KR102641300B1 - Target detection method and system based on phase information of MIMO radar signal - Google Patents

Abstract

A target detection method and system based on phase information of MIMO radar signals are disclosed. When a radar transmission signal transmitted through a plurality of transmitting antennas is reflected by a target and received through a plurality of receiving antennas, the distance-speed detection result of each received signal is obtained through predetermined signal processing for each received signal. Find the peak and extract the phase information of the peak. The phase values of the distance-velocity peaks extracted from the received signals of all the plurality of receiving antennas are arranged to form an arithmetic sequence, and the received signals are classified for each transmitting antenna based on the phase value sequence arranged in the arithmetic sequence. Using phase values arranged in an arithmetic sequence, the correct speed of the target can be estimated and angle estimation can be performed simultaneously.

Description

Target detection method and system based on phase information of MIMO radar signal}

The present invention relates to target detection technology using a radar system, and more specifically, to each transmitting antenna in a frequency-modulated continuous wave (FMCW) radar system based on a multiple input multiple output (MIMO) antenna. This relates to a technology that allows accurate detection of targets by classifying signals received from each transmitting antenna.

FMCW radar is widely used as an automotive sensor to obtain information about surrounding objects such as distance, speed, and angle. Additionally, MIMO antenna systems are being utilized to obtain high angular resolution with limited hardware size. In a MIMO-based FMCW radar system, in order to operate correctly, the receive (Rx) antenna must be able to distinguish between signals transmitted from multiple transmit (Tx) antennas. For this purpose, various signal multiplexing methods are used. For example, various signal multiplexing methods such as Time Division Multiplexing (TDM), Frequency Division Multiplexing (FDM), and Code Division Multiplexing (CDM) can be used to maintain orthogonality of transmitted signals. You can. Among them, the TDM method, in which each transmission antenna divides time slots and transmits at different times, is widely used.

The TDM method has the advantage of being easy to implement. However, the biggest disadvantage of the TDM method is that the chirp repetition time becomes longer, which reduces the maximum detectable speed, that is, the maximum detection speed, in proportion to the number of transmit antennas. Additionally, because each transmitting antenna transmits signals alternately, there is a disadvantage that if the target to be detected moves, angle estimation performance may deteriorate due to the Doppler effect caused by the movement of the target.

To solve this issue, several proposals have been made to resolve the Doppler-angle ambiguity of TDM-MIMO radar systems. In Non-Patent Document 1 below, the typical chirp sequence has been modified to assign a different start frequency to each chirp. Similarly, in Non-Patent Document 2 below, several types of chirp repetition frequencies were assigned and the original maximum detectable rate was recovered using the Chinese remainder theorem. However, the main disadvantage associated with these methods is that existing hardware must be modified.

Another approach is to assign a specific code to each transmit antenna and transmit the signals simultaneously. In particular, Binary Phase-Shift Keying (BPSK) is a widely used method of modulating the phase of a transmission signal to 0 or π. This method can separate the signals of each transmit antenna by using the orthogonality of the transmitted signal. Unlike the TDM-MIMO system, the BPSK-MIMO system requires an additional decoding process to separate the signals from each transmit antenna. However, higher signal-to-noise ratios (SNR) can be achieved by using the full transmit capability of the transmit antenna.

However, the BPSK-MIMO system also experiences Doppler-angle ambiguity because the block time used for speed estimation becomes longer in proportion to the number of transmission antennas. In other words, in the distance-speed detection results of the BPSK-MIMO radar system, each target appears overlapping as many as the number of transmitting antennas. In other words, when a radar signal is transmitted with N transmitting antennas, a peak corresponding to one actual target and a peak corresponding to (N-1) ghost targets are detected in the peak detection of the received signal. When using the BPSK method, a problem occurs in which the maximum detection speed is reduced by half due to the peak corresponding to the ghost target.

In Non-Patent Document 3 below, multiple frames with different definite rates were used and the original maximum detectable rate was recovered using the Chinese remainder theorem or clustering algorithm. However, this method requires modifying existing hardware similar to the method used in Non-Patent Documents 1 and 2. Non-patent Document 3 also attempted to restore the original maximum detectable speed by compensating the phase of the received signal using the estimated speed value. However, this method of directly correcting the phase is very unstable because small errors in the estimated velocity value can lead to large errors.

