MULTI-FREQUENCY ULTRA WIDE BANDWIDTH TRANSDUCER

• US 20130294202A1
• Filed: 03/15/2013
• Published: 11/07/2013
• Est. Priority Date: 05/01/2012
• Status: Active Grant

• Current Assignee: Fujifilm Dimatix, Inc. (Fujifilm Holdings Corporation)
• Original Assignee: Fujifilm Dimatix, Inc. (Fujifilm Holdings Corporation)
• Inventors: HAJATI, Arman
• Granted Patent: US 8,767,512 B2
• Time in Patent Office: Days
• US Class Current: 367/138
• CPC Class Codes: B06B 1/0622 on one surface
• CPC Class Codes: B06B 1/0629 Square array
• CPC Class Codes: G01S 15/8915 using a transducer array
• CPC Class Codes: G01S 15/8952 using discrete, multiple frequencies
• CPC Class Codes: G01S 7/52079 Constructional features constructional features of transducers B06B; mounting transducers G10K11/00; constructional features of ultrasonic medical diagnostic devices A61B8/44
• CPC Class Codes: G01S 7/521 Constructional features
• CPC Class Codes: G10K 11/346 using phase variation
• CPC Class Codes: H04R 17/00 Piezoelectric transducers; Electrostrictive transducers piezoelectric or electrostrictive elements in general H10N30/00; details of piezoelectric or electrostrictive motors, generators or positioners H10N30/00
• CPC Class Codes: H04R 2201/401 2D or 3D arrays of transducers
• CPC Class Codes: H04R 2201/403 Linear arrays of transducers
• CPC Class Codes: H10N 30/1071 with electrical and mechanical input and output, e.g. having combined actuator and sensor parts
• CPC Class Codes: H10N 30/2048 having non-planar shape
• CPC Class Codes: H10N 30/87 Electrodes or interconnections, e.g. leads or terminals
• CPC Class Codes: H10N 30/875 Further connection or lead arrangements, e.g. flexible wiring boards, terminal pins

Abstract

Piezoelectric micromachined ultrasonic transducer (pMUT) arrays and techniques for frequency shaping in pMUT arrays are described, for example to achieve both high frequency and low frequency operation in a same device. The ability to operate at both high and low frequencies may be tuned during use of the device to adaptively adjust for optimal resolution at a particular penetration depth of interest. In embodiments, various sizes of piezoelectric membranes are fabricated for tuning resonance frequency across the membranes. The variously sized piezoelectric membranes are lumped together by two or more separate electrode rails, enabling independent addressing between the two or more subgroups of sized transducer elements. Signal processing of the drive and/or response signals generated and/or received from each of the two or more electrode rails may achieve a variety of operative modes for the device, such as a near field mode, a far field mode, and an ultra wide bandwidth mode.

Claims

1. A piezoelectric micromachined ultrasonic transducer (pMUT) array, comprising:

a plurality of piezoelectric transducer element populations disposed over a substrate, each element population including at least first and second transducer elements having piezoelectric membranes of differing size, and each transducer element having a drive/sense electrode coupled to a piezoelectric membrane;

a plurality of sets of electrode rails disposed over the substrate, each set of electrode rails coupled to only one of the transducer element populations, wherein a first electrode rail of the set is electrically coupled to the drive/sense electrode of the first transducer element and a second electrode rail of the set is electrically coupled to the drive/sense electrode of the second transducer element.

2. The pMUT array of claim 1, wherein each element population includes a plurality of first transducer elements with a piezoelectric membrane of a first size and includes a plurality of second transducer elements with a piezoelectric membrane of a second size;

and

wherein the first electrode rail is electrically coupled to the drive/sense electrode of each of the first transducer elements and the second electrode rail is electrically coupled to the drive/sense electrode of each of the second transducer elements.

3. The pMUT array of claim 2, wherein the first transducer elements are sequentially incremented in size along a distance over the substrate with the difference in size between any two adjacent membranes being less that the difference in size between the largest and smallest of the first transducer elements.

