radar equipment

Abstract

To provide a radar device to be easily mounted and capable of correctly obtaining information on an object even when a plurality of objects is present.SOLUTION: In a radar device 1, when a code obtained by encoding an appearance pattern of a peak on a Doppler frequency axis expected while an object is at a standstill is defined as an assigned code, a processing section 6 sets a correspondence with respective transmission antennas 3a so as to generate the peak associated with each one of transmission signals in a bin corresponding to "1" of the assigned code. A modulation section 22 performs phase shift modulation following a linear block code as the assigned code.SELECTED DRAWING: Figure 1

Description

Technical Field

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[0001] The present disclosure relates to a radar device that transmits radio waves from a plurality of antennas to detect an object.

Background Art

[0002] As a method for improving the resolution of a radar device, there is a MIMO (Multi-Input Multi-Output) technique for transmitting radio waves from a plurality of transmitting antennas. In this MIMO technique, since it is necessary to separate the transmission signals from each transmitting antenna in order to detect an object, for example, by Doppler division multiplexing, phase shift modulation is performed using different phase shift amounts for each transmitting antenna, and each transmission signal is separated as different signal components on the Doppler frequency axis. And, for example, in Patent Document 1, it has been proposed to improve the accuracy of identifying a plurality of transmission signals from a received signal by making the number of transmitting antennas smaller than the number of phases used for modulation.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, as also shown in, for example, Patent Document 1, depending on the speed of an object, so-called folding may occur in which the position of a peak shifts on the Doppler frequency. At this time, if the folded peak overlaps with the peak of another object, the transmission signal cannot be separated, and there is a risk that information about the object cannot be accurately obtained, such as the speed of the object cannot be accurately estimated or the angle measurement accuracy deteriorates.

[0005] In this case, it is conceivable to reduce the overlap when multiple objects are present by making the intervals between the sets of peaks corresponding to each transmitted signal on the Doppler frequency all different, like a Golomb ruler. However, since a large number of phases are required to perform phase shift modulation in a way that results in a Golomb ruler, it is practically difficult to implement.

[0006] This disclosure is made in view of the circumstances described above, and its purpose is to provide a radar device that is easy to implement and can accurately obtain information about objects even when multiple objects are present. [Means for solving the problem]

[0007] A radar device (1) according to one aspect of the present disclosure comprises: a transmitting antenna unit (3) having a plurality of transmitting antennas (3a); an oscillator unit (21) that generates a common signal of continuous waves; a modulation unit (22) that generates a plurality of transmitting signals input to the plurality of transmitting antennas by performing phase shift modulation on each of a plurality of branch signals obtained by branching the common signal to the same number of transmitting antennas, each of which rotates the phase by a different amount of phase rotation; a receiving antenna unit (4) having one or more receiving antennas (4a); a receiving unit (5) that generates a received code that encodes the appearance pattern of peaks on the Doppler frequency axis for each of the one or more received signals received by the receiving antenna unit; and a processing unit (6) that generates information about an object that has reflected radiation waves from the transmitting antenna unit based on the received code generated by the receiving unit, wherein if the expected appearance pattern of peaks on the Doppler frequency axis when the object is stationary is encoded as an assignment code, the modulation unit performs phase shift modulation according to a linear block code as the assignment code. This makes implementation easy and allows for accurate acquisition of object information even when multiple objects are present. [Brief explanation of the drawing]

[0008] [Figure 1] This figure schematically shows an example of the configuration of a radar device according to the first embodiment. [Figure 2] A diagram showing an example of antenna placement and an example of assigned and received codes. [Figure 3] A schematic diagram illustrating an example of assignment code generation in Dopplerabine. [Figure 4] Diagram illustrating the object detection process flow. [Figure 5] This diagram illustrates the configuration of the processing unit and the calculation flow according to the third embodiment. [Figure 6] This diagram illustrates the configuration of the processing unit and the calculation flow according to the fourth embodiment. [Figure 7] This diagram illustrates the configuration of the processing unit and the calculation flow according to the fifth embodiment. [Figure 8] This diagram illustrates the configuration of the processing unit and the calculation flow according to the sixth embodiment. [Figure 9] This diagram illustrates the configuration of the processing unit and the calculation flow according to the seventh embodiment. [Modes for carrying out the invention]

[0009] Several embodiments will be described below with reference to the drawings. Parts that are substantially common to each embodiment will be denoted by the same reference numerals.

[0010] (First Embodiment) The first embodiment will be described below. The radar device 1 shown in Figure 1 is assumed to be mounted on a vehicle and used to obtain information about various objects present around the vehicle. The radar device 1 comprises a transmitting unit 2, a transmitting antenna unit 3, a receiving antenna unit, a receiving unit 5, and a processing unit 6. The transmitting antenna unit 3 has transmitting antennas 3aM, ranging from M transmitting antennas 3a1 to M transmitting antennas 3aM, as shown in Figure 2 as an example of antenna arrangement. Here, M is an integer of 2 or more. Each transmitting antenna 3a is arranged in a line along a predetermined arrangement direction at a predetermined interval.

[0011] The receiving antenna section 4 has receiving antennas 4aN, ranging from N receiving antennas 4a1 to N receiving antennas 4aN, as shown in the example of the transmitting side arrangement. Here, N is an integer of 1 or more. When multiple receiving antennas 4a are provided, they are arranged at different intervals from the transmitting antennas 3a and along the same direction as the arrangement direction of the transmitting antennas 3a.

[0012] Now, let's assume, for example, that the object to be detected is located in a direction tilted by θ with respect to the front direction of the transmitting antenna unit 3 and the receiving antenna unit 4. In this case, as is well known, the receiving antenna 4a1 receives signals transmitted from transmitting antenna 3a1, transmitting antenna 3a2, and transmitting antenna 3aM. Similarly, the other receiving antennas 4a also receive signals transmitted from their respective transmitting antennas 3a.

[0013] This creates a virtual array of a total of M × N receiving antennas 4a, each positioned at different distances from a single reference receiving antenna 4a. As a result, an angular resolution equivalent to that of a system with one transmitting antenna and M × N receiving antennas can be obtained.

[0014] As shown in Figure 1, the transmitting unit 2 comprises an oscillator 21 and a modulation unit 22. The oscillator 21 generates a common signal of a continuous wave and outputs the generated common signal to the modulation unit 22.

[0015] The modulation unit 22 splits the common signal generated by the oscillation unit 21 to generate M branch signals, the same number as the transmitting antenna 3a. Specifically, the modulation unit 22 sets different phase rotation amounts for each of the M branch signals and generates M transmission signals by performing phase shift modulation, which rotates the phase of the branch signals by the set phase rotation amount.

