Energy efficient simplified analogue phased array transducer for beam steering

Abstract

The present invention relates in a first aspect to an energy efficient simplified analogue phased array transducer for ultrasound beam steering, in a second aspect to a product, such as a small wearable ultrasound device for signalling changes in a human or animal body, such as a liquid volume in a body cavity of a human or an animal, in a third aspect to a use of said device, and in a fourth aspect to a method of operating an ultrasound device.

Claims

1. Phased array transducer for ultrasound beam steering comprising an array of n*m transducer elements operating at a frequency of 20 kHz-50 MHz, preferably wherein at least two neighbouring transducer elements are at a mutual distance of approximately 0.5 wavelength (λ±10%), preferably at least 1*m transducers, transmission control electronics for beam steering of the array comprising at least one high-voltage pulse source, preferably of >12 V, wherein sources are linked to a low-voltage timing circuit, preferably of <5.5V for timing of the at least one pulse sources, receiving control electronics simplified to limit energy consumption when processing received ultrasound, wherein the receiving control electronics is selected from (i) at least one and preferably all ultrasound receiving transducer element are adapted for determining ultrasound energy in connection with a rectifying amplifier and the rectifying amplifier in connection with an analogue adder for adding the outputs of the rectifying amplifiers, (ii) <50%, preferably <20%, of the n*m transducer elements connected or connectable to receive electronics, and (iii) combinations thereof, and an electrical power source in electrical connection with the array or an electrical connection for providing electrical power to the array.

2. Phased array transducer according to claim 1, wherein the rectifying amplifier is selected from circuits like a diode, a quadratic amplifier, a convertor for converting a negative amplitude into a positive amplitude and for maintaining a positive amplitude, a logarithmic amplifier, and variations thereof, and combinations thereof.

3. Phased array transducer according to any of claims 1-2, wherein the receiving control electronics is adapted to optimize beam steering in reception, for at least two, and preferably not all, ultrasound receiving transducer elements.

4. Phased array transducer according to any of claims 1-3, wherein the analogue adder is adapted to add the amplitude of the positive phase and the amplitude of the negative phase of the received signal.

5. Phased array transducer according to any of claims 1-4, comprising one high-voltage pulse transmission source per transducer element, wherein sources are preferably identical.

6. Phased array transducer according to any of claims 1-5, comprising a voltage controller for applying a voltage to the transducer elements.

7. Phased array transducer according to any of claims 1-6, wherein the receiving control electronics is connected or connectable to <50% of the receiving transducer elements, such as <20% of the receiving transducer elements, and/or wherein connected or connectable receiving transducer elements are selected such that k not-connected transducer elements are in between the connected transducer elements, wherein k is selected from 1-7 preferably wherein k is 2-6, more preferably wherein k is 3-5, such as k is 3.

8. Phased array transducer according to any of claims 1-7, wherein n∈[1-10] and m∈[2-1024], preferably wherein n∈[1-3] and m∈[4-128], more preferably wherein n∈[1-3] and m∈[8-48], even more preferably wherein n∈[1,2] and m∈[16-36], such as n∈[1] and m∈[24-32], and/or wherein transducer elements comprise a MEMS, such as a CMUT and PMUT, bulk piezo material, such as ceramic and crystalline material, piezocomposite, active piezoelectric material, ferroelectric ceramic, and combinations thereof.

9. Phased array transducer according to any of claims 1-8, comprising at least one series of m transducer elements over a length, wherein each of the electrodes on one side of all m transducer elements are connected electrically to the respective transducer electronics, and wherein the (counter-)electrodes on the other side are i) all connected together, or ii) the electrodes on the other side are split in two halves, where half of the electrode length is connected to a first electrode connector and the other half electrode length is connected to a second electrode connector, or iii) a p.sup.th fraction of p≥3 of the electrode length is connected to a p.sup.th electrode connector, wherein p preferably ∈[3-5], perpendicular to the long transducer elements, or iv) combinations thereof.

10. Phased array transducer according to any of claims 1-9, wherein the transducers elements are capable of operating separately, sequentially, in phase-shift mode, in parallel mode, in spatial scan mode, in intensity mode, in pulsed mode, in harmonic mode, variations thereof, and combinations thereof, and/or wherein both transmit and receive electronics are directly coupled to the transducer elements, preferably wherein the output resistance of the transmitters is high, such as >1 MΩ.

