Bias control of electrostatic transducers

• US 6,795,374 B2
• Filed: 09/07/2001
• Issued: 09/21/2004
• Est. Priority Date: 09/07/2001
• Status: Expired due to Term

• Current Assignee: Siemens Medical Solutions USA Incorporated (Siemens AG)
• Original Assignee: Siemens Medical Solutions USA Incorporated (Siemens AG)
• Inventors: Bolorforosh, Mirsaid Seyed, Phelps, Robert N., Barnes, Stephen R.
• Primary Examiner(s): Lobo, Ian J.
• Application Number:
  US09/949,420
• Publication Number:
  US 20030048698A1
• Time in Patent Office: 1,110 Days
• Field of Search: 367/138, 600/443, 600/459, 600/437
• US Class Current: 367/138
• CPC Class Codes: B06B 1/0215 for generating pulses, e.g. bursts of oscillations, envelopes
• CPC Class Codes: B06B 1/0292 Electrostatic transducers, e.g. electret-type
• CPC Class Codes: B06B 2201/51 Electrostatic transducer
• CPC Class Codes: B06B 2201/76 Medical, dental
• CPC Class Codes: G01S 15/8915 using a transducer array
• CPC Class Codes: G01S 15/895 characterised by the transmitted frequency spectrum
• CPC Class Codes: G01S 7/52033 Gain control of receivers for seismic signals G01V1/245
• CPC Class Codes: G01S 7/52038 involving non-linear properties of the propagation medium or of the reflective target
• CPC Class Codes: G01S 7/52039 exploiting the non-linear response of a contrast enhancer, e.g. a contrast agent diagnostic techniques involving the use of contrast agents A61B8/481
• CPC Class Codes: H04R 2201/021 Transducers or their casings adapted for mounting in or to a wall or ceiling
• CPC Class Codes: H04R 23/00 Transducers other than those covered by groups H04R9/00 - H04R21/00 diaphragms for transducers of the distributed-mode type H04R7/045

Abstract

A method and system for controlling bias voltage for use with an electrostatic transducer are provided. The bias voltage is dynamically varied or set as a function of imaging mode, depth gain compensation, elevational apodization, azimuthal apodization, timing with respect to the transmit waveform, center frequency of transmit and receive waves and desired modulation. Opposite polarity on sub-elements is also provided for removing signals from electromagnetic interference and crosstalk between elements.

Claims

1. An ultrasound method for operating a multiple element capacitive membrane ultrasound transducer (cMUT), the method comprising:

(a) applying a bias voltage to a multiple element electrostatic transducer during one of a transmit and a receive event; and

(b) varying the bias voltage as a function of time during the one of the transmit event and receive event.

2. The method of claim 1 wherein (a) comprises applying the bias voltage to each of a plurality of elements.

3. The method of claim 1 wherein (a) comprises applying the varied bias voltage during the receive event and further comprising:

(c) applying a second bias voltage in a transmit mode different than the bias voltages of (a).

4. The method of claim 3 wherein (a) and (c) comprise applying the second bias voltage for transmission at a first frequency and applying the bias voltage of (a) for reception at a second frequency that is a harmonic of the first frequency.

5. The method of claim 1 further comprising:

(c) applying aperture apodization as a function of different bias voltages for each of the multiple elements.

6. The method of claim 1 wherein (b) comprises controlling gain as a function of target depth.

7. The method of claim 1 wherein (b) comprises varying the bias voltage during a single receive event.

8. The method of claim 1 wherein (b) comprises increasing the bias voltage with increasing time.

9. The method of claim 1 further comprising:

(c) applying different bias voltages to different elevationally spaced sub-elements of one of the multiple elements.

10. The method of claim 9 further comprising:

(d) varying the bias voltage of (c) as a function of an imaging mode of operation.

11. The method of claim 5 further comprising:

(d) varying the bias voltage of (c) as a function of an imaging mode of operation.

12. The method of claim 3 further comprising:

(d) applying a transmit waveform to one of the multiple elements; and

(e) changing from the bias voltage of (a) to the second bias voltage of (c) substantially simultaneously with a beginning of (d).

13. The method of claim 1 further comprising:

(c) generating a radio frequency signal; and

(d) applying the radio frequency signal with the bias voltage signal of (a).

14. The method of claim 1 further comprising:

(c) reversing a polarity of the bias voltage of (a) for a sub-element of one of the multiple elements.

15. An ultrasound multiple element capacitive membrane ultrasound transducer (cMUT) system, the system comprising:

at least one membrane ultrasound element configured to receive acoustic energy and output a responsive electrical signal; and

a voltage bias source connected with the at least one membrane ultrasound element, the voltage bias source operative to vary a bias voltage as a function of time during one of a transmit event and a receive event.

16. The system of claim 15 wherein the voltage bias source comprises a digital-to-analog converter.

17. The system of claim 15 wherein the voltage bias source is operative to vary the bias during a receive event and apply a second bias voltage in a transmit mode, the second bias voltage different than the bias voltages during a receive mode.

18. The system of claim 17 wherein the voltage bias source is operative to apply the second bias voltage for transmission at a first frequency and applying the bias voltage for reception at a second frequency that is a harmonic of the first frequency.

