A wave physics approach to electronically steerable antennas

Electronically steerable antennas (ESAs) are compact, thin, and light antennas. ESAs are being more and more used for Satcom applications thanks to the rapid development of mega-constellations and the advent of 5G with mmWave. However, many limitations still exist in the current designs. Indeed, all designs up to date rely on the same old concept of phased arrays, which are composed of many sources phased matched to point in different directions. These arrays can be passive, in the sense that a common feed is used to radiate through many radiators, or active in which case each tiny emitter contains its own source of waves. The formers are poorly efficient because they are very dissipative but relatively simple and low-energy greedy. On the other hand, the latter provide good performances but they are extremely costly and use huge amounts of electrical power to operate. Additionally, a significant amount of power is lost as dissipation. Finally, both active and passive phased arrays have tremendous problems that need to be overcome before they are vastly used. Here we introduce the concept of leaky reconfigurable cavity antenna, which stems from a fundamentally different unique approach to beamforming. It makes use of a thin leaky cavity that, when excited by single or several feeds, can create any desired wavefield and consequently any desired radiation pattern. To achieve this desired radiation pattern, the cavity is reconfigured in real-time by electronically reconfigurable metasurfaces (MMs). The MM controls the reflections of the waves inside the cavity, acting as a software-controlled set of boundary conditions. Being based on discrete components, the antenna maintains the cost-efficiency, robustness, and power sobriety of the simplest passive phased arrays, with a power needed for beamforming as low as a few tens of watts at K
u
or K
a
. Furthermore, since the control is solely based on electronics, it achieves the performances of active phased arrays at the same time, for instance in terms of gain or switching speeds. With its high performance and low complexity, our concept paves the way for the deployment of electronically steerable antennas at scale. In conclusion, since the beamforming does not result from the synchronization of many elementary sources, but rather from the shaping of a wavefield inside a cavity, our concept is standard or protocol agnostic, it can support multiple frequency bands, and emit multiple beams, at different frequencies, with different polarizations and an optimal scan loss.