TARGET VERIFICATION DEVICE AND TARGET VERIFICATION PROCEDURE

Description

TECHNICAL FIELD

[0001] An example embodiment of the present disclosure generally relates to a target detection device for detecting targets in a water body or in air.BACKGROUND OF THE INVENTION

[0002] With advancements in the field of marine sonar technology, nowadays marine sonars are used for a number of marine activities. For example, the marine sonars are used in surveillance systems for visualizing underwater conditions by detecting targets such as shipwrecks, fish schools, a seabed, etc. A known sonar for marine use is disclosed in US2008 / 0043574A1 (Rooney et. Al.), wherein a low probability of marine mammal impact (LPMMI) waveform is generated having a modulation component selected to reduce a behavioral response from marine mammals. Some commonly known marine sonars transmit a transmission wave using a two dimensional (2D) array and detect the targets based on a reception wave corresponding to the transmission wave. However, the use of a 2D array makes the marine sonars expensive because of the large number of elements in the 2D array. To that end, some other marine sonars use a T-shaped array, where a transmission array and a reception array are perpendicularly arranged to each other. However, the use of T-shaped array does not allow visualizing the underwater conditions in a single transmission. For instance, the transmission wave transmitted by the T-shaped array may be a fan beam. Therefore, the marine sonars that use T-shaped array need to transmit the transmission wave multiple times by changing direction of the transmission wave for visualizing the underwater conditions. Accordingly, the marine sonars that use T-shaped array consume more power, and are inefficient thereby making the visualizing task more challenging. A similar problem may arise with a radar that detects targets in air.

[0003] A prior art document US6678210 relates to a sonar array forming multiple transmit and / or receive acoustic beams by a frequency beam forming technique. According to this method, since beams of different frequencies are formed in each direction of the transmission array direction by single transmission, it is possible to perform separation in the transmission array direction by performing band separation at the time of receiving. However, since frequency and range of direction of the beam are closely related, these cannot be set independently. So, when a wide range of direction is needed, the frequency range needs to be wide. However, it is complex and expensive to make a Sonar that handles a wide frequency range.

[0004] Accordingly, there is a need for a target detection device and a target detection method for detecting the targets in an efficient and feasible manner such that the visualization of the target and / or its environment is achieved in a single transmission.SUMMARY OF THE INVENTION

[0005] The invention is set out in the appended set of claims. In order to solve the foregoing problem, the present invention provides a target detection device. The target detection device comprises a transmission array having a plurality of transmission transducer elements; and a signal generator configured to: generate a plurality of transmission signals, wherein to generate each transmission signal of the plurality of transmission signals, the signal generator is further configured to change a phase of a base signal by a phase shift amount that changes continuously over time; and input to each transmission transducer element of the plurality of transmission transducer elements a corresponding generated transmission signal of the plurality of transmission signals. The target detection device also comprises a reception array having a plurality of reception elements, wherein the reception array is configured to receive a reception wave from a target, and each reception element is configured to convert the reception wave into a corresponding reception signal. An emission direction of a transmission wave transmitted by the transmission array changes over time, and a frequency of the transmission wave changes over time with the change in the emission direction of the transmission wave over time. This may facilitate 3D detection of echoes.

[0006] In additional target detection device embodiments, a first phase shift amount of a first transmission signal of the plurality of transmission signals at a first time is different from a second phase shift amount of the first transmission signal at a second time. The first phase shift amount and the second phase shift amount are measured with respect to the phase of the base signal. The first time is different from the second time.

[0007] In additional target detection device embodiments, a third phase shift amount of a second transmission signal of the plurality of transmission signals at the first time is different from the first phase shift amount of the first transmission signal at the first time. The third phase shift amount and the first phase shift amount are measured with respect to the phase of the base signal. The second transmission signal is different from the first transmission signal.

[0008] In additional target detection device embodiments, a first phase difference between the first transmission signal and the second transmission signal at the first time is different from a second phase difference between the first transmission signal and the second transmission signal at the second time.

[0009] In additional target detection device embodiments, an emission direction of a transmission wave transmitted by the transmission array changes over said time in response to the change in the phase shift amount over said time.

[0010] In additional target detection device embodiments, a carrier of the base signal is a frequency modulated carrier.

[0011] In additional target detection device embodiments, the emission direction of the transmission wave changes non-linearly with time.

[0012] In additional target detection device embodiments, the target detection device further comprises a processing circuitry configured to calculate an incoming direction of the reception wave in a first dimension by performing beamforming based on the received reception signals.

[0013] The processing circuitry may be further configured to extract frequency components from the reception signals to obtain a second incoming direction of the reception wave, different from the (first) incoming direction, based on a unique direction-frequency relationship between the emission directions of the transmission wave and frequency, and to generate 3D volume data based on the received reception signals, the (first) incoming direction and the second incoming direction.

[0014] In additional target detection device embodiments, the processing circuitry is further configured to: extract a plurality of different frequency components from the reception signals, wherein each frequency component corresponds to a different incoming direction in a second dimension, wherein the second dimension is different than the first dimension; and calculate an incoming direction of the reception wave in the second dimension, based on the extracted plurality of different frequency components.

[0015] In additional target detection device embodiments, directions of arrangement of the plurality of transmission transducer elements and the plurality of reception elements are perpendicular.

[0016] In additional target detection device embodiments, the target detection device is a sonar that detects underwater targets.

[0017] In additional target detection device embodiments, the target detection device is a radar that detects targets in air.

[0018] In another aspect, the present invention provides a target detection method. The target detection method comprises: generating a plurality of transmission signals, wherein for generating each transmission signal of the plurality of transmission signals the target detection method further comprises phase shifting a phase of a base signal by a phase shift amount that changes over time; inputting a corresponding generated transmission signal of the plurality of transmission signals into one of a plurality of transmission transducer elements; transmitting a transmission wave from the plurality of transmission transducer elements; and receiving a reception wave from a target using a plurality of reception elements, wherein each reception element converts the reception wave into a corresponding reception signal; wherein an emission direction of the transmission wave transmitted by the transmission transducer elements changes over time, and a frequency of the transmission wave changes over time with the change in the emission direction of the transmission wave over time.

[0019] In additional target detection method embodiments, a phase shift amount of each transmission signal, with respect to the phase of the base signal, varies continuously over the time, and a phase difference between any two transmission signals of the plurality of transmission signals varies continuously over the time.

[0020] In accordance with various embodiments, the present disclosure proposes the target detection device for detecting the targets such that the visualization of the underwater conditions is achieved in single transmission. To that end, the target detection device transmits a transmission wave as beams of different emission directions at different frequencies and at different time instances. Thereby the target detection device transmits the transmission wave in a detection range and enables to visualize the underwater or air conditions in single transmission. For example, the target detection device may allow 3D visualization of a target and / or its environment. In order to transmit the transmission wave as the beams of different emission directions at different frequencies and at different time instances, the target detection device generates each of the plurality of transmission signals by phase shifting the phase of the base signal by a phase shift amount that changes with time. As each transmission signal is generated by phase shifting the phase of the base signal by the phase shift amount that changes with time, the target detection device enables to control the detection range of the transmission wave using the phase shift amount applied to phase shift the base signal. Thereby, a frequency range of signals inputted to a transmission array is not dependent on the detection range of the transmission wave, as the detection range of transmission wave is controlled by the phase shift amount applied to the base signal. As the frequency range is not depending on the detection range of the transmission wave, the target detection device enables to select a frequency range of the base signal independently without considering the detection range of the transmission wave. For instance, a base signal of a small frequency range (or a constant frequency signal) may be selected for transmitting the transmission wave. To that end, the target detection device detects targets in single transmission with a narrow frequency band that is similar to the frequency range of the base signal.

[0021] However, in currently available technologies, the detection range is completely dependent on the frequency range of the signals inputted to the transmission array. For instance, in the currently available technologies, a detection range of about 20 degree (e.g., 10 degree to 30 degree) is achieved by designing signals from a wide frequency band of about 200 kHz. Thereby, the currently available technologies demand for additional circuitry and a transmission array, which are capable of handling a wide frequency range.

[0022] In contrast, the target detection device of the present disclosure may not require the additional circuitry and the transmission array capable of handling the wide frequency range, due to the fact that the frequency range of the base signal is independent of the detection range. Thereby cost of the target detection device is low, in comparison to the currently available technologies.

