beam with a downward tilt to cover UEs located beneath the deployed stripes. A spoof surface plasmon polariton (SSPP)based structure is implemented on a flexible substrate to achieve this design. The SSPP transmission line (TL) employs U-shaped unit cells. An equivalent circuit model is presented to analyze how design parameters affect the dispersion characteristics. A single metal-layered, hook-shaped open-ended SSPP TL enables a 45 • downward-tilted endfire radiation beam. Equivalent circuit models are also used to illustrate the antenna design evolution. A filtering mechanism is employed on the coplanar waveguide-to-SSPP transition to eliminate higher-order modes. An SSPP-based director is shared between two orthogonally arranged hookshaped antenna elements to improve directivity. The fabricated prototype is tested on both flat and curved surfaces (wood and brick) for validation. The MIMO antenna achieves a maximum gain of 7.4 dBi, an impedance bandwidth of 42.2%, isolation up to 26.7 dB, and an envelope correlation coefficient below 0.19. Owing to its ultra-thin flexible profile, tilted beam, and wideband performance, the proposed antenna is highly suitable for beyond fifth-generation RSN applications.

Source: IEEE Journal on Flexible Electronics

DOI: 10.1109/jflex.2025.3578588

Authors: Abhishek Maganbhai Sonagara, Mohit Mishra, Rakhesh Singh Kshetrimayum, Emil Björnson, Zhi Ning Chen

Institutions: Indian Institute of Technology Guwahati, National University of Singapore, Temasek Laboratories, KTH Royal Institute of Technology

Language: English

Topic: Antenna Design and Analysis

Subfield: Aerospace Engineering

Field: Engineering

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $2,645

Funder: Science and Engineering Research Board