Communications – electrical: acoustic wave systems and devices – Transmitter systems
Reexamination Certificate
1999-06-15
2001-04-03
Lobo, Ian J. (Department: 3662)
Communications, electrical: acoustic wave systems and devices
Transmitter systems
C310S316010
Reexamination Certificate
active
06212131
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to an ultrasound transmitting circuit including an electrical transmitter from which electrical oscillations, formed of a current signal and a voltage signal, can be fed at an electrical transmission power level over a connecting line into an ultrasound transducer that can be excited by the electrical oscillations to produce ultrasound oscillations.
Such an ultrasound transmitting circuit is used, for example, in therapeutic ultrasound arrays. The use of ultrasound arrays is dependent on a specific amplitude relationship, in addition to a specific phase relationship, between the individual ultrasound transducers in the ultrasound array. Major deviations from the predetermined relationship may cause serious deviations from the desired beam, which, under some circumstances, may even result in injuries to personnel.
The total power level fed in from the electrical transmitter can, in general, be preset very precisely. However, the individual ultrasound transducers have an impedance which, on one hand, is subject to major tolerances from one ultrasound transducer to another by virtue of the production techniques and, on the other hand, also varies dynamically as a function of the type of operation. Due to those impedance variations, the distribution of the transmitted ultrasound amplitudes deviates to a major extent from the predetermined electrical amplitude distribution of the individual electrical transmitters.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide an ultrasound transmitting circuit and an ultrasound transmitting system having a plurality of ultrasound transmitting circuits, which overcome the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and in which an amplitude of transmitted ultrasound oscillations can be predetermined exactly.
With the foregoing and other objects in view there is provided, in accordance with the invention, an ultrasound transmitting circuit, comprising an electrical transmitter for producing electrical oscillations formed of a current signal and a voltage signal; a connecting line connected to the electrical transmitter for carrying the electrical oscillations at an electrical transmission power level; an ultrasound transducer connected to the connecting line for receiving the electrical oscillations, the ultrasound transducer to be excited by the electrical oscillations to produce ultrasound oscillations; a phase regulator connected to the connecting line for receiving the current signal and the voltage signal; and a variable impedance connected to the phase regulator and coupled to the connecting line, the variable impedance to be actuated for placing the current signal and the voltage signal in phase.
When close to resonance, an ultrasound transducer behaves, to a first approximation, like a parallel circuit including a resistor and a capacitor. In accordance with another feature of the invention, the variable impedance is thus preferably configured as an inductance.
In accordance with a further feature of the invention, the relative phase of the current signal and the voltage signal can be controlled even more accurately if the inductance includes a fixed basic inductance and a variable, additional inductance, which can be actuated by the phase regulator.
In accordance with an added feature of the invention, the variable additional inductance can be achieved particularly easily if the additional inductance includes a quarter-wave circuit and at least one capacitance diode which is connected to the quarter-wave circuit and can be actuated by the phase regulator.
In accordance with an additional feature of the invention, a control signal for the variable inductance can be determined particularly easily if the phase regulator has a four-quadrant multiplier with two signal inputs and with one product output, a phase shifter is connected upstream of one of the signal inputs, the current signal and the voltage signal can be respectively supplied to one of the signal inputs, and the product output is connected to the variable impedance. The phase shifter allows the current signal and the voltage signal to be shifted through 90° with respect to one another, so that the electrical reactive power or volt-amperes can be measured through the use of the four-quadrant multiplier. Four-quadrant multipliers are available, for example, from the company Analog Devices, under the product designation MLT 04.
In accordance with yet another feature of the invention, there is provided a control amplifier connected downstream of the product output, in order to amplify the output signal from the four-quadrant multiplier.
In accordance with yet a further feature of the invention, the phase control is particularly stable if a low-pass filter is disposed between the product output and the control amplifier. The phase control results in the transmission power, which is fed in from the electrical transmitter, including only a real power component, but no reactive power or volt-amperes component. In principle, control of the transmitted power level is thus not absolutely essential.
In accordance with yet an added feature of the invention, the transmitted ultrasound oscillations can be controlled even more exactly if the current signal and the voltage signal can also be supplied to a power regulator, by which the electrical transmitter can be actuated in such a manner that the electrical transmission power level is regulated to a nominal power level.
In accordance with yet an additional feature of the invention, in the same way as the phase regulator, the power regulator may also have a four-quadrant multiplier with two signal inputs and one product output, the current signal and the voltage signal may be respectively supplied to one of the signal inputs, and the product output may be connected to the electrical transmitter.
In accordance with again another feature of the invention, once again, a low-pass filter is connected downstream of the product output.
In accordance with again a further feature of the invention, in order to allow the power level fed in from the electrical transmitter to be varied, a feed node, for presetting the nominal power level, is preferably connected upstream of the electrical transmitter.
In accordance with again an added feature of the invention, there is provided a control amplifier connected downstream of the feed node, in order to control the electrical transmitter power level even more precisely.
With the objects of the invention in view, there is also provided an ultrasound transmitting system, comprising a plurality of the ultrasound transmitting circuits coupled to one another.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in an ultrasound transmitting circuit and an ultrasound transmitting system having a plurality of ultrasound transmitting circuits, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope an d range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.
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Oppelt Ralph
Renz Wolfgang
Greenberg Laurence A.
Lerner Herbert L.
Lobo Ian J.
Siemens Aktiengesellschaft
Stemer Werner H.
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