Patent Application
20230412968
This application claims the benefit of European Patent Application No. 22179664, filed on Jun. 17, 2022, which application is hereby incorporated herein by reference.
The present disclosure relates generally to electronic devices, and more particularly to a MEMS device and an audio device including the MEMS device.
Electrodynamic speakers can be used in tweeter-woofer-systems (TWS). They can be fairly broadband and may deliver high sound pressure levels but require a certain space which is a challenge for use and integration in TWS applications. A MEMS device may comprise semiconductor materials, for example, on a basis of silicon, wherein electrical current may flow based on conductive materials such as metal materials and/or doping of a semiconductor material. MEMS devices may implement loudspeakers.
MEMS devices may implement speakers, but improved MEMS devices are needed for broadband speaker applications.
A MEMS device and an audio device including such a MEMS device are described below. According to one embodiment, a MEMS device comprises a first speaker arrangement being configured for emitting sound in a first audio frequency range and a second speaker arrangement being configured for emitting sound in a different second audio frequency range. The first speaker arrangement may be configured as a woofer, and the second speaker arrangement configured as a tweeter. The MEMS device may include a housing that provides for a common back volume for the first speaker arrangement and the second speaker arrangement, in particular wherein the housing is arranged to further provide for electrically connecting the first speaker arrangement and the second speaker arrangement to an environment of the package.
Preferred embodiments of the present disclosure are described herein while making reference to the accompanying drawings in which:
Equal or equivalent elements or elements with equal or equivalent functionality are denoted in the following description by equal or equivalent reference numerals even if occurring in different figures.
In the following description, a plurality of details is set forth to provide a more thorough explanation of embodiments of the present disclosure. However, it will be apparent to those skilled in the art that embodiments of the present disclosure may be practiced without these specific details. In other instances, well known structures and devices are shown in block diagrams form rather than in detail in order to avoid obscuring embodiments of the present disclosure. In addition, features of the different embodiments described hereinafter may be combined with each other, unless specifically noted otherwise.
Embodiments described herein relate to a MEMS device comprising at least a first speaker arrangement and a second speaker arrangement. Embodiments further relate to an audio device including such a MEMS device, and in particular to a combination of a woofer and tweeter MEMS device for improved efficiency and full audio bandwidth support. Such a MEMS device may be a packaged MEMS device and may comprise or provide for a housing, e.g., a packaging to form a package. In connection with embodiments described herein, a package may comprise a housing or cover or lid for one or more semiconductor devices or dies or integrated circuits, e.g., to house dies, possibly for their assembly on a printed circuit board which may itself be placed in a housing. However, a package is usually not intended to be opened again. A material for such a housing may comprise, for example, a metal material, a plastic material, a glass material, a ceramic material, or a combination thereof.
The package of a MEMS device or a packaged MEMS device may be understood as a housing (or cover, or lid) that may comprise at least two chips of the at least two speaker arrangements in the same package. Further, the at least two chips of the at least two speaker arrangements may be arranged on a common substrate of the package. Thus, the packaged MEMS device could provide for a common (i.e., shared) back volume for the at least two chips of the at least two speaker arrangements, which could result in a more compact arrangement than known speaker arrangements.
While a woofer may be understood as a speaker that emits sound, preferably in a frequency range of at most 500 Hz, at most 300 Hz or at most 200 Hz, a tweeter may be understood as a speaker that emits sound in a frequency range of at least 450 Hz and higher, of at least 1 kHz or of at least 3 kHz and higher. Both speaker arrangements 14 and 16 may comprise a respective audio frequency range that possibly may, but is not required to, overlap.
The respective speaker arrangement 14 and/or 16 may comprise a membrane or other structures to move a fluid, e.g., a cantilever. According to an embodiment, the woofer may be based on a thermo-acoustic principle and the tweeter may be based on the mechanically actuated membrane or cantilever structure, wherein both may be actuated at the audio frequency.
The MEMS device 10 may comprise an electrical connector 18 configured for a connection with an external control circuitry. From the external control circuitry, the MEMS speaker device 10 may comprise signals that form a basis for audio signals 22, 24 respectively being emitting by the speaker set ups 14, 16, respectively.