[0016] For example, let the number of phases used in phase shift keying be P, where P is an integer greater than M, and let p = 0, 1, 2, ··· P - 1. Then, the modulation unit 22 performs phase shift keying using P phase rotation amounts represented by a phase rotation amount (Δφ) = p × 360° / P. However, since P > M, when phase shift keying is performed, not all of the P phase rotation amounts are used, but only a part of them is used.

[0017] Also, the modulation unit 22 performs phase shift keying such that the assigned code becomes a linear cyclic block code, details of which will be described later. Here, the assigned code is obtained by encoding the appearance pattern of peaks on the Doppler frequency axis that is expected when an object existing within the measurement range is stationary. Also, the appearance pattern of peaks is determined by the phase assignment to each transmission signal. For example, when the number of phases is P and the number of transmission antennas 3a is M, the assigned code is represented as a code with a code length of P bits, where M bits of them are "1" and the remaining P - M bits are "0". For example, when the number of transmission antennas 3a is 2 and the number of phases is 5, a 5-bit code such as "11000" can be set as the assigned code.

[0018] The receiving unit 5 generates a received code obtained by encoding the appearance pattern of peaks on the Doppler frequency axis for each of the N received signals output from each receiving antenna 4a of the receiving antenna unit 4, and outputs it to the processing unit 6. Here, the received code is obtained by encoding the appearance pattern obtained from the peak detection result on the Doppler frequency axis of the actual received signal. For example, when the number of phases is P and the number of transmission antennas 3a is M, the received code is represented as a code with a code length equal to the number of phases used in phase shift keying, where M bits of the P bits are "1" and the remaining P - M bits are "0".

[0019] For example, as shown as an example in FIG. 2, when phase shift modulation is performed with the assigned code "11000" set, in a distance-velocity map where the vertical axis is distance and the horizontal axis is the velocity that can be uniquely determined based on the Doppler frequency, peaks are detected at M out of P divided points in the Doppler observation range. Therefore, for example, the received code received when there is no object will have a peak detected at the position of the black circle. And by corresponding the peak position to "1" and the position where there is no peak to "0", a 5-bit code of "11000" can be obtained as the received code.

[0020] The processing unit 6 is composed of a microcomputer having a CPU 61 and a memory 62 such as a RAM or a ROM, for example. The processing unit 6 controls the entire radar device 1 by executing a program 63 stored in the memory 62 by the CPU 61. Further, although details will be described later, the processing unit 6 causes phase shift modulation in which the assigned code becomes a linear cyclic block code to be performed in the modulation unit 22, and generates information on an object based on the cross-correlation between the assigned code and the received code. At this time, various data used for operations such as the number of phases, the assigned code, or the cross-correlation are stored in the memory 62 as a database 64.

[0021] Note that the processing unit 6 may be composed of one microcomputer or may be composed of a plurality of microcomputers. Also, the method for realizing the functions of the processing unit 6 is not limited to software, and one or all of its functions may be realized by using one or a plurality of hardware components.

[0022] Next, the operations and effects of the above-described configuration will be described. As mentioned above, in radar device 1 utilizing MIMO technology, it is necessary to separate the transmitted signals from each transmitting antenna 3a in order to detect an object. Separating transmitted signals means identifying which transmitting antenna 3a's radiation wave was reflected from the received signal. In this case, for example, the accuracy of identifying multiple transmitted signals from the received signal can be improved by reducing the number of transmitting antennas to fewer than the number of phases used for modulation.

[0023] However, depending on the velocity of objects within the measurement range, so-called aliasing may occur, where the position of the peak shifts on the Doppler frequency. As a result, the aliased peak may overlap with the peaks of other objects, potentially making it impossible to separate the transmitted signals. When the transmitted signals cannot be separated, it becomes impossible to accurately estimate the velocity of the objects, and the accuracy of angle measurement deteriorates, making it impossible to obtain accurate information about the objects.

[0024] In this case, it is conceivable to reduce the overlap to one when multiple objects are present by making the intervals between the sets of peaks corresponding to each transmitted signal on the Doppler frequency all different, like a Golomb ruler. However, the Golomb ruler has the problem that the number of phases required increases as the number of multiplexed transmitted signals increases. For example, when multiplexing 12 transmitted signals, the length of the Golomb ruler becomes 85, so at least twice that number of phases, 170, is required. However, it is currently difficult to implement such a number of phases.

[0025] Therefore, the radar device 1 is designed to be easy to implement and to be able to accurately obtain information about objects even when multiple objects are present, as described below. In other words, the radar device 1 performs phase shift modulation in the modulation unit 22 based on an assigned code that is easy to implement and can accurately obtain information about objects even when multiple objects are present.

[0026] First, let's explain the conditions required for the assigned code. For example, suppose there are two objects within the measurement range, one of which does not exhibit aliasing, while the other exhibits aliasing, and the result is obtained as a distance-velocity map. In this case, if radar measurements were performed using phase shift modulation based on a certain assigned code, the actual distance-velocity map obtained would be the result of a logical OR operation between the assigned code without aliasing and the assigned code that has undergone one cyclic shift. Hereafter, the logical OR operation will be referred to as the OR operation. In that case, in order to separate each transmitted signal, it is desirable that the assigned code be one that satisfies the following conditions.

[0027] 1. The correspondence between "1" and "1" should be minimal between the cyclically shifted codes. In other words, the original code and the cyclically shifted code should have as many combinations of "1" and "0" as possible at the same bit position. Note that locations where "1" and "1" correspond correspond to peak overlap. 2. The result of the OR operation must be unique. In other words, there must be few combinations that produce the same result as the OR operation.

[0028] Here, we consider linear cyclic block codes as a code that may satisfy the above conditions. A linear cyclic block code, for example, if the code length is 8 bits, uses only specific codes from a set of 256 codes such that their Hamming distances from each other are large. The codes selected in this case become the codeword.

[0029] Linear cyclic block codes have the characteristic of cyclicity, where the cyclic shift of a codeword also becomes a codeword. Furthermore, a large Hamming distance means that there are few correspondences between "1" and "1", and between "0" and "0", which means that there is less overlap between peaks on the Doppler frequency axis. Therefore, similar to selecting a so-called error correction code, it can be expected that the overlap of peaks on the Doppler frequency axis can be reduced by selecting a linear cyclic block code with a large Hamming distance as the assigned code. For this reason, radar device 1 performs phase shift modulation using a linear cyclic block code with cyclicity as the assigned code.

[0030] In this case, the assigned code is one in which, as described above, if the number of transmitting antennas 3a is M, the M bit is "1" and the PM bit is "0". For example, if the number of transmitting antennas 3a1 is M=4, then P=8 can be selected as the phase number to obtain a linear cyclic block code that has 4 bits of "1". This phase number should be appropriately selected within the range in which the modulation unit 22 can perform phase shift modulation.

