WO2017188893A1 - Dispositif à ultrasons, procédé de formation de celui-ci et procédé de commande de celui-ci - Google Patents

Dispositif à ultrasons, procédé de formation de celui-ci et procédé de commande de celui-ci Download PDF

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Publication number
WO2017188893A1
WO2017188893A1 PCT/SG2017/050209 SG2017050209W WO2017188893A1 WO 2017188893 A1 WO2017188893 A1 WO 2017188893A1 SG 2017050209 W SG2017050209 W SG 2017050209W WO 2017188893 A1 WO2017188893 A1 WO 2017188893A1
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Prior art keywords
ultrasonic transducer
ultrasound device
impedance
resonance
matching circuit
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PCT/SG2017/050209
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English (en)
Inventor
Yuanjin Zheng
Huaxi SUN
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Nanyang Technological University
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Nanyang Technological University
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Priority to CN201780021301.4A priority Critical patent/CN109075760B/zh
Publication of WO2017188893A1 publication Critical patent/WO2017188893A1/fr
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H7/00—Multiple-port networks comprising only passive electrical elements as network components
    • H03H7/38—Impedance-matching networks
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
    • B06B1/02—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
    • B06B1/0207—Driving circuits
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
    • B06B1/02—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
    • B06B1/0292—Electrostatic transducers, e.g. electret-type
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
    • B06B1/02—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
    • B06B1/06—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction
    • B06B1/0644—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using a single piezoelectric element
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
    • G01H15/00—Measuring mechanical or acoustic impedance
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
    • G01H3/00—Measuring characteristics of vibrations by using a detector in a fluid
    • G01H3/04—Frequency

Definitions

  • Various embodiments relate to an ultrasound device, a method for forming the ultrasound device and a method for controlling the ultrasound device. Background
  • a micromachined ultrasonic transducer is widely used in ultrasound imaging systems. It converts an electrical signal into ultrasonic waves and vice versa.
  • MUT micromachined ultrasonic transducer
  • a piezoelectric micromachined ultrasonic transducer uses piezoelectric materials to generate a voltage signal while a capacitive micromachined ultrasonic transducers (cMUT) modulates the capacitance to output a current signal.
  • a low noise amplifier (LNA) is usually used for amplifying the electrical signal, and normally there is no matching network between the MUT and the LNA so that the signal is not maximized or the noise performance is not optimized.
  • LNA low noise amplifier
  • FIG. 1 shows a schematic diagram 180 illustrating a passive amplification matching configuration of the prior art, provided in between an antenna 181 with a resistance, Rantenna, 182, and a LNA 183, and having an inductor, L, 184 and a capacitor, C, 185 connected to an input of the LNA 183.
  • the operating frequency, co s is defined by Equation (1):
  • a first-order low-pass filter provides voltage amplification and NF reduction when the inductor 184 resonates with the capacitor 185 at the operating frequency o3 ⁇ 4.
  • This matching technique is used in radio frequency (RF) systems and nuclear magnetic resonance (NMR) systems.
  • RF radio frequency
  • NMR nuclear magnetic resonance
  • an inductor is added to resonate with the parasitic capacitor of the LNA while in the NMR systems, a capacitor is added for the internal inductor of the NMR coil.
  • the first-order matching networks for these systems contain only two components and one of them is fixed, resulting in a fixed voltage gain and NF. Also, the bandwidth for matching is very narrow in this way since the first-order network only generates a sharp voltage peak at the operating frequency.
  • an ultrasound device may include an ultrasonic transducer, and a resonance matching circuit electrically coupled to the ultrasonic transducer, wherein the resonance matching circuit is configured to cooperate with the ultrasonic transducer to generate, from an impedance of the ultrasonic transducer, an effective impedance at a resonance condition of the ultrasonic transducer to provide a gain to an electrical signal generated by the ultrasonic transducer and to reduce a noise figure of the ultrasound device at the resonance condition.
  • a method for forming an ultrasound device having an ultrasonic transducer and a resonance matching circuit electrically coupled to the ultrasonic transducer may include determining an impedance of the ultrasonic transducer, determining a gain to be provided at a resonance condition of the ultrasonic transducer to an electrical signal generated by the ultrasonic transducer, and designing the resonance matching circuit based on the impedance and the gain for the resonance matching circuit to cooperate with the ultrasonic transducer to generate, from the impedance, an effective impedance at the resonance condition suitable to provide the gain.
  • a method for controlling an ultrasound device having an ultrasonic transducer and a resonance matching circuit electrically coupled to the ultrasonic transducer may include receiving an ultrasound at the ultrasonic transducer to generate an electrical signal via the ultrasonic transducer in response to the ultrasound received, and operating the ultrasound device at a resonance condition of the ultrasonic transducer so that the resonance matching circuit cooperates with the ultrasonic transducer to generate, from an impedance of the ultrasonic transducer, an effective impedance at the resonance condition to provide a gain to the electrical signal and to reduce a noise figure of the ultrasound device at the resonance condition.
