Signal processing device, ultrasonic sensor, and vehicle

Abstract

To provide a signal processing device that can achieve both a shortened reverberation time and improved noise removal performance.SOLUTION: A signal processing device (101A) comprises: a masking unit (10) configured to output a mask signal (MSK) by changing a level of the mask signal when a level of a comparison signal (CMP) output from a comparator (9) is maintained for a prescribed dead time (Td) after a level change, and to maintain the level of the mask signal at an immediately preceding level if the level of the comparison signal changes before the dead time has elapsed after the level change; and a dead time generating unit (13) configured to generate the dead time such that the dead time in a first period (T1) from a start of driving an ultrasonic sensor element (1) becomes shorter than the dead time in a second period (T2) after the first period.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present disclosure relates to a signal processing device. [Background technology]

[0002] Conventionally, the time it takes for an ultrasonic wave to be emitted and for the reflected wave to return from an obstacle was measured. Ultrasonic sensors are known that measure the distance to an obstacle by measuring the distance of the obstacle. (For example, Patent Document 1) Such ultrasonic sensors are often mounted on vehicles, and an on-board clearance sonar is known as one example. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2020 / 004609

[0004] [overview] Even if the drive of the ultrasonic sensor element is stopped, the mechanical vibration of the ultrasonic sensor element continues. If a reflected wave reflected by a nearby object is received while such reverberation is occurring, the distance cannot be measured. Therefore, it is desirable to shorten the reverberation time as much as possible. On the other hand, there is also a demand for improved noise removal performance to remove the effects of noise contained in the reflected wave signal generated based on the output from the ultrasonic sensor element.

[0005] In view of the above circumstances, an object of the present disclosure is to provide a signal processing device that is capable of achieving both a reduction in reverberation time and an improvement in noise removal performance.

[0006] A signal processing device according to an embodiment of the present disclosure includes: a drive circuit configured to drive the ultrasonic sensor element; a receiving circuit configured to output a receiving signal based on an output of the ultrasonic sensor element; a reflected wave signal generating unit configured to generate a reflected wave signal by performing a detection process based on the received signal; a comparator configured to compare the reflected wave signal with a threshold value and output a comparison signal as a comparison result; a masking unit configured to output the mask signal by changing the level of the mask signal when the level of the comparison signal is maintained for a predetermined dead time after the level change, and to maintain the level of the mask signal at the immediately preceding level when the level of the comparison signal is changed before the dead time has elapsed after the level change; a dead time generating unit configured to generate the dead time such that the dead time in a first period from the start of driving of the ultrasonic sensor element is shorter than the dead time in a second period after the first period; The configuration is provided with the following. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram showing an example in which an ultrasonic sensor is applied to a vehicle. [Diagram 2] FIG. 2 is a diagram showing a configuration of an ultrasonic sensor according to a comparative example. [Diagram 3] FIG. 3 is a timing chart showing a first operation example of the ultrasonic sensor. [Figure 4] FIG. 4 is a diagram showing an example of waveforms for explaining the operation of the masking unit. [Diagram 5] FIG. 5 is a diagram illustrating an example of the configuration of the masking unit. [Figure 6] FIG. 6 is a diagram illustrating a configuration of an ultrasonic sensor according to the first embodiment of the present disclosure. [Figure 7] FIG. 7 is a diagram illustrating a configuration of an ultrasonic sensor according to the second embodiment of the present disclosure. [Figure 8] FIG. 8 is a timing chart showing a second operation example of the ultrasonic sensor. [Figure 9] FIG. 9 is a timing chart showing a third operation example of the ultrasonic sensor.

[0008] [Detailed Description] Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the drawings.

[0009] <Ultrasonic sensors installed in vehicles> 1 shows a vehicle 200 equipped with an ultrasonic sensor 10X and an object (obstacle) 300. Ultrasonic waves transmitted from the ultrasonic sensor 10X are reflected by the object 300 and received as reflected waves by the ultrasonic sensor 10X. The ultrasonic sensor 10X measures distance by measuring the time from when the ultrasonic wave is transmitted to when it is received. Various ultrasonic sensors described below can be used as the ultrasonic sensor 10X, but the application of ultrasonic sensors is not limited to vehicles.

