Target detection device and target detection method

Abstract

[Problem] To provide a target detection device and a target detection method that can detect, with a simple configuration, a target. [Solution] A target detection device 1 comprises a first transmission-signal generating unit 111 for generating a first transmission signal, a second transmission-signal generating unit 121 for generating a second transmission signal, a wave transmission array 10 including a plurality of wave transmission elements 10a for converting the first transmission signal into a transmission wave, a first signal switching unit 113 for supplying the first transmission signal to one of the wave transmission elements 10a in the wave transmission array 10, a second signal switching unit 123 for supplying the second transmission signal to one of the wave transmission elements 10a in the wave transmission array 10, and a control unit 101 for controlling the first signal switching unit 113 to switch the wave transmission element 10a, to which the first transmission signal is supplied, from an element n to an element n+1 and controlling the second signal switching unit 123 to switch the wave transmission element, to which the second transmission signal is supplied, from an element m to an element m+1.

Description

[Technical Field]

[0001] The present invention relates to a target detection device and a target detection method that transmit a transmission wave and detect a target based on the reflected wave. [Background technology]

[0002] Conventionally, target detection devices are known that transmit a transmitted wave and detect a target based on the reflected wave. In this type of target detection device, targets are detected using, for example, a wave-transmitting / receiving array in which elements for transmitting and receiving waves are arranged two-dimensionally. For example, a transmitted wave is transmitted using the central element of the wave-transmitting / receiving array, and reflected waves are received using all elements of the wave-transmitting / receiving array. During wave reception, receive beams are formed in various directions by phase control for all elements, and received signals are generated for each direction. Targets are detected for each direction by processing the received signals for each direction.

[0003] Patent Document 1 discloses this type of target detection device. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] U.S. Patent No. 7,355,924 Summary of the Invention [Problem to be solved by the invention]

[0005] In a target detection device with the above configuration, the number of elements in the transmit / receive array is large, and the number of transmit channels and receive channels is also large, which makes the configuration of the target detection device complex and makes it difficult to reduce costs.

[0006] In view of the above problem, an object of the present invention is to provide a target detection device and a target detection method that are capable of detecting a target with a simple configuration. [Means for solving the problem]

[0007] A first aspect of the present invention relates to a target detection device, including a first transmission signal generator that generates a first transmission signal, a second transmission signal generator that generates a second transmission signal, a first wave transmitting array having a plurality of first wave transmitting elements that convert the first transmission signal and the second transmission signal into transmission waves, a first signal switching unit that supplies the first transmission signal to one of the first wave transmitting elements in the first wave transmitting array, a second signal switching unit that supplies the second transmission signal to one of the first wave transmitting elements in the first wave transmitting array, and a control unit that performs first control in which the first signal switching unit switches the first wave transmitting element to which the first transmission signal is supplied from element n to element n+1, and the second signal switching unit switches the first wave transmitting element to which the second transmission signal is supplied from element m to element m+1.

[0008] According to the target detection device of the first aspect, the first transmitting element to which the first transmission signal is supplied is switched from element n to element n+1 in the first transmitting array, thereby moving the transmitting source of the transmission wave in the arrangement direction of the first transmitting elements. As a result, the frequency of the transmission beam changes depending on the transmission direction due to the Doppler effect, and multiple iso-frequency planes (planes with the same frequency fluctuation due to the Doppler effect) are formed in the transmission beam. Therefore, by extracting signals corresponding to each iso-frequency plane from the reception signals generated by the receiving elements, it is possible to obtain reception signals based on the reflected waves from each iso-frequency plane.

[0009] At this time, the first transmitting element to which the second transmission signal is supplied is switched from element m to element m+1 in the first transmitting array. This causes the sweep of the first transmitting array by the first signal switching unit and the sweep of the first transmitting array by the second signal switching unit to partially overlap, preventing ripples from occurring in the transmission waveform and the reception processing result (constant frequency received signal). This improves the target detection accuracy.

[0010] In this way, according to the target detection device of the first aspect, targets can be accurately detected in each iso-frequency plane with a simple configuration in which the first transmitting element to which the first transmission signal and the second transmission signal are supplied is switched within the first transmitting array.

[0011] The target detection device according to the first aspect may be configured such that, in the first wave transmitting array, the element n+1 is adjacent to the element n, and the element m+1 is adjacent to the element m.

[0012] Furthermore, after the first control, the control unit may be configured to perform a second control in which the first signal switching unit switches the first transmitting element to which the first transmission signal is supplied from element n+1 to element n+2 adjacent to element n+1, and the second signal switching unit switches the first transmitting element to which the second transmission signal is supplied from element m+1 to element m+2 adjacent to element m+1.

[0013] With these configurations, the first transmission signal and the second transmission signal are supplied to adjacent first wave-transmitting elements in sequence, so that the transmission wave source can be moved finely in the direction in which the first wave-transmitting elements are arranged, thereby smoothly generating frequency changes due to the Doppler effect.

[0014] In the target detection device according to the first aspect, when the first transmitting array has P first transmitting elements, if P is an even number, (P / 2)-1 first transmitting elements may be included between element n and element m, and if P is an odd number, (P-1) / 2 or {(P-1) / 2}-1 first transmitting elements may be included between element n and element m.

[0015] By setting element n and element m in this way, the second signal switching unit starts sweeping the first transmitting array around the middle of the cycle in which the first signal switching unit sweeps the first transmitting array, which allows the sweeps to overlap by half a cycle, more effectively suppressing ripples in the received signal.

[0016] In the target detection device according to the first aspect, when the first transmitting array includes P first transmitting elements from first transmitting element 1 to first transmitting element P, if element n+1 corresponds to a first transmitting element beyond first transmitting element P, the first signal switching unit may be configured to switch the first transmitting element to which the first transmission signal is supplied from first transmitting element P to first transmitting element 1, and if element m+1 corresponds to a first transmitting element beyond first transmitting element P, the second signal switching unit may be configured to switch the first transmitting element to which the second transmission signal is supplied from first transmitting element P to first transmitting element 1.

[0017] According to this configuration, the first transmitting array is repeatedly swept with the first transmitting signal and the second transmitting signal, which increases the transmission energy of one pulse and widens the detectable distance range.

[0018] In the target detection device according to the first aspect, the first transmission signal may be a frequency-modulated signal, and the second transmission signal may be a frequency-modulated signal.

[0019] This allows for improved distance resolution in target detection by performing reception processing using a matched filter.

[0020] In the target detection device according to the first aspect, the plurality of first wave transmitting elements are grouped into a plurality of groups, and a plurality of the first wave transmitting elements are connected in each group, the first signal switching unit is configured to supply the first transmission signal to one of the groups in the first wave transmitting array, and the second signal switching unit is configured to supply the second transmission signal to one of the groups in the first wave transmitting array, and during first control by the control unit, the first signal switching unit is configured to switch the group to which the first transmission signal is supplied from group g to group g+1, and the second signal switching unit is configured to switch the group to which the second transmission signal is supplied from group h to group h+1.

[0021] With this configuration, the transmission waves are transmitted for each group, which increases the output power and directional gain of the transmission waves. Furthermore, the supply of transmission signals is switched between groups, which allows the transmission source of the transmission waves to be moved. Therefore, the Doppler effect can cause a change in the frequency of the transmission beam.

[0022] In this configuration, the group g and the group g+1 may be configured to share at least one of the first transmit elements, and the group h and the group h+1 may be configured to share at least one of the first transmit elements.

[0023] This configuration allows the source of the transmitted wave to be moved finely, thereby smoothly changing the frequency due to the Doppler effect.

[0024] In the target detection device according to the first aspect, the element n may be supplied with a first portion of the first transmission signal, and the element n+1 may be supplied with a second portion of the first transmission signal that is different from the first portion. Furthermore, the element m may be supplied with a first portion of the second transmission signal, and the element m+1 may be supplied with a second portion of the second transmission signal that is different from the first portion of the second transmission signal. For example, when frequency-modulated signals such as chirp signals are supplied as the first transmission signal and the second transmission signal, the portions of the signal waveforms supplied to the element n and the element n+1 may be different, and the portions of the signal waveforms supplied to the element m and the element m+1 may be different.

[0025] The target detection device according to the first aspect may further include a third transmission signal generator that generates a third transmission signal, a fourth transmission signal generator that generates a fourth transmission signal, a second wave transmitting array having a plurality of second wave transmitting elements that convert the third transmission signal and the fourth transmission signal into transmission waves, a third signal switching unit that supplies the third transmission signal to one of the second wave transmitting elements in the second wave transmitting array, and a fourth signal switching unit that supplies the fourth transmission signal to one of the second wave transmitting elements in the second wave transmitting array. In this configuration, the control unit may be configured, after the first control, to further perform third control in which the third signal switching unit switches the second wave transmitting element to which the third transmission signal is supplied from element n to element n+1, and the fourth signal switching unit switches the second wave transmitting element to which the fourth transmission signal is supplied from element m to element m+1.

[0026] According to this configuration, by adjusting the first and third transmission signals and adjusting the second and fourth transmission signals, it is possible to prevent unnecessary frequency components from being superimposed on the transmission waves, thereby enabling more accurate processing based on the received signals.

[0027] In this configuration, in the second transmitting array, the element n+1 is adjacent to the element n, and the element m+1 is adjacent to the element m, and the element n of the first transmitting array is adjacent to the element n of the second transmitting array, and the element m of the first transmitting array is adjacent to the element n of the second transmitting array. Preferably, element m is adjacent to element m of the second transmit array.

[0028] According to this configuration, while the transmission source of the transmission wave based on the first transmission signal moves from element n to element n+1 in the first transmission array, the transmission wave based on the third transmission signal is transmitted from element n in the second transmission array at a position between element n and element n+1. Furthermore, while the transmission source of the transmission wave based on the third transmission signal moves from element m to element m+1 in the first transmission array, the transmission wave based on the fourth transmission signal is transmitted from element m in the second transmission array at a position between element m and element m+1. This makes it easier to maintain the continuity of the transmission waves. Therefore, it is possible to prevent unnecessary frequency components from being superimposed on the transmission waves.

[0029] In the target detection device according to the first aspect, the third transmission signal may be a frequency-modulated signal, and the fourth transmission signal may be a frequency-modulated signal.

[0030] The target detection device according to the first aspect may further include a wave receiving array including at least one wave receiving element that receives a reflected wave generated by reflection of the transmitted wave from a target and converts the reflected wave into a received signal.

[0031] In this case, the target detection device may further include a received signal processing unit that processes the received signal, and the received signal processing unit may be configured to extract a received signal based on the reflected wave from an iso-frequency surface corresponding to the frequency based on the frequency component of the received signal.

[0032] As described above, by switching the transmitting element serving as the transmitting source in the direction of arrangement of the transmitting elements and moving the transmitting source, multiple overlapping iso-frequency planes (planes with the same frequency fluctuation due to the Doppler effect) are formed in the transmission beam. Therefore, based on the frequency components of the received signal, it is possible to define the iso-frequency plane corresponding to that frequency, and to extract the iso-frequency received signal, which is the received signal based on the reflected wave from that iso-frequency plane. Therefore, with the above configuration, it is possible to smoothly obtain the iso-frequency received signal for each iso-frequency plane through processing by the received signal processing unit.

