Device for environmental sensing and method for adjusting the dynamic range of a receiver amplifier

Abstract

Method for adjusting the dynamic range of a receiver amplifier (100) in an environmental sensor device, comprising the step of injecting (S200) an additional electrical signal (S g ) into the input (11, 12) of the receiving amplifier (100) to reduce an output signal generated due to a first electrical signal (u a ) of the receiving amplifier (100), wherein the additional electrical signal (S g ) by a current source (ig, B) drives a current towards a negative terminal of an operational amplifier (1) inside the receiver amplifier (100) and / or a voltage source (ug, A) is driven to couple a voltage to the positive terminal of the operational amplifier (1) of the receiver amplifier (100).

Description

State of the art

[0001] In environmental sensing, distance measurements between a sensor and surrounding objects are determined based on signals reflected by the surrounding objects or on the propagation times of these signals. A transducer sends a suitable signal into the environment, the echoes of which are received by the same transducer or a neighboring transducer and evaluated, for example, with regard to propagation time and other information. Naturally, a significantly higher amplitude is required for the transmission process than the amplitude of the reflected and received echo. If the transmit transducer is used for both transmission and reception, the electrical transmission signal can lead to unacceptably high input levels for the receiving amplifier if it is not protected or decoupled during transmission.

[0002] Document JP 2009 - 81 641 A discloses an imbalance-balance conversion circuit comprising a volume control circuit for regulating the volume of audio signals; an amplifier circuit for amplifying the audio signals whose volume is controlled by the volume control circuit; and a phase reversal circuit which reverses the phase of the audio signals amplified by the amplifier circuit and feeds it back to the amplifier circuit.

[0003] Fig. Figure 1 shows a prior art arrangement in which an ultrasonic transducer 2 can be supplied with an electrical signal by a transmitting amplifier 3, which is then transmitted as a signal into the vicinity of the transducer 2. Echoes arriving at the transducer 2 are converted into electrical received signals and are picked up and analyzed by a receiving amplifier 100. With a simple electrical design, the receiving amplifier 100 can be protected from the electrical signals of the transmitting amplifier 3, for example, by isolating it from the ultrasonic transducer 2 during the transmission process.

[0004] Fig. Figure 2 shows a detailed view of a circuit arrangement of a receiver amplifier 100, as used in the prior art. A received signal U originating from the converter 2 e(τ) is applied to a series circuit consisting of a capacitor C and an input resistor R1. A feedback resistor R2 is connected between the input resistor R1 and an input terminal 11 of an operational amplifier 1, with the second terminal connected to the output of the operational amplifier 1. A second input 12 of the operational amplifier 1 is connected via a reference voltage source U. ref connected to electrical ground. The reference voltage source U refThis serves to adjust the operating point of the operational amplifier 1. The illustrated arrangement represents a typical example of an inverting amplifier as an input amplifier stage of a receiver path of an environmental sensor system according to the prior art. A dashed-bordered part 10 of the receiver amplifier can be implemented as an integrated circuit (IC). In the prior art, two housing connections are required for the receiver amplifier 100, which are in Fig. 2 as open circles U e (τ), U a (τ) are shown. The input voltage U e (τ) generates a current i1 (τ) in the input resistor R1. The operational amplifier 1 responds to the resulting differential voltage across its inputs 11 and 12 by producing an output voltage U. a (τ) generates a current i2 (τ) in the feedback resistor R2. This results in a change in the output voltage U. a(τ) to such a value that i1 (τ) = -i2 (τ). The input ratio U e (τ) is only amplified in an unaltered, proportional manner to the ratio of resistances R2 and R1 if the output voltage U a (τ) is within the operating voltage range of operational amplifier 1, usually 0 to 5 V. However, particularly during transmission and shortly thereafter, such a large signal U is present at the input. e (τ) indicates that the receiving amplifier 100 or the operational amplifier 1 is being overloaded. In other words, the input signal U e (τ) no longer corresponds to the output signal U a (τ) proportional. However, during transmission and shortly thereafter, one also wants to transmit the very strong input signal U. e(τ) analyze to detect changes at the sensor, such as icing, contamination, and deposits, upstream of the sensor. A time-of-flight-dependent gain can be used for dynamic adjustment. This involves adjusting the gain during the measurement time and / or switching the amplifier paths used. However, the resistors and switches required for this pose a challenge in highly integrated circuits. This is particularly true when an additional separate pin is required on the package of an integrated circuit.