  • FIG. 1 shows a schematic diagram illustrating a passive amplification matching configuration of the prior art.
  • FIG. 2 shows a schematic diagram illustrating an electrical model of a micromachined ultrasonic transducer (MUT).
  • MUT micromachined ultrasonic transducer
  • FIG. 3A shows a schematic block diagram of an ultrasound device, according to various embodiments.
  • FIG. 3B shows a schematic block diagram of an ultrasound device, according to various embodiments.
  • FIG. 3C shows a flow chart illustrating a method for forming an ultrasound device, according to various embodiments.
  • FIG. 3D shows a flow chart illustrating a method for controlling an ultrasound device, according to various embodiments.
  • FIG. 4 shows a schematic diagram of an ultrasound device, according to various embodiments.
  • FIG. 5 shows a schematic diagram of a low noise amplifier (LNA), according to various embodiments.
  • LNA low noise amplifier
  • FIG. 6 shows a schematic diagram of a circuit illustrating second-order resonance matching for a piezoelectric micromachined ultrasonic transducer (pMUT), according to various embodiments.
  • FIG. 7A shows a schematic diagram of a circuit for an impedance transformer
  • FIG. 7B shows a schematic diagram of a circuit for a modified impedance transformer, according to various embodiments.
  • FIG. 8 shows a schematic diagram illustrating the Thevenin's equivalent circuit for a circuit with resonance matching, according to various embodiments.
  • FIG. 9 shows a schematic diagram of a front-end of a piezoelectric micromachined ultrasonic transducer (pMUT) system, according to various embodiments.
  • FIG. 10 shows a Smith Chart illustrating wideband matching, according to various embodiments.
  • FIG. 11 shows a schematic diagram illustrating a set-up for the measurement of voltage amplification.
  • FIG. 12 shows a plot of comparison of signals with and without matching in time domain obtained based on the set-up of FIG. 1 1.
  • FIG. 13 shows a plot of comparison of noise figure (NF) with and without the matching network of various embodiments.
  • FIG. 14 shows a schematic diagram illustrating a set-up for the measurement of sensitivity.
  • FIGS. 15A and 15B show respective plots of received signal without and with resonance matching of various embodiments based on the set-up of FIG. 14.
  • FIG. 16 shows a schematic diagram illustrating a model for wideband matching simulation.
  • FIG. 17 shows a plot of measured frequency response of the pMUT for the model of FIG. 16.
  • FIG. 18 shows a plot of wideband matching results obtained based on the model of FIG. 16.
  • Embodiments described in the context of one of the methods or devices are analogously valid for the other methods or devices. Similarly, embodiments described in the context of a method are analogously valid for a device, and vice versa.
  • the articles “a”, “an” and “the” as used with regard to a feature or element include a reference to one or more of the features or elements.
  • the term “about” or “approximately” as applied to a numeric value encompasses the exact value and a reasonable variance.
  • Various embodiments may provide a resonance matching method for a micromachined ultrasonic transducer (MUT).
  • MUT micromachined ultrasonic transducer
  • Various embodiments may enlarge the signal and reduce the noise figure (NF) of a piezoelectric micromachined ultrasonic transducer (pMUT) system and a capacitive micromachined ultrasonic transducers (cMUT) system by inserting passive components for matching, for example, to a low noise amplifier (LNA).
  • NF noise figure
  • Various embodiments may provide a voltage gain for a pMUT and a current gain for a cMUT, and NF reduction by using passive components matching.
  • the matching network may be multi-order and it may be applied with a wideband MUT. Besides, the gain could be set by the designer, which is more flexible for different applications, as compared to known techniques.
  • various embodiments may include a co-design with MUT and LNA.
  • Various embodiments may reduce the noise figure of an ultrasound receiving system or device.
  • FIGS. 3A and 3B show schematic block diagrams of respective ultrasound devices 300a, 300b, according to various embodiments.
  • the ultrasound device 300a, 300b includes an ultrasonic transducer 302, and a resonance matching circuit 304 electrically coupled to the ultrasonic transducer 302, wherein the resonance matching circuit 304 is configured to cooperate with the ultrasonic transducer 302 to generate, from an impedance of the ultrasonic transducer 302, an effective impedance at a resonance condition of the ultrasonic transducer 302 to provide a gain to an electrical signal generated by the ultrasonic transducer 302 and to reduce a noise figure of the ultrasound device 300a, 300b at the resonance condition.
  • an ultrasound device 300a, 300b may be provided.
  • the ultrasound device 300a, 300b may include an ultrasonic transducer 302.
  • the ultrasonic transducer 302 may be adapted to receive ultrasound (or an ultrasound signal or an ultrasonic wave) (e.g., 303, FIG. 3B).
  • the ultrasound device 300a, 300b may be an ultrasound receiver, or ultrasound receiving device.
  • the ultrasound device 300a, 300b may further include a resonance matching circuit (or matching network) 304 electrically coupled (or connected) (e.g., as represented by the line 306) to the ultrasonic transducer 302.