The control circuitry 26 may be configured for deriving a control signal 34 from the input signal 28, the control signal 34 being adapted for the speaker arrangement 16. The control circuitry 26 may provide the control signal 32 to the speaker arrangement 16 to generate the acoustic waves 24. Although being described as generating and providing control signals for each of the speaker arrangements contained in the device 10′, the control circuitry 26 may provide for only a subset thereof, and may receive remaining control signals via a connector as described in connection with
When referring again to
Device 10 respectively may provide for a common housing for electrically connecting the speaker arrangement 14 and the speaker arrangement 16 to an environment of the device, e.g., containing a fluid to receive sound waves 22 and/or 24. The control circuitry 26 may comprise, for example, a processing unit, a microcontroller, an application-specific integrated circuit, ASIC, a field programmable gate array, FPGA, or other suitable circuitry, configured for controlling at least one of the speaker arrangements 14 and 16.
The ASIC 36, the control circuitry 26 respectively, may comprise a low pass filter 38 for deriving the control signal 32 having one or more channels. Control signal 32 may be considered as a woofer signal as containing information to drive a woofer. The ASIC 36, the control circuitry 26, respectively, may comprise a high pass filter 42 for deriving the control signal 34, which may be referred to as a tweeter signal having one or more channels.
The speaker arrangement 14 may be implemented as a MEMS woofer while speaker arrangement 16 may be implemented as a MEMS tweeter to generate acoustic waves 22 and 24 that may superimpose each other to an acoustic output signal 44, e.g., a full bandwidth acoustic audio signal.
The speaker arrangement 14 and/or the speaker arrangement 16 and/or optional additional speaker arrangements may be implemented as MEMS speakers. According to an embodiment, such MEMS speaker may comprise a membrane structure that deflects in-place or out-of-plane of a MEMS layer. According to an embodiment, the membrane structure deflects out-of-plane to generate pressure in a fluid. According to some embodiments, a membrane structure of a MEMS speaker, e.g., to generate low audio frequencies, e.g., as a woofer, may be driven with ultrasonic frequencies that are demodulated to the audible audio range for a listener. Some implementations of MEMS speaker arrangements in connection with embodiments are described in the following.
A combination of two speaker arrangements comprising same or different audio frequency ranges is described by way of non-limiting example and does not preclude MEMS devices that comprise at least a third speaker arrangement being configured for emitting sound in a third overlapping or disjoint audio frequency range, e.g., a midrange speaker and/or further speaker arrangements. A common back volume as described above, may, in case it is used, also be used for a third and possible further speaker arrangements. For example, as an alternative to speaker arrangement 14 or 16 or in addition hereto, a midrange speaker arrangement may be a part of a MEMs device described herein, e.g., MEMS device 20. For example, the control unit, e.g., ASIC 36, may comprise a bandpass filter adapted for frequency ranges operated by the midrange speaker arrangement.
The MEMS device 30 comprises a membrane structure 48 being mechanically connected to the substrate 46. The membrane structure 48 may be directly or indirectly hinged or connected to the substrate 46. The membrane structure 48 may be provided parallel to a substrate plane, e.g., it may be arranged in an unactuated state essentially parallel to a substrate plane x/y, i.e., in-plane. The membrane structure 48 may be deflectable out-of-plane, e.g., based on an actuation signal and/or based on a pressure of a fluid 52 being present in a cavity 54 of the MEMS device 30, of the substrate 46, respectively. The membrane structure 48 may be implemented as a planar structure having, for example, a rectangular, round or essentially square shape or a structure in between, e.g. alveolate. The membrane structure 48 may also be formed as a cantilever beam.
