Method and device for detecting objects

Abstract

Device (1) configured to detect an object (B) around the device (1), the device (1) comprising: a drive signal generator (3) configured to generate a drive signal for driving a transmitter unit (20A) so that a transmitter device of the transmitter unit (20A) transmits a transmitter wave to the outside; and a detection unit (42) configured to: Receiving an echo resulting from the reflection of the transmitter wave by the object (B) via a receiver device (21); and Obtaining a received signal based on the received echo, thereby detecting the object (B) based on the received signal, where: the drive signal generator (3) is configured to selectively output one of the first drive signal (SD1) and the second drive signal (SD2) as the drive signal; the first drive signal (SD1) has a first temporal frequency change within a first frequency band (Bt1) defined inclusively from a first lowest frequency (Fti1) to a first highest frequency (Ftx1); the first frequency band (Bt1) has a first intermediate frequency (Ftc1) which is defined as one of the frequencies, center frequency and average frequency, of the first frequency band (Bt1); the second drive signal (SD2) has a second temporal frequency change within a second frequency band (Bt2) defined inclusively from a second lowest frequency (Fti2) to a second highest frequency (Ftx2); the second frequency band (Bt2) has a second intermediate frequency (Ftc2) which is defined as one of the frequencies, center frequency and average frequency, of the second frequency band (Bt2); the second intermediate frequency (Ftc2) is different from the first intermediate frequency (Ftc1); the second frequency band (Bt2) is partially superimposed on the first frequency band (Bt1); the received signal of the echo resulting from a reflection of the transmitter wave based on the first drive signal (SD1) is referred to as a first received signal (SR1); the received signal of the echo resulting from a reflection of the transmitter wave based on the second drive signal (SD2) is referred to as a second received signal (SR2), wherein a frequency increasing direction of the second drive signal (SD2) is opposite to a frequency increasing direction of the first drive signal (SD1); and the device (1) is configured, when acquiring two of the first received signals (SR1) consecutively, to reduce erroneous identification of an unintended frequency pattern signal (SRF) as the second received signal (SR2) according to a characteristic according to which the second received signal (SR2) is shifted to be higher than the unintended frequency pattern signal (SRF).

Description

Technical field

[0001] The present invention relates to methods and devices for detecting surrounding objects. State of the art

[0002] Object detection devices include a type of object detection device that uses an ultrasonic sensor. Such a type of object detection device may be installed in a vehicle to detect objects around the vehicle. Such an object detection device installed in a vehicle may have lower accuracy in detecting objects, for example, due to interference.

[0003] For example, interference may be generated when such an ultrasonic sensor installed in one's own vehicle receives an ultrasonic wave transmitted by another ultrasonic sensor installed in another vehicle located around the one's own vehicle. As another example, interference may be generated when one of the ultrasonic sensors installed in one's own vehicle receives an ultrasonic wave transmitted by another of the ultrasonic sensors.

[0004] DE 101 06 142 A1 discloses an ultrasonic multi-sensor arrangement. The ultrasonic multi-sensor arrangement disclosed in DE 101 06 142 A1 comprises a plurality of transmitter units, each including at least a first and a second transmitter unit and at least one receiver unit. The selected first and second transmitter units in the plurality of transmitter units can be configured to operate in parallel to transmit a coded ultrasonic pulse burst.

[0005] The coding of the ultrasonic pulse burst to be transmitted by the respective first and second transmitter units disclosed in DE 101 06 142 A1 enables the first and second transmitter units to operate in parallel, i.e. simultaneously, with each other.

[0006] In particular, a carrier signal used to encode the ultrasonic pulse burst of each of the simultaneously operating first and second transmitter units is individually frequency-modulated. The frequency, i.e., the drive frequency, of the carrier signal used for the first transmitter unit increases linearly during the duration of the ultrasonic pulse burst from the first transmitter unit. In contrast, the frequency, i.e., the drive frequency, of the carrier signal used for the second transmitter unit decreases linearly during the duration of the ultrasonic pulse burst from the second transmitter unit.

[0007] US 2010 / 0 245 154 A1 discloses an object distance measuring system in which alternating up and down frequency sweeps are transmitted, which have randomly distributed slopes due to a random selection of local frequency peaks and valleys according to predetermined probability tables, and the beat frequency, which is obtained by combining the transmitted signal with its reflection from an object, is determined.

[0008] US 2017 / 0 023 670 A1 discloses a radar system comprising: a transmitter controller configured to control an oscillator such that the oscillator provides a transmit radar signal, the transmit radar signal comprising: a transmit first ramp frequency portion during which the frequency of the transmit radar signal either increases or decreases over time; a transmit first return frequency portion during which the frequency of the transmit radar signal changes in an opposite manner to the transmit first ramp frequency portion; and a transmit second ramp frequency portion during which the frequency of the transmit radar signal changes in the same manner as the transmit first ramp frequency portion; and a receiver controller configured to receive a received radar signal representing a reflected version of the transmitted radar signal.

[0009] US 2016 / 0 061 942 A1 discloses a radar device for estimating the distance of an obstacle. The radar device includes a local oscillator that generates a first ramp segment and a second ramp segment. The first ramp segment and the second ramp segment each include a starting frequency, a first frequency, and a second frequency. The first frequency of the second ramp segment is equal to or greater than the second frequency of the first ramp segment when a slope of the first ramp segment and a slope of the second ramp segment are equal and positive. The first frequency of the second ramp segment is equal to or less than the second frequency of the first ramp segment when the slope of the first ramp segment and the slope of the second ramp segment are equal and negative.

[0010] DE 10 2008 044 366 A1 discloses a detection device for detecting the surroundings of a vehicle. The detection device has at least one ultrasonic transducer and a transmission pulse modulator connected to the at least one ultrasonic transducer. The detection device also has a receiver connected to the at least one ultrasonic transducer. The transmission pulse modulator is designed to generate a pulse-modulated transmission signal and to transmit it to the ultrasonic transducer for sound conversion. The receiver is designed to receive a response signal generated by the ultrasonic transducer and representing an ultrasonic echo and, depending on the response signal, to determine a distance or a time derivative of the distance of the ultrasonic transducer from an object and to generate an output signal representing the distance.The pulse-modulated transmission signal has temporally successive transmission pulses with a transmission pulse duration, wherein at least one transmission pulse of the transmission pulses has a temporal transmission pulse section with an increasing and / or decreasing carrier frequency and a temporal transmission pulse section with a constant carrier frequency, so that the carrier frequency is modulated by the transmission pulses.

[0011] The use of the technology disclosed in DE 101 06 142 A1 enables an ultrasonic sensor installed in a vehicle to identify whether a received ultrasonic echo results from an ultrasonic wave transmitted by the ultrasonic sensor itself.

[0012] In particular, the transceiver unit or transmitter / receiver unit of the ultrasonic sensor determines whether a received ultrasonic echo contains the frequency modulation that matches the frequency modulation of the ultrasonic wave transmitted by the transceiver unit of the ultrasonic sensor itself, and thus identifies whether the received ultrasonic echo results from the ultrasonic wave signal transmitted by the ultrasonic sensor itself.