[0005] Fig. Figure 3 shows typical phases of a measurement cycle in the form of a converter input signal plotted against time. i (τ). In a first phase 20, the converter 2 begins to convert electrical energy into mechanical vibrations. The electrical input signal U is quickly e(τ) 23 in a region 21 has increased to such an extent that saturation effects become apparent in the regions of highest amplitude 24. After switching off the excitation, the input signal 23 decays in a region 22 to amplitude ranges in which there is no longer any saturation / overdrive.

[0006] No sufficiently simple devices and methods are known in the prior art by which the dynamics of the input signal of a receiving amplifier can be reduced, particularly during transmission and shortly thereafter. Disclosure of the invention

[0007] The present invention addresses a need existing in the prior art by means of a method with the features of claim 1 and a device with the features of claim 4. Accordingly, a method for adapting the dynamic range of a receiver amplifier to an environmental sensor device is proposed. The receiver amplifier can, in particular, be permanently connected to a converter and a transmitter amplifier providing a transmit signal. The environmental sensor device can, for example, be designed for automotive use as a so-called parking assistance system. Such systems often operate according to the ultrasonic echo pulse method. According to the invention, the method comprises the step of injecting an additional electrical signal into an input of the receiver amplifier to reduce an output signal of the receiver amplifier generated by a first electrical signal.In other words, it is proposed that during a transmission process, an electrical signal from the transmitting amplifier, which is fed to a converter, is attenuated at the input of the receiving amplifier by appropriately applying an additional signal to the input of the receiving amplifier. In this way, the transmitted signal and the additional signal can add up at the amplifier input or within the amplifier itself, such that the output of the receiving amplifier is significantly lower than it would be without the additional electrical signal. According to the invention, the additional electrical signal can be driven by a current source into the direction of a negative terminal of an operational amplifier within the receiving amplifier. Alternatively or additionally, according to the invention, a voltage source is driven to couple a voltage to the positive terminal of the operational amplifier of the receiving amplifier.

[0008] The dependent claims describe preferred embodiments of the invention.

[0009] Preferably, the additional electrical signal can be generated using the first electrical signal. In other words, a signal corresponding to the first electrical signal can be used as the input for generating the additional electrical signal. The additional electrical signal can, in particular, be a substantially phase-synchronous representation of the first electrical signal. This can be achieved, for example, by tapping a voltage at the input of the converter, at the input of the receiving amplifier, or at the output of the transmitting amplifier. Alternatively or additionally, a signal received, stored, and, in particular, adapted during a previous transmission cycle can be read from a memory and used to generate the additional electrical signal.For example, a predefined phase shift between the first electrical signal and the additional electrical signal can ensure that both signals cancel each other out, at least partially, resulting in a significantly reduced output signal from the receiver amplifier.

[0010] The output signal of the receiver amplifier can be used during transmission to test the functionality of a signal converter for environmental sensors. For example, defects or other functional limitations (e.g., contamination, icing, aging, etc.) can be detected by analyzing the receiver amplifier's output signal. Since the electrical characteristics of the converter can vary considerably depending on its functionality, appropriate threshold values ​​can be defined and used in the analysis, allowing for the detection of functional impairments. Analog-to-digital (AID) conversion can be performed to evaluate the receiver amplifier's output signal, providing a wider functional range for analysis.By reducing the output levels of the receiving amplifier according to the invention, quantization for analog-to-digital conversion can be implemented better and more cost-effectively, since the converter can be designed for smaller input signal levels.

