Unidirectional dispersive transducers and applications to efficient elastic convolver

Elastic convolvers an very important for signal-processing devices of the spread spectrum communication systems. We have already fabricated a dispersive IDT with down-chirp directivity on the Y cut-Z propagation LiNbO/sub 3/ and we fabricated a convolver using this IDT and dispersive split IDT with bi-directionality. An dispersive electrode IDT with an up-chirp directivity has not been obtained. We now propose a dispersive split IDT with an up-chirp directivity using Al/Cr bimetal electrode on Y-Z LiNbO/sub 3/ substrate. We have successfully fabricated the required IDT using an electro-chemical effect. Furthermore, we also obtained the elastic convolver using this IDT with a high efficiency of -56.5 dBm and low-insertion loss of 11.9 dB at a center describe frequency of 200 MHz.