  • the resonance matching circuit 304 may be configured to cooperate with the ultrasonic transducer 302 at a resonance condition (or resonance frequency or operating frequency) of the ultrasonic transducer 302 to generate an effective impedance at the resonance condition from an impedance of the ultrasonic transducer to provide a gain (or amplification) to an electrical signal generated (and outputted) by the ultrasonic transducer 302 and to reduce a noise figure (NF) of the ultrasound device 300a, 300b at the resonance condition.
  • NF noise figure
  • the resonance matching circuit 304 may cooperate with the ultrasonic transducer 302 to generate an effective impedance from or based on an impedance of the ultrasonic transducer 302 so as to provide a gain at the resonance condition and to reduce the noise figure at the resonance condition.
  • the ultrasound device 300a, 300b employs impedance transformation to provide the gain and reduction in the noise figure, rather than based on impedance matching for power transfer.
  • the effective impedance is a parameter transformed from the impedance of the ultrasonic transducer 302.
  • the impedance of the ultrasonic transducer 302 may mean the resistance of the ultrasonic transducer 302, and correspondingly, the term "effective impedance" may mean the "effective resistance”.
  • the ultrasonic transducer 300a, 300b may receive ultrasound 303 and generate an electrical signal in response to the ultrasound 303 received.
  • the resonance matching circuit 304 cooperates with the ultrasonic transducer 302 to generate the effective impedance so as to provide the gain to the electrical signal generated.
  • gain refers to an electrical (signal) gain.
  • the noise figure at the resonance condition may be at a reduced level as compared to the level of the noise figure that may be present at a non- resonance condition of the ultrasonic transducer 302, or the level of the noise figure that otherwise may be present in a device without the resonance matching circuit 304.
  • the term "noise figure” refers to the degradation of the signal to noise ratio caused by a device. The noise figure is a figure of merit and may be used to quantify the departure of a "real" device from an "ideal" device.
  • the noise figure may be dependent on the gain that is provided.
  • the noise figure may have an inverse relationship with the gain.
  • the impedance of the ultrasonic transducer 302 refers to the "internal" impedance of the ultrasonic transducer 302 (e.g., actual impedance of the ultrasonic transducer 302) while the effective impedance refers to the impedance inclusive of the effects of the resonance matching circuit 304 acting on the ultrasonic transducer 302 at the resonant condition.
  • the effective impedance may be of a value that is different from that of the impedance of the ultrasonic transducer 302.
  • the resonance matching circuit 304 may cooperate with the ultrasonic transducer 302 to form a multi-order circuit (e.g., n-order circuit where n > 2) to generate, from the impedance of the ultrasonic transducer 302, the effective impedance.
  • the resonance matching circuit 304 and the (circuit of the) ultrasonic transducer 302 may cooperatively or collectively form a multi-order circuit (or multi- order filter).
  • the effective impedance may refer to the impedance of the multi-order circuit formed at the resonant condition.
  • the resonance matching circuit 304 may be arranged at an output side or downstream side of the ultrasonic transducer 302. In this way, the resonance matching circuit 304 may act on the electrical signal generated by the ultrasonic transducer 302.
  • the resonance matching circuit 304 may include electrical components having respective values designed based on the impedance of the ultrasonic transducer 302 to generate the effective impedance to provide the gain (that is desired) at the resonance condition. As a non-limiting example, the values may be adjusted by the designer according to the gain and/or bandwidth needed.
  • the resonance matching circuit 304 may include a plurality of passive components, e.g., one or more inductors, and one or more capacitors. This may mean that the resonance matching circuit 304 may define a passive resonance matching circuit.
  • the respective values of at least one inductor and at least one capacitor may depend on the circuit of the ultrasonic transducer 302. In various embodiments, a higher gain to be provided may require a higher number of electrical components in the resonance matching circuit 304.
  • the electrical components may include an inductor 308 and a capacitor 310 connected in series to ground.
  • the inductor 308, the capacitor 310 and an equivalent capacitance (e.g., see Co 626, FIG. 6) of the ultrasonic transducer 302 may form a multi-order circuit.
  • a first end of the inductor 308 may be electrically coupled (or connected) to the ultrasonic transducer 302, a second end of the inductor 308 may be connected to a first end of the capacitor 310, and a second end of the capacitor 310 may be grounded (or connected to ground).
  • a first end of the capacitor 310 may be electrically coupled (or connected) to the ultrasonic transducer 302, a second end of the capacitor 310 may be connected to a first end of the inductor 308, and a second end of the inductor 308 may be grounded (or connected to ground).
  • a low noise amplifier (LNA) 312 may be electrically coupled (e.g., as represented by the line 314) to the resonance matching circuit 304.
  • the inductor 308 and the capacitor 310 may be connected to each other at a node and the LNA 312 may be connected to the node.
  • an input of the LNA 312 may be connected to the node.
  • the term “low noise amplifier” or its acronym “LNA” may mean an electronic amplifier that amplifies a very low-power signal without significantly degrading its signal-to-noise ratio (SNR). While a “general” amplifier increases the power of both the signal and the noise present at its input, an LNA is designed to minimize additional noise.
