CN115957956A - Circuit arrangement, ultrasonic sensor and vehicle having such a circuit arrangement - Google Patents

Circuit arrangement, ultrasonic sensor and vehicle having such a circuit arrangement Download PDF

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Publication number
CN115957956A
CN115957956A CN202211246701.4A CN202211246701A CN115957956A CN 115957956 A CN115957956 A CN 115957956A CN 202211246701 A CN202211246701 A CN 202211246701A CN 115957956 A CN115957956 A CN 115957956A
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circuit arrangement
unit
integrator
amplifier
analog
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M·弗雷德
Y·傅
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Robert Bosch GmbH
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Robert Bosch GmbH
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S15/00—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
    • G01S15/88—Sonar systems specially adapted for specific applications
    • G01S15/93—Sonar systems specially adapted for specific applications for anti-collision purposes
    • G01S15/931—Sonar systems specially adapted for specific applications for anti-collision purposes of land vehicles
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
    • G01S7/523—Details of pulse systems
    • G01S7/526—Receivers
    • G01S7/527—Extracting wanted echo signals
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
    • G01S7/534—Details of non-pulse systems
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
    • H03F3/45—Differential amplifiers
    • H03F3/45071—Differential amplifiers with semiconductor devices only
    • H03F3/45076—Differential amplifiers with semiconductor devices only characterised by the way of implementation of the active amplifying circuit in the differential amplifier
    • H03F3/45179—Differential amplifiers with semiconductor devices only characterised by the way of implementation of the active amplifying circuit in the differential amplifier using MOSFET transistors as the active amplifying circuit
    • H03F3/45183—Long tailed pairs
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
    • H03F3/45—Differential amplifiers
    • H03F3/45071—Differential amplifiers with semiconductor devices only
    • H03F3/45076—Differential amplifiers with semiconductor devices only characterised by the way of implementation of the active amplifying circuit in the differential amplifier
    • H03F3/45475—Differential amplifiers with semiconductor devices only characterised by the way of implementation of the active amplifying circuit in the differential amplifier using IC blocks as the active amplifying circuit
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
    • H03F3/45—Differential amplifiers
    • H03F3/45071—Differential amplifiers with semiconductor devices only
    • H03F3/45479—Differential amplifiers with semiconductor devices only characterised by the way of common mode signal rejection
    • H03F3/45928—Differential amplifiers with semiconductor devices only characterised by the way of common mode signal rejection using IC blocks as the active amplifying circuit
    • H03F3/45932—Differential amplifiers with semiconductor devices only characterised by the way of common mode signal rejection using IC blocks as the active amplifying circuit by using feedback means
    • H03F3/45937—Measuring at the loading circuit of the differential amplifier
    • H03F3/45941—Controlling the input circuit of the differential amplifier
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
    • H03M1/00—Analogue/digital conversion; Digital/analogue conversion
    • H03M1/06—Continuously compensating for, or preventing, undesired influence of physical parameters
    • H03M1/0617—Continuously compensating for, or preventing, undesired influence of physical parameters characterised by the use of methods or means not specific to a particular type of detrimental influence
    • H03M1/0626—Continuously compensating for, or preventing, undesired influence of physical parameters characterised by the use of methods or means not specific to a particular type of detrimental influence by filtering
    • H03M1/0629—Anti-aliasing
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
    • G01H11/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by detecting changes in electric or magnetic properties
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S15/00—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
    • G01S15/88—Sonar systems specially adapted for specific applications
    • G01S15/93—Sonar systems specially adapted for specific applications for anti-collision purposes
    • G01S15/931—Sonar systems specially adapted for specific applications for anti-collision purposes of land vehicles
    • G01S2015/932—Sonar systems specially adapted for specific applications for anti-collision purposes of land vehicles for parking operations
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
    • G01S7/52004—Means for monitoring or calibrating
    • G01S7/52006—Means for monitoring or calibrating with provision for compensating the effects of temperature
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F2200/00—Indexing scheme relating to amplifiers
    • H03F2200/114—Indexing scheme relating to amplifiers the amplifier comprising means for electro-magnetic interference [EMI] protection
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F2203/00—Indexing scheme relating to amplifiers with only discharge tubes or only semiconductor devices as amplifying elements covered by H03F3/00
    • H03F2203/45—Indexing scheme relating to differential amplifiers
    • H03F2203/45418—Indexing scheme relating to differential amplifiers the CMCL comprising a resistor addition circuit
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F2203/00—Indexing scheme relating to amplifiers with only discharge tubes or only semiconductor devices as amplifying elements covered by H03F3/00
    • H03F2203/45—Indexing scheme relating to differential amplifiers
    • H03F2203/45441—Indexing scheme relating to differential amplifiers the CMCL comprising an integrating circuit
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F2203/00—Indexing scheme relating to amplifiers with only discharge tubes or only semiconductor devices as amplifying elements covered by H03F3/00
    • H03F2203/45—Indexing scheme relating to differential amplifiers
    • H03F2203/45521—Indexing scheme relating to differential amplifiers the FBC comprising op amp stages, e.g. cascaded stages of the dif amp and being coupled between the LC and the IC
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F2203/00—Indexing scheme relating to amplifiers with only discharge tubes or only semiconductor devices as amplifying elements covered by H03F3/00
    • H03F2203/45—Indexing scheme relating to differential amplifiers
    • H03F2203/45526—Indexing scheme relating to differential amplifiers the FBC comprising a resistor-capacitor combination and being coupled between the LC and the IC
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H11/00—Networks using active elements
    • H03H11/02—Multiple-port networks
    • H03H11/04—Frequency selective two-port networks
    • H03H11/12—Frequency selective two-port networks using amplifiers with feedback
    • H03H11/1217—Frequency selective two-port networks using amplifiers with feedback using a plurality of operational amplifiers
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H11/00—Networks using active elements
    • H03H11/02—Multiple-port networks
    • H03H11/04—Frequency selective two-port networks
    • H03H11/12—Frequency selective two-port networks using amplifiers with feedback
    • H03H11/1217—Frequency selective two-port networks using amplifiers with feedback using a plurality of operational amplifiers
    • H03H11/1234—Modifications to reduce detrimental influences of amplifier imperfections, e.g. limited gain-bandwith product, limited input impedance

