Monolithic elastic convolver output circuit

Abstract

The disclosure relates to a microstrip circuit which is used to combine the energy output from the convolving plate of a surface acoustic wave (SAW) monolithic elastic convolver. The convolving plate is tapped at its two ends and a Wilkinson combiner is used to sum the signals that propagate to the ends of the plate. The Wilkinson combiner is a three-port device with the two arms that couple to the convolver plate having their characteristic impedances set to match that of the acoustic waveguide. In view of the impedance match, no electromagnetic reflections are produced at the end of the convolving plate and all of the energy incident on the Wilkinson combiner is summed and delivered to the output port of the combiner. Additionally, the microstrip circuit has an impedance transformer to transform down to an impedance suitable for driving an output amplifier chain of a receiving system. In accordance with a second embodiment of the invention, a plurality of convolvers is connected together in a Christmas tree-type of arrangement to maintain spatial amplitude uniformity while minimizing the phase delay that occurs from propagation from the center of the elastic convolver to the outer extremes thereof. In accordance with a third embodiment of the invention, the Wilkinson convolvers of FIG. 2 are replaced by microstrips configured to sum the outputs from all of the convolver sections without reflections. This embodiment provides an impedance matched to the driving segments of the convolving plate and produces broad band power combining internal to the microstrip of the output circuit. This embodiment eliminates potential losses within the microstrip circuit from power dissipation in lumped resistors inherent in the Wilkinson embodiment.