Method for extracting target on basis of FMCW radar and apparatus therefor

Abstract

Disclosed are a method and an apparatus for extracting a target on the basis of an FMCW radar. The method for extracting a target on the basis of an FMCW radar comprises the steps of: (a) transmitting a radar transmission signal, the radar transmission signal being a signal to which binary phase shift keying (BPSK) modulation has been performed on the basis of a first binary code; (b) obtaining a radar reception signal reflected by a target; (c) generating a ghost target signal by multiplying the reception signal by a second binary code; and (d) extracting an actual target signal by removing the ghost target signal from the reception signal.

Description

FMCW radar-based target extraction method and device thereof

[0001] The present invention relates to a method for extracting a target based on an FMCW radar and a device therefor.

[0002]

[0003] In automotive radar systems, MIMO FMCW radar systems are mainly used, which use a large-scale virtual antenna array technique that physically increases the number of antennas for high-resolution angle estimation.

[0004] To estimate the target's range, velocity, and angle information using a MIMO FMCW radar system, the receiver must distinguish the signals transmitted from each antenna element. Therefore, the antenna system adopts time-division multiplexing (TDM), frequency division multiplexing (FDM), or code-division multiplexing (CDM) to transmit FMCW radar signals.

[0005] Currently, TDM-based MIMO is the most widely used method. However, TDM-based MIMO FMCW radar systems suffer from a problem: the maximum detectable speed decreases proportionally to the number of transmitting antennas. Furthermore, the time delay between waveforms transmitted from different antenna elements significantly reduces angle estimation accuracy.

[0006] To address the challenges of TDM-based MIMO FMCW radar systems, a BPSK (Binary Phase Shift Keying)-based MIMO FMCW radar system can be considered. BPSK-based MIMO FMCW radar systems transmit signals with binary phase modulation. While binary phase modulation can mitigate the reduction in maximum detectable velocity, it also poses the problem of ghost targets being detected along the Doppler axis.

[0007]

[0008] The present invention provides a method for extracting a target based on an FMCW radar and a device therefor.

[0009] In addition, the present invention provides a method and device for extracting a target based on an FMCW radar capable of detecting only an actual target by distinguishing and removing a ghost target using a new binary code at a receiving end.

[0010]

[0011] According to one aspect of the present invention, a method for extracting a target based on an FMCW radar is provided.

[0012] According to one embodiment of the present invention, an FMCW radar-based target extraction method may be provided, including: (a) transmitting a radar transmission signal, wherein the radar transmission signal is a signal modulated by binary phase shift keying (BPSK) based on a first binary code; (b) obtaining a radar reception signal reflected by a target; (c) generating a ghost target signal by multiplying the reception signal by a second binary code; and (d) extracting an actual target signal by removing the ghost target signal from the reception signal.

[0013] The above second binary code is a code not used for transmitting the transmission signal, and may be a binary code orthogonal to the first binary code used for transmitting the transmission signal.

[0014] The above first binary code is assigned using the following mathematical formula:

[0015]

[0016] Here, represents the total number of chirps, t represents time, represents the binary code length.

[0017] The above step (d) can extract the actual target signal by subtracting the ghost target signal from the received signal.

[0018] The above step (d) extracts the actual target signal using the following mathematical formula,

[0019]

[0020] Here, represents the received signal, indicates a ghost target signal, represents the second binary code.

[0021] According to another aspect of the present invention, an FMCW radar-based target extraction device is provided.

[0022] According to one embodiment of the present invention, an FMCW radar-based target extraction device may be provided, including a radar sensor that transmits a radar transmission signal and obtains a radar reception signal reflected by a target, the radar transmission signal being a signal modulated by binary phase shift keying (BPSK) based on a first binary code; a ghost target signal generation unit that generates a ghost target signal by multiplying the reception signal by a second binary code; and a target extraction unit that extracts an actual target signal by removing the ghost target signal from the reception signal.