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  • Engineering & Computer Science (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Physics & Mathematics (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • General Physics & Mathematics (AREA)
  • Power Engineering (AREA)
  • Acoustics & Sound (AREA)
  • Theoretical Computer Science (AREA)
  • Measurement Of Velocity Or Position Using Acoustic Or Ultrasonic Waves (AREA)

Abstract

The invention relates to a circuit arrangement (10) for processing an analog ultrasound signal (11) detected by means of an ultrasound transducer (110) and for converting the processed ultrasound signal (12) into a digital ultrasound signal (13), wherein the circuit arrangement (10) has a low-noise amplifier unit (20), an anti-aliasing filter unit (30) and an analog/digital converter unit (40), which are arranged in series, for processing and converting the analog ultrasound signal (11). One aspect of the invention is that the anti-aliasing filter unit (30) has a feedback loop (31) for suppressing low frequency interference signals. Furthermore, the invention relates to an ultrasonic sensor unit (100) having the circuit arrangement (10) according to the invention and to a vehicle (200) having the ultrasonic sensor unit (100) according to the invention.

Description

Circuit arrangement, ultrasonic sensor and vehicle having such a circuit arrangement
Technical Field
The invention proceeds from a circuit arrangement for processing an analog ultrasound signal detected by means of an ultrasound transducer and for converting the analog ultrasound signal into a digital ultrasound signal, wherein the circuit arrangement has a low-noise amplifier unit, an anti-aliasing filter unit and an analog/digital converter unit, which are arranged in series for processing and converting the analog ultrasound signal.
Background
Electrical interference and high frequency interference occurs during normal operation of many devices. The electrical interference and the high frequency interference are generated with different electrical characteristics over a wide frequency range from, for example, 1MHz to 18GHz, and may be distributed in the system accordingly. Thereby generating Electromagnetic Interference (EMI = Electromagnetic Interference) in the corresponding device.
Such a device is known to the person skilled in the art, for example, from patent document EP 2 255446B1. The received ultrasound signal is amplified by an amplifier, filtered by an anti-aliasing unit and finally converted into a digital ultrasound signal by means of an analog-to-digital converter.
The problem here is that high-frequency signals are processed by means of amplitude modulation in the relevant frequency band due to the non-linear nature of the active components in the circuit arrangement. The resulting dc current offset and low-frequency amplitude variations of these signals are manifested as additional noise sources at the output of the analog/digital converter unit, as a result of which the evaluation of the digital ultrasound signals becomes difficult or even erroneous.
The problem mentioned should be solved by the present invention.
Disclosure of Invention
The invention proceeds from a circuit arrangement for processing an analog ultrasound signal detected by means of an ultrasound transducer and for converting the analog ultrasound signal into a digital ultrasound signal, wherein the circuit arrangement has a low-noise amplifier unit, an anti-aliasing filter unit and an analog/digital converter unit, which are arranged in series for processing and converting the analog ultrasound signal.
An aspect of the invention is that the anti-aliasing filter unit has a feedback loop for suppressing low frequency interfering signals.
It is advantageous here that an improvement of the EMI resistance of the circuit arrangement can be achieved due to the feedback loop by suppressing the signal gain in the low frequency range and correspondingly filtering the modulated signal in addition to the anti-aliasing effect. The noise level of the converted digital ultrasound signal is thereby reduced in turn.
A feedback loop is generally understood to be a mechanism in a signal amplification system or an information processing system in which a portion of an output variable is conducted back to an input of the system, either directly or in a modified form.
The feedback loop can be configured in particular as a negative feedback loop, which is also arranged in the anti-aliasing Filter unit in addition to the biquad Filter (biquadraticfilter) and the passive Filter.
The sequential arrangement is to be understood here to mean that the individual elements of the circuit arrangement are arranged in cascade in terms of signal flow technology.