In addition, U.S. Patent Application Publication No. 2018-0011170(A1) (title of the invention: Methods and Apparatus for Velocity Detection in MIMO Radar Including Velocity Ambiguity Resolution) estimates the Doppler phase caused by the movement of the target and then adjusts the angle by this value. After correcting the phase value of the transmitting antenna, a technology for estimating the target's speed and angle information through signal processing is initiated. When this technology directly corrects the phase value, a large error may occur even if there is a slight error in the corrected phase value.

1. U.S. Patent Application Publication No. 2018-0011170 (A1)

1. K. Thurn, D. Shmakov, G. Li, S. Max, M. Meinecke, and M. Vossiek, “Concept and implementation of a PLL-controlled interlaced chirp sequence radar for optimized range-Doppler measurements,” IEEE Trans . Microw. Theory Tech., vol. 64, no. 10, pp. 3280-3289, Oct. 2016. 2. Y. Li, C. Xu, X. Yan, and Q. Liu, “An improved algorithm for Doppler ambiguity resolution using multiple pulse repetition frequencies,” in Int. Conf. Wirel. Commun. Signal Process., Nanjing, China, 2017, pp. 1-5. 3. H. A. Gonzalez, C. Liu, B. Vogginger, and C. G. Mayr, “Doppler ambiguity resolution for binary-phase-modulated MIMO FMCW radars,” in Int. Radar Conf., Toulon, France, 2019, pp. 1-6.

To solve this problem, the present invention uses the phase information of the received signal in a MIMO radar system to exclude ghost target signals and distinguish the actual target signal for each transmit antenna, eliminating Doppler-angle ambiguity without reducing the maximum detection speed. The purpose is to provide a MIMO radar-based target detection method and system that can estimate the target's speed at the original detection speed and at the same time accurately and efficiently estimate the target's angle regardless of whether the target is moving. .

The problems to be solved by the present invention are not limited to the above-described problems, and may be expanded in various ways without departing from the spirit and scope of the invention.

A target detection method based on phase information of a MIMO radar signal according to embodiments for realizing the purpose of the present invention is a target detection method using a MIMO radar system, where a radar transmission signal transmitted through a plurality of transmission antennas is a target. Simultaneously receiving signals reflected and returned through a plurality of receiving antennas; finding a peak in the distance-velocity detection result of each received signal through predetermined signal processing on the received signals from each of the plurality of receiving antennas and extracting phase information of the corresponding peak; and arranging the phase values of the distance-velocity peaks extracted from the received signals of all the plurality of receiving antennas to form an arithmetic sequence and classifying the received signals for each transmitting antenna based on the phase value sequence arranged in the arithmetic sequence. Includes steps.

According to an exemplary embodiment, the step of extracting the phase information includes the intermediate frequency (IF) band signal of the cos channel (I channel) and the intermediate frequency (IF) of the sin channel (Q channel) obtained through signal processing of the received signal. ) Obtaining distance-velocity detection results for each target by applying a two-dimensional fast Fourier transform (2D FFT) to the band signal; and applying a constant false alarm rate (CFAR) algorithm to the distance-speed detection result to extract distance-velocity peaks corresponding to each target and phase values of the peaks.

According to an exemplary embodiment, the radar transmission signal may be a signal modulated by PSK modulation.

According to an exemplary embodiment, the plurality of transmitting antennas and the plurality of receiving antennas may be an antenna array arranged in a ULA form.

According to an exemplary embodiment, in the step of classifying each transmission antenna, when there are two transmission antennas, the preceding sub-phase sequence among the phase sequences of the distance-velocity peaks forming the arithmetic sequence is the first transmission Corresponding to signals transmitted from the antenna, a latter phase sequence may be determined to correspond to signals transmitted from the second transmit antenna. Here, each sub-phase sequence is a sequence of phases equal to the number of receiving antennas.

According to an exemplary embodiment, in the step of classifying each transmission antenna, if there are N transmission antennas (N is a natural number of 3 or more), the kth phase sequence of distance-velocity peaks forming an arithmetic sequence (here, k is a natural number from 1 to N) The sub-phase sequence may be determined to correspond to signals transmitted from the kth transmission antenna. Here, each sub-phase sequence is a sequence of phases equal to the number of receiving antennas.

