(12) United States Patent
`Perez
`
`111111
`
`1111111111111111111111111111111111111111111111111111111111111
`US006492761Bl
`US 6,492,761 Bl
`Dec.10,2002
`
`(10) Patent No.:
`(45) Date of Patent:
`
`(54) DIGITAL PIEZOELECTRIC TRANSDUCERS
`AND METHODS
`
`(75)
`
`Inventor: Gritsko Perez, Evington, VA (US)
`
`(73) Assignee: Ericsson Inc., Research Triangle Park,
`NC (US)
`
`( *) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`(21) Appl. No.: 09/009,520
`
`(22) Filed:
`
`Jan. 20, 1998
`
`(51)
`(52)
`(58)
`
`(56)
`
`Int. Cl? ................................................ HOlL 41/04
`U.S. Cl. ........................................ 310/324; 310/334
`Field of Search ................................. 310/324, 334,
`310/366
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`* 10/1964 Roberts ...................... 310/328
`3/1976 Fulenwider ................. 310/330
`* 5/1985 Stinger, Jr ................... 341!151
`* 12/1989 Seidel ........................ 310/324
`* 10/1998 Matsumoto et a!.
`... 310/316.01
`
`3,153,229 A
`3,947,708 A
`4,515,997 A
`4,885,781 A
`5,821,666 A
`
`FOREIGN PATENT DOCUMENTS
`
`GB
`JP
`JP
`JP
`
`1382927
`58200698
`59128900
`59188295
`
`2/1975
`11/1983
`7/1984
`10/1984
`
`* cited by examiner
`
`Primary Examiner-Nestor Ramirez
`Assistant Examiner-Peter Medley
`(74) Attorney, Agent, or Firm-Myers Bigel Sibley &
`Sajovec
`
`(57)
`
`ABSTRACT
`
`A digitally driven piezoelectric transducer uses a fiat piezo(cid:173)
`electric element having a plurality of electrically isolated
`conductive sections coupled to one side of said piezoelectric
`element and a conductive ground plate coupled to another
`side of said piezoelectric element. In addition, a resonant
`cavity is coupled to said piezoelectric element and intensi(cid:173)
`fies the acoustic or sound energy produced by said piezo(cid:173)
`electric transducer. This digitally driven piezoelectric trans(cid:173)
`ducer avoids the problems associated with electromagnetic
`interference by avoiding additional analog circuitry pre vi(cid:173)
`ously needed to create sound audible for humans.
`
`20 Claims, 7 Drawing Sheets
`
`bit 0
`bit 1
`bit 2
`bit 3
`bit 4
`bit 5
`
`Verizon Wireless
`Exhibit 1081-0001
`
`

`

`U.S. Patent
`
`Dec.10,2002
`
`Sheet 1 of 7
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`Verizon Wireless
`Exhibit 1081-0002
`
`

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`U.S. Patent
`
`Dec.10,2002
`
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`Verizon Wireless
`Exhibit 1081-0003
`
`

`

`U.S. Patent
`
`Dec.10,2002
`
`Sheet 3 of 7
`
`US 6,492,761 Bl
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`Verizon Wireless
`Exhibit 1081-0004
`
`

`

`U.S. Patent
`
`Dec. 10, 2002
`
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`Verizon Wireless
`Exhibit 1081-0005
`
`

`

`U.S. Patent
`
`Dec.10,2002
`
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`Verizon Wireless
`Exhibit 1081-0006
`
`

`

`U.S. Patent
`
`Dec. 10, 2002
`
`Sheet 6 of 7
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`US 6,492, 761 Bl
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`Verizon Wireless
`Exhibit 1081-0007
`
`

`

`U.S. Patent
`
`Dec.10,2002
`
`Sheet 7 of 7
`
`US 6,492,761 Bl
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`•
`
`•
`
`Verizon Wireless
`Exhibit 1081-0008
`
`