The analog/digital converter unit is used for converting the processed analog ultrasonic signals into digital ultrasonic signals. The analog/digital converter unit can be configured, for example, as a low-pass Delta Sigma Modulator (DSM). To suppress quantitative noise in the band, a 4-order 2-concatenated multi-bit DSM is proposed. This cascaded structure simplifies the stability problems associated with high order single bit modulators.
One embodiment of the invention provides that the feedback loop comprises an integrator and a current source that can be controlled by the integrator and is used to generate the feedback current.
Advantageously, the following currents can be influenced by means of the feedback current: this current flows out of the amplifier unit and thus into the anti-aliasing filter unit and contains the corresponding ultrasound signal.
An integrator is to be understood here as a circuit: the circuit is configured in particular as an inverting amplifier and is suitable for use as an active filter. Here, the input voltage of the integrator is integrated and the result is provided in the form of an output voltage.
One embodiment of the invention provides that the integrator has an operational amplifier, a capacitor and a resistor, and the controllable current source has a switching element, wherein an input of the operational amplifier of the integrator is connected to an output of a further operational amplifier of the anti-aliasing unit, and wherein an output of the operational amplifier of the integrator is connected to the switching element in such a way that the feedback current can be controlled as a function of a voltage applied to the output of the operational amplifier of the integrator, and wherein the switching element is connected to the input of the anti-aliasing unit.
It is advantageous here that a particularly effective feedback loop can be realized.
The input voltage to the integrator drops across the resistance of the integrator, which then charges the capacitor. The capacitor of the integrator is used here as negative feedback (Gegenkopplung).
According to one embodiment of the invention, the resistance value R of the integrator and the value C of the capacitor of the integrator are selected such that the formula
Figure BDA0003886335040000031
The result is greater than the predetermined frequency, in particular greater than 5kHz.
In this case, it is advantageous if the predetermined frequency can be defined in particular as an EMI frequency, so that the corresponding low-frequency components can be filtered out accordingly by means of the feedback loop.
The EMI frequency may be assumed to be 5kHz, for example.
According to a further embodiment of the invention, the amplifier unit has a miller-compensated transconductance amplifier.
It is advantageous here to achieve a particularly good amplifier unit, wherein typical problems of such amplifier units in terms of limiting frequencies, stability problems and increased noise levels no longer exist or only exist insignificantly due to the feedback loop in the anti-aliasing filter unit. This is because, in principle, no pre-filtering is required in the amplifier as is typical in the prior art.
The amplifier unit can be configured in particular as a two-stage amplifier.
According to a further embodiment of the invention, it is provided that the current assembly has a clamping circuit (klemmschal) for amplitude limiting the voltage of the analog ultrasound signal provided by the ultrasound converter, wherein the amplifier units are arranged in series downstream of the clamping circuit.
Advantageously, the capacitance of the capacitor of the clamping circuit can be selected to be larger than typically selected in the prior art due to the feedback loop in the anti-aliasing filter unit. In the prior art, the capacitance must thus be selected so small that high-frequency signals are filtered out, which, however, impairs the effectiveness of the clamping circuit and correspondingly increases the risk of overvoltage being fed into the circuit arrangement. Furthermore, having a correspondingly small-valued capacitor leads to a high EMI sensitivity of the circuit arrangement, since the variable current source transistor of the clamping circuit is supplied with a high-frequency interference signal, which generates a low-frequency envelope variation and transmits a corresponding noise signal further to the other unit. According to the invention, these disadvantages can be eliminated accordingly.
The invention further relates to an ultrasonic sensor unit having an ultrasonic transducer and a circuit arrangement according to the invention. The ultrasonic transducer can here not only emit but also receive ultrasonic signals in that it converts corresponding electrical signals into echo signals and emits said echo signals, and correspondingly receives echo signals and converts these echo signals into electrical signals as analog ultrasonic signals.
Furthermore, the invention relates to a vehicle having an ultrasonic sensor unit according to the invention and a digital ultrasonic signal control device for evaluating the ultrasonic signal provided by the ultrasonic sensor unit. From the digital ultrasound signals, the control device can, for example, perform a distance determination of the vehicle from the object, wherein this information can be used, for example, during a parking procedure.
