US 4,162,415 AGranted

Acoustic surface wave transducer and filter built around this transducer

AssigneeInstitut Radiotekhniki i Elektroniki Akademii Nauk SSSR

InventorsAnatoly S. Andreev, Alexandr S. Bagdasarian, Jury V. Gulyaev, Anatoly M. Kmita

Life of this patent

Estimating the term…

Loading patent…

Abstract

An acoustic surface wave interdigital transducer comprises a main and auxiliary rows of electrodes arranged on a piezoelectric substrate. The main row of electrodes comprises a first group of electrodes galvanically connected to a first contact area and a second group of electrodes parallel to the electrodes of the first group and disposed therebetween so that there are formed overlapping portions having the same length. The auxiliary row of electrodes comprises a third group of electrodes galvanically coupled to the second contact area and a fourth group of electrodes parallel to the electrodes of the third group connected directly to the corresponding electrodes of the second group of the main row and disposed between the electrodes of the third group so as to form overlapping portions of electrodes of both groups, said portions having a variable length. The electrodes of the second group of the main row are connected to the second contact area through capacitances. The distances between the longitudinal axes of the adjacent electrodes of the third and fourth groups of the auxiliary row differ from the distances between the longitudinal axes of the electrodes of the first and second groups of the main row. An acoustic surface wave filter built around the above described acoustic surface wave transducer.

Claims17

Dependent claims

An acoustic surface wave interdigital transducer comprising:

a piezoelectric substrate;
a first contact area arranged on said piezoelectric substrate;
a second contact area arranged on said piezoelectric substrate;
a main row of electrodes having longitudinal axes, said row being arranged on said piezoelectric substrate and having a first group of said electrodes electrically connected to said first contact area and a second group of said electrodes in parallel to said electrodes of the first group and disposed therebetween so that overlapping portions of said electrodes of the same length are formed;
a first auxiliary row of electrodes, having longitudinal axes, arranged on said piezoelectric substrate between the main row of said electrodes and the second contact area;
the first auxiliary row of said electrodes including a third group of said electrodes galvanically coupled to the second contact area, and a fourth group of said electrodes parallel to said electrodes of the third group connected directly to the corresponding electrodes of the second group of the main row and arranged between said electrodes of the third group so that at least a part of these have, with said electrodes of the third group, overlapping portions of a variable length;
each electrode of the fourth group, together with the adjacent electrodes of the third group and the adjoining portions of the second contact area forming a capacitor which connects the corresponding electrodes of the second group of the main row to the second contact area, the capacitance of this capacitor being defined by a specified impulse response of the transducer;
said electrodes of the third and fourth groups of the first auxiliary row being arranged so that the distances between said longitudinal axes of the adjacent electrodes of the third and fourth groups are selected so that they differ from the distances between said longitudinal axes of the adjacent electrodes of the first and second groups of the main row.

5 more elements

An acoustic surface wave filter comprising:

a piezoelectric substrate;
an input acoustic surface wave interdigital transducer arranged on said piezoelectric substrate;
an output acoustic surface wave interdigital transducer having a main row of electrodes and arranged on said piezoelectric substrate so that this main row of said electrodes is disposed in the same acoustic channel with said main row of said electrodes of said input transducer;
at least one said acoustic surface wave transducer comprising:
a first contact area arranged on said piezoelectric substrate;
a second contact area arranged on said piezoelectric substrate;
said main row of electrodes having longitudinal axes arranged on said piezoelectric substrate;
said main row of said electrodes including a first group of said electrodes electrically connected to the first contact area and a second group of said electrodes in parallel to said electrodes of the first group and arranged there between so as to form overlapping portions of said electrodes of the first and second group, said portions having the same length;
a first auxiliary row of electrodes having longitudinal axes arranged on said piezoelectric substrate between the main row of said electrodes and the second contact area;
the first auxiliary row of said electrodes including a third group of said electrodes galvanically coupled to the second contact area and a fourth group of said electrodes in parallel to said electrodes of the third group directly connected to the corresponding electrodes of the second group of the main row and disposed between said electrodes of the third group so that at least a part of them have, with the electrodes of the third group, overlapping portions of a variable length;
each said electrode of the fourth group, together with the adjacent said electrodes of the third group and the adjoining portion of the second contact area, forming a capacitor which connects the corresponding electrode of the second group of the main row with the second contact area, the capacitance of this capacitor being defined by a specified impulse response of the transducer;
said electrodes of the third and fourth groups of the first auxiliary row being disposed so that the distances between said longitudinal axes of the adjacent electrodes of the third and fourth groups differ from the distances between said longitudinal axes of the adjacent electrodes of the first and second groups of the main row.

9 more elements

Dependencies are inferred from the claim text.