Citation: Jiménez, D.A.; Reyna, A.; Balderas, L.I.; Panduro, M.A. Design of 4 × 4 Low-Profile Antenna Array for CubeSat Applications. Micromachines 2023, 14, 180. https://doi.org/10.3390/ mi14010180 Academic Editor: Nikola Basta and Milka Potrebic Received: 19 December 2022 Revised: 2 January 2023 Accepted: 9 January 2023 Published: 10 January 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). micromachines Article Design of 4 × 4 Low-Profile Antenna Array for CubeSat Applications Diana Alondra Jiménez 1 , Alberto Reyna 1, * , Luz Idalia Balderas 1 and Marco Antonio Panduro 2 1 Electrical and Electronic Engineering Department, University Autonomous of Tamaulipas, UAMRR, Reynosa 88779, Mexico 2 Electronics and Telecommunications Department, CICESE Research Center, Ensenada 22860, Mexico * Correspondence: alberto.reyna@docentes.uat.edu.mx Abstract: This paper presents a low-profile microstrip antenna with high gain for fifth-generation (5G) CubeSat applications. The proposed design consists of 16 miniaturized patch antennas distributed in a uniform 4 × 4 topology with a feeding network on Rogers TMM10 substrate. The antenna array was simulated in CST Studio Suite ® software and fabricated for performance testing on the CubeSat structure. The prototype works perfectly from 3.46 GHz to 3.54 GHz. The simulated and measurement results reveal remarkable performance. The design obtained a measured gain of 8.03 dBi and a reflection coefficient of −17.4 dB at the center frequency of 3.5 GHz. Due to its reduced dimensions of 10 × 10 cm, this design is an excellent alternative for mounting on a CubeSat structure as it combines efficient performance with a low profile. Keywords: antenna array; CubeSat; fifth generation (5G); high gain; miniaturization; nanosatellite 1. Introduction Given the demand for increasingly efficient global communication with great coverage and a long range, the development of low earth orbit (LEO), medium earth orbit (MEO), geostationary earth orbit (GEO), and high-altitude platform station (HAPS) satellite systems is required [1,2]. In the last two decades, the development of these telecommunications satellite systems has experienced a great boom, since it has evolved beyond the use of large satellites to include the design, manufacture, and launch of new projects of smaller size and cost. In this sense, nanosatellites, whose mass is between 1 and 10 kg, stand out [3]. A CubeSat is a standardized form of this type of satellite. In 1999 its standard [4] was created, thus initiating a new era in satellite design. Currently, revision number 14 is available, where a standard CubeSat unit or “1U” is defined as a cube-shaped structure with a restricted volume of 10 cm × 10 cm × 10 cm and a mass of up to 1.33 kg [5]. A key component of the CubeSat communication system is the antenna. This device is used to send data from the nanosatellite to the ground station and to receive commands from it. However, its design is very challenging, as it must meet the size and mass restrictions of the CubeSat standard while offering high gain. On the other hand, frequency is also a key parameter to be considered. In this case, with the publication of new specifications for 5G mobile technologies, and with the conclusion of the first complete set of standards, a new area of technological development opportunity has been opened for nanosatellites that operate in their frequency bands. Since Release 15 of 3GPP (3rd Generation Partnership Project), the radio frequency range from 3.3 GHz to 4.2 GHz was enabled as a new band for 5G [6]. This frequency band is suitable for providing narrowband IoT services with low-orbit nanosatellites as mentioned in Release 17 for Narrow Band IoT/extended Machine Type Communication standards [7]. In this sense, the modern antenna design trends for nanosatellites consider the aspects of low-profile, high-gain, and 5G frequency ranges as mentioned in [8]. Micromachines 2023, 14, 180. https://doi.org/10.3390/mi14010180 https://www.mdpi.com/journal/micromachines