Miniaturized Anechoic Chamber Constructed Based on an Inhomogeneous PML Model

In electromagnetics, anechoic chambers are used to obtain artificial analogs of free space. Such chambers are electrically large due to the inherent angle-dependent nature of absorbing materials. Existing models of perfectly matched layer (PML) imply that angle-independent reflectionless absorptions can hardly be achieved without involving gain media. In this paper, we mathematically derived an unconventional PML model, based on which the angle-dependent nature of absorbing materials can be manipulated to construct electrically small anechoic chambers. As an example, a semiclosed cylindrical chamber was experimentally implemented with an inhomogeneous artificial surface as thin as 0.012 wavelength. The inner diameter of this chamber is six wavelengths. The spatial voltage standing wave ratio (VSWR) experimentally measured inside this chamber complies with the theoretical analysis and full-wave simulation. With the aid of the dielectric 3-D printing technology, high-performance, microsized anechoic chambers can be constructed for scientific research and technology development in the future.