Home appliances generally comprise a mechanical envelope, or enclosure, of electrically conductive material (steel, aluminum, etc.) that houses electrical and electronic circuits. That envelope typically includes all kind of apertures, openings, holes, slots, windows, etc., to connect—physically and electromagnetically—the external space with its internal space. The performance of that envelope is a key element to comply with surface current EMI/EMC (Electro-Magnetic Interference/Electro-Magnetic Compatibility) regulations for electromagnetic interference, both emissions and immunity. Here, we present a novel theoretical proposal that consists of establishing the mathematical relationship of the coupling between the resonant modes of an internal cavity (RMs) contained in a conductive body and the characteristic modes (CMs) on the external surface of its envelope through the openings that connect those external and internal spaces, and doing so by means of equivalent virtual surface currents located in those openings. The comparative results of simulations and actual measurements of immunity in an anechoic chamber (measurements originally oriented to other purposes) are presented as above-mentioned evidence of resonating modes coupling on the frequency range 40–1000 MHz. However, this theoretical proposal is novel and remains to be developed in greater depth and detail in future works.

This paper proposes a reconstruction framework for estimating the far-field (FF) radiation patterns of large, heavy, or non-rotatable wireless-enabled systems. The method combines a tilted orbital sampling (ToS) strategy with sparse spherical harmonic (SH) expansion, compressed sensing (CS), and convex optimization (CO), thereby linking a mechanically constrained acquisition scheme with a mathematically efficient recovery process. The purpose of this integration is not only to reduce the number of measurements but also to retrieve the radiation information most relevant to Internet of Things (IoT) devices and bulky equipment that cannot be easily rotated within anechoic chambers. The framework is validated on two representative cases: a canonical half-wave dipole and a commercial Wi-Fi-enabled device. In the latter and more challenging case, accurate reconstruction is achieved with fewer than 30 SH coefficients and using less than 20% of the measurements required by a conventional full-sphere scan, with the normalized root-mean-square error remaining below 5%. Although inaccessible angular regions may be partially uncharacterized, such directions are of minor relevance for the intended operational coverage. The resulting SH-based representation can be seamlessly integrated into ray-tracing propagation simulators and electromagnetic optimization workflows, enabling efficient and application-oriented OTA characterization under realistic chamber constraints.