Circulators and isolators are commonly established in electromagnetics, from radio-waves to optics, but a similar functionality is not available for sound. This implies that sonars or ultrasound devices cannot rely on the same aperture to transmit and receive at the same time and the same frequency, leading to more complex and bulky systems. The reason for these limitations is the weak magnetic effects on sound waves. With the acoustic circulator, Silicon Audio uses mechanical motion or time modulation to realize large isolation and circulation in a compact, linear component.
The first prototype of the acoustic circulator was based on a circular cavity loaded with CPU fans that circulated the air in the cavity at the required speed to realize large isolation and circulation in a deeply subwavelength component. This configuration supported re-routing of audible waves with over 40 dB measured isolation between ports. While still in the research phase, this work has the potential for future translation on chip using MEMS technology and eventual replacement of the mechanical motion with time modulation for a variety of acoustic applications.
Silicon Audio’s prototype reported unprecedented isolation levels for a compact acoustic device, as seen in the Isolation v Input current chart. In addition, the device is purely linear, and does not introduce any distortion to the applied signal.
Silicon Audio’s extensive acoustics experience is deployed in the development of the acoustic circulator for various applications and frequency ranges.Our ACOUSTICS experience…
The functionality of Silicon Audio’s circulators is inspired by our research on metamaterials and specifically the magnetic bias on a ferromagnetic molecule, which is mimicked by the mechanical motion of the medium in the acoustic circulator.