`

`US 6,492,761 Bl
`
`1
`DIGITAL PIEZOELECTRIC TRANSDUCERS
`AND METHODS
`
`BACKGROUND OF THE INVENTION
`
`1. Field of Invention
`The present invention relates to piezoelectric transducers
`and more specifically to piezoelectric transducers driven by
`digital signals thereby eliminating additional analog cir(cid:173)
`cuitry in electronic devices.
`2. The Prior Art
`A piezoelectric element is a crystal which delivers a
`voltage when mechanical force is applied between its faces,
`and it deforms mechanically when voltage is applied
`between its faces. Because of these characteristics a piezo(cid:173)
`electric element is capable of acting as both a sensing and a
`transmitting element. Piezoelectricity exists because some
`atomic lattice structures have as an essential cell a cubic or
`rhomboid atomic cage, and this cage holds a semi-mobile
`ion which has several stable quantum position states inside
`itself. The ion's post ion state can be caused to shift by either
`deforming the cage or by applying an electric field or
`voltage. The coupling between the central ion and the cage
`transforms electrical charge to mechanical strain and vice
`versa.
`Based on these fundamental principles of piezoelectricity,
`it is well known that if an analog signal is applied to a
`piezoelectric element, the piezoelectric element will deform,
`thereby creating a sound pressure which in turn may create
`an audible sound. Piezoelectric speakers can generate a wide
`range of high sound pressures. In addition, piezoelectric
`elements may be manufactured using an ultra thin piezo(cid:173)
`electric film, which allows the piezoelectric elements to be
`made quite small. Such piezoelectric elements have been
`used to provide sound audible in the human hearing range
`for such devices as speakers for computers, cordless phones,
`alarm clocks, fire alarms, buzzers, headphones, and ear(cid:173)
`phones driven by analog signals.
`Unlike conventional speaker systems, a piezoelectric ele- 40
`ment is capable of creating a sound without a fragile or
`moving coil. Piezoelectric elements thus are ideal for
`today's electronic devices because they do not emit a
`significant amount of electrical noise or electromagnetic
`interference ("EMI"). The EMI produced by coil-based
`speakers is usually lower than the EMI generated by the
`audio, radio and power supply circuitry. As a more signifi(cid:173)
`cant advantage, piezoelectric transducers are significantly
`cheaper than electrodynamic speakers. In addition, piezo(cid:173)
`electric elements are compatible with solid state devices 50
`because they are rugged, compact, reliable and efficient. A
`further benefit of piezoelectric elements is that they consume
`a little amount of power compared to the amount of acoustic
`pressure they can generate.
`A problem with conventional piezoelectric elements is 55
`that in order for them to reproduce human voice or music
`sounds with acceptable quality they have had to be driven by
`analog voltage signals. See FIGS. 3 and 4, and discussion
`below. Because piezoelectric elements used to reproduce
`human voice or musical sounds are driven by analog voltage 60
`signals, any system using these devices must incorporate
`analog circuitry, such as an operational amplifier circuit or
`a digital to analog converter. Analog circuitry is sensitive to
`noise and EMI. EMI disturbs electronic equipment, as
`perceived in the form of undesired audible noises and 65
`distortions on the output audio signal of cellular phones and
`other equipment. An electromagnetic field is a combination
`
`20
`
`2
`of electric and magnetic fields. The frequency of oscillation
`can range from a fraction of one Hertz (cycle per second) to