[0031] Now, if we select P=8 as the phase number, we can set "10001011" as the assigned code for a linear cyclic block code. Note that "10001011" indicates that in an 8-bit binary number, the most significant bit is "1", followed by "0", and the least significant bit is "1".

[0032] Then, as shown in Figure 3, radar device 1 performs phase shift modulation so that a peak associated with each transmitted signal occurs in the bin corresponding to the assigned code "1" when viewing the Doppler bins for each Nd / P with a Doppler bin number (Nd=256). In Figure 3, the blacked-out bins correspond to the assigned code "1", and the shaded blocks correspond to the assigned code "0".

[0033] Specifically, the processing unit 6 of the radar device 1 repeatedly executes the object detection process shown in Figure 4. First, the processing unit 6 obtains an assigned code (S1). In this embodiment, the assigned code is pre-set and stored in the database 64. Therefore, in step S1, the processing unit 6 reads the assigned code from the database 64.

[0034] Next, the processing unit 6 sets the correspondence with each transmitting antenna 3a so that a peak associated with each transmitted signal occurs in the bin corresponding to the assigned code "1" (S2). For example, the processing unit 6 sets the phase rotation amount for each transmitted signal when performing phase shift modulation to correspond to each transmitting antenna 3a such that transmitting antenna 3a1 corresponds to bin "0", transmitting antenna 3a2 corresponds to bin "128", transmitting antenna 3a3 corresponds to bin "192", and transmitting antenna 3a4 corresponds to bin "255". The correspondence with each transmitting antenna 3a may also be set in advance and stored as a database 64.

[0035] Then, the processing unit 6 determines whether the predetermined measurement start timing has arrived (S3). If it determines that it is not the measurement start timing (S3:NO), it waits. On the other hand, if the processing unit 6 determines that it is the measurement start timing (S3:YES), it performs radar measurement (S4). In this step S4, the processing unit 6 operates the transmitting unit 2 for a predetermined measurement period according to the set conditions, outputs radiated waves from each transmitting antenna 3a, and receives reflected waves from the object in the receiving unit 5.

[0036] In this case, if the assigned code was "10001011", the cyclically shifted code obtained by aliasing would be "11000101", and the minimum Hamming distance between them would be 3. In other words, in this embodiment, the modulation unit 22 performs phase shift modulation such that the minimum Hamming distance between the assigned code and the group of codes consisting of the cyclic shift of the assigned code is 3 or more. The group of codes consisting of the cyclic shift corresponds to the set of expected values ​​of the actual received codes.

[0037] Next, the processing unit 6 analyzes the interphase relationship between the assigned code and the received code (S5). This received code can be obtained, for example, by performing a two-dimensional Fourier transform (2DFFT) on the actually received signal and then performing peak detection (CFAR). In other words, the processing unit 6 estimates the circumstances under which the received code was obtained from the relationship between the known assigned code and the received code, which is the actual measurement result, and verifies the accuracy of the estimation, that is, the reliability of the separation.

[0038] For example, if the assigned code is "10001011" and the received code is "11001111", the received code matches the result of an OR operation between the assigned code and the code obtained by cyclically shifting the assigned code. Therefore, the receiving unit 5 can infer that there are two objects and that aliasing is occurring in one of them. The processing unit 6 can then verify the accuracy of this inference by analyzing whether the same received code can be obtained with other combinations. In other words, the processing unit 6 can separate each transmitted signal when multiple objects are present.

[0039] Then, the processing unit 6 generates information such as the distance and velocity of the object based on the analysis results (S6). The generated information is output to the electronic control devices for display control and speed control installed in the vehicle and is used for driver notification and vehicle speed control. The calculation of cross-correlation in step S5 and the generation of information in step S6 will be explained in detail in other embodiments described later. In this way, the radar device 1 performs phase shift modulation according to a linear cyclic block code as the assigned code in the modulation unit 22.

[0040] According to the radar device 1 described above, the following effects can be obtained. The radar device 1 comprises a transmitting antenna unit 3 having multiple transmitting antennas 3a, an oscillator unit 21 that generates a common signal of continuous waves, a modulation unit 22 that generates multiple transmitting signals input to the multiple transmitting antennas 3a by performing phase shift modulation on each of the multiple branch signals obtained by splitting the common signal into the same number of transmitting antennas 3a, each of which rotates the phase by a different amount of phase rotation, a receiving antenna unit 4 having one or more receiving antennas 4a, a receiving unit 5 that generates a received code that encodes the appearance pattern of peaks on the Doppler frequency axis for each of the one or more received signals received by the receiving antenna unit 4, and a processing unit 6 that generates information about an object that has reflected radiation waves from the transmitting antenna unit 3 based on the received code generated by the receiving unit 5.

[0041] Then, the radar device 1 assigns a code to which the expected peak appearance pattern on the Doppler frequency axis when an object is stationary has been encoded. The processing unit 6 sets the correspondence with each transmitting antenna 3a so that a peak associated with each transmitted signal occurs in the bin corresponding to "1" of the assigned code, and the modulation unit 22 performs phase shift modulation according to a linear cyclic block code as the assigned code.

[0042] Linear cyclic block codes possess the characteristic of cyclicity, where the cyclic shift of a codeword also becomes a codeword. Therefore, by choosing a code with a large Hamming distance, the overlap of peaks on the Doppler frequency axis can be reduced. In other words, it becomes easier to separate each transmitted signal.

[0043] This allows for accurate estimation of the velocity of each object if the transmitted signals can be separated. Furthermore, by using assigned codes with a large Hamming distance between codes, the number of overlapping peaks can be kept low, reducing angular measurement errors. In other words, accurate information about the objects can be obtained. In addition, the required code length of the assigned codes, that is, the number of phases (P) when performing phase shift modulation, is approximately twice the number (M) of the transmitting antennas 3a. Therefore, it is easy to implement, and even when there are a plurality of objects, information of the objects can be accurately obtained.

[0044] In the modulation unit 22 of the radar device 1, phase shift modulation is performed such that the minimum Hamming distance between an assigned code and a code group composed of a cyclic shift of the assigned code is 2 or more. As a result, overlapping of peaks can be reduced more, separation of each transmission signal becomes easy, and reliability of the separated result can be improved.

[0045] Also, in the modulation unit 22, the phase shift modulation can be configured such that the minimum Hamming distance between an assigned code and a code group composed of a cyclic shift is 3 or more. Even with such a configuration, overlapping of peaks can be reduced more, separation of each transmission signal can be easily performed, and reliability of the separated result can be improved.

[0046] (Second Embodiment) Hereinafter, the second embodiment will be described. In the second embodiment, another method for setting or selecting an assigned code will be described. Also, the second embodiment can be combined with one or more other embodiments if there is no conflict.