The vehicle can be configured, for example, as a PKW, LKW or a motorcycle, in which one or in particular a plurality of ultrasonic sensor units according to the invention are installed.
The control device can be configured, for example, as a microcontroller and form a central control device of the vehicle.
Drawings
Fig. 1 shows an embodiment of a vehicle according to the invention with an ultrasonic sensor according to the invention and a control device for evaluating the digital ultrasonic signals provided by the ultrasonic sensor unit;
FIG. 2 shows a clamp circuit according to the prior art;
fig. 3 shows an amplifier cell according to the prior art;
FIG. 4 shows an embodiment of an anti-aliasing filter unit according to the invention;
fig. 5 shows a graph of the common gain coefficient of the amplifier unit and the anti-aliasing filter unit with respect to frequency.
Detailed Description
Fig. 1 shows an exemplary embodiment of a vehicle according to the invention with an ultrasonic sensor according to the invention and a control device for evaluating the digital ultrasonic signals provided by the ultrasonic sensor unit.
A vehicle 200 is shown. The vehicle 200 has an ultrasonic sensor unit 100. The ultrasonic sensor unit 100 in turn comprises an ultrasonic transducer 110 and a circuit arrangement 10 for processing the analog ultrasonic signal 11 detected by means of the ultrasonic transducer 110 and for converting the processed ultrasonic signal 12 into a digital ultrasonic signal 13. For this purpose, the circuit arrangement 10 has a low-noise amplifier unit 20, an anti-aliasing filter unit 30 and an analog/digital converter unit 40, which are arranged in sequence for processing and converting the analog ultrasound signal 11. In addition, the vehicle has a control device 210, which is connected to the ultrasonic sensor unit 100 and is used to evaluate the digital ultrasonic signals 13 provided by the ultrasonic sensor unit 100.
In an embodiment not shown in the figures, the circuit arrangement 10 may have a reference buffer which mainly provides the amplifier unit 20 and the anti-aliasing filter unit 30 with respective reference voltages. The reference buffer has a low output impedance here in order to avoid an unstable closed loop from the non-inverting input connection of the anti-aliasing filter unit 30 to the non-inverting input connection of the amplifier unit 20.
In an embodiment not shown in the figures, the circuit arrangement 10 can also have an incorporated temperature sensor, by means of which the signal conditions for temperature changes can be calibrated.
Fig. 2 shows a clamp circuit according to the prior art.
During transmission, the signals of the ultrasound system have an amplitude of up to +/-100V. In order to protect the electronic components of the circuit arrangement 10, the voltage at the input of the circuit arrangement 10 is limited between 0V and 1.8V by a clamping circuit 50 as shown in fig. 2. The clamping circuit 50 is composed of a coupling capacitor 51, two comparators 52 and two adjustable current sources 53. The analog ultrasonic signal 11 of the ultrasonic transducer 50 is coupled to the non-inverting input connection of the comparator 52. The reference voltages are applied to the inverting input connections of the comparators 52, respectively. The reference voltage is selected upward and downward such that it corresponds to a dc current value that prevents the signal from exceeding the effective input range.
If the amplitude of the ultrasonic signal 11 is greater than the upper reference voltage or less than the lower reference voltage, the output of one of the two comparators 52 switches to the current of the respective current source 53, which results in charging or discharging the coupling capacitor 51 and thereby sets and limits the level of the input signal accordingly.
Fig. 3 shows an amplifier unit according to the prior art.
A low-noise amplifier unit 20 with Pseudo-Single-Ended-differential-conversion means (Pseudo-Single-Ended-differential-impedance) is shown, which means that only the positive output of the amplifier unit 20 contains the corresponding ultrasonic signal. The gain of the amplifier unit 20 is, for example, 20, which is produced by two resistors, not shown in the figure, whose resistance values differ by a factor of 20 accordingly.
