Studying the electromagnetic compatibility of an Unmanned Aerial Vehicle (UAV) using full-wave electromagnetic simulations is computationally challenging. A UAV can exhibit unintentional coupling from far-field sources as well as from sources in its close vicinity. For example, in many applications, the UAV carries a payload that consists of a transmitting antenna to communicate/characterize receivers on the ground. Therefore, there is a strong need for an accurate and rapid technique to quantify RF coupling to the UAV subcomponents due to a wide range of incident electromagnetic radiation. In this work, we study RF coupling to a quadcopter UAV in a computationally efficient manner using the Equivalent Circuit Approach (ECA). The ECA is based on modeling the direct coupling to the wiring system with a Thevenin equivalent circuit terminated with the load under test. We study different circuit representations for this Thevenin equivalent circuit and show the advantages of each representation. Moreover, the equivalent circuit of the UAV wires is used to study different linear/nonlinear loads in a fraction of the time required by full-wave simulations. In addition, we show how the ECA provides physical insight that can facilitate the prediction of RF coupling to a UAV and other complex systems.

In this work, we study the current coupled to a simplified Unmanned Aerial Vehicle (UAV) model using a dual computational and experimental approach. The simplified surrogate structure reduced the computational burden and facilitated the experimental measurement of the coupled currents. For a practical system, a wide range of simulations and measurements must be performed to analyze the induced current variations with respect to properties of the incident excitation waveform, such as the frequency, angle of incidence, and polarization. To simplify this analysis, Characteristic Mode Analysis (CMA) was used to compute the eigen-currents of the UAV model and predict where and under which RF excitation conditions the coupled current is maximized. We verified these predictions using direct experimental measurement of the coupled currents. The presented simulations and measurements show the usefulness of CMA for studying electromagnetic coupling to practical systems.

A swarm of unmanned aerial vehicles (UAVs) often rely on exceptional wireless coverage of embedded or flush-mounted antennas or arrays, especially in long-range communication. While arrays offer significant range and beam steerability control, they often suffer from size, weight, and power (SWaP) limitations. On the other hand, achieving a wideband, high-gain, and beam-steerable response from a single antenna is highly desired for its compact SWaP characteristics. In this study, a cube-shaped cavity antenna excited by a monopole feed is designed, fabricated, and measured. The proposed antenna operates from 4.1 to 5.56 GHz with a 30.22% fractional bandwidth and a peak gain of 8 dBi. In addition, a frequency-selective surface (FSS) is developed to replace the metallic faces of the cavity, enabling 360° electronic beam steerability. Thermal analysis of the FSS-based cavity design is conducted to determine its maximum power handling capability, revealing a maximum power handling capability of 1.3 KW continuous. In addition, the maximum rating currents of the FSS diodes can be reached only at 165 W, limiting the maximum power handling to only 165 W in the case of using the diodes used in this analysis. The antenna prototype is successfully fabricated, and the radiation pattern is experimentally measured, showing a strong agreement between the simulated and measured results. The electronic steerability of the proposed antenna indicates its suitability for 5G new radio and UAV applications.

This article is intentionally generated by an artificial intelligence (AI) system and is framed as a practical stress test: can modern AI reliably draft an engineering tutorial/review on a technically nuanced topic without inventing citations and without producing internally inconsistent technical explanations? The technical topic selected for this test and reported here is the applications of CMA for designing metasurface. Specifically, CMA provides an eigenmode-based decomposition of currents and fields that can expose the dominant mechanisms governing metasurface antennas and related engineered surfaces. This tutorial-style review synthesizes CMA formulations relevant to metasurfaces spanning finite apertures and periodic frequency-selective surfaces, and maps commonly reported modal quantities (eigenvalues, modal significance, characteristic angle, and excitation-dependent modal weights) to practical design tasks such as bandwidth enhancement, mode suppression, polarization conversion, and reconfigurable phase control. Practical guidance is provided on mode tracking, normalization conventions, and validation against full-wave simulations or measurements, with the aim of improving transparency and reproducibility in CMA-guided metasurface studies. As this manuscript was drafted with AI assistance, we additionally report an explicit citation-verification and self-consistency audit to illustrate a concrete workflow for maintaining scientific reliability in AI-assisted technical writing. This manuscript is intentionally positioned as a tutorial/review and an AI-audit case study rather than as a primary research paper; accordingly, the figures are illustrative schematics and synthetic plots used to explain modal reasoning, not to report new electromagnetic simulations or measurements.

In this work, we study the current coupled to a simplified Unmanned Aerial Vehicle (UAV) model using a dual computational and experimental approach. The surrogate structure reduced the computational burden and facilitated the experimental measurement of the coupled currents. For a practical system, a wide range of simulations and measurements must be performed to analyze the induced current variations with respect to the incident excitation properties such as the frequency, angle of incidence, and polarization. To simplify this analysis, Characteristic Mode Analysis (CMA) was used to compute the eigen-currents of the UAV model and predict where and under which RF excitation conditions, the coupled current is maximized. We verified these predictions using direct experimental measurement of the coupled currents. The presented simulations and measurements show the usefulness of CMA for studying electromagnetic coupling to practical systems.