[0023] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.EFFECT(S) OF THE INVENTION

[0024] According to this invention, a target detection device and a target detection method is provided. The invention enables the target detection device to detect targets in a single transmission by transmitting a transmission wave as beams of different emission directions at different frequencies and at different time instances. The invention further enables the target detection device to control a detection range of the transmission wave by generating each of a plurality of transmission signals by phase shifting a phase of a base signal by a phase shift amount that changes with time. For instance, the target detection device controls the detection range of the transmission wave by phase shift amount applied to the base signal. Furthermore, the target detection device enables to select a frequency range of the base signal independently without considering the detection range of the transmission wave, as the detection range of the transmission wave is controlled by the phase shift amount applied to the base signal. Furthermore, the invention enables target detection device to detect targets in a single transmission by using a narrow frequency band that is similar to the frequency range of the base signal.BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present disclosure is illustrated by way of example and not by way of limitation in the figures of the accompanying drawings, in which the like reference numerals indicate like elements and in which: FIG. 1 illustrates a block diagram of a target detection device for detecting targets, in accordance with an example embodiment of the present invention; FIG. 2A illustrates a block diagram of a transmission part of the target detection device for transmitting a transmission wave, in accordance with an example embodiment of the present invention; FIG. 2B illustrates a phase shift process executed by a transmission signal generation part for generating a plurality of transmission signals, in accordance with an example embodiment of the present invention; FIG. 2C illustrates a schematic diagram of configuration of a transmission array, in accordance with an example embodiment of the present invention; FIG. 3A illustrates a graph showing a change in a phase shift amount with time for each of the plurality of transmission signals when a base signal is a continuous wave, in accordance with an example embodiment of the present invention; FIG. 3B illustrates a graph showing the change in the phase shift amount with time for each of the plurality of transmission signals when the base signal is a linear FM wave, in accordance with an example embodiment of the present invention; FIG. 4A illustrates a graph showing a change in an instant frequency with time for each of the plurality of transmission signals when the base signal is the continuous wave, in accordance with an example embodiment of the present invention; FIG. 4B illustrates a graph showing the change in the instant frequency with time for each of the plurality of transmission signals when the base signal is the linear FM wave, in accordance with an example embodiment of the present invention; FIG. 5 illustrates an exemplary scenario showing the transmission part for transmitting the transmission wave, in accordance with an example embodiment of the present invention; FIG. 6A illustrates a graph showing a change in an emission direction of the transmission wave with time, in accordance with an example embodiment of the present invention; FIG. 6B illustrates a graph showing a change in an emission direction of the transmission wave with time, in accordance with another example embodiment of the present invention; FIG. 7 illustrates graphs showing the change in the emission direction with respect to time when the base signal is the continuous wave, in accordance with an example embodiment of the present invention; FIG. 8 illustrates graphs showing the change in the emission direction with respect to time when the base signal is the linear FM wave, in accordance to an example embodiment of the present invention; FIG. 9A illustrates a diagram showing the transmission wave transmitted by the transmission array, in accordance with an example embodiment of the present invention; FIG. 9B illustrates a parallel arrangement of the transmission array and a reception array, in accordance with an example embodiment of the present invention; FIG. 10A illustrates a reception process for receiving a reception wave corresponding to the transmission wave when the transmission array and the reception array are perpendicularly arranged, in accordance with an example embodiment of the present invention; FIG. 10B illustrates the reception process for receiving the reception wave corresponding to the transmission wave when the transmission array and the reception array are arranged in parallel, in accordance with an example embodiment of the present invention; FIG. 11A is a block diagram of the target detection device for detecting the targets, in accordance with an example embodiment of the present invention; FIG. 11B illustrates a block diagram of a receiver part, in accordance with an example embodiment of the present invention; FIG. 12A illustrates a block diagram of the signal processing part for calculating the volume data, in accordance with an example embodiment of the present invention; FIG. 12B illustrates a block diagram of the signal processing part for calculating the volume data, in accordance with an another example embodiment of the present invention; FIG. 12C illustrates a block diagram of the signal processing part when the base signal is the continuous wave, in accordance with yet another example embodiment of the present invention; FIG. 13A illustrates a target detection method for transmitting the transmission wave, in accordance with an example embodiment of the present invention; FIG. 13B illustrates a target detection method for processing the reception wave, in accordance with an example embodiment of the present invention; and FIG. 14 illustrates a working environment of the target detection device for detecting the targets, in accordance with an example embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0026] One of the objectives of the present disclosure is to detect targets such that visualization of the underwater conditions is achieved in single transmission. To that end, a transmission wave is transmitted as the beams of different emission directions at different frequencies and at different time instances. Thereby the transmission wave is propagated in a detection range which allows visualizing the underwater conditions in single transmission. In order to transmit the transmission wave as the beams of different emission directions at different frequencies and at different time instances, each of the plurality of transmission signals are generated by phase shifting the phase of the base signal by the phase shift amount that changes with time. Accordingly, the transmission wave is controlled to propagate in the detection range by the phase shift amount applied to the base signal. Thereby, a frequency range of the base signal is selected independently without considering the detection range of the transmission wave. For instance, a base signal of a small frequency range is selected for transmitting the transmission wave. Therefore, the targets can be detected for visualizing the underwater conditions in single transmission with a narrow frequency band that is similar to the frequency range of the base signal. In this way, the target detection device can detect the targets for visualizing the underwater conditions in single transmission. Further, an overview of the target detection device for detecting the targets is provided below with reference to FIG. 1.

[0027] FIG. 1 illustrates a block diagram of a target detection device 100 for detecting the targets, in accordance with an example embodiment of the present invention. In an example embodiment, the target detection device 100 is installed at a vessel navigating in the water body. In an example embodiment, the target detection device 100 is a sonar that is used to detect targets in the water body. In an embodiment, the target detection device 100 is a radar that is used to detect targets above the water body. The targets may include one or more of fish schools, shipwrecks, a seabed and the like.

[0028] The target detection device 100 includes a transmission part 100a and a reception part 100b. The transmission part 100a is configured to transmit a transmission wave 105 for detecting the targets. In an example embodiment, the target detection device 100 transmits the transmission wave 105 as beams of different emission directions at different frequencies at different time instances, to detect the targets. For instance, the transmission wave 105 is the beams of different frequencies and different emission directions with time. To that end, the transmission part 100a includes a signal generator 101 and a transmission array 103. The signal generator 101 is be configured to generate a plurality of transmission signals (mathematically represented as s n (t)) and is further configured to input the generated plurality of transmission signals s n (t) into the transmission array 103. The transmission array 103 (also referred to as a transmitting system 103) comprises a plurality of transmission elements 103a. The plurality of transmission elements 103a are transmission transducers that convert the plurality of transmission signals s n (t) into the transmission wave 105. To that end, the plurality of transmission elements 103a are referred to as a plurality of transmission transducer elements (103a). The transmission array 103 is for example a 1D array (linear array), in which the plurality of transmission elements 103a is arranged in a line, preferably a straight line. Without any limitation to the straight line arrangement of elements, the plurality of transmission elements 103a may also be arranged along a curved line.

[0029] The reception part 100b is configured to receive a reception wave 107. In an example embodiment, the reception wave 107 is a wave reflected from the at least one target, in response to transmitting the transmission wave 105. The reception part 100b comprises a reception array 109 and a signal processing part 111. The reception array 109 (also referred to as a reception system 109) also comprises a plurality of reception elements 109a. The plurality of reception elements 109a are be reception transducers that convert the reception wave 107 into a plurality of reception signals. The reception array is for example a 1D array (linear array), in which the plurality of reception elements 109a is arranged in a line which is preferably straight but may be curved. The signal processing part 111 (also referred to as a processing circuitry 111) is configured to receive the plurality of reception signals and is further configured to separate echoes (e.g., beams reflected from the at least one target) in a first dimension (e.g., a horizontal direction) and in a second dimension (e.g., a vertical direction), based on the reception signals. Further, the signal processing part 111 is configured to generate visual data of the detected target for visualizing the underwater conditions. In an example embodiment, the visual data is a three dimensional (3D) view of the detected target.

[0030] Additionally, the target detection device 100 comprises a controller (not shown in this figure). The controller is a micro-controller based circuit. The controller further controls the signal generator 101 to generate the plurality of transmission signal s n (t) such that the transmission wave 105 generated from the plurality of transmission signal s n (t) is propagated as the beams of different emission directions at different frequencies and at different time instances. The transmission part 100a for transmitting the transmission wave 105 (as the beams of different frequencies and different emission directions with time) is further explained in the detailed description of FIG. 2A.

[0031] FIG. 2A illustrates a block diagram of the transmission part 100a of the target detection device 100 for transmitting the transmission wave 105, in accordance with an example embodiment of the present invention. As illustrated in FIG. 2A, the transmission part 100a includes the signal generator 101 and the transmission array 103. The signal generator 101 is configured to generate the plurality of transmission signals s n (t). In an example embodiment, the signal generator 101 includes a base signal generation part 201 and a transmission signal generation part 203 for generating the plurality of transmission signals s n (t). The base signal generation part 201 is a signal generation circuit that is configured to generate a base signal (mathematically represented as bs(t)). The base signal bs(t) may be at least one of continuous wave (CW) and frequency modulated (FM) wave. Further, the FM wave may be at least one of linear FM wave (e.g., Chirp) and non-linear FM wave (e.g., hyperbolic FM wave). When the base signal bs(t) corresponds to the continuous wave, a carrier of the base signal bs(t) is a single frequency carrier. When the base signal bs(t) corresponds to the FM wave, a carrier of the base signal bs(t) is a FM carrier.

