Ultrasonic sensor

Abstract

The invention relates to a method for operating an ultrasound sensor, comprising emitting a train of ultrasound pulses as a series of ultrasound pulses having a pulse length T1 and a pulse interval T2. The sum of the pulse length T1 and the pulse interval T2 represents that the pulse period length T is equal to T1 + T2. The ultrasonic pulse train starts at a first time t1 and ends at a second time t2. The instantaneous pulse frequency fm, NL = 1 / T corresponds to the reciprocal of the instantaneous pulse length T. The instantaneous pulse frequency fm, NL passes through a first frequency range [Delta] fu during a first time period [Delta] tu, passes through an intermediate frequency range [Delta] fc in a subsequent intermediate time period [Delta] tc, and passes through a second frequency range [Delta] fl in a subsequent second time period [Delta] t2. The time length of the intermediate time period [Delta] tc is equal to or greater than the sum of the first time period [Delta] tu and the second time period [Delta] tl.

Description

Ultrasonic sensor

[0001] This application is a divisional application of patent application No. 202011267685.8, filed on November 13, 2020, entitled "Method for Operating an Ultrasonic Sensor". Technical Field

[0002] This invention relates to a method for operating an ultrasonic sensor using a chirped signal. Background Technology

[0003] DE 10 2017 104 145 A1 discloses a method for operating an ultrasonic sensor device of a motor vehicle by means of excitation through a change in a diaphragm, as well as related ultrasonic sensor devices, driver assistance systems, and motor vehicles. The technical teaching of DE 10 2017 104 145 A1 relates to a method for operating an ultrasonic sensor device of a motor vehicle, wherein a diaphragm in a first ultrasonic sensor is excited to emit a first ultrasonic signal, and a diaphragm in a second ultrasonic sensor is excited to emit a second ultrasonic signal, wherein the diaphragms in the first and second ultrasonic sensors have the same resonant frequency f, and wherein the diaphragm in the first ultrasonic sensor is excited using a first frequency f1 that is lower than the resonant frequency f by a predetermined frequency difference Δf, and the diaphragm in the second ultrasonic sensor is excited using a second frequency f2 that is higher than the resonant frequency f by a predetermined frequency difference Δf. Furthermore, DE 10 2017 104 145 A1 also discloses the idea of ​​changing the frequency difference Δf according to a control signal transmitted to the first and second ultrasonic sensors. DE 10 2017 104 145 A1 also discloses the following idea: the first encoding of the first ultrasonic signal from the first ultrasonic sensor and / or the second encoding of the second ultrasonic signal from the second ultrasonic sensor are provided by frequency shift keying, by phase shift keying as chirp and / or by digital modulation methods.

[0004] DE 10 2017 123 049 B3, DE 10 2017 123 050 B3, DE 10 2017 123 052 B3, and DE 10 2017 123 051 B3 also disclose the use of chirped signals. In these documents, the term "positive chirp-up" is interpreted as a strictly monotonic frequency change of the ultrasonic transmission signal from a lower ultrasonic transmission frequency to a higher ultrasonic transmission frequency, and "negative chirp-down" is understood as a strictly monotonic frequency change of the ultrasonic transmission signal from a higher ultrasonic transmission frequency to a lower ultrasonic transmission frequency.

[0005] What all these documents have in common is that they do not examine or disclose the optimal coding for chirped signals.

[0006] As illustrated in documents DE 10 2017 123 049 B3, DE 10 2017 123 050 B3, DE 10 2017 123 052 B3, and DE 10 2017 123 051 B3, while positive and negative chirps exhibit orthogonal signal shapes, they are only applicable to very large bandwidth-time products. To improve orthogonality, chirped signals can also operate at different center frequencies; however, this significantly increases the bandwidth requirement.