`many million Hertz. EMI will decrease the overall perfor(cid:173)
`mance and reliability of affected electronic devices using
`5 analog circuits.
`Currently, cellular phones are designed with analog
`driven electrodynamic speakers to generate audible sounds.
`As illustrated by the schematic in FIG. 4, these prior art
`systems use digital signal processors or microprocessors to
`10 drive a digital to analog converter, which in turn, provides
`an analog signal to the electrodynamic speaker.
`Another method of providing sound is depicted in more
`detail in FIG. 3, wherein a piezoelectric element is driven
`directly by an analog signal. These piezoelectric systems
`15 also use a digital to analog converter to create a usable signal
`for the piezoelectric transducers. Both of these prior art
`systems are susceptible to the problems associated with
`EMI, which is a common source of noise heard in acoustic
`generation devices.
`The EMI which causes unwanted noise in the speakers of
`modern communication devices, such as cellular phones, is
`largely generated by the analog and digital circuitry associ(cid:173)
`ated with the means for driving said speakers. In cellular
`25 communication systems several different mobile units share
`the same set of frequency channels at the same time. In order
`to share the same frequency, the mobile units using the
`system sample a given set of frequency channels (spread
`spectrum) at a predetermined and controlled rate. The three
`30 basic spread spectrum types are code-division multiple
`access (CDMA), time-vision multiple access (TDMA), and
`frequency-vision multiple access. Turning the sampling
`circuitry, which monitors the signals being sent by a base
`station, on and off at high rates of speed generates EMI.
`35 Such EMI can cause problems with cellular phone spear
`clarity, because it is a source of noise which can be heard by
`humans on the speaker system. Some say the noise makes
`the phone sound as if the speaker is making a low hissing or
`crackling sound ("motor-boating").
`Thus, a need exists in the electronic industry to replace
`analog driven speakers in various products, including cel(cid:173)
`lular phones, with purely digitally driven speakers which are
`less susceptible to EMI. The present invention discloses a
`digitally driven piezoelectric transducer which is not depen-
`45 dent on analog circuitry to produce audible sound, thereby
`eliminating the problems with EMI and the need for addi(cid:173)
`tional analog circuitry.
`
`SUMMARY OF THE INVENTION
`
`The present invention comprises a digitally driven piezo(cid:173)
`electric transducer. The invention uses a piezoelectric ele(cid:173)
`ment having a plurality of electrically isolated conductive
`sections carried by one side of the piezoelectric element and
`a conductive common plate carried by the other side of the
`piezoelectric element. In addition, the invention includes a
`resonant cavity which is connected with the piezoelectric
`element which intensifies the sound energy produced by the
`piezoelectric transducer.
`A digitally driven piezoelectric transducer avoids the
`problems associated with EMI because it eliminates the need
`for additional analog circuitry to create sound audible to
`humans. In the invention, a plurality of electrically isolated
`conductive strips of varying size are carried by one side of
`a piezoelectric element. The electrically isolated conductive
`strips may take the form of any convenient shape and are
`specifically designed to cover areas of predetermined sizes
`on said piezoelectric element. The electrically isolated con-
`
`Verizon Wireless
`Exhibit 1081-0009
`
`

