Theory of metascreen-based acoustic passive phased array

The metascreen-based acoustic passive phased array provides a. new degree of freedom for. manipulating. acoustic waves due to their fascinating properties, such as a. fully shifting phase, keeping impedance matching, and holding subwavelength spatial resolution. We develop acoustic theories to analyze the transmission/reflection spectra and the refracted pressure fields of a metascreen composed of elements with four Helmholtz resonators (HRs) in series and a straight pipe. We find that these properties. are also valid under oblique incidence with large angles, with the underlying physics stemming from the hybrid resonances between the HRs and the straight pipe. By imposing the. desired phase profiles, the refracted fields can be tailored in an. anomalous yet controllable manner. In particular, two types. of negative refraction. are exhibited,. based on two distinct mechanisms: one is formed from. classical diffraction theory and the other is dominated by the periodicity of the metascreen. Positive (normal) and negative refractions can be converted by simply changing the incident angle, with the coexistence of two types. of refraction. in a certain range of incident angles.