Abstract:
A miniature rangefinder includes a housing, a micromachined ultrasonic transducer, and signal processing circuitry. The housing includes a substrate and a lid. The housing has one or more apertures and the micromachined ultrasonic transducer is mounted over an aperture. The micromachined ultrasonic transducer may function as both a transmitter and a receiver. An integrated circuit is configured to drive the transducer to transmit an acoustic signal, detect a return signal, and determine a time of flight between emitting the acoustic signal and detecting the return signal.

Description:
CLAIM OF PRIORITY 
       [0001]    This application is a continuation of International Patent Application Number PCT/US2015/043256 filed Jul. 31, 2015, the entire disclosures of which are incorporated herein by reference. International Patent Application Number PCT/US2015/043256 claims the priority benefit of U.S. Provisional Patent Application No. 62/032,041, filed Aug. 1, 2014, the entire disclosures of which are incorporated by reference. 
     
    
     NOTICE OF MATERIAL SUBJECT TO COPYRIGHT PROTECTION 
       [0002]    A portion of the material in this patent document is subject to copyright protection under the copyright laws of the United States and of other countries. The owner of the copyright rights has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the United States Patent and Trademark Office publicly available file or records, but otherwise reserves all copyright rights whatsoever. The copyright owner does not hereby waive any of its rights to have this patent document maintained in secrecy, including without limitation its rights pursuant to 37 C.F.R.§1.14. 
       BACKGROUND OF THE INVENTION 
       [0003]    Proximity sensors are used in a variety of consumer electronic devices, including in cell phones. In cell phones, the proximity sensor is used to detect when the user places the phone near their ear so that the touch screen can be disabled. Existing sensors for this application are optical proximity sensors, based on an infrared (IR) light emitting diode (LED) and one or more photodetectors. A typical proximity sensor (such as the Avago APDS-9950, Taos TMD2771, Capella Microsystems CM36683P) functions by detecting the intensity of IR light reflected from an object. The proximity sensor indicates when an object is near the sensor, typically within 100 mm+/−20 mm of the sensor, when the reflected IR level crosses a pre-determined threshold. 
         [0004]    These proximity sensors suffer from a number of limitations. The first is that reflected IR intensity is a poor measure of proximity: the IR light reflected from two objects at the same distance will depend on the size and color of the object. This problem is very evident to cell phone users with dark hair and/or skin, who often find that their cell phone display and touch screen do not properly disable when they use the phone. A second problem is the high power required by the LED source, which can consume more than 10 milliwatts (mW). The stand-by power consumption of a typical cell phone is approximately 50 mW so the proximity sensor must be turned off most of the time to avoid draining the battery. A third problem is that optical proximity sensors can detect objects only over a limited range (approximately 100 mm). For applications in tablets, notebook computers, and monitors, it is desirable to be able to detect objects over a longer range (up to 600 mm or more). Finally, many applications require an accurate measure of distance (e.g. to the user&#39;s hand or head) that current optical proximity sensors simply cannot provide. 
         [0005]    Accordingly, what is needed is a proximity sensor that provides an accurate measurement of the distance to an object, independent of the color or size of the object, that is low power (ideally below 1 mW), and that can operate at both short ranges (1 cm) and long range (&gt;10 cm). 
       BRIEF SUMMARY OF THE DISCLOSURE 
       [0006]    Aspects of the present disclosure generally relate to ultrasonic rangefinders and proximity sensors. In various implementations, an ultrasonic rangefinder may include a housing containing a micromachined ultrasonic transducer and an application specific integrated circuit (ASIC). In various implementations, the rangefinder may have a digital serial interface and an interrupt pin that is used to signal when an object is detected within a predetermined range of the rangefinder. The serial interface allows the end user to program the predetermined range, to read out the range of a detected object, and configure various aspects of the rangefinder. The rangefinder may be used in proximity sensing applications such as in consumer electronics. Multiple rangefinders may be used together to allow triangulation of object location in three-dimensional space. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