[0007] Based on the technical inspiration from DE 10 2017 104 145 A1, while positive and negative chirped signals exhibit orthogonal signal shapes, this is only applicable to cases with very large bandwidth-time products. Specifically, due to the narrow bandwidth of ultrasonic transducers, the bandwidth can only be chosen to be very small (typically 7 kHz, e.g., 58 Hz + / - 3.5 kHz). Therefore, the inventors of DE 10 2017 104145 A1 proposed in their patent application to separate the center frequencies of the chirped signals from the two ultrasonic transmitters, thereby reducing spectral overlap.

[0008] The purpose of the technical teachings described herein is to minimize spectral overlap beyond that of the prior art without separating the center frequencies too far apart, thereby minimizing the necessary bandwidth.

[0009] Actual testing shows that the method in DE 10 2017 104 145 A1 is ineffective. Therefore, for it to function, the spectra of the two ultrasonic signals (i.e., the two chirped signals) from the two ultrasonic transmitters must actually not overlap. This leads to signal distortion and amplitude reduction because the necessary separation of center frequencies requires the two ultrasonic sensors to operate at frequencies far below their resonant frequencies, resulting in significant damping. This is illustrated in Figure 5.

[0010] JP 2011-038 948 A discloses the use of nonlinear chirp. According to the technical teachings of JP 2011-038 948 A, a method for generating an ultrasonic pulse train includes transmitting the ultrasonic pulse train as a series of ultrasonic pulses, wherein the instantaneous pulse frequency of the ultrasonic pulse train is different at the beginning and end of the pulse train, and wherein the temporal variation of the instantaneous pulse frequency is different at the two different times of the ultrasonic pulse train.

[0011] DE 2017 122 477 A1 discloses a continuous linear variation of the instantaneous pulse frequency of an ultrasonic pulse train during transmission. In the technical teaching of DE 2017 122 477 A1, this variation is used to infer from the received frequency of the echo whether at least one of multiple echoes has been reflected during the transmission phase, or whether this is an overreaction.

[0012] Regarding the term "Ultraschall-Burst", reference is made here, by way of example, to the explanation in paragraph

[0013] of DE 10 2018106 251 A1.

[0013] Here, an ultrasonic pulse train is understood as a continuous fluctuation in air pressure caused by sound waves. An ultrasonic pulse train comprises multiple ultrasonic pulses. The characteristic of an ultrasonic pulse is an increase in air pressure caused by sound waves followed by a decrease in air pressure caused by sound waves.

[0014] A series of ultrasonic pulses having a sequence frequency is referred to hereinafter as an ultrasonic pulse train. Here, the time interval between the pressure rise and the pressure drop caused by the sound wave is understood as the pulse length T1. The time interval between the pressure drop and the pressure rise caused by the sound wave is understood as the pulse interval T2. Then, the temporal pulse period length T = T1 + T2 is the temporal sum of the pulse length T1 and the pulse interval T2. Here, the instantaneous pulse frequency f... m,NL =1 / T corresponds to the reciprocal of the pulse period length T. Summary of the Invention

[0015] Therefore, the object of the present invention is to provide a solution that does not have the aforementioned disadvantages of the prior art and has other advantages. However, the advantages are not limited thereto.

[0016] This objective is achieved through the protected subject matter of this invention. Attached Figure Description

[0017] Figure 1 shows a constant frequency change rate. f / A schematic simplified spectrum of the ultrasonic transmission signal (i.e., the linearly chirped signal) from the ultrasonic transmitter of t, and its non-constant frequency variation rate. f / The spectrum of the ultrasonic transmission signal (i.e., nonlinear chirped signal) of the ultrasonic transmitter t.

[0018] Figure 2 shows the spectrum of a linear positive chirp pulse (rising nonlinear chirp) and the spectrum of a linear negative chirp pulse (falling nonlinear chirp).

[0019] Figure 3 shows the spectrum of a nonlinear positive chirp pulse (rising nonlinear chirp) and the spectrum of a nonlinear negative chirp pulse (falling nonlinear chirp).

[0020] Figure 4 shows exemplary frequency curves of linear and nonlinear chirped signals over time.