[0032] Further, the generated base signal bs(t) is inputted into the transmission signal generation part 203. The transmission signal generation part 203 is configured to generate the plurality of transmission signals s n (t) from the base signal bs(t). In an example embodiment, the transmission signal generation part 203 is configured to phase shift a phase of the base signal bs(t) by a phase shift amount that varies with time for generating each of the plurality of transmission signals s n (t). In other words, the transmission signal generation part 203 continuously calculates the phase shift amount that varies with time and phase shifts the phase of the base signal bs(t) in accordance with the calculated phase shift amount, for generating each of the plurality of transmission signals s n (t). The phase shift amount is mathematically represented as θ n (t). In an example embodiment, the transmission signal generation part 203 comprises a phase shifter 203a that is configured to calculate the phase shift amount θ n (t) and phase shift, using the calculated phase shift amount θ n (t), the phase of the base signal bs(t). In an example embodiment, the base signal generation part 201 and the transmission signal generation part 203 having the phase shifter 203a are embodied within a processor. The processor may be embodied in a number of different ways. For example, the processor may be embodied as one or more of various hardware processing means such as a coprocessor, a microprocessor, a digital signal processor (DSP), a processing element with or without an accompanying DSP, or various other processing circuitry including integrated circuits such as, for example, an ASIC (application specific integrated circuit) and an FPGA (field programmable gate array), and the like. Further, a phase shift process executed by the transmission signal generation part 203 for generating the plurality of transmission signals s n (t) from the base signal bs(t) is further explained in the detailed description of FIG. 2B.

[0033] FIG. 2B illustrates a phase shift process executed by the transmission signal generation part 203 for generating the plurality of transmission signals s n (t), in accordance with an example embodiment of the present invention. The phase shift process illustrates that the transmission signal generation part 203 generates a plurality of transmission signals s 1 (t), s 2 (t), s 3 (t), and s 4 (t) by phase shifting the phase of the base signal bs(t) by the phase shift amount θ n (t) such that the transmission wave 105 (not shown) generated from the plurality of transmission signals s 1 (t), s 2 (t), s 3 (t), and s 4 (t) is propagated in a detection range 205 with time t. The plurality of transmission signals s 1 (t), s 2 (t), s 3 (t), and s 4 (t) correspond to the plurality of transmission signals s n (t) . Here for the purpose of the explanation, four transmission signals s 1 (t), s 2 (t), s 3 (t), and s 4 (t) are considered. However, the plurality of transmission signals s n (t) may comprises any finite number of transmission signals. The detection range 205 includes emission directions of the transmission wave 105 at different time instances t 1 , t 2 , t 3 , t 4 , and t 5 . Here for the purpose of explanation, the detection range 205 of a range +30 degree to -30 degree is considered. However, the detection range 205 may have any range from a range of +90 degree to -90 degree. Further, the time t of duration 5ms is considered for exemplary purpose, however the time t may not be limited to the duration of 5ms.

[0034] In an example embodiment, the transmission signal generation part 203 generates the plurality of transmission signals s 1 (t), s 2 (t), s 3 (t), and s 4 (t) using the phase shift amount θ n (t) that is continuously varying over the time t for each transmission signal, relative to the base signal bs(t). For instance, a first phase shift amount θ 1 (t 1 ) of the first transmission signal s 1 (t) at a first time (t 1 ) is different from a second phase shift amount θ 1 (t 2 ) of the first transmission signal s 1 (t) at a second time (t 2 ). The first phase shift amount θ 1 (t 1 ) and the second phase shift amount θ 1 (t 2 ) are measured in relation to the phase of the base signal bs(t). Further, the first time (t 1 ) is different from the second time (t 2 ).

[0035] In an example embodiment, the transmission signal generation part 203 generates the plurality of transmission signals s 1 (t), s 2 (t), s 3 (t), and s 4 (t) using the phase shift amount θ n (t) that is different for any two transmission signals s 1 (t), s 2 (t), s 3 (t), and s 4 (t) at any given time instance t 1 , t 2 , t 3 , t 4 , and t 5 . For instance, a third phase shift amount θ 2 (t 1 ) of the second transmission signal s 2 (t) at the first time (t 1 ) is different from the first phase shift amount θ 1 (t 1 ) of the first transmission signal s 1 (t) at the first time (t 1 ). The third phase shift amount θ 2 (t 1 ) of the second transmission signal s 2 (t) and the first phase shift amount θ 1 (t 1 ) of the first transmission signal s 1 (t) are measured with respect to the phase of the base signal bs(t). Further, the second transmission signal s 2 (t) is different from the first transmission signal s 1 (t).

[0036] In an example embodiment, the transmission signal generation part 203 generates the plurality of transmission signals s 1 (t), s 2 (t), s 3 (t), and s 4 (t) such that a phase difference Δθ between any two transmission signals s 1 (t), s 2 (t), s 3 (t), and s 4 (t) is continuously varying with the time t. For instance, a first phase difference Δθ 1 between the first transmission signal s 1 (t) and the second transmission signal s 2 (t) at the first time (t 1 ) is different from a second phase difference Δθ 2 between the first transmission signal s 1 (t) and the second transmission signal s 2 (t) at the second time (t 2 ). The first phase difference Δθ 1 is mathematically represented as Δθ 1 = |θ 1 (t 1 ) - θ 2 (t 1 )|. The second phase difference Δθ 2 is mathematically represented as Δθ 2 = |θ 1 (t 2 ) - θ 2 (t 2 )|.

[0037] Further, the phase shift process executed by the transmission signal generation part 203 is mathematically represented as s n (t) = bs(t) · e jθn(t)< , where the notation s n (t) corresponds to the plurality of transmission signals generated by the transmission generation part 203, the notation bs(t) corresponds to the base signal generated by the base signal generation part 201, the notation θ n (t) corresponds to the phase shift amount for generating the plurality of transmission signals s n (t) from the base signal bs(t).

[0038] The base signal bs(t) is mathematically represented as bs(t) = e j2< πft< , when the base signal bs(t) corresponds to the continuous wave (CW). The base signal bs(t) is mathematically represented as bs t = e j 2 πf 1 t + π B T t 2 , when the base signal bs(t) corresponds to the Chirp signal. The notation f 1 is a start frequency, the notation B is a bandwidth, and the notation T is a pulse length.

[0039] The phase shift amount θ n (t) is mathematically represented as θ n t = 2 ⋅ π ⋅ f t ⋅ d n t c , where the notation n is a transmission element number of the transmission element 103a (e.g. n = 1, 2, 3, ..., N), the notation f(t) is an instant frequency of the base signal bs(t) at every time point t, the notation c is a constant and denotes speed of sound in the water (e.g. c = 1500m / s), the notation d n (t) is a delay distance of each transmission element 103a. The delay distance d n (t) is determined from a configuration of the transmission array 103. The configuration of the transmission array 103 is further explained in the detailed description of FIG. 2C.

[0040] FIG. 2C illustrates a schematic diagram of a configuration 209 of the transmission array 103, in accordance with an example embodiment of the present invention. The configuration 209 illustrates that the plurality of transmission elements 103a are located at coordinates l n and further illustrates that any two consecutive transmission elements 103a in the transmission array 103 are separated by a pitch p. In an example embodiment, the pitch p between any two consecutive transmission elements 103a is constant. To that end, the transmission wave 105 is smoothly transmitted in a desired emission direction. The delay distance d n (t) is mathematically represented from the configuration 209 as d n (t) = l n · sin(φ(t)), where the notation l n is the coordinates of the plurality of transmission elements 103a and the notation φ(t) is the emission direction (e.g., the detection range 205) at every time point t. The notation l n is mathematically represented as l n = p ⋅ n − p ⋅ N + 1 2 , where the notation p is the pitch between any two consecutive transmission elements 103a.

[0041] Referring to FIG. 2A, in an example embodiment, the transmission signal generation part 203 calculates the phase shift amount θ n (t) at every time point for each transmission signal s n (t) by selecting the emission direction φ(t) (e.g., an emission direction in the detection range 205) at every time point t. The transmission signal generation part 203 generates the plurality of transmission signals s n (t) by phase shifting the phase of the base signal bs(t) by the calculated phase amount θ n (t). Further, the transmission signal generation part 203 inputs each of the generated plurality of transmission signals s n (t) into one of the transmission elements 103a. Accordingly, the emission direction φ(t) of the transmission wave 105 transmitted by the transmission array 103 changes with time t in response to change in the phase shift amount θ n (t) with time t. In other words, the transmission wave 105 generated from the generated plurality of transmission signals s n (t) is the beams of different emission directions φ(t), which are varying with time t in response to change in the phase shift amount θ n (t) with time t. The change in the phase shift amount θ n (t) with time t for each of the plurality of transmission signals s n (t) is further graphically explained in the detailed description of FIGs. 3A-3B.