[0033] In this configuration, the received signal processing unit can be configured to obtain the iso-frequency received signal of the iso-frequency plane corresponding to each frequency by extracting from the received signal a plurality of frequency components each extracted at a different frequency.

[0034] Alternatively, in this configuration, the received signal processing unit may be configured to calculate a frequency spectrum of the received signal, and acquire the iso-frequency received signal of the iso-frequency plane corresponding to each frequency based on the frequency spectrum.

[0035] In the target detection device according to the first aspect, the receiving array may include a plurality of receiving elements, and the receiving signal processing unit may be configured to perform beamforming based on the receiving signals generated from each of the receiving elements, and to calculate the direction of arrival of the reflected wave from the target based on the beamforming.

[0036] In the target detection device according to the first aspect, the receiving array includes a plurality of receiving elements, and the receiving array, unlike the first transmitting array, can be configured such that a receiving beam generated based on the received signals from each receiving element intersects with a transmitting beam generated by the first transmitting array.

[0037] This configuration allows the calculation of the distribution of intensity data based on the intensity of the reflected waves in the area where the received beam and the transmitted beam (equal frequency surface) intersect. Therefore, by changing the direction of the received beam within the detection range using beamforming, it is possible to generate intensity data that is distributed three-dimensionally within the detection range.

[0038] A second aspect of the present invention relates to a target detection method, which performs a first sweep in which a plurality of wave-transmitting elements arranged in a row are swept with a first transmission signal, and starts a second sweep in which the plurality of wave-transmitting elements are swept with a second transmission signal just before the first sweep ends.

[0039] According to the target detection method of the second aspect, the wave transmission source of the transmission wave moves in the direction in which the wave transmitting elements are arranged, as in the first aspect, and therefore, the same effects as in the first aspect can be achieved.

[0040] In the target detection method according to this aspect, it is preferable that the second sweep is started at a timing near a half cycle of the first sweep.

[0041] This allows the first sweep and the second sweep to overlap by 1 / 2 period, making it possible to more effectively suppress ripples occurring in the received signal. [Effects of the Invention]

[0042] As described above, according to the present invention, it is possible to provide a target detection device and a target detection method that are capable of detecting a target with a simple configuration.

[0043] The effects and significance of the present invention will become more apparent from the following description of the embodiments, however, the embodiments shown below are merely examples of how the present invention can be implemented, and the present invention is not limited to the embodiments described below. [Brief explanation of the drawings]

[0044] [Figure 1] Fig. 1(a) is a diagram showing a configuration of a wave transmitting system according to a reference example, and Fig. 1(b) is a diagram showing a configuration example for moving a wave transmitting source according to an embodiment. [Figure 2] FIG. 2 is a diagram schematically illustrating a state of a sound field when the transmitting array is swept multiple times according to the embodiment. [Figure 3] FIG. 3 is a diagram showing a simulation result of an iso-frequency surface obtained by simulation according to the embodiment. [Figure 4] FIG. 4 is a diagram schematically illustrating an example of the configuration of a wave transmitting and receiving system according to an embodiment. [Figure 5] FIG. 5 is a diagram illustrating an example of application of a window for suppressing side lobes according to a comparative example. [Figure 6] Fig. 6(a) is a diagram showing a simulation result of the waveform of a transmission wave when the window shown in Fig. 5 is applied. Fig. 6(b) is a diagram showing a simulation result of receiving and processing the echo of the transmission wave of Fig. 6(a) by simulating the receiving and processing result. [Figure 7] FIG. 5 is a diagram illustrating an application example of a window according to an embodiment. [Figure 8] Fig. 8(a) is a diagram showing a simulation result of the waveform of a transmission wave when the window shown in Fig. 7 is applied. Fig. 8(b) is a diagram showing a simulation result of reception processing results obtained by simulating the reception processing results of the echo of the transmission wave shown in Fig. 8(a). [Figure 9] FIG. 10 is a diagram illustrating the configuration of a signal switching unit according to an embodiment when a next sweep is started in the middle of one sweep. [Figure 10] FIG. 10 is a block diagram showing a specific configuration of a target detection device according to an embodiment. [Figure 11] Fig. 11(a) is a functional block diagram showing a configuration example of a received signal processing unit according to an embodiment, and Fig. 11(b) is a functional block diagram showing another configuration example of a received signal processing unit according to an embodiment. [Figure 12] 12(a) is a flowchart showing a process for transmitting a transmission wave based on a first transmission signal from a transmitting array according to an embodiment, and FIG. 12(b) is a flowchart showing a process for transmitting a transmission wave based on a second transmission signal from a transmitting array according to an embodiment. [Figure 13] FIG. 13 is a flowchart illustrating a process for processing a received signal and displaying a detected image according to an embodiment. [Figure 14] FIG. 14 is a diagram schematically illustrating a configuration when the target object detection device according to the embodiment is used as a sonar for detecting targets in water. [Figure 15] FIG. 15 is a diagram showing a configuration in which a first transmission signal and a second transmission signal are supplied to each group of wave transmitting elements according to a modified example of the embodiment. [Figure 16]FIG. 16 is a diagram showing a configuration for transmitting waves using a first transmitting array and a second transmitting array. [Figure 17] FIG. 17 is a diagram showing an application example of a window according to the second embodiment. [Figure 18] Fig. 18(a) is a diagram showing a simulation result of a waveform of a transmission wave according to a comparative example of the second embodiment, and Fig. 18(b) is a diagram showing a simulation result of receiving and processing an echo of the transmission wave of Fig. 18(a) by simulating the receiving and processing result. [Figure 19] Fig. 19(a) is a diagram showing a simulation result of a waveform of a transmission wave according to the second embodiment, and Fig. 19(b) is a diagram showing a simulation result of receiving and processing an echo of the transmission wave of Fig. 19(a) by simulating the receiving processing result. [Figure 20] FIG. 20 is a block diagram showing a specific configuration of a target detection device according to the second embodiment. [Figure 21] Fig. 21(a) is a functional block diagram showing a configuration example of a received signal processing unit according to a modified example, and Fig. 21(b) is a functional block diagram showing another configuration example of a received signal processing unit according to a modified example. [Figure 22] Fig. 22(a) is a diagram showing the configurations of a first wave transmitting array and a second wave transmitting array according to another modified example, and Fig. 22(b) is a diagram showing the configurations of a wave transmitting array and a signal switching unit according to yet another modified example. DETAILED DESCRIPTION OF THE INVENTION

[0045] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0046] <Basic configuration> First, the basic configuration of a wave transmitting and receiving system of the target detection device according to this embodiment will be described.

[0047] FIG. 1(a) is a diagram showing the configuration of a wave transmitting system according to a reference example.

[0048] In the configuration of FIG. 1(a), a transmission signal S10 is supplied to a wave transmission source R10, and a transmission wave is transmitted from the wave transmission source R10. For example, the carrier frequency of the transmission signal S10 is set to a constant value f0. When the wave transmission source R10 is moved in a moving direction D10 under this condition, a frequency change due to the Doppler effect occurs in the transmission wave observed at an observation position a predetermined distance away from the wave transmission source R10. In other words, if the distance between the wave transmission source R10 and the observation position is sufficiently large, no frequency change due to the Doppler effect occurs at a front observation position that is in front of the intermediate position of the moving range, and a transmission wave of the same frequency f0 as the transmission signal S10 is generated.

[0049] In contrast, at the upper observation position displaced in the opposite direction to the movement direction relative to the front observation position, the wave source R10 moves away from the observation position, and therefore, due to the Doppler effect, a transmission wave with a frequency f0-fd, which is a frequency reduction from the transmission signal S10, is generated. -fd is the amount of change in frequency relative to the frequency f0 of the transmission signal S10 due to the Doppler effect. Also, at the lower observation position displaced in the same direction as the movement direction relative to the front observation position, the wave source R10 moves in a direction approaching the observation position, and therefore, due to the Doppler effect, a transmission wave with a frequency f0-fd is generated from the transmission signal S10. A transmission wave with an increased frequency of f0+fd is generated, where +fd is the amount of change in frequency relative to the frequency f0 of the transmission signal S10 due to the Doppler effect.

[0050] This frequency change is greater as the displacement of the upper and lower observation positions relative to the front observation position increases. That is, the frequency of the transmitted wave changes from frequency f0 in the positive and negative directions depending on the magnitude of the displacement angle in the depression angle direction (the same direction as the moving direction D10) and elevation angle direction (the opposite direction to the moving direction D10) relative to the front observation position. Therefore, when the reflected wave of the transmitted wave is received by the wave receiving element, the magnitude of the depression angle and elevation angle can be calculated from the frequency components of the received signal output from the wave receiving element. In other words, by extracting a specific frequency component from the received signal, the received signal at a specific angular position in the depression angle direction and elevation angle direction can be obtained. Based on this principle, in this embodiment, the received signal at each angular position in the depression angle direction and elevation angle direction is obtained.

[0051] FIG. 1(b) is a diagram showing an example of a configuration for moving the wave source R10.

[0052] In this configuration example, a transmitting array 10 is used in which a plurality of transmitting elements 10a are arranged in a row. In Fig. 1(b), for convenience, eight transmitting elements 10a are included in the transmitting array 10, but the number of transmitting elements 10a is not limited to this. In Fig. 1(b), for convenience, each transmitting element 10a is numbered in order from the top.

[0053] In this configuration example, the connection of the input terminal of the transmission signal S10 to each wave-transmitting element 10a is switched by a signal switching unit 20. The signal switching unit 20 is configured, for example, by a demultiplexer. Here, the wave-transmitting element 10a to which the transmission signal S10 is supplied is switched to the adjacent wave-transmitting element 10a in order from top to bottom. This causes the transmission source of the transmission wave to move in the direction D10. In this configuration example, as in the case of FIG. 1(a), a change in frequency occurs at each observation position due to the Doppler effect.

[0054] 1(b), for example, when a transmission signal is swept from top to bottom across the multiple transmitting elements 10a arranged in the transmitting array 10 only once to transmit one pulse for one detection unit (one ping), each transmitting element 10a transmits only for the period during which that transmitting element 10a is driven. As a result, with this transmission method, the transmission energy per pulse is low, limiting the maximum detectable distance.

[0055] Therefore, in this embodiment, the transmission energy of one pulse is increased by performing a sweep multiple times, in which the multiple transmitting elements 10a of the transmitting array 10 are continuously driven in one direction, thereby extending the maximum detectable distance.

[0056] FIG. 2 is a diagram schematically showing the state of the sound field when the transmitting array 10 is swept multiple times.

[0057] 2, the x-axis and y-axis are set as the arrangement direction of the transmitting elements 10a in the transmitting array 10 and the front direction of the transmitting array 10. Also, FIG. 2 shows the wavefront of the sound field.

[0058] The plurality of transmitting elements 10a of the transmitting array 10 are driven in sequence continuously from one end (transmitting element at the start position) to the other end (transmitting element at the end position), sweeping the transmitting array 10, and then a similar sweep is repeated without any time gap. This creates a state in which the sound source S moves from the start position to the end position, and then moves from the start position to the end position without any time gap. By repeating this control a predetermined number of times in one detection unit, the pulse transmission time is extended and the transmission energy is increased. In FIG. 2, for convenience, the number of times is shown as one detection unit. The sound field is shown when four sweeps are performed in the output unit.