By way of non-limiting example only, a MEMS device may be formed from at least one wafer or other basis structure. Such a wafer may be considered as a plate-like structure that has a comparatively low thickness when compared to longitudinal extensions. Without limiting such considerations to a specific coordinate system or realization of a structure, the longitudinal directions may be considered as defining an in-plane direction of a MEMS device. Such directions are shown in
The membrane structure 48 is configured for deflecting along the z-direction with a frequency in ultra-sonic frequency range to cause a motion of the fluid 52. The motion may comprise a flow of the fluid 52 through a valve structure 56 and/or may relate to a pressure, a change thereof or a pressure wave generated in the cavity 54. For example, the membrane structure 48 may be configured for and controlled to deflect out-of-plane with an ultrasonic frequency. That is, the deflection of the membrane structure 48 may be controlled in a frequency range inaudible for a human. However, by use of a MEMS membrane structure that possibly has a comparatively small size and thus moves a small amount of fluid, a high rate of moving such small amounts may result in considerable fluid set under pressure, e.g., in a front volume. To avoid moving the fluid 52 back and forth with the membrane structure, the controllable valve structure may be used to allow, based on a control signal for the valve structure 56, a fluid pulse or fluid motion away from the membrane structure 48 through the valve structure 56 towards a front volume 74. In addition, the MEMS device 30 may provide for a back volume 75 on a different side of the membrane structure 48. The whole MEMS device 30 may thus offer a front and a back port for fluid and/or sound.
In some possible ways of operation, based on closing the valve structure 56 during a time the membrane structure 48 moves away from the valve structure, e.g., along +z, and again opening the valve structure 56 when the membrane structure 48 moves towards the valve structure 56 again, e.g., along −z, fluid pulses or fluid 52 may be accumulated in the front volume 74. The membrane structure may move or vibrate with an ultrasonic frequency, e.g. a frequency of at least 20 kHz, at least 30 kHz or even more up to several 100 kHz, i.e., with an ultrasonic frequency rage. For example, the membrane may vibrate with a frequency of at least kHz, at least 70 kHz or at least 90 kHz, e.g., approximately or equal to 96 kHz, wherein some structures may also allow for a frequency of at least 200 kHz, 300 kHz or up to 500 kHz or more to cover a range between at least 50 kHz and at most 500 kHz. Such an ultrasonic frequency range may be demodulated to an audible frequency range, i.e., an audio frequency range, e.g., below 20 kHz.
The valve structure 56 and the membrane structure 48 may together sandwich the cavity 54, wherein based on a control of valve structure 56 different fluidic resistances for the fluid may be provided. According to one example, the valve 56 may be switched between an open state in which the valve structure 56 basically provides for a low, negligible or no fluidic resistance and a second state, in which the valve structure 56 may be considered in a closed state in which the valve structure provides for a comparatively higher fluidic resistance for the fluid 52. For example, in the closed state, there may be no or only negligible flow from the fluid 52 through the valve structure 56.
The valve structure 56 may comprise a planar perforated structure 58 and a shutter structure 62 moveable with respect to the perforated structure 58. In one example, the perforated structure 58 may be an immoveable structure, e.g., a fixture or the like, for example, immovably connected to the substrate 46. However, according to other examples, both structures, the perforated structure 58 and the shutter structure 62 may be moveably arranged and may move with regard to each other.
The perforated structure 58 may comprise a plurality of openings 641 to 64n that allow the fluid 52 to pass through. According to an embodiment, the shutter structure 62 may comprise structural sections 661 to 66n that are adapted for an opposing position with regard to the openings 641 to 64n in the second position to provide for the second fluidic resistance.
By use of the valve structure 56, the ultrasonic waves in the cavity 54 may be transferred to other frequency ranges, e.g., an audible or audio frequency range.
While using a membrane being deflectable along a direction of movement 68 being possibly parallel to the z-direction, which may allow for a large amount of fluid to be moved, a direction of movement 72 of the valve structure 56, e.g., the shutter structure 62, may allow for a low thickness of the MEMS device 30, may comprise a control unit and/or an interface for a connection with an external control unit. Such a control unit may comprise control circuitry configured for controlling a deflection of the membrane structure 48 to deflect with a first ultrasonic frequency and for controlling the valve structure 56, e.g., an actuator structure connected to the shutter structure 62 to change between the first position and the second position with a same or a different second ultrasonic frequency to generate a sound pressure level in a front volume 74 of the MEMS device 30 in an audio frequency range, the sound pressure level in the audio frequency range being generated from the ultrasonic frequency of the membrane structure 48, i.e., by use of the valve structure 56, the membrane sound may be modulated or demodulated so as to obtain an audio signal. For example, such a demodulation/modulation may comprise an advanced digital sound reconstruction, ADSR, or other ultrasonic demodulation, UD, concepts.