[0047] The radar device 1 can be configured such that in the modulation unit 22, phase shift modulation is performed such that a code polynomial of an assigned code is divisible by a polynomial having a period equal to or longer than the code length of the code polynomial.

[0048] Also, the radar device 1 can be configured such that in the modulation unit 22, for a code group obtained by cyclically shifting an assigned code, when the maximum number of overlapping bits is C and the minimum Hamming distance is D, phase shift modulation is performed such that C < D.

[0049] Furthermore, the radar device 1 can be configured in the modulation unit 22 to perform phase shift modulation such that, when the number of overlapping objects is K and Q is an integer greater than or equal to K, the result of the OR operation between the assigned code and any Q codes from the code group consisting of the cyclic shift of the assigned code is a different code.

[0050] Examples of assignment codes capable of such phase shift modulation include the Hamming code, CRC code, BCH code, Reed-Solomon code, cyclic Golay code, and M-sequence code described in the first embodiment. The method for determining the assignment code for each code will be explained below, but since each code is well known, the method will be illustrated using the code polynomial of the variable x. In the following equations, "^" indicates exponentiation, and "=" indicates that the code polynomial of the assignment code is divisible by a polynomial with a period equal to or greater than the code length of the code polynomial.

[0051] a) Example of Hamming code • If the assignment code is "01011001" Sign polynomial:x^5+x^3+x^2=x^2×(x^3+X+1) From the above code polynomial, a 7-bit codeword, for example "0101100", is obtained. Bit extension is then performed by adding a "1" to the end of the obtained codeword to obtain the assigned code = "01011001". In this case, bit extension can be achieved by adding a single bit of "1" or "0" to the end, to the beginning, or by inserting it between bits of the codeword.

[0052] However, as with other methods, bit extension is not essential and is merely a means to facilitate calculations in processing unit 6. For example, it can be calculated as follows: • If the assignment code is "10001011", Sign polynomial:x^6+x^2+1=x^3×(x^3+x+1) Using the above-mentioned code polynomial, we can obtain the codeword "1000101", and then perform a bit extension by adding "1" to the end of the obtained codeword to obtain the assigned code = "10001011".

[0053] b) Examples of CRC codes Sign polynomial:x^15+x^12+x^7+x^6+x^5+x^4+x+1=(x^7+x^2)×(x^8++x^7+x^6+x^4+x^2+X+1) The assigned code = "1001000010111011" is obtained from the codeword derived using the above-mentioned code polynomial.

[0054] c) Example of a BCH code Sign polynomial:x^14+x^13+x^12+x^7+x^6+x^5+x^2+X=(x^4++x^3+x^2)×(x^10++x^8+x^5+x^4+x^2+X+1) Using the above-mentioned code polynomial, we can obtain a codeword such as "111000010100110", and then perform a bit extension by adding "1" to the end of the obtained codeword to obtain the assigned code = "1110000101001101".

[0055] d) Examples of Reed-Solomon codes Sign polynomial:x^3+x+1 Using the above-mentioned code polynomial, we obtain a codeword such as "000010000011010001001", and then perform a bit extension by adding "1" to the end of the obtained codeword to obtain the assigned code = "0000100000110100010011".

[0056] e) Examples of cyclic Golay codes Sign polynomial:x^11+x^10+x^6+x^5+x^4+x^2+1 Using the above-mentioned code polynomial, we obtain a codeword such as "0111011101011111111010", and then perform a bit extension by adding "1" to the end of the obtained codeword to obtain the assigned code = "01110111010111111110101".

[0057] f) Example of an M-sequence code Sign polynomial:x^3+x+1 Using the above-mentioned code polynomial, we can obtain a codeword such as "1110100", and then perform a bit extension by adding "1" to the end of the obtained codeword to obtain the assigned code = "11101001".

[0058] By setting an assigned code from such a codeword and performing phase shift modulation in the modulation unit 22 using that assigned code, implementation is easy, similar to the first embodiment, and information about multiple objects can be accurately obtained.

[0059] (Third embodiment) The third embodiment will now be described. In the third embodiment, a specific method for analyzing the cross-correlation between the assigned code and the received code in step S5 of Figure 4, as described in the first embodiment, will be explained. Parts common to those described in other embodiments will be denoted by the same reference numerals, and detailed explanations will be omitted. Furthermore, the content described in the third embodiment can be combined with one or more other embodiments, provided there are no conflicts.

[0060] As shown in Figure 5 as an example of the calculation block configuration, the processing unit 6 of the radar device 1 in this embodiment includes a metric calculation unit 601 that calculates the cross-correlation function between the assigned code and the received code. In this embodiment, the metric calculation unit 601 calculates the correlation value between the assigned code and the received code as a relationship to the time delay (τ) which indicates how many bits the assigned code has shifted, as shown as an example of the calculation result. In Figure 5, for explanatory purposes, the assigned code used for phase shift modulation in the modulation unit 22 is shown as being input to the processing unit 6, but the assigned code is a parameter set from the processing unit 6 to the modulation unit 22 and is therefore known to the processing unit 6.

[0061] At this time, the metric calculation unit 601 calculates the cross-correlation function between the assigned code and the received code based on the Hamming distance. For example, if we conveniently refer to the result of an OR operation between the assigned code and a code obtained by shifting the assigned code by one bit as the arithmetic code, the metric calculation unit 601 determines that the correlation value is high if the Hamming distance between the received code and the arithmetic code is small, and that the correlation value is low if the Hamming distance between the received code and the arithmetic code is large. In the case of Figure 5, it is shown that the correlation value between the assigned code and the received code is high when τ=8, i.e., when it is shifted by 8 bits, and when τ=10, i.e., when it is shifted by 10 bits.

[0062] The calculation result of the metric calculation unit 601 is output to the estimation unit 602. The estimation unit 602 then extracts peaks with high correlation values ​​by performing threshold processing, which uses a threshold to extract those with high cross-correlation. This makes it possible to determine the delay time for the received code, that is, the amount of shift of the assigned code corresponding to the actual received code, and as a result, each transmitted signal can be separated.

[0063] Furthermore, if each transmitted signal can be separated, the velocity estimation unit 603 can estimate the velocity of an object such as object 100, and the angle estimation unit 604 can estimate the angle of each object. As a result, the information generation unit 605 can generate information such as the distance, velocity, or angle of each object.

[0064] Thus, the radar device 1 of this embodiment includes a metric calculation unit 601 that determines the cross-correlation between the assigned code and the received code. This makes it possible to separate each transmitted signal based on the cross-correlation when multiple peaks overlap. Therefore, it is easy to implement and can obtain accurate information about objects even when multiple objects are present, thus achieving the same effects as the first embodiment and other embodiments.

