Improved depthfinder display presentation by use of MSI: Brede, R. Electroteknisk Tidsskrift Vol 84 No 20 (November 1971) pp 19–20 (In Norwegian)

Abstract

This chapter focuses on real-time SAW convolvers for programmable matched filtering, such as in spread-spectrum communications. This chapter examines three types of real-time convolvers. The first of these is the three-port monolithic waveguide SAW convolver, whose operation is based on acoustic interactions on the surface of the piezoelectric substrate. This type is currently leading the three-port SAW convolver field in applications calling for bandwidths of 100 megahertz or less. The other two real-time SAW convolvers incorporate a silicon semiconductor in close proximity to a lithium niobate substrate such that their operation is dependent on the acoustoelectric interactions of SAW-induced electric fields at the silicon surface. In the order of evolution, these last two are the three-port SAW/ silicon convolver and the more intricate four-port SAW/silicon convolver. This four-port structure finds application in wide-band radar and spread-spectrum communications, such as for packet radio applications. The choice of whether to use a SAW convolver or a linear SAW filter for matched filtering depends on a number of factors. On the credit side, the SAW convolver can provide for a fixed or programmable matched filtering of lengthy coded sequences, well beyond the present range of fixed or programmable transversal SAW filters.