The amplifier unit 20 is configured as a two-stage miller-compensated transconductance amplifier that processes input signals on one side. A reference voltage is applied to the non-inverting input potential of the amplifier unit 20, which is provided by a reference buffer, for example. Since the input stage of the amplifier cell 20 is more critical than the preset load transistor pair interference, especially the input differential pair 21 and the common source transistor 22 have a high sensitivity to electromagnetic interference (elektromagnetischen interference). The low-pass filtering function is realized by using a series resistor 23 and a capacitor 24 on the gates of the CMOS input differential pair 21, which has the effect of reducing high-frequency modulation signals that may cause interference to the input differential pair 21 in the amplifier unit 20.
Fig. 4 shows an embodiment of an anti-aliasing filter unit according to the invention. A third order anti-aliasing filter unit 30 is shown having an active second order biquad filter with a signal gain of e.g. four and a passive first order filter. The biquad filter is based on a multiple feedback architecture operational amplifier having a Common Mode Feedback (CMFB) output, wherein the CMFB regulates the common mode voltage between the outputs of the anti-aliasing filter unit 30. The anti-aliasing filter unit 30 removes high frequency components from the ultrasound signal 11 to prevent subsequent analog/digital converter units 40 from causing distortion due to previous sampling of the ultrasound signal 11.
In addition, the anti-aliasing filter unit 30 has a feedback loop 31. The feedback loop 31 has an integrator 32 and a current source 39 controllable by the integrator 32 for generating a feedback current I RF . The integrator 32 in turn has an operational amplifier 33, a capacitor 34 and a resistor 35. The controllable current source 38 has a switching element 39. The input of the operational amplifier 33 of the integrator 32 is connected to the output of a further operational amplifier 37 of the anti-aliasing unit 30, the further operational amplifier 37 being part of a biquad filter. In addition, the output of the operational amplifier 33 of the integrator 32 is connected to a switching element 39 in such a way that the feedback current I can be controlled as a function of the voltage applied to the output of the operational amplifier 32 of the integrator 32 RF Wherein the switching element 39 is connected to an input of the anti-aliasing unit 30. Thereby, the current I can be fed back RF To influenceCurrent I flowing from the amplifier unit 40 into the anti-aliasing filter unit 30 SIG The amount of (c). The undesired model signal is measured by means of the integrator 32 and is coupled to the current I by means of the high gain of the integrator at low frequencies SIG To distinguish them. The integrator 32 in the feedback loop 32 here generates a high-pass function in the closed-loop transfer function.
Fig. 5 shows a graph of the common gain coefficient of the amplifier unit and the anti-aliasing filter unit with respect to frequency. In the diagram, the gain factors V of the two components of the circuit arrangement 10, namely the amplifier unit 20 and the anti-aliasing filter unit 30, are plotted on the ordinate. While the angular frequency omega is plotted on the abscissa.
The transmission characteristics of the structural elements (i.e. the amplifier unit 20 and the anti-aliasing filter unit 30 with the feedback loop 31) are given by the following equation:
Figure BDA0003886335040000071
where A1 is the transfer function of the amplifier unit 20, A2 is the transfer function of the anti-aliasing filter unit 30, and Af is the transfer function of the feedback loop 31.
In addition, the following applies:
Figure BDA0003886335040000072
with low frequency gain A2 and 3dB bandwidth ω of the anti-aliasing filter unit 30 3dB 。
The low frequency gain Af of the feedback loop 31 may be calculated as follows:
Figure BDA0003886335040000073
wherein Af = g Aint, and wherein @>
Figure BDA0003886335040000074
WhereinG is the transconductance of the switching element 30, ω f Is the 3dB bandwidth of integrator 32 and Aint is the low frequency gain of integrator 32.
Since the amplifier unit 20 has a large bandwidth, A1(s) is below the frequency ω 3dB The case (2) is assumed to be a constant A1. After combining the aforementioned equations, the common transfer function of the amplifier unit 20 and the anti-aliasing filter unit 30 with the feedback loop 31 can be expressed in the following way:
Figure BDA0003886335040000075
the frequency response analysis of the common transfer function of the amplifier unit 20 and the anti-aliasing filter unit 30 with the feedback loop 31 can be performed accordingly on fig. 5. The transfer function is shown here: at a frequency of ω f In the case of (2) and (a) at a frequency of (A2) f In the case of (2) a pole ω occurs p 。
The low-frequency signals can be suppressed by a factor A1/Af, so that the modulation signal can be removed, wherein ω is guaranteed p Less than the echo signal frequency. At medium frequency (omega) 3dB >ω>ω p ) In this case, the gain becomes A1 × A2, which remains unchanged compared to the prior art. At high frequencies (omega)>ω 3dB ) Accordingly, the anti-aliasing effect after sampling by the analog/digital converter unit 40 is avoided.

