A surface acoustic wave elastic convolver using a KNbO3 single crystal substrate

Elastic convolvers are very important in signal processing devices of spread spectrum communication (SSC) systems. Highly efficient convolvers are required in the application of the spread spectrum and next stage communication systems. A high value of the coupling coefficient is very important for wideband and high efficiency surface acoustic wave (SAW) devices, such as SAW convolvers. Potassium niobate (KNbO3) has large piezoelectric constants;Ind a very large electromechanical coupling coefficient (K-2) Df 0.53 for surface acoustic waves, which is about 10 times higher than that of LiNbO3. Therefore, highly efficient elastic SAW convolvers using KNbO3 substrates are expected in the future. In this paper, the use of the rotated 60 degrees Y-cut, X-propagating KNbO3 substrates in convolvers is demonstrated. The experimental results show that the efficiency of the convolver using 60 degrees Y-X KNbO3 is 15 dB higher than that of the convolver using Y-Z LiNbO3.