Abstract:
Embodiments include an implant and a method of operating the implant. The implant includes a receiver that receives first ultrasound signals emitted by an external transmitting unit of a further apparatus. The receiver includes a piezoelement, which is excited by the first ultrasound signals at a first resonance frequency (f 1 ) and therefrom converts the mechanical energy transferred with the first ultrasound signals into electrical energy. In embodiments of the invention, the piezoelement is additionally excited at a second resonance frequency (f 2 ), which differs from the first resonance frequency (f 1 ), and at the second resonance frequency (f 2 ) operates as a transmitter to transmit second ultrasound signals.

Description:
[0001]    This application claims the benefit of German Patent Application DE 10 2016 104 097.5, filed on 7 Mar. 2016, the specification of which is hereby incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    Field of the Invention 
         [0003]    Embodiments of the invention generally relate to a medical implant and a method of operating the medical implant. 
         [0004]    Description of the Related Art 
         [0005]    Generally, medical endoprostheses or implants for a wide range of applications have been typically used in a large variety. Generally, implants are divided into passive and active implants. Passive implants typically tend to perform mechanical tasks in the body into which they are inserted. Passive implants are typically, for example, a stent, a replacement heart valve, a breast implant, prosthetic body limbs, or optical lenses. By contrast, generally, active implants contain an electronics unit and are able to detect specific body states or perform a treatment. Examples of active implants generally include cardiac pacemakers, neurostimulators, drug delivery pumps, or defibrillators. Typically, further applications of active implants also include sensors for body functions, for example pressure sensors as described in United States Patent Application 20020045921, to Wolinskey et al., entitled “Implantable Pressure Sensors and Methods for Making and Using Them”. Embodiments of the present invention generally relate to active implants in accordance with the above distinction, as will be further discussed below. 
         [0006]    Generally, when using active implants, it may be necessary to exchange data relating to the control of the implant or generated by the implant, for example measurement data of a sensor integrated into the implant, with a unit that is external in relation to the implant. Typically, such a unit that is external in relation to the implant can be, for example, a unit outside the body, such as a programming apparatus or a further implant. In order to simplify the presentation, generally, a unit of the type above that is outside the body, or a further implant, will be referred to hereinafter as a further apparatus. Typically, it is desirable that a data exchange with the further apparatus is performed wirelessly. In addition, generally, the implants should be as small as possible so as to load the body to a minimal extent on account of their spatial requirement. 
         [0007]    Typically, primarily galvanic communication/impedance modulation-based communication, inductive near-field telemetry systems or radio systems are used for data transfer between the implant and an apparatus that is outside the body for data capture and/or data processing. Typical systems, however, have a series of disadvantages. In the case of galvanic communication/impedance modulation-based communication, generally, housing feedthroughs or electrodes are necessary on the outside of the housing. In addition, typically, electrodes have to be affixed to the body surface on the side of the apparatus outside the body, which is practical only to a limited extent with frequent use of the interface. Generally, inductive near-field telemetry has a heavily limited transfer radius, in particular in the case of miniaturisation of implants and the associated use of small coils. With regard to radio data transfer, typically, there is the known disadvantage that the antenna must be of a certain size, which prevents further miniaturisation. In addition, generally, it is not possible to place the antenna in a housing made of conductive material, such as titanium, and therefore the integration of an antenna into an implant is associated with greater outlay. Typically, a further known disadvantage in the case of radio data transfer lies in the fact that the energy requirement for the data transfer rises depending on the depth of implantation of the implant in the body. Generally, this inevitably leads to the use of larger energy sources, which is also contrary to further miniaturisation. 
         [0008]    Typically, ultrasound has also been used for the exchange of data with an implant. Generally, the systems proposed previously, however, are technically complex and take up a large amount of space. For example, the use of ultrasound for data transfer are described in the publication entitled “Deeply implanted medical device based on a novel ultrasonic telemetry technology”, thesis no. 5730 (2013) at the École Polytechnique Fédérale de Lausanne (Swiss Federal Institute of Technology in Lausanne) by M. Peisino, in U.S. Pat. No. 5,861,018, to Feierbach, entitled “Ultrasound Transdermal Communication System and Method”, in United States Patent Application Publication 20100249882, to Houben, entitled “Acoustic Telemetry System for Communication with an Implantable Medical Device”, and in United States Patent Application Publication 20020045921, to Wolinsky et al., entitled “Implantable Pressure Sensors and Methods for Making and Using Them”. The implants according to the prior art patents and publications generally have a piezoelement, with which ultrasound signals sent by an external transmission unit can be received and converted into electrical signals. 
