Communications – electrical: acoustic wave systems and devices – Receiver circuitry
Reexamination Certificate
1999-08-16
2001-07-31
Lobo, Ian J. (Department: 3662)
Communications, electrical: acoustic wave systems and devices
Receiver circuitry
C367S903000
Reexamination Certificate
active
06269052
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The invention lies in the electronics field. Specifically, the invention relates to a circuit having a transmitter for transmitting a transmission signal to a transducer and a receiver for receiving a reception signal from the transducer. In addition, the invention relates to a method for transmitting a transmission signal to a transducer and for receiving a reception signal from the transducer.
In particular, the invention also relates to a transmitting/receiving circuit, which is also referred to as a transceiver circuit, as well as a transmitting/receiving method for an ultrasonic transducer.
Ultrasonic transducers are usually operated in the so-called pulse echo method. Such transducers must accordingly be able to transmit and to receive alternately. An ultrasonic transducer of this type may be constructed from one or more piezoelectric individual elements arranged for example in a linear or else in a two-dimensional array. In the transmission mode, these individual elements are excited to produce high-frequency oscillations by means of electrical transmission signals which may, if appropriate, be offset in terms of their phase angle with respect to one another for each individual element. As a result, an ultrasonic pulse is generated and is radiated into an examination object to be imaged. The precise focus region of the ultrasonic pulse in the examination object can be varied by way of the driving of the piezoelectric individual elements of the ultrasonic transducer. The ultrasonic pulse is reflected within the examination object in the direction of the ultrasonic transducer. The reflection can occur for example at discontinuities in the examination medium such as e.g. interfaces between materials of different acoustic impedance. These echo pulses or reflected pulses are received by the transducer or the individual elements and converted into a corresponding electrical reception signal. That signal is fed to a receiver equipped with a very sensitive preamplifier in order to raise the signal level of the reception signal. The signal level is generally very low. The amplified reception signal can then be forwarded to a signal processor for evaluation of the information content and for generation of a pictorial representation.
In order to ensure efficient functioning, the transmission signal and the reception signal must be isolated from one another. Therefore, each transducer element is connected to a transmitting/receiving circuit which electrically connects the transducer element selectively either to the transmitter or to the receiver. A transmitting/receiving circuit of this type is also referred to as a transmit/receive separator.
The decoupling of the transmitter from the receiver is desirable in principle because the amplitudes of the transmitted and received signals differ very greatly from one another. A transducer element is typically excited with a signal level of more than 100 V. A reception signal reflected from the examination object, on the other hand, has a very low voltage amplitude in the mV range. The transmitting/receiving circuit decouples receiver and transmitter from one another in order to avoid damage to the sensitive preamplifier in the receiver caused by the powerful transmission signal during the transmission mode. In addition, the decoupling during the transmission mode prevents undesirable influencing of the transmission signal, for example in the form of distortion, by the receiver. On the other hand, decoupling of receiver and transmitter is also desirable during the reception mode, in order to keep transmitter noise away from the receiver.
Various transmitting/receiving circuits are known. The changeover and decoupling can be performed by a circuit either actively, that is to say under the control of a switching signal, or else passively, that is to say automatically. An active transmitting/receiving circuit normally contains a plurality of active components such as transistors which vary their properties in dependence on the switching signal present at a control input. However, an active transmitting/receiving circuit always requires a separate control line for each individual element of the ultrasonic transducer, via which control line the switching signal is transmitted. Moreover, an additional control circuit is required which synchronizes the changeover and decoupling with the transmission and reception signals. If synchronization fails, there is the risk that sensitive assemblies in the receiver will be destroyed. Passive implementations of a transmitting/receiving circuit are usually either limited in terms of their dynamic range or they comprise complicated components, such as, for example transformers with a plurality of windings and taps.
An earlier, commonly assigned German patent application DE 195 14 330 A1 discloses a transmitting/receiving circuit for an ultrasonic imaging system in which a transducer is optionally electrically connected to a transmitter in a transmission mode and to a receiver in a reception mode. For this purpose, the transmitting/receiving circuit contains at least one variable-capacitance diode connected in the reverse direction for the transmission signal of the transmitter between the transducer and receiver. Instead of a single variable-capacitance diode, it is also possible to provide a reverse-connected series circuit borne by two variable-capacitance diodes. When a variable-capacitance diode is used, however, it is possible for a high current pulse to be coupled into the receiver, particularly in the event of a steep rise in the transmission signal. This current pulse can then result in damage to the receiver.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a transceiver circuit and a transmit/receive method, which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which can be constructed using simpler means in comparison with the prior art implementations. It is a particular object to avoid having to use complicated components such as separate control lines or else transformers. In addition, it is also an object to reliably protect the receiver against the powerful transmission signal.
With the foregoing and other objects in view there is provided, in accordance with the invention, a circuit configuration, comprising:
a transmitter for transmitting a transmission signal, a transducer connected to the transmitter for receiving the transmission signal, and a receiver having an input connected to the transducer for receiving a reception signal from the transducer;
a first nonlinear, bipolar voltage-limiting two-terminal network connected between the transmitter and the transducer;
a second nonlinear, bipolar current-limiting two-terminal network connected between the transducer and the receiver; and
a third nonlinear, bipolar voltage-limiting two-terminal network connected in parallel with the input of the receiver.
With the above and other objects in view there is also provided, in accordance with the invention, a method of transmitting a transmission signal to a transducer and for receiving a reception signal from the transducer, which comprises:
coupling a transmission signal of a transmitter to a transducer via a first nonlinear two-terminal network and decoupling the transmission signal from a receiver with a second and a third nonlinear two-terminal network; and
coupling a reception signal of the transducer to a receiver via the second and third nonlinear two-terminal networks and decoupling the reception signal from the transmitter with the first nonlinear two-terminal network; and thereby
limiting a voltage present at the first nonlinear two-terminal network and a voltage present at the third nonlinear two-terminal network in bipolar fashion; and
limiting a current flowing through the second nonlinear two-terminal network in bipolar fashion.
The invention is based on the insight that a transceiver circuit can be realized in a simple manner by conne
Greenberg Laurence A.
Lerner Herbert L.
Lobo Ian J.
Siemens Aktiengesellschaft
Stemer Werner H.
LandOfFree
Transmitting/receiving circuit and transmitting/receiving... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Transmitting/receiving circuit and transmitting/receiving..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Transmitting/receiving circuit and transmitting/receiving... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2512896