Differential receive at an ultrasonic transducer

An ultrasonic transducer device comprising:

• a substrate;
• an edge support structure connected to the substrate;
• and
• a membrane connected to the edge support structure such that a cavity is defined between the membrane and the substrate, the membrane configured to allow movement at ultrasonic frequencies, the membrane comprising:
• a first piezoelectric layer having a first surface and a second surface;
• a second piezoelectric layer having a first surface and a second surface, wherein the second surface of the first piezoelectric layer faces the first surface of the second piezoelectric layer;
• a buffer layer between the first piezoelectric layer and the second piezoelectric layer, wherein the buffer layer has a thickness that tunes a frequency of operation of the ultrasonic transducer device to a desired frequency;
• a first electrode placed on the first surface of the first piezoelectric layer;
• a second electrode placed on the first surface of the second piezoelectric layer, such that the second electrode is disposed between the second piezoelectric layer and the buffer layer, and such that the first electrode and second electrode are on opposite sides of a neutral axis of the ultrasonic transducer device;
• and
• a third electrode placed on the second surface of the first piezoelectric layer, such that the third electrode is disposed between the first piezoelectric layer and the buffer layer;
• wherein, during a receive operation, the first electrode and the second electrode operate to provide differential receiving and the third electrode is electrically coupled to ground.

An ultrasonic transducer device comprising:

• a substrate;
• a support structure connected to the substrate;
• and
• a membrane connected to the support structure such that a cavity is defined between the membrane and the substrate, the membrane configured to allow movement at ultrasonic frequencies, the membrane comprising:
• a first piezoelectric layer having a first surface and a second surface;
• a second piezoelectric layer having a first surface and a second surface, wherein the second surface of the first piezoelectric layer faces the first surface of the second piezoelectric layer;
• a buffer layer between the first piezoelectric layer and the second piezoelectric layer, wherein the buffer layer has a thickness that tunes a frequency of operation of the ultrasonic transducer device to a desired frequency;
• a first electrode placed on the first surface of the first piezoelectric layer, wherein the first electrode is located at a region of maximum strain of the membrane;
• a second electrode placed on the first surface of the second piezoelectric layer, wherein the second electrode is a patterned electrode comprising more than one electrode components located proximate to the support structure of the membrane, such that the second electrode is disposed between the second piezoelectric layer and the buffer layer;
• and
• a third electrode placed on the second surface of the first piezoelectric layer, such that the third electrode is disposed between the first piezoelectric layer and the buffer layer.