         [0009]    For example, U.S. Pat. No. 6,140,740, to Porat et al., entitled “Piezoelectric Transducer” generally describes a passive method for ultrasound communication in which a sound wave originating from an external transmitter is modulated in the reflection. According to Porat et al., the patient apparatus necessary for the method, and the production of the sound converter, however, are very complex. 
         [0010]    In view of the above, there is a need of an implant having the possibility for wireless data transfer, which is of a simple structure and allows for a further miniaturisation. 
       BRIEF SUMMARY OF THE INVENTION 
       [0011]    One or more embodiments of the invention include an implant with various features as will be discussed below and as presented in the claims. In at least one embodiment, the implant may include a receiver in the form of or such as a piezoelement that receives first ultrasound signals sent from a transmission unit of a further apparatus such as a second device. In one or more embodiments, the receiver may be excited at a first resonance frequency by the first ultrasound signals and may convert the mechanical energy transferred with the first ultrasound signals into electrical energy. In at least one embodiment, the piezoelement may be excited at a second resonance frequency, wherein the second resonance frequency differs from the first resonance frequency. In one or more embodiments, the piezoelement, at the second resonance frequency, may be operated as or may be or may include a transmitter to transmit second ultrasound signals. 
         [0012]    According to at least one embodiment of the invention, the piezoelement may be used to receive the first ultrasound signals and to transmit the second ultrasound signals and therefore may operate as, or may be or may include a transceiver. As such, by way of one or more embodiments, a low technical outlay may be necessary to transmit the first ultrasound signals and to receive the second ultrasound signals. In at least one embodiment, when transmitting and receiving the ultrasound signals, the piezoelement operates in or includes a resonance mode, such that an effective energy conversion may occur. For operation in the resonance mode, according to one or more embodiments, both series resonance frequency and parallel resonance frequency may be used as resonance frequency when transmitting and when receiving. In at least one embodiment, regarding energy efficiency, the series resonance frequency may be used when transmitting and when receiving the ultrasound signals. 
         [0013]    In one or more embodiments, as a result of the conversion of the received first ultrasound signals, the piezoelement generates sufficient electrical energy to generate and send second ultrasound signals at the second resonance frequency. In at least one embodiment of the invention, a passive communication method may be provided for the active implant, wherein the electrical energy converted from the first ultrasound signals may be used to excite the piezoelement to vibrate at the second resonance frequency, and wherein the piezoelement delivers ultrasound which may be received via a further apparatus. According to one or more embodiments of the invention, the implant may operate without an additional energy source. As such, at least one embodiment includes a significant saving of space and corresponding miniaturisation of the implant. In one or more embodiments of the invention, the implant may operate with an energy source. As such, in at least one embodiment, energy saving may be obtained with the implant, such as during frequently communicating applications, wherein a significant extension of the service life of the implant and/or reduction of the overall size of the energy source of the implant and therefore a reduction of the overall size of the implant may be achieved. 
         [0014]    In one or more embodiments, in conjunction with the transmission of ultrasound signals, the implant may include a metal housing. 
         [0015]    At least one embodiment of the invention, compared to non-ultrasound-based data transfer methods, includes significant advantage as a result of an improved possibility of integration and miniaturisation, as discussed herein. In one or more embodiments, sound converters such as piezoelements may be integrated into hermetically sealed and militarised housings of the implant. 
         [0016]    According to at least one embodiment of the invention, the implant may include two or more implants, wherein communication may be provided between the two or more implants in a network. In one or more embodiments, for example, a first implant may be used as a further apparatus, wherein the further apparatus may include one or more of an ultrasound transmitter, an ultrasound receiver, a data processor that processes data and a storage device, and wherein the first implant may include a small energy store, for example a small battery. At least one embodiment of the invention may include a second implant, the structure of which will be described below in detail, which communicates passively. In one or more embodiments, the implant may be used when there is only very little space available in order to introduce the implant, for example at a specific measurement point for a body parameter. In at least one embodiment, the implant may be a node in a network of implants that communicate with one another or in a network of external apparatuses and implants. 