[0023] The target extraction unit can extract the actual target signal by subtracting the ghost target signal from the received signal.

[0024]

[0025] By providing a FMCW radar-based target extraction method and device according to one embodiment of the present invention, there is an advantage in that only actual targets can be detected by distinguishing and removing ghost targets using a new binary code at a receiving end.

[0026]

[0027] FIG. 1 is a flowchart illustrating an FMCW radar-based target extraction method according to one embodiment of the present invention.

[0028] FIG. 2 is a diagram illustrating a binary code used for transmission and reception according to one embodiment of the present invention.

[0029] FIG. 3 is a diagram illustrating system parameters according to one embodiment of the present invention.

[0030] FIG. 4 is a diagram illustrating a simulation environment for an antenna layout of a MIMO radar system according to one embodiment of the present invention.

[0031] FIG. 5 is a diagram illustrating target information according to one embodiment of the present invention.

[0032] FIG. 6 is a diagram showing the Doppler shift according to the spectrum of the code assigned to each transmission antenna element according to one embodiment of the present invention.

[0033] FIGS. 7 and 8 are diagrams illustrating distance-Doppler maps according to one embodiment of the present invention.

[0034] FIG. 9 is a diagram illustrating a ghost target detection result according to one embodiment of the present invention.

[0035] Figure 10 is a result of representing the ghost target detection result according to one embodiment of the present invention as a distance-Doppler map.

[0036] FIG. 11 is a diagram illustrating an actual target detection result according to one embodiment of the present invention.

[0037] FIG. 12 is a diagram schematically illustrating the internal configuration of an FMCW radar-based target extraction device according to one embodiment of the present invention.

[0038]

[0039] As used herein, singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, terms such as "consist of" or "include" should not be construed to necessarily include all components or steps described in the specification, and should be construed to mean that some of the components or steps may not be included, or that additional components or steps may be included. In addition, terms such as "part" and "module" described in the specification mean a unit that processes at least one function or operation, which may be implemented by hardware or software, or by a combination of hardware and software.

[0040] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings.

[0041]

[0042] FIG. 1 is a flowchart illustrating a method for extracting a target based on an FMCW radar according to an embodiment of the present invention, FIG. 2 is a diagram illustrating a binary code used for transmission and reception according to an embodiment of the present invention, FIG. 3 is a diagram illustrating system parameters according to an embodiment of the present invention, FIG. 4 is a diagram illustrating a simulation environment for an antenna layout of a MIMO radar system according to an embodiment of the present invention, FIG. 5 is a diagram illustrating target information according to an embodiment of the present invention, FIG. 6 is a diagram illustrating a Doppler shift according to a spectrum of a code assigned to each transmission antenna element according to an embodiment of the present invention, FIGS. 7 and 8 are diagrams illustrating a range-Doppler map according to an embodiment of the present invention, FIG. 9 is a diagram illustrating a ghost target detection result according to an embodiment of the present invention, FIG. 10 is a diagram illustrating a ghost target detection result represented as a range-Doppler map according to an embodiment of the present invention, and FIG. 11 is a diagram illustrating an actual target detection result according to an embodiment of the present invention.

[0043] In step 110, the FMCW radar-based target extraction device (100) transmits a radar signal.

[0044] Here, the radar signal may be a BPSK-based FMCW radar signal.

[0045] For the convenience of understanding and explanation, we will first briefly explain the transmission and reception signals in a single input / single output FMCW radar system.

[0046] The signal transmitted from an FMCW radar system consists of a series of chirps. The pth chirp of the signal transmitted from can be expressed as in mathematical expression 1. Here, am.

[0047]

[0048] Here, and represents the amplitude and phase offset of the pth chirp, , represents the center frequency, bandwidth, and duration of each chirp, respectively. A transmission signal of one cycle including all chirps can be expressed as in mathematical expression 2.