  • the LNA 312 may be arranged at an output side or downstream side of the resonance matching circuit 304. In this way, the LNA 312 may act on an electrical signal outputted by the resonance matching circuit 304.
  • the resonance matching circuit 304 may be arranged between the ultrasonic transducer 302 and the LNA 312.
  • the ultrasonic transducer 302 may be connected on the input side or to the input of the resonance matching circuit 304, while the LNA 312 may be connected on the output side or to the output of the resonance matching circuit 304.
  • a magnitude of an input impedance, ZLNA, of the low noise amplifier 312 may be larger than a magnitude of the effective impedance, Ri n .
  • IZLNAl Rin, e.g., IZLNAl>10Ri n .
  • the low noise amplifier 312 may be or may include a differential common source amplifier, or a common source amplifier (e.g., for CMOS (complementary metal-oxide-semiconductor)), or a common emitter amplifier (e.g., for BJT (bipolar junction transistor)).
  • CMOS complementary metal-oxide-semiconductor
  • BJT bipolar junction transistor
  • the low noise amplifier 312 may be or may include any amplifier as long as it satisfies two conditions: (1) its input impedance is large (e.g., >100 kQ), and (2) its input voltage noise is much larger than its input current noise, as explained further below in relation to FIG. 9.
  • the ultrasonic transducer 302 may be or may include a micromachined ultrasonic transducer (MUT).
  • MUT micromachined ultrasonic transducer
  • the term "micromachined ultrasonic transducer” or its acronym “MUT” may mean an ultrasonic transducer that is fabricated using silicon micro-machining technology (MEMS technology). This may mean that a micromachined ultrasonic transducer is a silicon- based ultrasonic transducer.
  • a micromachined ultrasonic transducer employs a diaphragm (or membrane) which may vibrate in response to a signal received by the diaphragm. In an ultrasound receiver, ultrasound or ultrasonic waves incident or applied to the diaphragm induces vibration of the diaphragm to generate an electrical signal.
  • the micromachined ultrasonic transducer may be or may include a piezoelectric micromachined ultrasonic transducer (pMUT).
  • the resonance matching circuit 304 may provide a voltage gain and NF reduction for a pMUT ultrasound device.
  • piezoelectric micromachined ultrasonic transducer or its acronym “pMUT” may mean a MEMS- based piezoelectric ultrasonic transducer.
  • a pMUT employs a diaphragm (or membrane) which may vibrate in response to a signal received by the diaphragm.
  • a piezoelectric material is coupled to the diaphragm.
  • ultrasound or ultrasonic waves incident or applied to the diaphragm of a pMUT induces vibration of the diaphragm to generate, via the piezoelectric material, an electrical signal.
  • a pMUT employs a piezoelectric material to generate a voltage signal.
  • a magnitude of the effective impedance may be larger than a magnitude of the impedance of the piezoelectric micromachined ultrasonic transducer.
  • the ultrasonic transducer 302 is a pMUT
  • the LNA 312 may include a low noise voltage amplifier
  • the LNA 312 may be a high impedance LNA (e.g., >100 kQ)
  • the effective impedance may be larger than the impedance of the pMUT
  • the electrical signal generated (and outputted) by the pMUT is a voltage signal
  • the gain provided is a voltage gain.
  • the micromachined ultrasonic transducer may be or may include a capacitive micromachined ultrasonic transducers (cMUT).
  • the resonance matching circuit 304 may provide a current gain and NF reduction for a cMUT ultrasound device.
  • the term "capacitive micromachined ultrasonic transducer” or its acronym “cMUT” may mean a MEMS-based capacitive ultrasonic transducer employing a diaphragm.
  • a cMUT employs a diaphragm (or membrane) which may vibrate in response to a signal received by the diaphragm.
  • the diaphragm is positioned over a cavity that may be formed in a silicon substrate, where the diaphragm and the substrate define two separate electrodes.
  • ultrasound or ultrasonic waves incident or applied to the diaphragm of a cMUT induces vibration of the diaphragm, thereby causing a change in the capacitance between the two electrodes to generate an electrical signal.
  • a cMUT modulates a capacitance to output a current signal.
  • a magnitude of the effective impedance may be smaller than a magnitude of the impedance of the capacitive micromachined ultrasonic transducer.
  • the ultrasonic transducer 302 is a cMUT
  • the LNA 312 may include a low noise current amplifier
  • the LNA 312 may be a low impedance LNA (e.g., ⁇ 100 ⁇ )
  • the effective impedance may be smaller than the impedance of the cMUT
  • the electrical signal generated (and outputted) by the cMUT is a current signal
  • the gain provided is a current gain.
  • the ultrasonic transducer 300a, 300b may be based on pMUT or cMUT.
  • the ultrasonic transducer 302 may be a band-pass transducer. This may mean that the ultrasonic transducer 302 passes signals of frequencies within a certain range (or band) and rejects (or attenuates) signals of frequencies outside that range.