[0059] As shown in Figure 2, the transmission packets from each sweep are time-compressed according to the in-plane direction θ of the xy plane (hereinafter referred to as "orientation θ") relative to the front direction, and the carrier frequency is changed. Furthermore, in accordance with this time compression, gaps (sections of zero sound pressure) corresponding to the orientation θ are generated between the transmission packets. In Figure 2, transmission packets in the front direction (y-axis direction) and the sweep direction (x-axis direction) of the transmit array 10 are shown along the y-axis and x-axis, respectively, with the transmission packets in the orientation indicated by the arrows at the tips of the arrows. The τ attached to each transmission packet is the period during which the sound source S moves from the start position to the end position, i.e., the period of one sweep for the transmit array 10.

[0060] As shown in Figure 2, in the front direction (y-axis direction), there is no Doppler effect, so the waveform of the transmission packet is maintained similar to that of the transmission signal. Therefore, no gaps occur between transmission packets in the front direction. In contrast, in the sweep direction (x-axis direction) of the transmitting array 10, the Doppler effect significantly compresses the waveform of the transmission packet, resulting in large gaps between the transmission packets. Furthermore, in the direction of the arrow, the Doppler effect is smaller than in the x-axis direction, so compression of the waveform of the transmission packet is smaller, and gaps between the transmission packets are suppressed.

[0061] In this way, the state of compression and gaps in the waveform differs for each direction, so the frequency spectrum of the sound wave differs for each direction. That is, the spectral intensity is low in directions where gaps cause phase discontinuities, and high in directions where gaps do not cause phase discontinuities. Specifically, in directions where the gaps are an integer multiple of the wavelength, no phase discontinuities occur, so the spectral intensity is high.

[0062] Here, the number of waves sent in the front direction (θ=0) in one sweep is f0·τ, The packets are repeated over a sweep period τ, and a CW wave with a long pulse width and connected phase is transmitted in the forward direction. On the other hand, in directions other than the forward direction, discontinuities in phase occur due to gaps depending on the direction, but the initial phase between packets is maintained in the direction of the carrier frequency that satisfies the following relational expression:

[0063]

number

[0064] If the gap period, i.e., the phase stop period, is an integer multiple of the carrier period in that direction, the initial phase between packets will be the same, and the influence of the gap will be minor. This condition can be expressed by the following equation from the above equation (1):

[0065]

number

[0066] From equation (2), it can be seen that a continuous phase, that is, a direction in which the spectrum becomes sharper, is formed for each 1 / τ.

[0067] Next, we consider beam spacing (the interval between the formed transmission beams).

[0068] As mentioned above, the direction in which the transmit beam is formed is the direction in which the initial phase is connected, and the direction in which the carrier frequency satisfies equation (2). The direction θn is related to other variables by the following equation:

[0069] The gap time in the θ direction is calculated using the following formula:

[0070]

number

[0071] Here, V is the moving speed of the sound source S, c is the speed of sound, and r(θ) is the compression ratio of the transmitted wave propagating in the θ direction.

[0072] The direction in which the time of this gap is an integer multiple of the period of the carrier frequency in the θ direction is θn, and θn is defined by the following equation.

[0073]

number

[0074] Therefore, θn can be calculated using the following formula:

[0075]

number

[0076] Therefore, a transmission beam is formed in the direction θn calculated by the above equation (5). Therefore, by extracting the carrier frequency in the direction θn, it is possible to extract the received signal for each transmission beam.

[0077] FIG. 3 is a diagram showing a simulation result obtained by simulation of a surface (hereinafter referred to as "equal frequency surface") on which the amount of frequency variation due to the Doppler effect is the same when the sound source S is moved in one direction as described above.

[0078] In FIG. 3, the unit of each axis is meter. The transmitting array 10 is arranged so as to extend in the X-axis direction at the intermediate position in the Y-axis direction (the position where the distance is zero). The transmission wave is transmitted in the Z-axis direction from the intermediate position in the Y-axis direction. That is, the direction from the intermediate position in the Y-axis direction toward the Z-axis direction is the front direction.

[0079] In FIG. 3, equal frequency surfaces EP1 to EP5 in the range above the front direction are shown. The equal frequency surfaces EP1, EP2, EP3, EP4, and EP5 are surfaces of frequencies of f0 - fd1, f0 - fd2, f0 - fd3, f0 - fd4, and f0 - fd5, respectively. f0 is the frequency in the front direction and is equal to the frequency of the transmission signal supplied to the transmitting element. There is a relationship of fd1 < fd2 < fd3 < fd4 < fd5 for fd1 to fd5.

[0080] For the sake of convenience, five equal frequency surfaces EP1 to EP5 are shown in FIG. 3, but there are also a large number of equal frequency surfaces between these equal frequency surfaces EP1 to EP5. For example, the frequency in the gap between the equal frequency surfaces EP1 and EP2 continuously transitions from f0 - fd1 to f0 - fd2. By folding the equal frequency surfaces EP1 to EP5 in FIG. 3 symmetrically with respect to the Y-Z plane, an equal frequency surface in the range below the front direction is formed.

[0081] By using the equal frequency surface corresponding to the transmission beam formed by the above formula (5) among the equal frequency surfaces formed in this way for target detection, the accuracy of target detection can be improved.

[0082] FIG. 4 is a diagram schematically showing a configuration example of a transmission and reception system.

[0083] In this configuration example, in addition to the configuration of the transmitting array 10 (transmitting system) shown in Fig. 1(a), a receiving array 30 having a plurality of receiving elements 30a is arranged as a receiving system configuration. The transmitting array 10 is arranged so that the transmitting elements 10a are aligned along the X-axis. The receiving array 30 is arranged directly above the transmitting array 10. In this configuration example, the arrangement direction of the receiving elements 30a and the arrangement direction of the transmitting elements 10a are perpendicular to each other.

[0084] By driving the wave transmitting elements 10a in the wave transmitting array 10 in order in the vertical direction, a transmission beam TB1 is formed in front of the wave transmitting array 10 (positive direction of the Z axis).

[0085] That is, when a transmission signal S10 is supplied to the transmitting element 10a, the transmitting element 10a transmits a transmission wave with a relatively wide directivity. When the transmission signal S10 is supplied for one sweep to the transmitting elements 10a in the transmitting array 10 in order from top to bottom, the region where all the transmission waves transmitted from the transmitting elements 10a overlap is the region where the total transmission beam TB1 is formed. As described with reference to FIG. 3, many equal-frequency surfaces are generated in this formation region.

[0086] By performing phase control (beamforming) on ​​the received signals output from each receiving element 30a, a narrow receiving beam RB1 is formed in the circumferential direction centered on the X-axis. As a result, the received signals in the area where the receiving beam RB1 and the transmitting beam TB1 intersect are extracted. By rotating the receiving beam RB1 in the θ1 direction centered on the X-axis using the phase control, the received signals at each rotating position are extracted. The horizontal arrival direction of the reflected wave, which is the transmitted wave reflected by the target, can be determined by the rotating position of the receiving beam RB1. Furthermore, the frequency of the received signal can determine the iso-frequency surface (see Figure 3) on which the reflected wave occurs.

[0087] Therefore, by extracting received signals of frequencies corresponding to each iso-frequency plane from the received signals extracted by the receiving beam RB1 and plotting the intensity of the extracted received signals on each iso-frequency plane on each iso-frequency plane, the distribution of intensity data of the received signals in the range where the receiving beam RB1 and the transmitting beam TB1 intersect can be obtained. Then, by rotating the receiving beam RB1 within the horizontal detection range and obtaining the distribution of intensity data at each rotation position, it is possible to obtain intensity data (volume data) distributed three-dimensionally across the entire detection range in the horizontal and vertical directions. By imaging this intensity data (volume data), it is possible to obtain an image showing the state of the target in the detection range.

[0088] In the above configuration, a frequency-modulated signal such as a chirp signal can be used as the transmission signal. In this case, the distance resolution of target detection can be improved by applying a well-known pulse compression technique using a matched filter to the received signal.

[0089] Furthermore, as described above, when the transmit array 10 is repeatedly swept multiple times to generate transmit pulses, a window may be applied to each sweep in order to suppress side lobes that occur in the sweep direction (azimuth direction).

[0090] FIG. 5 is a diagram showing an example of application of a window for side lobe suppression.

[0091] FIG. 5 shows an example of window application when the transmit array 10 is swept twice to generate a transmit pulse. T11 is the first sweep period, and T12 is the second sweep period. Numbers 1 to 8 in the upper part of FIG. 5 indicate the numbers of the transmit elements 10a, as in FIG. 1(b). The waveforms shown next to each number schematically show the waveform of window W1 for each transmit element 10a, which is applied during the period when the transmit element 10a with that number is driven by the transmit signal. The waveforms in the middle of FIG. 5 are the waveforms of windows W11 and W12 set for each sweep, and the waveform in the lower part of FIG. 5 is the waveform of window W0 applied to the entire transmit pulse.

[0092] The waveform of each window indicates the weighting of the transmission signal. The higher the height of the window waveform, the higher the weighting. The transmission signal is amplified with a weighting that is a superposition of the weightings of all the windows. That is, a transmission signal (e.g., a chirp signal) whose frequency is modulated from the start of the sweep period T11 (the start time of the transmission pulse) to the end of the sweep period T12 (the end time of the transmission pulse) is amplified with a weighting that is a superposition of the weightings of all the windows. The transmission signal amplified by each window in this way is supplied to each transmitting element 10a at the switching timing of the signal switching unit 20.

[0093] Side lobes are suppressed by setting windows on the transmission signal as shown in Figure 5. The upper window W1 and the middle windows W11 and W12 suppress side lobes that occur in the sweep direction, and the lower window W0 suppresses side lobes in the distance direction (time axis direction).

[0094] However, when a window is applied to the transmission signal in this manner, if reception processing is performed using an ideal matched filter for the transmission signal for each direction of the sweep direction (each of the above-mentioned equal frequency planes), ripples will occur in the transmission wave due to the influence of the windows W11 and W12 for each sweep.

[0095] Figure 6(a) shows the results of a simulation of the waveform of a transmitted wave when a window is set as shown in Figure 5, and Figure 6(b) shows the results of receiving and processing the echo of this transmitted wave, obtained by simulation. In Figure 6(b), it is assumed that the target is located at an azimuth of 0 degrees in the sweep direction (front direction). Furthermore, these simulations assume that the sweep is repeated five times to generate a transmitted pulse for one detection unit.

[0096] In Figure 6(a), the horizontal axis represents the distance in the forward / backward direction from the central waveform P0, and the vertical axis represents the intensity of the envelope of the transmitted wave. In Figure 6(b), the horizontal axis represents the distance in the forward / backward direction from the normal distance position of the target, and the vertical axis represents the angle of the sweep direction with respect to the front direction. Note that the graph in Figure 6(a) is normalized with the peak of the central waveform P0 set to 1. Also, although the original image in Figure 6(b) was a color image, this color image is shown in grayscale here for convenience.