[0021] Figure 5 shows the spectra of two ultrasonic signals (i.e., two chirped signals) from two ultrasonic transmitters that must actually not overlap.

[0022] Figure 6 shows the frequency-time curves of the nonlinear positive chirp signal and the nonlinear negative chirp signal.

[0023] Figure 7 shows the instantaneous pulse frequency f of the exemplary nonlinear negative chirped ultrasound pulse train corresponding to Figure 6. m,NL The time curve. Detailed Implementation

[0024] First, as disclosed in DE 10 2017 123 049 B3, DE 10 2017 123 050 B3, DE 10 2017 123 052 B3 and DE 10 2017 123 051 B3, the simplest and most obvious chirp shape is linear chirp, in which, per unit time Frequency change of t f (i.e., the rate of frequency change) f / t) is constant.

[0025] Now, during the establishment of this invention, it has been recognized that the rate of change is at a non-constant frequency. f / t replaces the constant frequency change rate f / It is beneficial to carry out the work.

[0026] The basic idea is to shape the spectra of two ultrasound signals to make them narrower. Therefore, the center frequency interval can be chosen to be smaller. In the technical inspiration of DE 10 2017 104 145 A1, amplitude weighting for spectral shaping and sidelobe reduction is proposed. This will be illustrated by Figures 1 through 7.

[0027] Figure 1 shows a constant frequency change rate. f / A schematic simplified spectrum of the ultrasonic transmission signal (i.e., the linearly chirped signal) from the ultrasonic transmitter of t, and its non-constant frequency variation rate. f / The spectrum of the ultrasonic transmission signal (i.e., the nonlinear chirped signal) from the ultrasonic transmitter t. It can be easily seen that the spectrum of the nonlinear chirped signal is narrower than that of the linear chirped signal. The preferred nonlinear chirped signal will be further explained below.

[0028] Now, suppose we use a first ultrasonic sensor that emits a linearly chirped signal with a first center frequency f1 and a second ultrasonic sensor that emits a linearly chirped signal with a second center frequency f2. The first center frequency f1 and the second center frequency f2 should have a center frequency interval Df. 12 =f1-f2.

[0029] If the center frequency interval Df 12 If the bandwidth is less than that of a linear chirped signal, they will overlap.

[0030] This situation is illustrated in Figure 2.

[0031] If nonlinear chirped signals are used at different start frequencies, the narrower spectrum of the two nonlinear chirped signals results in less overlap between them.

[0032] This situation is illustrated in Figure 3. Figure 6 shows the corresponding frequency curves of the nonlinear positive chirped signal and the nonlinear negative chirped signal over time.

[0033] Figure 4 shows exemplary frequency curves of linear and nonlinear chirped signals over time. They correspond to the signal curves shown in Figure 2.

[0034] This scheme can be summarized as follows: by using nonlinear chirping, the spectrum of the chirped signal can be shaped to have a narrower frequency band, thereby significantly reducing the bandwidth requirement without reducing the signal-to-noise ratio.

[0035] Therefore, this scheme describes a method for operating an ultrasonic sensor, which includes the step of transmitting an ultrasonic pulse train as a series of ultrasonic pulses. The ultrasonic pulses have a pulse length T1 and a pulse interval T2. Here, the sum of the pulse length T1 and the pulse interval T2 is the pulse period length T = T1 + T2. Here, the ultrasonic pulse train begins at a first time t1 and ends at a second time t2. Here, the instantaneous pulse frequency f... m,NL =1 / T corresponds to the reciprocal of the pulse period length T. Here, the pulse period length T at the first time t1 and therefore the instantaneous pulse frequency f m =1 / T differs from the pulse period length T and therefore the instantaneous pulse frequency f of the second time t2. m =1 / T.