[0065] (Fourth Embodiment) The fourth embodiment will now be described. In the fourth embodiment, a specific method for analyzing the cross-correlation between the assigned code and the received code in step S5 of Figure 4, as described in the first embodiment, will be explained. Parts common to those described in other embodiments will be denoted by the same reference numerals and detailed explanations will be omitted. Furthermore, the contents described in the fourth embodiment can be combined with one or more other embodiments if there are no conflicts.

[0066] As shown in Figure 6 as an example of the calculation block configuration, the processing unit 6 of the radar device 1 in this embodiment includes a metric calculation unit 611 that determines the cross-correlation between the assigned code and the received code. The metric calculation unit 611 compares the received code with overlap pattern data 613, in which all or part of the expected values ​​of the received code assumed when multiple objects are present are stored in advance, and calculates the difference between them as the Hamming distance.

[0067] The overlap pattern data 613 is a database 64 that stores a list of all or part of the expected received codes, assuming, for example, that the number of phases is P and the number of overlapping objects is 2. The overlap pattern data 613 is referenced in the metric calculation unit 611 when calculating the cross-correlation between the assigned code and the received code. Note that the overlap pattern data 613 shown in Figure 6 is just one example. It is also possible to store other overlap pattern data 613 with different assumed numbers of overlapping objects. In other words, the overlap pattern data 613 is data that lists all or part of the expected received codes in advance for the assumed overlap situation of all or part of the objects.

[0068] As mentioned above, since the assigned codes are pre-set, the expected value of the received codes that will actually be obtained can be determined in advance by assuming the number of overlapping objects. In other words, the overlapping pattern data 613 is correlated with the assigned codes. Therefore, if the expected values ​​of the received codes are listed and stored as the overlapping pattern data 613, the cross-correlation between the received codes obtained during actual measurement and the assigned codes can be determined by referring to the overlapping pattern data 613.

[0069] For example, suppose the Hamming distance between duplicate pattern No. 1 and the received code is 3, the Hamming distance between duplicate pattern No. 2 and the received code is 4, the Hamming distance between duplicate pattern No. 3 and the received code is 0, and the Hamming distance between duplicate pattern No. U and the received code is 3. In this case, the cross-correlation between the received code and the assigned code will show a peak with the highest correlation value for duplicate pattern No. 3, a relatively low correlation value between duplicate pattern No. 1 and No. U, and the lowest correlation value for duplicate pattern No. 2. Note that the calculation results of the Hamming distance shown in Figure 6 are just one example.

[0070] The calculation results from the metric calculation unit 611 are output to the estimation unit 612. The estimation unit 612 detects peaks in the cross-correlation between the expected value of the received code and the received code by performing thresholding processing on the calculation results to extract those with high cross-correlation using a threshold, or by performing processing to find the maximum or minimum value of the calculation results. In this embodiment, the minimum value of the Hamming distance is found, but depending on how the overlapping pattern data 613 is generated, it is also possible to configure the system to find the maximum value of the Hamming distance, for example. Furthermore, thresholding processing can be combined with processing to find the minimum or maximum value.

[0071] The estimation unit 612 then estimates the overlapping pattern corresponding to the received signal in the overlapping pattern data 613 based on the peak in the detected cross-correlation. For example, in the case of Figure 6, if overlapping pattern No. 3 is detected as a peak, the estimation unit 612 identifies overlapping pattern No. 3 as the overlapping pattern corresponding to the received signal. Since the overlapping pattern is a code that was determined in advance assuming the existence of an object, if the overlapping pattern is known, the object corresponding to that pattern can be estimated. In other words, it is possible to reproduce a situation in which each transmitted signal is substantially separated.

[0072] Furthermore, if each transmitted signal can be separated, then, for example, the velocity estimation unit 603 can estimate the velocity of each object, and the angle estimation unit 604 can estimate the angle of each object, allowing the information generation unit 605 to generate information such as the distance, velocity, or angle of each object.

[0073] As described above, the radar device 1 of this embodiment includes a metric calculation unit 611 that calculates the expected value of the received code and the cross-correlation of the received code. The metric calculation unit 611 calculates the difference between the received code and the overlap pattern data 613, which is pre-stored with all or part of the expected values ​​of the received code assumed when multiple objects are present, as the Hamming distance. This makes it possible to first estimate the overlap patterns that have a high cross-correlation with the received code.

[0074] Since the overlapping pattern data 613 represents the expected value of the received signal depending on the object's condition, if overlapping patterns with high cross-correlation can be estimated, the object's condition can be estimated from those overlapping patterns. In other words, the expected object's condition can be estimated from the actual received signal. This allows for the determination of the cross-correlation between the assigned code and the received code, and enables the reproduction of a situation where each transmitted signal is substantially separated.

[0075] Therefore, it is easy to implement and can accurately obtain information about objects even when multiple objects are present, thus achieving the same effects as the first and other embodiments. In this case, for received signals not included in the duplicate pattern data 613, the duplicate pattern can be determined by cross-correlation calculation in combination with, for example, the third embodiment.

[0076] (Fifth embodiment) The fifth embodiment will now be described. In the fifth embodiment, a specific method for analyzing the cross-correlation between the assigned code and the received code in step S5 of Figure 4, as described in the first embodiment, will be explained. Parts common to those described in other embodiments will be denoted by the same reference numerals, and detailed explanations will be omitted. Furthermore, the content described in the fifth embodiment can be combined with one or more other embodiments, provided there are no conflicts.

[0077] As shown in Figure 7 as an example of the calculation block configuration, the processing unit 6 of the radar device 1 in this embodiment includes a metric calculation unit 621 that calculates the cross-correlation between the assigned code and the received code. As shown in the calculation block details, this metric calculation unit 621 includes a correlation calculation block 621a that calculates the cross-correlation between the assigned code and the received code, etc., and a difference calculation block 621b that calculates the difference between the result of the correlation calculation block 621a and the correlation calculation result data 623.

[0078] The correlation calculation block 621a, similar to the metric calculation unit 601 in the first embodiment, is a calculation block for determining the cross-correlation between the assigned code and the received code as, for example, the relationship between the correlation value and delay time shown as the calculation result in Figure 5. The difference calculation block 621b is a calculation block that calculates the difference between the calculation result of the correlation calculation block 621a and the correlation calculation result data 623, which is pre-stored in, for example, the database 64.

