MEMS-switched ultrasonic transducer array with improved reliability
Various approaches for improving reliability in an ultrasound system having transducer elements, phase transmission lines, and a switch matrix having beamforming switches for connecting the phase transmission lines to the transducer elements involve operating the beamforming switches to avoid “hot” switching as the activation pattern of the transducers changes.
1. A method of improving reliability in an ultrasound system comprising (i) a plurality of transducer elements, (ii) a phase generator connected to a plurality of phase transmission lines, and (iii) a switch matrix comprising a plurality of beamforming switches for switchably connecting various ones of the phase transmission lines to the transducer elements, each of the transducer elements being associated with a set of beamforming switches each connected to a different phase transmission line, wherein some of the beamforming switches are open and some of the beamforming switches are closed in accordance with an initial switch activation pattern, the method comprising:
(a) reducing the differential voltage between the phases at the phase generator;
(b) reducing the differential voltage between the phases at near the beamforming switches; and
(c) following steps (a) and (b), altering the initial switch activation pattern.
2. The method of claim 1 , wherein the differential voltage in step (a) is reduced below a first predetermined threshold corresponding to a voltage closer to zero than ±0.5V.
3. The method of claim 1 , wherein the differential voltage in step (b) is reduced below a second predetermined threshold corresponding to a voltage closer to zero than ±0.5V.
4. The method of claim 1 , further comprising a step of pausing after performing steps (a) and (b) and before performing step (c).
5. The method of claim 4 , wherein the pausing step has a duration determined by at least one of an environmental condition or a sonication parameter.
6. The method of claim 5 , wherein the environmental condition is an ambient RF level.
7. The method of claim 5 , wherein the environmental condition is reflection from the transducer elements.
8. The method of claim 5 , further comprising the step of monitoring a voltage on a closed switch, wherein the environmental condition is a magnitude of the monitored voltage.
9. The method of claim 5 , wherein the sonication parameter comprises an amplitude of a pulse transmitted from one of the transducer elements.
10. The method of claim 1 , further comprising a step of pausing after performing step (a) and before performing step (b).
11. The method of claim 1 , wherein step (b) is performed by progressively connecting the phase transmission lines together using a plurality of sets of differential switches, each differential switch being associated with at least one of the phase transmission lines.
12. The method of claim 11 , wherein at least one of the beamforming switches or the differential switches is an MEMS switch.
13. The method of claim 11 , wherein at least one of the beamforming switches or the differential switches is a CMOS switch.
14. The method of claim 11 , wherein at least one of the differential switches or the beamforming switches in each set are sequentially activated in a predetermined order.
15. The method of claim 14 , wherein the predetermined order is based on a previous switching order.
16. The method of claim 15 , wherein the predetermined order is determined by a number of previous times each of the differential switches was the first differential switch coupling the associated phase transmission line to another phase transmission line when changing the initial switch activation pattern to a new switch activation pattern.
17. The method of claim 15 , wherein the predetermined order is based on a number of previous times each of the differential switches in each switch set being a sacrificial switch.
18. The method of claim 15 , wherein the predetermined order is determined by a number of previous times each of the beamforming switches was the first beamforming switch that was activated when changing the initial switch activation pattern to a new switch activation pattern.
19. The method of claim 1 , wherein, in a set of the beamforming switches in which a first beamforming switch is closed and a second beamforming switch is open, step (c) comprises closing the second beamforming switch and, thereafter, opening the first switch.
20. The method of claim 1 , wherein, in a set of the beamforming switches in which a first group of beamforming switches is closed and a second group of beamforming switches is open, step (c) comprises closing the second group of beamforming switches and, thereafter, opening the first group of beamforming switches, the beamforming switches in the second group being sequentially closed in a predetermined order.
21. The method of claim 20 , wherein the predetermined order is based on a previous switching order.
22. The method of claim 21 , wherein the predetermined order is determined by a number of previous times each of the beamforming switches in the second group was first to be closed.
23. The method of claim 20 , wherein the predetermined order is based on a geometry of the transducer elements.
24. The method of claim 23 , wherein the geometry comprises relative locations of the transducer elements in the ultrasound system.