[0010] <Comparative Example> 2 is a diagram showing the configuration of an ultrasonic sensor 100 according to a comparative example. The ultrasonic sensor 100 includes an ultrasonic sensor element (hereinafter, sensor element) 1 and a signal processing device 100A. The signal processing device 100A is an IC (integrated circuit) that integrates a drive circuit 2, a receiving circuit 3, an ADC 4, a reflected wave signal generating unit 5, a multiplier 6, a gain value control unit 7, a threshold generating unit 8, a comparator 9, a masking unit 10, a signal selecting unit 11, and a communication terminal 12. Note that the circuit configuration in the signal processing device does not necessarily have to be configured as an IC.

[0011] The sensor element 1 is made up of a piezoelectric element and is externally connected to the signal processing device 100A.

[0012] The driving circuit 2 is a circuit that drives the sensor element 1. When the driving circuit 2 pulse-drives the sensor element 1, the sensor element 1 vibrates and an ultrasonic wave is transmitted from the sensor element 1. When the sensor element 1 vibrates due to, for example, receiving a reflected ultrasonic wave, it outputs a sensor output signal SS.

[0013] The receiving circuit 3 is a circuit that receives and processes the sensor output signal SS. The receiving circuit 3 has an LNA (low noise amplifier) ​​and an LPF (low pass filter), etc. The LNA can amplify the weak sensor output signal SS. The receiving circuit 3 outputs a receiving signal RS as a result of processing the sensor output signal SS.

[0014] An ADC (AD converter) 4 converts the received signal RS, which is an analog signal, into a digital signal DS.

[0015] The reflected wave signal generator 5 performs detection processing on the digital signal DS to generate a reflected wave signal WS1. For example, envelope detection or quadrature demodulation is used as the detection method. The gain value controller 7 performs time-dependent variable control of the gain value G by which the reflected wave signal WS1 is multiplied. The multiplier 6 multiplies the reflected wave signal WS1 by the gain value G to generate a reflected wave signal WS2.

[0016] The threshold generator 8 performs time-dependent variable control of the threshold TH to be input to the comparator 9. The comparator 9 compares the reflected wave signal WS2 with the threshold TH, and outputs a comparison signal CMP as a comparison result. The comparison signal CMP can be either a high level or a low level.

[0017] The masking unit 10 performs a masking process on the comparison signal CMP to output a mask signal MSK. The masking process will be described in detail later.

[0018] The signal selection unit 11 selects one of the comparison signal CMP and the mask signal MSK and outputs it as an output signal OUT. The output signal OUT is output to the outside via a communication terminal 12.

[0019] Fig. 3 is a timing chart showing an example of the operation of the ultrasonic sensor 100 according to the comparative example. In Fig. 3, from the top, waveform examples of the reflected wave signal WS2, the gain value G, the threshold value TH, the comparison signal CMP, and the mask signal MSK are shown. Note that in Fig. 3, the mask signal MSK and the dead time Td according to the embodiment of the present disclosure, which will be described later, are also shown in the bottom. Note that the way in which the gain value G and the threshold value TH are changed over time in Fig. 3 is merely an example.

[0020] The operation of the comparative example will be described with reference to Fig. 3. First, when the driving circuit 2 starts driving the sensor element 1 (timing t0), the sensor element 1 starts transmitting ultrasonic waves, and the driving signal from the driving circuit 2 is input directly to the receiving circuit 3, causing the reflected wave signal WS2 to rise. Then, when the reflected wave signal WS2 exceeds the threshold value TH (timing t1), the comparison signal CMP switches from high level to low level.

[0021] At timing t2, the drive of the sensor element 1 is stopped, but the mechanical vibration of the sensor element 1 continues, causing reverberation. At this time, the level of the reflected wave signal WS2 is maintained by the vibration waveform of the sensor output signal SS. After that, when the reverberation ends, the reflected wave signal WS2 falls. At this time, when the reflected wave signal WS2 becomes equal to or lower than the threshold value TH (timing t3), the comparison signal CMP switches to a high level.

[0022] After that, the threshold value TH decreases at time t4 and becomes constant at time t5. After that, the gain value G increases at time t6 and becomes constant at time t7. Since the reflected wave from the obstacle attenuates depending on the distance, the gain value G is increased over time.

[0023] After that, noise Ns occurs in the reflected wave signal WS2. Such noise is caused, for example, by noise originally contained in the sensor output signal SS as an acoustic signal or an electrical signal, or by a change in the level of the output signal OUT leaking from the communication terminal 12 to the sensor output signal SS (capacitive coupling, etc.).