         [0007]    The invention will be more fully understood by reference to the following drawings which are for illustrative purposes only: 
           [0008]      FIGS. 1A-B  illustrates the operation of the ultrasonic rangefinder, according to various aspects of the present disclosure. 
           [0009]      FIG. 2  is a cross section view of a rangefinder according to an aspect of the present disclosure. 
           [0010]      FIG. 3  is a bottom view of a rangefinder according to an aspect of the present disclosure. 
           [0011]      FIG. 4A  is a top view of a micromachined ultrasonic transducer according to an aspect of the present disclosure. 
           [0012]      FIG. 4B  is a cutaway cross-section perspective view of the micromachined ultrasonic transducer of  FIG. 4A  taken along line A-A of  FIG. 4A . 
           [0013]      FIG. 5  is a block diagram of an embodiment of an electronic assembly containing a rangefinder according to an aspect of the present disclosure. 
           [0014]      FIG. 6  is a block diagram of an embodiment of an ultrasonic rangefinder according to an aspect of the present disclosure. 
           [0015]      FIG. 7  is a state diagram illustrating a method for operating an ultrasonic rangefinder according to an aspect of the present disclosure. 
           [0016]      FIG. 8  is a cross section view of an alternative implementation of a rangefinder according to an aspect of the present disclosure. 
           [0017]      FIG. 9  is a cross section view of a yet another implementation of a rangefinder according to an aspect of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    Although the description herein contains many details, these should not be construed as limiting the scope of the claimed invention but as merely providing illustrations of some of the aspects of the present disclosure. Therefore, it will be appreciated that the scope of the present invention fully encompasses other implementations which may appreciated by those skilled in the art. 
         [0019]    According to an aspect of the present disclosure an ultrasonic rangefinder may include a micromachined ultrasonic transducer (MUT) and an application specific integrated circuit (ASIC) packaged together in a small housing similar to that of a micro-electromechanical systems (MEMS) microphone. It will be appreciated that the following embodiments are provided by way of example only, and that numerous variations and modifications are possible. For example, while an implementation is shown having an acoustic port in the bottom of the housing, the acoustic port may have other locations, such as in the top of the housing. All such variations that would be apparent to one of ordinary skill in the art are intended to fall within the scope of this disclosure. It will also be appreciated that the drawings are not necessarily to scale, with emphasis being instead on the distinguishing features of the rangefinder device disclosed herein. 
         [0020]    Benefits of the present subject matter include, but are not limited to: 1) a rangefinder that can measure the range to an object using ultrasonic time-of-flight rather than simple reflected intensity and therefore provides a much more accurate measurement than existing optical proximity sensors; 2) the ultrasonic time-of-flight measurement is not sensitive to the color of an object, unlike existing optical proximity sensors, therefore it provides a more consistent measurement of range and proximity across a wide range of objects; 3) an ultrasound transducer consumes far less power than a light source of the type used in an optical proximity sensor; 4) the integrated circuit electronics provide a simple digital interface making the sensor much easier to use than existing ultrasonic sensors; 5) the integrated circuit electronics may incorporate a charge-pump so that the rangefinder requires only a low-voltage power supply input; 6) the ultrasonic rangefinder may serve as both a transmitter and a receiver of ultrasound, eliminating the need for separate transmitter and receiver devices; 7) the ultrasonic rangefinder has a lower manufacturing cost than other ultrasonic sensors. 
