Performance evaluation and validation of a quad-element super-wideband fractal MIMO antenna with integrated quad-band filtering capability for advanced 5G/IoT systems

Why this tiny pattern matters for wireless life

Our homes, offices, and cities are filling up with wirelessly connected gadgets, from phones and laptops to sensors, cameras, cars, and factory robots. All of them compete for space in the airwaves. This paper presents a new kind of compact antenna that can talk across a very wide range of frequencies, as needed for advanced 5G and Internet of Things (IoT) systems, while smartly ignoring four especially noisy bands that belong to powerful satellite and radar services. That combination—tiny size, huge bandwidth, and built‑in "deaf spots"—aims to make future devices faster, more reliable, and less vulnerable to interference.

A small board with big listening power

The heart of the work is a four‑element antenna array, roughly the size of a couple of postage stamps, built on a low‑cost fiberglass circuit board (FR4). Each element is a hexagon of copper that serves as a miniature radio window. Working together, the four elements form what engineers call a MIMO (multiple‑input multiple‑output) antenna, which can send and receive several signals at once. The array covers an unusually broad "super‑wideband" span from about 2.4 to 25 gigahertz—more than a decade of frequency—embracing bands used by 5G, Wi‑Fi, short‑range radar, and many IoT applications. This broad reach allows a single, compact module to replace several separate antennas in a phone, sensor node, or other portable gadget.

Fractal cuts that shrink and sharpen

To squeeze so much performance into such a small footprint, the authors carve a windmill‑like fractal pattern into each hexagonal patch. A fractal is a repeated geometric motif that creates a long, folded path inside a small area. Here, the pattern is built in steps, starting from a simple triangle and adding smaller copies around it, forming clusters of diamond shapes. These recurring cuts lengthen the effective electrical path without enlarging the metal patch, reducing its area by about half compared with a solid hexagon. As the iterations are added, the antenna’s operating band expands and shifts downward in frequency, enabling the broad 2.4–25 GHz coverage while keeping the overall device compact enough for handheld hardware.

Quieting the loud neighbors in the airwaves

Wideband listening brings a drawback: the antenna can also pick up very strong, narrowband signals from satellite and radar services that share parts of the spectrum. These signals can overwhelm receivers designed for low‑power consumer links. To tackle this, the designers build four tunable "notch" structures right into each antenna element. Two L‑shaped slits cut into the ground plane knock out specific satellite downlink bands. A pair of tiny rectangular ring shapes near the feed line blocks a slice of radar spectrum, while a related ring etched into the ground cancels a satellite uplink band. Each notch is sized so that at its target frequency, incoming energy circulates locally instead of radiating, creating a deep dip in sensitivity only at that band, while leaving the rest of the super‑wideband range available for useful signals.

Keeping four ears from listening to each other

Because the array has four active elements packed closely together, there is a risk they will strongly "hear" one another instead of the outside world, spoiling the diversity that MIMO relies on. The authors reduce this unwanted coupling in two ways. First, they optimize the spacing between the hexagonal patches. Second, they reshape the shared metal ground on the back of the board, adding slots and a slim vertical strip that carries a central hexagonal ring. This structure guides currents so that energy leaking from one element is largely blocked before it disturbs its neighbors. Laboratory measurements show that energy transfer between ports stays well below typical limits across the full band, and statistical measures of diversity indicate that the four elements deliver mostly independent views of the wireless channel, even in echo‑rich environments.

From simulation to real‑world 5G and IoT

The team built and tested physical prototypes, comparing computer predictions with measurements of reflection, coupling, radiation patterns, and signal gain. Despite small differences caused by fabrication tolerances and connectors, the results match closely: the array covers nearly the entire intended super‑wideband range, shows clear notches at the four protected services, and maintains stable, directional radiation suited to high‑data‑rate links. Diversity metrics confirm that the design can improve signal‑to‑noise ratio without extra transmit power. In simple terms, this work demonstrates a low‑cost, compact antenna module that can support many of the bands used by future 5G and IoT devices while automatically steering clear of a few especially noisy neighbors in the spectrum, making wireless communication both faster and more reliable.

Citation: Sohi, A.K., Kumar, G.N., Singh, A.K. et al. Performance evaluation and validation of a quad-element super-wideband fractal MIMO antenna with integrated quad-band filtering capability for advanced 5G/IoT systems. Sci Rep 16, 13778 (2026). https://doi.org/10.1038/s41598-025-33801-1

Keywords: 5G antennas, MIMO, super wideband, fractal design, interference filtering