11. Product comprising a phased array transducer according to any of claims 1-10, wherein the product is preferably selected from a wearable device, a portable device, a medical device, a non-destructive testing device, variations thereof, and combinations thereof.

12. Product according to claim 11, wherein the product is a small wireless ultrasound device for signalling a change in a body tissue, body vessel or body cavity, such as a bladder, preferably a stand-alone device.

13. Product according to claim 11 or 12, comprising at least one transducer director, and/or a positioner for maintaining the product in a position, preferably at least one sensor for determining posture of a body of a user, a contacting means for contacting the product to a skin of the body, an energy scavenger, an ADC for converting analogue array signals to digitized output signals, wherein the product is wearable and is substantially flat.

14. Product according to any of the claims 11-13, comprising ant one of a movement sensor, an accelerometer, gyroscope, and a magnetic sensor.

15. Product according to any of the claims 11-14, wherein the product electronics is one or more of an IC, a piezoelectric element, a printed circuit board (PCB), and combinations thereof.

16. Product according to any of the claims 11-15, wherein the transducer is one or more of a MEMS (CMUT or PMUT), a piezoelectric (ceramic or crystalline), and combinations thereof.

17. Product according to any of the claims 11-16, wherein the wearable product consists of one integrated package.

18. Use of a product according to any of the claims 11-17 for determining or monitoring a liquid volume in a cavity, such as a bladder, a uterus (amniotic fluid), a sinus, a pleural cavity, a pericardial sac, and a vessel such as an aorta, for detecting or monitoring at least one of aneurism, infection, tumour, dehydration, pleural effusion, urine influx rate from at least one kidney, hydrocephalus, a size of a human or animal cavity, for determining a liquid volume in a lung, for training, for ultrasound image forming, as a flow sensor, for (semi)continuous monitoring over longer periods of time, for monitoring during normal life, and for monitoring inside or outside a hospital or (long-term) caretaking environment, optionally in combination with a further (second) device.

19. Method of operating an ultrasound product according to any of claims 11-17, comprising the steps of determining an amount of liquid in a bladder, based on the amount determined, performing a further act, or refraining from further action.

Description

SUMMARY OF FIGURES

[0043] FIG. 1. Schematic set-up of part of a prior art trans-mitting device.

[0044] FIG. 2: Schematic set-up of part of a prior art receiving device.

[0045] FIG. 3: Analog beam forming principle.

[0046] FIG. 4: Digital beam forming principle.

[0047] FIGS. 5a-f: Calculated amplitude traces.

[0048] FIG. 6: The width of the transmit-receive sensitivity (thick lines) and the maximum height of the side lobes, relative to the centre peak (thin lines).

[0049] FIG. 7: The width of the transmit-receive sensitivity (thick lines) and the maximum height of the side lobes, relative to the centre peak (thin lines).

[0050] FIGS. 8a-d show possible array layouts according to exemplary embodiments.

[0051] FIGS. 9a-d show several options to simplify and to limit energy consumption, compared to the standard beam steering approach in reception, according to exemplary embodiments.

[0052] FIGS. 10a-c show some options for connecting only a fraction of the available transducer elements to the receiving circuit according to respective embodiments.

DETAILED DESCRIPTION OF FIGURES

[0053] FIG. 1: Transmit pulse formation by a phased array to a focal point, as used in the prior art. For this purpose a voltage pulse is provided to each transducer element E with a well-defined delay D so as to form a beam focus at the desired point P.

[0054] FIG. 2: Reception of reflections from a focal point by a phased array, as used in the prior art. The delay of each signal makes that all signals arrive at the same time at the summation.

[0055] FIG. 3: Analog beam forming principle, where the delays are made in the analogue domain, before the analogue summation and the analogue-to-digital conversion, as used in the prior art.

[0056] FIG. 4: Digital beam forming principle, where each signal is first digitized by an analogue-to-digital converter and then the delays are added during signal processing in the digital domain, as used in the prior art.

[0057] FIGS. 5a-f: Calculated amplitude traces for ultrasound beams coming from various directions (8 (a), 16 (b), 24 (c), 33 (d), 42 (e) and 54 (f) degrees, respectively) for three approaches to construct these data (not rectified “interfering data”, rectified “abs(data)” and negative values made zero “pos(data)”) and one reference line (“conventional beam steering”) with interference and the optimal delays in reception, as known from the prior art.