[0042] FIG. 3A illustrates a graph 301 showing the change in the phase shift amount θ n (t) with time t for each of the plurality of transmission signals s n (t), when the base signal bs(t) is the continuous wave, in accordance with an example embodiment of the present invention. For instance, the graph 301 illustrates the change in the phase shift amount θ n (t) for parameters N = 16, f(t) = 150kHz, p = 5mm, φ(t) = -30 to 30 degree, t = 0ms to 5ms. The notation N is a total number of transmission elements in the transmission array 103. As N = 16, the transmission signal generation part 203 generates sixteen transmission signals s n (t) (e.g., channel-1 (CH1) to channel-16 (CH16)). Here for the purpose of explanation, the graph 301 illustrates the change in the phase shift θ n (t) for sixteen transmission signals s n (t). However, the plurality of transmission signals may be any finite number of transmission signals.

[0043] As illustrated in the graph 301, x-axis of the graph 301 is time t and y-axis of the graph 301 is the phase shift amount θ n (t) for the plurality of transmission signals s n (t). The graph 301 illustrates that the phase shift amount θ n (t) (e.g. θ 1 (t) to θ 16 (t)) corresponding to the plurality of transmission signals s n (t) (e.g. CH1 to CH16) respectively is continuously varying with time t. The graph 301 further illustrates that the phase shift amount θ n (t) corresponding to any two transmission signals of the plurality of transmission signals s n (t) is different at a given time t. Furthermore, the graph 301 illustrates that the phase difference Δθ between any two transmission signals of the plurality of transmission signals s n (t) is continuously varying with the time t.

[0044] FIG. 3B illustrates a graph 303 showing the change in the phase shift amount θ n (t) with time t for each of the plurality of transmission signal s n (t), when the base signal bs(t) is the linear FM wave, in accordance with an example embodiment of the present invention. For instance, the graph 303 illustrates the change in the phase shift amount θ n (t) for parameters N = 16, f(t) = 125kHz to 175kHz , p = 5mm , φ(t) = -30 to 30 degree, t = 0ms to 5ms. The notation N is the total number of transmission elements in the transmission array 103. As N = 16, the transmission signal generation part 203 generates sixteen transmission signals s n (t) (e.g., channel-1 (CH1) to channel-16 (CH16)).

[0045] As illustrated in the graph 303, x-axis of the graph 303 is time t and y-axis of the graph 303 is the phase shift amount θ n (t) for the plurality of transmission signals s n (t). The graph 303 illustrates that the phase shift amount θ n (t) (e.g. θ 1 (t) to θ 16 (t)) corresponding to the plurality of transmission signals s n (t) (e.g. CH1 to CH16) is continuously varying with the time t. The graph 303 further illustrates that the phase shift amount θ n (t) corresponding any two transmission signals is different at a given time t. Furthermore, the graph 303 illustrates that the phase difference Δθ between any two transmission signals is continuously varying with the time t. Further, a change in the instant frequency f(t) with respect to time t for each of the plurality of signals s n (t) is as illustrated in the detailed description of FIGs. 4A-4B.

[0046] FIG. 4A illustrates a graph 401 showing the change in the instant frequency f(t) with time for each of the plurality of transmission signals s n (t), when the base signal bs(t) is the continuous wave, in accordance with an example embodiment of the present invention. For instance, the graph 401 illustrates the change in the instant frequency f(t) for the plurality of transmission signals s n (t) when the base signal bs(t) corresponds to the continuous wave of a constant frequency of 150kHz.

[0047] As illustrated in the graph 401, x-axis of the graph 401 is time t and y-axis of the graph 401 is the instant frequency f(t) for the plurality of transmission signals s n (t). The graph 401 illustrates that the instant frequency f(t) of each of the plurality of transmission signals s n (t) (e.g., CH1 to CH16) is almost constant with time t, as the base signal bs(t) is the continuous wave of the constant frequency of 150kHz.

[0048] FIG. 4B illustrates a graph 403 showing the change in the instant frequency f(t) with time for each of the plurality of transmission signals s n (t), when the base signal bs(t) is the linear FM wave, in accordance with an example embodiment of the present invention. For instance, the graph 403 illustrates the change in the instant frequency f(t) for the plurality of transmission signals s n (t) when the base signal bs(t) corresponds to the linear FM wave whose frequency is linearly varying from 125kHz to 175kHz. In an example embodiment, the frequency range of the base signal bs(t) is selected in regard to a frequency range characteristic of transmission array 103. To that end, the target detection device 100 avoids research & development cost on the transmission array 103. As illustrated in the graph 403, x-axis of the graph 403 is time t and y-axis of the graph 403 is the instant frequency f(t) for the plurality of transmission signals s n (t). The graph 403 illustrates that the instant frequency f(t) of each the plurality of signals s n (t) (e.g., CH1 to CH16) is linearly varying with time t at the frequency range of 125kHz to 175kHz, as the base signal bs(t) is linear FM wave of the frequency range 125kHz to 175kHz. The transmission wave 105 transmitted from the transmission array 103 using the plurality of transmission signals s n (t) (e.g., CH1 to CH16) is further explained in the detailed description of FIG. 5.

[0049] FIG. 5 illustrates an exemplary scenario showing the transmission part 100a for transmitting the transmission wave 105, in accordance with an example embodiment of the present invention. The transmission part 100a includes the signal generator 101 and the transmission array 103 for transmitting the transmission wave 105. The signal generator 101 generates the plurality of transmission signals s n (t) as explained in the detailed description of FIGs. 2A-2C. For instance, the signal generator 101 generates each of the plurality of transmission signals s n (t) from the base signal bs(t) by phase shifting the phase of the base signal bs(t) by the phase shift amount θ n (t). Further, the signal generator 101 inputs each of the plurality of transmission signals s n (t) into one of the transmission elements 103a (not shown) of the transmission array 103. The transmission array 103 converts the plurality of transmission signals s n (t) into the transmission wave 105 as illustrated in FIG. 5. The transmission wave 105 may be the beam whose emission direction is changing in a direction 501 (e.g., in the vertical direction) with the time t in response to the change in the phase shift amount θ n (t) with time t. For instance, the transmission wave 105 may be the beam that starts at an emission direction -30 degree and ends at an emission direction +30 degree with varying time t. The change in the emission direction φ(t) of the transmission wave 105 with time t is further graphically illustrated in FIGs. 6A-6B.

[0050] FIG. 6A illustrates a graph 601 showing the change in the emission direction of the transmission wave 105 with time t, in accordance with an example embodiment of the present invention. As illustrated in the graph 601, x-axis of the graph 601 is time t and y-axis of the graph 601 is the emission direction φ(t). The graph 601 illustrates that the emission direction φ(t) of the transmission wave 105 is linearly changing with time t. For instance, the emission direction φ(t) of the transmission wave 105 changes linearly with time t, according to a linear function. In some other example embodiments, the emission direction φ(t) of the transmission wave 105 varies non-linearly with time t. For instance, the emission direction φ(t) may non-linearly vary with time t, as illustrated in FIG. 6B.

[0051] FIG. 6B illustrates a graph 603 showing the change in the emission direction of the transmission wave 105 with time t, in accordance with another example embodiment of the present invention. As illustrated in the graph 603, x-axis of the graph 603 is time t and y-axis of the graph 603 is the emission direction φ(t). The graph 603 illustrates that the emission direction φ(t) of the transmission wave 105 is non-linearly changing with time t. For instance, the emission direction φ(t) of the transmission wave 105 changes non-linearly with time t, according to an arcsin function (e.g. an inverse of a sine function). Therefore, the emission direction φ(t) of the transmission wave 105 changes either linearly or non-linearly with time t irrespective of whether the base signal bs(t) is the continuous wave or the linear FM wave. Further, the change in the emission direction φ(t) with respect to time t when the base signal bs(t) is the continuous wave is further graphically illustrated in FIG. 7.

