High efficient electro-acoustic convolvers

Elastic convolvers are very important for signal-processing devices of the spread spectrum communication systems. The more efficient convolvers are required for the application in the spread spectrum and next stage communication systems. The efficiency of electro-acoustic convolvers depends on the sheet conductivity and thickness of the thin film semiconductor. Generally, the sheet conductivity is larger and the thickness of the film is thinner for optimum efficiency. In this paper, monolithic planner type of the convolver utilizing a strip coupler to couple a piezoelectric material and semiconductor is described. The 128°Y-X LiNbO₃ and InSb thin film semiconductor are put together using the MBE. The strip electrodes are fabricated on the LiNbO ₃ and InSb substrates using lithography process. The gaps between the coupler electrodes and InSb are very small. Therefore the high efficient and high frequency convolvers by using a longitudinal coupling are obtained. The experimental result shows the F-value of about -35 dB at 100 MHz