[0036] The instantaneous pulse frequency f of a nonlinear chirped pulse at time (t) m,NL(t) can be expressed by the following equation:

[0037]

[0038] The above formulas only concern the start time t of the ultrasound pulse between the first time t1 and the second time t2, or only the end time t of the ultrasound pulse between the first time t1 and the second time t2. In this respect, the above formulas do not specify a continuous curve, but rather discrete values ​​of discrete times t between the first time t1 and the second time t2. In fact, the instantaneous pulse frequency f... m,NL The deviation of (t) from the curve is numerically less than 10%, preferably less than 5%, preferably less than 2%, preferably less than 1%, and preferably less than 0.5%. Therefore, the instantaneous pulse frequency f m,NL (t) essentially follows the formula above. Therefore, the instantaneous pulse frequency change of the nonlinear chirped pulse... f m,NL / t is not constant. Here, B L B is the bandwidth coefficient of the linear part. C It is the bandwidth coefficient of the nonlinear part.

[0039] Here, at least the instantaneous pulse frequency change at the third time t3 between the first time t1 and the second time t2. f m,NL / The instantaneous pulse frequency change t is different from that of the fourth time t4 between the first time t1 and the second time t2. f m,NL / t.

[0040] Conversely, the instantaneous pulse frequency f of a linear chirped pulse at time t... m,L (t) can be expressed by the following equation:

[0041]

[0042] Therefore, the instantaneous pulse frequency change of a linear chirped pulse f m,NL / t is constant.

[0043] Figure 1 shows the spectrum of linear chirp (linear chirp) and the spectrum of nonlinear chirp (nonlinear chirp).

[0044] Alternatively, the scheme may also have the following characteristics: the spectral bandwidth of a nonlinear chirped ultrasound pulse train is reduced by more than 25% and / or preferably more than 30% and / or preferably more than 35% relative to the spectral bandwidth of a linear chirped ultrasound pulse train with respect to the -3dB level of its corresponding spectral amplitude maximum.

[0045] Figure 3 shows the spectrum of a nonlinear positive chirp pulse (rising nonlinear chirp) and the spectrum of a nonlinear negative chirp pulse (falling nonlinear chirp).

[0046] As an alternative to the two features described above, the scheme may further be characterized in that the spectrum of the nonlinear positive chirped pulse at the intersection with the spectrum of the nonlinear negative chirped pulse is reduced by at least -12 dB compared to the maximum value. Simultaneously, the spectrum of the nonlinear negative chirped pulse at the intersection with the spectrum of the nonlinear positive chirped pulse is reduced by at least -12 dB compared to the maximum value.

[0047] In a variation of these three basic methods, the instantaneous pulse frequency change of the nonlinear chirped pulse... f m,NL / The frequency t decreases monotonically or increases monotonically between the first time t1 and the second time t2. Particularly preferably, the instantaneous pulse frequency change of the nonlinear chirped pulse... f m,NL / t either decreases or increases strictly monotonically between the first time t1 and the second time t2.

[0048] In the second variation of these three basic methods, the temporal variation of the instantaneous pulse frequency of the nonlinear chirped pulse is... 2 f m, NL / t 2 (That is, the rate of change of the instantaneous pulse frequency) monotonically decreases or monotonically increases between the first time t1 and the second time t2. Particularly preferred is the time-varying nature of the instantaneous pulse frequency change of the nonlinear chirped pulse. 2 f m, NL / t 2 (That is, the instantaneous pulse frequency change of the nonlinear chirped pulse) f m, NL / The rate of change of t over time is either strictly monotonically decreasing or strictly monotonically increasing between the first time t1 and the second time t2.

[0049] Particularly preferred is the instantaneous pulse frequency change of the nonlinear chirped pulse between the first time t1 and the second time t2. f m, NL / The temporal curve of the value of t has a minimum value.

[0050] In the third broad variant of these three basic methods, the instantaneous pulse frequency variation of the non-linear chirped pulse between the first time t1 and the second time t2 f m, NL / The temporal variation of t 2 f m, NL / t 2 is constant at least at a third time t3 (where t1 < t3 < t2), and thus is applicable at this time t3 3 f m, NL / t 3 = 0.