         [0017]    In one or more embodiments of the invention, the piezoelement may be excited simultaneously at the first resonance frequency and the second resonance frequency. As a result, in at least one embodiment, the device may operate at a faster speed. 
         [0018]    In at least one embodiment, the piezoelement may be formed as or may include a thin rectangular piezoelectric layer, such as a layer with a height H that may range from 100 μm to 1000 μm, such as ranging from 250 μm to 350 μm. In one or more embodiments, the thin rectangular piezoelectric layer may include side edges with lengths L and B, wherein the lengths L, B of the side edges may determine the first and second resonance frequencies. In at least one embodiment, the direction in which the height H of the piezoelectric layer is measured may run perpendicularly to the side edges L, B. In one or more embodiments, the required and/or desired resonance frequencies may be easily adjusted by the lengths L, B of the side edges. In at least one embodiment, the thin rectangular piezoelectric layer may include lead zirconate titanate (PZT). 
         [0019]    In one or more embodiments of the invention, the piezoelement may include a total of at least two electrodes, each formed in a layer-like manner, wherein a first electrode is arranged on an underside of the thin rectangular piezoelectric layer and at least one second electrode is arranged on an upper side of the thin rectangular piezoelectric layer. In at least one embodiment, the upper side of the piezoelectric layer may include a side face having the greatest extent of the piezoelectric layer and the underside is the side of the piezoelectric layer opposite the upper side. 
         [0020]    In one or more embodiments of the invention, the piezoelement may include a total of at least three electrodes, each formed in a layer-like manner, wherein a first electrode is arranged on the underside of the thin rectangular piezoelectric layer, and a second electrode and at least one third electrode, which may be galvanically separated from the second electrode, may be arranged on the upper side of the thin rectangular piezoelectric layer. 
         [0021]    In at least one embodiment, the second electrode and the at least one third electrode may be arranged on the upper side of the piezoelectric layer adjacently, for example as a rectangular layer. 
         [0022]    According to one or more embodiments of the invention, the electrodes arranged on the upper side may include ribs formed in a comb-like manner, wherein the ribs of the second electrode and the ribs of the third electrode engage with one another. For example, in at least one embodiment, each rib of the second electrode lies in a gap between two ribs of the third electrode, and vice versa. 
         [0023]    By way of at least one embodiment, the second electrode and the third electrode are on the upper side of the piezoelectric layer, such that the complexity of the circuitry is simplified during the simultaneous transmitting and receiving operation or mode at a number of frequencies. In one or more embodiments, there may be no galvanic contact between the second electrode and the third electrode on the upper side of the piezoelectric layer, wherein both electrodes are electrically insulated from one another. Thus, in at least one embodiment, any additional separation between the electrodes is not needed. 
         [0024]    One or more embodiments of the invention may include an amplifier, wherein the input of the amplifier is connected to an energy supply, which is connected via a rectifier to the piezoelement. In at least one embodiment, with the aid of the electrical energy converted at the first resonance frequency by the piezoelement, the amplifier may generate an electrical output signal (an AC voltage), wherein the piezoelement may be excited at the second resonance frequency via the amplifier and may generate the corresponding second ultrasonic signal to be sent. By way of one or more embodiments, the amplifier may be or may include a class E amplifier. 
         [0025]    At least one embodiment may include a single electrode on the upper side of the piezoelectric layer and a single electrode on the underside of the piezoelectric layer, wherein the electrodes on the upper side and underside of the piezoelement may be short-circuited by the class E amplifier, which may be remedied by a circulator or a diplexer. As such, in at least one embodiment, with the structuring of the electrodes on the upper side of the piezoelectric layer, such a separation and therefore the associated circuitry outlay may be avoided. 
         [0026]    In order to attain a good separation of the excitation of the piezoelement in the transmitting and receiving mode, according to one or more embodiments, the length L, B of the side edges of the piezoelectric layer may be selected such that the frequency spacing between the first resonance frequency and the second resonance frequency is at least 100 kHz. In one or more embodiments the length L, B of the side edges of the piezoelectric layer may be selected such that the frequency spacing between the first resonance frequency and the second resonance frequency is at least 450 kHz. 