`

`US 6,492,761 Bl
`
`3
`ductive strips are integrally formed with the piezoelectric
`element, covering predetermined surface areas to form a
`binary progression. Each electrically isolated conductive
`section is driven by a different bit of the parallel digital
`signal supplying the acoustic information, and thus gener(cid:173)
`ating sounds in different ranges according to the input
`signals.
`The present invention therefore avoids the problems with
`prior art speaker systems by avoiding the use of digital to
`analog conversion circuitry. By not using this conversion 10
`circuitry, the invention allows designers to avoid using
`unnecessary analog circuitry that is susceptible to EMI. In
`addition, since digital piezoelectric transducers have no coils
`or magnets, they are less likely to pick up EMI radiated by
`other systems.
`
`DETAILED DESCRIPTION OF THE DRAWINGS
`FIG. 1 shows in plane view a schematic embodiment of
`a digital piezoelectric transducer.
`FIG. 1A shows the strip/bit distribution for a four-bit
`piezoelectric transducer.
`FIG. 2 is a diagrammatic illustration in side view of a
`digital piezoelectric transducer taken from a side view
`perspective.
`FIG. 3 shows schematically a prior art analog piezoelec(cid:173)
`tric transducer and the circuitry for driving same.
`FIG. 4 shows schematically prior art circuitry for driving
`a cellular phone sound system using an analog electrody(cid:173)
`namic speaker system.
`FIG. 5 is a simplified wiring schematic for connecting an
`eight-bit digital signal to a digital piezoelectric transducer of
`this invention.
`FIGS. 6A, B and C depict several digital piezoelectric 35
`transducers having electrically isolated conductive sections
`formed in different sizes and shapes.
`
`4
`30kHz. This frequency range is chosen because it covers the
`spectrum of frequencies human beings are capable of hear(cid:173)
`ing. Although the resonant cavities 18 depicted in FIGS. 1
`and 2 are rectangular in shape, as discussed in more detail
`5 below, the resonant cavity 18 may be manufactured in any
`desired shape. Of course, in best modes of the invention, the
`resonant cavity is optimally designed to intensify the sound
`pressure changes generated by deformation of said piezo(cid:173)
`electric element 12.
`The digital piezoelectric transducer 10 takes advantage of
`a physical property of piezoelectric material, in that, it
`deforms proportionally to the area covered by a voltage
`difference. As a result of this phenomenon, the more area
`covered by each electrically isolated conductive section 14,
`15 the greater the deformation of the piezoelectric element 12
`from its center position when a voltage is applied to each
`electrically isolated conductive section 14. The electrically
`isolated conductive sections 14 may be provided to cover
`different surface areas of said piezoelectric element 12 in
`20 almost any shape, including rectangular and circular.
`Therefore, digital piezoelectric transducers may be made in
`many different shapes and sizes.
`As previously discussed, the piezoelectric element 12 in
`25 a digital piezoelectric transducer 10 is connected with a
`plurality of electrically isolated conductive sections 14 dis(cid:173)
`tributed on one side of the piezoelectric element 12. Each of
`the electrically isolated conductive sections 14 is integrally
`formed to cover predetermined surface areas on said piezo-
`30 electric element 12, forming a binary progression. Also,
`each electrically isolated conductive section 14 on the digital
`piezoelectric transducer 10 is driven by a different bit of a
`parallel signal carrying audible message.