MEMS device 40 comprises the control circuitry 26, e.g., comprising a processing unit, a microcontroller, an application-specific integrated circuit, ASIC, a field programmable gate array, FPGA, or other suitable circuitry, configured for controlling a deflection of the membrane structure 48. The control circuitry 26 may further be configured for controlling an actuator structure 76 connected to the shutter structure 62 to change between the first position shown in
By driving the membrane structure 48 and the valve structure 56 with a same or a different ultrasonic frequency, a modulation of the sound generated by the membrane structure 48 may be obtained.
A MEMS device in accordance with an embodiment may comprise a membrane structure 48 that comprises a plurality of ventilation holes 78 configured for a passage of the fluid 52 into the cavity 54 while preventing an acoustic short circuit. The ventilation holes 78 may have a synergetic effect and may, for example, first serve as holes that are now to etch a sacrificial layer to generate at least a part of the cavity 54. The ventilation holes 78 may comprise a comparatively low size along the x- and/or y-direction to prevent for an acoustic short circuit. That is, the ventilation holes 78 may have a high fluidic resistance with increases with ˜1/d4 wherein d refers to a hole diameter.
That is, the ventilation holes 78 may allow to remove the sacrificial layer without generating an acoustic short circuit. Such an acoustic short circuit may be understood as an effect that the membrane structure 48 deflects along a direction, but only provides for insufficient pressure or movement of fluid 52 as the fluidic resistance of the ventilation holes 78 is too low, such that the fluid 52 travels through such holes instead of being moved by the membrane structure. A size of the ventilation holes 78 may be tuned to achieve a fluidic resistance for the fluid 52 that is high enough to allow efficient flow generation through the valve structure 56 and to be low enough to allow for ventilation of the cavity 54 through the membrane structure 48 when the valve structure 56 is in a closed state, i.e., the shutter structure 62 is in the second position. A diameter of such a ventilation hole may be, for example, in a range of at least 0.5 μm and at most 5 μm, at least 0.7 μm and at most 4 μm or of at least 1 μm and at most 3 μm.
Alternatively, or in addition to the ventilation holes 78, the MEMS structure 40 and/or the MEMS structure 30 may comprise a bump structure 82 which may have a set of bumps, a continuous or discontinuous ring-like structure of at least one bump or the like that is arranged between the perforated structure 58 and the shutter structure 62. During manufacturing of the MEMS device 40, the bump structure 82 may, for example, be formed as a part of the perforated structure 58 and/or as a part of the shutter structure 62.
In a closed state of the valve structure 56, the bump structure 82 may prevent a fluid through the valve structure 56 based on a mechanical contact between the perforated structure 58 and the shutter structure 62 via the bump structure 82. That is, although showing a remaining distance between the bump structure 82 and the shutter structure 62, the MEMS device 40 of
According to an embodiment, the bump structure 82 comprises bump elements with different properties and/or for different purposes. For example, the bump elements 841 and 842 may comprise a comparatively long extension along the z-direction, i.e., they may be comparatively long. The bump elements 841 and 842 may be configured for providing a point-like contacting surface with the shutter structure 62 to provide for anti-stiction function. By having the bump elements 841, 842 with a point-like surface or at least a small contact area, good anti-stiction properties may be obtained. The bump elements 841 and/or 842 as an alternative or in addition allow to have a low amount of disturbing noise in the demodulated audio signal as a surface area that generates friction and thereby possibly noise when changing the position of the shutter structure 62 is small.
According to an embodiment, a MEMS device according to the present disclosure may provide for anti-stiction bumps between the perforated structure and the shutter structure and may comprise a sealing structure between the perforated structure and the shutter structure. A remaining gap in an area of the sealing structure may be larger when compared to a gap in an area of the anti-stiction bumps.
