Wave Apodization to Suppress Transverse Modes and Third-order Intermodulation Distortion in POI-SAW Resonators

The growing complexity of RF front-ends in modern mobile communications has put tremendous pressure on improving the performance of SAW devices. Wave apodization of the interdigital transducer (IDT) is a widely used technique for improved linear in SAW devices. However, its influence on device nonlinearity remains unclear. This work investigates the influence of the interdigital transducer (IDT) design on linear and nonlinear performance of the piezoelectric on insulator surface acoustic wave (POI-SAW) resonator on 30° YX-LiNbO3/SiO2/poly-Si/Si substrate. The POI-SAW resonators on 30° YX-LiNbO3/SiO2/poly-Si/Si substrate with normal IDT and wave apodization IDT are designed and fabricated. Then their linear and nonlinear responses are measured and analyzed, respectively. Measurement results demonstrate that the apodization design effectively suppresses the transverse mode response, while also reducing the third-order intermodulation distortion (IMD3) to a level of -15 dBm. Compared to normal IDT designs, wave apodization IDT is proved to be of obvious advantage in suppression of both transverse modes and third-order intermodulation distortion (IMD3).