[0079] The correlation calculation result data 623 is data that has been pre-calculated and compiled, representing all or part of the calculation results of the cross-correlation between the expected value of the received code and the assigned code, assuming the presence of multiple objects. In other words, the correlation calculation result data 623 stores data showing cross-correlation, such as the relationship between the correlation value and delay time shown in the calculation results of Figure 5, associated with the number of assumed objects, etc. Furthermore, the correlation calculation result data 623 is stored as data that can be compared with the calculation results of the correlation calculation block 621a. In short, the correlation calculation result data 623 is data that has been pre-calculated, representing all or part of the calculation results of the cross-correlation between the expected value of the received code and the assigned code, for the overlapping situations of all or part of the assumed objects.

[0080] In this configuration, when radar measurement is performed, the correlation calculation block 621a first calculates the cross-correlation function between the assigned code and the received code, and the result of this calculation is output to the difference calculation block 621b. Subsequently, the difference calculation block 621b compares the calculation result of the correlation calculation block 621a with the correlation calculation result data, and calculates the difference between them.

[0081] The calculation result of the difference calculation block 621b is output to the estimation unit 622, and the estimation unit 622 detects peaks in the cross-correlation between the assigned code and the received code by performing threshold processing to extract those with high cross-correlation using a threshold value for the difference, or by performing processing to find the maximum or minimum value for the difference.

[0082] The correlation calculation result data 623 shows the cross-correlation between the expected value of the received signal and the assigned signal in a given situation. By detecting the peak in the cross-correlation, it is possible to estimate the situation of the object corresponding to the actual received signal. In other words, based on the correlation calculation result data 623, it is possible to reproduce the situation in which each transmitted signal is substantially separated.

[0083] Furthermore, if each transmitted signal can be separated, then, for example, the velocity estimation unit 603 can estimate the velocity of each object, and the angle estimation unit 604 can estimate the angle of each object, allowing the information generation unit 605 to generate information such as the distance, velocity, or angle of each object.

[0084] As described above, the radar device 1 of this embodiment includes a metric calculation unit 621 that calculates the cross-correlation between the assigned code and the received code. The metric calculation unit 621 compares the calculation result of the cross-correlation between the assigned code and the received code with correlation calculation result data 623, which is pre-stored and contains all or part of the calculation results of the cross-correlation between the received code and the assigned code from which the received signal is obtained when multiple objects are present, and calculates the difference. This makes it possible to estimate the status of the object corresponding to the received code and to reproduce the situation in which each transmitted signal is substantially separated.

[0085] Therefore, it is easy to implement and can accurately obtain information about objects even when multiple objects are present, thus achieving the same effects as the first and other embodiments. In this case, for received signals not included in the correlation calculation result data 623, for example, the overlapping pattern can be estimated by calculating cross-correlation in combination with the third embodiment, or estimation can be performed based on the overlapping pattern data 613 in combination with the fourth embodiment.

[0086] (Sixth Embodiment) The sixth embodiment will now be described. In the sixth embodiment, a specific method for analyzing the cross-correlation between the assigned code and the received code in step S5 of Figure 4, as described in the first embodiment, will be explained. Parts common to those described in other embodiments will be denoted by the same reference numerals, and detailed explanations will be omitted. Furthermore, the content described in the sixth embodiment can be combined with one or more other embodiments, provided there are no conflicts.

[0087] As shown in Figure 8 as an example of the calculation block configuration, the processing unit 6 of the radar device 1 in this embodiment includes a metric calculation unit 631 that determines the cross-correlation function between the assigned code and the received code, and an estimation unit 632 that detects the peak in the cross-correlation function between the assigned code and the received code.

[0088] The metric calculation unit 631, similar to the metric calculation unit 601 in the first embodiment, is a calculation block for determining the cross-correlation function between the assigned code and the received code as, for example, the relationship between the correlation value and the delay time shown as the calculation result in Figure 5.

[0089] As shown in the calculation block details, the estimation unit 632 includes calculation peak detection block 632a for detecting peaks in the calculation results of the metric calculation unit 631, correlation peak detection block 632b for detecting peaks in cross-correlation by comparing the received code with the correlation calculation result data 623, and overlap pattern estimation block 632c for estimating the overlap state of peaks based on their outputs.

[0090] The calculation peak detection block 632a detects peaks in the cross-correlation between the assigned code and the received code by performing threshold processing on the calculation results of the metric calculation unit 631 to extract those with high cross-correlation using a threshold, or by performing processing to find the maximum or minimum value of the calculation results.

[0091] The correlation peak detection block 632b compares the received code with the correlation calculation result data 623 and performs thresholding to extract those with high cross-correlation using a threshold, or performs processing to find the maximum or minimum value of the calculation result, thereby estimating the peak in the cross-correlation between the received code and the correlation calculation result data 623, that is, the data in the correlation calculation result data 623 that has a high correlation value with the received signal. However, since the information of the received code is included in the cross-correlation calculation result as the output of the metric calculation unit 632a, inputting the received code to the correlation peak detection block 632b is not mandatory when using this information.

[0092] The overlap pattern estimation block 632c estimates the overlap state of peaks corresponding to the actual object overlap by comparing the peak detected by the computational peak detection block 632a with the peak detected by the correlation peak detection block 632b. At this time, the overlap pattern estimation block 632c calculates the difference between the two peaks as the Hamming distance, for example, and if the Hamming distance is small, it determines that the peak detection results of each block are valid and estimates the object overlap state corresponding to that peak. This makes it possible to estimate the status of the object corresponding to the received code and reproduce the situation in which each transmitted signal is substantially separated.

[0093] The estimation results from the estimation unit 632 allow the velocity estimation unit 603 to estimate the velocity of each object, and the angle estimation unit 604 to estimate the angle of each object. As a result, the information generation unit 605 can generate information such as the distance, velocity, and angle of each object.

[0094] Thus, the radar device 1 of this embodiment includes a metric calculation unit 621 that determines the cross-correlation between the assigned code and the received code, and an estimation unit 632 that detects peaks in the cross-correlation between the assigned code and the received code.

[0095] The estimation unit 632 then estimates the overlap of objects by performing thresholding processing on the calculation results of the metric calculation unit 631 to extract peaks using thresholds, or by comparing the peaks detected by processing to find the maximum, minimum, or extreme values ​​on the calculation results of the metric calculation unit with the peaks obtained by comparing the received signal with the correlation calculation result data 623. This makes it possible to reproduce a situation in which each transmitted signal is substantially separated.

[0096] Therefore, it is easy to implement and can accurately obtain information about objects even when multiple objects are present, thus achieving the same effects as the first and other embodiments. In this case, for received signals not included in the correlation calculation result data 623, for example, the overlapping pattern can be estimated by calculating cross-correlation in combination with the third embodiment, or estimation can be performed based on the overlapping pattern data 613 in combination with the fourth embodiment.

