Arrays trilogy: adaptive-parametric-synthetic

Beyond the "diffraction limit" inherited from optics, that is now described as "Woodward's theorem", three kinds of antennas have demonstrated that this divine law may be bypassed. They have opened new fields for antennas. Within the framework of decision theory, adaptive array questions the pertinence of this limit as a measurement of the antenna's spatial resolution. This "cultural revolution" rejuvenated the landscape of antenna processing, its vocabulary (array manifold, spatial filtering, matched field, spatial coherence, etc.), its processing (SLC, MUSIC, ESPRIT, etc.) and its applications in a wide range of domains (telecom, sonar, radar, and medical ultrasound). Parametric array, while specific to the acoustic world, allows us to build very large-bandwidth transmit arrays, which are highly directive at low frequencies. They are a result of research on models in non-linear acoustics and are used in the underwater world (acoustic communication links, sounders, etc.) or in the air (sound projectors). Synthetic arrays take advantage of the physical array's movement to generate a large aperture, coherently combining successive receptions. Multiple applications include radar or sonar mapping, medical ultrasound, seismology, and even radio astronomy.