  • the ultrasound device 300a, 300b of various embodiments may operate on the basis of noise reduction. This may mean that the order of the multi-order circuit and/or the inductor and capacitor values depend on noise reduction, rather than on impedance matching.
  • FIG. 3C shows a flow chart 350 illustrating a method for or of forming an ultrasound device having an ultrasonic transducer and a resonance matching circuit electrically coupled to the ultrasonic transducer, according to various embodiments.
  • an impedance of an ultrasonic transducer is determined.
  • a gain to be provided at a resonance condition of the ultrasonic transducer to an electrical signal generated by the ultrasonic transducer is determined.
  • the resonance matching circuit (of the ultrasound device) is designed based on the impedance and the gain for the resonance matching circuit to cooperate with the ultrasonic transducer to generate, from the impedance, an effective impedance at the resonance condition suitable to provide the gain.
  • a noise figure of the ultrasound device at the resonance condition may also be determined from the impedance determined and the gain determined.
  • the impedance of the ultrasonic transducer may be determined at the resonance condition.
  • respective values of (passive) electrical components of the resonance matching circuit may be determined. This may include determining respective values of at least one capacitor and at least one inductor of the electrical components.
  • a Smith Chart may be used.
  • the respective values of the electrical components may be determined using a Smith Chart.
  • the ultrasound device may further include a low noise amplifier electrically coupled to the resonance matching circuit, and the low noise amplifier may be designed based on the effective impedance.
  • the ultrasonic transducer may be or may include a micromachined ultrasonic transducer (MUT).
  • MUT micromachined ultrasonic transducer
  • the micromachined ultrasonic transducer may be or may include a piezoelectric micromachined ultrasonic transducer (pMUT) or a capacitive micromachined ultrasonic transducers (cMUT).
  • pMUT piezoelectric micromachined ultrasonic transducer
  • cMUT capacitive micromachined ultrasonic transducers
  • FIG. 3D shows a flow chart 355 illustrating a method for or of controlling an ultrasound device having an ultrasonic transducer and a resonance matching circuit electrically coupled to the ultrasonic transducer, according to various embodiments.
  • an ultrasound is received at the ultrasonic transducer for the ultrasonic transducer to generate an electrical signal in response to the ultrasound received.
  • the ultrasound device is operated at a resonance condition of the ultrasonic transducer so that the resonance matching circuit cooperates with the ultrasonic transducer to generate, from an impedance of the ultrasonic transducer, an effective impedance at the resonance condition to provide a gain to the electrical signal and to reduce a noise figure of the ultrasound device at the resonance condition.
  • FIG. 4 an ultrasound device 400 having a MUT 402, a resonance matching network 404 and a LNA 412.
  • the resonance matching network 404 is arranged in between the MUT 402 and the LNA 412, and connected to the MUT 402 and the LNA 412.
  • the simplest second-order matching is illustrated in FIG. 4 to first clarify the approach employed in various embodiments and a multi-order matching is derived later and would be decribed further below.
  • the second-order resonance matching network 404 may include one inductor and one capacitor which may be arranged in one of two configurations as illustrated in FIG.4.
  • an inductor 408a and a capacitor 410a may be arranged in series between the MUT 402 and ground, with the inductor 408a grounded, and an interconnection node between the inductor 408a and the capacitor 410a connected to the LNA 412.
  • an inductor 408b and a capacitor 410b may be arranged in series between the MUT 402 and ground, with the capacitor 410b grounded, and an interconnection node between the inductor 408b and the capacitor 410b connected to the LNA 412.
  • a pMUT is used as the MUT 402 as a non-limiting example for illustration and understanding purposes; however, it should be appreciated that the same mechanism also works for a cMUT as the MUT 402.
  • the pMUT is any piezoelectric transducer which could be modeled as, but not limited to, a Butterworth- Van-Dyke (BVD) model as shown in FIG. 2.
  • BBD Butterworth- Van-Dyke
  • Descriptions relating to the ultrasound device 400 and/or any components thereof are provided based on the MUT 402 being a pMUT. It should be appreciated that suitable modifications may be made to the ultrasound device 400 and/or any components thereof where the MUT 402 is a cMUT. Non-limiting examples of some of these modifications are described further below.
  • the LNA 412 may be any low noise voltage amplifier whose input impedance may be larger than approximately 100 kQ.
  • a custom-designed differential common source amplifier 512 of the type having a structure as shown in FIG. 5 may be employed as the LNA 412.
  • the LNA 512 may be fabricated based on 0.18 ⁇ CMOS technology.
  • the LNA 512 may include a transistor 513 where the current going through this transistor 513 is the DC bias current, bias resistors 514a, 514b, decoupling capacitors 515a, 515b, input stage transistors 516a, 516b, cascade stage transistors 517a, 517b, and a common mode feedback stage comprising transistors 519a, 519b and resistors 518a, 518b.
  • Each of the input stage transistors (or input transistors) 516a, 516b should have a large transconductance, g m , while each of the transistors (or load transistors) 519a, 519b should have a small g m for low input-referred noise.
