JP2023091893A - Signal processing device, ultrasonic system and vehicle - Google Patents

Abstract

To provide an ultrasonic system that can identify self-waves with a simple configuration.SOLUTION: An ultrasonic system includes a wave transmission signal generation unit configured to generate a wave transmission signal for transmitting ultrasonic, a wave reception signal output unit (including, for example, an ADC 15) configured to output a wave reception signal based on reception of the ultrasonic, and a self-wave identification unit (168) configured to identify self-waves as reflection waves of the transmission waves that can be included in the reception waves. The wave transmission signal generation unit encodes the wave transmission signal by modulating a frequency of the wave transmission signal. The self-wave identification unit (168) includes filters (168A1, 168A2) having a plurality of pass bands shifted from each other, generates a plurality of envelops from a waveform of the wave reception signal passing each of the plurality of pass bands to identify the self-wave from each peak position of the plurality of envelops.SELECTED DRAWING: Figure 3

Description

The invention disclosed in this specification provides a signal processing apparatus for processing a transmission signal for transmitting ultrasonic waves and a reception signal based on reception of ultrasonic waves, and an ultrasonic wave including the signal processing apparatus. systems and vehicles equipped with such ultrasound systems.

2. Description of the Related Art Conventionally, an ultrasonic system is known that measures the distance to an obstacle by measuring the time TOF (Time Of Flight) from the time an ultrasonic wave is generated until the reflected wave from the obstacle returns. Such ultrasonic systems are often installed in vehicles, and one example is known as an in-vehicle clearance sonar.

WO2020/004609

In an ultrasonic system for identifying self-waves, self-waves are identified by capturing product-specific modulation schemes as characteristics of self-waves. An ultrasound system that distinguishes its own waves can distinguish between ultrasound waves transmitted from other ultrasound systems and reflected waves transmitted from its own ultrasound system and reflected by an object. False detection of distance can be reduced.

From the viewpoint of cost, an ultrasonic system capable of identifying self-waves with a simple configuration is desired.

The signal processing apparatus disclosed in this specification includes a transmission signal generation unit configured to generate a transmission signal for transmitting ultrasonic waves, and a reception signal based on reception of ultrasonic waves. and a self-wave identification unit configured to identify a self-wave that is a reflected wave of the transmitted wave that may be included in the received wave, wherein The transmitted wave signal generation unit encodes the transmitted wave signal by modulating the frequency of the transmitted wave signal, and the self wave identification unit includes a filter having a plurality of passbands that are shifted from each other. A plurality of envelopes are generated from the waveforms of the received wave signals that have respectively passed through the bands, and the self wave is identified from the peak positions of each of the plurality of envelopes.

An ultrasound system disclosed in the present specification includes a signal processing device configured as described above and an ultrasound transmitting/receiving device configured to be directly or indirectly connected to the signal processing device. is.

The vehicle disclosed in this specification is configured to include the ultrasonic system configured as described above.

According to the signal processing device, ultrasonic system, and vehicle disclosed in this specification, self waves can be easily identified.

FIG. 1 is a diagram schematically showing a vehicle equipped with an ultrasonic system according to an embodiment and an object. FIG. 2 is a diagram showing the configuration of the ultrasound system according to the embodiment. FIG. 3 is a diagram showing the configuration of a receiving circuit according to the embodiment. FIG. 4 is a diagram showing the distribution of frequencies. FIG. 5 is a diagram showing an envelope waveform generated during up-chirp. FIG. 6 is a diagram showing an envelope waveform generated during down-chirp. FIG. 7 is a diagram illustrating a configuration example of an envelope generation unit according to the embodiment;

An embodiment of the present invention will be described below with reference to the drawings. The ultrasonic system according to the embodiment described below is assumed to be mounted on a vehicle as an example, and measures the distance between the vehicle and an object to provide an alarm function, an automatic braking function, and an automatic It can be used for parking functions, etc.

FIG. 1 shows a vehicle 200 equipped with an ultrasound system 100 (hereinafter referred to as “ultrasound system 100”) according to an embodiment, and an object (obstacle) 300 . Ultrasonic waves transmitted from the ultrasonic system 100 are reflected by the object 300 and received by the ultrasonic system 100 as reflected waves. At this time, the ultrasound system 100 also receives environmental noise N. FIG. Environmental noise N includes, for example, ultrasound waves transmitted from ultrasound systems other than ultrasound system 100 .

