Pulse train excitation for capacative micromachined ultrasonic transducer
Aspects of this disclosure relate to driving a capacitive micromachined ultrasonic transducer (CMUT) with a pulse train of unipolar pulses. The CMUT may be electrically excited with a pulse train of unipolar pulses such that the CMUT operates in a continuous wave mode. In some embodiments, the CMUT may have a contoured electrode.
1. A method of driving a capacitive micromachined ultrasonic transducer, the method comprising:
electrically exciting the capacitive micromachined ultrasonic transducer with a pulse train comprising a plurality of unipolar pulses,
wherein the plurality of unipolar pulses of the pulse train cause the capacitive micromachined ultrasonic transducer to operate in a continuous wave mode.
2. The method of claim 1 , wherein each pulse of the pulse train is positive relative to a baseline of the pulse train.
3. The method of claim 2 , wherein the baseline is zero Volts.
4. The method of claim 1 , further comprising generating a final pulse of the pulse train, the final pulse starting at a first bias voltage and ending at a second bias voltage different from the first bias voltage.
5. The method of claim 4 , further comprising:
maintaining the second bias voltage after the final pulse ends; and
processing a signal received by the capacitive micromachined ultrasonic transducer operating in a receive mode, wherein the signal is received by the capacitive micromachined ultrasonic transduce while the second bias voltage is applied to the capacitive micromachined ultrasonic transducer.
6. The method of claim 4 , wherein the first bias voltage has a smaller magnitude than the second bias voltage.
7. The method of claim 4 , wherein the second bias voltage is less than a pull-in voltage of the capacitive micromachined ultrasonic transducer.
8. The method of claim 4 , wherein one or more of the unipolar pulses starts and ends at the first bias voltage.
9. The method of claim 4 , further comprising generating an initial pulse of the pulse train, the initial pulse starting at a third bias voltage and ending at the first bias voltage.
10. The method of claim 1 , wherein at least some of the plurality of pulses is shaped as a half-sine pulse, and the method further comprises generating a final pulse of the pulse train, the final pulse being shaped as a partial half-sine pulse.
11. The method of claim 1 , further comprising generating the pulse train such that each of the unipolar pulses is shaped as one of a half-sine pulse, a Gaussian pulse, or a rectangular pulse.
12. The method of claim 1 , further comprising adjusting one or more of a pulse width of at least some of the unipolar pulses, a repetition period of the pulse train, or an amplitude of at least some of the unipolar pulses such that a plate of the capacitive micromachined ultrasonic transducer, during said electrically exciting, does not physically contact an underlying substrate of the capacitive micromachined ultrasonic transducer.
13. The method of claim 1 , further comprising applying a bias voltage to the capacitive micromachined ultrasonic transducer to adjust the baseline of the pulse train.
14. The method of claim 13 , wherein the bias voltage is non-zero and has a magnitude that is less than a magnitude of a pull-in voltage of the capacitive micromachined ultrasonic transducer.
15. The method of claim 1 , wherein the capacitive micromachined ultrasonic transducer transmits high intensity focused ultrasound in response to said electrically exciting.
16. The method of claim 1 , wherein the capacitive micromachined ultrasonic transducer transmits haptic energy to a person in response to said electrically exciting.
17. The method of claim 1 , wherein the capacitive micromachined ultrasonic transducer comprises a contoured electrode.
18. A system for generating ultrasound, the system comprising:
a capacitive micromachined ultrasonic transducer; and
excitation circuitry configured to generate a pulse train of unipolar pulses and drive the capacitive micromachined ultrasonic transducer with the pulse train such that the capacitive micromachined ultrasonic transducer outputs ultrasound energy in a continuous wave mode.
19. The system of claim 18 , further comprising:
receive circuitry configured to process a signal received from the capacitive micromachined ultrasonic transducer in a receive mode;
wherein the excitation circuitry is configured to generate the pulse train such that a final pulse of the pulse train starts at a first bias voltage and ends at a second bias voltage different from the first bias voltage, and wherein the excitation circuitry is configured to apply the second bias voltage to the capacitive micromachined ultrasonic transducer in the receive mode.
20. A method of using a capacitive micromachined ultrasonic transducer, the method comprising:
electrically exciting the capacitive micromachined ultrasonic transducer with a pulse train of unipolar pulses such that the capacitive micromachined ultrasound transducer outputs a continuous wave of ultrasound energy in a continuous wave mode, wherein a final pulse of the pulse train starts at a first bias voltage and ends at a second bias voltage different from the first bias voltage, wherein a final pulse of the pulse train starts at a first bias voltage and ends at a second bias voltage different from the first bias voltage;
maintaining the second bias voltage after the final pulse ends; and
processing a signal received by at least the capacitive micromachined ultrasonic transducer operating in an imaging mode, wherein the signal is received by the capacitive micromachined ultrasonic transducer while the second bias voltage is applied to the capacitive micromachined ultrasonic transducer.
21. The method of claim 20 , wherein the first bias voltage and the second bias voltage have a same polarity.