[0013] The transmitter unit of such an ultrasonic sensor typically uses a transducer that serves as an oscillator for generating an ultrasonic wave; the transducer has a predetermined resonant frequency. If the drive frequency of the carrier signal for the transmitter unit is distant from the resonant frequency, the tracking ability of the transmitter unit with respect to the drive frequency may be impaired. For this reason, a simple linear increase or decrease in the drive frequency of the transmitter unit, as disclosed in DE 101 06 142 A1, may lead to insufficient identification accuracy of the received ultrasonic waves.

[0014] The present invention is based on the circumstances described above by way of example. The object of the invention is therefore to provide a device and a method for detecting an object, each of which achieves higher identification accuracy. This object is achieved by a device having the features of claim 1 and by a method having the features of claim 9. The dependent claims are directed to advantageous developments of the invention.

[0015] The drive signal generator of each of the apparatus and the method according to the present invention is configured to output the drive signal to drive the transmitter unit so that the transmitter device of the transmitter unit transmits the transmitter wave outward. When an echo resulting from the reflection of the transmitter wave by the object is received via the receiver device, the detection unit obtains the received signal based on the received echo, thereby detecting the object based on the received signal.

[0016] The method selectively uses one of the first drive signal and the second drive signal as the drive signal. The drive signal generator of the device is configured to selectively output one of the first drive signal and the second drive signal as the drive signal.

[0017] The first drive signal has the first temporal frequency change within the first frequency band, which is defined inclusively from the first lowest frequency to the first highest frequency. The first frequency band has the first intermediate frequency, which is defined as one of the center frequency and the average frequency of the first frequency band.

[0018] The second drive signal has the second temporal frequency change within the second frequency band, which is defined inclusively from the second lowest frequency to the second highest frequency. The second frequency band has the second intermediate frequency, which is defined as one of the center frequency and the average frequency of the second frequency band. The second intermediate frequency is different from the first intermediate frequency. The second frequency band is partially superimposed on the first frequency band.

[0019] The received signal based on the echo resulting from the transmitter wave generated based on the first drive signal is referred to as a first received signal. Similarly, the received signal based on the echo resulting from the transmitter wave generated based on the second drive signal is referred to as a second received signal.

[0020] The device and the method lead to a better accuracy of the individual identification of the first and the second received signal.

[0021] In some paragraphs of the specification, claims, and abstract, reference numerals or numbers enclosed in parentheses are assigned to the respective elements. Each reference numeral or number enclosed in parentheses of an element represents only one example of a correspondence relationship between the element and specific means described in the embodiment described later, and therefore, the reference numerals enclosed in parentheses do not limit the technical scope of the present invention. Brief description of the drawings Fig. 1 is a block diagram illustrating a schematic configuration of an object detection device according to an embodiment. Fig. 2 is a diagram including timing diagrams each representing a frequency characteristic of a respective first and second drive signal generated by a Fig. 1 shown control signal generator. Fig. 3 is a diagram comprising a first pair of graphs and a second pair of graphs; the first pair of graphs represents characteristics of a first received signal corresponding to the Fig. 2, and the second pair of graphs represents characteristics of a second received signal corresponding to the first drive signal shown in Fig. 2 corresponds to the second control signal shown. Fig. Figure 4 is a graph showing how two first received signals corresponding to the first drive signal change over time. Fig. 5 is a diagram including timing charts each illustrating a frequency characteristic of a corresponding one of the first and second drive signals according to a first comparative example. Fig. 6 is a diagram comprising a first pair of graphs and a second pair of graphs; the first pair of graphs represents characteristics of a first received signal corresponding to the Fig. 5, and the second pair of graphs represents characteristics of a second received signal corresponding to the first drive signal shown in Fig. 5 corresponds to the second control signal shown. Fig. 7 is a diagram including timing charts each illustrating a frequency characteristic of a corresponding one of the first and second drive signals according to a second comparative example. Fig. 8 is a diagram comprising a first pair of graphs and a second pair of graphs; the first pair of graphs represents characteristics of a first received signal corresponding to the Fig. 7, and the second pair of graphs represents characteristics of a second received signal corresponding to the first drive signal shown in Fig. 7 corresponds to the second control signal shown. Fig. 9 is a graph illustrating how two first received signals corresponding to the first drive signal change over time according to the second comparative example. Fig. Fig. 10 is a diagram according to a first partial modification, including timing charts each representing a frequency characteristic of a corresponding one of the first and second drive signals output from a Fig. 1 shown control signal generator. Fig. Fig. 11 is a diagram according to a second partial modification, including timing charts each representing a frequency characteristic of a corresponding one of the first and second drive signals output from a Fig. 1 shown control signal generator. Detailed description of the embodiment

[0022] An embodiment of the present invention will now be described with reference to the accompanying drawings. If various modifications applicable to the embodiment were inserted into the middle of the descriptions of the embodiment, this insertion would make the understanding of the embodiment difficult. For this reason, various modifications of the embodiment will be described collectively at the end of the descriptions of the embodiment.

[0023] In relation to Fig. 1, an object detection device 1 is installed in a vehicle (not shown) and configured to detect an object B located around the vehicle. The vehicle in which the object detection device 1 of the embodiment is installed is referred to as a self-vehicle.

[0024] The object detection device 1 of the first embodiment is configured as an ultrasonic sensor. Specifically, the object detection device 1 is configured to transmit a transmitter wave, i.e., an ultrasonic wave burst, toward the exterior of the own vehicle. Furthermore, the object detection device 1 is configured to receive a reflected wave, i.e., a received echo resulting from the reflection of the transmitter wave by the object B, to accordingly obtain a distance to the external object B from the own vehicle.

[0025] In particular, the object detection device 1 includes a transceiver or transmitter / receiver device 2, a drive signal generator 3 and a controller 4. The object detection device 1 has a single sensor housing, and the transceiver 2, the drive signal generator 3 and the controller 4 are carried by the sensor housing.

[0026] The transceiver 2 of the object detection device 1 of the first embodiment is designed as a single device configured to perform a transmission function and a reception function. Specifically, the single transceiver 2 consists of a single transducer 21, a transmitter unit 20A, and a receiver unit 20B. The transmitter unit 20A and the receiver unit 20B share the transducer 21 to perform the transmission function and the reception function.

[0027] Specifically, the transceiver 2 includes the transducer 21, a transmitter circuit 22, and a receiver circuit 23. The transmitter unit 20A includes the transducer 21 and the transmitter circuit 22, and the receiver unit 20B includes the transducer 21 and the receiver circuit 23.

[0028] The transducer 21 is electrically connected to the transmitter circuit 22 and the receiver circuit 23. The transducer 21 serves as a transmitter device that transmits the transmitter wave to the outside and also serves as a receiver device that receives an echo.