Therefore, if the ultrasound system 100 does not correctly distinguish between the self wave, which is the reflected wave, and the environmental noise N, the ultrasound system 100 will erroneously detect the distance to the object 300 .

Next, the ultrasound system 100 will be described. FIG. 2 is a diagram showing the configuration of the ultrasound system 100. As shown in FIG.

The ultrasound system 100 includes a signal processing device 1 , a transformer Tr, and an ultrasound transmission/reception device 2 . The ultrasonic transmission/reception device 2 is externally connected to the signal processing device 1 via a transformer Tr. Note that the transformer Tr may not necessarily be provided.

The signal processing device 1 is a semiconductor integrated circuit device. The signal processing device 1 includes a DAC (Digital to Analog Converter) 11, a driver 12, an LNA (Low Noise Amplifier) 13, an LPF (Low Pass Filter) 14, an ADC (Analog to Digital Converter) 15, and a digital processing It includes a portion 16 and external terminals T1 to T5.

The DAC 11 D/A converts the transmission signal output from the transmission signal generation unit 164 included in the digital processing unit 16 from a digital signal to an analog signal, and outputs the signal after the D/A conversion to the driver 12 .

The output terminals of the differential pair of the driver 12 are connected to the primary side of the transformer Tr via external terminals T1 and T2. An ultrasonic transmission/reception device 2 is connected to the secondary side of the transformer Tr. A driver 12 drives the ultrasonic transmission/reception device 2 based on the output signal of the DAC 11 .

The ultrasonic transmission/reception device 2 has a piezoelectric element (not shown) and transmits and receives ultrasonic waves. That is, the ultrasonic transmission/reception device 2 functions both as a sound source and as a reception section.

The input terminals of the differential pair of LNA 13 are connected to the secondary side of transformer Tr via external terminals T3 and T4. The output signal of LNA 13 is supplied to ADC 15 via LPF 14 . ADC 15 A/D-converts the output signal of LNA 13 from an analog signal to a digital signal, and outputs the A/D-converted signal to reception demodulation control section 165 included in digital processing section 16 .

The LNA 13, the LPF 14, and the ADC 15 are an example of a received wave signal output unit configured to output a received wave signal based on received ultrasonic waves.

The digital processing unit 16 includes an interface 161, a pseudorandom number generator 162, a transmission modulation control unit 163, a transmission signal generation unit 164, a reception demodulation control unit 165, a self wave identification determination unit 166, and a TOF measurement unit. 167;

The interface 161 conforms to LIN (Local Interconnect Network) as an example, and communicates with an ECU (Electronic Control Unit) (not shown) mounted on the vehicle 200 (see FIG. 1) via an external terminal T5.

The interface 161 outputs the update trigger signal TG to the pseudorandom number generator 162 based on the transmission command sent from the ECU. The interface 161 may be configured to output the update trigger signal TG each time a transmission command is received, or may be configured to output the update trigger signal TG once when the transmission command is received N times (N is a natural number equal to or greater than 2). There may be.

Pseudorandom number generator 162 generates a pseudorandom number PRN and outputs the pseudorandom number PRN to transmission modulation control section 163 . Also, the pseudorandom number generator 162 updates the pseudorandom number PRN each time it receives the update trigger signal TG.

As the pseudorandom number generator 162, for example, an LFSR (Linear Feedback Shift Register) can be used. Since the LFSR has a simple configuration, the cost of the pseudorandom number generator 162 can be reduced by using the LFSR as the pseudorandom number generator 162 .

Since the LFSR performs the same operation if the initial value is the same, it is desirable that the initial value of the LFSR be different between the individual ultrasound systems 100 . Therefore, it is preferable to use part of the unique identification number (serial number) given to the signal processing device 1 as the initial value of the LFSR. Since it is assumed that the number of patterns in the numerical part of the unique identification number assigned to the signal processing device 1 is greater than the number of patterns in the value of the LFSR, the unique identification number assigned to the signal processing device 1 is used as the initial value of the LFSR. We are going to use a part of Since part of the unique identification number is used, the initial value of LFSR may not be completely different between individual ultrasound systems 100 . However, by using part of the unique identification number assigned to the signal processing device 1, it is possible to easily increase the dispersion of the initial values of the LFSR among the individual ultrasound systems 100 (individual signal processing devices 1). can.