[0052] FIG. 7 illustrates graphs 701, 703, 705, and 707 showing the change in the emission direction φ(t) with respect to time t when the base signal bs(t) is the continuous wave, in accordance with an example embodiment of the present invention. As illustrated in the graphs 701 and 705, x-axis of the graphs 701 and 705 are time t and y-axis of the graphs 701 and 705 are amplitude of the transmission wave 105. As illustrated in the graphs 703 and 707, x-axis of the graphs 703 and 707 are time t and y-axis are the instant frequency f(t). The graph 701 and the graph 703 illustrate the amplitude and the instant frequency f(t) of the transmission wave 105 respectively, when the transmission wave 105 is at the emission direction φ(t) = 0 degree. The graph 705 and the graph 707 illustrate the amplitude and the instant frequency f(t) of the transmission wave 105 respectively, when the transmission wave 105 is at the emission direction φ(t) = 20 degree. The graphs 701 and 705 illustrate that the emission direction of the transmission wave 105 changes with the time t. For instance, a peak amplitude of the transmission wave 105 of two different emission directions is appearing at two different time instances. The graphs 703 and 707 illustrate that the instant frequency (t) is constant for two different emission directions of the transmission wave 105. For instance, the instant frequency f(t) is constant for two different emission directions of the transmission wave 105, as the base signal bs(t) is the continuous wave of the constant frequency. Further, the change in the emission direction φ(t) with respect to time t when the base signal bs(t) is the linear FM wave is further graphically illustrated in FIG. 8.

[0053] FIG. 8 illustrates graphs 801, 803, 805, and 807 showing the change in the emission direction φ(t) with respect to time t when the base signal bs(t) is the linear FM wave, in accordance with an example embodiment of the present invention. According to some embodiments, when the base signal bs(t) corresponds to the FM wave, the emission direction φ(t) of the transmission wave 105 changes with respect to time t and the instant frequency f(t) of the transmission wave 105 also changes with respect to time t. As a result, the instant frequency f(t) of the transmission wave 105 changes with the emission direction φ(t) of the transmission wave 105.

[0054] As illustrated in the graphs 801 and 805, x-axis of the graphs 801 and 805 are the time t and y-axis of the graphs 801 and 805 are the amplitude of the transmission wave 105. As illustrated in the graphs 803 and 807, x-axis of the graphs 803 and 807 are the time t and y-axis of the graphs 803 and 807 are the instant frequency f(t). The graph 801 and the graph 803 illustrate the amplitude and the instant frequency f(t) of the transmission wave 105 respectively, when the transmission wave 105 is at the emission direction φ(t) = 0 degree. The graph 805 and the graph 807 illustrate the amplitude and the instant frequency f(t) of the transmission wave 105 respectively, when the transmission wave 105 is at the emission direction φ(t) = 20 degree. The graphs 801, 803, 805, and 807 illustrate that the emission direction φ(t) of the transmission wave 105 changes with respect to time t and the instant frequency f(t) of the transmission wave 105 changes with the emission direction φ(t). Therefore, each emission direction corresponds to a given frequency, and a unique direction-frequency relationship is thus established. For instance, a peak amplitude of the transmission wave 105 of different emission directions is appearing at different time instances and at different instant frequencies. The transmission wave 105 of different emission directions at different frequencies and at different time instances transmitted by the transmission array 103 is as illustrated in FIG. 9A.

[0055] FIG. 9A illustrates a diagram showing the transmission wave 105 transmitted by the transmission array 103, in accordance with an example embodiment of the present invention. The transmission array 103 having the plurality of the transmission elements 103a transmits the transmission wave 105 in response to the signal generator 101 generating the plurality of transmission signals s n (t) as explained in the detailed description of FIGs. 2A-2C. The transmission wave 105 is represented as beams 105a, 105b, 105c as depicted in FIG. 9A. In an embodiment, each of the beams 105a, 105b, and 105c of different emission direction φ(t) is transmitted at different time t and at different instant frequency f(t), when the base signal bs(t) is the FM wave. For instance, the transmission wave 105 is the beam 105a of the emission direction φ(t 1 ) transmitted at an instant frequency f(t 1 ) and at the first time t 1 . Further, when the time t changes from the first time t 1 to the second time t 2 , the transmission wave 105 changes its instant frequency (e.g., from f(t 1 ) to f(t 2 )) and change its emission direction (e.g., from φ(t 1 ) to φ(t 2 )) in the direction 501, which is represented by the beam 105b. Similarly, when the time t changes from the second time t 2 to a third time t 3 , the transmission wave 105 is represented by the beam 105c. To that end, the target detection device 100 controls the transmission wave 105 to propagate in the detection range using the phase shift amount θ n (t) applied to the base signal bs(t) and the instant frequency f(t) of the base signal. Therefore, the target detection device 100 controls the transmission wave 105 to propagate in the detection range with a frequency band that is similar to the frequency range (e.g., 50kHz (125kHz-175kHz)) of the base signal bs(t). Accordingly, the target detection device 100 uses a narrow frequency band to control the transmission wave 105 in the detection range, in comparison to currently available technologies.

[0056] In an alternate embodiment, each of the beams 105a, 105b, and 105c of different emission directions φ(t) are transmitted at different time instances and with the constant frequency, when the base signal bs(t) is the continuous wave. To that end, the target detection device 100 controls the transmission wave 105 with only the phase shift amount θ n (t) applied to the base signal bs(t) for propagating the transmission wave 105 in the detection range. In this case, the target detection device 100 controls the transmission wave 105 to propagate in the detection range with a frequency band of zero kHz (0kHz), as the base signal bs(t) is the continuous wave of the constant wave.

[0057] Therefore, the transmission wave 105 transmitted by the transmission array 103 is propagated in an angle range (i.e., the detection range) selected from the range +90 degree to -90 degree in a single transmission by phase shifting the phase of the base signal bs(t) by the phase shift amount θ n (t). Further, the target detection device 100 includes the reception array 109 having the plurality of reception elements 109a for receiving the reception wave 107. The reception wave 107 is the wave (also referred to echoes) reflected from the at least one target in response to transmitting the transmission wave 105. The transmission array 103 and the reception array 109 are arranged in different directions. In an example embodiment, the transmission array 103 and the reception array 109 are arranged perpendicular to each other as depicted in FIG. 9A. For instance, a direction of arrangement of the plurality of transmission elements 103a and a direction of arrangement of the plurality of reception elements 109a may be perpendicular. In an alternate embodiment, the transmission array 103 and the reception array 109 is arranged in parallel, or at some other angle. Further, a parallel arrangement of the transmission array 103 and the reception array 109 is as depicted in the FIG. 9B.

[0058] FIG. 9B illustrates a parallel arrangement of the transmission array 103 and the reception array 109, in accordance with an example embodiment of the present invention. As illustrated in FIG. 9B, the transmission array 103 and the reception array 109 are arranged in same direction. For instance, the direction of arrangement of the plurality of transmission elements 103a and the direction of arrangement of the plurality of reception elements 109a are similar. The transmission array 103 transmits the transmission wave 105 that is gradually changing its emission direction φ(t) in the direction 501 as explained in the detailed description of FIG. 9A. In some embodiments, the transmission array 103 having the plurality of transmission elements 103a is replaced by a single transceiver array 901 having a plurality of transceiver elements to obtain the parallel arrangement of the transmission array 103 and the reception array 109. To that end, the single transceiver array 901 is configured to transmit the transmission wave 105 and receive the reception 107 corresponding to the transmission wave 105. Further, a reception process for receiving the reception wave 107 corresponding to the transmission wave 105 is as explained in the detailed description of FIGs. 10A-10B.

[0059] FIG. 10A illustrates the reception process for receiving the reception wave 107 corresponding to the transmission wave when the transmission array 103 and the reception array 109 are perpendicularly arranged, in accordance with an example embodiment of the present invention. The reception wave 107 is the wave that is reflected from at least one target, in response to transmitting the transmission wave 105. As illustrated in FIG. 10A, the reception wave 107 corresponding to the transmission wave 105 approaches the reception array 109. To that end, the reception array 109 having the plurality of reception elements 109a receives the reception wave 107. Further, each reception element 109a of the reception array 109 converts the reception wave 107 into a reception signal. Further, by performing a phase control (beamforming) to the reception signal outputted from each reception element 109a, a narrow reception beam 1001 (also referred to as a reception beam 1001) is formed as depicted in FIG. 10A. For instance, the signal processing part 111 forms the reception beam 1001. Thus, the reception signals in an area where the reception beam 1001 and at least one of beams 107a, 107b, and 107c corresponding to the beams 105a, 105b, and 105c respectively intersect can be extracted. In an embodiment, a direction of the reception beam 1001 is changed in a direction 1003 (e.g., in the horizontal direction) by performing the phase controlling. Further, an incoming direction of the reception wave 107 is calculated by the signal processing part 111 (not shown) in a first dimension (i.e. in the direction 1003) from the direction of the reception beam 1001. For instance, the direction of the reception beam 1001 defines the incoming direction of the reception wave 107 in the first dimension.