[0029] Specifically, the transducer 21 is configured as an ultrasonic microphone with an electromechanical conversion device, such as a piezoelectric device. The transducer 21 is installed in the vehicle so as to be arranged to face the exterior surface of the vehicle; this arrangement of the transducer 21 enables the transmission of the transmitter wave to the exterior of the vehicle and the reception of an echo, i.e., a reflected wave, from the exterior thereof.

[0030] The transmitter circuit 22 is configured to drive the transducer 21 in response to an input drive signal, thereby transmitting transmitter waves, i.e., a transmitter wave burst, at a frequency within a predetermined ultrasonic frequency band. Specifically, the transmitter circuit 22 includes, for example, a digital-to-analog (D / A) converter and is configured to perform D / A conversion of the input drive signal having a digital format into an alternating current (AC) voltage signal as a drive signal having an analog format, using the D / A converter, and apply the AC voltage signal to the transducer 21.

[0031] The receiver circuit 23 is configured to generate a received signal based on a result of reception of an echo by the transducer 21 and output the received signal to the controller 4. Specifically, the receiver circuit 23 includes, for example, an amplifier and an A / D converter. The receiver circuit 23 is configured to perform a predetermined signal processing task, including amplification and A / D conversion of an input AC voltage signal from the transducer 21, by using the amplifier and the A / D converter, to thereby generate a received signal based on the amplitudes of the echo received by the transducer 21. Then, the receiver circuit 23 is configured to output the generated received signal to the controller 4.

[0032] As previously described, the transceiver 2 is configured so that the transducer 21 serves as a transceiver unit that (1) the transmitter wave sends (2) receives the echo resulting from the reflection of the transmitter wave transmitted from the transceiver 21 itself by an object B, to thereby generate a received signal containing information regarding the distance to the object B from the own vehicle.

[0033] An echo resulting from the reflection of the transmitter wave transmitted by the transducer 21 and received by the transducer 21 itself is called a regular echo. On the other hand, an echo resulting from the reflection of the transmitter wave transmitted by another device, i.e., another transducer, and received by the transducer 21 is called an irregular echo.

[0034] The drive signal generator 3 is configured to generate the drive signal for driving the transmitter unit 20A. The drive signal is, for example, a pulsed signal whose frequency is within the predetermined ultrasonic band and causes the transmitter unit 20A to transmit the transmitter wave.

[0035] Specifically, the drive signal generator 3 of the embodiment is configured to selectively generate one of the first drive signal SD1 and the second drive signal SD2 as the drive signal, and selectively output one of the first drive signal SD1 and the second drive signal SD2. Each of the first and second drive signals SD1 and SD2 is frequency-modulated, and the frequency modulation of the first drive signal SD1 is different from that of the second drive signal SD2. Specific examples of how each of the first and second drive signals SD1 and SD2 is frequency-modulated will be described later.

[0036] The control device 4 is configured to control how the drive signal generator 3 outputs one of the signals, first drive signal SD1 and second drive signal SD2, and to perform a task of processing the received signal output from the receiver unit 20B.

[0037] In particular, the control device 4 has a transmission control unit 41 and a detection unit 42.

[0038] The transmission control unit 41 is configured to output a control signal to the drive signal generator 3 to thereby control how the transmitter unit 20A outputs transmitter waves.

[0039] Specifically, the transmission control unit 41 is configured to control the frequency and output timing of the first drive signal SD1 or the second drive signal SD2 generated by the drive signal generator 3. The frequency of the drive signal, that is, the frequency of each of the first and second drive signals SD1 and SD2, is also referred to as a drive frequency. The transmission control unit 41 is configured to control the drive signal generator 3 to selectively output one of the first drive signal SD1 and the second drive signal SD2.

[0040] The detection unit 42 is configured to detect the object B based on the received signal output from the receiver circuit 23.

[0041] Specifically, the detection unit 42 controls operations of the receiver circuit 23 and receives the received signal output from the receiver circuit 23, thereby detecting the presence of the object B and detecting the distance of the object B from the transducer 21.

[0042] The detection unit 42 includes a Doppler shift (DS) detector 43. The Doppler shift detector 43 is configured to detect a Doppler shift of the echo received by the transducer 21 relative to the corresponding transmitter wave. In particular, the detection unit 42 is configured to correct the received signal according to the Doppler shift detected by the Doppler shift detector 43. The detection unit 42 is also configured to calculate the degree of agreement between the corrected received signal and a predetermined reference signal and to determine whether the corrected received signal is based on a regular echo.

[0043] In the following, schematic operations of the previously configured object detection device 1 will be described together with advantages provided by the previously configured object detection device 1 with respect to Fig. 2 to 9 can be obtained. Fig. 2 shows a specific example of each of the first drive signal SD1 and the second drive signal SD2.

[0044] As shown in FIG. 1, the transmission control unit 41 of the embodiment outputs the control signal to the drive signal generator 3, so that the drive signal generator 3 generates the drive signal based on the control signal and outputs the drive signal to the transmitter unit 20A. The drive signal drives the transmitter unit 20A, so that the transmitter circuit 22 excites the transducer 21 based on the input drive signal to cause the transducer 21 to serve as the transmitter device that transmits a transmission wave to the outside of the object detection device 1, that is, to the outside of the own vehicle.

[0045] The control signal includes a signal, i.e., information, that enables the drive signal generator 3 to output a selected one of the first drive signal SD1 and the second drive signal SD2. Specifically, the transmission control unit 41 instructs the drive signal generator 3 to output one of the first drive signal SD1 and the second drive signal SD2. In response to receiving the control signal indicative of the first drive signal SD1, the drive signal generator 3 generates the first drive signal SD1 and outputs the first drive signal SD1 to the transmitter unit 20A. In contrast, in response to receiving the control signal indicative of the second drive signal SD2, the drive signal generator 3 generates the second drive signal SD2 and outputs the second drive signal SD2 to the transmitter unit 20A.

[0046] In relation to Fig. 2, the first control signal SD1 and the second control signal SD2 have respective frequency modulations that differ from each other. Fig. The graph shown in Figure 2 has a horizontal axis T representing time and a vertical axis F representing the drive frequency. Reference symbol Tts represents a transmission start time, which is the start time of transmission of the drive signal. Reference symbol Tte represents a transmission completion time, which is the completion time of the completion of transmission of the drive signal. Reference symbol Fk represents a predetermined resonance frequency of the transmitter unit 20A. As a typical example, the resonance frequency Fk is substantially equal to a predetermined resonance frequency of the transducer 21.

[0047] The first drive signal SD1 is configured such that the frequency of the first drive signal SD1 changes over time within a first frequency band Bt1, which is defined inclusively from a first lowest frequency Fti1 to a first highest frequency Ftx1. The first lowest frequency Fti1 represents the lower limit of the first frequency band Bt1, and the first highest frequency Ftx1 represents the upper limit of the first frequency band Bt1. The first frequency band Bt1 of the exemplary embodiment is configured to include the resonance frequency Fk. Reference symbol Ftc1 represents an intermediate frequency, which is the center frequency of the first frequency band Bt1.