[0097] When the window is set using the method of FIG. 5, multiple ripples R1 occur before and after the central waveform P0, as shown in FIG. 6(a). Therefore, as shown in FIG. 6(b), the reception processing result has a high-intensity region (the region indicated by the dashed ellipse) at the distance position D1 corresponding to the ripple R1 as well as at the normal distance position D0 of the target. In this case, the detected image of the target will display an image of the target not only at the normal distance position D0 of the target but also at the distance position D1 corresponding to the ripple R1. Therefore, the target position is not clearly displayed in the detected image, and multiple target images are displayed overlapping near the normal position of the target.

[0098] To solve this problem, in this embodiment, the next sweep is started between the start and end of one sweep, which prevents a deep valley from occurring at the boundary between the window W11 set for one sweep and the window W12 set for the next sweep, thereby preventing the ripple R1 shown in FIG.

[0099] FIG. 7 is a diagram showing an example of application of the window in this case.

[0100] 7, a sweep in a sweep period T21 is set between a sweep in a sweep period T11 and a sweep in a sweep period T12. The sweep in the sweep period T21 starts at the midpoint of the sweep period T11. The sweep in the following sweep period T12 starts at the midpoint of the sweep period T21. A window W21, indicated by a dashed line in the middle, is also set in the sweep period T21.

[0101] In sweep period T21, the upper, middle, and lower windows W1, W21, and W0 corresponding to sweep period T21 are applied. That is, the upper window W1 applied in sweep period T21 is eight windows arranged in a straight line in a diagonal direction. The middle window W21 applied in sweep period T21 is the same as windows W11 and W12, and the lower window W0 applied in sweep period T21 is a portion obtained by cutting out the range of sweep period T21 from the lower window W0. The windows applied in sweep periods T11 and T12 are the same as those in FIG. 5.

[0102] 7, a transmission signal (e.g., a chirp signal) whose frequency is modulated from the start of sweep period T11 (start time of the transmission pulse) to the end of sweep period T12 (end time of the transmission pulse) is amplified with weighting that combines the weightings of all windows for each sweep period T11, T12, and T21. The transmission signal weighted by each window in this way is supplied to each wave transmitting element 10a during the drive period of each wave transmitting element 10a in each sweep period.

[0103] When the windows are set as in Fig. 7, the side lobes are suppressed, as in Fig. 5. In this case as well, the upper window W1 and the middle windows W11, W12, and W21 suppress the side lobes occurring in the sweep direction, and the lower window W0 suppresses the side lobes in the distance direction.

[0104] 7, the window W21 in the middle of the sweep period T21 is interpolated between the window W11 in the middle of the sweep period T11 and the window W12 in the middle of the sweep period T12, thereby preventing a deep valley from occurring at the boundary between these windows, thereby preventing the ripple R1 shown in FIG. 6(b).

[0105] 8(a) and 8(b) are diagrams showing the simulation results when the windows are set as shown in FIG.

[0106] Fig. 8(a) shows the simulation results of the transmission waveform, similar to Fig. 6(a), and Fig. 8(b) shows the results of the simulation of the transmission waveform. ) shows the simulation results of the reception processing results, as in Figure 6(b). In the simulation of Figure 8(b), as in Figure 6(b), it is assumed that the target is located at an azimuth of 0 degrees in the sweep direction (front direction). Also, in these simulations, it is assumed that the sweep is repeated five times to generate one transmission pulse.

[0107] As shown in FIG. 8(a), when the window is set using the method of FIG. 7, the ripple R1 as shown in FIG. 6(a) does not occur, and the transmitted waveform is a single-peak waveform P0. Therefore, as shown in FIG. 8(b), the reception processing result does not have high-intensity regions clearly separated in the distance direction as shown in FIG. 6(b), and a high-intensity region (the region indicated by the dashed ellipse) occurs near the normal distance position D0 of the target. Therefore, in the detected image of the target, multiple target images are prevented from overlapping near the normal distance position of the target, and an image showing the target is displayed near the normal distance. Therefore, the position of the target can be displayed more clearly in the detected image, and the accuracy of the image showing the target can be improved.

[0108] FIG. 9 is a diagram showing the configuration of the signal switching unit when the next sweep is started in the middle of one sweep, as shown in FIG.

[0109] When starting the next sweep in the middle of one sweep, two signal switching units, a first signal switching unit 21 and a second signal switching unit 22, are used, as shown in FIG. 9. The first signal switching unit 21 and the second signal switching unit 22 are each configured, for example, by a demultiplexer. For example, the first signal switching unit 21 is used for odd-numbered sweeps, and the second signal switching unit 22 is used for even-numbered sweeps. In this case, a first transmission signal S11 is supplied to terminal T1, and a second transmission signal S11 is supplied to terminal T2. As described above, each transmission signal is a transmission signal (e.g., a chirp signal) whose frequency is modulated from the start point of the transmission pulse to the end point of the transmission pulse, and is then weighted for each sweep period by each window in FIG. 7.

[0110] For example, at the timing when the first signal switching unit 21 switches the supply destination of the first transmission signal S11 from the fourth wave transmitting element 10a from the top to the fifth wave transmitting element 10a from the top, the second signal switching unit 22 connects the terminal T2 to the first wave transmitting element 10a from the top. As a result, sweeping of the sweep period T21 starts in the middle of the sweep period T11, as shown in Fig. 7. This prevents the ripple R1 from occurring in the transmission waveform, as described above.

[0111] When the sweep periods are overlapped by half as shown in Figure 7, the sweep repetition period is halved compared to Figure 5. This allows the chirp bandwidth to be doubled, improving the distance resolution for target detection.

[0112] <Specific configuration> FIG. 10 is a block diagram showing a specific configuration of the target detection device 1. As shown in FIG.

[0113] The target detection device 1 includes the above-described wave transmitting array 10 as a configuration of the wave transmitting system. The wave transmitting array 10 has the same configuration as that shown in Fig. 9. The target detection device 1 includes a first transmission signal generator 111, a second transmission signal generator 121, a first transmission amplifier 112, a second transmission amplifier 122, a first signal switcher 113, and a second signal switcher 123 as a configuration for supplying transmission signals to each wave transmitting element 10a of the wave transmitting array 10.

[0114] The first transmission signal generating unit 111 generates the first transmission signal S11 in accordance with control from the control unit 101. As described above, the first transmission signal S11 is a signal used for odd-numbered sweeps, and is a signal obtained by weighting one pulse of a frequency-modulated transmission signal by each window applied to the odd-numbered sweep period.

[0115] The second transmission signal generating unit 121 generates the second transmission signal S12 in accordance with control from the control unit 101. As described above, the second transmission signal S12 is a signal used for even-numbered sweeps, and is a signal obtained by weighting one pulse of a frequency-modulated transmission signal by each window applied to the even-numbered sweep period.

[0116] The first transmission amplifier 112 amplifies the first transmission signal S11 input from the first transmission signal generator 111 in response to control from the controller 101. The first signal switcher 113 sequentially supplies the first transmission signal S11 to the plurality of wave transmitting elements 10a included in the wave transmitting array 10 in response to control from the controller 101. The first signal switcher 113 has the same configuration as the first signal switcher 21 in Fig. 9. The first signal switcher 113 is configured by, for example, a demultiplexer.

[0117] The second transmission amplifier 122 amplifies the second transmission signal S12 input from the second transmission signal generation unit 121 in accordance with control from the control unit 101. The second signal switching unit 123 sequentially supplies the second transmission signal S12 to the plurality of wave transmitting elements 10a included in the wave transmitting array 10 in accordance with control from the control unit 101. The second signal switching unit 123 has the same configuration as the second signal switching unit 22 in Fig. 9. The second signal switching unit 123 is formed, for example, by a demultiplexer.

[0118] The control unit 101 includes an arithmetic processing circuit such as a CPU (Central Processing Unit), a storage medium such as a ROM (Read Only Memory), a RAM (Random Access Memory), or a hard disk. The control unit 101 includes an integrated circuit such as an FPGA (Field-Programmable Gate Array). It may be configured as follows.

[0119] As described above, the control unit 101 controls the first transmission signal generation unit 111 and the second transmission signal generation unit 121, the first transmission amplifier 112 and the second transmission amplifier 122, and the first signal switching unit 113 and the second signal switching unit 123 so that sweeping of the wave transmitting array 10 with the second transmission signal S12 starts before the end of the sweep period of the wave transmitting array 10 with the first transmission signal S11. This causes the sweep period of the wave transmitting array 10 with the first transmission signal S11 and the sweep period of the wave transmitting array 10 with the second transmission signal S12 to partially overlap. For example, the control unit 101 performs transmission control so that sweeping of the wave transmitting array 10 with the second transmission signal S12 starts midway through the sweep period of the wave transmitting array 10 with the first transmission signal S11.

[0120] By this transmission control, an equal frequency surface with the same amount of frequency fluctuation due to the Doppler effect is formed in the transmission beam TB1. In addition, in this control, the control unit 101 applies each window shown in Fig. 7 to the first transmission signal S11 and the second transmission signal S12. This suppresses the side lobes and ripples as described above.

[0121] The target detection device 1 includes the above-mentioned wave receiving array 30 as a configuration of the wave receiving system. The wave receiving array 30 has the same configuration as that shown in Fig. 4. The wave receiving array 30 has k wave receiving elements 30a arranged therein. A received signal is output from each wave receiving element 30a to a channel CH1 to CHk corresponding to each wave receiving element 30a.

[0122] The target detection device 1 is configured to process the received signals output from each receiving element 30a of the receiving array 30 to generate a detected image, and includes a plurality of receiving processing units 201, a plurality of AD conversion units 202, a received signal processing unit 203, and a video signal processing unit 204.

[0123] The plurality of reception processing units 201 are connected to the channels CH1 to CHk, respectively. The reception processing unit 201 performs processes on the input reception signal, such as removing unnecessary bands, amplifying the reception signal to a level suitable for AD conversion, and removing signal components in a band equal to or greater than half the sampling period of the AD conversion. A plurality of AD conversion units 202 are associated with the plurality of reception processing units 201, respectively. Each AD conversion unit 202 converts the analog reception signal input from the corresponding reception processing unit 201 into a digital signal at a predetermined sampling period.

[0124] The received signal processing unit 203 processes the received signals of channels CH1 to CHk input from the plurality of AD conversion units 202, and calculates intensity data (volume data) of the received signals distributed three-dimensionally in the detection range. The received signal processing unit 203, together with the control unit 101, may be configured as a single integrated circuit (such as an FPGA).

[0125] The video signal processing unit 204 processes the intensity data (volume data) input from the received signal processing unit 203 to generate image data for imaging the state of the target in the detection range. The video signal processing unit 204 is configured by, for example, a CPU. The display unit 205 is configured by a monitor or the like, and displays a detection image corresponding to the image data input from the video signal processing unit 204.

[0126] FIG. 11( a ) is a functional block diagram showing an example of the configuration of the received signal processing unit 203 .

[0127] The received signal processing unit 203 includes an arithmetic processing circuit and a storage medium. The received signal processing unit 203 executes the functions of the functional blocks shown in Fig. 11(a) by a program stored in the storage medium. Some of the functions shown in Fig. 11(a) may be realized by hardware using logic circuits instead of software.

[0128] The received signal processing unit 203 includes a plurality of digital filters 211 , a buffer 212 , a plurality of matched filters 213 , and a plurality of beam synthesis units 214 .