[0051] FIG. 7 shows the frequency curve better. In FIG. 7, only the instantaneous pulse frequency f of an exemplary non-linear negative chirped ultrasonic pulse train is shown m,NL as a function of time. It corresponds to the negative chirped ultrasonic pulse train of FIG. 6. The following description will of course apply in a similar manner to an exemplary non-linear positive chirped ultrasonic pulse train and will not be repeated here. It corresponds to the positive chirped ultrasonic pulse train of FIG. 6. The claimed solution of the present invention also includes the time sequence of a plurality of sub ultrasonic pulse trains in the form of an overall ultrasonic pulse train, in which at least one sub ultrasonic pulse train is an ultrasonic pulse train according to that described herein.

[0052] The above-described method for operating an ultrasonic sensor can also be characterized differently. Another feature emphasizes that the instantaneous pulse frequency f m,NL differs only slightly from the intermediate instantaneous pulse frequency f c over a relatively long period of time. The frequency deviation is only relatively large over a relatively short period of time at the start and end of the ultrasonic pulse train.

[0053] Particularly preferably, the intermediate instantaneous pulse frequency f of the ultrasonic pulse train c does not deviate from the frequency of the ultrasonic transmitter and / or ultrasonic transducer used. If the instantaneous pulse frequency f c deviates from this resonance frequency only over a relatively short period of time during the transmission of the ultrasonic pulse train, the ultrasonic transmitter or ultrasonic transducer can transmit with almost maximum transmission power over a relatively long period within the transmission period of the ultrasonic pulse train. Thus, when used in an ultrasonic parking assistance system of a motor vehicle, the range of the system is maximized and significantly exceeds the range of a system with a linear chirp. The resonance frequency of the ultrasonic transducer or ultrasonic transmitter and the intermediate instantaneous pulse frequency f cThis correspondence can be expressed quantitatively. In the context of this invention, this frequency can be assumed to be the resonant frequency of the ultrasonic transducer or ultrasonic transmitter, at which the acoustic power radiated from the relevant ultrasonic transducer or ultrasonic transmitter is maximum. Therefore, particularly preferably, in the ultrasonic pulse train transmission method proposed herein, the intermediate instantaneous pulse frequency f of the ultrasonic pulse train... c The deviation from the resonant frequency or rated frequency of the ultrasonic transmitter shall not exceed 10% and / or preferably not exceed 5% and / or preferably not exceed 2% and / or preferably not exceed 1% and / or preferably not exceed 0.5% and / or preferably not exceed 0.2% and / or preferably not exceed 0.1% and / or preferably not exceed 0.05% and / or preferably not exceed 0.02% and / or preferably not exceed 0.01%, and / or the deviation from the resonant frequency or rated frequency of the ultrasonic transducer shall not exceed 10% and / or preferably not exceed 5% and / or preferably not exceed 2% and / or preferably not exceed 1% and / or preferably not exceed 0.5% and / or preferably not exceed 0.2% and / or preferably not exceed 0.1% and / or preferably not exceed 0.05% and / or preferably not exceed 0.02% and / or preferably not exceed 0.01%.

[0054] As previously described, the transmission of an ultrasonic pulse train is performed as a series of ultrasonic pulses having a pulse length T1 and a pulse interval T2. The pulse length T1 and pulse interval T2 represent the pulse period length T = T1 + T2 as the sum of the times from the start of one pulse to the start of the next. The ultrasonic pulse train begins at a first time t1 and ends at a second time t2. The start of the ultrasonic pulse train begins with the start of the first pulse in the ultrasonic pulse train. In the context of this paper, the ultrasonic pulse train ends after a period of time corresponding to the pulse interval T2 between the last pulse and the penultimate pulse of the ultrasonic pulse train, where the elapsed time begins from the end of the last pulse of the ultrasonic pulse train. In the context of this paper, the time at which this elapsed time is the second time t2.