         [0027]    In order to provide a transfer of data from the implant to a further apparatus, at least one embodiment may include an external receiver or a further implant, and the amplifier may include a modulator, such that the output signal to transfer the data may be modulated via the modulator. In one or more embodiments, various modulation methods, such as frequency, amplitude or phase modulation, may be used for this purpose. 
         [0028]    At least one embodiment of the invention may include a method of operating the implant, wherein the piezoelement may be excited at the first resonance frequency and may receive the first ultrasound signals emitted by the transmitting unit of the further apparatus. In one or more embodiments, the piezoelement may be excited at the second resonance frequency via the generated electrical energy and may emit the second ultrasound signals. The method according to at least one embodiment of the invention has the advantages discussed above in conjunction with the implant. In one or more embodiments, an AC voltage may be generated as an output signal, such as via the amplifier with use of the electrical energy generated by the first ultrasound signals, and the AC voltage may be used to excite the piezoelement at the second resonance frequency. 
         [0029]    In at least one embodiment, the modulator may modulate the electrical output signal of the amplifier. 
         [0030]    With an appropriate modulation, by way of one or more embodiments, data may be transferred to the implant via the first ultrasound signal emitted to the implant. As such, in at least one embodiment, the implant may communicate bidirectionally with a further apparatus. With the described piezoelement, one or more embodiments may include a bidirectional communication of the implant in alternating operation (half-duplex) and in counter operation (full-duplex). 
         [0031]    The implant according to at least one embodiment of the invention and the method according to at least one embodiment of the invention will be described hereinafter. By way of one or more embodiments, the features of the invention will be shown and described herein in conjunction with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0032]    The above and other aspects, features and advantages of at least one embodiment of the invention will be more apparent from the following more particular description thereof, presented in conjunction with the following drawings, wherein: 
           [0033]      FIG. 1  schematically shows a first exemplary embodiment of an implant and an external transmitting and receiving unit in the form of a block diagram, according to one or more embodiments of the invention; 
           [0034]      FIG. 2  schematically shows the implant and the transmitting and receiving unit of  FIG. 1 , in detail in the form of a block diagram, according to one or more embodiments of the invention; 
           [0035]      FIG. 3  schematically shows a piezoelectric layer in a perspective side view, according to one or more embodiments of the invention; 
           [0036]      FIG. 4  schematically shows an impedance curve (dependent on frequency) of a piezoelement of the implant of  FIG. 1 , according to one or more embodiments of the invention; 
           [0037]      FIG. 5  shows a phase curve of a piezoelement of the implant of  FIG. 1 , according to one or more embodiments of the invention; 
           [0038]      FIG. 6  schematically shows a first exemplary embodiment of a piezoelement of the implant in a view from below, according to one or more embodiments of the invention; 
           [0039]      FIG. 7  schematically shows the piezoelement of  FIG. 6  in a view from above, according to one or more embodiments of the invention; 
           [0040]      FIG. 8  schematically shows the piezoelement of  FIG. 6  in a view from the side, according to one or more embodiments of the invention; 
           [0041]      FIG. 9  schematically shows a first exemplary embodiment of the implant with the piezoelement of  FIGS. 6 to 8  in a block diagram, according to one or more embodiments of the invention; 
           [0042]      FIG. 10  schematically shows a second exemplary embodiment of a piezoelement of the implant in a view from above, according to one or more embodiments of the invention; 
           [0043]      FIG. 11  schematically shows the piezoelement of  FIG. 10  in a view from below, according to one or more embodiments of the invention; 
           [0044]      FIG. 12  schematically shows the piezoelement of  FIG. 10  in a view from the side, according to one or more embodiments of the invention; 
           [0045]      FIG. 13  schematically shows a second exemplary embodiment of the implant with the piezoelement of  FIGS. 10 to 12  in a block diagram, according to one or more embodiments of the invention; 
           [0046]      FIG. 14  schematically shows a third exemplary embodiment of a piezoelement of the implant in a view from above, according to one or more embodiments of the invention; 
           [0047]      FIG. 15  schematically shows the piezoelement of  FIG. 14  in a view from below, according to one or more embodiments of the invention; 
           [0048]      FIG. 16  schematically shows the piezoelement of  FIG. 14  in a view from the shorter side, according to one or more embodiments of the invention; and 
           [0049]      FIG. 17  schematically shows a third exemplary embodiment of the implant with the piezoelement of  FIGS. 14 to 16  in a block diagram, according to one or more embodiments of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0050]    The following description is of the best mode presently contemplated for carrying out at least one embodiment of the invention. This description is not to be taken in a limiting sense, but is made merely for the purpose of describing the general principles of the invention. The scope of the invention should be determined with reference to the claims. 