`The least significant bit of a parallel digital signal is
`coupled to the electrically isolated conductive section 14
`that covers the least amount of surface area on the piezo(cid:173)
`electric element 12. The most significant bit of the parallel
`signal is connected to the electrically isolated conductive
`section 14 which covers the most surface area on the
`40 piezoelectric element 12. Accordingly, each bit of the par(cid:173)
`allel digital signal will cover an increasing amount of
`surface area as the bit order increases from least significant
`bit to most significant bit.
`The digital piezoelectric transducer 10 disclosed may be
`designed to be driven by as many bits as the designer
`chooses. For example a digital piezoelectric transducer may
`be designed to handle a digital drive signal of 4, 8, 16, 32 or
`any other number of bits in length. Typically, however, it is
`convenient to use signals having a length that is in multiples
`of four. An eight-bit digital piezoelectric transducer 10 is
`disclosed here as an example only and is by no means meant
`as a limitation. A four-bit piezoelectric transducer is depicted
`in FIG. 1A having 15 electrically isolated conductive strips,
`55 instead of the 255 that would be used for an eight-bit system.
`The digital piezoelectric transducer 10 can be designed to be
`driven by ann-bit digital word and will have 2-1 electrically
`isolated conductive strips 14 formed thereon.
`An eight-bit digital piezoelectric transducer can be
`designed in a wide range of sizes and shapes. As illustrated
`graphically in FIGS. 6A, 6B and 6C, a piezoelectric element
`12 used in the present invention may have electrically
`isolated conductive strips 14 manufactured in many different
`shapes and sizes. Each electrically isolated conductive sec-
`65 tion 14 covers a precisely predetermined surface area of the
`piezoelectric element 12 as shown in Tables 1 and 2 pro(cid:173)
`vided below.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`The present invention discloses a piezoelectric transducer
`that is capable of being directly driven by a digital signal.
`FIG. 1 shows a simplified digital piezoelectric transducer 10
`of the present invention. The digital piezoelectric transducer
`10 comprises a piezoceramic plate 12 with a plurality of 45
`electrically isolated conductive sections 14 carried on one
`side. In addition, a conductive common plate 16 is carried on
`the opposite side of the piezoceramic plate. See FIG. 2. As
`depicted, a resonant cavity 18 may be coupled to the
`piezoceramic plate 12 for providing support to the piezoce- 50
`ramie plate 12. The resonant cavity 18 can be formed in any
`shape suitable for intensifying and directing the sound
`generated by vibrations of the piezoceramic plate 12.
`Referring once again to FIG. 1, the digital piezoelectric
`transducer 10 has a resonant cavity 18 so that the sound
`generated is intensified. The resonant cavity 18 is formed
`with a means for providing parallel digital signals to the
`electrically isolated conductive sections 14 which are inte(cid:173)
`grally formed on the resonant cavity 18. For example, the
`resonant cavity 18 may be coupled by a plurality of fixed 60
`contacts 20 that are connected with said plurality of elec(cid:173)
`trically isolated conductive sections 14. These fixed contacts
`20 may then be used for coupling a parallel digital signal
`containing sound to the plurality of electrically isolated
`sections 14.
`The acoustic sound energy is designed to be intensified by
`the resonant cavity 18 in the range of about 10 HZ to about
`
`Verizon Wireless
`Exhibit 1081-0010
`
`