An analog true random number generator may be used instead of the pseudorandom number generator 162 . However, in the ultrasound system 100, random numbers are not used for security, but are used to ensure the randomness of the modulation scheme. The generator causes the cost of the signal processing device 1 to increase. In other words, cost can be reduced by using a pseudo-random number generator instead of a true random number generator.

Transmission modulation control section 163 determines a modulation pattern based on pseudorandom numbers. Examples of the modulation target of the modulation pattern include the frequency of the transmission signal, the phase of the transmission signal, the amplitude of the transmission signal, the number of burst signals included in the transmission signal, and the number of burst signals included in the transmission signal. interval time and the like.

The modulation pattern determined by transmission modulation control section 163 is desirably configured by combining a plurality of modulation targets. As a result, even if the modulation range of each modulation target is narrow due to the performance of the signal processing device 1 or the like, it becomes easy to ensure the randomness of the modulation scheme.

The transmission signal generation unit 164 generates a transmission signal with a modulation pattern determined by the transmission modulation control unit 163, that is, a modulation pattern based on the pseudorandom number PRN. As a result, the randomness of the modulation scheme is ensured, and the possibility of matching the modulation scheme of the own ultrasound system with that of another ultrasound system can be reduced. identification accuracy is improved.

The reception demodulation control section 165 acquires the received wave signal output from the ADC 15 and information on the modulation pattern determined by the transmission modulation control section 163 . The reception demodulation control section 165 determines the contents of demodulation of the received wave signal based on the modulation pattern.

For example, when the modulation pattern includes frequency modulation, the reception demodulation control unit 165 uses correlation convolution processing between the transmission signal and the reception signal, FFT (Fast Fourier Transform) processing for the reception signal, and the like. to demodulate the frequency-modulated information contained in the received wave signal. For example, when the modulation pattern includes an interval time, the reception demodulation control unit 165 obtains the information on the interval time included in the received signal by using the time measurement process between adjacent peaks of the received wave signal. demodulate.

Own wave identification determination section 166 identifies the own wave based on information on the modulation pattern determined by transmission modulation control section 163 and information demodulated by reception demodulation control section 165 . More specifically, if the similarity between the modulation pattern information determined by the transmission modulation control unit 163 and the information demodulated by the reception demodulation control unit 165 is equal to or higher than a predetermined level, the self-wave identification determination unit 166 Detects the reflected wave (self wave) of the transmitted wave.

Note that the self-wave identification determination unit 166 may identify the self-wave by integrating a plurality of received wave signals. As a result, although randomness is given to the modulation method, the modulation method in the ultrasonic system 100 and the modulation method in the ultrasonic system other than the ultrasonic system 100 are unlucky in one transmission wave. Even if the modulation schemes match, the self-wave identification determining section 166 can correctly identify the self-wave as long as the modulation schemes do not match continuously. That is, the self-wave identification determining unit 166 integrates a plurality of received wave signals to identify the self-wave, thereby further improving the self-wave identification accuracy.

The TOF measurement unit 167 uses a counter 167A to measure the time (TOF) from when the ultrasonic wave is transmitted until when the reflected wave from the object 300 is received.

The TOF measurement unit 167 starts counting by the counter 167A at the timing when the transmission command is sent from the ECU to the signal processing device 1 .

The TOF measurement unit 167 holds the count value of the counter 167A at the timing when the self wave is detected by the self wave identification determination unit 166 . The count value held by the TOF measurement unit 167 corresponds to the TOF, and the distance to the object can be specified by the TOF and the velocity of the ultrasonic waves transmitted from the ultrasonic transmitter/receiver. The count value held by the TOF measuring section 167 is sent to the ECU via the interface 161 .

FIG. 3 is a diagram showing the configuration of a receiving circuit. The receiving circuit RC has an ADC 15 and a self-wave identification section 168 . The self wave identification section 168 has an envelope generation section 168A, a peak position comparison section 168B, and a chirp detection section 168C. Note that the self-wave identification unit 168 can be understood as an example of a functional unit including the reception demodulation control unit 165 and the self-wave identification determination unit 166 described above.