[0024] 3, the reflected wave signal WS2 exceeds the threshold value TH at time t8, causing the comparison signal CMP to switch to a low level. Then, the reflected wave signal WS2 falls below the threshold value TH at time t9, causing the comparison signal CMP to switch to a high level. In this way, when noise Ns occurs near the threshold value TH, an unstable level change occurs in the comparison signal CMP.

[0025] In the example of Fig. 3, after the noise Ns, the waveform of the reflected wave signal WS is generated by the reflected wave, and at timing t10, the reflected wave signal WS2 exceeds the threshold value TH, causing the comparison signal CMP to switch to a low level. After that, the comparison signal CMP is maintained at a low level for a relatively long time. Then, at timing t11, when the reflected wave signal WS2 becomes equal to or lower than the threshold value TH, the comparison signal CMP switches to a high level.

[0026] In order to suppress the influence of such noise Ns, a masking unit 10 is provided. The masking unit 10 is also called a debounce circuit (or a chattering cancellation circuit). Fig. 4 is a diagram showing an example of waveforms for explaining the operation of the masking unit 10. In Fig. 4, from the top to the bottom, an input signal Sin to the masking unit 10 and an output signal Sout from the masking unit 10 are shown.

[0027] The masking unit 10 changes the level of the output signal Sout when the level of the input signal Sin is maintained for a predetermined dead time Td after the level change, and maintains the level of the output signal Sout at the previous level when the level of the input signal Sin changes before the dead time Td has elapsed after the level change. Note that in the comparative example, the dead time Td is a fixed value.

[0028] Explaining using the example shown in FIG. 4, when the input signal Sin changes from a high level to a low level at timing ta, the input signal Sin changes to a high level at timing tb before the lapse of a certain dead time Td from timing ta, so that the output signal Sout maintains the previous high level. After that, when the input signal Sin changes from a high level to a low level at timing tc, the input signal Sin is maintained at a low level for the dead time Td from timing tc, so that the output signal Sout changes from a high level to a low level at timing td. After that, when the input signal Sin changes from a low level to a high level at timing te, the input signal Sin changes to a low level at timing tf before the lapse of the dead time Td from timing te, so that the output signal Sout maintains the previous low level. After that, when the input signal Sin changes from a low level to a high level at timing tg, the input signal Sin is maintained at a high level for the dead time Td from timing tg, so that the output signal Sout changes from a low level to a high level at timing th. In this manner, the input signal Sin (from ta to tb and from te to tf) whose level is maintained for a short period is masked.

[0029] 5 is a diagram showing an example of the configuration of the masking unit 10. The masking unit 10 has a successive match counter 10A, a count value comparator 10B, and an output latch unit 10C.

[0030] The consecutive coincidence counter 10A starts counting time when triggered by a level change of the input signal Sin, and continues counting while the level of the input signal Sin is consistent. The consecutive coincidence counter 10A initializes the count when triggered by a level change of the input signal Sin.

[0031] The count value comparator 10B compares the count value CNT by the successive coincidence counter 10A with the dead time Td, and outputs a comparison output CP as a comparison result. The count value comparator 10B outputs a comparison output CP of a first level (e.g., low level) if the count value has not reached the dead time Td, and outputs a comparison output CP of a second level (e.g., high level) if the count value is equal to or greater than the dead time Td.

[0032] When the comparison output CP changes from the first level to the second level, the output latch unit 10C outputs the output signal Sout with the level of the input signal Sin as the level of the output signal Sout. In other cases, the output latch unit 10C holds the level of the output signal Sout. The output latch unit 10C is configured by, for example, a flip-flop.

[0033] For example, in the example of FIG. 4, when the input signal Sin changes to a low level at timing ta, the count is initialized and the count value CNT rises. Then, at timing tb before the dead time Td is reached, the input signal Sin changes to a high level, so the count is initialized and the count value CNT rises. After that, when the input signal Sin changes to a high level at timing tc, the count is initialized and the count value CNT rises. Then, at timing td, the count value CNT reaches the dead time Td, so the comparison output CP switches from the first level that was maintained from timing ta to td to the second level. As a result, the output latch unit 10C sets the low level, which is the level of the input signal Sin, to the level of the output signal Sout, and the output signal Sout changes from the high level to the low level.

