JPS5687909A - Electromechanical converter for elastic surface wave filter - Google Patents

Abstract

PURPOSE:To enable to make easy the matching with external circuits and to increase the frequency characteristics, by using electrode groups providing float electrodes in which the cross finger length is the same and which are not connected to any part between the electrodes at 0 deg. and 90 deg. sides with equal cross finger length. CONSTITUTION:An output side electrode group 13 forms a float electrode 13d, by cutting off a pair of positive and negative or several pairs of electrode at 0 deg. and 90 deg. side electrodes of each group from the positive and negative electrodes and connecting the ends, and this electrode 13d is suitably located in each group to change the exciting strength. When a reference signal is fed to a 0 deg. side electrode 13a and implusive voltage different from the phase by 90 deg. is fed to a 90 deg. side electrode 13b, the electric field between the electrodes 13a and 13b clipping the electrode 13d is small, the stress produced is 1/3 in comparison with the absence of the electrode 13d and the component of the electrode 13a is also 1/2. This is also the same for the electrode 13b, and the electrode of one group at the output side electrode 13 have the exciting intensity of 1/2, allowing to have weight toward axial direction. Specified frequency characteristics can be obtained by changing the combination of the location of the elecdrodes 13.