[0129] The plurality of digital filters 211 are provided corresponding to the plurality of AD conversion units 202 in Fig. 10. The digital filters 211 are filters with a steeper filter function than the reception processing unit 201 in Fig. 10, and remove signals in unnecessary bands from the received signal.

[0130] The buffer 212 temporarily holds the received signals of channels CH1 to CHk output from the multiple digital filters 211. The buffer 212 holds, in time series, the received signals of a unit pulse period that sweeps the multiple transmitting elements 10a of the transmitting array 10 multiple times. The buffer 212 sequentially supplies the received signals of a unit pulse period to the multiple matched filters 213, respectively. After supplying the received signals of a unit pulse period to the multiple matched filters 213, the buffer 212 erases the received signals of that unit pulse period.

[0131] The plurality of matched filters 213 pulse-compress the received signals of the input channels CH1 to CHk for each unit pulse period for each iso-frequency plane. A matched filter 213 is provided for each iso-frequency plane. That is, the number of iso-frequency planes is defined as many as the number of matched filters 213. The more matched filters 213 are used, the higher the resolution of the received signals in the overlapping direction of the iso-frequency planes. Each matched filter 213 is set with parameter values ​​corresponding to the ideal transmission waveform of the corresponding iso-frequency plane. It is preferable that the iso-frequency plane associated with each matched filter 213 is an iso-frequency plane that satisfies the above formula (5). The matched filters 213 pulse-compress the received signals of the channels CH1 to CHk for each unit pulse period using the ideal waveform set for the matched filters 213, generating signals (hereinafter referred to as "iso-frequency received signals") and supplying the signals to the beam synthesis unit 214.

[0132] The multiple beam combining units 214 are provided corresponding to the multiple matched filters 213, respectively. The beam combining unit 214 forms a reception beam RB1 by beamforming based on phase control or delay control, and separates the equal-frequency reception signals in the θ1 direction in FIG. 4 with a predetermined resolution. This allows for the acquisition of equal-frequency reception signals in the region where the reception beam RB1 intersects with the equal-frequency plane defined by the matched filter 213. That is, the top-most beam combining unit 214 acquires equal-frequency reception signals in the intersection region where the first equal-frequency plane S1 intersects with the reception beam RB1 in each azimuth in the direction parallel to the horizontal plane (the θ1 direction in FIG. 4).

[0133] The intensity of the obtained iso-frequency received signals varies on the time axis depending on the strength of the reflected waves from the intersection region. This time axis corresponds to the distance from the receiving array 30 in the intersection region. Therefore, by mapping each intensity on the time axis to a corresponding distance position from the receiving array 30 in the intersection region, the distribution of intensity data in the intersection region can be obtained. In this way, by integrating the distribution of intensity data for each direction output from each beam combining unit 214, volume data in which intensity data is distributed three-dimensionally in the detection range can be obtained.

[0134] FIG. 11(b) is a functional block diagram showing another example of the configuration of the received signal processing unit 203.

[0135] In this configuration example, the received signal of each channel is frequency converted by an FFT (Fast Fourier Transform) 221, and then pulse compressed in the frequency domain for each channel by a matched filter 222. The matched filter 222 performs pulse compression for each iso-frequency plane, as in the case of FIG. 11(a). Thereafter, the signal of each channel after pulse compression is transformed into the time domain by an IFFT (Inverse Fourier Transform) 223. As a result, An iso-frequency received signal is generated for each iso-frequency plane. The generated iso-frequency received signal for each iso-frequency plane is output to the corresponding beam synthesis unit 214. The subsequent processing is the same as in the case of FIG. 11(a).

[0136] 11(a), this configuration also allows volume data in which intensity data is distributed three-dimensionally in the detection range to be acquired by integrating the distribution of intensity data for each direction output from each beam synthesis unit 214. In the configuration example of FIG. 11(b), pulse compression is performed by the matched filter 222 in the frequency domain, so the amount of calculation required for pulse compression can be reduced compared to the configuration example of FIG. 11(a). Furthermore, in the configuration example of FIG. 11(b), the matched filter for acquiring iso-frequency received signals can be set more precisely than in the configuration example of FIG. 11(a). Therefore, the number of iso-frequency planes to be processed can be increased, and the resolution of iso-frequency received signals in the stacking direction of the iso-frequency planes can be improved.

[0137] Figures 12(a) and (b) are flowcharts showing the wave transmission process performed by the control unit 101 in Figure 10. This process is executed continuously during the detection operation, and is ended when the detection operation ends.

[0138] 12(a) shows the wave transmission process for odd-numbered sweeps using the first signal switching unit 113, and FIG. 12(b) shows the wave transmission process for even-numbered sweeps using the second signal switching unit 123.

[0139] 12(a), when it is time to start transmitting one pulse of wave (S111: YES), the control unit 101 executes a first sweep using the first signal switching unit 113 (S112). Specifically, the control unit 101 causes the first transmission signal generating unit 111 to generate the first transmission signal S11, and controls the first signal switching unit 113 to switch the wave transmitting element 10a to which the first transmission signal S11 is supplied, in order from the first wave transmitting element 10a to the last wave transmitting element 10a. When the switching has been completed up to the last wave transmitting element 10a in this way (S113: YES), The control unit 101 determines whether or not the control to be performed for transmitting one pulse has been completed, that is, whether or not the odd-numbered sweeps have been repeated the number of times corresponding to one pulse (S114).

[0140] If the determination in step S114 is NO, the control unit 101 returns the sweep position to the leading wave transmitting element 10a (S115) and repeats the first sweep (S112). In this way, when the odd-numbered sweep is repeated the set number of times (S114: YES), the control unit 101 ends the odd-numbered sweep control using the first signal switching unit 113.

[0141] 12(b), when the timing reaches a half cycle of the sweep period after the start of the first sweep in FIG. 12(a) (S121: YES), the control unit 101 executes a second sweep using the second signal switching unit 123 (S122). Specifically, the control unit 101 causes the second transmission signal generating unit 121 to generate the second transmission signal S12 and controls the second signal switching unit 123 to switch the wave transmitting elements 10a to which the second transmission signal S12 is supplied, in order from the first wave transmitting element 10a to the last wave transmitting element 10a. When the switching has been completed up to the last wave transmitting element 10a (S123: YES), the control unit 101 determines whether or not the control to be performed for transmitting waves for one pulse has been completed, i.e., whether or not the even-numbered sweeps have been repeated the number of times corresponding to one pulse (S124).

[0142] If the determination in step S124 is NO, the control unit 101 returns the sweep position to the leading wave transmitting element 10a (S125) and repeats the second sweep (S122). In this way, when the even-numbered sweep has been repeated the set number of times (S124: YES), the control unit 101 ends the even-numbered sweep control using the second signal switching unit 123.

[0143] By the control shown in FIGS. 12(a) and 12(b), a transmission beam TB1 having a number of equal frequency surfaces is formed.

[0144] FIG. 13 is a flowchart showing the process of processing the received signal and displaying the detected image.

[0145] A received signal for a unit pulse period is supplied from the buffer 212 to each of the plurality of matched filters 213 (S201). Each matched filter 213 generates a signal (constant frequency received signal) by pulse-compressing the received signal of each input channel using an ideal waveform of the constant frequency plane set for itself, and supplies the signal to the corresponding beam synthesis unit 214 (S202).

[0146] The beam combining unit 214 extracts signal components in each direction in the horizontal direction (θ1 direction) from the input iso-frequency received signals by beamforming (S203). This results in a distribution of intensity data in which the intensity data of the received signals is mapped onto each iso-frequency plane. The received signal processing unit 203 integrates the intensity data from all the beam combining units 214 to form volume data in which the intensity data is distributed three-dimensionally in the detection range (S204). The received signal processing unit 203 supplies the volume data to the video signal processing unit 204.

[0147] The video signal processing unit 204 processes the volume data to generate image data for displaying the detection status of the target in the detection range, and supplies the generated image data to the display unit 205 (S205). The display unit 205 displays an image based on the input image data (S206). This displays the detection status of the target in the detection range. The control unit 101 repeatedly executes the processes of steps S201 to S206 every time a transmission pulse is transmitted by the processes of FIGS. 12(a) and 12(b).

[0148] FIG. 14 is a diagram schematically showing a configuration in which the above-described target detection device 1 is used as a sonar for detecting targets in water.

[0149] A transducer 300 is installed on the bottom of the ship 2. The transducer 300 includes a transmitting array 10 and a receiving array 30. The transmitting array 10 transmits transmission waves into the water using the above-described process. Here, sound waves (e.g., ultrasonic waves) are transmitted as the transmission waves. As a result, a transmission beam TB1 is formed in which equal frequency planes overlap in the angular direction within a range of angle θ2 parallel to the vertical plane.

[0150] 10, the components other than the transmitting array 10, the receiving array 30, and the display unit 205 are mounted on a control device installed in the wheelhouse 2a of the ship 2. The display unit 205 is installed in the wheelhouse 2a separately from the control device. The display unit 205 may also be integrated into the control device.

[0151] With this configuration, a detected image showing the state of the water bottom 3 and the school of fish 4 is displayed on the display unit 205. This allows the user to understand the underwater situation. Four transducers 300 facing forward, backward, left, and right may be installed on the bottom of the boat. In this case, the configuration of the wave transmitting system and wave receiving system shown in FIG. 10 is prepared for each transducer 300. This allows the detected image of the entire periphery of the boat to be displayed on the display unit 205.

[0152] Furthermore, when the above-described target detection device 1 is used as a radar for detecting targets in the air, a transducer 400 is installed, for example, on the side wall of the wheelhouse 2a. The transducer 400 includes a transmitting array 10 and a receiving array 30. The transmitting array 10 transmits transmission waves into the air through the above-described processing. Here, radio waves are transmitted as the transmission waves. The circuit configuration is installed in the wheelhouse 2a, similar to the case of sonar.

[0153] According to this configuration, a detected image showing the situation of obstacles, flocks of birds, etc. is displayed on the display unit 205. This allows the user to understand the situation in the air. Note that the transducer 400 may be installed on each of the front, rear, left, and right sides of the wheelhouse 2a. In this case, the configuration of the transmitting system and receiving system shown in FIG. 10 is prepared for each transducer 400. This allows the detected image of the space all around the ship 2 to be displayed on the display unit 205.

[0154] <Effects of the embodiment> According to the embodiment, the following effects can be achieved.

[0155] 9, the transmitting element 10a to which the first transmitting signal S11 is supplied is switched from element n to element n+1 in the transmitting array 10 by the first signal switching unit 21, whereby the transmitting source of the transmitting wave moves in the arrangement direction of the transmitting elements 10a. As a result, the frequency of the transmitting beam TB1 changes in the moving direction of the transmitting source due to the Doppler effect, and multiple iso-frequency planes are formed in the transmitting beam TB1. Therefore, by extracting signals corresponding to each iso-frequency plane from the receiving signal generated by the receiving element 30a, it is possible to obtain receiving signals (iso-frequency receiving signals) based on the reflected waves from each iso-frequency plane.