[0011] Preferably, the additional electrical signal and / or the first electrical signal can be stored and varied in a predefined manner. An additional electrical signal successfully used to compensate for or reduce the output signal can be stored and used for compensation in subsequent transmissions. Alternatively or additionally, a first electrical signal can be stored, and an additional electrical signal can be generated from its representation for use in a subsequent transmission cycle. Naturally, the variation can include all suitable signal parameters and signal processing algorithms. For example, amplitude adjustment, frequency adjustment, and / or phase adjustment can be performed between a first intermediate signal to be compensated and a compensating additional electrical signal.

[0012] According to a second aspect of the present invention, a device for environmental sensing is proposed. This device comprises a signal converter, a receiver amplifier, and a controllable electrical power source. The device can, for example, be implemented in the form of a parking assistance system. The signal converter can be designed as an acoustic converter, in particular as an ultrasonic converter. The receiver amplifier can be permanently connected to the signal converter, so that it is not, in particular not galvanically, disconnected from the signal converter during a transmission process. In other words, it is also supplied with a first electrical signal during a transmission process. The controllable electrical power source can, for example, be designed as a controllable voltage source and / or as a controllable current source.According to the invention, the signal converter is configured to convert a first electrical signal into a transmitted signal, to transmit this signal into the environment, and to convert an echo of the transmitted signal into an electrical input signal for the receiving amplifier. Furthermore, the electrical power source is configured to feed an additional electrical signal into an input of the receiving amplifier in order to attenuate an output signal of the receiving amplifier generated by the first electrical signal. Regarding the features for realizing the device according to the invention and the associated advantages, reference may be made to the first-mentioned aspect of the invention to avoid unnecessary repetition.

[0013] Furthermore, the device according to the invention can include storage means and signal processing means configured to store the additional electrical signal and / or the first electrical signal and to vary it in a predefined manner. In this way, a successful compensation process can be used to provide input values ​​for a subsequent operating cycle of the device for environmental sensing.

[0014] The receiver amplifier can be advantageously further developed using a voltage-dependent resistor, which, for example, consists of two antiparallel diodes. This voltage-dependent resistor can be used to amplify high-level input signals to the receiver amplifier to a relatively small extent. Conversely, low-level input signals to the receiver amplifier can be amplified to a relatively large extent. For this purpose, the voltage-dependent resistor can, for example, be placed in the feedback path of an operational amplifier within the receiver amplifier. For instance, the voltage-dependent resistor can be connected in parallel to the one connected to... Fig. The feedback resistor R2 shown in diagram 2 should be arranged. The diodes can be designed as Zener diodes. Brief description of the drawings

[0015] Exemplary embodiments of the invention are described in detail below with reference to the accompanying drawings. The drawings show: Fig. 1. A schematic diagram of the construction of an environmental sensor system according to the state of the art; Fig. 2 a circuit diagram of a state-of-the-art receiver amplifier; Fig. 3 a time diagram of an input signal of a receiving amplifier, as occurs in the prior art; Fig. 4 a schematic diagram of an embodiment of an environmental sensor system according to the invention; Fig. 5 a circuit diagram of an embodiment of a receiver amplifier with different further developments according to the invention; Fig. 6 a flowchart illustrating steps of an embodiment of a method according to the invention; Fig. 7 a timing diagram illustrating a receiver amplifier input signal (first electrical signal) and a feedback signal (additional electrical signal); Fig. 8 a logarithmic representation of the in Fig. 7 shown time diagrams; Fig. 9 a time diagram of a receiver amplifier input signal (first electrical signal) and of a receiver amplifier output signal through a counterfeed according to the invention; and Fig. 10 a logarithmic representation of the in Fig. 9 shown time diagrams. Embodiments of the invention

[0016] On the Fig. Points 1 to 3 have already been addressed in the introductory description in connection with the state of the art.

[0017] Fig. Figure 4 shows a schematic diagram of an embodiment of a device for environmental sensing according to the invention. A transducer 2 is electrically connected to a transmitting amplifier 3 and a receiving amplifier 100.