[0060] Further, a plurality of different frequency components (also referred to as frequency reception signals) from the reception signals are extracted by the signal processing part 111. In an embodiment, each extracted frequency component defines an incoming direction of the reception wave 107 in a second dimension (i.e., in the direction 501). Indeed, as the emission direction corresponds to a given frequency and as the unique direction-frequency relationship is known by the signal processing part 111, extracting the frequency component from the reception signal enables to know the incoming direction of the reception wave 107. For instance, each extracted frequency component corresponds to a different incoming direction, since the transmission array 103 transmits the transmission wave 105 of beams of different directions at different frequencies, when base signal bs(t) is FM wave. Furthermore, a distribution of intensity data of the reception signals in the detection range where the reception beam 1001 intersects with each of the beams 107a, 107b, and 107c is obtained, by plotting data based on an intensity of the reception signal at a distance position determined by a delay time of the reflection wave 107 in a direction defined by an angle in the direction 501 corresponding to the extracted frequency and in a direction defined by an angle in the direction 1003 acquired by the beamforming. Then, volume data that is distributed three-dimensionally in the detection range in the direction 501 and in the direction 1003 is obtained, by changing the direction of the reception beam 1001 in the direction 1003 within the detection range and by acquiring the distribution of the intensity data at the respective directions of the reception beam 1001. Furthermore, visual data indicating a state of the at least one target is generated based on the obtained volume data. Therefore, transmitting different frequencies in different emission directions with the 1D transmission array 103, and receiving the reception wave 107 with the 1D reception array 109 different from the transmission array and oriented in a different direction to the transmission array 103, enables three-dimensional target detection.

[0061] FIG. 10B illustrates the reception process for receiving the reception wave 107 corresponding to the transmission wave when the transmission array 103 and the reception array 109 are arranged in parallel, in accordance with an example embodiment of the present invention. As illustrated in FIG. 10B, the reception wave 107 corresponding to the transmission wave 105 approaches the reception array 109. To that end, the reception array 109 having the plurality of reception elements 109a receives the reception wave 107. Further, the reception beam 1001 is formed by performing the phase control (beamforming) as explained in the detailed description of FIG. 10A. Since, the transmission wave 105 (e.g. the beams 105a, 105b, and 105c) and the reception beams 1001 are scanning the detection range in the same direction, a two-dimensional data set in the detection range is acquired by changing the direction of the reception beam 1001. For instance, the two-dimensional data set comprise distance data where the reception beam 1001 intersects with the reception wave 107 corresponding to the transmission wave 105 and direction data in which the reception beam 1001 is changing.

[0062] In this way, the target detection device 100 detects the targets for visualizing the underwater conditions in single transmission by using the narrow frequency band and the phase shift amount θ n (t) for controlling the transmission wave 105 to propagate in the detection range. Further, a detailed block diagram of the target detection device 100 for detecting the targets and generating visual data of the targets is as explained in the detailed description of FIG. 11A.

[0063] FIG. 11A is a block diagram of the target detection device 100 for detecting the targets, in accordance with an example embodiment of the present invention. The target detection device 100 includes the signal generator 101 and the transmission array 103 as illustrated and explained in the detailed description of FIGs. 2A-2C. Additionally, the target detection device 100 includes a transmission amplifier 1101 connected between the signal generator 101 and the transmission array 103. The transmission amplifier 1101 amplifies the plurality of transmission signals s n (t) outputted from the signal generator 101 and supplies it to each transmission element 103a.

[0064] Further, the target detection 100 includes a controller 1103. The controller 1103 includes an arithmetic processing circuit such as a CPU (Central Processing Unit), and a storage media such as a ROM (Read Only Memory), a RAM (Random Access Memory), and a hard disk drive. The controller 1103 may be comprised of an integrated circuit such as a FPGA (Field-Programmable Gate Array). The controller 1103 causes the signal generator 101 to generate the plurality of transmission signals s n (t) as explained in the detailed description of FIGs. 2A-2C. Further, when these generated plurality of transmission signals s n (t) are inputted into the transmission array 103, the transmission array 103 transmits the transmission wave 105 as the beams of different emission directions at different instant frequencies with time t according to the unique direction-frequency relationship. Therefore, the transmission wave 105 of FIG. 9A is formed. The controller 1103 also provides the unique direction-frequency relationship to the signal processing part 111.

[0065] The target detection device 100 may further comprise the reception array 109. In an embodiment, the reception array 109 is arranged in a different direction to the transmission array 103 and may be for example perpendicularly arranged to the transmission array 103 as depicted in FIG. 9A. In an alternate embodiment, the reception array 109 is arranged in parallel to the transmission array 103 as depicted in FIG. 9B, or at any other angle. The reception array 109 comprises the plurality of reception elements 109a. Each of the reception elements 109a is configured to receive the reception wave 107 and further configured to convert the reception wave 107 into the plurality of reception signals. The plurality of reception signals are outputted from the plurality of reception elements 109a to corresponding channels CH1-CHm.

[0066] The target detection device 100 further include a plurality of receiver parts 1105, a plurality of analog-to-digital converters (ADCs) 1107, the signal processing part 111, an image processing part 1109, and a display unit 1111, as a configuration for processing the plurality of reception signals outputted from each reception element 109a of the reception array 109 and for generating the visual data. The plurality of receiver parts 1105 are connected to the channels CH1-CHm, respectively. Each receiver part 1105 may be as explained in the detailed description of FIG. 11B.

[0067] FIG. 11B illustrates a block diagram of the receiver part 1105, in accordance with an example embodiment of the present invention. The receiver part 1105 is similar to reception part 100b of the target detection device 100 shown in FIG. 1. The receiver part 1105 includes a low noise amplifier (LNA) 1105a, a filter 1105b, a main amplifier 1105c, and an anti-aliasing filter 1105d. The LNA 1105a may amplify a low power reception signal outputted from the reception element 109a without degrading its signal-to-noise ratio. The filter 1105b removes an unnecessary band from the inputted reception signal. The main amplifier 1105c amplifies the reception signal to a level suitable for A / D conversion. The anti-aliasing filter 1105d removes a signal component at a band more than half of a sampling period of the A / D conversion.

[0068] Referring to FIG. 11A, the plurality of ADCs 1107 are associated with the plurality of receiver parts 1105, respectively. Each ADC 1107 converts the analog reception signal inputted from the corresponding receiver part 1105 into a digital signal at a given sampling period. The signal processing part 111 processes the reception signals of the channels CH1-CHm inputted from the plurality of ADCs 1107, respectively, to calculate the volume data of the reception signals that is distributed three-dimensionally over the detection range. The signal processing part 111 may be a single integrated circuit (FPGA etc.) together with the controller 1103.

[0069] The image processing part 1109 process the volume data inputted from the signal processing part 111 and generate the visual data for visualizing the state of the at least one target in the detection range. For instance, the image processing part 1109 performs operations such as a gain adjustment operation, an interference removal operation, a coordinate conversion (Spherical coordinate to Cartesian coordinate) operation, a pixel interpolation operation, a smoothing operation, a color conversion operation, and the like on the volume data to generate the visual data indicating the state of the at least one target. The image processing part 1109 may be embodied as a CPU, for example. The display unit 1111 may be comprised of a monitor for visualizing the underwater conditions according to the visual data inputted from the image processing part 1109.

[0070] FIG. 12A illustrates a block diagram of the signal processing part 111 for calculating the volume data, in accordance with an example embodiment of the present invention. The signal processing part 111 includes a plurality of digital filters 111a, a buffer 111b, a plurality of band-pass filters 111c, and a plurality of beam synthesizing parts 111d (which may also be referred to as beam forming parts 111d). The plurality of digital filters 111a are provided corresponding to the plurality of ADCs 1107 of FIG. 11A. The digital filter 111a may be a sharp digital filter for removing signals of unnecessary bands in the reception signal. The buffer 111b temporarily holds the reception signals of the channels CH1-CHm outputted from the plurality of digital filters 111a. The buffer 111b sequentially supplies the reception signals for one scan to the plurality of band-pass filters 111c. Further, the buffer 111b discards the reception signals after supplying the reception signals to the plurality of band-pass filters 111c. The plurality of band-pass filters 111c extract the plurality of different frequency components (frequency receptions signals) at frequencies F 1 -F n from the reception signals of one particular scan. The frequencies F 1 -F n correspond to the instant frequencies in the frequency range of the base signal bs(t). As each emission direction φ(t) has a different instant frequency f(t) as established according to the unique direction-frequency relationship, frequency characteristics of each band-pass filter 111c are designed to match a frequency band in a given emission direction. To that end, each band-pass filter 111c corresponds to that given emission direction. In some embodiments, the plurality of band-pass filters 111c may be replaced with a plurality of compression filters (also referred to as matched filters) for extracting the plurality of frequency components. To that end, each compression filter corresponds to a given emission direction as established according to the unique direction-frequency relationship and frequency characteristics of compression filter are designed to match a frequency band in that given emission direction. In case of the compression filter, the frequency band of the filter is generally larger than for a band-pass filter but the center frequency of the frequency band used for the design of each compression filter may be used as an entry point in the direction-frequency relationship to make the conversion from frequency to incoming direction. The use of plurality of compression filters enables providing a better range resolution. Further, the plurality of band-pass filters 111c (or the plurality of compression filters) supply the extracted plurality of frequency components to the plurality of beam synthesizing parts 111d, respectively.