[0034] After that, the count value CNT continues to rise, and the comparison output CP maintains the second level. Then, when the input signal Sin changes to a high level at timing te, the count is initialized and the count value CNT rises. At this time, the comparison output CP switches to the first level. Then, at timing tf before the dead time Td is reached, the input signal Sin changes to a low level, so the count is initialized and the count value CNT rises. Then, when the input signal Sin changes to a high level at timing tg, the count is initialized and the count value CNT rises. Then, at timing th, the count value CNT reaches the dead time Td, so the comparison output CP switches from the first level that was maintained from timing te to tg to the second level. As a result, the output latch unit 10C sets the high level, which is the level of the input signal Sin, to the level of the output signal Sout, and the output signal Sout changes from the low level to the high level.

[0035] As shown in Fig. 2, the input signal Sin of the masking 10 is the comparison signal CMP, and the output signal Sout is the mask signal MSK. In Fig. 3, the behavior of the mask signal MSK according to the comparative example will be described. At timing t1, the comparison signal CMP changes to a low level, and since the comparison signal CMP maintains its level for the dead time Td from timing t1, the mask signal MSK changes to a low level. After that, at timing t3, the comparison signal CMP changes to a high level, and since the comparison signal CMP maintains its level for the dead time Td from timing t3, the mask signal MSK changes to a high level.

[0036] After that, the comparison signal CMP changes to a low level at timing t8, and changes to a high level at timing t9 before the dead time Td has elapsed from timing t8, so the level of the mask signal MSK is maintained at the previous high level. Then, the comparison signal CMP changes to a low level at timing t10 ​​before the dead time Td has elapsed from timing t9, so the level of the mask signal MSK is maintained at the previous high level.

[0037] Since the comparison signal CMP maintains its level for the dead time Td from timing t10, the mask signal MSK changes to a low level. After that, the comparison signal CMP changes to a high level at timing t11, and since the comparison signal CMP maintains its level for the dead time Td from timing t11, the mask signal MSK changes to a high level.

[0038] In this way, the effect of the noise Ns can be suppressed by the masking unit 10, but the dead time Td corresponds to the delay time of the mask signal MSK relative to the comparison signal CMP. This delay time is relatively unproblematic for detecting reflected waves at long distances, but the following problem occurs for short-distance detection. As shown in Fig. 3, the time from the timing t1 when the reflected wave signal WS2 exceeds the threshold value TH to the timing when the mask signal MSK changes to a high level is the reverberation time Trv, but the reverberation time Trv is extended by a delay equivalent to the dead time Td (hatched in Fig. 3).

[0039] If the sensor element 1 receives a wave reflected by a nearby object during the reverberation time Trv, the reflected wave cannot be detected. As described above, if the reverberation time Trv becomes long, it affects the performance of short-distance measurement (short-distance measurement limit distance).

[0040] First Embodiment In view of the above problems, the following embodiments of the present disclosure are implemented. Fig. 6 is a diagram showing a configuration of an ultrasonic sensor 101 according to a first embodiment of the present disclosure. The ultrasonic sensor 101 has a signal processing device 101A. The signal processing device 101A has a dead time generating unit 13 as a difference from the comparative example (Fig. 2).

[0041] The dead time generating section 13 generates a variable dead time Td according to the gain value G generated by the gain value control section 7. The larger the gain value G, the longer the dead time Td becomes.

[0042] An example of such an operation according to the first embodiment will be described with reference to Fig. 3. The lower part of Fig. 3 shows an example of the behavior of the mask signal MSK and the dead time Td according to this embodiment.

[0043] Since the dead time generation unit 13 links the dead time Td with the gain value G, the dead time Td is set to be relatively short during the timings t0 to t6 when the gain value G is low. In the example of Fig. 3, since Td = 0, the level of the mask signal MSK changes simultaneously at the timings t1 and t3 when the level of the comparison signal CMP changes.

[0044] After that, from timing t6 to t7, the gain value G increases, so the dead time Td also increases. Then, after timing t7, the gain value G becomes constant, so the dead time Td also becomes constant.

[0045] In other words, the dead time Td in the first period T1 (timings t0 to t6) from the start of driving of the sensor element 1 is generated so as to be shorter than the dead time Td in the second period T2 following the first period.