[0097] (Seventh Embodiment) The seventh embodiment will now be described. In the seventh embodiment, a specific method for analyzing the cross-correlation between the assigned code and the received code in step S5 of Figure 4, as described in the first embodiment, will be explained. Parts common to those described in other embodiments will be denoted by the same reference numerals, and detailed explanations will be omitted. Furthermore, the content described in the seventh embodiment can be combined with one or more other embodiments, provided there are no conflicts.

[0098] As shown in Figure 9 as an example of the calculation block configuration, the processing unit 6 of the radar device 1 in this embodiment includes a metric calculation unit 641 that determines the cross-correlation between the assigned code and the received code, and an estimation unit 642 that detects peaks in the cross-correlation between the assigned code and the received code.

[0099] The metric calculation unit 641, similar to the metric calculation unit 601 in the first embodiment, is a calculation block for determining the cross-correlation function between the assigned code and the received code as, for example, the relationship between the correlation value and the delay time shown as the calculation result in Figure 5.

[0100] As shown in the calculation block details, the estimation unit 642 includes a calculation peak detection block 642a that detects the peak of the calculation result of the metric calculation unit 641, an overlap pattern estimation block 642b that estimates the peak overlap state by comparing the calculation result of the metric calculation unit 641 with the overlap pattern data 613, and a selector 642c that selects the one with a higher correlation value with the received signal from the detection result of the calculation peak detection block 642a and the estimation result of the overlap pattern estimation block 642b.

[0101] The calculation peak detection block 642a detects peaks in the cross-correlation between the assigned code and the received code by performing threshold processing on the calculation results of the metric calculation unit 641 to extract those with high cross-correlation using a threshold, or by performing processing to find the maximum or minimum value of the calculation results.

[0102] The overlap pattern estimation block 642b compares the calculation result of the metric calculation unit 641 with the correlation calculation result data 623 and estimates the peak in their cross-correlation, that is, the data in the correlation calculation result data 623 that has a high correlation value with the calculation result.

[0103] The selector 642c then selects the result of the calculation peak detection block 642a and the result of the overlap pattern estimation block 642b that has a greater cross-correlation with the received signal, for example, a relatively smaller Hamming distance. If the results of both are the same, either one can be selected, and if both are judged to have low certainty, the system can be configured to detect peaks based on other methods described in other embodiments.

[0104] In other words, in this embodiment, peaks corresponding to the overlapping status of objects are detected using multiple methods, and the most reliable method is selected. Since the overlapping pattern data 613 is the expected value of the received signal assumed according to the status of the objects, if an overlapping pattern with a high cross-correlation can be estimated, the status of the objects can be estimated from that overlapping pattern. In other words, the assumed status of the objects can be estimated from the actual received signal. This makes it possible to determine the cross-correlation between the assigned code and the received code, and to reproduce a situation in which each transmitted signal is substantially separated.

[0105] As described above, the radar device 1 of this embodiment includes a metric calculation unit 621 that determines the cross-correlation between the assigned code and the received code, and an estimation unit 642 that detects peaks in the cross-correlation between the assigned code and the received code. The estimation unit 642 then estimates the object overlap situation by comparing the peak obtained from the calculation result of the metric calculation unit 641 with the peak obtained by comparing the calculation result with the overlap pattern data 613.

[0106] This makes it possible to reproduce a situation in which each transmitted signal is substantially separated. Therefore, it is easy to implement and can obtain the same effects as the first and other embodiments, such as being able to accurately obtain information about objects even when multiple objects are present. In this case, for received signals that are not included in the overlapping pattern data 613, the overlapping pattern can be estimated by calculating cross-correlation in combination with the third embodiment, for example, or estimation can be performed in combination with the fifth embodiment based on the correlation calculation result data 623.

[0107] The control unit and its method described herein may be implemented by a dedicated computer provided by configuring a processor and memory programmed to perform one or more functions embodied by a computer program. Alternatively, the control unit and its method described herein may be implemented by a dedicated computer provided by configuring a processor by one or more dedicated hardware logic circuits. Alternatively, the control unit and its method described herein may be implemented by one or more dedicated computers configured by a combination of a processor and memory programmed to perform one or more functions and a processor configured by one or more hardware logic circuits. Furthermore, the computer program may be stored as instructions executed by the computer on a computer-readable non-transitional tangible recording medium.

[0108] This case includes the invention described in the claims, as well as the following inventions: [1] A transmitting antenna section having multiple transmitting antennas, An oscillator that generates a common signal of a continuous wave, A modulation unit that generates multiple transmission signals input to the multiple transmission antennas by performing phase shift modulation on each of the multiple branch signals obtained by splitting the common signal into the same number of branches as the transmitting antenna, each branch rotating the phase by a different amount of phase rotation, A receiving antenna unit having one or more receiving antennas, A receiving unit that generates a received code by encoding the pattern of peak appearance on the Doppler frequency axis for each of the one or more received signals received by the receiving antenna unit, The system includes a processing unit that generates information about an object that has reflected radiation waves from the transmitting antenna unit based on the received code generated by the receiving unit, If we assign a code that encodes the expected pattern of peak appearances on the Doppler frequency axis when an object is at rest, A radar device that performs phase shift modulation according to a linear cyclic block code as the assigned code in the modulation unit. [2] The radar device according to [1], wherein in the modulation unit, phase shift modulation is performed such that the minimum Hamming distance between the assigned code and a code group composed of a cyclic shift of the assigned code is 2 or more. [3] The radar device according to [1] or [2], wherein in the modulation unit, phase shift modulation is performed such that the minimum Hamming distance between the assigned code and a code group composed of a cyclic shift of the assigned code is 3 or more. [4] The radar device according to any one of [1] to [3], wherein in the modulation unit, phase shift modulation is performed such that the code polynomial of the assigned code is divisible by a polynomial having a period equal to or longer than the code length of the code polynomial. [5] The radar device according to any one of [1] to [4], wherein in the modulation unit, phase shift modulation is performed such that for a code group obtained by cyclically shifting the assigned code, when the maximum number of overlapping bits is C and the minimum Hamming distance is D, C < D. [6] The radar device according to any one of [1] to [5], wherein in the modulation unit, phase shift modulation is performed such that the assigned code is any one of a Hamming code, a CRC code, a BCH code, a Reed - Solomon code, a cyclic Golay code, and an M - sequence code. [7] The radar device according to any one of [1] to [6], wherein the assigned code is subjected to bit extension by adding 1 or 0 for 1 bit so that the code length is a power of 2. [8] The radar device according to any one of [1] to [7], wherein in the modulation unit, phase shift modulation is performed such that when the number of overlapping objects is K and an integer Q greater than or equal to K is considered, the result of performing an OR operation on any Q codes of a code group composed of the assigned code and a cyclic shift of the assigned code is a different code for each. [9] A radar device according to any one of [1] to [8], comprising a metric calculation unit for determining the cross-correlation between the assigned code and the received code.