`

`US 6,492,761 Bl
`
`5
`
`TABLE 1
`
`(Referring to FIG. 6B)
`
`Bit
`
`Percentage of Covered Area
`
`7
`6
`5
`4
`3
`2
`
`0
`
`50%
`25%
`12.5%
`6.25%
`3.125%
`1.562%
`0.7812%
`0.3905%
`
`TABLE 2
`
`(Referring to FIG. 6 A, C)
`
`Bit
`
`Angular Section (Degrees)
`
`7
`6
`5
`4
`3
`2
`
`0
`
`45
`22.5
`11.25
`5.625
`2.8125
`1.40625
`0.703125
`0.351563
`
`The present invention also provides novel methods of
`digitally driving a piezoelectric transducer 10. A piezoelec(cid:173)
`tric element 12 has a plurality of electrically isolated con(cid:173)
`ductive sections 14 attached to one side of the piezoelectric
`element 12. In addition, a conductive common plate 16 is
`attached to the other side of the piezoelectric element 12. In
`order to drive a digital piezoelectric transducer 10 a digital
`drive signal must be generated and then supplied to the
`electrically isolated conductive sections 14 in parallel. For
`example, the digital drive signal may take the form of a
`parallel 4, 8, 16, or 32 bit signal.
`The digital drive signal is supplied to the digital piezo- 40
`electric transducer 10 by a means for creating a parallel
`digital signal such as a microprocessor or digital signal
`processor. Another way to drive the piezoelectric transducer
`10 is by connecting the conductive common plate (ground)
`16 to the positive power supply and outputting an active low 45
`pulses from the digital circuitry. This driving method is
`called sinking, as opposed to sourcing, that is, the method of
`using active high pulses to output digital signals. (See FIG.
`5). The digital signals that are used to drive the piezoelectric
`element may be supplied by the output ports of standard so
`microprocessor based systems. The voltage level of the
`digital signals used to drive the piezoelectric element can
`vary, however, in preferred embodiments of the invention
`they range somewhere between 2.5 and 5 volts. In order to
`intensify and direct the acoustic sound pressure created by ss
`the deformation of the piezoelectric element 12, a resonant
`cavity 18 may be coupled with said piezoelectric element 12.
`The resonant cavity 18 also provides support for said
`piezoelectric element 12 and is supplied with a plurality of
`fixed contacts 20 connected with said plurality of electrically 60
`isolated conductive sections 14. The resonant cavity is
`designed to optimally intensify acoustic sounds that cover
`the audible range of human hearing.
`In preferred embodiments of the invention, the step of
`forming the plurality of electrically isolated conductive 65
`sections 14 in a predetermined surface area will be optimally
`done to make the digital piezoelectric transducer 10 create
`
`6
`the best sound quality. The surface areas of said electrically
`isolated conductive sections 14 should preferably be
`arranged in a binary progression from least significant bit to
`most significant bit. This gives the engineer who uses said
`s digital piezoelectric transducers much greater control over
`said digitally driven piezoelectric transducer 10 in operation.
`Digitally driven piezoelectric traducer 10 can be
`employed in a variety of electronic equipment to eliminate
`the noise associated with analog speaker systems of the prior
`10 art. Cellular phones are an ideal application for such trans(cid:173)
`ducers. Current cellular antenna technology allows transfers
`of acoustic information in serial digital format. Therefore,
`the step of converting the serial signal carrying the acoustic
`information into a plurality of parallel driving signals ear-
`lS rying said acoustic information must be completed. As most
`digital signal processors ("DSP") and microprocessors con(cid:173)
`tain parallel output/input ports, this step is limited to minor
`changes in the DSP or microprocessor software. The parallel
`driving signals are connected with the electrically isolated
`20 conductive sections 14 to provide the acoustic sound energy.
`In addition, a digital piezoelectric transducer 10 such as
`disclosed here may be incorporated into a hand-held per(cid:173)
`sonal communications device. Such a device is typically
`provided with a means for receiving an information signal
`25 broadcast from a cellular or satellite communication sys(cid:173)
`tems. The cellular communications systems may be of any
`type or mode, such as analog, CDMA, TDMA, or FDMA.
`The hand-held personal communications device would also
`be provided with a means for transforming said information
`30 signal into a parallel digital signal. This operation is typi(cid:173)
`cally performed by such devices as a digital signal processor
`or a microprocessor. Finally, a digital piezoelectric trans(cid:173)
`ducer 10 will be incorporated into the design and be coupled
`with said means for transforming the information signal into
`35 a parallel digital signal within the hand-held communication
`device.
`The use of a digital piezoelectric transducer 10 to create
`an audible sound from application of a parallel digital signal
`has benefits in the fact that less EMI is created because of the
`elimination of analog circuitry. In addition, because a digital
`piezoelectric transducer 10 has no coil or fragile speaker and
`does not require analog circuitry, the system will remain
`relatively unaffected by EMI. Other benefits include being
`lightweight, small, inexpensive, and capable of generating
`high-pressure sounds. Further benefits of digitally driven
`piezoelectric transducers will be seen by those skilled in the
`art.
`While the invention has been described in its currently
`best known modes of operation and embodiments, other
`modes and embodiments of the invention will be apparent to
`those skilled in the art. The invention is limited only by the
`scope of the claims that follow.
`What is claimed is:
`1. A digital piezoelectric transducer, comprising:
`a piezoelectric element;
`a conductive common plate carried by a first side of said
`piezoelectric element;
`first and second sets of electrically isolated conductive
`sections carried by a second side of said piezoelectric
`element; and
`first and second electrically isolated connections adapted
`to provide first and second bits of a digital signal to said
`first and second sets of conductive sections such that
`said first set of conduction sections is driven by said
`first bit and said second set of conduction sections is
`driven by said second bit;
`
`Verizon Wireless
`Exhibit 1081-0011
`
`