[0046] As a result, by shortening the dead time Td immediately after transmitting the ultrasonic waves, the delay due to the dead time Td can be reduced and the reverberation time Trv can be shortened. Therefore, the performance of short-distance measurement can be improved. When the gain value is low, the noise is also small, so even if the masking effect is low, it does not cause a problem, and the dead time Td is shortened in the first period T1. In addition, by lengthening the dead time Td as time passes (as the gain value G increases), the stability of reflected wave detection at long distances where noise is a problem can be improved. In this way, it is possible to achieve both noise removal performance and shortened reverberation time.

[0047] <Second embodiment> 7 is a diagram showing a configuration of an ultrasonic sensor 102 according to a second embodiment of the present disclosure. The ultrasonic sensor 102 includes a signal processing device 102A. A difference from the first embodiment is that the dead time generating unit 13 starts measuring time using the timer 13A from the start of driving the sensor element 1, and generates the dead time Td according to the measured time. This allows the dead time Td to be set with a higher degree of freedom than in the first embodiment.

[0048] In this embodiment, the behavior of the dead time Td may be as shown in FIG. 3, but the dead time Td may continue to increase even after timing t7, for example.

[0049] In this embodiment, as shown in Fig. 8 as an operation example different from Fig. 3, when the dead time Td is increased from timing t6 to timing t7, it may be increased in a step-like manner in multiple stages. In the example shown in Fig. 3, the dead time Td is increased continuously. However, when it is increased continuously, it is not limited to a linear increase as shown in Fig. 3, but may be increased in a curved manner.

[0050] The longer the dead time Td, the longer the delay time, and the greater the error in the measured distance. However, if the dead time Td is increased continuously or in multiple steps, the dead time Td should be kept as short as possible, and the error in the measured distance can be minimized.

[0051] In this embodiment, the dead time Td may be instantaneously started at timing t6 and then maintained thereafter, as in another operation example shown in Fig. 9. In other words, this can be regarded as an on / off control of the dead time Td, which can facilitate the control.

[0052] <Other> In addition to the above-mentioned embodiment, various technical features disclosed in this specification can be modified in various ways without departing from the spirit of the technical creation. In other words, the above-mentioned embodiment should be considered to be illustrative and not restrictive in all respects, and the technical scope of the present invention should not be limited to the above-mentioned embodiment, but should be understood to include all modifications that fall within the meaning and scope equivalent to the scope of the claims.

[0053] For example, the multiplier 6 may be disposed between the receiving circuit 3 and the ADC 4. In this case, the multiplier 6 multiplies the received signal RS, which is an analog signal output from the receiving circuit 3, by the gain value G.

[0054] <Additional Notes> As described above, the signal processing device (101A) according to one embodiment of the present disclosure includes: A drive circuit (2) configured to drive the ultrasonic sensor element (1); a receiving circuit (3) configured to output a receiving signal (RS) based on an output (SS) of the ultrasonic sensor element; A reflected wave signal generating unit (5, 6) configured to generate a reflected wave signal (WS2) by performing detection processing based on the received signal; a comparator (9) configured to compare the reflected wave signal with a threshold value (TH) and output a comparison signal (CMP) as a comparison result; a masking unit (10) configured to change the level of a mask signal (MSK) when the level of the comparison signal is maintained for a predetermined dead time (Td) after the level change, and to maintain the level of the mask signal at the previous level when the level of the comparison signal is changed before the dead time has elapsed after the level change, and to output the mask signal; a dead time generating unit (13) configured to generate the dead time so that the dead time in a first period (T1) from the start of driving of the ultrasonic sensor element is shorter than the dead time in a second period (T2) after the first period; The first configuration includes the above.

[0055] This configuration can solve the problem of achieving both a shortened reverberation time and improved noise removal performance.

[0056] In addition, in the first configuration, a multiplier (6) is disposed between the sensor element and the comparator and configured to multiply an input by a gain value (G); a gain value control unit (7) configured to variably generate the gain value depending on time; a dead time generating unit (13) configured to variably generate the dead time in response to the gain value; It may further comprise the following (second configuration).

[0057] In addition, in the above first configuration, a configuration may be made which further includes a dead time generating unit (13) configured to start measuring time from the start of the drive and variably generate the dead time in accordance with the passage of time (third configuration).

[0058] In any one of the first to third configurations, the dead time generating unit may be configured to generate the dead time so as to continuously increase with respect to time in the second period (fourth configuration).