[10] The radar device according to [1], comprising a metric calculation unit that compares the received code with duplicate pattern data in which all or part of the expected values ​​of the received code assumed when multiple objects are present are stored in advance, and calculates the difference.

[11] The radar device according to [9] or

[10] , wherein the metric calculation unit compares the calculation result of the cross-correlation between the assigned code and the received code with correlation calculation result data, which is stored in advance and contains the calculation results of all or part of the cross-correlation between the received code and the assigned code from which the received signal is obtained, assuming that multiple objects exist, and calculates the difference.

[12] The radar device according to

[10] or

[11] , wherein the metric calculation unit calculates the difference using the Hamming distance.

[13] The system includes an estimation unit that detects peaks in the calculation result of the cross-correlation between the assigned code and the received code. The estimation unit extracts peaks by performing thresholding processing on the calculation results of the metric calculation unit using a threshold value, or by performing processing to determine the maximum value, minimum value, or extreme value on the calculation results of the metric calculation unit, and compares the peaks obtained by comparing the peaks with correlation calculation result data, which is stored in advance and contains all or part of the calculation results of the cross-correlation between the received signal and the received code assumed to exist when multiple objects are present and the assigned code from which the received signal is obtained. A radar device as described in any of [9] to

[12] that estimates the degree of overlap of objects by comparing them.

[14] The system includes an estimation unit that detects peaks in the calculation result of the cross-correlation between the assigned code and the received code, The radar apparatus according to any one of the following [9] to

[13] , wherein the estimation unit estimates the object overlap status by comparing a peak calculated on the calculation result of the metric calculation unit with a peak obtained by comparing the calculation result of the metric calculation unit with overlap pattern data in which all or part of the expected value of the received code assumed when multiple objects exist is stored in advance. [Explanation of Symbols]

[0109] In the diagram, 1 is the radar device, 2 is the transmitter, 3 is the transmitting antenna, 3a is the transmitting antenna, 4 is the receiving antenna, 4a is the receiving antenna, 5 is the receiving unit, 6 is the processing unit, 21 is the oscillation unit, 22 is the modulation unit, 601, 611, 621, 631, and 641 are the metric calculation units, 602, 612, 622, 632, and 642 are the estimation units, 613 is the overlapping pattern data, and 623 is the correlation calculation result data.

Claims

1. A transmitting antenna unit (3) having multiple transmitting antennas (3a), An oscillator (21) that generates a common signal of a continuous wave, A modulation unit (22) generates multiple transmission signals that are input to the multiple transmission antennas by performing phase shift modulation on each of the multiple branch signals obtained by splitting the common signal into the same number of branches as the transmitting antennas, each branch rotating the phase by a different amount of phase rotation, A receiving antenna unit (4) having one or more receiving antennas (4a), A receiving unit (5) generates a received code that encodes the pattern of peak appearance on the Doppler frequency axis for each of the one or more received signals received by the receiving antenna unit, The system includes a processing unit (6) that generates information about an object that has reflected radiation waves from the transmitting antenna unit based on the receiving code generated by the receiving unit, If we assign a code that encodes the expected pattern of peak appearances on the Doppler frequency axis when an object is at rest, A radar device in which the modulation unit performs phase-shift modulation according to a linear block code having a code length equal to the number of phases (P) used for the phase-shift modulation as the assigned code.

2. The radar device according to claim 1, wherein the modulation unit performs phase shift modulation such that the minimum Hamming distance between the assigned code and the code group consisting of the cyclic shift of the assigned code is 2 or more.

3. The radar device according to claim 1, wherein the modulation unit performs phase shift modulation such that the minimum Hamming distance between the assigned code and the code group consisting of the cyclic shift of the assigned code is 3 or more.

4. The radar device according to claim 1, wherein the modulation unit performs phase shift modulation such that the code polynomial of the assigned code is a polynomial divisible by a polynomial having a period equal to or greater than the code length of the code polynomial.

5. The radar device according to claim 1, wherein the modulation unit performs phase shift modulation on the group of codes obtained by cyclically shifting the assigned codes such that C < D, where C is the maximum number of overlapping bits and D is the minimum Hamming distance.

6. The radar apparatus according to claim 1, wherein the modulation unit performs phase shift modulation in which the assigned code is one of the following: Hamming code, CRC code, BCH code, Reed-Solomon code, cyclic Golay code, and M-sequence code.

7. The radar device according to claim 1, wherein the assigned code is bit-extended by adding one bit of 1 or 0 such that the code length becomes a power of 2.

8. The radar apparatus according to claim 1, wherein in the modulation unit, when the number of overlapping objects is K and the assigned code is an integer greater than or equal to K, the radar apparatus performs phase shift modulation such that the results of OR operations on any Q codes from the code group consisting of the assigned code and the cyclic shift of the assigned code are each different codes.

9. The radar device according to claim 1, further comprising a metric calculation unit (601, 611, 621, 631, 641) for determining the cross-correlation function between the assigned code and the received code.

10. The radar device according to claim 1, further comprising a metric calculation unit that compares the received code with duplicate pattern data in which all or part of the expected values ​​of the received code assumed when multiple objects are present are stored in advance, and calculates the difference.

11. The radar device according to claim 9, wherein the metric calculation unit compares the calculation result of the cross-correlation between the assigned code and the received code with correlation calculation result data, which is stored in advance and contains the calculation results of all or part of the cross-correlation between the received code and the assigned code from which the received signal is obtained, assuming that multiple objects exist, and calculates the difference.

12. The radar device according to claim 10 or 11, wherein the metric calculation unit calculates the difference using the Hamming distance.

13. The system includes estimation units (602, 612, 622, 632, 642) that detect peaks in the calculation result of the cross-correlation between the assigned code and the received code. The radar device according to claim 9, wherein the estimation unit estimates the overlapping status of objects by performing threshold processing to extract peaks using thresholds on the calculation results of the metric calculation unit, or by comparing the peaks detected by performing processing to find the maximum value, minimum value, or extreme value on the calculation results of the metric calculation unit with correlation calculation result data, which is stored in advance and contains all or part of the calculation results of the cross-correlation between the expected value of the received code assumed when the received signal and multiple objects are present, and the assigned code on which the received signal is obtained.

14. The system includes estimation units (602, 612, 622, 632, 642) that detect peaks in the calculation results of the cross-correlation between the assigned code and the received code, The radar apparatus according to claim 9, wherein the estimation unit (642) estimates the object overlap status by comparing a peak calculated on the calculation result of the metric calculation unit with a peak obtained by comparing the calculation result of the metric calculation unit with overlap pattern data in which all or part of the expected value of the received code assumed when multiple objects exist is stored in advance.

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