[0156] At this time, the second signal switching unit 22 in Fig. 9 switches the transmitting element 10a to which the second transmission signal S12 is supplied from element m to element m+1 in the transmitting array 10. As a result, as shown in Fig. 7, the sweep of the transmitting array 10 by the first signal switching unit 21 and the sweep of the transmitting array 10 by the second signal switching unit 22 partially overlap, which makes it possible to suppress ripples in the transmitting waveform and the receiving processing result (constant frequency received signal) as shown in Figs. 8(a) and 8(b). This improves the target detection accuracy.

[0157] As described above, according to this embodiment, targets in each equal frequency plane can be accurately detected by a simple configuration in which the transmitting element 10a to which the first transmission signal S11 and the second transmission signal S12 are supplied is switched within the transmitting array 10.

[0158] In this embodiment, element n+1 is adjacent to element n, and element m+1 is adjacent to element m in the wave transmitting array 10. The wave transmitting element 10a to which the first transmission signal S11 is supplied is switched from element n+1 to element n+2, which is adjacent to element n+1, and the wave transmitting element 10a to which the second transmission signal S12 is supplied is switched from element m+1 to element m+2, which is adjacent to element m+1. In this way, the first transmission signal S11 and the second transmission signal S12 are supplied to adjacent wave transmitting elements 10a in sequence, allowing the wave transmitting source of the transmission wave to be moved finely in the direction in which the wave transmitting elements 10a are arranged. This allows for smooth frequency changes due to the Doppler effect.

[0159] In this embodiment, when the transmitting array 10 includes P transmitting elements 10a, if P is an even number, (P / 2)-1 transmitting elements 10a are preferably included between element n and element m. If P is an odd number, (P-1) / 2 or {(P-1) / 2}-1 transmitting elements 10a are preferably included between element n and element m. By setting element n and element m in this manner, the second signal switching unit 22 starts sweeping the transmitting array 10 near the middle of the period in which the first signal switching unit 21 sweeps the transmitting array 10. This allows each sweep to overlap by 1 / 2 period, more effectively suppressing ripples in the transmitted waves and the received signal. Furthermore, since the sweep repetition period is halved compared to the case of FIG. 5, the chirp bandwidth can be doubled, thereby improving the distance resolution of target detection.

[0160] Furthermore, if the transmitting array 10 includes P transmitting elements 10a, numbered from transmitting element 1 to transmitting element P, and element n+1 corresponds to a transmitting element 10a that exceeds transmitting element P, the first signal switching unit 21 switches the transmitting element 10a to which the first transmission signal S11 is supplied from transmitting element P to transmitting element 1, and if element m+1 corresponds to a transmitting element 10a that exceeds transmitting element P, the second signal switching unit 22 switches the transmitting element 10a to which the second transmission signal S12 is supplied from transmitting element P to transmitting element 1. This causes the transmitting array 10 to be repeatedly swept with the first transmission signal S11 and the second transmission signal S12. This increases the transmission energy per pulse, thereby widening the detectable distance range.

[0161] In the above embodiment, the first transmission signal S11 is a frequency-modulated signal, and the second transmission signal S12 is a frequency-modulated signal. As a result, by performing reception processing using a matched filter 213 as shown in Figures 11(a) and 11(b), it is possible to improve the distance resolution of target detection.

[0162] In this embodiment, element n is supplied with a first portion of the first transmission signal S11, element n+1 is supplied with a second portion of the first transmission signal S11 that is different from the first portion, element m is supplied with a first portion of the second transmission signal S12, and element m+1 is supplied with a second portion of the second transmission signal S12 that is different from the first portion of the second transmission signal S12. In the above embodiment, the first transmission signal S11 and the second transmission signal S12 are frequency-modulated signals such as chirp signals, so that the portions of the signal waveforms supplied to element n and element n+1 are different, and the portions of the signal waveforms supplied to element m and element m+1 are different.

[0163] 11(a) and 11(b), the received signal processing unit 203 has a configuration (matched filters 213, 222) that extracts, based on the frequency components of the received signal, a received signal (constant frequency received signal) based on a reflected wave from an iso-frequency plane corresponding to the frequency. This makes it possible to smoothly acquire the constant frequency received signal for each iso-frequency plane.

[0164] 4, the receiving beam RB1 generated based on the received signal from each receiving element 30a is configured to intersect with the transmitting beam TB1 generated by the transmitting array 10. As a result, the receiving beam RB1 and the transmitting beam TB1 (equal frequency plane) In the area where these lines intersect, the distribution of intensity data can be calculated based on the intensity of the reflected waves. Therefore, by using beamforming to change the direction of the receiving beam within the detection range, it is possible to generate intensity data that is distributed three-dimensionally within the detection range.

[0165] <Example of change> In the above embodiment, the first transmission signal S11 and the second transmission signal S12 are each supplied to one transmitting element 10a, but multiple transmitting elements 10a may be grouped and the first transmission signal S11 and the second transmission signal S12 may be supplied to each group.

[0166] FIG. 15 is a diagram showing a configuration in which a first transmission signal S11 and a second transmission signal S12 are supplied to each group of wave transmitting elements 10a.

[0167] In the configuration example of Fig. 15, each group includes two wave transmitting elements 10a. The top two wave transmitting elements 10a form group G1, and the second and third wave transmitting elements 10a from the top form group G2. The two wave transmitting elements 10a in adjacent groups are offset by one in the vertical direction. In the configuration example of Fig. 15, seven groups are configured, from group G1 to group G7.

[0168] The first signal switching unit 21 and the second signal switching unit 22 each have one input terminal and two output terminals, and the two output terminals are simultaneously connected to the wave transmitting elements 10a of each group. Therefore, the first transmission signal S11 or the second transmission signal S12 is simultaneously supplied to the wave transmitting elements 10a of each group. The first signal switching unit 21 switches the group to which the first transmission signal S11 is supplied from group g to group g+1, and the second signal switching unit 22 switches the group to which the second transmission signal S12 is supplied from group h to group h+1. As a result, by sequentially switching the output terminals of the first signal switching unit 21 and the second signal switching unit 22, the supply destination of the first transmission signal S11 or the second transmission signal S12 is sequentially switched to the adjacent group. In this way, the sweep of the wave transmitting array 10 is performed group by group.

[0169] 10 and 11(a) and (b) can also be applied to this modified example. In this case, the first signal switching unit 113 and the second signal switching unit 123 and the configuration of the wave transmitting array 10 in FIG. 10 are replaced with the configuration in FIG. 15. As described above, the control unit 101 controls each unit of the wave transmitting system so that the sweep by the first signal switching unit 113 and the sweep by the second signal switching unit 123 partially overlap. For example, the control unit 101 controls each unit of the wave transmitting system so that the sweep by the first signal switching unit 113 and the sweep by the second signal switching unit 123 overlap by approximately half a period.

[0170] In this modification, the transmission destination of the transmission signal is switched on a group-by-group basis, thereby moving the transmission source of the transmission wave. Therefore, as in the above embodiment, the Doppler effect can cause a change in frequency in the transmission beam. Furthermore, since the sweep by the first signal switching unit 113 and the sweep by the second signal switching unit 123 partially overlap, the occurrence of ripples in the transmission waveform can be suppressed, as in the above embodiment. Furthermore, according to this modification, the transmission wave is transmitted on a group-by-group basis, thereby increasing the output and directional gain of the transmission wave.

[0171] 15, a group is formed by two wave transmitting elements 10a, but a group may be formed by three or more wave transmitting elements 10a. In this case, too, it is sufficient that the transmission source of the transmission wave is moved by switching the transmission destination of the transmission signal on a group-by-group basis.

[0172] Second Embodiment In the above embodiment, waves are transmitted using one transmitting array 10. In an embodiment, transmission is performed using two transmit arrays.

[0173] FIG. 16 is a diagram showing a configuration for transmitting waves using two transmitting arrays.

[0174] 16, in the second embodiment, the wave transmitting system includes a first wave transmitting array 11, a second wave transmitting array 12, a first signal switching unit 21, a second signal switching unit 22, a third signal switching unit 23, and a fourth signal switching unit 24. The first wave transmitting array 11 is configured with a plurality of first wave transmitting elements 11a arranged in a row. The second wave transmitting array 12 is configured with a plurality of second wave transmitting elements 12a arranged in a row. The second wave transmitting elements 12a are arranged between adjacent first wave transmitting elements 11a.

[0175] A first transmission signal S11 is supplied to a terminal T1 of the first signal switching unit 21, and a second transmission signal S12 is supplied to a terminal T2 of the second signal switching unit 22. The first signal switching unit 21 and the second signal switching unit 22 each switch the first transmitting element 11a in the first transmitting array 11 to which the first transmission signal S11 and the second transmission signal S12 are to be supplied. A third transmission signal S13 is supplied to a terminal T3 of the third signal switching unit 23, and a fourth transmission signal S14 is supplied to a terminal T4 of the fourth signal switching unit 24. The third signal switching unit 23 and the fourth signal switching unit 24 each switch the second transmitting element 12a in the second transmitting array 12 to which the third transmission signal S13 and the fourth transmission signal S14 are to be supplied.

[0176] In the second embodiment, in the first transmitting array 11, the third signal switching unit 23 is controlled so that wave transmission is performed from the second transmitting element 12a of the second transmitting array 12 sandwiched between element n and element n+1 at the timing when the first signal switching unit 21 switches the first transmitting element 11a to which the first transmission signal S11 is supplied from element n to element n+1. Furthermore, in the first transmitting array 11, the fourth signal switching unit 24 is controlled so that wave transmission is performed from the second transmitting element 12a of the second transmitting array 12 sandwiched between element m and element m+1 at the timing when the second signal switching unit 22 switches the first transmitting element 11a to which the second transmission signal S12 is supplied from element m to element m+1.

[0177] Thus, in the second embodiment, the gaps between the transmission waves of the first transmission signal S11 are interpolated by the transmission waves of the third transmission signal S13, and the gaps between the transmission waves of the second transmission signal S12 are interpolated by the transmission waves of the fourth transmission signal S14.

[0178] FIG. 17 is a diagram showing an application example of a window according to the second embodiment.

[0179] 17, as in the case of FIG. 7, a sweep in sweep period T21 is set between the sweep in sweep period T11 and the sweep in sweep period T12. In this case, the sweep in sweep period T21 also starts near the middle of sweep period T11. The sweep in the next sweep period T12 also starts near the middle of sweep period T21. Windows W11, W12, and W21, shown by dashed lines in the middle, are set in sweep periods T11, T12, and T21, respectively, and a window W0 is set over the entire transmission pulse.

[0180] In the sweep periods T11 and T12, the window W1a indicated by the solid line is a window applied during a period in which the first transmission signal S11 is supplied to the first wave transmitting element 11a by the first signal switching unit 21 in Fig. 16, and the window W1b indicated by the dashed line is a window applied during a period in which the third transmission signal S13 is supplied to the second wave transmitting element 12a by the third signal switching unit 23 in Fig. 16. In addition, in the sweep period T21, the window W2a indicated by the solid line is a window applied during a period in which the second transmission signal S12 is supplied to the first wave transmitting element 11a by the second signal switching unit 22 in Fig. 16, and the window W2b indicated by the dashed line is a window applied during a period in which the fourth transmission signal S14 is supplied to the second wave transmitting element 12a by the fourth signal switching unit 24 in Fig. 16.