[0049]

[0050] Here, represents the transmission cycle.

[0051] At this time, the signal reflected and received by the target can be expressed as in mathematical expression 3.

[0052]

[0053] Here, represents the amplitude of the received signal, is the distance of the kth target ( ) and speed ( ) indicates the time delay caused by the represents the number of targets, represents the noise added from the receiving antenna element.

[0054] The number of transmitting antenna elements is and the number of receiving antenna elements is Considering the MIMO antenna system, all The signal transmitted by the transmitting antenna element is rth When received by the receiving antenna element, it can be expressed as in mathematical expression 4.

[0055]

[0056] Here, represents the noise added to the rth receiving antenna element, and is the spacing between the transmitting antenna elements respectively ( ) and the spacing between the receiving antenna elements ( ) represents the time delay due to the kth target and the angle formed by the boresight of the antenna. In this case, the total time delay according to the antenna spacing can be expressed as in mathematical equation 5.

[0057]

[0058] Here, represents the wavelength corresponding to the center frequency of the FMCW radar signal.

[0059] In a BPSK-based MIMO FMCW radar system, the FMCW radar signal transmitted from the qth antenna element can be modulated as in mathematical expression 6.

[0060]

[0061] Here, represents the code assigned to the qth antenna element for BPSK modulation, and is generally uses orthogonal codes to reduce cross-correlation between signals transmitted from different antenna elements. For example, Hadamard codes can be used for BPSK modulation.

[0062] In one embodiment of the present invention, the total number of copies is Binary codes can be assigned by dividing them into units. This can be expressed mathematically as shown in Equation 7.

[0063]

[0064] Here Is exists between and all has a value of 1 or -1.

[0065] In addition, in one embodiment of the present invention So that it becomes an integer cast Set as a multiple of . Also, They satisfy the property of being orthogonal to each other and can be expressed as in mathematical equation 8.

[0066]

[0067] In step 115, the FMCW radar-based target extraction device (100) receives a radar reception signal reflected by the target.

[0068] The received signal from the FMCW radar system is down-converted to a baseband signal through a frequency mixer and a low-pass filter. Typically, there is a time delay. and Is which means is very small compared to . Therefore, the signal transmitted from the qth transmitting antenna element is sampled by the ADC at the rth receiving antenna element and can be expressed as in mathematical expression 9.

[0069]

[0070] Here, n(n = 1, 2,..., ) is the index of the time sample in each chirp, represents the sampling interval. Also, represents the amplitude of the kth baseband signal. In a MIMO antenna system, the signal received by the rth antenna element can be expressed as the sum of the signals transmitted by all transmitting antenna elements, as in mathematical expression 10.

[0071]

[0072] For example, consider a BPSK-based MIMO radar system with three transmit antenna elements, each of which uses an orthogonal Hadamard code as follows:

[0073] , , This is illustrated in Fig. 2. In Fig. 2, the system parameter values ​​related to the FMCW radar are set to values ​​widely used in commercial automotive radar.

[0074] As shown in FIG. 3, in one embodiment of the present invention, the spacing between all antenna elements is 0.45 A 3 x 16 MIMO antenna system is assumed, and the antenna layout of the MIMO radar system is shown in the simulation environment in Fig. 4. The target information is as shown in Fig. 5.

[0075] The signal transmitted from each transmitting antenna element is shifted along the Doppler axis by the assigned binary phase code, and Fig. 6 shows the Doppler shift according to the spectrum of the code assigned to each transmitting antenna element. In the case of (a) of Fig. 6 The transmitted signal encoded in is not affected by the phase. Therefore, the Doppler shift does not appear and the detection result of the actual target is maintained. However, the transmitted signal in (b) and (c) of Fig. 6 is shifted along the Doppler axis by the binary phase code and shows different Doppler shifts depending on the spectrum of the code.