[0048] The first drive signal SD1 is configured to include a predetermined frequency change; the predetermined frequency change represents that the frequency of the first drive signal SD1 increases toward the first highest frequency Ftx1. That is, the first drive signal SD1 is a so-called up-chirp signal. In particular, the first drive signal SD1 is configured such that the frequency of the first drive signal SD1 increases from the first lowest frequency Fti1 to the first highest frequency Ftx1.

[0049] The first drive signal SD1 of the embodiment is configured such that the frequency of the first drive signal SD1 increases linearly from the first lowest frequency Fti1 at the transmission start time Tts to the first highest frequency Ftx1 at the transmission end time Tte. The up-chirp of the first drive signal SD1 is configured such that the intermediate frequency Ftc1 of the first frequency band Bt1 coincides with an average frequency of the first frequency band Bt1.

[0050] The second drive signal SD2 is configured such that the frequency of the second drive signal SD2 changes over time within a second frequency band Bt2, which is defined inclusively from a second lowest frequency Fti2 to a second highest frequency Ftx2. The second lowest frequency Fti2 represents the lower limit of the second frequency band Bt2, and the second highest frequency Ftx2 represents the upper limit of the second frequency band Bt2. The second frequency band Bt2 of the exemplary embodiment is configured to include the resonance frequency Fk. Reference symbol Ftc2 represents an intermediate frequency, which is the center frequency of the second frequency band Bt2.

[0051] The second drive signal SD2 is configured to include a predetermined frequency change; the predetermined frequency change represents the frequency of the second drive signal SD2 decreasing toward the second lowest frequency Ftx2. This means that the second drive signal SD2 is a so-called downward chirp signal. Specifically, the second drive signal SD2 is configured such that the frequency of the second drive signal SD2 decreases from the second highest frequency Ftx2 to the second lowest frequency Fti2.

[0052] The second drive signal SD2 of the embodiment is configured such that the frequency of the second drive signal SD2 decreases linearly from the second highest frequency Ftx2 at the transmission start time Tts to the second lowest frequency Fti2 at the transmission end time Tte. The down chirp of the second drive signal SD2 is configured such that the intermediate frequency Ftc2 of the second frequency band Bt2 coincides with an average frequency of the second frequency band Bt2.

[0053] The first drive signal SD1 and the second drive signal SD2 are configured to partially overlap each other. In particular, the first frequency band Bt1 and the second frequency band Bt2 are configured such that the first lowest frequency Fti1 and the second lowest frequency Fti2 are different from each other. The first frequency band Bt1 and the second frequency band Bt2 are additionally configured such that the first highest frequency Ftx1 and the second highest frequency Ftx2 are different from each other.

[0054] Specifically, the first frequency band Bt1 and the second frequency band Bt2 of the embodiment are configured such that the second lowest frequency Fti2 is higher than the first lowest frequency Fti1. Furthermore, the first frequency band Bt1 and the second frequency band Bt2 of the embodiment are configured such that the second highest frequency Ftx2 is higher than the first highest frequency Ftx1.

[0055] The first drive signal SD1 and the second drive signal SD2 are configured so that the intermediate frequency Ftc1 and the intermediate frequency Ftc2 are different from each other. Specifically, the intermediate frequency Ftc1 of the embodiment is set to be on the order of 0.5 kHz to several kHz lower than the resonance frequency Fk. In contrast, the intermediate frequency Ftc2 of the embodiment is set to be on the order of 0.5 kHz to several kHz higher than the resonance frequency Fk.

[0056] The transmitter unit 20A, which includes the transducer 2 serving as the transmitter means for transmitting ultrasonic waves, has the resonant frequency Fk. The transducer 21 configured as a resonant ultrasonic microphone has a frequency characteristic substantially identical to a frequency characteristic of a typical bandpass filter.

[0057] That is, a frequency range for which the transmitter unit 20A can exhibit favorable transmission and reception characteristics of ultrasonic waves is essentially limited to a range of plus or minus a few percent around the resonance frequency Fk. This may result in the tracking capability of the transmitter unit 20A deteriorating if the drive frequency of the transmitter unit 20A is distant from the resonance frequency.

[0058] From this point of view, the transmitter unit 20A has a predetermined transmission frequency range defined inclusively between an upper limit frequency Fu and a lower limit frequency Fd. The transmission frequency range corresponds to a sensitivity range of the transducer 21 when the transducer 21 is used as a receiver device. That is, the upper limit frequency fu of the transmission frequency range of the transmitter unit 20A corresponds to the sensitivity of the transducer 21 of 0 [dB] when the sensitivity of the transducer 21 at the resonance frequency Fk is set to 0 [dB]. The lower limit frequency Fd of the transmission frequency range of the transmitter unit 20A corresponds to the sensitivity of the transducer 21 of -3 [dB] when the sensitivity of the transducer 21 at the resonance frequency Fk is set to 0 [dB].

[0059] The first lowest frequency Fti1 of the embodiment is set to be equal to the lower limit frequency Fd of the transmitter unit 20A. The second highest frequency Ftx2 of the embodiment is set to be equal to the upper limit frequency Fu of the transmitter unit 20A.

[0060] As described above, the frequency-modulated first drive signal SD1 differs from the frequency-modulated second drive signal SD2. The frequency of a transmitter wave is determined based on the drive frequency of the transducer 21, that is, an excitation frequency of the transducer 21. For this reason, a transmitter wave, that is, a transmitter wave burst, has, as an identifying feature, a frequency change depending on the temporal change of the drive frequency. That is, the frequency-modulated transmitter wave of the first drive signal SD1 and the frequency-modulated transmitter wave of the second drive signal SD2 have respective features that are different from each other.

[0061] When an echo resulting from the reflection of a transmitter wave by the object B is received by the transducer 21 serving as a receiver, the receiver circuit 23 generates a received signal based on the echo received by the transducer 21. If the echo received by the transducer 21 is a regular echo, the received signal has a frequency-modulated characteristic substantially identical to a frequency-modulated characteristic of the transmitter wave transmitted from the same transducer 21.

[0062] From this point of view, the detection unit 42 is configured to calculate the degree of agreement between a Doppler shift-corrected received signal, which has been corrected according to the Doppler shift detected by the Doppler shift detector 43, and the reference signal, and to identify whether the Doppler shift-corrected received signal is based on a regular echo. Upon determining that the Doppler shift-corrected received signal is based on a regular echo, the detection unit 42 is configured to detect the object B based on the Doppler shift-corrected received signal, thereby obtaining the distance of the object B from the transducer 21.

