High-sensitive vector visualization of nonlinear harmonic responses generated in RF-SAW devices

This paper describes a high-sensitive 2D vector visualization of the second-order harmonic (H2) distribution on RF-SAW devices. Based on the Sagnac interferometer as a probe for acoustic vibrations on the SAW device surface, the visualization system was tuned to pick up not only linear responses but also weaker H2 responses. Since the system captures amplitude and phase information, we can manipulate them, i.e., extracting the specific modes in the wave number domain via the FFT/IFFT, estimating the group delay at points by points, etc. As demonstrations, the linear and the H2 responses on the one-port SAW resonator of the resonant frequency of 923.0 MHz were visualized. The driving frequency was swept from 922.0 to 950.0 every 0.5 [MHz], then the H2 responses are shown as animations. Furthermore, the advantages of capturing phase information are shown. The proposed system is helpful for nonlinearity in RF SAW devices.