Acoustic Add-Drop filter involving a ring resonator based on a One-Dimensional surface phononic crystal

By employing two parallel one-dimensional surface phononic crystals for spoof surface acoustic waves and a circular ring resonator, an acoustic add-drop filter is numerically designed and its operation in the air environment is both numerically and experimentally investigated. Finite Element Method is used for band structure calculations and frequency domain simulations of filter operation. For frequencies around 40 kHz, a surface band is observed when a one-dimensional array of cylindrical cavities with a period of 2.7 mm, whose radius is 1.1 mm are embedded in the solid surface by 30% of the radius from their center. When a surface phononic crystal is close to a circular ring resonator containing 100 cavities in total with a radius of 42.9 mm, at a distance of 1.5 periods, frequency-domain Finite-Element simulations at 41.528 kHz reveal that drop port output maximum is observed, whereas through and add outputs are minimum. The corresponding drop port transmission peak has a width and quality factor of 25 Hz and 1661, respectively. In addition, the contrast ratio between the drop and through port outputs at the peak frequency is calculated as 0.77. Experimentally obtained port output data are in agreement with numerical results. The proposed acoustic add-drop filter can be used in areas such as ultrasonic sensors, acoustic signal processing and acoustic logic.