According to an exemplary embodiment, the target detection method based on phase information of the MIMO radar signal calculates estimated information about the speed and angle of each target using the received signal divided for each transmit antenna after the classification step. Additional steps may be included.

According to an exemplary embodiment, the angle of each target may be estimated by applying fast Fourier transform to the phase sequence for each target.

According to an exemplary embodiment, the radar transmission signal may be a chirp signal whose frequency increases with time.

Meanwhile, a target detection system based on phase information of a MIMO radar signal according to embodiments for realizing the purpose of the present invention includes a plurality of transmitting antennas, a plurality of receiving antennas, a transmitter, a receiver, a digital signal processor, and a distance/speed detector. It may include a government, and an angle estimator. The transmitter is configured to generate a radar transmission signal and transmit it wirelessly through the plurality of transmission antennas. The receiver uses the received signal reflected by the target in front and received through the plurality of receiving antennas, the transmitted signal, and a 90-degree phase-shifted signal of the transmitted signal to an intermediate frequency (IF) of the cos channel (I channel). ) band signal and an intermediate frequency (IF) band signal of the sin channel (Q channel). The digital signal processing unit is configured to perform filtering and fast Fourier transform (FFT) processing on the intermediate frequency band signal of the cos channel (I channel) and the intermediate frequency band signal of the sin channel (Q channel). The distance/speed estimator detects distance-speed peaks using the signal processed by the digital signal processor and extracts the phase value of each peak, arranges the extracted phase values to form an arithmetic sequence, and arranges them in an arithmetic sequence. Based on the phase value sequence, the correspondence between the received signals and each transmitting antenna is determined, the received signal is classified by transmitting antenna, and the target distance and speed are estimated using the received signal classified by each transmitting antenna. It is configured to perform processing.

According to an exemplary embodiment, the distance/speed estimator applies a constant false alarm rate (CFAR) algorithm to the signal processed by the fast Fourier transform (FFT) in the digital signal processor to determine the distance- It may be configured to extract velocity peaks and phase values of the peaks.

According to an exemplary embodiment, when there are two transmission antennas, the distance/speed estimator is configured to transmit a preceding sub-phase sequence among the phase sequences of the distance-velocity peaks forming an arithmetic sequence from the first transmission antenna. Corresponding to the signals transmitted from the second transmitting antenna, a latter phase sequence may be configured to determine that corresponding to the signals transmitted from the second transmit antenna. Here, each sub-phase sequence is a sequence of phases equal to the number of receiving antennas.

According to an exemplary embodiment, the distance/speed estimator, when there are N transmitting antennas (N is a natural number of 3 or more), the kth phase sequence of distance-speed peaks forming an arithmetic sequence (where k is 1) to N) may be configured to determine that the sub-phase sequence corresponds to signals transmitted from the kth transmit antenna. Here, each sub-phase sequence is a sequence of phases equal to the number of receiving antennas.

According to an exemplary embodiment, the target detection system based on phase information of the MIMO radar signal includes an angle estimation unit configured to calculate the angle information of each target by applying a predetermined angle estimation algorithm using received signals divided for each transmission antenna. More may be included.

According to an exemplary embodiment, the angle estimator may be configured to estimate the angle of each target by applying fast Fourier transform to the phase sequence for each target.

According to an exemplary embodiment, the plurality of transmitting antennas and the plurality of receiving antennas may be an antenna array arranged in a ULA form.

According to an exemplary embodiment, the radar transmission signal may be a chirp signal whose frequency increases with time.

In the range-speed detection results of the BPSK-MIMO radar system, each target appears overlapping as many as the number of transmitting antennas. That is, one real target and several ghost targets are detected. In order to distinguish between real targets and ghost targets in the received signals of the BPSK-MIMO radar system, the idea is used that the phase values of the peak signals corresponding to the real targets and ghost targets must have the form of an arithmetic sequence. Therefore, by properly arranging the phase values of these peaks in the received signal into an arithmetic sequence, it is possible to determine which transmitting antenna each target was generated from. That is, after distinguishing between the peak corresponding to the actual target and the peak corresponding to the ghost target in the received signal, the correct speed of the target can be estimated using the arranged phase values, and angle estimation can also be performed at the same time.