[0063] The embodiment uses the first drive signal SD1 and the second drive signal SD2 as the drive signal. Specifically, the drive signal generator 3 is capable of outputting a selected one of the first drive signal SD1 and the second drive signal SD2. The frequency of the first drive signal SD1 is configured to change over time within the first frequency band Bt1 defined between the first lowest frequency Fti1 and the first highest frequency Ftx1. The second drive signal SD2 is configured to change over time within the second frequency band Bt2 defined between the second lowest frequency Fti2 and the second highest frequency Ftx2.

[0064] The second frequency band Bt2 and the first frequency band Bt1 are superimposed or overlapped with each other, while the intermediate frequency Ftc2 of the second frequency band Bt2 differs from the intermediate frequency Ftc1 of the first frequency band Bt1. This means that the second frequency band Bt2 partially overlaps with the first frequency band Bt1.

[0065] The received signal based on an echo resulting from a transmitter wave generated based on the first drive signal SD1 is referred to as a first received signal SR1. Similarly, the received signal based on an echo resulting from a transmitter wave generated based on the second drive signal SD2 is referred to as a second received signal SR2.

[0066] In Fig. 3, reference symbol T represents time, reference symbol Trs represents a reception time of a portion of the transmitter wave transmitted at the transmission start time Tse, and reference symbol Tre represents a reception time of a portion of the transmitter wave transmitted at the transmission end time Tte. In Fig. 3, reference symbol Va represents the amplitude of each of the first and second received signals SR1 and SR2, and reference symbol F represents a frequency of each of the first and second received signals SR1 and SR2.

[0067] Hereinafter, the frequency of the first received signal SR1 is referred to as a first received frequency, and the frequency of the second received signal SR2 is referred to as a second received frequency.

[0068] In relation to Fig. 3, the first received frequency F of the first received signal SR1 corresponding to the first up-chirp drive signal SD1 becomes a lowest value Fri1 at time Tr1, which is substantially the midpoint between the reception start time Trs and the reception completion time Tre. In addition, the first received frequency F of the first received signal SR1 gradually increases from time Tr1 and reaches a highest value Frx1 at the reception completion time Tre.

[0069] The increase amount ΔFr1 of the first received frequency F of the first received signal SR1 represents an identification feature of the first received signal SR1 and represents the deviation of the highest value Frx1 from the lowest value Fri1. A median value Frc1 between the highest value Frx1 and the lowest value Fri1 of the first received frequency F of the first received signal SR1 is lower than the resonance frequency Fk.

[0070] In contrast, with regard to Fig. 3, the second received frequency F of the second received signal SR2 corresponding to the second down-chirp drive signal SD2 has a highest value Frx2 at time Tr2, which is substantially the midpoint time between the reception start time Trs and the reception completion time Tre. In addition, the second received frequency F of the second received signal SR2 gradually decreases from time Tr2 and reaches a lowest value Fri2 at the reception completion time Tre.

[0071] The amount of reduction ΔFr2 of the second received frequency F of the second received signal SR2 represents an identification feature of the second received signal SR2 and represents the deviation of the highest value Frx2 from the lowest value Fri2. A median value Frc2 between the highest value Frx2 and the lowest value Fri2 of the second received frequency F of the second received signal SR2 is higher than the resonance frequency Fk.

[0072] Fig. Figure 4 illustrates how the two first received signals SR1 change over time when two first received signals SR1 are successively received by the receiver circuit 23. As shown in Figure 4, an unintended frequency pattern signal SRF based on the second down-chirp drive signal SD2 is generated between the adjacent two first received signals SR1.

[0073] However, when the second received signal SR2 is generated based on the second down-chirp drive signal SD2, the second received signal SR2 should be shifted to be higher than the unintended frequency pattern signal SRF. This therefore effectively reduces erroneous identification of the two first received signals SR1 due to the presence of the unintended frequency pattern signal SRF.

[0074] In contrast, a first comparative example is given below with regard to the Fig. 5 and Fig. 6. The first comparative example is configured such that the first up-chirp drive signal SD1 and the second down-chirp drive signal SD2 are designed not to overlap. Fig. 5 of the first comparison example corresponds to the Fig. 2 of the embodiment, and Fig. 6 of the first comparison example corresponds to the Fig. 3 of the embodiment.

[0075] Specifically, the first drive signal SD1 of the first comparative example is configured such that the frequency of the first drive signal SD1 linearly increases from the first lowest frequency Fti1 at the transmission start time Tts to the first highest frequency Ftx1 at the transmission completion time Tte. The first lowest frequency Fti1 of the first comparative example is set to be equal to the lower limit frequency Fd of the transmission frequency range of the above-mentioned transmitter unit 20A. The first highest frequency Ftx1 of the first comparative example is set to be equal to the resonance frequency Fk of the transmitter unit 20A.

[0076] As a result, the first frequency band Bt1 of the first comparative example lies within a frequency range between the lower limit frequency Fd and the resonance frequency Fk; the frequency range is arranged to be lower than the resonance frequency Fk of the transmission frequency range of the above-mentioned embodiment.

[0077] In addition, the second drive signal SD2 of the first comparative example is configured such that the frequency of the second drive signal SD2 linearly decreases from the second highest frequency Ftx2 at the transmission start time Tts to the second lowest frequency Fti2 at the transmission end time Tte. The second lowest frequency Fti2 of the first comparative example is set to be equal to the resonance frequency Fk of the transmitter unit 20A. The second highest frequency Ftx2 of the first comparative example is set to be equal to the upper limit frequency Fu of the transmission frequency range of the transmitter unit 20A set forth above.

[0078] As a result, the second frequency band Bt2 of the first comparative example lies within a frequency range between the resonance frequency Fk and the upper limit frequency Fu; the frequency range is arranged to be higher than the resonance frequency Fk of the transmission frequency range of the above-described embodiment.

[0079] In relation to Fig. 6, the first frequency band Bt1 and the second frequency band Bt2 of the first comparative example are each set to be narrower than the corresponding ones of the first frequency band Bt1 and the second frequency band Bt2 of the presented embodiment. This setting results in the increase amount ΔFr1 of the first received frequency F of the first received signal SR1 according to the first comparative example being smaller than the increase amount ΔFr1 of the first received frequency F of the first received signal SR1 according to the previous embodiment.

[0080] Similarly, this setting results in the decrease amount ΔFr2 of the second received frequency F of the second received signal SR2 according to the first comparative example being smaller than the decrease amount ΔFr2 of the second received frequency F of the second received signal SR2 according to the previous embodiment.

[0081] The first comparative example therefore results in an individual identification accuracy of each of the first and second received signals SR1 and SR2 being lower than an individual identification accuracy of the corresponding one of the first and second received signals SR1 and SR2 according to the previous embodiment.

[0082] In addition, a second comparative example is presented below with regard to the Fig. 7 to 9.

[0083] The second comparative example is configured such that the first up-chirp drive signal SD1 and the second down-chirp drive signal SD2 are designed to completely overlap each other. Fig. 7 to 9 of the second comparative example correspond to the Fig. 2 to 4 of the embodiment.