Claims (8)

1. A circuit arrangement (10) for processing an analog ultrasound signal (11) detected by means of an ultrasound converter (110) and for converting the processed ultrasound signal (12) into a digital ultrasound signal (13), wherein the circuit arrangement (10) has a low-noise amplifier unit (20), an anti-aliasing filter unit (30) and an analog/digital converter unit (40) which are arranged sequentially for processing and conversion of the analog ultrasound signal (11),
it is characterized in that the preparation method is characterized in that,
the anti-aliasing filter unit (30) has a feedback loop (31) for suppressing low frequency interference signals.
2. The circuit arrangement (10) as claimed in claim 1, characterized in that the feedback loop (31) comprises an integrator (32) and a current source (39) controllable by the integrator (32) for generating a feedback current (I) RF )。
3. The circuit arrangement (10) according to claim 2, characterized in that the integrator (32) has an operational amplifier (33), a capacitor (34) and a resistor (35), and the controllable current source (38) has a switching element (39), wherein an input of the operational amplifier (33) of the integrator (32) is connected to an output of a further operational amplifier (37) of the anti-aliasing unit (30), wherein an output of the operational amplifier (33) of the integrator (32) is connected to the switching element (39) in such a way that the feedback current (I) can be controlled as a function of a voltage applied at the output of the operational amplifier (33) of the integrator (32) RF ) Wherein the switching element (39) is connected to an input of the anti-aliasing unit (30).
4. The circuit arrangement (10) according to claim 3, characterized in that the value R of the resistance (35) of the integrator (32) and the value C of the capacitor of the integrator (32) are chosen such that the formula
Figure FDA0003886335030000011
The result is greater than a predetermined frequency, in particular greater than 5kHz.
5. The circuit arrangement (10) according to any one of the preceding claims, wherein the amplifier unit (20) has a miller-compensated transconductance amplifier.
6. The circuit arrangement (10) according to any one of the preceding claims, wherein the current assembly (10) has a clamping circuit (50) for amplitude limiting the voltage of the analog ultrasound signal (11) provided by the ultrasound transducer (110), wherein the amplifier units (20) are arranged sequentially behind the clamping circuit (50).
7. An ultrasonic sensor unit (100) having an ultrasonic transducer (110) and a circuit arrangement (10) according to any one of the preceding claims.
8. A vehicle (200) with an ultrasonic sensor unit (100) according to claim 7 and with a control device (210) for the evaluation of the digital ultrasonic signals (13) provided by the ultrasonic sensor unit (100).
CN202211246701.4A 2021-10-12 2022-10-12 Circuit arrangement, ultrasonic sensor and vehicle having such a circuit arrangement Pending CN115957956A (en)

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DE102021211498.9A DE102021211498A1 (en) 2021-10-12 2021-10-12 Circuit arrangement for processing an analog ultrasonic signal detected by an ultrasonic converter and for converting the analog ultrasonic signal into a digital ultrasonic signal, as well as an ultrasonic sensor and a vehicle with such a circuit arrangement

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US7656750B2 (en) 2008-02-26 2010-02-02 Semiconductor Components Industries, Llc Echo detection
US20180234059A1 (en) 2017-02-14 2018-08-16 General Electric Company Low noise amplifier with hybrid termination and variable gain
US10680633B1 (en) 2018-12-21 2020-06-09 Analog Devices International Unlimited Compnay Data acquisition system-in-package

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