[0018] Both the transmitting amplifier 3 and the receiving amplifier 100 are connected to a data storage device 4 as a storage medium and a microcontroller 5 as a signal processing device. The transmitting amplifier 3 is configured to supply the ultrasonic transducer 2 with electrical signals (first electrical signals), which also reach the input of the receiving amplifier 100. In addition, echoes received by the ultrasonic transducer 2 are recorded and analyzed at the input of the receiving amplifier 100. The functionality of the in Fig. The device shown in section 4 will be discussed in detail in the following figures.

[0019] Fig. Figure 5 shows a receiver amplifier 100 according to the invention, which, compared to the one in Fig. The circuit diagram shown in section 2 exhibits several improvements according to the invention. To avoid repetition, further details are provided below. Fig. 2 referred to. According to the invention, an input 11 of the operational amplifier 1 is connected to a controllable current source i g (τ) B is connected. The input voltage U can be used, for example, as the control variable for the voltage-controlled current source B. e (τ) can be used. Circuit engineers are familiar with how to implement such a control system, so detailed explanations are omitted here. A controllable voltage source u is connected to a second input 12 of the operational amplifier 1. g (τ) A in series with the reference voltage source U ref provided for. The controllable voltage source A can also be used as a control variable, for example an input voltage signal U. e(τ) obtained. A phase shift between the input voltage signal U can occur. e (τ) and the signal of the controllable voltage source A or the signal of the controllable current source B. Depending on the design of the control path and its delay, phase correction can be achieved in this way to minimize the reduction of the output signal U. a (τ) of the receiving amplifier 100 is achieved. Furthermore, a series circuit of two Zener diodes D1 and D2, connected in opposite directions, is provided in parallel with the feedback resistor R2. This series circuit acts as a voltage-dependent resistor whose conductance increases with increasing applied voltage. In this way, a high voltage difference between the output u a(τ) and the input 11 of the operational amplifier 1 to a high conductance of the series connection of the diodes D1, D2 between the terminals 11 and 13, thereby reducing the gain of the receiving amplifier 100.

[0020] Fig. Figure 6 shows a flowchart illustrating the steps of an embodiment of a method according to the invention. The method begins with step 100, in which a first electrical signal is generated to emit an ultrasonic pulse into the environment. In step 200, an additional electrical signal is fed into the input of a receiver amplifier. In step 300, the output signal of the receiver amplifier undergoes analog-to-digital conversion. In step 400, the digital signal is analyzed. This analysis allows, for example, the determination of whether the signal shape, amplitude, or spectral composition indicates a functioning transducer. In this way, for example, icing, contamination, or defects of the transducer diaphragm can be detected.In step 500, the additional electrical signal is stored for later use. In step 600, the stored additional electrical signal is modified or varied. This allows for the correction of unsatisfactory compensation results (for example, due to excessively high or low remaining output signal levels from the receiving amplifier 100). The procedure ends in step 700. Naturally, the described procedure can be carried out identically or with individual steps omitted at the start of a new measurement cycle.

[0021] Fig. Figure 7 shows a time diagram of an input voltage signal U e (τ) of the receiving amplifier and a counter-feedback signal S generated according to the invention g as an additional first signal. The high signal levels of the input voltage signal U e(τ) lead to nonlinear effects in regions 24. In other words, the signal is overdriven in regions 24.

[0022] Fig. 8 is a logarithmic representation of the magnitude of the in Fig. 7 time sequence shown.

[0023] Fig. 9 is a time diagram illustrating the in Fig. 7 shown input voltage signal U e (τ) and an output voltage signal U a (τ) of the receiving amplifier according to the invention is counter-feeded by an additional electrical signal. Compared to the input voltage signal U e (τ) of the receiving amplifier is the level of the output voltage signal U a(τ) is reduced many times over after counterfeeding according to the invention and is far from an overdrive range. In this way, a more cost-effective analog-to-digital conversion can be performed and a precise analysis of the digitized converter signal can be carried out for functional verification. More cost-effective digital-to-analog converters can be used and the lower output levels result in less electromagnetic interference in the entire system.

[0024] Fig. Figure 10 shows a logarithmic representation of the magnitude of the time diagram from Fig. 9.