According to exemplary embodiments of the present invention, it can be implemented in a digital signal processor of an existing radar system without installing additional hardware. The target's speed and angle estimation performance can be improved through signal processing. In other words, it can be simply implemented in an existing digital signal processor. Two-dimensional (2D) Fast Fourier Transform (FFT) for distance-velocity estimation is an essential signal processing that must be performed in an FMCW radar system, and only an algorithm for sorting phase values needs to be additionally implemented.

The present invention can solve the problem of lower maximum detection speed that occurs when using multiple transmit antennas.

The present invention can also solve the problem of angle estimation performance degradation caused by target movement because it uses signals received simultaneously at each receiving antenna. That is, the present invention uses signals received simultaneously, unlike the TDM method in which signals are received alternately, and thus can solve the problem of angle estimation inaccuracy due to movement of the object between different time slots.

1 is a block diagram showing the configuration of a BPSK-MIMO FMCW radar system according to an exemplary embodiment of the present invention.
Figure 2 illustrates the transmitted signal waveform of the FMCW radar system.
Figure 3 schematically shows an angle estimation method for a target using a Uniform Linear Array (ULA) antenna system.
Figure 4 illustrates angle estimation using a MIMO ULA antenna system.
Figure 5 shows the transmitted signal of a BPSK-MIMO radar system using two transmit antennas.
Figure 6 shows the distance-speed estimation results from a simulation using a BPSK-MIMO radar system equipped with two transmit antennas.
Figure 7 shows the distance-speed estimation results of a simulation using a BPSK-MIMO radar system with four transmit antennas instead of two transmit antennas.
Figure 8 shows angle estimation results for the case of a stationary target (A) and a non-stationary target (A).
Figure 9 shows the overall procedure of applying the method for classifying received signals by transmission antenna according to an exemplary embodiment of the present invention.
Figure 10 shows a process for estimating the speed and angle of a target by dividing received signals by transmission antenna through signal processing using a processor according to an exemplary embodiment of the present invention.
Figure 11 shows simulated distance-velocity estimation results using two transmit antennas and four receive antennas according to an exemplary embodiment of the present invention: (A) is a three-dimensional view, and (B) is a top-down view. It is a two-dimensional diagram.
Figure 12 shows the unwrapped phase values of eight virtual antennas corresponding to the phase sequences [P _a P _b ] and [P _d P _c ].
Figure 13 shows the results of estimating the angles of the first and second targets by applying FFT to the phase sequence arranged in an arithmetic sequence.
Figure 14 shows the unwrapped phase values of eight virtual antennas for various SNRs.
Figure 15 shows the transmission signal of a 3-PSK MIMO radar system using three transmit antennas.
Figure 16 shows range-velocity estimation results simulated using a 3-PSK MIMO radar system with three transmit antennas and four receive antennas according to an exemplary embodiment of the present invention: (A) is a three-dimensional diagram; , (B) is a two-dimensional diagram viewed from above.

Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the attached drawings. The same reference numerals are used for the same components in the drawings, and duplicate descriptions for the same components are omitted.

The terms used in the present invention are only used to describe specific embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, terms such as “comprise” or “have” are intended to designate the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, but are not intended to indicate the presence of one or more other features. It should be understood that this does not exclude in advance the possibility of the existence or addition of elements, numbers, steps, operations, components, parts, or combinations thereof. Additionally, terms such as first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The above terms are used only for the purpose of distinguishing one component from another.

1 is a block diagram showing the configuration of a BPSK-MIMO FMCW radar system according to an exemplary embodiment of the present invention.

Referring to FIG. 1, the BPSK-MIMO FMCW radar system 10 includes a transmitter 20 and a transmit antenna 30 connected thereto, a receiver 40 and a receive antenna 50 connected thereto, and a digital signal processor 60, It may include a distance/speed estimator 70 and an angle estimator 80.