[0076] To understand the influence of the binary-coded signal multiplied at each transmitting antenna, the signal received at the rth receiving antenna element was decomposed as shown in (a), (b), and (c) of Figs. 7 and 8. In reality, three transmitting signals are combined and received, as shown in (d) of Fig. 8. As described in Fig. 6, the position of the detected target moves along the Doppler axis.

[0077] In one embodiment of the present invention, a target that is not an actual target is defined as a ghost target, and ghost targets generated at the receiver can be removed to extract only the actual target. This will be more clearly understood through the following explanation.

[0078] In step 120, the FMCW radar-based target extraction device (100) generates a ghost target signal by multiplying the received signal by a second binary code. In one embodiment of the present invention, the second binary code is a code not used for transmitting a transmission signal, and is defined as a binary code orthogonal to the first binary code used for transmitting the transmission signal.

[0079] At the receiving end, BPSK modulation Use the code, that is, The number of Not This is done. At this time, the transmitter is 1~ The second code is used, and the receiver is the last Use the second code.

[0080] Suggestion sign in When multiplied by , the decoded received signal can be expressed as in mathematical expression 11.

[0081]

[0082] In this way, when the received signal is decoded using a second binary code, a Doppler shift occurs due to the binary code multiplied at the receiver, as illustrated in Fig. 9. Therefore, the actual target information disappears, leaving only the Doppler-shifted signal.

[0083] Consequently, when the received signal is decoded using the second binary code, the actual target information disappears, and only the Doppler-shifted signal (i.e., the ghost target) can be extracted. For example, the result of decoding the received signal according to an embodiment of the present invention based on the target detection result of (d) of FIG. 8 is as shown in FIG. 10.

[0084] As shown in (b) of Figure 2, the code used in the transmitter is orthogonal to is used. As shown in Fig. 10, Multiplying the received signal by the binary code only removes the actual target information from the range-Doppler map.

[0085] For the convenience of understanding and explanation, a signal generated by multiplying a received signal by a second binary code is referred to as a ghost target signal in one embodiment of the present invention.

[0086] In step 125, the FMCW radar-based target extraction device (100) removes the ghost target signal from the received signal to extract the actual target signal.

[0087] As described above, a ghost target signal can be generated by multiplying the received signal by a second binary code. Accordingly, the FMCW radar-based target extraction device (100) subtracts the ghost target signal from the received signal to extract only the actual target from the range-Doppler map where both the ghost target and the actual target exist simultaneously.

[0088] As a result, only the actual target can be extracted using the signals of Equations 10 and 11, and this can be expressed as Equation 12.

[0089]

[0090] Here, are two signals and Represents a constant for compensating the signal strength between the actual target and the ghost target. The maximum value of the peak shown in If so, max and The minimum value of the peak shown in is the ghost target only. When multiplied by the second binary code, is displayed as, Is As shown in Fig. 11, by subtracting the ghost target signal from the received signal, all ghost targets are removed, leaving only information about the actual target in the range-Doppler map.

[0091]

[0092] FIG. 12 is a diagram schematically illustrating the internal configuration of an FMCW radar-based target extraction device according to one embodiment of the present invention.

[0093] Referring to FIG. 12, an FMCW radar-based target extraction device (100) according to one embodiment of the present invention is configured to include a radar sensor (1110), a ghost target signal generation unit (1120), a target extraction unit (1130), a memory (1140), and a processor (1150).

[0094] The radar sensor (1110) can transmit a radar transmission signal and obtain a radar reception signal reflected by a target.

[0095] At this time, the radar transmission signal is a BPSK (Binary phase shift keying) modulated signal based on the first binary code.

[0096] The ghost target signal generation unit (1120) is a means for generating a ghost target signal by multiplying a received signal by a second binary code. As previously described, the second binary code is a code not used for transmitting a radar transmission signal, but may be a code orthogonal to the first binary code.