The bump structure 82 may alternatively or in addition comprise a continuous or segmented bump element 86 that may form at least a part of a ring through a respective opening 641, 642 respectively. When compared to the bump elements 841, 842, a length along the z-direction of bump elements 861, 862 may be smaller. A reduced length or height of bump elements 861, 862 when compared to bump elements may result, at least during regular operation, in that the bump elements 861, 862 do not provide for a mechanical contact but reduce or at least partly obstruct a slit along the z-direction, the slit being between the perforated structure 58 and the shutter structure 62. That is, elements 861 and 862 are not necessarily bumps but can also for a different type of protrusion or elevation.
To have different heights of bump elements used for different purposes may allow to maintain good anti-stiction properties by use of bump elements 841, 842 even in case of having a comparatively large surface provided by sealing bumps or sealing elevations 86 as they do not necessarily contribute to the anti-stiction functionality. A gap 881 remaining between bump elements 841 and shutter structure 62 may be comparatively low, down to zero in a case where the bumps abut the opposing structure. A gap 882 between the bump elements 861 or 862 on the one hand and shutter structure 62 on the other hand may, at a same time, be non-zero which may be interpreted as a remaining pinching slit even if the valve structure 56 is in a closed position. Such a gap may have a size, for example, of at least 100 nm and at most woo nm, of at least 200 nm and at most 700 nm or of at least 300 nm and at most 500 nm. A gap 883 between the shutter structure 62 and the perforated structure 58 may, at a same time, be in a range of at least 600 nm and at most 1500 nm. That is, bump elements 861 and 862 may provide to tighten or seal the cavity 54 even if a small gap 882 remains.
Bump structure 82 does not prevent bump elements 921 and/or 922 to be arranged between the membrane structure 48 and the valve structure 56. It has to be noted that the perforated structure 58 or the shutter structure 62 may be arranged closer to the membrane structure 48 when compared to the other structure.
Alternatively, or in addition to the bum structure 82 and/or the ventilation holes 78, the shutter structure 62 may comprise a mechanical stiffening 961, 962 configured for suppressing an out-of-plane deflection of the shutter structure 62. For example, the mechanical stiffening 961, 962 may comprise a locally increased thickness of the shutter structure 62, e.g., a beam-like structure or a bar-like structure. Alternatively, or in addition, an additional layer or structure may be arranged to locally stiffen the shutter structure to increase weight of the moved structure only as much as desired. Alternatively, or in addition to the stiffening of the perforated structure, wherein the shutter structure may comprise a mechanical stiffening, the mechanical stiffening configured for suppressing an out-of-plane deflection of the shutter structure.
Alternatively, or in addition, the MEMS device 50 may comprise a protective structure 102 which may also be arranged at MEMS device 30 and/or 40. The protective structure 102 may be transparent for a sound pressure level, e.g., in the audio range, of the fluid while being configured for mechanically protecting the valve structure 56. The protective structure 102 may sandwich the valve structure 56 together with the membrane structure, i.e., the valve structure 56 may be arranged between the membrane structure 48 and the protective structure 102. The protective structure 102 may comprise, for example, a plastic material, a semiconductor material and/or a glass material. For example, a plastic material, i.e., a membrane comprising the plastic material, may be well-suited to block ultrasonic sound while being transparent for audible frequencies. A glass structure forming at least a part of the protective structure 102 may comprise a mesh-like structure, may provide for a high mechanical robustness, and may comprise small openings that may at as ventilation holes.
The external or internal control circuitry may be configured for controlling the actuator structure 76 to move the shutter structure 62 into the first position or into the second position at an instance of time based on a deflection state of the membrane structure 48 at that instance of time. That is, the control circuitry may temporally align a control of the membrane structure 48 and of the shutter structure 62. For example, the control circuitry may control the actuator structure 76 so as to provide for the first position of the valve structure at a time when the membrane provides for pressure in the cavity or may provide for a closed state of the valve structure 56 at this time. For example, the control circuitry 26 may be configured for controlling the actuator structure 76 and the membrane structure 48 for aggregating a fluidic pressure of the fluid motion generated by the membrane structure 48 to have an aggregated pressure in the front volume by use of the valve structure. In other words, the membrane structure 48 may aggregate pressure, e.g., by pumping a contribution in the front volume while having the valve structure 56 in an open state and the valve structure 56 may be controlled into a closed state when the membrane 48 moves back again. According to other types of ultrasonic demodulation, e.g., ADSR, the membrane structure on the one hand and the shutter position on the other hand may also be unsynchronized.