[0055] Therefore, the ultrasonic pulse train has a time length Δt. s =t2-t1. Here, at time t during the ultrasonic pulse train (t1≤t≤t2), the instantaneous pulse frequency f m,NL =|1 / T| numerically corresponds to the reciprocal of the instantaneous pulse period length T. The pulse period length T at the first time t1 and the resulting instantaneous pulse frequency f will be discussed below. m,NL =|1 / T| is called the first instantaneous pulse frequency f. u And the pulse period length T of the second time t2 and the therefore instantaneous pulse frequency f m,NL =|1 / T| is called the second instantaneous pulse frequency fl Preferably, the first instantaneous pulse frequency f u Unlike the second instantaneous pulse frequency f l As mentioned above, the ultrasonic pulse train has an intermediate instantaneous pulse frequency f. c =|f u -f l | / 2. In the following text, the instantaneous pulse frequency f m,NL The total change of |1 / T| between the first time t1 and the second time t2 is called the total frequency change Δf. s Here, the first boundary frequency f cu The frequency is as follows, which is different from the frequency f of the first instantaneous pulse. u The frequency interval between it and the second instantaneous pulse frequency f l The frequency value interval is half of the frequency value interval. Here, the second boundary frequency f cl The frequency is as follows, and the frequency interval between this frequency and the second instantaneous pulse frequency f1 is equal to the interval between the first instantaneous pulse frequency f1 and f2. u The frequency value interval is half of the frequency value interval. Preferably, the instantaneous pulse frequency f m,NL First boundary time t cu Equal to the first boundary frequency f cu Preferably, the instantaneous pulse frequency f m,NL Second boundary time t cl Equal to the second boundary frequency f cl First boundary time t cu Preferably, in time, it occurs after the first time t1 and at the second boundary time t. cl Preferably, in time, at the first boundary time t cu Subsequently, and preferably at the second boundary time t2, the second time t2 is in time at the second boundary time t cl Subsequently, preferably, starting from the first time t1 and ending at the first boundary time t... cu The first time period Δt ends u During this period, the instantaneous pulse frequency f m,NL The pulse frequency f at the first instant u and the first boundary frequency f cu The first frequency range Δf between u The pulse frequency f is at the first instant. u and the first boundary frequency f cu Between. Preferably, from the first boundary time t cu Start at the second boundary time t cl The middle period Δt at the end c During this period, the instantaneous pulse frequency f m,NL First boundary frequency f cu Second boundary frequency f cl The intermediate frequency range Δfc The inner frequency is at the first boundary frequency f cu Second boundary frequency f cl Between. Preferably, from the second boundary time t cl The second time interval Δt begins and ends at the second time t2. l During this period, the instantaneous pulse frequency f m,NL Second boundary frequency f cl The second frequency range Δf between the second instantaneous pulse frequency f1 and the second instantaneous pulse frequency f1 l The inner frequency is at the second boundary frequency f cl Between the second instantaneous pulse frequency f1. The decisive factor here is the intermediate time interval Δt. c The duration is greater than the first period Δt u The duration of the second period Δt l The sum of durations, or the intermediate time interval Δt c The duration is equal to the first time interval Δt u The duration of the second period Δt l The sum of the durations. Therefore, the focus of sound transmission can be initially placed on the resonant frequency of the ultrasonic transducer or ultrasonic transmitter, thereby maximizing the range of the ultrasonic parking assist system.

[0056] Therefore, preferably, the instantaneous pulse frequency change at least at a third time t3 between the first time t1 and the second time t2. f m, NL / The instantaneous pulse frequency change t is different from the first time t1 and the second time t2, at least the fourth time t4. f m, NL / t.

[0057] Preferably, the instantaneous pulse frequency f between the first time t1 and the second time t2 is... m,NL (t) can be expressed by the following equation:

[0058]

[0059] Among them, B L B is the bandwidth coefficient of the linear part. C It is the bandwidth coefficient of the nonlinear part.

[0060] Preferably, the instantaneous pulse frequency change f m, NL / t decreases or increases monotonically again between the first time t1 and the second time t2.