4. The pMUT array of claim 3, wherein each piezoelectric transducer element has an ellipsoidal or spherical piezoelectric membrane.

5. The pMUT array of claim 4, wherein each element population includes n transducer elements having piezoelectric membranes of i differing sizes, and the set of electrode rails comprises m electrode rails;

and

wherein j transducer elements of a same size are electrically connected to a corresponding one of the m electrode rails, with n and i larger than 2.

6. The pMUT array of claim 5, wherein j is larger than 1 and m is equal to 2.

7. The pMUT array of claim 5, wherein a first subset of the i transducer elements are to output to the first electrode rail y differing frequency responses that are of a lower frequency than i-y differing frequency responses output to the second electrode rail by a second subset of the i transducer elements.

8. The pMUT array of claim 1, wherein the plurality of sets of electrode rails form a linear array across a first dimension of the substrate, wherein each of the piezoelectric transducer element populations comprises a linear array across a second dimension of the substrate, and wherein the piezoelectric membranes are circular or spheriodal with differing diameters.

9. The pMUT array of claim 1, wherein the plurality of sets of electrode rails forms a two-dimensional array of electrode rails along a first and second dimension of the substrate, and wherein the piezoelectric membranes are circular or spheriodal with differing diameters.

10. An apparatus for generating and sensing pressure waves in a medium, the apparatus comprising:

the pMUT array of claim 1;

at least one signal generator coupled to the pMUT array to apply a first electrical drive signal on the first electrode rail and a second electrical drive signal on the first electrode rail.

11. The apparatus of claim 10, wherein the at least one signal generator is to output first and second electrical drive signals having at least one of differing frequency, differing amplitude, or differing phase.

12. The apparatus of claim 10, wherein the first transducer element is smaller than the second transducer element and wherein the first electrical drive signal has a larger voltage amplitude than that of the second electrical drive signal.

13. The apparatus of claim 10, further comprising:

at least one receiver coupled to the pMUT array to receive a first electrical response signal from the first electrode rail and second electrical response signal from the second electrode rail; and

a signal processor coupled to the at least one receiver to process the electrical response signals received from the plurality of the drive/sense electrodes.

14. The apparatus of claim 13, wherein the first electrical response signal has a first frequency response spanning a bandwidth higher than that of the second electrical response signal.

15. The apparatus of claim 13, wherein the first transducer element is smaller than the second transducer element and wherein the signal processor is to apply a larger amplification to the first electrical response signal than to the second electrical response signal.

16. The apparatus of claim 15, wherein the at least one signal generator is to modulate the first and second electrical drive signals and wherein signal processor is to modulate the first and second electrical response signals to generate a cumulative frequency response having a bandwidth greater than either the first or second electrical response signals.

17. A method of generating and sensing pressure waves in a medium with the pMUT array of claim 1, the method comprising:

generating a first electrical signal;

generating a second electrical signal;

applying the first electrical signal to the first drive/sense electrode and the second electrical signal to the second drive/sense electrode; and

modulating at least one of amplitude and phase of one of first and second signals relative to the other to control a penetration depth of the pMUT array.

18. The method of claim 17, wherein the first transducer element is smaller than the second transducer element and wherein modulating at least one of amplitude and phase further comprises decreasing an amplitude of the first electrical drive signal relative an amplitude of the second electrical drive signal to increase the far field resolution of the pMUT array.

19. The method of claim 17, further comprising:

receiving a first electrical response signal from the first drive/sense electrode;

receiving a second electrical response signal from the second drive/sense electrode; and

signal processing the first and second electrical response signals to generate a cumulative frequency response having a bandwidth greater than either of the first or second electrical response signals alone.

20. The method of claim 19, wherein the first transducer element is smaller than the second transducer element and wherein the signal processing further comprises increasing an amplification of the first electrical response signal relative an amplification of the second electrical response signal to increase the near field resolution of the pMUT array or increasing the amplification of the second electrical response signal relative that of the first electrical response signal to increase the far field resolution of the pMUT array.