[0071] The plurality of beam synthesizing parts 111d are provided corresponding to the plurality of band-pass filters 111c. As each beam synthesis part of the plurality of beam synthesis parts 111d corresponds to a given frequency within the frequencies F 1 -F n , each beam synthesis part corresponds to a given incoming direction of the reception wave 107 according to the unique direction-frequency relationship. The beam synthesizing part 111d forms the reception beam 1001 by the beam forming based on the phase control and separate the frequency component (i.e., the incoming direction of the reception wave 107) in the direction 501 at a given resolution. Thus, the frequency component in the area where the reception beam 1001 intersects with the at least one of the beams 107a, 107b, and 107c may be extracted. The extracted frequency component changes in the intensity on the time axis according to the intensity of the reflection wave 107 from the area where the reception beam 1001 intersects with the at least one of the beams 107a, 107b, and 107c. The time axis may correspond to a distance from the reception array 109 in the area where the reception beam 1001 intersects with the at least one of the beams 107a, 107b, and 107c. Therefore, the distribution of the intensity data in the area where the reception beam 1001 intersects with the at least one of the beams 107a, 107b, and 107c is acquired by mapping each intensity on the time axis at the corresponding distance position from the reception array 109 in the area where the reception beam 1001 intersects with the at least one of the beams 107a, 107b, and 107c. Thus, the volume data where the intensity data is distributed three-dimensionally over the detection range may be acquired by integrating the distributions of the intensity data in each direction.

[0072] FIG. 12B illustrates a block diagram of the signal processing part 111 for calculating the volume data, in accordance with another example embodiment of the present invention. In this example configuration, the plurality of band-pass filters 111c in the example configuration of FIG. 12A are replaced by a Fast Fourier Transform (FFT) 111e and a frequency extraction part 111f. The FFT 111e calculates a frequency spectrum from the reception signals for one scan of the channels CH1-CHm. The frequency extraction part 111f may extract the frequency components at the frequencies F 1 -F n from the frequency spectrum of each channel calculated by the FFT 111e and supply the extracted frequency components to the corresponding beam synthesizing part 111d. Processing of the plurality of beam synthesizing parts 111d may be same as explained in the FIG. 12A. Further, the use of the FFT 111e and the frequency extraction part 111f enables to accurately extract the plurality of frequency components (i.e., the incoming direction of the reception wave 107) from the reception signals.

[0073] Also, according to this configuration, by integrating the distributions of the intensity data in each direction, outputted from beam synthesizing parts 111d, the volume data where the intensity data is distributed three-dimensionally over the detection range is acquired as explained in the detailed description of FIG. 12A.

[0074] FIG. 12C illustrates a block diagram of the signal processing part 111 when the base signal bs(t) is the continuous wave, in accordance with yet another example embodiment of the present invention. In this example configuration, the plurality of band-pass filters 111c in the example configuration of FIG. 12A are replaced by a single band-pass filter 111g and further the plurality of beam synthesizing parts 111d in the example configuration of the FIG. 12A are replaced by a single beam synthesizing part 111h, as the instant frequency f(t) of the base signal bs(t) is the constant frequency when the base signal bs(t) correspond to the continuous wave. Processing of the single band-pass filter 111g is same as the band-pass filter 111c explained in the detailed description of FIG. 12A. For instance, the single band-pass filter 111g extracts a single frequency component from the receptions signals, as the base signal bs(t) is the continuous wave. Processing of the single beam synthesizing part 111h is same as the beam synthesizing part 111d as explained in the detailed description of FIG. 12A. For instance, the distribution of intensity data are acquired in each direction defined by the direction 1003 by changing the direction of the reception beam 1001.

[0075] FIG. 13A illustrates a target detection method 1300a for transmitting the transmission wave 105, in accordance with an example embodiment of the present invention. The target detection method 1300a may be used in conjunction with the target detection device 100 described in the detailed description of FIG. 11A. Starting at step 1301, the target detection method 1300a includes generating the plurality of transmission signals s n (t). In an example embodiment, the target detection method 1300a includes phase shifting the phase of the base signal bs(t) by the phase shift amount θ n (t) that changes over the time t for generating each of the plurality of transmission signals s n (t). For instance, the signal generator 101 of the target detection device 100 generates the plurality of transmission signals s n (t) as explained in the detailed description of FIGs. 2A-2C. Further, in some example embodiments, the phase shift amount θ n (t) applied to each of the plurality of transmission signal s n (t), relative to the base signal bs(t), continuously varies with time t and the phase difference Δθ between any two transmission signals of the plurality of transmission signals may continuously vary with time t.

[0076] At step 1303, the target detection method 1300a includes inputting each transmission signal into one of the plurality of transmission elements 103a. For instance, the signal generator 101 inputs each transmission signal into one of the plurality of transmission elements 103a.

[0077] At step 1305, the target detection method 1300a includes transmitting the transmission wave 105 from the plurality of transmission elements 103a. For instance, in response to inputting the plurality of transmission signals s n (t) into the plurality of transmission elements 103a, the transmission array 103a may transmit the transmission wave 105 as illustrated in FIG. 9A.

[0078] On implementing the target detection method 1300a on the target detection device 100, the transmission wave 105 of FIG. 9A is formed. For instance, the transmission wave 105 is the beams 105a, 105b, and 105c of different emission directions at different time instances and at different frequencies as explained in the detailed description of FIG. 9A. Accordingly, the target detection device 100 that implements the target detection method 1300a transmits the transmission wave 105 in the detection range. Further, the target detection device 100 that implements the target detection method 1300a enables to control the detection range of the transmission wave 105 using the phase shift amount θ n (t) applied to the base signal bs(t), as each transmission signal is generated by phase shifting the phase of the base signal bs(t) by the phase shift amount θ n (t). Therefore, the frequency of the base signal bs(t) may be selected independently without considering the detection range. Accordingly, the target detection device 100 that implements the target detection method 1300a transmits the transmission wave 105 in the detection range for detecting the targets in the single transmission using the narrow frequency band that is similar to the frequency band of the base signal bs(t).

[0079] FIG. 13B illustrates a target detection method 1300b for processing the reception wave 107, in accordance with an example embodiment of the present invention. The target detection method 1300b may be used in conjunction with the target detection device 100 described in the detailed description of FIG. 11A.

[0080] Starting at step 1307, the target detection method 1300b includes receiving the reception wave 107 from at least one target. For instance, the reception array 109 receives the reception wave 107 from at least one target. The reception wave 107 is the wave reflected from the at least one target, in response to transmitting the transmission wave 105.

[0081] At step 1309, the target detection method 1300b includes converting the reception wave 107 into the plurality of reception signals. For instance, each reception element 109a of the reception array 109 converts the reception wave 107 into the reception signal.

[0082] At step 1311, the target detection method 1300b includes calculating the incoming direction of the reception wave 107 in a first dimension by performing the beamforming on the reception signals. For instance, the signal processing part 111 calculates the incoming direction of the reception wave 107 in the direction 1003 by phase controlling the reception beam 1001 as explained in the detailed description of FIG. 10A.

[0083] At step 1313, the target detection method 1300b includes extracting the plurality of different frequency components from the reception signals. For instance, the signal processing part 111 extracts the plurality of different frequency components from the reception signals as explained in the detailed description of FIG. 10A. As each emission direction φ(t) has a different instant frequency f(t) as established according to the unique direction-frequency relationship, each frequency component corresponds to a different incoming direction in the second dimension (e.g., in the direction 501).

[0084] At step 1315, the target detection method 1300b includes calculating the incoming direction of the reception wave 107 in the second dimension, based on the extracted plurality of different frequency components and the unique direction-frequency relationship. For instance, the signal processing part 111 calculates the incoming direction of the reception wave 107 in the direction 501, based on the extracted plurality of different frequency components. In an example embodiment, each frequency component defines the incoming direction in the direction 501, as each emission direction φ(t) has a different instant frequency f(t) as established according to the unique direction-frequency relationship.

[0085] At step 1317, the target detection method 1300b includes calculating the volume data over the detection range, based on the incoming direction of the reception wave 107 in the first dimension and the second dimension. For instance, the signal processing part 111 obtains the distribution of the intensity data by mapping the intensity data of the reception signal in the detection range and calculate the volume data over the detection range based on the distribution of the intensity data as explained in the detailed description of FIG. 10A.