[0181] In a sweep period T11, a weighting obtained by superimposing the window W1a, the window W11, and the window W0 is applied to the first transmission signal S11, and a weighting obtained by superimposing the window W1b, the window W11, and the window W0 is applied to the third transmission signal S13. The same is applied in a sweep period T12. In a sweep period T21, a weighting obtained by superimposing the window W2a, the window W21, and the window W0 is applied to the second transmission signal S12, and a weighting obtained by superimposing the window W2b, the window W21, and the window W0 is applied to the fourth transmission signal S14.

[0182] In the case of FIG. 17, the windows applied to the first transmission signal S11, the second transmission signal S12, the third transmission signal S13, and the fourth transmission signal S14, respectively, are applied to a transmission signal (e.g., a chirp signal) that is frequency modulated from the start of the sweep period T11 (the start point of the transmission pulse) to the end of the sweep period T12 (the end point of the transmission pulse), thereby generating the first transmission signal S11, the second transmission signal S12, the third transmission signal S13, and the fourth transmission signal S14.

[0183] That is, the first transmission signal S11 is generated by applying the windows W1a, W11, and W0 of Fig. 17 to the frequency-changed transmission signal. The second transmission signal S12 is generated by applying the windows W2a, W21, and W0 of Fig. 17 to the frequency-changed transmission signal. The third transmission signal S13 is generated by applying the windows W1b, W11, and W0 of Fig. 17 to the frequency-changed transmission signal. The fourth transmission signal S14 is generated by applying the windows W2b, W21, and W0 of Fig. 17 to the frequency-changed transmission signal.

[0184] FIG. 18(a) is a diagram showing the simulation results of the waveform of the transmitted wave obtained by simulation for a comparative example, and FIG. 18(b) is a diagram showing the results of receiving and processing the echo of this transmitted wave obtained by simulation.

[0185] In the comparative example, the sweep during the sweep period T21 and the setting of windows W2a, W2b, and W21 are omitted in FIG. 17. Furthermore, in the comparative example, it is assumed that the target is located at a position at an azimuth of 0 degrees in the sweep direction (a position in the front direction). In the simulations of FIGS. 18(a) and 18(b), it is assumed that the sweep is repeated five times to generate a transmission pulse for one detection unit. The vertical and horizontal axes of the graphs of FIGS. 18(a) and 18(b) are the same as the vertical and horizontal axes of the graphs of FIGS. 6(a) and 6(b).

[0186] In this comparative example, as shown in Fig. 18(a), multiple ripples R1 occur before and after the central waveform P0. Therefore, as shown in Fig. 18(b), in the reception processing result, a high-intensity region (region indicated by a dashed ellipse) occurs not only at the normal range position D0 of the target but also at the range position D1 corresponding to the ripple R1. In this case, as in the case of Fig. 6(b), an image of the target is displayed in the detected image of the target not only at the normal range position D0 of the target but also at the range position D1 corresponding to the ripple R1.

[0187] FIG. 19(a) is a diagram showing the simulation results of the waveform of the transmission wave obtained by simulation according to the second embodiment, and FIG. 19(b) shows the results of receiving and processing the echo of this transmission wave obtained by simulation.

[0188] The simulation results in Figures 19(a) and (b) are obtained when the sweep period and windows are set as in Figure 17. That is, in this simulation, unlike the comparative example, sweeping is also performed in sweep period T21 between sweep periods T11 and T12, and windows W2a, W2b, and W21 are set in this sweep period T21.

[0189] In the simulations of Figures 19(a) and (b), the sweep was repeated five times and one detection was made. It is assumed that a unit transmission pulse is generated. The vertical and horizontal axes of the graphs in Figures 19(a) and 19(b) are the same as the vertical and horizontal axes of the graphs in Figures 8(a) and 8(b).

[0190] As shown in FIG. 19(a), in the second embodiment, the ripple R1 as in FIG. 18(a) does not occur, and the transmitted waveform is only a single-peaked waveform P0. Therefore, as shown in FIG. 19(b), in the reception processing result, a high-intensity region (region indicated by a dashed ellipse) occurs only at the normal distance position D0 of the target. In the simulation result of FIG. 19(b), the high-intensity region is more densely concentrated at the normal distance position than in FIG. 8(b). Therefore, in the detection image of the target, an image showing the target is displayed only at the normal distance position of the target. Therefore, according to the sweeping method of the second embodiment, the position of the target can be displayed more clearly in the detection image, and the accuracy of the image showing the target can be improved.

[0191] FIG. 20 is a block diagram showing a specific configuration of the target detection device 1 according to the second embodiment.

[0192] For convenience, only the configuration of the wave transmitting system is shown in Fig. 20. The configuration of the wave receiving system of the target detection device 1 is the same as that in Fig. 10.

[0193] 20 , the target detection device 1 includes a first transmission signal generator 111, a second transmission signal generator 121, a third transmission signal generator 131, and a fourth transmission signal generator 141, which generate the above-mentioned first transmission signal S11, second transmission signal S12, third transmission signal S13, and fourth transmission signal S14, respectively. The first transmission signal S11, second transmission signal S12, third transmission signal S13, and fourth transmission signal S14 generated by the first transmission signal generator 111, second transmission signal generator 121, third transmission signal generator 131, and fourth transmission signal generator 141 are amplified by a first transmission amplifier 112, second transmission amplifier 122, third transmission amplifier 132, and fourth transmission amplifier 142, respectively, and then supplied to a first signal switcher 113, a second signal switcher 123, a third signal switcher 133, and a fourth signal switcher 143.

[0194] The first signal switching unit 113, the second signal switching unit 123, the third signal switching unit 133, and the fourth signal switching unit 143 have the same configuration as the first signal switching unit 21, the second signal switching unit 22, the third signal switching unit 23, and the fourth signal switching unit 24 in Fig. 16, respectively. The first signal switching unit 113 and the second signal switching unit 123 switch the first wave transmitting elements 11a to which the first transmission signal S11 and the second transmission signal S12 are to be supplied in the first wave transmitting array 11, as described above. Also, the third signal switching unit 133 and the fourth signal switching unit 143 switch the second wave transmitting elements 12a to which the third transmission signal S13 and the fourth transmission signal S14 are to be supplied in the second wave transmitting array 12, as described above.

[0195] The first transmission signal S11, the second transmission signal S12, the third transmission signal S13, and the fourth transmission signal S14 supplied to each transmitting element are weighted by the first transmission signal generation unit 111, the second transmission signal generation unit 121, the third transmission signal generation unit 131, and the fourth transmission signal generation unit 141, respectively, by each window shown in FIG. 17, as described above.

[0196] In the configuration of the receiving system, the parameter values ​​of each matched filter 213 shown in Fig. 11(a) are changed according to the generation method shown in Fig. 17. In this case as well, parameters according to the ideal transmission waveform in each iso-frequency plane are applied to each matched filter 213.

[0197] <Effects of the second embodiment> In the configuration of the second embodiment, similarly to the case of Fig. 7, the side lobes are suppressed by applying the windows shown in Fig. 17. Also, similarly to the case of Fig. 7, deep valleys do not occur at the boundaries of the windows W11, W12, and W21, so that the ripple R1 in the transmission waveform is suppressed. This suppresses the occurrence of

[0198] 17, the gaps between the waves transmitted by the first transmission signal S11 are interpolated by the waves transmitted by the third transmission signal S13, and the gaps between the waves transmitted by the second transmission signal S12 are interpolated by the waves transmitted by the fourth transmission signal S14. This makes it possible to prevent unnecessary frequency components from being superimposed on the transmission waves, and allows for more accurate processing based on the received signals.

[0199] Also, as shown in Figure 16, within the second transmitting array 12, element n+1 is adjacent to element n, element m+1 is adjacent to element m, element n of the first transmitting array 11 is adjacent to element n of the second transmitting array 12, and element m of the first transmitting array 11 is adjacent to element m of the second transmitting array 12.

[0200] As a result, while the transmission source of the transmission wave based on the first transmission signal S11 moves from element n to element n+1 in the first transmission array 11, the transmission wave based on the third transmission signal S13 is transmitted from element n in the second transmission array 12 at a position between element n and element n+1. Also, while the transmission source of the transmission wave based on the second transmission signal S12 moves from element m to element m+1 in the first transmission array 11, the transmission wave based on the fourth transmission signal S14 is transmitted from element m in the second transmission array 12 at a position between element m and element m+1. This makes it easier to maintain the continuity of the transmission waves, and therefore makes it possible to prevent unnecessary frequency components from being superimposed on the transmission waves.

[0201] <Other change examples> The present invention is not limited to the configurations of the above embodiment and embodiment 2. Furthermore, the embodiments of the present invention can be modified in various ways in addition to the above configurations.

[0202] For example, in the above embodiment, as shown in FIGS. 11(a) and 11(b), pulse compression is performed by the matched filter 213, and then the signals are separated into signals for each direction by beamforming. However, it is also possible to first separate the received signal into signals for each direction by beamforming, and then perform pulse compression on the separated signals for each direction by a matched filter.

[0203] Furthermore, in the second embodiment described above, the first transmission signal S11 and the second transmission signal S12 before the window is applied are the same signal as the third transmission signal S13 and the fourth transmission signal S14 before the window is applied, but as long as unnecessary frequency components of the transmission wave can be suppressed, the first transmission signal S11 and the second transmission signal S12 before the window is applied and the third transmission signal S13 and the fourth transmission signal S14 before the window is applied may be different signals from each other.

[0204] Furthermore, in the above embodiment, the carrier signals of the first transmission signal S11 and the second transmission signal S12 are frequency modulated, but the frequency of the carrier signals may be constant. In this case, the configuration of the received signal processing unit 203 is changed as shown in Figures 21(a) and 21(b). That is, in the configuration of Figure 21(a), the matched filter 213 of Figure 11(a) is changed to a bandpass filter 215. Each bandpass filter 215 extracts frequency components of the corresponding iso-frequency plane from the received signal of each channel and outputs them to the beam synthesis unit 214 at the subsequent stage.

[0205] 21(b), the matched filter 222 in FIG. 11(b) is replaced with a frequency extraction unit 224. The FFT 211 calculates a frequency spectrum from the received signal of each channel. The frequency extraction unit 224 extracts frequency components of the corresponding iso-frequency plane from the calculated frequency spectrum of each channel. The extracted frequency components of each iso-frequency plane are converted into time-domain signals by the IFFT 223 and output to the beam synthesis unit 214 at the subsequent stage. can be.

[0206] In this way, even when the carrier signal frequencies of the first transmission signal S11 and the second transmission signal S12 are constant, by setting each window as shown in Fig. 7 and supplying the first transmission signal S11 and the second transmission signal S12 to each transmitting element 10a of the transmitting array 10 using the configuration of Fig. 9, the occurrence of ripples in the envelope of the transmission waveform is suppressed, thereby improving the accuracy of target detection.

[0207] Note that the configuration of the modified example shown in Fig. 15 and the configuration of the second embodiment shown in Fig. 16 to Fig. 20 may also be applied to this modified example, thereby achieving the same effects as those of the modified example and the second embodiment.