  • the W/L (width to length) ratio for each of the transistor 513, input stage transistors 516a, 516b, and cascade stage transistors 517a, 517b may be (900 ⁇ /0.18 ⁇ ), and the W/L (width to length) ratio for each of the transistors 519a, 519b may be (150 ⁇ /2 ⁇ ).
  • the DC bias current is preferably large to obtain a large g m for the input transistors 516a, 516b.
  • Cascade (comprising transistors 517a, 517b) is used for gain boosting without injecting noise. Common mode feedback by using two large resistors 518a, 518b (- 10 kQ each) is used for low noise.
  • Bias resistors 514a, 514b at the input of the LNA 512 is about 10 kQ each and the decoupling capacitors 515a, 515b at the input of the LNA 512 is about 2 nF each.
  • specification for the LNA 512 may be as shown in Table 1 below.
  • Vdd may be about 1.8 V
  • Biasi may be about 1.1 V
  • Bias 2 may be about 0.9 V
  • Bias 3 may be about 0.6 V.
  • Configuration (1) 405a in FIG. 4 is used as a non-limiting example for the resonance matching network 404 for illustration and understanding purposes; however, it should be appreciated that configuration (2) 405b may instead be suitably employed.
  • FIG. 6 shows a schematic diagram of a circuit of the ultrasound device 400 illustrating second-order resonance matching (based on configuration (1) 405a) for a piezoelectric micromachined ultrasonic transducer (pMUT) 602, according to various embodiments.
  • the pMUT 602 is represented by a BVD model 690 having a series arrangement 630 of a capacitor C m 620, an inductor L m 622, a resistor R m 624, and a voltage source V s 628, and another capacitor Co 626 arranged in parallel to the series arrangement 630.
  • Co 626 represents the static capacitance of the piezoelectric material of the pMUT 602, while the mechanical vibrating system of the pMUT 602 is modeled by a series RLC (series arrangement 630).
  • L m 622 describes the mass of the mechanical system.
  • R m 624 and C m 620 vary to model the changes in boundary conditions.
  • an inductor, L, 408a and a capacitor, C, 410a are arranged between an LNA 412 and the pMUT 602.
  • L 408a, C 410a and Co 626 form a second- order network or circuit.
  • the input impedance of the LNA 412 is normally very high to minimize loading effect.
  • the operating frequency (or resonance frequency/condition) 622 and C m 620 may cancel each other.
  • V s 628 is the received signal source in the ultrasound transducer 602.
  • L 408a and C 410a are assumed to be ideal and the input impedance of the LNA 412 is assumed to be infinite.
  • the approach of voltage amplification of various embodiments is through impedance transformation.
  • the resistor R m 624 and the capacitors C 410a, Co 626 illustrated in FIG. 6 form an impedance transformer as shown in FIG. 7A.
  • the resistor R m 624 and the capacitor Co 626 are connected in parallel, in turn connected in series with the capacitor C 410a.
  • the admittance, Yi n may be defined as:
  • Equation (2) j(O s R m (C + C 0 ) + l 0) 2 R C 2
  • the resonance matching raises R m to Ri n . Since power is constant if LC is ideal, voltage is amplified accordingly. This could be explained by Thevenin's theorem as illustrated in FIG. 8.
  • the output impedance is transformed from R m 624 to Rin 834 and the open terminal voltage is amplified from V s 628 to V 2 836.
  • the relationship of power, P, to the output impedance and the open terminal voltage may be defined as below:
  • the voltage gain, a is set by C as may be defined according to Equation (8) and the value of L may be determined by Equations (4) and (6).
  • ⁇ ]( ⁇ +— + ⁇ -— Equation (8).
  • the matching network of various embodiments may also reduce the NF of the pMUT system (or cMUT system).
  • the signal flow may be as shown in FIG. 9 illustrating, as a non-limiting example, a front-end of a piezoelectric micromachined ultrasonic transducer (pMUT) system 900.
  • An ultrasound or ultrasonic wave 903 is received by a transducer (pMUT) 902 and converted into an electrical signal, which feeds into an LNA 912 through a matching network 904.
  • a gain a may be provided.
  • v 2 937 is the output noise of the pMUT 902.
  • v 2 938 and i 2 939 represent the input-referred noise of the LNA 912.
  • the passive network 904 is assumed to be noiseless.
  • the NF may be calculated by referring all noise parts at the node B located between the p as shown below:
  • the matching network 904 may be an impedance transformer. Ri n increases as a increases. When Ri n is
  • Rin may make the current noise " 939 dominate and NF may start to increase.
  • there may be an optimal value of a for noise matching.
  • configuration (2) 405b illustrated in FIG. 4 may also be used for resonance matching which has the same mechanism as the configuration ( 1) 405a as described herein.
  • the matching condition is that, at the operating frequency (or resonance condition), R m (e.g., 624, FIGS. 7A, 7B, 8) may be transformed to be a larger resistor through the second-order network 404 (FIG. 4). Please also refer to FIG. 8.
