Communications – electrical: acoustic wave systems and devices – Transmitter systems
Reexamination Certificate
1998-06-30
2001-04-10
Pihulic, Daniel T. (Department: 3662)
Communications, electrical: acoustic wave systems and devices
Transmitter systems
Reexamination Certificate
active
06215733
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates generally to a method and apparatus for projecting acoustic signals. More specifically, the invention relates to a transducer system in which electromechanical transducer elements may be driven individually with either a positive or negative voltage of substantially the same magnitude.
Typically, transducer drive electronics include a power supply feeding an amplifier. The amplifier provides gain for an input signal, with the amplified input signal then being fed to a transducer assembly that includes several electromechanical transducer elements. These elements are electrically connected in parallel but operate mechanically in series, so that the mechanical displacements of the transducer elements are summed. In such as approach, all electromechanical transducer elements expand and contract in unison.
Referring to
FIG. 1
, a prior art acoustic transducer drive system
10
is shown. System
10
includes a very large, ship-based amplifier section
12
that includes of a number of bridge circuits
14
which gate power from power supply
16
to a transformer
18
primary winding “p”. By appropriately controlling bridge circuit switches
20
A-
20
D, properly phased, square-wave pulses are introduced into the secondaries “s” of transformers
18
. These transformer outputs are then series summed to synthesize a desired waveform, such as a sinewave. The sythesized waveform is typically further amplified, such as by transformer
22
and is then typically tuned via a large, low frequency, tuning inductor
24
. Finally, the waveform is conducted down an underwater drive cable and is presented electrically in parallel to a plurality of electromechanical transducer elements
26
. The electromechanical elements convert the electrically synthesized signal to mechanical and acoustic power. The transducer elements are marked in this figure so that arrows go from negative to positive for the dipoles in these elements.
This approach to amplification can lead to amplifiers having efficiencies in excess of 80%. For some applications however, such as low frequency transmissions, miniaturization of the amplifiers is limited by the necessary size of the transformers, which can also be the heaviest component of the system. Miniaturization is also impeded by the necessary size of the low frequency, tuning inductors.
It is also known that a large, circulating reactive load is frequently encountered in the drive cable of such systems between the power amplifiers on a ship and the array of transducer elements below. Such reactive loads compel the use of large and heavy drive cables. Further, cross talk is frequently experienced between the alternating current transducer power signals and other signals in the transducer drive cable.
In the area of electromechanical materials, it is known that some of these materials exhibit a nonlinear expansion/contraction response, so that the materials require a direct current to bias the materials to a substantially flat section of their response. Besides these materials, a new generation of electromechanical materials are being researched. These materials do not require polarization, which has its advantages, however the expansion/contraction response of the materials can be highly non-linear.
SUMMARY OF THE INVENTION
The invention integrates an amplifier directly into an electromechanical transducer assembly. In one embodiment of this invention, power from a power supply is supplied to what can be described as an electromechanical amplifier that includes bridge circuits that directly drive the transducer elements. Each transducer element can include its own co-located switching network such as, for example, a bridge circuit, that can be used with other system components to control when and for how long a voltage of equal magnitude and of either a positive or negative polarity is selectively directed to the element to expand or contract it in relation to a signal desired to be acoustically transmitted. Besides permitting an output of two voltages of equal magnitude and opposite polarity, the bridge circuit also permits an output that is “open” and one that allows a dissipation of transducer element charge.
By directly driving transducer elements in the manner described, transformer and inductor requirements and their accompanying magnetics are minimized, furthering size reduction and weight reduction transducer design goals. Further, the co-location of transducer electronics with associated transducer drive elements restrains power (energy) circulation amongst these transducer system components, permitting downsizing of transducer drive cables and minimizing undesired cross-talk. By providing one of two drive voltages of equal magnitude and opposite polarity, transducer drive element biasing becomes unnecessary. This “digital” output also lends itself to be used with advanced transducer material technology, in which the non-linear response of these materials do not make them good candidates for being driven via alternating current.
OBJECTS OF THE INVENTION
An object of this invention is to provide a transducer system that minimizes transformer magnetics.
Another object of the invention is to provide a transducer system that minimizes the weight and size of amplification and inductor components.
Another object of the invention is to provide a transducer system that minimizes reactive currents in transducer drive cables.
Yet another object of the invention is to provide a transducer system that minimizes cross-talk in transducer signal lines.
Still another object of the invention is to provide a transducer system that minimizes the need to provide direct current biasing to transducer drive elements.
And still a further object of the invention is to provide a transducer system that is amenable to being used with electromechanical drive materials that have non-linear expansion/contraction response characteristics.
Other objects, advantages and new features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanied drawings.
REFERENCES:
patent: 3581212 (1971-05-01), McMurray
patent: 4360707 (1982-11-01), Joseph et al.
patent: 4405874 (1983-09-01), Suthers
patent: 5051799 (1991-09-01), Paul et al.
patent: 5056067 (1991-10-01), Drumheller
patent: 5469403 (1995-11-01), Young et al.
Hammond Russell E.
Rynne, Jr. Edward F.
Fendelman Harvey
Kagan Michael A.
Lipovsky Peter A.
Pihulic Daniel T.
The United States of America as represented by the Secretary of
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