[0025] A key concept of the present invention is to prevent excessively high output levels of a receiver amplifier during transmission in an environmental sensing system by reducing the electrical signals acting on the receiver amplifier input from the transmitter amplifier. This is achieved by feeding compensation signals into suitable terminals of the receiver amplifier. The receiver amplifier can remain electrically and galvanically connected to the transducer and the transmitter amplifier even during transmission, thus saving on circuit hardware and switching operations. Furthermore, the invention enables cost-effective analysis of the functionality of a transducer used for environmental sensing by allowing the transducer signals recorded during transmission to be examined.

[0026] The invention enables the cost-effective integration of essential features of the device in the form of integrated circuits (ICs). These areas are indicated in the figures of the device by dashed outlines 10. Depending on the desired effect and amplitude of the output signal of the receiving amplifier, the additional electrical signal can be shaped appropriately. For example, a feedback signal can be a sine wave with a fixed frequency of, for example, 48 kHz. This can be weighted with an amplitude weighting function so that the amplitude of the feedback signal decreases significantly over time. Storage processes, which have been mentioned in the preceding description of the invention, can in particular store signal waveforms by storing sampled values. Modifications orVariations in stored signal waveforms can be used, for example, to adapt stored signal waveforms to climate-related factors or to adapt to variations specific to individual samples.

[0027] Even though the aspects of the invention and advantageous embodiments have been described in detail with reference to the exemplary embodiments explained in conjunction with the accompanying drawing figures, modifications and combinations of features of the illustrated exemplary embodiments are possible for the person skilled in the art without leaving the scope of the present invention, the scope of protection of which is defined by the accompanying claims.

Claims

[1] Method for adjusting the dynamic range of a receiver amplifier (100) in an environmental sensor device, comprising the step of injecting (S200) an additional electrical signal (S g ) into the input (11, 12) of the receiving amplifier (100) to reduce an output signal generated due to a first electrical signal (u a ) of the receiving amplifier (100), wherein the additional electrical signal (S g ) by a current source (ig, B) drives a current towards a negative terminal of an operational amplifier (1) inside the receiver amplifier (100) and / or a voltage source (ug, A) is driven to couple a voltage to the positive terminal of the operational amplifier (1) of the receiver amplifier (100). [2] Method according to claim 1, wherein the additional electrical signal (S g) is generated by means of the first electrical signal and is in particular an essentially phase-synchronous mapping of the first electrical signal. [3] Method according to any one of the preceding claims, wherein - the additional electrical signal (S g ) and / or - the first electrical signal is stored (S500) and varied in a predefined manner (S600). [4] Device for environmental sensing comprising - a signal converter (2), - a receiver amplifier (100), - a controllable electrical energy source (ug, ig, A, B), wherein the signal converter (2) is configured to convert a first electrical signal into a transmit signal, to transmit it into the environment and to convert an echo of the transmit signal into an electrical input signal of the receiving amplifier (100), where the electrical energy source (ug, ig, A, B) is set up, an additional electrical signal (S)g ) to feed into the input (11, 12) of the receiving amplifier (100) in order to attenuate an output signal of the receiving amplifier (100) generated on the basis of the first electrical signal. [5] Device according to claim 4, wherein the controllable electrical energy source (ug,ig) is configured to receive a control signal generated by means of the first electrical signal. [6] Device according to claim 4 or 5, wherein the controllable electrical energy source (u g , i g , A, B) a controllable power source (i g ) or a controllable voltage source (u g ) is. [7] Device according to one of claims 4 to 6, wherein the signal transducer (2) is an acoustic signal transducer, which is designed in particular for the ultrasound range. [8] Device according to one of claims 4 to 7, wherein storage means (4) and signal processing means (5) are further provided, which are configured to store the additional electrical signal and / or the first electrical signal and to vary it in a predefined manner. [9] Device according to one of claims 4 to 8, wherein the receiving amplifier (100) is equipped by a voltage-dependent resistor, in particular by two parallel, oppositely directed diodes (D1, D2), to amplify input signals of the receiving amplifier (100) with a high level to a relatively lesser extent than input signals with a lower level, wherein the voltage-dependent resistor is preferably arranged in a feedback branch of the receiving amplifier (100).

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