[0084] In relation to Fig. 7, the first drive signal SD1 of the second comparative example is configured such that the frequency of the first drive signal SD1 linearly increases from the first lowest frequency Fti1 at the transmission start time Tts to the first highest frequency Ftx1 at the transmission end time Tte. The first lowest frequency Fti1 of the second comparative example is set to be equal to the lower limit frequency Fd of the transmission frequency range of the above-mentioned transmitter unit 20A. The first highest frequency Ftx1 of the second comparative example is set to be equal to the upper limit frequency Fu of the transmission frequency range of the above-mentioned transmitter unit 20A.

[0085] In addition, the second drive signal SD2 of the first comparative example is configured such that the frequency of the second drive signal SD2 linearly decreases from the second highest frequency Ftx2 at the transmission start time Tts to the second lowest frequency Fti2 at the transmission end time Tte. The second lowest frequency Fti2 of the second comparative example is set to be equal to the lower limit frequency Fd of the transmission frequency range of the above-mentioned transmitter unit 20A. The second highest frequency Ftx2 of the second comparative example is set to be equal to the upper limit frequency Fu of the transmission frequency range of the above-mentioned transmitter unit 20A.

[0086] In relation to Fig. 8, each of the first frequency band Bt1 and the second frequency band Bt2 of the second comparative example is set to be narrower than the corresponding one of the first frequency band Bt1 and the second frequency band Bt2 of the previously described embodiment. This setting results in the increase amount ΔFr1 of the first received frequency F of the first received signal SR1 according to the second comparative example being larger than the increase amount ΔFr1 of the first received frequency F of the first received signal SR1 according to the previous embodiment.

[0087] Similarly, this setting results in the decrease amount ΔFr2 of the second received frequency F of the second received signal SR2 according to the second comparative example being larger than the decrease amount ΔFr2 of the second received frequency F of the second received signal SR2 according to the previous embodiment.

[0088] As in Fig. As shown in Figure 9, when two first received signals SR1 are consecutively received by the receiver circuit 23, an unintended frequency pattern signal SRF based on the second down-chirp drive signal SD2 is generated between the adjacent two first received signals SR1. Since it is difficult to distinguish the unintended frequency pattern signal SRF from the second received signal SR2, which may be generated based on the second down-chirp drive signal SD2, the second comparative example may result in erroneous identification of the two first received signals SR1 due to the presence of the unintended frequency pattern signal SRF.

[0089] As described by comparing the embodiment with the first and second comparative examples, the configuration of the embodiment results in higher accuracy in identifying the first received signal SR1 and the second received signal SR2. In addition, the configuration of the embodiment enables the first and second received signals SR1 and SR2 to be individually identified with higher identification accuracy.

[0090] The configuration of the embodiment therefore enables the object detection device 1 to have an overall higher identification accuracy of the received signals.

[0091] Typical modifications of the embodiments will be described below. Specifically, one or more different points of the typical modifications compared to the embodiment will be described below.

[0092] In the embodiment and typical modifications, the same reference numerals are assigned to the same or corresponding portions between the embodiment and the typical modifications. In the following descriptions of the typical modifications, for the descriptions of each component having the same reference numeral as that of the corresponding component of the embodiment, the previous descriptions of the corresponding component in the embodiment can be applied, as long as there is no technical inconsistency between the same components or there is no additional explanation for the corresponding component of the typical modifications.

[0093] The object detection device 1 is not limited to having a configuration installable in a vehicle and may therefore have a configuration installable in a watercraft or an aircraft.

[0094] The object detection device 1 is not limited to a configuration consisting of the single transceiver 2 and the single drive signal generator 3 as described above. Specifically, the object detection device 1 may be equipped with a plurality of transceivers 2 and a plurality of signal generators 3, the number of which corresponds to the number of the plurality of transceivers 2.

[0095] The object detection device 1 is not limited to a configuration in which the single transducer 21 is capable of performing both the transmission function of transmitting ultrasonic waves and the reception function of receiving echoes. That is, the object detection device 1 may be configured to include a first transducer 21 and a second transducer 22 in parallel. The first transducer 21 is electrically connected to the transmitter circuit 22 and is configured to transmit ultrasonic waves. The second transducer 22 is electrically connected to the receiver circuit 23 and is configured to receive echoes.

[0096] The object detection device 1 may be configured such that a drive signal of a predetermined type is input to the single transceiver 2. That is, the drive signal generator 3 of the object detection device 1 installed in the own vehicle may be configured to output only the first drive signal SD1. The drive signal generator 3 of the object detection device 1 installed in another vehicle may be configured to output only the second drive signal SD2. The drive signal generator 3 of the object detection device 1 installed in another vehicle may be configured to output a third drive signal with a frequency modulation different from the frequency modulation of each of the first and second drive signals SD1 and SD2. The third drive signal may be configured as a constant frequency signal, such as the resonance frequency Fk.

[0097] When the object detection device 1 includes a plurality of transceivers 2, the object detection device 1 may be configured such that drive signals having different waveforms from each other are input to the respective transceivers 2.

[0098] For example, if the object detection device 1 has a first and a second transceiver 2, the object detection device 1 may be configured such that the first and second drive signals SD1 and SD2 are input to the respective first and second transceivers 2.

[0099] The object detection device 1 may be configured to use at least three types of drive signals, such as the first drive signal SD1, the second drive signal SD2, and a third drive signal with a frequency modulation different from the frequency modulation of each of the first and second drive signals SD1 and SD2. This enables the transmitter waves transmitted from the transceivers 2 to be properly distinguished from each other. That is, the present disclosure is not limited to two types of drive signals, such as the first drive signal SD1 and the second drive signal SD2. Specifically, the drive signal generator 3 may be configured to selectively output one of the at least three types of drive signals including the first drive signal SD1 and the second drive signal SD2.The transmission control unit 41 may be configured to instruct the drive signal generator 3 to output a selected one of the at least three drive signals.

[0100] The object detection device 1 may be configured to detect a two-dimensional position of the object B relative to the own vehicle using a plurality of transducers 21 according to a known triangulation method. The object detection device 1 of this modification may be configured so that the transducers 21 installed in the own vehicle each transmit transmitter waves having a predetermined frequency characteristic. In this modification, a regular echo is a received echo resulting from one of the transmitter waves transmitted from the own vehicle, and an irregular echo is a received echo resulting from another transmitter wave transmitted from another vehicle.

[0101] The configuration of each component of the object detection device 1, such as the configuration of the transmitter circuit 22 or the configuration of the receiver circuit 23, is not limited to those described in the embodiment.

[0102] For example, the D / A converter may be installed in the drive signal generator instead of in the transmitter circuit 22.

[0103] The present invention may use any of various drive signal waveforms other than the drive signal waveform described in the embodiment. For example, the first drive signal SD1 may have nonlinear frequency modulation, which may have the intermediate frequency Ftc1 and the average frequency different from each other. Specifically, the intermediate frequency Ftc1 according to this modification may be set to the center frequency or average frequency of the first frequency band Bt1. The intermediate frequency Ftc2 according to this modification may be set to the center frequency or average frequency of the second frequency band Bt2.