         [0021]      FIGS. 1A-B  illustrate the operation of an ultrasonic rangefinder  10  according to various aspects of the present disclosure. The rangefinder  10  transmits a pulse of ultrasound  14 . An object  12  approaching the rangefinder  10  is detected based on a reflected echo  16  when the original ultrasound pulse  14  is reflected from object  12 . The time-of-flight (ToF), which is the time elapsed from transmitting the original pulse  14  to receiving the reflected echo  16 , is used to detect the range of object  12  from the rangefinder  10 . Using the known value of the speed of sound, c, the range is computed as range=ToF*c/2. While  FIGS. 1A-B  show a single object  12 , multiple objects having different ranges from the rangefinder  10  may also be detected. 
         [0022]      FIG. 2  illustrates a cross-section view of an embodiment of the ultrasonic rangefinder. The rangefinder includes a substrate  18 , a micromachined ultrasonic transducer (MUT)  20 , an application specific integrated circuit  22  and a lid  24 . The substrate  18  may be composed of a laminate material similar to that commonly used in the packaging of MEMS microphones. Many materials may be used for lid  24 , including laminate, plastic or metal. By way of example, and not by way of limitation, the integrated circuit (IC)  22  may be an application specific integrated circuit (ASIC). As is generally understood by those skilled in the art, the term ASIC generally refers to an IC customized for a particular use, rather than intended for general-purpose use. An ASIC is sometimes referred to as a system-on-chip (SoC). Examples of ASIC designs include standard cell, gate array, such as field programmable gate array (FPGA), full custom, and structured. 
         [0023]    An acoustic aperture or port  26  may be located beneath MUT  20  so that port  26  is aligned beneath a cavity or pipe  28  formed in MUT  20 . The diameter  30  and length  34  of pipe  28  and the diameter  32  and length  26  of port  26  may be dimensioned such that port  26  and pipe  28  form an acoustic resonator in order to enhance the acoustic performance of the MUT. For a given operating frequency f, the resonance condition occurs when the effective length of the acoustic resonator Le is equal to an odd multiple of one-quarter wavelength, L e =n*λ/4, where n=1, 3, 5, . . . is an odd integer and λ=c/f is the acoustic wavelength of sound with speed c and frequency f. The effective length L e  is the sum of pipe length  34  and port length  36  plus a correction factor α determined by pipe diameter  30  and port diameter  32 . For a circular port with approximately equal pipe diameter  30  and port diameter  32 , the correction factor is approximately equal to α=0.35*D, where D is the diameter of both port  26  and pipe  28 . For other geometries, the correction factor α may range from 0.25 to 0.7. In some embodiments, the acoustic resonator may include an acoustic tube within a product into which the rangefinder  10  is incorporated. By way of example, and not by way of limitation, a cylindrical hole may be drilled through the cover glass or housing of the product. In this case, the length of the acoustic resonator is the sum of port  26  in substrate  18 , pipe  28  in MUT  20  and the length of the acoustic tube in the cover glass or housing. 
         [0024]    The height  38  of the rangefinder is typically from 0.4 mm to 3 mm, and specifically may range from 0.5 mm to 1.5 mm and more specifically from 0.7 mm to 1.3 mm. Considering the internal dimensions, the gap  40  between the top of MUT  20  and the lid  24  is chosen so that it sound reflecting from lid  24  does not degrade the acoustic performance of the rangefinder. As an illustration, for a MUT operating at 200 kHz, the acoustic wavelength is λ=1.7 mm and gap  40  is chosen to be less than λ/4=0.43 mm. Alternatively, the gap  40  may be chosen to maximize the bandwidth of MUT  20  by setting the gap  40  to increase the damping incurred due to the sound reflecting from lid  24 . 
         [0025]      FIG. 3  illustrates a bottom view of an embodiment of the rangefinder. Substrate  18  contains a plurality of electrical contact pads  42  that provide electrical connection to the MUT and ASIC. The acoustic port  26  is surrounded by a sealing ring  44  which may be attached to the end users circuit board using a solder reflow process. The signals carried on contact pads  42  may include power, ground, an interrupt pin and a digital serial interface, for example serial peripheral interface (SPI) or inter-integrated circuit (I2C). The following table illustrates an example of the signals carried on contact pads  42  in the case of an I2C serial interface: 
         [0000]    
       