[0097] The target extraction unit (1130) can extract the actual target signal by removing the ghost target signal from the received signal. In other words, the target extraction unit (1130) can detect only the actual target by removing the ghost target by subtracting the ghost target signal from the received signal.

[0098] The memory (1140) stores a command for performing an FMCW radar-based target extraction method according to one embodiment of the present invention.

[0099] The processor (1150) is a means for controlling internal components (e.g., radar sensor (1110), ghost target signal generation unit (1120), target extraction unit (1130), memory (1140), etc.) of an FMCW radar-based target extraction device (100) according to one embodiment of the present invention.

[0100]

[0101] The device and method according to the embodiment of the present invention may be implemented in the form of program commands that can be executed through various computer means and recorded on a computer-readable medium. The computer-readable medium may include program commands, data files, data structures, etc., alone or in combination. The program commands recorded on the computer-readable medium may be those specially designed and configured for the present invention or may be those known and usable by those skilled in the art of computer software. Examples of the computer-readable recording medium include magnetic media such as hard disks, floppy disks, and magnetic tapes, optical media such as CD-ROMs and DVDs, magneto-optical media such as floptical disks, and hardware devices specially configured to store and execute program commands such as ROMs, RAMs, and flash memories. Examples of program commands include not only machine language codes generated by a compiler, but also high-level language codes that can be executed by a computer using an interpreter, etc.

[0102] The hardware device described above may be configured to operate as one or more software modules to perform the operations of the present invention, and vice versa.

[0103] The present invention has been described above, focusing on specific embodiments thereof. Those skilled in the art will appreciate that the present invention can be implemented in modified forms without departing from its essential characteristics. Therefore, the disclosed embodiments should be considered illustrative rather than limiting. The scope of the present invention is set forth in the claims, not the foregoing description, and all differences within the scope equivalent thereto should be construed as being encompassed by the present invention.

Claims

1. (a) A step of transmitting a radar transmission signal - the radar transmission signal is a signal modulated by BPSK (Binary phase shift keying) based on a first binary code; (b) a step of acquiring a radar reception signal reflected by a target; (c) generating a ghost target signal by multiplying the received signal by a second binary code; and (d) An FMCW radar-based target extraction method comprising a step of extracting an actual target signal by removing the ghost target signal from the received signal.

2. In paragraph 1, An FMCW radar-based target extraction method, characterized in that the second binary code is a code not used for transmitting a transmission signal and is a binary code orthogonal to the first binary code used for transmitting the transmission signal.

3. In paragraph 1, An FMCW radar-based target extraction method, characterized in that the first binary code is allocated using the following mathematical formula. Here, represents the total number of chirps, t represents time, represents the binary code length.

4. In paragraph 1, Step (d) above, An FMCW radar-based target extraction method characterized in that the actual target signal is extracted by subtracting the ghost target signal from the received signal.

5. In paragraph 1, Step (d) above, An FMCW radar-based target extraction method characterized in that the actual target signal is extracted using the following mathematical formula. Here, represents the received signal, indicates a ghost target signal, represents the second binary code.

6. A computer-readable recording medium recording a program code for performing a method according to any one of clauses 1 to 5.

7. A radar sensor that transmits a radar transmission signal and obtains a radar reception signal reflected by a target, wherein the radar transmission signal is a signal modulated by BPSK (Binary phase shift keying) based on a first binary code; A ghost target signal generation unit that generates a ghost target signal by multiplying the received signal by a second binary code; and An FMCW radar-based target extraction device including a target extraction unit that extracts an actual target signal by removing the ghost target signal from the received signal.

8. In paragraph 7, An FMCW radar-based target extraction device, characterized in that the second binary code is a code not used for transmitting a transmission signal and is a binary code orthogonal to the first binary code used for transmitting the transmission signal.

9. In paragraph 7, The above target extraction unit, An FMCW radar-based target extraction device characterized in that the actual target signal is extracted by subtracting the ghost target signal from the received signal.

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