5G Networks Benefit from 3D Printed Multiple Input Multiple Output (MIMO) Antennas

As 3D printing continues to offer a host of benefits in the manufacturing of components like antennas, researchers Shaker Alkaraki and Yue Gao explore new applications, outlining their findings in the recently published ‘mm-Wave Low Cost MIMO Antennas with Beam Switching Capabilities Fabricated Using 3D Printing for 5G Communication Systems.’

One of the greatest advantages 3D printing and additive manufacturing processes offer is the potential to save exponentially on the bottom line in manufacturing certain parts—as well as being able to create them on demand and in many cases, much faster than by conventional methods. In this study, the authors investigate 3D printing of prototypes for multiple input multiple output (MIMO) antennas for 5G and millimeter-wave (mm-wave) applications.

With comprehensive standardization in place by 2020, 5G wireless technology for mobile technology is meant to expand in capacity enormously—by several hundred times over in comparison to previous processes, as it will be used over several frequency bands. So far, most countries have agreed with the proposal to use the following millimeter-wave (mm-wave) frequencies:

• 24 GHz to 29.5 GHz
• 37 GHz to 42.5 GHz
• 2 GHz to 48.2 GHz
• 64 to 71 GHz

Along with speed and affordability, 3D printing also allows the researchers to develop complex shapes; in this case, however, the process is more effective when used with new metallization techniques that are significantly lower in cost. In the MIMO system, multiple antennas are to be used, although there are challenges such as signal losses in higher atmospheres and high cost for system components.

“The attenuation of the signal at mm-wave mainly depends on the propagation distance, weather conditions and operating frequency,” stated the authors. “Shadowing is another important source of signal losses.”

The goal is to 3D print high-performance antennas that are steerable and more efficient but without the typically associated high expense.

The schematic of the proposed single element antenna. (a) Cross section of front view, (b) top view, (c) bottom view, and (d) perspective view.

The MIMO antenna prototypes developed for this study are:

• Compact in design, measuring 2×2 and 4×3
• More affordable
• More efficient
• Offers beam-switching abilities without phased array technology

The dimension of the proposed single element antenna

The schematic of proposed antenna with wall on its side. (a) Front view and (b) perspective view.

The antennas are comprised of two main parts:

• Feeding structure – microstrip made up of mini-smp ground plane/pad, vias and transmission line fabricated using RO4003C substrate with a dielectric constant of 3.38.
• Radiating structure – the 3D printed component, made up of a central slot surrounded by a rectangular cavity and two corrugations.

Creating both an asymmetric electric field and asymmetric surface current, one side of the antenna features a metallized wall. These elements steer the antenna beam, dependent on the wall height. The researchers note that ‘further increment within the wall height’ increases gain up to the point of saturation.

The relationship between wall height (𝑊ℎ), directivity and beam direction at 28 GHz. (𝜆 = 10.71 𝑚𝑚)

While the smaller antenna is made up of four elements providing radiation in the boresight direction, the larger prototype offers six elements just for providing radiation—and then another six for steering.

The effect of wall height (𝑤ℎ) on the radiation patterns of the antenna. (a) 2D radiation patterns of H-plane (y-z plane) for different wall height in 𝑚𝑚, (b) 3D radiation patterns of the antenna with no wall 𝑊ℎ = 0 𝑚𝑚, (c) 3D radiation pattern for 𝑊ℎ = 4.5 𝑚𝑚, (d) 𝑊ℎ = 11 𝑚𝑚 and (e) 𝑊ℎ =25 𝑚𝑚.

“The beam of the 4 × 3 MIMO is steered mechanically through introducing a metallic wall with different height on the side of the radiating single element structure. The sidewall creates asymmetric electric field on the surface of the antenna, which reflects the beam of the antenna to the opposite direction.

“The proposed sidewall is able to steer the beam of the MIMO up to 30° in the elevation plane. Finally, the performance of the proposed MIMO antennas are measured and found to operate as predicted by the numerical simulation tool,” concluded the authors.

3D printing is often a catalyst for greater innovation in creating parts like antennas, encouraging new concepts and expansion of traditional applications as researchers bring forth new projects featuring antennas for biomedical monitoring, polymer antennas for SAR systems, nanoantenna arrays, and more.

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