         
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Signal 
                 Description 
               
               
                   
                   
               
             
             
               
                   
                 VDD 
                 Power supply voltage. 
               
               
                   
                 GND 
                 Ground 
               
               
                   
                 SCL 
                 Serial-data clock for I2C interface 
               
               
                   
                 SDA 
                 Serial data I/O terminal for I2C interface 
               
               
                   
                 INT 
                 Interrupt pin 
               
               
                   
                   
               
             
          
         
       
     
         [0026]      FIG. 4A  shows a top view of one embodiment of micromachined ultrasonic transducer (MUT)  20 .  FIG. 4B  shows a cross-section view of one embodiment of MUT  20 , corresponding to a cross-section cut through line AA in  FIG. 4A . Various types of MUTs have been demonstrated, among which are capacitive MUTs (CMUTs) and piezoelectric MUTs (PMUTs). Each type of MUT consists of a thin diaphragm or membrane  46 . The CMUT and PMUT differ in the method used to provide electrical transduction of the membrane vibration: in a CMUT, capacitive transduction is used, whereas in a PMUT piezoelectric transduction is used.  FIGS. 4A-4B  show a PMUT with a ring of piezoelectric material  52  spanning the perimeter of membrane  46 . A top electrode  48  and bottom electrode  50  provide electrical contacts to piezoelectric ring  52  which transduces vibration of membrane  46  into an electrical signal. When the MUT functions as a transmitter, an electrical signal applied between electrode  48  and electrode  50  produces vibration of membrane  46 , launching an acoustic pressure wave. When the MUT functions as a receiver, an acoustic pressure wave incident on membrane  46  induces membrane vibration, producing a measurable electrical signal on electrodes  48  and  50 . 
         [0027]    In the implementation shown in  FIGS. 4A-4B , membrane  46  is formed of a thin passive layer  54  deposited on the surface of a MUT substrate  56 . Various materials such as silicon, silicon dioxide, silicon nitride, may be used to form passive layer  54 . The MUT substrate  56  may be made of silicon or other materials such as glass. A pipe-like resonant cavity  28  is etched into the MUT substrate  56  to release membrane  46 . When substrate  56  is silicon, cavity  28  may be etched using deep reactive ion etching (DRIE). The thickness of the MUT substrate  56  determines the length  34  of pipe  28 , and the diameter  30  of cavity  28  is determined by the DRIE process.  FIGS. 4A-B  show a circular cavity  28  and membrane  46 , however many other configurations including square, hexagonal, and rectangular are possible. The diameter of cavity  28  is shown to be the same as the diameter of membrane  46 , however cavity  28  may be either smaller or larger than membrane  46 . 
         [0028]    According to aspects of the present disclosure an acoustic rangefinder apparatus of the type described herein may incorporate a charge-pump to convert the input supply voltage to a higher voltage used to transmit ultrasound. The rangefinder apparatus may also include a digital serial interface that allows the end user to program minimum and maximum range thresholds. When an object is detected within the range thresholds, the rangefinder sets one of the digital outputs to a high level, thereby indicating that an object has been detected within range. The end user may also read the range to an object through a digital serial interface. 
         [0029]    Further details are provided regarding the rangefinder electronic sub-assembly. In the embodiment of  FIG. 5 , all of the blocks except the MUT  20  are contained in an ASIC assembly  22  which controls the rangefinding measurement. It will be appreciated that the ASIC assembly  22  may comprise a single integrated circuit or several integrated circuits, and may include additional discrete components. 
         [0030]    In the implementation depicted in  FIG. 5 , a measurement cycle begins with the generation of a transmit pulse by signal generation block  200 . A programmable charge pump  226  boosts the input power supply voltage, which is in the range of 1V to 5V, to a transmit voltage level, which is in the range of 1.8V to 100V, and more specifically in the range 5V to 32V. Programmable charge pump  226  may also supply bias voltage to transducer  20 . Amplifier  202  transmits a signal through closed transmit switch  204  to actuate micromachined ultrasound transducer  20 , which emits a sound pulse. Amplifier  202  may be configured to operate in a non-linear fashion. 
         [0031]    After a transmit duration in the range of 10 microseconds to 30 milliseconds, and more specifically in the range of 50 microseconds to 1 millisecond, transmit switch  204  is opened and receive switch  210  is closed. An echo signal received by transducer  20  is amplified by amplifier  212  and demodulated and filtered by mixer and filter block  214 . In the illustrated implementation, a phase-insensitive demodulator is used. A designer skilled in the art will appreciate that a complex demodulator which demodulates the in-phase and quadrature components of the received echo signal may be used instead. The receive cycle lasts between 100 microseconds and 50 milliseconds, and more specifically in the range of 200 microseconds to 10 milliseconds. 