[0104] Fig. 10 represents a first partial modification of the Fig. 2. In particular, the temporal down-chirp frequency change, which is referred to as the Fig. 2 is changed into a temporal up-chirp frequency change, and the first drive signal SD1 according to the first partial modification is designed to have the temporal up-chirp frequency change (see Fig. 10).

[0105] Similarly, the temporal up-chirp frequency change, which is referred to as the Fig. 2 is changed into a temporal downward chirp frequency change, and the second drive signal SD2 according to the partial modification is designed to have the temporal downward chirp frequency change (see Fig. 10).

[0106] That is, the first drive signal SD1 of the first partial modification is designed such that the frequency of the first drive signal SD1 increases linearly from the first lowest frequency Fti1 at the transmission start time Tts to the first highest frequency Ftx1 at the transmission end time Tte.

[0107] In contrast, the second drive signal SD2 of the first partial modification is designed such that the frequency of the second drive signal SD2 decreases linearly from the second highest frequency Ftx2 at the transmission start time Tts to the second lowest frequency Fti2 at the transmission end time Tte.

[0108] The first frequency band Bt1 and the second frequency band Bt2 of the first partial modification are designed such that the second lowest frequency Fti2 is lower than the first lowest frequency Fti1. Additionally, the first frequency band Bt1 and the second frequency band Bt2 of the first partial modification are designed such that the second highest frequency Ftx2 is lower than the first highest frequency Ftx1.

[0109] The second lowest frequency Fti2 of the first partial modification is set to coincide with the lower limit frequency Fd of the previously described transmission frequency range of the transmitter unit 20A of the first partial modification. In addition, the first highest frequency Ftx1 of the first partial modification is set to coincide with the upper limit frequency Fu of the previously described transmission frequency range of the transmitter unit 20A of the first partial modification.

[0110] The intermediate frequency Ftc1 according to the first partial modification is set to be on the order of 0.5 kHz to several kHz higher than the resonant frequency Fk. In contrast, the intermediate frequency Ftc2 of the embodiment is set to be on the order of 0.5 kHz to several kHz lower than the resonant frequency Fk.

[0111] The first and second control signals SD1 and SD2 of the first partial modification, which are shown in Fig. 10 achieve the same technical advantages as those described in the embodiment.

[0112] Fig. 11 represents a second partial modification of the Fig. 2. In particular, the first and second drive signals SD1 and SD2 according to the second partial modification are designed such that the frequency of the corresponding first and second drive signals SD1 and SD2 changes stepwise.

[0113] In particular, the first control signal SD1 according to the second partial modification is designed such that (1) The drive frequency is maintained at the first lowest frequency Fti1 from the transmission start time Tts to an intermediate time Ttm (2) The driving frequency changes gradually from the first lowest frequency Fti1 to the first highest frequency Ftx1 at the intermediate time Ttm (3) The drive frequency is maintained at the first highest frequency Ftx1 from the intermediate time Ttm to the transmission completion time Tte

[0114] The intermediate time Ttm represents a time essentially halfway between the transmission start time Tts and the transmission end time Tte.

[0115] The first lowest frequency Fti1, the first highest frequency Ftx1 and the intermediate frequency Ftc1 according to the second partial modification are the same as those described in the embodiment.

[0116] In addition, the second control signal SD2 according to the second partial modification is designed such that (1) The drive frequency is kept at the second highest frequency Ftx2 from the transmission start time Tts to the intermediate time Ttm (2) The driving frequency changes gradually from the second highest frequency Ftx2 to the second lowest frequency Fti2 at the intermediate time Ttm (3) The drive frequency is maintained at the second lowest frequency Fti2 from the intermediate time Ttm to the transmission completion time Tte

[0117] The second lowest frequency Fti2, the second highest frequency Ftx2 and the intermediate frequency Ftc2 according to the second partial modification are the same as those described in the embodiment.

[0118] The first and second control signals SD1 and SD2 of the second partial modification, which are shown in Fig. 11 achieve the same technical advantages as those described in the embodiment.

[0119] Both the first control signal SD1 and the second control signal SD2, which are Fig.11, has a corresponding discrete frequency change, but the present disclosure is not limited thereto. Specifically, the driving frequency of each of the first driving signal SD1 and the second driving signal SD2 may change linearly around the intermediate time Ttm. In addition, the frequency of each of the first driving signal SD1 and the second driving signal SD2 may change in a sigmoid curve.

[0120] The elements constituting the embodiment are not necessarily to be interpreted as essential components, unless (i) at least one of the elements is clearly designated as essential or (ii) at least one of the elements is generally regarded as an essential element.

[0121] Where the embodiment describes specific numerical values ​​representing, for example, the number of some elements, a value or quantity that at least one parameter takes, and / or one or more specific ranges, the present disclosure is not limited to the specific numerical values ​​unless (i) the concrete numerical values ​​are clearly described as essential or (ii) the present disclosure is in principle clearly limited to the specific numerical values.

[0122] Similarly, while the embodiment describes the specific shapes of a plurality of elements, the specific directions of the plurality of elements, and / or the specific positional relationship between the plurality of elements, the present disclosure is not limited to the specific shapes of a plurality of elements, the specific directions of the various elements, and / or the specific positional relationship between the plurality of elements, except that (i) The specific shapes of several elements, the specific directions of the several elements and / or the specific positional relationship between the several elements are clearly described as essential or (ii) The present disclosure is generally limited to the specific shapes of a plurality of elements, the specific directions of the plurality of elements, and / or the specific positional relationship between the plurality of elements.