         [0051]      FIGS. 1 and 2  schematically show a system that includes an implant  10 , and a transmitting and receiving unit  30  of a further apparatus (not shown), according to one or more embodiments of the invention. In at least one embodiment, the further apparatus may be or may include one or more of a programming apparatus, a patient apparatus, and a further implant. By way of one or more embodiments, first ultrasound signals  21  may be sent from the transmitting and receiving unit  30  of the further apparatus, wherein the first ultrasound signals  21  reach the implant  10  through the body and are received in the implant via the piezoelement  11 . In at least one embodiment, the piezoelement  11 , as will be described in greater detail further below, may serve as, may be or may include a transmitter to transmit second ultrasound signals  22  from the implant  10  to the transmitting and receiving unit  30  of the further apparatus to transfer data from the implant  10  to the further apparatus 
         [0052]    In one or more embodiments, the piezoelement  11  of the implant  10  may include a piezoelectric layer  40  that may be one or more of a planar, rectangular, and ceramic piezoelectric layer, as shown in  FIG. 3 . In at least one embodiment, the piezoelectric layer  40  may include a specific, predefined length L, a specific, predefined width B, and a specific, predefined height H. In one or more embodiments, the height H of the piezoelectric layer  40  may be smaller compared to the length L and the width B. In at least one embodiment, the height H may be 300 μm. As such, in one or more embodiments, the piezoelectric layer  40  is thin. 
         [0053]    In at least one embodiment, resonance frequencies of the piezoelement  11  may be predefined by the length L and the width B of the piezoelectric layer  40 . By exciting the piezoelectric layer  40  at the series resonance frequencies, in one or more embodiments, mechanical energy may be converted into electrical energy particularly efficiently, and vice versa. 
         [0054]    By way of at least one embodiment, the piezoelectric layer  40  may include a length L of 5 mm, a width B of 2 mm, and a height H of 300 μm and may include a lead zirconate titanate (PZT) material that includes a series resonance frequency of f 1 =320 kHz (X-mode) and a series resonance frequency of f 2 =800 kHz (Y-mode). In one or more embodiments, the curve of the absolute value of the impedance depending on the frequency of the piezoelectric layer  40  is shown in  FIG. 4 . Accordingly, by way of at least one embodiment,  FIG. 5  shows the curve of the phase dependency between current and voltage on the frequency of the piezoelectric layer  40 . In order to measure such curves, according to one or more embodiments, the piezoelectric layer  40  may be contacted on its upper side and underside, such that the electric field lines run from the upper side to the underside or from the underside to the upper side (in accordance with the polarity of the applied voltage) of the piezoelectric layer  40  and may be examined with the aid of an impedance analyser. In at least one embodiment, jumps in an impedance curve discussed above may each indicate a resonance at the corresponding frequency. In one or more embodiments, a local minimum in each case characterizes a series resonance frequency of the piezoelectric layer  40  such as the ceramic of the piezoelectric layer. In at least one embodiment, the subsequent local maximum characterizes the corresponding parallel resonance frequency. 
         [0055]    According to one or more embodiments, the piezoelectric layer  40  of the piezoelement  11 , as shown in  FIGS. 6 to 8 , may include two layer-like electrodes, such as a first, layer-like electrode  41  on the underside, as shown in  FIG. 6 , and a second layer-like electrode  42  on the upper side, as shown in  FIG. 7 . In at least one embodiment, the upper side and the underside of the piezoelectric layer  40  may be opposite side faces having the greatest extent. In one or more embodiments, the electrodes  42 ,  41  may occupy the entire or almost the entire surface of the upper side and underside of the piezoelectric layer  40 . 
         [0056]    By way of at least one embodiment, the piezoelement  11  as shown in  FIGS. 10 to 12 , may include a second electrode  142  and a third electrode  143  in the form of two adjacently arranged layers on the upper side of the piezoelectric layer  40 , as shown in  FIG. 10 . According to one or more embodiments, the piezoelement  11  may include a single first electrode  41  on the underside, as shown in  FIG. 11 . In at least one embodiment, the second electrode  142  and the third electrode  143  may be galvanically separated from one another. 