[0208] Furthermore, in the second embodiment, the timing for switching the first wave-transmitting element 11a to which the first transmission signal S11 and the second transmission signal S12 are supplied and the timing for switching the second wave-transmitting element 12a to which the third transmission signal S13 and the fourth transmission signal S14 are supplied are not limited to the timings shown in FIG. 17, and may be other timings as long as they can suppress unnecessary frequency components occurring in the transmission waves.

[0209] Furthermore, in the second embodiment, the configurations of the first transmitting array 11 and the second transmitting array 12 are not limited to the configuration shown in Figure 16, and may be other configurations as long as they can cause a frequency change in the transmitting beam TB1 based on the Doppler effect.

[0210] For example, as shown in Fig. 22(a), the first and second wave transmitting arrays 11 and 12 may be configured so that the second wave transmitting element 12a is positioned to the side of the boundary between two adjacent first wave transmitting elements 11a. In this case, the first and second transmission signals S11, S12, S13, and S14 are supplied to the corresponding wave transmitting elements of the first and second wave transmitting arrays 11 and 12, respectively, at the same timing as in Fig. 17. This makes it possible to suppress unnecessary frequency components occurring in the transmission waves.

[0211] Furthermore, the method of grouping the wave transmitting elements 10a is not limited to the method shown in FIG. 15, and other methods may be used as long as the wave transmitting source can be moved in one direction. For example, as shown in FIG. 22(b), a configuration may be adopted in which multiple wave transmitting elements 10a are grouped into multiple groups, and the destination of the transmission signal S1 is switched between the groups. This configuration also allows the wave transmitting source to move in the movement direction D10, thereby causing a frequency change in the transmission beam TB1 based on the Doppler effect. Furthermore, since the transmission wave is transmitted for each group, the output of the transmission wave can be increased. The number of grouped wave transmitting elements 10a is not limited to two, and may be three or more.

[0212] The number of transmitting elements is not limited to the numbers shown in the above embodiment and the second embodiment, and may be any number as long as it is plural. In the above embodiment, the transmitting array 10 and the receiving array 30 are arranged perpendicular to each other, but the transmitting array 10 and the receiving array 30 may be arranged at an angle slightly deviated from the perpendicular.

[0213] Furthermore, in the above embodiment, as shown in FIG. 9, the first signal switching unit 21 is configured with one demultiplexer, but the first signal switching unit 21 may be configured with a plurality of demultiplexers.

[0214] For example, when the first signal switching unit 21 is configured by two demultiplexers, odd-numbered wave transmitting elements 10a are connected to a plurality of terminals on the output side of one of the demultiplexers. The second signal switching unit 22, the third signal switching unit 23, and the fourth signal switching unit 24 may each be configured with a plurality of demultiplexers. Alternatively, the second signal switching unit 22, the third signal switching unit 23, and the fourth signal switching unit 24 may each be configured with a plurality of demultiplexers. The first transmission signal S11 may be input to each of the two demultiplexers, and the even-numbered wave transmitting elements 10a may be connected to a plurality of terminals on the output side of the other demultiplexer. In this case, the first transmission signal S11 is input to each of the two demultiplexers, and the two demultiplexers are controlled so that one demultiplexer supplies the first transmission signal S11 to the wave transmitting element 10a at the timing when the odd-numbered wave transmitting element 10a is driven, and the other demultiplexer supplies the first transmission signal S11 to the wave transmitting element 10a at the timing when the even-numbered wave transmitting element 10a is driven. Similarly, the second signal switching unit 22, the third signal switching unit 23, and the fourth signal switching unit 24 may each be configured with a plurality of demultiplexers.

[0215] Furthermore, the sweeping method of the transmitting array is not limited to the methods described in the above embodiment and the second embodiment, and other sweeping methods may be used. For example, in a unit pulse period, the transmitting array 10 may be swept once by the first transmission signal S11 and once by the second transmission signal S12.

[0216] 14 shows a configuration in which the target detection device 1 (sonar, radar) is installed on the ship 2, but the target detection device 1 (sonar, radar) may be installed on a moving body other than the ship 2, or the target detection device 1 (sonar, radar) may be installed on a structure other than a moving body, such as a buoy. For example, the target detection device 1 (sonar) may be installed inside a fish pen to observe fish cultivated in the fish pen.

[0217] The embodiments of the present invention may be modified as appropriate within the scope of the claims. [Explanation of symbols]

[0218] 1. Target detection device 10 Transmitting array (first transmitting array) 10a Wave transmitting element (first wave transmitting element) 11 First transmitting array 11a First transmitting element 12 Second transmitting array 12a Second transmitting element 30 Receiving Array 30a Receiving element 101 Control section 111 First transmission signal generation unit 113 First signal switching unit 121 Second transmission signal generation unit 123 Second signal switching unit 131 Third transmission signal generation unit 133 Third signal switching unit 141 Fourth transmission signal generation unit 143 4th signal switching unit 203 Received signal processing section S11 First transmission signal S12 Second transmission signal S13 Third transmission signal S14 Fourth transmission signal EP1~EP5 Equal frequency plane

Claims

1. In the target detection device, a first transmission signal generator that generates a first transmission signal; a second transmission signal generator that generates a second transmission signal; a first transmitting array having a plurality of first transmitting elements that convert the first transmitting signal and the second transmitting signal into a transmitting wave; a first signal switching unit that supplies the first transmission signal to one of the first wave transmitting elements in the first wave transmitting array; a second signal switching unit that supplies the second transmission signal to one of the first wave transmitting elements in the first wave transmitting array; a control unit that performs first control in which the first signal switching unit switches the first wave-transmitting element to which the first transmission signal is supplied from element n to element n+1, and the second signal switching unit switches the first wave-transmitting element to which the second transmission signal is supplied from element m to element m+1.

2. The target detection device according to claim 1, A target detection device, wherein in the first transmitting array, the element n+1 is adjacent to the element n, and the element m+1 is adjacent to the element m.

3. 3. The target detection device according to claim 2, After the first control, the control unit performs second control in which the first signal switching unit switches the first wave-transmitting element to which the first transmission signal is supplied from element n+1 to element n+2 adjacent to element n+1, and the second signal switching unit switches the first wave-transmitting element to which the second transmission signal is supplied from element m+1 to element m+2 adjacent to element m+1.

4. The target detection device according to any one of claims 1 to 3, When the first transmit array includes P first transmit elements, If the P is an even number, (P / 2)-1 first transmitting elements are included between the element n and the element m, If the P is an odd number, (P-1) / 2 or {(P-1) / 2}-1 first wave transmitting elements are included between the element n and the element m.

5. The target detection device according to any one of claims 1 to 4, When the first wave transmitting array includes P first wave transmitting elements, i.e., first wave transmitting element 1 to first wave transmitting element P, If the element n+1 corresponds to a first wave transmitting element that exceeds the first wave transmitting element P, the first signal switching unit switches the first wave transmitting element to which the first transmission signal is supplied from the first wave transmitting element P to the first wave transmitting element 1, If the element m+1 corresponds to a first wave transmitting element that exceeds the first wave transmitting element P, the second signal switching unit switches the first wave transmitting element to which the second transmission signal is supplied from the first wave transmitting element P to the first wave transmitting element 1.

6. The target detection device according to any one of claims 1 to 5, the first transmission signal is a frequency modulated signal; The target detection device, wherein the second transmission signal is a frequency modulated signal.

7. The target detection device according to claim 1, The plurality of first transmitting elements are grouped into a plurality of groups, and each group has a plurality of first transmitting elements. a number of the first transmitting elements are connected, the first signal switching unit is configured to supply the first transmission signal to one of the groups in the first transmitting array; the second signal switching unit is configured to supply the second transmission signal to one of the groups in the first transmitting array; During the first control of the control unit, the first signal switching unit switches the group to which the first transmission signal is supplied from group g to group g+1, and the second signal switching unit switches the group to which the second transmission signal is supplied from group h to group h+1.

8. The target detection device according to claim 7, The group g and the group g+1 share at least one of the first wave transmitting elements, and the group h and the group h+1 share at least one of the first wave transmitting elements.

9. The target detection device according to any one of claims 1 to 8, the element n is supplied with a first portion of the first transmit signal; the element n+1 is supplied with a second portion of the first transmit signal that is different from the first portion; said element m is supplied with a first portion of said second transmit signal; The element m+1 is supplied with a second portion of the second transmission signal that is different from the first portion of the second transmission signal.

10. The target detection device according to any one of claims 1 to 9, a third transmission signal generator that generates a third transmission signal; a fourth transmission signal generator that generates a fourth transmission signal; a second transmitting array having a plurality of second transmitting elements that convert the third transmitting signal and the fourth transmitting signal into a transmitting wave; a third signal switching unit that supplies the third transmission signal to one of the second wave transmitting elements in the second wave transmitting array; a fourth signal switching unit that supplies the fourth transmission signal to one of the second wave transmitting elements in the second wave transmitting array, After the first control, the control unit further controls the third signal switching unit to switch the second wave transmitting element to which the third transmission signal is supplied from element n to element n+1, The fourth signal switching unit performs third control to switch the second wave-transmitting element to which the fourth transmission signal is supplied from element m to element m+1.

11. The target detection device according to claim 10, In the second transmit array, the element n+1 is adjacent to the element n, and the element m+1 is adjacent to the element m; A target detection device, wherein the element n of the first transmitting array is adjacent to the element n of the second transmitting array, and the element m of the first transmitting array is adjacent to the element m of the second transmitting array.

12. The target detection device according to claim 10 or 11, the third transmission signal is a frequency modulated signal; The fourth transmission signal is a frequency modulated signal.

13. The target detection device according to any one of claims 1 to 12, The target detection device further comprises a wave receiving array including at least one wave receiving element that receives a reflected wave generated by reflection of the transmitted wave from a target and converts the reflected wave into a received signal.

14. The target detection device according to claim 13, a reception signal processing unit that processes the reception signal, The received signal processing unit extracts the iso-frequency received signal based on the reflected wave from an iso-frequency surface corresponding to the frequency of the received signal, based on the frequency component of the received signal.

15. The target detection device according to claim 14, The received signal processing unit A target detection device that extracts a plurality of frequency components, each extracted at a different frequency, from the received signal, thereby obtaining the iso-frequency received signal of the iso-frequency plane corresponding to each frequency.

16. The target detection device according to claim 14, The received signal processing unit calculating a frequency spectrum of the received signal; The target detection device acquires the iso-frequency received signals of the iso-frequency plane corresponding to each frequency based on the frequency spectrum.

17. The target detection device according to any one of claims 13 to 16, the receive array includes a plurality of receive elements; The received signal processing unit performs beamforming based on the received signals generated from the wave receiving elements, and calculates the arrival direction of the reflected wave from the target based on the beamforming.

18. The target detection device according to any one of claims 13 to 17, the receive array includes a plurality of receive elements; The receive array is different from the first transmit array, A target detection device, wherein a receiving beam generated based on the received signals generated from each of the receiving elements intersects with a transmitting beam generated by the first transmitting array.

19. In the target detection method, performing a first sweep in which a plurality of wave transmitting elements arranged in a row are swept with a first transmission signal; a second sweep for sweeping the plurality of wave-transmitting elements with a second transmission signal is started at a timing before the first sweep is completed.

20. 20. The target detection method according to claim 19, The target detection method includes starting the second sweep at a timing approximately half a cycle of the first sweep.

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