19. The system of claim 15 wherein the voltage bias source is operative to apply aperture apodization as a function of different bias voltages for different ones of the multiple elements.

20. The system of claim 15 wherein the voltage bias source is operative to varying the bias voltage during a single receive event.

21. The system of claim 15 wherein the voltage bias source is operative to increase the bias voltage with increasing time.

22. The system of claim 15 wherein the at least one membrane ultrasound element comprises at least two elevationally spaced sub-elements;

and

wherein the voltage bias source is operative to apply different bias voltages to different ones of the elevationally spaced sub-elements.

23. The system of claim 15 wherein the voltage bias source is operative to vary the bias voltage as a function of an imaging mode of operation.

24. The system of claim 17 further comprising:

a beamformer operative to apply a transmit waveform to the at least one membrane ultrasound element;

wherein the voltage bias source is operative to change from the bias voltage of receive mode to the second bias voltage of the transmit mode substantially simultaneously with a beginning of the transmit waveform.

25. The system of claim 15 further comprising:

a signal source connected with the bias voltage source to the at least one-membrane ultrasound element, the signal source operative to generate a radio frequency signal.

26. The system of claim 15 wherein the at least one membrane ultrasound element comprises at least two sub-elements connected with the bias voltage source with a reversed polarity.

27. An ultrasound method for operating a multiple element capacitive membrane ultrasound transducer (cMUT), the method comprising:

(a) applying a first DC bias voltage to at least one of the multiple elements in a receive mode;

(b) applying a second DC bias voltage in a transmit mode, the second bias voltage different than the first bias voltages;

(c) applying a transmit waveform to one of the multiple elements in the transmit mode; and

(d) changing from the first DC bias voltage to the second DC bias voltage substantially simultaneously with a beginning of the transmit waveform.

28. The method of claim 27 wherein (a) and (b) comprise applying the first and second DC bias voltages, respectively, to each of a plurality of the multiple elements.

29. The method of claim 27 wherein (d) comprises changing from the first DC bias voltage to the second DC bias voltage in synchronization with a leading edge of the transmit waveform.

30. The method of claim 27 wherein (b) comprises applying the second DC bias voltage for transmission at a first frequency and (a) comprises applying the first DC bias voltage for reception at a second frequency that is a harmonic of the first frequency.

31. The method of claim 27 further comprising:

(e) applying aperture apodization as a function of different bias voltages for each of the multiple elements.

32. The method of claim 27 further comprising:

(e) varying the first DC bias voltage as a function of depth.

33. The method of claim 27 wherein the second DC bias voltage is less than the first DC bias voltage and the beginning of the transmit waveform comprises a decreasing voltage.

34. The method of claim 27 further comprising:

(e) applying different bias voltages at one time to different elevationally spaced sub-elements of one of the multiple elements.

35. The method of claim 27 further comprising:

(e) varying the first and second DC bias voltages as a function of an imaging mode of operation.

36. The method of claim 27 further comprising:

(e) varying the first DC bias voltage as a function of time during a receive event.

37. The method of claim 27 further comprising:

(e) generating a radio frequency signal; and

(f) applying the radio frequency signal with the first DC bias voltage.

38. The method of claim 27 further comprising:

(e) reversing a polarity of the first bias voltage for a sub-element of one of the multiple elements.

39. An ultrasound multiple element capacitive membrane ultrasound transducer (cMUT) system, the system comprising:

at least one membrane ultrasound element;

a beamformer operative to apply a transmit waveform to the at least one membrane ultrasound element; and

a voltage bias source connected with the at least one membrane ultrasound element, the voltage bias source operative to change from a first DC bias voltage of a receive mode to a second different DC bias voltage of a transmit mode substantially simultaneously with a beginning of the transmit waveform.

40. The system of claim 39 wherein the voltage bias source comprises a digital-to-analog converter.

41. The system of claim 39 wherein the voltage bias source is operative to apply the second DC bias voltage for transmission at a first frequency and applying the first DC bias voltage for reception at a second frequency that is a harmonic of the first frequency.

42. The system of claim 39 wherein the voltage bias source is operative to apply aperture apodization as a function of different bias voltages for different ones of the multiple elements.

43. The system of claim 39 wherein the voltage bias source is operative to changing from the first DC bias voltage to the second DC bias voltage in synchronization with a leading edge of the transmit waveform.

44. The system of claim 39 wherein the at least one membrane ultrasound element comprises at least two elevationally spaced sub-elements;

and wherein the voltage bias source is operative to apply different bias voltages to different ones of the elevationally spaced sub-elements.

45. The system of claim 39 wherein the voltage bias source is operative to vary the DC bias voltage in the receive mode as a function of an imaging mode of operation.

46. The system of claim 39 wherein the voltage bias source is operative to vary the first DC bias voltage as a function of time during a receive event.

47. The system of claim 39 further comprising:

a signal source connected with the bias voltage source to the at least one-membrane ultrasound element, the signal source operative to generate a radio frequency signal.

48. The system of claim 39 wherein the at least one membrane ultrasound element comprises at least two sub-elements connected with the bias voltage source with a reversed polarity.