The ADC 15 converts the input received wave from an analog signal to a digital signal. A digital signal converted by the ADC 15 is output to the envelope generator 168A.

Envelope generator 168A includes a filter having a plurality of passbands that are shifted from each other. To be more specific with reference to this figure, the envelope generator 168A includes a low band BPF (band pass filter) 168A1 and a high band BPF 168A2. The first passband set in low-band BPF 168A1 and the second passband set in high-band BPF 168A2 each have a lower cutoff frequency and an upper cutoff frequency, and their center frequencies are different.

FIG. 4 is a diagram showing the frequency distribution (in particular, the correlation between the frequency chirp range of the transmitted signal and the first passband and the second passband). The first passband set in the low-band BPF 168A1 has a center frequency LBPCF in a frequency band lower than the chirp median value FCCV of the frequency of the transmitted wave signal. Also, the second passband set in the high-band BPF 168A2 has a center frequency HBPCF in a frequency band higher than the chirp median value FCCV of the frequency of the transmission signal. More specifically, the center frequency LBPCF of the first passband is set closer to the chirp lower limit FCLLV of the frequency of the transmission signal, and the center frequency HBPCF of the second passband is set closer to the chirp upper limit of the frequency of the transmission signal. It is set closer to the value FCHLV.

The envelope generator 168A generates respective envelopes from the waveform of the received wave signal that has passed through the first passband and the waveform of the received wave signal that has passed through the second passband, and then detects the respective peak positions. Further includes detectors 168A3 and 168A4. The peak positions of the envelopes generated by the peak detectors 168A3 and 168A4 are output to the peak position comparator 168B.

The peak position comparison section 168B compares the peak positions of the multiple envelopes generated by the envelope generation section 168A. A result of comparing the peak positions of a plurality of envelopes is output to the chirp detector 168C.

The chirp detector 168C detects the appearance of the peak position of the envelope generated from the waveform of the received signal that has passed through the first passband and the peak position of the envelope generated from the waveform of the received signal that has passed through the second passband. Frequency modulation is detected from the order of

FIG. 5 is a diagram showing an envelope waveform generated during up-chirp. During the up-chirp, the frequency of the transmission signal is modulated by increasing the frequency of the transmission signal with the lapse of time in the transmission signal generator 164 (for example, 49 kHz→53 kHz). Generally, the frequency and step width are parameters that are adjusted according to the sensor characteristics. Thus, by way of example, the step width may be 100 Hz.

The chirp detector 168C detects that peaks appear in order from the envelope generated from the waveform of the received wave signal that has passed through the first passband among the plurality of envelopes. In line with this figure, the solid line L11 is the envelope waveform generated from the received wave signal that has passed through the first passband (for example, the center frequency of 50 kHz) of the low-band BPF 168A1, and its peak position is at time t11. ing. On the other hand, the dashed line L12 is the envelope waveform generated from the received wave signal that has passed through the second passband (for example, the center frequency of 52 kHz) of the high-band BPF 168A2, and its peak position is at time t12 after time t11. there is

FIG. 6 is a diagram showing an envelope waveform generated during down-chirp. During the down-chirp, the transmission signal generator 164 lowers the frequency of the transmission signal over time to modulate the frequency (for example, 53 kHz→49 kHz). As mentioned above, the frequency and step width are generally parameters to be adjusted according to the sensor characteristics. Thus, by way of example, the step width may be 100 Hz.

The chirp detector 168C detects that peaks appear in order from the envelope generated from the waveform of the received wave signal that has passed through the second passband among the plurality of envelopes. In line with this figure, the solid line L21 is the envelope waveform generated from the received wave signal that has passed through the first passband (for example, the center frequency of 50 kHz) of the low-band BPF 168A1, and its peak position is at time t22. ing. On the other hand, the dashed line L22 is an envelope waveform generated from the received wave signal that has passed through the second passband (for example, the center frequency of 52 kHz) of the high-band BPF 168A2, and its peak position is at time t21 before time t22. there is

The frequency modulation (whether it is an up-chirp or a down-chirp) can be easily detected simply by checking the order in which the peak positions of the multiple envelopes generated in this way appear.