[0061] Preferably, the temporal variation of the instantaneous pulse frequency change 2 f m, NL / t 2 It either decreases monotonically or increases monotonically between the first time t1 and the second time t2.

[0062] However, the instantaneous pulse frequency change is a temporal variation between the first time t1 and the second time t2. 2 f m, NL / t 2 It can also be constant.

[0063] The temporal variation of instantaneous pulse frequency change between the first time t1 and the second time t2 3 f m, NL / t 3 It can also be constant.

[0064] Preferably, relative to a constant instantaneous pulse frequency variation f m, NL / The spectral width of the ultrasonic pulse train spectrum with respect to the spectrum at a level of -3 dB relative to its maximum amplitude, wherein the spectral width of the ultrasonic pulse train spectrum with respect to the ultrasonic pulse train spectrum at a level of -3 dB relative to its maximum amplitude is reduced by more than 25% and / or preferably reduced by more than 30% and / or preferably reduced by more than 35%.

[0065] As described above, the transmission of the entire ultrasound pulse train can also be performed as a direct temporal sequencing of the transmission of partial ultrasound pulse trains, wherein at least some of these partial ultrasound pulse trains (preferably, all of the partial ultrasound pulse trains) correspond to one of the methods described above.

[0066] advantage

[0067] Instead of amplitude weighting, which also reduces the signal-to-noise ratio, the dwell time of the ultrasonic transmitter system can also be adjusted for each instantaneous pulse frequency f. m Optimization is performed to best shape the spectrum. This leads to the use of nonlinear chirp. Practical tests show that this can reduce the center frequency interval of the spectra of two different ultrasonic pulse trains from two different ultrasonic transmitters, for example, from 7 kHz to 4 kHz. The nonlinear chirped signals can even overlap slightly here. The signal amplitude and waveform (including sidelobe reduction) and the signal-to-noise ratio become better.

[0068] Due to the instantaneous pulse frequency f in the middle of the ultrasonic pulse train cPreferably, it does not deviate from the frequency of the ultrasonic transmitter and / or ultrasonic transducer used, and due to the instantaneous pulse frequency f c During the transmission of the ultrasonic pulse train, the frequency deviates from the resonant frequency only for a relatively short period and only slightly. Therefore, the ultrasonic transmitter or transducer can transmit at almost maximum power for a relatively long period within the transmission time of the ultrasonic pulse train. Consequently, when applied to ultrasonic parking assist systems in automobiles, the range of this system is maximized and significantly exceeds that of systems with linear chirp.

[0069] List of cited references

[0070] DE 10 2017 104 145 A1; DE 10 2017 123 049 B3; DE 10 2017 123 050 B3; DE10 2017 123 052 B3; DE 10 2017 123 051 B3; JP 2011-038 948 A; DE 2017 122 477; DE10 2018 106 251 A1

Claims

1. An ultrasonic sensor, comprising: Ultrasonic diaphragm; and a control unit configured to generate and transmit an ultrasonic pulse train, wherein the transmission of at least one of the partial ultrasonic pulse trains corresponds to a method comprising transmitting the partial ultrasonic pulse train as a series of ultrasonic pulses having a pulse length T1 and a pulse interval T2, wherein the sum of the pulse length T1 and the pulse interval T2 is equal to the pulse period length T = T1 + T2, and wherein the partial ultrasonic pulse train begins at a first time t1 and ends at a second time t2, and wherein the instantaneous pulse frequency f m,NL =1 / T corresponds to the reciprocal of the pulse period length T, and wherein the pulse period length T at the first time t1 and therefore the instantaneous pulse frequency f m,NL =1 / T is different from the pulse period length T and therefore the instantaneous pulse frequency f at the second time t2. m,NL =1 / T, and wherein the change in the instantaneous pulse frequency at least at a third time t3 between the first time t1 and the second time t2. f m, NL / t is different from the change in the instantaneous pulse frequency at least at a fourth time t4 between the first time t1 and the second time t2. f m, NL / t。

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