[0058] The receive beam steering approach, with four (of e.g. 24) receiving transducers with non-receiving transducer elements in between has been extended in FIG. 6, where all possibilities are elaborated. From this figure, it appears that three non-receiving transducer elements between the receiving ones is the optimal configuration when using only four transducer elements for reception of the ultrasound. This results in an array of 24 transducer elements, where all 24 transducers are used for sending and only transducer Nr. 6, 10, 14 and 18 are used for receiving the ultrasound. It is observed that that the directional angle of the first (and largest) side lobe in transmission coincides with the angle of the first minimum in reception, reducing the side lobes in the transmit-receive sensitivity considerably. As a reference we show a phased array with 24 transducers sending: The dotted line denotes a single receiving transducer element and the dashed line denotes all 24 receiving. Note that the number of 24 elements is only used as an example to show the principle. Different optimizations may apply for different number of elements.

[0059] The receive beam steering approach, with transducers with three non-receiving transducer elements in-between has been extended in FIG. 7, where the number of transducer elements has been varied, keeping their distance fixed. From this figure, it appears that five receiving transducers with three non-receiving transducer elements between the receiving ones is the optimal configuration in this example. This results in and array of 24 transducer elements, where all transducers are used for sending and only transducer Nr. 4, 8, 12, 16 and 20 are used for receiving the ultrasound. As a reference we show a phased array with 24 transducers sending: The dotted line denotes a single receiving transducer element and the dashed line denotes all 24 receiving.

[0060] FIGS. 8a,b show an array connected with one electrical contact at the bottom side and ten at the top (top and bottom view) and FIGS. 8c,d show an array connected with two electrical contact at the bottom side and ten at the top (top and bottom view).

[0061] FIGS. 9a-d show examples of the standard, prior art, beam steering approach in reception (FIG. 9a), the approach with rectifying amplifiers selected from circuits, like a diode, a quadratic amplifier, a convertor for converting a negative amplitude into a positive amplitude and for maintaining a positive amplitude, a logarithmic amplifier, and variations thereof, and combinations thereof (FIG. 9b), the approach of beam steering with a reduced number of transducer elements connected (FIG. 9c) and a combination of the above (FIG. 9d).

[0062] FIGS. 10a-c show some concepts of operating or connecting only a fraction of the available transducer elements to the receiving circuit according to respective embodiments. In such a configuration of a pulse echo ultrasound system the transducer acts as both transmitter and receiver. The transducer can be activated by a pulse of high voltage, typically 25 to 150 volts and short duration, typically 100 to 500 nano-seconds and the receiver will receive a voltage of less than 1 volt, typically in the millivolt range.

[0063] In FIG. 10a shows an embodiment in which the plurality of transducer elements E is connected to both a transmission circuit Tx as well as to a receiving circuit Rx over corresponding switches S. The respective operation, i.e. transmission or reception, is set by operating the switches S accordingly. In an embodiment, all, or a relatively large number of the transducer elements are switched to the transmission circuit during the transmission phase, whereas only a part, or a relatively small number of the transducer elements are switched to the receiving circuit during the receiving phase. In this way, an energy saving mode may be implemented by solely controlling the switches S accordingly, while maintaining in principle the capability of using all transducer elements during the receiving phase.

[0064] The option shown in FIG. 10b shows an embodiment in which only a reduced number of switches S are provided for those transducer elements that are actually used during the receiving phase. This embodiment may further contribute to reducing the element count and circuit complexity of the receive electronics, besides providing the advantages relating to energy and power saving, especially during receiving.

[0065] FIG. 10c shows an embodiment wherein both transmit and receive electronics are directly coupled to the transducer elements without any switch in between. This is possible in case the output resistance of the pulsers is sufficiently high, such as >1 MΩ, so that no current will flow (typically <1 μA), when the receive signal comes in. This embodiment may further contribute to reducing the element count and circuit complexity even further by avoiding the switches S from FIG. 10a. and FIG. 10b.

[0066] The invention although described in detailed explanatory context may be best understood in conjunction with the accompanying examples and figures.