[0086] At step 1319, the target detection method 1300b includes generating the visual data based on the calculated volume data. For instance, the image processing part 1109 generates the visual data based on the volume data. The visual data may indicate the state of the at least one target.

[0087] At step 1321, the target detection method 1300b includes displaying the generated visual data. For instance, the visual data is displayed via the display unit 1111 for visualizing the underwater conditions.

[0088] On implementing the target detection method 1300b on the target detection device 100, the target detection device 100 processes the reception wave 107 corresponding to the transmission wave 105. Since the transmission wave 105 corresponds to the beams 105a, 105b, and 105c of different emission directions at different time instances and at different frequencies, the target detection device 100 that implements the target detection method 1300b smoothly detect the targets. For instance, echoes (e.g., beams of the transmission wave 105 reflected from the at least one target) may be smoothly separated to detect the targets, as the transmission wave 105 corresponds to the beams 105a, 105b, and 105c of different emission directions at different time instances and at different frequencies. For instance, transmitting different frequencies in different emission directions with the 1D transmission array 103, and receiving the reception wave 107 with the 1D reception array 109 different from the transmission array 103 and oriented in a different direction to the transmission array 103, enables three-dimensional target detection without the need for a 2D transmission array or a 2D reception array. Since the transmission wave 105 is transmitted using the narrow frequency band, the target detection device 100 that implements the target detection method 1300b allows visualizing of the underwater conditions based on the detected targets using the narrow frequency band.

[0089] FIG. 14 illustrates a working environment of the target detection device 100 for detecting the targets, in accordance with an example embodiment of the present invention. In an embodiment, the target detection device 100 is a sonar for detecting the targets in the water body. To that end, a transducer 1401 is installed on bottom of a vessel 1403. The transducer 1401 includes the transmission array 103 and the reception array 109. The transmission array 103 transmits the transmission wave 105 underwater in response to generating the plurality of transmission signals s n (t) by the signal generator 101. For instance, an acoustic wave (e.g., an ultrasonic wave) is transmitted as the transmission wave 105 by the transmission array 103 of the transducer 1401.

[0090] Configurations of FIG. 11A other than the transmission array 103, the reception array 109, and the display unit 1111 is provided to a control device (not shown in figure) installed in a control room 1403a of the vessel 1403. The display unit 1111 is installed in the control room 1403a, separately from the control device. The display unit 1111 is also be integrally provided with the control device. Further, a detection image indicative of a situation of a fish school 1405, a seabed 1407, and the like are displayed on the display unit 1111. Therefore, a user can grasp the underwater conditions. In some embodiments, four transducers 1401 which are directed forward, rearward, leftward, and rightward are installed on the bottom of the vessel 1403. In this case, each transducer 1401 comprising the transmission array 103 and the reception array 109 are configured as explained in the detailed description of FIG. 11A. To that end, a detection image of entire underwater from the vessel 1403 may be displayed on the display unit 1111.

[0091] In an alternate embodiment, the target detection device 100 is a radar for detecting targets in air. To that end, a transducer 1409 is installed in an upper part of the control room 1403a, as illustrated in the FIG. 14. The transducer 1409 includes the transmission array 103 and the reception array 109. The transmission array 103 transmits the transmission wave 105 in the air in response to generating the plurality of transmission signals s n (t) by the signal generator 101. For instance, a radio wave is be transmitted as the transmission wave 105 by the transmission array 103 of the transducer 1409. Further, a circuitry configuration for the transducer 1409 is installed in the control room 1403a, similarly as explained for the transducer 1401. Further, a detection image indicative of a situation of an obstacle and a flock of birds may be displayed on the display unit 1111. Accordingly, the user may grasp the situation in the air. In some embodiments, the transducer 1409 is installed on each of front, rear, right and left side surfaces of the control room 1403a. In this case, each transducer 1409 comprising the transmission array 103 and the reception array 109 is configured as explained in the detailed description of FIG. 11A. To that end, a detection image of an airspace surrounding the vessel 1403 may be displayed on the display unit 1111.

Claims

1. A target detection device (100), comprising: a transmission array (103) having a plurality of acoustic transmission transducer elements (103a); a signal generator (101) configured to: generate a plurality of transmission signals, wherein to generate each transmission signal of the plurality of transmission signals, the signal generator (101) is further configured to change a phase of a same base signal by a phase shift amount that changes continuously over time; and input to each transmission transducer element of the plurality of acoustic transmission transducer elements (103a) a corresponding generated transmission signal of the plurality of transmission signals; and a reception array (109) having a plurality of reception elements (109a), wherein the reception array (109) is configured to receive a reception wave (107) from a target, and each reception element (109a) is configured to convert the reception wave (107) into a corresponding reception signal; wherein the phase changes are such that an emission direction of a transmission wave (105) transmitted by the transmission array (103) changes over time, and a frequency of the transmission wave (105) changes over time with the change in the emission direction of the transmission wave (105) over time.

2. The target detection device (100) of claim 1, wherein: a first phase shift amount (θ1(t1)) of a first transmission signal (s1(t)) of the plurality of transmission signals at a first time (t1) is different from a second phase shift amount (θ1(t2)) of the first transmission signal (s1(t)) at a second time (t2), the first phase shift amount (θ1(t1)) and the second phase shift amount (θ1(t2)) are measured with respect to the phase of the base signal, and the first time (t1) is different from the second time (t2).

3. The target detection device (100) of claim 2, wherein: a third phase shift amount (θ2(t1)) of a second transmission signal (s2(t)) of the plurality of transmission signals at the first time (t1) is different from the first phase shift amount (θ1(t1)) of the first transmission signal (s1(t)) at the first time (t1), the third phase shift amount (θ2(t1)) and the first phase shift amount (θ1(t1)) are measured with respect to the phase of the base signal, and the second transmission signal (s2(t)) is different from the first transmission signal (s1(t)).

4. The target detection device (100) of claim 3, wherein a first phase difference (Δθ1) between the first transmission signal (s1(t)) and the second transmission signal (s2(t)) at the first time (t1) is different from a second phase difference (Δθ2) between the first transmission signal (s1(t)) and the second transmission signal (s2(t)) at the second time (t2).

5. The target detection device (100) of any of claims 1-4, wherein the emission direction of the transmission wave (105) transmitted by the transmission array (103) changes over said time in response to the change in the phase shift amount over said time.

6. The target detection device (100) of claim 5, wherein a carrier of the base signal is a frequency modulated carrier.

7. The target detection device (100) of any of claims 1-6, wherein the emission direction of the transmission wave (105) changes non-linearly with time.

8. The target detection device (100) of any of claims 1-7, further comprising a processing circuitry (111) configured to calculate an incoming direction of the reception wave (107) in a first dimension by performing beam forming based on the received reception signals.

9. The target detection device (100) of claim 8, wherein the processing circuitry (111) is further configured to extract frequency components from the reception signals to obtain a second incoming direction of the reception wave (107), different from the incoming direction, based on a unique direction-frequency relationship between the emission directions of the transmission wave (105) and frequency, and to generate 3D volume data based on the received reception signals, the incoming direction and the second incoming direction.

10. The target detection device (100) of claim 8 or 9, wherein the processing circuitry (111) is further configured to: extract a plurality of different frequency components from the reception signals, wherein each frequency component corresponds to a different incoming direction in a second dimension, wherein the second dimension is different than the first dimension; and calculate an incoming direction of the reception wave (107) in the second dimension, based on the extracted plurality of different frequency components.

11. The target detection device (100) of any of claims 1-10, wherein directions of arrangement of the plurality of transmission acoustic transducer elements (103a) and the plurality of reception elements (109a) are perpendicular.

12. The target detection device (100) of any of claims 1-11, wherein the target detection device (100) is a sonar that detects underwater targets.

13. A target detection method (1300a), comprising: generating (1301) a plurality of transmission signals, wherein for generating each transmission signal of the plurality of transmission signals the target detection method (1300a) further comprises phase shifting a phase of a same base signal by a phase shift amount that changes continuously over time; inputting (1303) a corresponding generated transmission signal of the plurality of transmission signals into each of a plurality of acoustic transmission transducer elements (103a); transmitting (1305) a transmission wave (105) from the plurality of acoustic transmission transducer elements (103a); and receiving a reception wave (107) from a target using a plurality of reception elements (109a), wherein each reception element (109a) converts the reception wave (107) into a corresponding reception signal; wherein the phase changes are such that an emission direction of the transmission wave (105) transmitted by the acoustic transmission transducer elements (103a) changes over time, and a frequency of the transmission wave (105) changes over time with the change in the emission direction of the transmission wave (105) over time.

14. The target detection method (1300a) of claim 13, wherein a phase difference between any two transmission signals of the plurality of transmission signals varies continuously over the time.