As shown, for example, in
In particular, a layer of the shutter structure 62 is shown. A two-dimensional layout of the structural section 66 of the shutter structure 62 is shown, leading also to a two-dimensional arrangement of openings 132 that may overlap openings 64 of a perforated structure in the first state. One or more spring structures 1331 to 1334 may form a part of the MEMS device 60. The at least one spring structure 1331 to 1334 may be formed, for example, as a ridge or other type of spring that may allow to move the shutter structure 62 along the x- and/or y-direction while preventing such a movement, for example, along a z-direction. A geometry of spring structures 1331 to 1334 may also restrict a movement of the shutter structure 62 along one of the directions x and y while facilitating the movement along the other direction, e.g., the direction x along which the actuator structure 76 may generate a force so as to deflect the shutter structure 62. That is, the spring structure may, at least in the combination of spring elements, comprise an out-of-plane mechanical stiffness along the z direction being larger when compared to an in-plane mechanical stiffness along the direction of movement 72.
The spring structures 1331 to 1334 may elastically hinge the shutter structure 62, e.g., at the substrate 46 and/or at the stator or perforated structure 58 in a rest position, the actuator structure 76 configured for deflecting the shutter structure 62 in-plane along a direction of movement, e.g., x, and out of the rest position.
An extension 134 of the shutter structure 62 along x and/or y may be, for example, in a range of at least 500 μm and some millimeter, e.g., around 1 mm. A length 135 of the spring structures 1331 to 1334 may be in a range of at least 50 μm and at most 300 μm, at least 70 μm and at most 200 μm or at least 90 μm and at most 150 μm, e.g., 100 μm. Those dimensions are example values only as well as the number of spring structures 133. For example, one, two, three or more than four spring structures 133 may be arranged, e.g., six, eight, nine or more. Alternatively, or in addition, the structural extensions may comprise any other value.
As may be seen from
Based on spring structures 133, 133′ and/or a combination thereof which forms also an embodiment, the shutter structure 62 and the at least one spring structure may form at least a part of a resonator having a resonance frequency, said resonance frequency being in the ultrasonic frequency range of, for example, at least 20 kHz, at least 30 kHz, at least 40 kHz or more.
As is described, for example, in connection with
This may result in different frequencies of movement for the resonator structures 621 to 624 in response to a respective control signal having the intended frequency or being of a broadband characteristic so as to excite resonant movement of one, more or all of the resonator structures.
This may allow generation of more than a single tone or frequency component with the MEMS structure at a time.
In acoustic communication with a single membrane structure 48, an arrangement of valve structures 56a1 to 56d4 may be arranged in four lines and four columns. This does not exclude having a second, further membrane structure in acoustic communication with additional valve structures and/or to have a different number of valve structures, a different number of lines and/or a different number of columns of valve structures in communication with the membrane structure 48. For example, valve structures 56a1 to 56a4 may be formed so as to comprise a same resonance frequency, e.g., based on spring structures. Valve elements 56b1 to 56b4 may comprise a different second resonance frequency while valve structures 56c1 to 56c4 and 56d1 to 56d4 may comprise a third and fourth resonance frequency. Based on a suitable control signal, this may allow to contribute with different spectra to the audible signal, e.g., for the ultrasonic demodulation being implemented in the MEMS device. A use of one, two, three or four of the respective valve structure 56a, 56b, 56c or 56d may allow to increase or reduce a sound pressure contribution of said frequency, while a deactivation of all of the respective valve structures having a resonance frequency may lead to an absence of said spectrum. As described, such a MEMS device may be configured for a use with an ultrasonic demodulation concept, e.g., to individually operate different valve structures in communication with a same membrane with different operation frequencies.