  • the total equivalent capacitance resonates with the total equivalent inductance so it is called resonance matching.
  • a high-order matching network may be used.
  • the approach is still the same, that is transforming R m to be a larger resistor Ri n .
  • the design procedures are stated below, using FIG. 9 as a non-limiting example.
  • the impedance, Z, of the pMUT 902 may be measured by equipment and then R m (e.g., 624, FIGS. 6, 7A, 7B) may be known.
  • the voltage gain a may be set by the designer and Ri n (e.g., see FIGS. 7B and 8) may be calculated to be a 2 R m .
  • FIG. 10 illustrates a non-limiting example of how this may be achieved using a Smith Chart 1070.
  • Z*(complex conjugate) is plotted as the source 1072 and Ri n is plotted as the load 1074.
  • the required bandwidth defines the boundary curve.
  • Values of the capacitors and inductors may be determined by tracing the impedance curve bouncing between the x-axis and the boundary curve.
  • the number of matching elements is the number of arcs in the graph or Smith Chart 1070. This method may ensure that the number of matching elements is minimized.
  • the desired Rin may be obtained after the matching network 904 as shown in FIG. 9.
  • a wider bandwidth means more matching elements if the voltage gain a is fixed. If the bandwidth is fixed, a higher voltage gain a means more matching elements. Since the passive components are non-ideal in reality, more matching elements may bring more loss and noise.
  • the input impedance of the LNA, ZLNA should be sufficiently high when compared with Ri n , otherwise they may form a voltage divider which may reduce the input voltage of LNA.
  • IZLNAI > 10Ri n may be provided.
  • Various embodiments could be applied to cMUT as well whose electrical circuit may be similar to that for pMUT as shown in FIG. 2, except that the signal is mainly current and the source impedance, R m , is very high (>few kQ). Then in FIG. 9, the matching network 904 may transform Z to be a lower resistance Ri n and the current gain may be achieved. Thus, the NF of the system 900 dominated by the current noise may be reduced in the same manner due to the passive current gain a.
  • Various embodiments may include one or more of the following, but are not limited to:
  • the transducer may be either a pMUT or a cMUT.
  • the LNA may be a high impedance (e.g., > 100 kQ) low noise amplifier for pMUT, or a low impedance (e.g., ⁇ 100 ⁇ ) low noise amplifier for cMUT.
  • Resonance matching network may be placed between the transducer and the LNA, for example, as shown in FIG. 9.
  • Matching condition is that, at the operating frequency (or resonance frequency or condition) of the pMUT, Ri n in FIG. 9 is larger than the resistance R m in FIG. 2 and Rin is purely resistive. For cMUT, at the operating frequency (or resonance frequency or condition), Ri n is smaller than R m .
  • Inserted components L, C and the internal capacitance of pMUT or cMUT form a multi-order network.
  • the design of the noise enhancement module (e.g., the resonance matching network and the LNA) is different from the conventional impedance matching network: the order and/or inductor/capacitor values for various embodiments depend on noise reduction but not impedance matching.
  • the transducer may be a band-pass device.
  • the transducer has a certain type of frequency response and its bandwidth is wide (e.g., fractional bandwidth > 50%). Since various embodiments may include a co-design with the transducer circuit, it may maintain its frequency response type and bandwidth.
  • a multi-order filter may be employed. Impedance transformation is used. By using a Smith Chart, the impedance of the transducer may be increased to a much higher value to obtain the desired voltage gain and noise figure reduction.
  • various embodiments are not simply a matching technique; various embodiments provide a noise reduction method including co-design with a transducer.
  • the method may also include a co-design with an LNA. Values of the inductors and the capacitors may depend on the transducer circuit. Besides, there may be certain design considerations for the LNA in order to achieve a voltage gain and noise figure reduction.
  • the receiver end may be increased to high impedance (much larger than 50 ⁇ (ohm)), which may amplify voltage and reduce the noise figure.
  • high impedance much larger than 50 ⁇ (ohm)
  • a known matching technique of coupling an L-C matching network between an output of an excitation circuit and an input of a transducer is used for impedance matching to 50 ⁇ for maximum power transfer. Further, the known technique is used for a transmission end. When applied in a receiver end, this known technique cannot amplify voltage or reduce the noise figure.
  • FIG. 11 shows a schematic diagram illustrating a set-up 1160 for the measurement of voltage amplification.
  • the transmitter, Tx, 1161 is a pMUT for transmitting a signal, and is connected to a pulser 1162 via a coaxial cable 1163 of resistance 50 ⁇ .
  • the receiver, Rx, 1164 is another pMUT for receiving a signal. Both Tx 1164 and Rx 1164 are put in a water tank 1165 containing water.
  • the enhancement module 1166 contains the matching network (or matching circuit) and the LNA circuit, according to various embodiments.
  • An oscilloscope 1167 is connected to the enhancement module 1166. This setup 1160 aims to measure the voltage gain of the matching network.
  • Simulation results obtained also show that the NF of the system could be reduced.