[0059] In addition, in any of the above first to third configurations, the dead time generating unit may be configured to generate the dead time in the second period so as to increase in a step-like manner in multiple stages with respect to time (fifth configuration).

[0060] In addition, in any of the first to third configurations, the dead time generation unit may generate the dead time so that it increases instantaneously at the start timing of the second period, and thereafter the dead time may be constant (sixth configuration).

[0061] In any one of the first to sixth configurations, the masking portion (10) is a successive coincidence counter (10A) configured to use a change in the level of the comparison signal as a trigger to initialize time and start counting the time, and to continue counting while the levels of the comparison signals are consistent; a count value comparator (10B) configured to compare a count value (CNT) output from the successive coincidence counter with the dead time; an output latch section (10C) which outputs a mask signal with a level of the comparison signal set to a level of the mask signal when an output (CP) of the count value comparator changes to a predetermined level; (seventh configuration).

[0062] Moreover, an ultrasonic sensor (101) according to an embodiment of the present disclosure includes the signal processing device (101A) in any one of the first to seventh configurations and the ultrasonic sensor element (1) (eighth configuration).

[0063] Moreover, a vehicle (200) according to an embodiment of the present disclosure includes the ultrasonic sensor (10X) in the eighth configuration (ninth configuration). [Industrial Applicability]

[0064] The present disclosure can be used in ultrasonic sensors, for example, for in-vehicle use. [Explanation of symbols]

[0065] 1 Sensor element 2. Drive circuit 3. Receiving circuit 4 ADC 5 Reflected wave signal generation section 6. Multiplier 7 Gain value control section 8 Threshold Generation Unit 9 Comparators 10 Masking section 10A consecutive coincidence counter 10B Count value comparator 10C Output latch section 11 Signal selection section 12 Communication terminal 13 Dead time generator 10X Ultrasonic Sensor 100,101,102 Ultrasonic Sensors 100A, 101A, 102A Signal processing device 200 vehicles 300 Objects

Claims

1. a drive circuit configured to drive the ultrasonic sensor element; a receiving circuit configured to output a receiving signal based on an output of the ultrasonic sensor element; a reflected wave signal generating unit configured to generate a reflected wave signal by performing a detection process based on the received signal; a comparator configured to compare the reflected wave signal with a threshold value and output a comparison signal as a comparison result; a masking unit configured to output the mask signal by changing the level of the mask signal when the level of the comparison signal is maintained for a predetermined dead time after the level change, and to maintain the level of the mask signal at the immediately preceding level when the level of the comparison signal is changed before the dead time has elapsed after the level change; a dead time generating unit configured to generate the dead time such that the dead time in a first period from the start of driving of the ultrasonic sensor element is shorter than the dead time in a second period after the first period; A signal processing device comprising:

2. a multiplier disposed between the sensor element and the comparator and configured to multiply an input by a gain value; a gain value control unit configured to variably generate the gain value depending on time; a dead time generating unit configured to variably generate the dead time in response to the gain value; The signal processing apparatus of claim 1 , further comprising:

3. The signal processing device according to claim 1 , further comprising a dead time generating unit configured to start measuring time from the start of the driving and to variably generate the dead time in accordance with the passage of time.

4. The signal processing device according to claim 1 , wherein the dead time generating section generates the dead time so as to continuously increase with respect to time in the second period.

5. The signal processing device according to claim 1 , wherein the dead time generating section generates the dead time in the second period so as to increase in a stepwise manner in a plurality of stages with respect to time.

6. The signal processing device according to claim 1 , wherein the dead time generating section generates the dead time so that the dead time increases instantaneously at a start timing of the second period, and the dead time is constant thereafter.

7. The masking portion is a successive coincidence counter configured to use a change in the level of the comparison signal as a trigger to initialize time and start counting time, and to continue counting while the levels of the comparison signals are consistent; a count value comparator configured to compare a count value output from the successive coincidence counter with the dead time; an output latch section which outputs the mask signal with the level of the comparison signal set to the level of the mask signal when the output of the count value comparator changes to a predetermined level; The signal processing device according to claim 1 , further comprising:

8. An ultrasonic sensor comprising: the signal processing device according to claim 1; and the ultrasonic sensor element.

9. A vehicle comprising the ultrasonic sensor according to claim 8.

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