Such a structure may allow for a detailed controlled of the generated output. For example, the membrane may be operated at a resonance frequency thereof and valve structures may be operated at a resonance frequency thereof. A vibration or movement of the shutter structure of different rows may be operated in resonance each and with a phase shift of 90° with regard to one another to emulate the analog sound. An amplitude of the sound may be adapted via a parallel path having a further shutter structure.
In view of the above, at least the speaker arrangement 14 may be configured as an ultrasonic demodulation speaker. Such a configuration is shown in
The MEMS device no may comprise speaker arrangements 14 and 16 that may share back volume 75 as a common back volume. For example, a housing of the MEMS device no or of other MEMS devices described herein may provide for a common back volume for the first speaker arrangement and the second speaker arrangement.
The MEMS device no may comprise the speaker arrangement 14, e.g., to form a part of a MEMS package described herein, e.g., a woofer part. Therein, the membrane structure 48 may deflect so as to generate pressure in cavity 54. A shutter structure of valve structure 56 may be realized, for example, in accordance with MEMS device 30 shown in
When referring again to
The MEMS device no may comprise a single or more than a single actuator, e.g., actuator structures 761 and 762 and/or possible further actuator structures so as to generate active forces along positive and negative directions of movement 72. This may allow for a highly controllable generation of sound when compared to relying on restoring forces of springs only.
An example of a possible implementation of the valve structures is shown in the schematic top view of
The speaker arrangements 14 and 16 may be formed on a same die, e.g., silicon substrate that may, without any limitation, also be formed on separate dies that are combined with each other within the respective package.
As shown in
As shown, for example, in
As shown, for example, in
One or more valve structures 56 may be arranged so as to sandwich the cavity together with the membrane structure 48, wherein the valve structure may comprise a planar perforated structure 58 and a shutter structure 62 arranged moveable in-plane and with a frequency in the ultrasonic frequency range and with regard to the substrate plane and between a first position and second position. That is, the shutter structure 62 may be moved in parallel to a layer parallel to the longitudinal directions x/y. The shutter structure 26 may be arranged to provide a first fluidic resistance, e.g., to enable the fluid flow, for the fluid in the first position and a second, higher fluidic resistance, e.g., to at least partly block the fluid flow, for the fluid in the second position.
According to an embodiment, the speaker arrangement 12 comprises a thermoelectrical speaker, e.g., a membrane structure that is deflectable based on a thermoelectric concept or thermoelectric principle. Such an actuator may operate in accordance with a principle to actuate a photoacoustic sensor. According to embodiments, a micro audio speaker module may comprise a combination of MEMS tweeter and a MEMS woofer in one assembly including an ASIC that provides the appropriate voltage levels and signal preconditioning for the tweeter and woofer. However, the ASIC may also be an external component. According to an embodiment, as module described herein may be implemented that the woofer is based on an ultrasonic demodulation principle like ADSR, a single or a dual side band modulation and/or the tweeter may be based on an analog audio frequency mechanically actuated membrane or cantilever structure.
In
According to an embodiment, the different speaker arrangements 14 and 16 being part of a MEMS device described herein, may not only operate in different audio frequency ranges but may also operate based on different principles. For example, while a speaker arrangement may operate based on a thermoelectric actuation, e.g., in combination with electrodynamic actuators to drive the valves, a different speaker arrangement may operate based on a piezoelectric actuator. That is, not only the structure but also the actuator principle may differ between the speaker arrangements. As an alternative or in addition, the principle of generating the audio frequency range may also differ. While speaker arrangement 16 described herein may generate the audible frequency range itself by use of the membrane, the lower frequencies, e.g., of speaker setup 14, may benefit from an additional valve structure to allow some sort of pump mechanism in the front volume to aggregate pressure level.
According to embodiments, the ASIC and the MEMS may be assembled in one housing. Alternatively, the MEMs may be assembled in one housing and the ASIC may even be part of an external system, e.g., a system-on-a-chip SoC. As an alternative, the MEMS woofer and MEMS tweeter may be integrated on the same substrate or die. As an alternative hereto, the MEMS woofer and MEMS tweeter may even be integrated on separate substrates or dies.
