Multilevel bipolar pulser
Circuitry for ultrasound devices is described. A multilevel pulser is described, which can provide bipolar pulses of multiple levels. The multilevel pulser includes a pulsing circuit and pulser and feedback circuit. Symmetric switches are also described. The symmetric switches can be positioned as inputs to ultrasound receiving circuitry to block signals from the receiving circuitry.
1. An ultrasound device comprising:
at least one capacitive ultrasonic transducer;
a pulser having an input terminal and an output terminal coupled to the capacitive ultrasonic transducer and configured to provide an input signal to the capacitive ultrasonic transducer having a value selected from among multiple selectable values;
a feedback circuit coupled to the output terminal and the input terminal of the pulser and configured to provide a control signal to the input terminal of the pulser based on a comparison of a detection signal, representing or derived from the input signal, to a first threshold voltage of a plurality of comparison threshold voltages generated by the feedback circuit; and
a dividing circuit configured to provide the detection signal to the feedback circuit, wherein a voltage of the detection signal is proportional to a voltage of the input signal.
2. The ultrasound device according to claim 1 , wherein the pulser is configured to provide a bipolar input signal to the capacitive ultrasonic transducer.
3. The ultrasound device according to claim 1 , wherein the pulser is configured to provide the input signal having a direct current (DC) component that is greater than zero.
4. The ultrasound device according to claim 1 , wherein the feedback circuit comprises a resistive ladder configured to generate the plurality of comparison threshold voltages.
5. The ultrasound device according to claim 1 , wherein the feedback circuit is configured to control the control signal to temporally apodize the input signal.
6. The ultrasound device according to claim 1 , wherein the feedback circuit is digitally controlled.
7. The ultrasound device according to claim 1 , wherein the feedback circuit is configured to provide the control signal to the pulser asynchronously.
8. The ultrasound device according to claim 1 , where the capacitive ultrasonic transducer is a first capacitive ultrasonic transducer of a plurality of capacitive ultrasonic transducers, the pulser is a first pulser of a plurality of pulsers, the feedback circuit is a first feedback circuit of a plurality of feedback circuits, the control signal is a first control signal of a plurality of control signals and the input signal is a first input signal of a plurality of input signals;
wherein the plurality of feedback circuits are configured to control the plurality of control signals to spatially apodize the plurality of input signals provided to the plurality of capacitive ultrasonic transducers.
9. The ultrasound device according to claim 1 , wherein the capacitive ultrasonic transducer is coupled to bias circuitry and configured to receive a bias voltage having an absolute value that is greater than zero.
10. The ultrasound device according to claim 1 , wherein the pulser comprises a first transistor exhibiting a first type of conductivity and a second transistor exhibiting a second type of conductivity different from the first type of conductivity.
11. A method of operating an ultrasound device having a capacitive ultrasonic transducer, a pulser coupled to the capacitive ultrasonic transducer, a dividing circuit, and a feedback circuit, the method comprising:
with the pulser, providing an input signal to the capacitive ultrasonic transducer;
with the dividing circuit, deriving a detection signal from the input signal, a voltage of the detection signal being proportional to a voltage of the input signal; and
with the feedback circuit, generating a plurality of comparison threshold voltages and providing a control signal to the pulser to control the provision of the input signal based on a result obtained by comparing the detection signal to a first threshold voltage of the plurality of comparison threshold voltages.
12. The method of operating an ultrasound device according to claim 11 , wherein the pulser is configured to provide a bipolar input signal to the capacitive ultrasonic transducer.
13. The method of operating an ultrasound device according to claim 11 , wherein the pulser is configured to provide the input signal having a value selected from among multiple selectable values.
14. The method of operating an ultrasound device according to claim 11 , wherein the pulser is configured to provide the input signal having a direct current (DC) component that is greater than zero.
15. The method of operating an ultrasound device according to claim 11 , wherein the feedback circuit is configured to control the control signal to temporally apodize the input signal.
16. The method of operating an ultrasound device according to claim 11 , wherein providing the control signal to the pulser to control the providing of the input signal is performed asynchronously.
17. The method of operating an ultrasound device according to claim 11 , wherein the feedback circuit is digitally controlled.
18. The method of operating an ultrasound device according to claim 11 , wherein the capacitive ultrasonic transducer is a first capacitive ultrasonic transducer of a plurality of capacitive ultrasonic transducers, the pulser is a first pulser of a plurality of pulsers, the feedback circuit is a first feedback circuit of a plurality of feedback circuits, the control signal is a first control signal of a plurality of control signals and the input signal is a first input signal of a plurality of input signals;
wherein the plurality of feedback circuits are configured to control the plurality of control signals to spatially apodize the plurality of input signals provided to the plurality of capacitive ultrasonic transducers.