  • the pMUT model, the matching network and the LNA designed corresponding to the circuit illustrated FIG. 5 may be put together and simulated in a design tool (e.g., Cadence).
  • Cadence a design tool
  • FIG. 13 illustrating a plot 1370 of comparison of the result 1372 for the NF with the matching network and the result 1374 for the NF without the matching network, with the matching network, the NF drops from about 10 dB to about ldB at the working frequency.
  • FIG. 14 shows a schematic diagram illustrating a set-up 1460 for the measurement of sensitivity.
  • a pMUT 1461 is put in a water tank 1465 containing water to detect a target 1469 that may be positioned a distance, d, from the pMUT 1461.
  • the pMUT 1461 is connected to a pulser 1462 to provide a signal towards the target 1469.
  • the signal is reflected by the target 1469 as an echo and the echo is received by the pMUT 1461 that is also connected to a matching network 1466 and a LNA 1468.
  • the echo is amplified by the LNA 1468 and measured in the oscilloscope 1467.
  • the distance, d, from the pMUT 1461 to the target 1469 is a measure of sensitivity. A longer distance results in a smaller amplitude of the echo. If the system could detect the target 1469 at a further distance by adding a resonance matching network 1466, it means that the sensitivity is improved.
  • FIGS. 15A and 15B The results obtained are shown in FIGS. 15A and 15B.
  • the distance, d is increased to about 35 mm, without resonance matching, no useful signal may be observed as shown in plot 1570 of FIG. 15 A.
  • the echo is shadowed by noise. It means that the system is limited to detect targets at a maximum distance of approximately 35 mm.
  • FIG. 16 shows a schematic diagram illustrating a model 1660 for wideband matching simulation.
  • the pMUT block 1662 is the electrical model of a commercial pMUT whose operating frequency is approximately 8.5 MHz with about 60 % fractional bandwidth.
  • the frequency response of the pMUT is measured and shown in plot 1770 in FIG. 17.
  • the 1 mV signal source in the pMUT block 1662 simulates the signal received by the pMUT.
  • a multi-order network 1664 is used for matching and the inductors are non-ideal in simulation.
  • the matching network 1664 may include several stages of inductors and capacitors connected in a duplicated configuration as shown in FIG. 16.
  • the voltage gain is designed to be 8 and the bandwidth of the pMUT is maintained.
  • the LNA, represented by block 1666 is represented by its PSPICE model with resistor feedback, providing approximately 26 dB gain. The results obtained are plotted in FIG. 18.
  • FIG. 18 shows a plot 1870 of wideband matching results obtained based on the model 1660 of FIG. 16, illustrating the result 1872 with the matching network 1664 and the result 1874 without matching.
  • the voltage gain defined before is the gain from the original signal picked up by the pMUT 1662 to the output voltage after the matching network 1664.
  • the voltage gain may be defined as V 2 /V s . If no matching network is applied, the output voltage of the pMUT 1662 is Vi, which is smaller than V s .
  • the signal with matching (V 2 ) at about 8.5 MHz is about -28 dB.
  • the bandwidth is cut off at -6 dB point. It could be seen that wideband matching is achieved with a real gain V 2 /Vi over 18 dB across the bandwidth from about 6 MHz to about 1 1 MHz.
  • various embodiments may be implemented in all kinds of ultrasound systems, including systems which may be based on pMUT or cMUT. Such products may include scanners, imaging sensors, probes, detectors and so on, covering ultrasonic applications in all aspects of industrial and medical fields. Various embodiments may enable these applications to have a higher sensitivity and better performance in receiving signals.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Transducers For Ultrasonic Waves (AREA)
  • Ultra Sonic Daignosis Equipment (AREA)
  • Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)

Abstract

Des modes de réalisation de la présente invention concernent un dispositif à ultrasons. Le dispositif à ultrasons comprend un transducteur d'ultrasons et un circuit d'adaptation de résonance connecté électriquement au transducteur d'ultrasons. Le circuit d'adaptation de résonance est configuré pour coopérer avec le transducteur d'ultrasons en vue de générer, à partir d'une impédance du transducteur d'ultrasons, une impédance efficace à un état de résonance du transducteur d'ultrasons pour fournir un gain à un signal électrique généré par le transducteur d'ultrasons et pour réduire une valeur de bruit du dispositif d'ultrasons à l'état de résonance. D'autres modes de réalisation de la présente invention concernent également un procédé de formation d'un dispositif à ultrasons et un procédé de commande d'un dispositif à ultrasons.
PCT/SG2017/050209 2016-04-25 2017-04-13 Dispositif à ultrasons, procédé de formation de celui-ci et procédé de commande de celui-ci Ceased WO2017188893A1 (fr)

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CN110247628A (zh) * 2019-05-30 2019-09-17 西安交通大学 基于MOSFET的CMUTs谐振信号输出网络
CN111865255B (zh) * 2020-07-31 2021-06-01 诺思(天津)微系统有限责任公司 射频模组设计方法、射频模组及通信设备
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