Embodiments relate to the finding that the combination of two micro speaker concepts that have their respective sweet-spot in different frequency ranges may be used to cover a larger, e.g., anti-audio band with a high sound pressure level and a high efficiency. A particular combination of an ultrasonic, pump based woofer, e.g., using an ultrasound demodulation like ADSR, a single-sideband demodulation or dual-sideband demodulation techniques with an analog tweeter as well as a thermos-acoustic woofer in combination with an analog tweeter. These considerations support both, a single die integration or a dual die solution.
Some embodiments in accordance with the present disclosure are described in the following:
According to a first aspect, a MEMS device comprises:
According to a second aspect making reference to aspect 1, the first speaker arrangement is configured as woofer; and wherein the second speaker arrangement is configured as a tweeter.
According to a third aspect making reference to aspect 1 or 2, the MEMS device comprises a housing that provides for a common back volume for the first speaker arrangement and the second speaker arrangement, in particular wherein the housing is arranged to further provide for electrically connecting the first speaker arrangement and the second speaker arrangement to an environment of the package.
According to a fourth aspect making reference to one of previous aspect, the first speaker arrangement and the second speaker arrangement are formed on a same die.
According to a fifth aspect making reference to one of aspects 1 to 4, the MEMS device comprises control circuitry configured for receiving an input signal comprising audio information; and wherein the control circuitry is configured for deriving a first control signal from the input signal, the first input signal adapted for the first speaker arrangement; and for providing the first control signal to the first speaker arrangement; and wherein the control circuitry is configured for deriving a second control signal from the input signal, the second input signal adapted for the second speaker arrangement; and for providing the second control signal to the second speaker arrangement.
According to a sixth aspect making reference to aspect 5, the control circuitry comprises a lowpass filter for the deriving the first control signal and comprises a highpass filter for the deriving the second control signal.
According to a seventh aspect making reference to one of aspects 1 to 4, the MEMS device comprises an electrical connector configured for a connection with an external control circuitry.
According to an eighth aspect making reference to one of aspects 1 to 7, at least the first speaker arrangement is configured as ultrasonic demodulation speaker.
According to a ninth aspect making reference to aspect 8, the first speaker arrangement comprises a membrane structure one a first side of a plurality of substrate cavities being adjacently arranged; wherein the first speaker arrangement comprises a corresponding plurality of valve structures on a second side of the plurality of cavities; wherein the MEMS device is configured for operating each valve structure at an individual frequency; wherein the plurality of valve structures is configured for commonly providing the first audio frequency range from a fluid motion generated by the membrane structure.
According to a tenth aspect making reference to one of previous aspects, the first speaker arrangement comprises:
According to an eleventh aspect making reference to aspect 10, the MEMS device comprises a spring structure elastically hinging the shutter structure at the substrate structure in a rest position; and comprising an actuator structure configured for deflecting the shutter structure in-plane along a direction of movement and out of the rest position.
According to a twelfth aspect making reference to aspect 10 or 11, the MEMS device comprises a bump structure between the perforated structure and the shutter structure, the bump structure configured for adjusting a minimum distance between the perforated structure and the shutter structure.
According to a thirteenth aspect making reference to one of aspects 1 to 7, the first speaker arrangement comprises a thermoelectrical speaker.
According to a fourteenth aspect making reference to one of previous aspects, the second speaker arrangement comprises at least one piezoelectrically driven membrane structure configured for generating the sound in the first audio frequency range.
According to a fifteenth aspect an audio device comprises a MEMS device according to one of previous aspects and configured for providing acoustic sound based on the first audio frequency range and based on the second audio frequency range.
Although some aspects have been described in the context of an apparatus, it is clear that these aspects also represent a description of the corresponding method, where a block or device corresponds to a method step or a feature of a method step. Analogously, aspects described in the context of a method step also represent a description of a corresponding block or item or feature of a corresponding apparatus.
The above described embodiments are merely illustrative for the principles of the present disclosure. It is understood that modifications and variations of the arrangements and the details described herein will be apparent to others skilled in the art. It is the intent, therefore, to be limited only by the scope of the impending patent claims and not by the specific details presented by way of description and explanation of the embodiments herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 22179664 | Jun 2022 | EP | regional |
