THE ELECTROSTATIC PROBLEM FOR THE SAW INTERDIGITAL TRANSDUCERS IN AN EXTERNAL ELECTRIC-FIELD .1. A GENERAL-SOLUTION FOR A LIMITED NUMBER OFELECTRODES

An exact solution for finding the surface charge and electric field di stributions in interdigital transducers (IDT's) with a limited number N of electrodes is given. It is based on the Keldysh-Sedov solution to the mixed boundary problem of the analytic function theory, The IDT e lectrodes are placed on the plane boundary between two anisotropic die lectric media, The external electric field may arbitrarily vary along the structure. The solution contains N constants which may be found fr om the electrodes' connection conditions, For determining these consta nts a linear set of algebraic equations is obtained, The coefficients of this system are written in explicit form, The capacitance coefficie nts for a system of electrodes of different widths are obtained, For i llustration purposes systems with one and two electrodes are considere d in greater detail. In these cases the external electric field is ass umed to vary harmonically along the structure with an arbitrary wavenu mber, For one electrode the Fourier transform of the charge distributi on is obtained in terms of the Bessel functions. For two electrodes of different widths a simple expression for the capacitance is found, Th e charge and electric field distributions are represented graphically for several wavenumbers and geometrical sizes of the electrode system. Section I contains a survey, including Russian literature, which is n ot well known in the west.