         [0057]    By way of one or more embodiments, the piezoelement  11  as shown in  FIGS. 14 to 16  differs from the piezoelement  11  as shown in  FIGS. 10 to 12 , in terms of the structure of the second electrode  242  and third electrode  243  arranged on the upper side of the piezoelectric layer  40 . In at least one embodiment, the electrodes  242 ,  243  may include ribs arranged in a comb-like manner, wherein each rib of the second electrode  242  is arranged in a gap between two ribs of the third electrode  243 , and vice versa. By way of one or more embodiments, a single electrode  41  may be provided on the underside of the piezoelectric layer  40 , as shown in  FIG. 15 . In at least one embodiment, the second electrode  242  and the third electrode  243  may be galvanically separated from one another. 
         [0058]      FIGS. 9, 13 and 17  show interconnection of the electrodes of the piezoelement  11 , each as a block diagram, according to one or more embodiments of the invention. At least one embodiment may include two different circuit variants: a first circuit variant for a piezoelement  11  that includes two electrodes as shown in  FIG. 9  and a second circuit variant for a piezoelement  11  that includes three electrodes as shown in  FIGS. 13 and 17 . 
         [0059]      FIG. 9  shows the first circuit variant, according to one or more embodiments of the invention. In at least one embodiment, the first electrode  41  may be connected to ground, and the second electrode  42  may be connected to a circulator  17 , wherein the circulator  17  separates the frequency f 1  of the incoming signal from the frequency f 2  of the outgoing signal. In one or more embodiments, the piezoelement  11  may receive a first ultrasound signal  21  having a frequency f 1 , which may be converted into a corresponding incoming electrical signal having a frequency f 1 . In at least one embodiment, the circulator  17  may forward the incoming signal having the frequency f 1  to a rectifier  12 , such as a diode, and may then supply the incoming signal that is rectified to a capacitor  13 , which may be or may include an intermediate energy store. In one or more embodiments, the incoming signal may be tapped at the capacitor  13 . In at least one embodiment, the outgoing signal generated by the frequency generator  16 , which may be amplified by the class E amplifier  15  and includes the frequency f 2 , may be forwarded via another connection point of the circulator  17 . According to one or more embodiments, the connection between the capacitor  13  and the class E amplifier  15  may serve as, may be or may include the energy supply of the amplifier. In at least one embodiment, the piezoelement  11  may convert the outgoing electrical signal into the second ultrasound signal  22 . One or more embodiments may include a modulator (not shown), which modulates the outgoing signal via a frequency, amplitude, or phase modulation in order to transfer data from the implant  10  to the further apparatus. 
         [0060]    According to at least one embodiment of the invention,  FIG. 13  shows the interconnection of the electrodes  41 ,  142 , and  143 , and  FIG. 17  shows the interconnection of the electrodes  41 ,  242 , and  243  in accordance with the second circuit variant. In one or more embodiments, of  FIGS. 13 and 17 , the first electrode  41  may be connected to ground. In at least one embodiment, the second electrode  142 ,  242  may be connected to the rectifier  12 , which rectifies an incoming electrical signal generated from the first ultrasound signal  21  with the frequency f 1 . In one or more embodiments, the rectified signal may then be supplied to a capacitor  13 , which serves as, is or may include an energy store. In at least one embodiment, the incoming signal in the form of the frequency f 1  may be tapped at the capacitor  13 . In one or more embodiments, the third electrode  143 ,  243  in each case may be connected to the class E amplifier  15 , may generate the second ultrasound signal  22  and may transmit the second ultrasound signal  22  with the frequency f 2 . In at least one embodiment, the frequency f 2  may be provided electrically by the frequency generator  16  connected to the third electrode  143 ,  243  and may be amplified by the class E amplifier  15 . In one or more embodiments, the connection between the capacitor  13  and the class E amplifier  15  may serve as, may be or may include the energy supply of the amplifier  15 . In the second variant, at least one embodiment may include a modulator, which modulates the outgoing signal using one or more of a frequency, amplitude, and phase modulation in order to transfer data from the implant  10  to the further apparatus. 