         [0032]    Comparator  218  compares the demodulated echo signal with a threshold set by a digital to analog converter  216 . The output of comparator  218  may be used in several modes. In a first mode, a programmable digital timer  222  uses a programmable clock  228  to accumulate the time since the start of the transmit pulse. The programmable digital timer  222  is configured to load its count value into output registers  224  when the comparator  218  transitions from low to high, signaling the reception of an echo. The programmable digital timer may be configured to only load its count value into output registers  224  when the count value is between a certain high and low threshold, signaling that an object is within a pre-programmed range. The programmable digital timer  222  may trigger an external interrupt for the purposes of waking up an external device. 
         [0033]    In a second mode, the output of comparator  218  may be used by successive approximation register (SAR) logic  220  to reconfigure the digital to analog converter (DAC)  216  to provide a better approximation of the value of the echo signal. In this way a high resolution sample of the echo signal may be stored. The comparator  218  may be preceded by a sample and hold block (not shown) which may be used to sample the signal periodically and convert the analog signal to a corresponding digital value. The sampling rate for this analog-to-digital conversion process may be in a range of, e.g., 1 kHz to 100 kHz, and more specifically 4 kHz to 40 kHz. The SAR logic  220  reconfigures the DAC  216  between 4 to 16 times per sample, providing between 4 to 16 bits resolution, and more specifically, 8 to 12 bits. This digital representation of the echo signal is stored in a memory, e.g., output registers  224 . During the measurement, output signal  234  may be used to signal a wakeup event, to output range data, or to output echo signal data. 
         [0034]    A configuration signal  232  from an external electronic device configures configuration registers  230  which control the various blocks in the design, including but not limited to blocks  200 ,  226 ,  204 ,  210 ,  212 ,  214 ,  220 ,  216 , and  222 . A programmable clock  228  provides a stable reference clock to blocks including but not limited to signal generation block  200 , programmable charge pump  226 , transmit switch  204 , receive switch  210 , amplifier  212 , mixer and filter block  214 , DAC  216 , SAR logic  220 , comparator  218 , programmable digital timer  222 , and output registers  224 . The clock  228  is used to time and transition between transmit, receive, and idle states of the rangefinder. An analog reference  234  provides analog reference signals to blocks including but not limited to programmable charge pump  226 , amplifier  212 , mixer and filter block  214 , comparator  218 , and DAC  216 . 
         [0035]    In the implementation shown in  FIG. 6 , a rangefinder  140 , which may be configured as described above with respect to  FIG. 2  through  FIG. 5 , may be part of an electronic assembly  154  that contains a microprocessor  142 , a radio transceiver  146 , a memory  148  and several peripherals  144 ,  150 . The rangefinder  140  may be connected through a shared bus  152 , which is shared with additional peripheral(s)  144 . By way of example, and not by way of limitation, the ASIC  22  may be coupled to the shared bus  152 . The rangefinder  140  may be configured to perform a range measurement periodically with a period between e.g., 1 msec and 10 sec, or more specifically, a period between 10 msec and 1 sec. The other components on the electronic assembly  154  are configured to be in a low-power state. Because the rangefinder  140  can be operated in a low power consumption mode, it will be appreciated that rangefinder  140  can act as a wakeup switch for electronic assembly  154 . When rangefinder  140  detects an object that enters or exits a predefined span of range, it can signal other components on the electronic assembly to wake and enter a higher power state. 
         [0036]    In one implementation, the rangefinder  140  may be configured to detect objects within a certain range. On detection of an object, the rangefinder wakes microprocessor  142  which transmits a signal through a channel  164  using the radio transceiver  146 . The signal is received by another radio transceiver  156  on an electronic assembly  158 , causing microprocessor  160  to trigger peripheral  162  to perform a useful action. It will be appreciated by a designer skilled in the art that similar embodiments can be used to trigger different actions by different peripheral(s)  162 . This may include replacing radio  146 , channel  164 , and transceiver  156  with a wired serial connection or an optical or infrared signaling device. It should be appreciated that in some cases transceiver  146  may be operated as a transmitter only and transceiver  156  may be operated as a receiver only. 
         [0037]    Further details are now provided regarding the operation of the various states of the rangefinder. In the method of operation shown in  FIG. 7 , the rangefinder is in start state  100  at power up. After a transition period  118 , the rangefinder enters a sleep state  102  wherein most of the electronic circuitry is powered down. For example, in  FIG. 5 , signal generation block  200 , amplifier  202 , programmable charge pump  226 , transmit switch  204 , receive switch  210 , amplifier  212 , mixer and filter block  214 , DAC  216 , comparator  218 , programmable digital timer  222 , output registers  224 , SAR logic  220  and/or output signal  234  may be configured to be off or in a low-power state. 
         [0038]    An external device or factory programming may cause the rangefinder to transition  120  into a proximity state  104  or to transition  124  into a range measurement state  108 . A sleep signal  122  may cause the rangefinder to transition to the sleep state  102 . 