`

`US 6,492,761 Bl
`
`10
`
`8
`12. The digital piezoelectric transducer of claim 11
`wherein there are twice as many first conductive sections as
`there are of second conductive sections.
`13. The digital piezoelectric transducer of claim 11
`including:
`a third set of electrically isolated conductive sections
`carried by said second side of said piezoelectric ele(cid:173)
`ment; and
`a third electrically isolated connection adapted to provide
`a third bit of said digital signal to said third set of
`conductive sections such that said third set of conduc(cid:173)
`tion sections is driven by said third bit;
`wherein said third set of conductive sections includes a
`plurality of discrete third conductive sections each of
`which is driven by said third bit; and
`wherein said third set of conductive sections has a total
`surface area that is twice said total surface area of said
`first set of conductive sections.
`14. The digital piezoelectric transducer of claim 13
`wherein said first, second, and third conductive sections
`each have substantially the same size and shape.
`15. The digital piezoelectric transducer of claim 14
`wherein said first, second, and third conductive sections are
`rectangular and are interleaved in alternating manner across
`said second side of said piezoelectric element.
`16. The digital piezoelectric transducer of claim 1 wherein
`each of said first conductive sections is wedge-shaped.
`17. The digital piezoelectric transducer of claim 16
`wherein at least one conductive section of said second set of
`conductive sections is interposed between a pair of said first
`30 conductive sections.
`18. The digital piezoelectric transducer of claim 1 wherein
`each of said first conductive sections is rectangular.
`19. The digital piezoelectric transducer of claim 18
`wherein at least one conductive section of said second set of
`35 conductive sections is interposed between a pair of said first
`conductive sections.
`20. The digital piezoelectric transducer of claim 1 further
`including a resonant cavity connected with said piezoelectric
`element for intensifying acoustic energy generated by said
`40 piezoelectric element in the range of about 10 Hz to about
`30kHz, and wherein said piezoelectric element is adapted to
`directly generate the acoustic energy intensified by said
`resonant cavity.
`
`5
`
`7
`wherein said first set of conductive sections includes a
`plurality of electrically isolated first conductive sec(cid:173)
`tions each of which is driven by said first bit.
`2. The digital piezoelectric transducer of claim 1 further
`comprising a resonant cavity connected with said piezoelec-
`tric element for intensifying acoustic energy generated by
`said piezoelectric element.
`3. The digital piezoelectric transducer of claim 2 wherein
`the acoustic energy is intensified by said resonant cavity in
`the range of about 10 Hz to about 30 kHz.
`4. The digital piezoelectric transducer of claim 1 wherein
`each of said first and second sets of electrically isolated
`conductive sections is integrally formed to cover a different
`predetermined surface area on said piezoelectric element.
`5. The digital piezoelectric transducer of claim 1 further 15
`comprising means attached to said piezoelectric element for
`providing parallel digital signals to said first and second sets
`of electrically isolated conductive sections.
`6. The digital piezoelectric transducer of claim 1 wherein
`said first and second sets of electrically isolated conductive 20
`sections form a binary progression of surface area, each of
`said first and second sets of electrically isolated conductive
`sections being driven by a different bit of parallel digital
`signals.
`7. The digital piezoelectric transducer of claim 1 wherein 25
`said resonant cavity has means including a plurality of fixed
`contacts that are connected with said first and second sets of
`electrically isolated conductive sections for connecting par(cid:173)
`allel digital signals to said first and second sets of electrically
`isolated conductive sections.
`8. The digital piezoelectric transducer of claim 1 wherein
`at least one conductive section of said second set of con(cid:173)
`ductive sections is interposed between a pair of said first
`conductive sections.
`9. The digital piezoelectric transducer of claim 1 wherein
`said second set of conductive sections includes a plurality of
`discrete second conductive sections each of which is driven
`by said second bit.
`10. The digital piezoelectric transducer of claim 9 wherein
`at least one of said second conductive sections is interposed
`between a pair of said first conductive sections.
`11. The digital piezoelectric transducer of claim 9 wherein
`said first set of conductive sections has a total surface area
`that is twice a total surface area of said second set of
`conductive sections.
`
`* * * * *
`
`Verizon Wireless
`Exhibit 1081-0012
`
`