         [0061]    By way of one or more embodiments, the transmitting and receiving unit  30  of the further apparatus, for example a patient apparatus located outside of the body, may transmit a first ultrasound signal  21 , for example at a frequency f 1  of 320 kHz, using a transmitting/receiving sound converter  31 . In at least one embodiment, the first ultrasound signal corresponds to the series resonance frequency of the piezoelement  11  of the implant  10  and is therefore received particularly efficiently by the piezoelement  11  and may be converted into a corresponding electrical AC voltage. In one or more embodiments, the electrical AC voltage may be rectified using a rectifier  12 , which is connected to the piezoelement  11 , and may be stored temporarily in a capacitor  13  connected to the rectifier  12 . In at least one embodiment, the electrical energy in the form of a DC voltage stored in the capacitor  13  may be converted using a class E amplifier  15  and an oscillator  16  into an AC voltage having a frequency of 800 kHz. In one or more embodiments, the data ready to be transferred may be modulated using a modulator integrated into the class E amplifier  15  and may be converted via the piezoelement  11  at the second series resonance frequency f 2  into a second ultrasound signal  22 . According to at least one embodiment, the conversion of the electrical energy into mechanical energy is performed particularly efficiently by the piezoelement  11 , since the conversion occurs at the second series resonance frequency f 2 . In one or more embodiments, the second ultrasound signal  22  may be received in the transmitting and receiving unit  30  of the further apparatus by via a transmitting/receiving sound converter  31 , and may be rectified and demodulated. At least one embodiment may include high-pass filter  34 , amplifier  34  and a demodulator  35  connected thereto to receive, rectify and demodulate the second ultrasound signal  22 . In one or more embodiments, the transferred data may be extracted from the second ultrasound signal  22 . At least one embodiment of the invention may include a memory (not illustrated) for the data transferred with the second ultrasound signal  22  and a processing unit (not illustrated) such as a microcontroller, μC, to process the data. 
         [0062]    By way of one or more embodiments, the transmitting and receiving unit  30  of the further apparatus may be structured substantially similarly to the implant  10 . In at least one embodiment, the transmitting and receiving unit  30  may include at least two sound converters provided in a sound converter unit  31 : a first sound converter that generates and transmits the first ultrasound signal  21 , and a second sound converter that receives and converts the second ultrasound signal  22 . In at least one embodiment, the structure of the transmitting and receiving unit  30  of the further apparatus is therefore advantageous because the complexity of the signal processing is reduced by the separation of the processes of transmitting the first ultrasound signal  21  and receiving the second ultrasound signal  22  by at least two different sound converters. 
         [0063]    In at least one embodiment of the invention, the transmitting and receiving unit  30  of the further apparatus, similarly to the implant  10 , may be structured with a combined sound converter as shown in  FIGS. 6 to 8, 10 to 12, and 14 to 16 . In one or more embodiments, such a structure may be advantageous when the further apparatus is also an implant. 
         [0064]    According to at least one embodiment, the implant  10  may be constructed in a space-saving manner, since the voltage source may be provided in a compact manner merely on account of the energy transferred with the ultrasound signal, such as during comprehensive communication. In one or more embodiments, the ultrasound signals used to transfer the data may include an extensive range, even in the body of a person. By way of at least one embodiment, the elements of the implant may be integrated in a metal housing, for example a metal housing that includes titanium. 
         [0065]    It will be apparent to those skilled in the art that numerous modifications and variations of the described examples and embodiments are possible in light of the above teaching. The disclosed examples and embodiments are presented for purposes of illustration only. Other alternate embodiments may include some or all of the features disclosed herein. Therefore, it is the intent to cover all such modifications and alternate embodiments as may come within the true scope of this invention. 
       LIST OF REFERENCE SIGNS 
       [0000]    
       
           10  implant 
           11  piezoelement 
           12  rectifier 
           13  capacitor 
           15  class E amplifier 
           16  frequency generator 
           17  circulator 
           21  first ultrasound signal at a first frequency f 1   
           22  second ultrasound signal at a second frequency f 2   
           30  transmitting/receiving unit of the further apparatus 
           31  sound converter unit 
           32  frequency generator 
           33  high-pass filter 
           34  amplifier 
           35  demodulator 
           40  piezoelectric layer 
           41  first electrode 
           42 ,  142 ,  242  second electrode 
           143 ,  243  third electrode