         [0039]    In the proximity state  104 , a proximity measurement is performed. If a target is detected within predefined limits  130 , a wakeup interrupt  110  is emitted. The rangefinder may also output the measured range. For example, in  FIG. 6 , the rangefinder  140  may wake the microprocessor  142 , which may perform different actions based on the measured range, such as transmitting a signal using radio  146 . After performing a measurement in the proximity state  104  for a programmable time period, the rangefinder enters an idle state  106 . During idle state  106 , several blocks may be powered down. After a programmable time period, a clock trigger  128  causes the rangefinder to re-enter the proximity state  104  and repeat the measurement. 
         [0040]    During the idle state  106 , an external input  134  causes the rangefinder to enter the range measurement state  108 . 
         [0041]    During the range measurement state  108 , the rangefinder outputs the range to the target(s). It may also be configured to output a digitized version of the echo signal recorded by the rangefinder. Following the range measurement state  108 , the rangefinder enters the idle state  106 . After a programmable time period, clock trigger  134  causes the rangefinder to re-enter range measurement state  108  and repeat the measurement. 
         [0042]    In one embodiment, multiple rangefinders may be used together to determine the position of an object in multiple dimensions. For example, two rangefinders placed in opposite corners of a device such as a tablet, laptop, or monitor, could be used to determine the z-axis range and x-axis position of an object. Similarly, three rangefinders could be used to triangulate the x, y, and z position of an object. 
         [0043]    When multiple rangefinders are used together, it may be desirable to allow the rangefinders to work together in coordination, for example to avoid collisions between sound pulses that are transmitted at the same time. In such an application, the rangefinders may be configured to perform a “discovery” operation on power up, similar to that used in networking, wherein one rangefinder transmits a pulse of sound and waits for a predetermined interval to receive a responding pulse from a second rangefinder. Upon receipt of the first pulse of sound, the second rangefinder transmits a responding pulse. The responding pulse may be encoded to distinguish the response from echoes originating from the first pulse. This procedure may continue until all rangefinders have been enumerated, after which each rangefinder is configured to conduct range measurements in a time-division multiplexed (TDM) fashion, wherein the first rangefinder conducts a measurement in a predetermined time-slot, followed by the second rangefinder, and so on until all measurements have been completed. If during the “discovery” phase two rangefinders transmit at the same time, resulting in a collision, each rangefinder waits a randomly generated amount of time before re-transmitting a pulse, in a manner similar to the Ethernet protocol. Such a procedure may be implemented through appropriate programming, which may be implemented, e.g., by the Microprocessor  142  shown in  FIG. 6 . 
         [0044]    In the embodiment illustrated in  FIG. 2  and  FIG. 3 , the acoustic port  26  and electrical contacts  42  are located on the substrate  18 . However, alternative embodiments are possible. In a second embodiment, shown in  FIG. 8 , the MUT  20  may be mounted on the lid  24  and the acoustic port  26  is in the lid  24 . In this second embodiment, the ASIC  22  may remain on the substrate  18  or may be mounted on the lid  24  along with the MUT  20 . If the MUT  20  is mounted on the lid  24  and the ASIC  22  is mounted on the substrate  18 , electrical connections between the MUT  20  and the ASIC  22  may be formed using conductive traces on the lid  24  and substrate  18  in a fashion similar to that used to connect electrical components on printed circuit boards. In this embodiment, the MUT  20  is first electrically connected to the lid  24  and the ASIC  22  is electrically connected to the substrate  18  and a connection may be established between lid  24  and substrate  18  by means of a conductive via which may be created between the lid  24  and substrate  18 . This process may use a third layer between the lid  24  and substrate  18  which contains the via (not shown). 
         [0045]    In a third embodiment, shown in  FIG. 9 , the MUT  20  may be mounted such that port  28  faces the lid  24 . In this case, the diameter  30  and length  34  of port  28  and the diameter  23  and length  36  of port  26  may be designed to enhance the acoustic output from port  26 . In this case, the MUT  20  may be electrically connected to the substrate by eutectic bonding, solder bonding, or bump bonding. 
         [0046]    All cited references are incorporated herein by reference in their entirety. In addition to any other claims, the applicant(s)/inventor(s) claim each and every embodiment of the invention described herein, as well as any aspect, component, or element of any embodiment described herein, and any combination of aspects, components or elements of any embodiment described herein. 
         [0047]    The appended claims are not to be interpreted as including means-plus-function limitations, unless such a limitation is explicitly recited in a given claim using the phrase “means for.” Any element in a claim that does not explicitly state “means for” performing a specified function, is not to be interpreted as a “means” or “step” clause as specified in 35 USC§112(f). In particular, the use of “step of” in the claims herein is not intended to invoke the provisions of 35 USC§112(f).