FIG. 7 is a diagram showing a configuration example of the envelope generator 168A according to the embodiment. The envelope generator 168A has a bandpass filter 22 and a peak detection circuit 23. FIG.

The bandpass filter 22 has a signal switching section 22A and a filter operation circuit 22B.

The bandpass filter 22 is configured to switch between multiple passbands in a time division manner based on the signal output from the timing generator 21 .

More specifically, based on the signal output from the timing generation unit 21, the signal switching unit 22A time-divisionally converts the filter coefficient of the filter operation circuit 22B, the multiplier input, and the adder input for each of a plurality of passbands. switch.

The filter operation circuit 22B is configured by combining a multiplier 22B1 and an adder 22B2, and performs time-division filter operation processing so as to function as the low-band BPF 168A1 and the high-band BPF 168A2, for example.

In accordance with this figure, the filter operation circuit 22B operates in the first phase based on the filter coefficients switched in a time division manner by the signal switching unit 22A, the multiplier input, and the adder input. In the second phase, only the second passband is passed.

That is, the first phase corresponds to, for example, the period during which the filter operation circuit 22B (and the bandpass filter 22) functions as the low-band BPF 168A1. Also, the second phase corresponds to, for example, a period during which the filter operation circuit 22B functions as the high-band BPF 168A2.

Note that the first phase and the second phase are alternately switched based on the signal output from the timing generator 21 .

In addition, as shown in the figure, the filter operation circuit 22B includes a low-band storage element 22B3 for storing the operation results obtained in the first phase and a high-band storage element 22B3 for storing the operation results obtained in the second phase. 22B4 may be included.

Thus, by switching the filter coefficient, multiplier input, and adder input in a time division manner, a single filter operation circuit 22B can be shared by a plurality of passbands.

By sharing the filter operation circuit 22B for a plurality of passbands, it is not necessary to arrange the filter operation circuit 22B for each passband. By using such a configuration, the circuit scale can be reduced, and the cost can be reduced.

<Summary>
In the following, the various embodiments described so far will be described in general terms.

For example, the signal processing apparatus disclosed in this specification includes a transmission signal generation unit configured to generate a transmission signal for transmission of ultrasonic waves; a received wave signal output unit configured to output a wave signal; and a self wave identification unit configured to identify a self wave that is a reflected wave of the transmitted wave that may be included in the received wave. the transmission signal generator encoding the transmission signal by modulating the frequency of the transmission signal; A plurality of envelopes are generated from the waveforms of the received signals that have respectively passed through the passbands of , and the self wave is identified from the peak positions of each of the plurality of envelopes (first configuration).

In the signal processing device according to the first configuration, the plurality of passbands each have a lower cutoff frequency and an upper cutoff frequency, and have different center frequencies (second configuration). configuration).

Further, in the signal processing device according to the second configuration, the first passband of the filter has a center frequency in a lower frequency band than the chirp median value of the frequency of the transmission signal, and the second passband of the filter may be configured to have a center frequency in a higher frequency band than the chirp median value of the frequency of the transmission signal (third configuration).

Further, in the signal processing device according to the third configuration, the center frequency of the first passband is set close to the chirp lower limit of the frequency of the transmission signal, and the center frequency of the second passband is set to the A configuration (fourth configuration) may be employed in which the chirp upper limit value of the frequency of the transmission signal is set.

Further, in the signal processing device according to any one of the first to fourth configurations, the transmission signal generation unit modulates the frequency of the transmission signal by increasing the frequency of the transmission signal with the lapse of time. The identification unit identifies the self-wave by detecting the appearance of peaks in order from the envelope generated from the waveform of the received wave signal that has passed through the lower passband among the plurality of envelopes. A configuration (fifth configuration) may be used.

Further, in the signal processing device according to any one of the first to fourth configurations, the transmission signal generation unit modulates the frequency of the transmission signal by decreasing the frequency of the transmission signal with the lapse of time. The identification unit identifies the self-wave by detecting peaks appearing in order from the envelope generated from the waveform of the received wave signal that has passed a higher passband among the plurality of envelopes. A configuration (sixth configuration) may be used.