Claims

[1] A device (1) configured to detect an object (B) around the device (1), the device (1) comprising: a drive signal generator (3) configured to generate a drive signal for driving a transmitter unit (20A) so that a transmitter device of the transmitter unit (20A) transmits a transmitter wave to the outside; and a detection unit (42) configured to: Receiving an echo resulting from the reflection of the transmitter wave by the object (B) via a receiver device (21); and Obtaining a received signal based on the received echo, thereby detecting the object (B) based on the received signal, where: the drive signal generator (3) is configured to selectively output one of the first drive signal (SD1) and the second drive signal (SD2) as the drive signal; the first drive signal (SD1) has a first temporal frequency change within a first frequency band (Bt1) defined inclusively from a first lowest frequency (Fti1) to a first highest frequency (Ftx1); the first frequency band (Bt1) has a first intermediate frequency (Ftc1) which is defined as one of the frequencies, center frequency and average frequency, of the first frequency band (Bt1); the second drive signal (SD2) has a second temporal frequency change within a second frequency band (Bt2) defined inclusively from a second lowest frequency (Fti2) to a second highest frequency (Ftx2); the second frequency band (Bt2) has a second intermediate frequency (Ftc2) which is defined as one of the frequencies, center frequency and average frequency, of the second frequency band (Bt2); the second intermediate frequency (Ftc2) is different from the first intermediate frequency (Ftc1); the second frequency band (Bt2) is partially superimposed on the first frequency band (Bt1); the received signal of the echo resulting from a reflection of the transmitter wave based on the first drive signal (SD1) is referred to as a first received signal (SR1); the received signal of the echo resulting from a reflection of the transmitter wave based on the second drive signal (SD2) is referred to as a second received signal (SR2), wherein a frequency increasing direction of the second drive signal (SD2) is opposite to a frequency increasing direction of the first drive signal (SD1); and the device (1) is configured, when acquiring two of the first received signals (SR1) consecutively, to reduce erroneous identification of an unintended frequency pattern signal (SRF) as the second received signal (SR2) according to a characteristic according to which the second received signal (SR2) is shifted to be higher than the unintended frequency pattern signal (SRF). [2] Device (1) according to claim 1, further comprising: a transmission control unit (41) configured to instruct the drive signal generator (3) to selectively output one of the first drive signal (SD1) and the second drive signal (SD2). [3] Device (1) according to claim 1 or 2, wherein: the first frequency band (Bt1) and the second frequency band (Bt2) are each designed to contain a resonance frequency of the transmitter unit (20A). [4] Device (1) according to one of claims 1 to 3, wherein: the first frequency band (Bt1) and the second frequency band (Bt2) are such that: the first lowest frequency (Fti1) and the second lowest frequency (Fti2) are different from each other; and the first highest frequency (Ftx1) and the second highest frequency (Ftx2) are different from each other. [5] Device (1) according to claim 4, wherein: the first frequency band (Bt1) and the second frequency band (Bt2) are such that: the second lowest frequency (Fti2) is higher than the first lowest frequency (Fti1); and the second highest frequency (Ftx2) is higher than the first highest frequency (Ftx1). [6] Device (1) according to claim 5, wherein: the transmitter unit (20A) has a predetermined transmission frequency range defined including a lower limit frequency (Fd) and an upper limit frequency (Fu); the first lowest frequency (Fti1) is set equal to the lower limit frequency (Fd) of the transmission frequency range of the transmitter unit (20A); and the second highest frequency (Ftx2) is set equal to the upper limit frequency (Fu) of the transmission frequency range of the transmitter unit (20A). [7] Device (1) according to one of claims 1 to 6, wherein: the first temporal frequency change of the first control signal (SD1) includes a temporal frequency increase towards the first highest frequency (Ftx1); and the second temporal frequency change of the second control signal (SD2) includes a temporal frequency decrease towards the second lowest frequency (Fti2). [8] Device (1) according to claim 7, wherein: the first temporal frequency change of the first drive signal (SD1) includes a frequency increase from the first lowest frequency (Fti1) to the first highest frequency (Ftx1) as the temporal frequency increase; and the second temporal frequency change of the second control signal (SD2) includes a frequency decrease from the second highest frequency (Ftx2) to the second lowest frequency (Fti2) as the temporal frequency decrease. [9] A method for detecting a surrounding object (B), the method comprising: Causing a drive signal generator (3) to generate a drive signal for driving a transmitter unit (20A) so that a transmitter device (21) of the transmitter unit (20A) transmits a transmitter wave to the outside; Cause a detection unit (42): receives an echo resulting from the reflection of the transmitter wave by the object (B) via a receiver device (21); and receives a received signal based on the received echo, thereby detecting the object (B) based on the received signal, where: the object detection method selectively uses one of the first drive signal (SD1) and the second drive signal (SD2) as the drive signal; the first drive signal (SD1) has a first temporal frequency change within a first frequency band (Bt1) defined inclusively from a first lowest frequency (Fti1) to a first highest frequency (Ftx1); the first frequency band (Bt1) has a first intermediate frequency (Ftc1) which is defined as one of the frequencies, center frequency and average frequency, of the first frequency band (Bt1); the second drive signal (SD2) has a second temporal frequency change within a second frequency band (Bt2) defined inclusively from a second lowest frequency (Fti2) to a second highest frequency (Ftx2); the second frequency band (Bt2) has a second intermediate frequency (Ftc2) which is defined as one of the frequencies, center frequency and average frequency, of the second frequency band (Bt2); the second intermediate frequency (Ftc2) is different from the first intermediate frequency (Ftc1); the second frequency band (Bt2) is partially superimposed on the first frequency band (Bt1); the received signal of the echo resulting from a reflection of the transmitter wave based on the first drive signal (SD1) is referred to as a first received signal (SR1); the received signal of the echo resulting from a reflection of the transmitter wave based on the second drive signal (SD2) is referred to as a second received signal (SR2), wherein a frequency increasing direction of the second drive signal (SD2) is opposite to a frequency increasing direction of the first drive signal (SD1); and the method, when two of the first received signals (SR1) are successively acquired, reduces erroneous identification of an unintended frequency pattern signal (SRF) as the second received signal (SD2) according to a characteristic according to which the second received signal (SD2) is shifted to be higher than the unintended frequency pattern signal (SRF). [10] The method of claim 9, further comprising: Instructing the drive signal generator (3) to selectively output one of the signals, first drive signal (SD1) and second drive signal (SD2). [11] A method according to claim 9 or 10, wherein: the first frequency band (Bt1) and the second frequency band (Bt2) are each designed to contain a resonance frequency of the transmitter unit (20A). [12] A method according to any one of claims 9 to 11, wherein: the first frequency band (Bt1) and the second frequency band (Bt2) are designed so that: the first lowest frequency (Fti1) and the second lowest frequency (Fti2) are different from each other; and the first highest frequency (Ftx1) and the second highest frequency (Ftx2) are different from each other. [13] The method of claim 12, wherein: the first frequency band (Bt1) and the second frequency band (Bt2) are designed so that: the second lowest frequency (Fti2) is higher than the first lowest frequency (Fti1); and the second highest frequency (Ftx2) is higher than the first highest frequency (Ftx1). [14] The method of claim 13, wherein: the first lowest frequency (Fti1) is set equal to the lower limit frequency (Fd) of the transmission frequency range of the transmitter unit (20A); and the second highest frequency (Ftx2) is set equal to the upper limit frequency (Fu) of the transmission frequency range of the transmitter unit (20A). [15] A method according to any one of claims 9 to 14, wherein: the first temporal frequency change of the first control signal (SD1) includes a temporal frequency increase towards the first highest frequency (Ftx1); and the second temporal frequency change of the second control signal (SD2) includes a temporal frequency decrease towards the second lowest frequency (Fti2). [16] The method of claim 15, wherein: the first temporal frequency change of the first drive signal (SD1) includes a frequency increase from the first lowest frequency (Fti1) to the first highest frequency (Ftx1) as the temporal frequency increase; and the second temporal frequency change of the second control signal (SD2) includes a frequency decrease from the second highest frequency (Ftx2) to the second lowest frequency (Fti2) as the temporal frequency decrease.

Images