Further, in the signal processing device having any one of the first to sixth configurations, the filter may be configured to switch the plurality of passbands in a time division manner (seventh configuration).

Further, for example, the ultrasound system disclosed in this specification includes a signal processing device having any one of the first to seventh configurations, and a signal processing device that is directly or indirectly connected to the signal processing device. and an ultrasonic wave transmitting/receiving device configured (ninth configuration).

Further, for example, the vehicle disclosed in this specification is configured to include the ultrasonic system according to the eighth configuration (tenth configuration).

<Other Modifications>
The configuration of the present invention can be modified in various ways without departing from the gist of the invention, in addition to the above embodiments. The above embodiments should be considered illustrative in all respects and not restrictive, and the technical scope of the present invention is indicated by the scope of claims rather than the description of the above embodiments. It should be understood that all changes that fall within the meaning and range of equivalents of the claims are included.

1 signal processing device 2 ultrasonic transmission/reception device 11 DAC
12 driver 13 LNA
14LPF
15 ADCs
16 Digital Processing Unit 21 Timing Generation Unit 22 Bandpass Filter 22A Signal Switching Unit 22B Filter Operation Circuit 22B1 Multiplier 22B2 Adder 22B3 Low Band Storage Element 22B4 High Band Storage Element 23 Peak Detection Circuit 161 Interface 162 Pseudorandom Number Generator 163 Transmission modulation control unit 164 Transmission wave signal generation unit 165 Reception demodulation control unit 166 Self-wave identification determination unit 167 TOF measurement unit 167A Counter 168 Self-wave identification unit 168A Envelope generation unit 168A1 Low-band BPF
168A2 high band BPF
168A3, 168A4 peak detector 168B peak position comparator 168C chirp detector 100 ultrasonic system according to embodiment 200 vehicle 300 object (obstacle)
RC Receiving circuit T1 to T5 External terminal Tr Transformer

Claims (9)

a transmission signal generator configured to generate a transmission signal for transmitting ultrasound waves;
a received wave signal output unit configured to output a received wave signal based on received ultrasonic waves;
a self-wave identifying unit configured to identify a self-wave that is a reflected wave of the transmitted wave that can be included in the received wave;
with
The transmission signal generator encodes the transmission signal by modulating the frequency of the transmission signal,
The self-wave identification unit includes a filter having a plurality of passbands that are shifted from each other, generates a plurality of envelopes from waveforms of the received wave signals that have passed through the plurality of passbands, and generates a plurality of envelopes from the respective peaks of the plurality of envelopes. A signal processing device that identifies the self-wave from position. 2. The signal processing apparatus according to claim 1, wherein said plurality of passbands each have a lower cutoff frequency and an upper cutoff frequency, and are configured to have different center frequencies. A first passband of the filter has a center frequency in a frequency band lower than the median chirp of the frequency of the transmit signal, and a second passband of the filter has a center frequency of the median of the chirp of the frequency of the transmit signal. 3. A signal processing apparatus according to claim 2, wherein also has a center frequency in the high frequency band. The center frequency of the first passband is set close to the chirp lower limit of the frequency of the transmission signal, and the center frequency of the second passband is set close to the chirp upper limit of the frequency of the transmission signal. 4. The signal processing apparatus according to claim 3, set to . The transmission signal generation unit modulates the frequency by increasing the frequency of the transmission signal over time,
The self-wave identification unit identifies the self-wave by detecting peaks appearing in order from the envelope generated from the waveform of the received wave signal that has passed through a lower passband among the plurality of envelopes. A signal processing device according to any one of claims 1 to 4, configured to: The transmission signal generator modulates the frequency by lowering the frequency of the transmission signal over time,
The self-wave identification unit identifies the self-wave by detecting peaks appearing in order from the envelope generated from the waveform of the received wave signal that has passed through a higher passband among the plurality of envelopes. A signal processing device according to any one of claims 1 to 4, configured to: 7. The signal processing device according to claim 1, wherein said filter is configured to switch said plurality of passbands in a time division manner. A signal processing device according to any one of claims 1 to 7;
an ultrasound transceiver configured to be directly or indirectly connected to the signal processor. A vehicle comprising the ultrasound system of claim 8 .

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