The transmitter 20 may include a signal generator 22 and an oscillator 24. The signal generator 22 and the oscillator 24 may be configured to generate a chirp signal whose frequency increases with time and transmit it wirelessly through the transmission antenna 30. Specifically, the waveform generator 22 can generate an analog signal with a desired period and shape based on the provided transmission information (digital). For example, the signal generator 22 may provide a modulated signal (triangular wave) in a triangular waveform to the oscillator 24. The oscillator 24 can convert the signal provided by the waveform generator 24 into a chirp signal whose frequency increases with time for wireless transmission. The chirp signal can be amplified to the output required for wireless transmission and transmitted through the transmitting antenna 30. The oscillator 24 may be configured as, for example, a voltage control oscillator (VCO).

The signal transmitted in this way may be reflected by a surrounding target and received through the receiving antenna 50. Components of the receiving unit 40 may form a cos channel (I channel) and a sin channel (Q channel) connected to the receiving antenna 50. The cos channel (I channel) may include a first mixer (41), a first low-pass filter (LPF, 44), and a first analog-to-digital converter (ADC, 46), and the sin channel (Q channel) may also include It may include a second mixer 43, a second low-pass filter 45, and a second analog-to-digital converter (ADC, 47). In the cos channel (I channel), the first mixer 41 is connected to the receiving antenna 50 and the oscillator 24 and multiplies the received signal with the chirp signal used for transmission. When two sinusoidal signals are multiplied in the first mixer 41, a high-frequency signal and a low-frequency signal are generated, and the high-frequency signal can be removed through the first LPF 44. The first ADC 46 can convert an analog signal into a digital signal through sampling of the output signal of the first LPF 44. The same signal processing as in the cos channel (I channel) can be performed in the sin channel (Q channel). However, the chirp signal used for transmission (i.e., the output signal of the oscillator 24) is not provided as is to the second mixer 43, but a chirp signal phase-shifted by 90° through the phase shifter 42 is provided. This is different from signal processing in the cos channel (I channel). In this way, the first mixer 41 multiplies the received signal by the chirp signal for transmission, and the second mixer 43 phases the received signal by shifting the chirp signal by 90 degrees and then multiplies it, thereby producing a cos channel (I channel) signal and sin channel (Q channel) signal can be formed.

The digital signal processing unit 60 may perform various digital signal processing (windowing, filtering, FFT, etc.) on the signal that has passed through the first and second ADCs 46 and 47 of the receiving unit 40. In particular, 2D FFT can be performed on digitized cos channel (I channel) signals and sin channel (Q channel) signals.

The digital signal processed in the digital signal processing unit 60 is provided to the distance/speed estimator 70 to estimate the distance and speed of the target, and is also provided to the angle estimator 80 to estimate the angle of the target. You can. In particular, the distance/speed estimation unit 70 detects peaks in the distance-speed domain by applying the CFAR algorithm to the 2D FFT processed signal and extracts the phase value of each peak, and the extracted phase values are converted into an arithmetic sequence. Arranged to form an arithmetic sequence, determine the correspondence relationship between the received signals and each transmitting antenna based on the phase value sequence arranged in an arithmetic sequence, process to classify the received signals for each transmitting antenna, and receive signals classified for each transmitting antenna. You can use to perform processing to estimate the distance and speed of the target. The angle estimation unit 80 can also calculate the angle information of each target by applying an angle estimation algorithm using received signals classified for each transmission antenna.

The digital signal processing unit 60, the distance/speed estimating unit 70, and the angle estimating unit 80 include hardware such as the processing unit 90 and a program that can be executed on the processing unit 90 (this program will be described later). The algorithm of the method according to the embodiment of the present invention is implemented as a computer program. The processing unit 90 may include, for example, a processor, a controller, an arithmetic logic unit (ALU), a digital signal processor, a microcomputer, a field programmable array (FPA), a programmable logic unit (PLU), a microprocessor, or Like any other device capable of executing and responding to instructions, it may be implemented using one or more general-purpose or special-purpose computers. Processing device 90 may execute an operating system (OS) and one or more software applications running on the operating system. Additionally, a processing device may access, store, manipulate, process, and generate data in response to the execution of software.

Next, the basic operating principle of the BPSK-MIMO FMCW radar system 10 will be described in more detail. FMCW radar transmits periodic chirp signals where each frequency increases linearly with time. The transmitted signal for a single chirp can be expressed as:

......(One)

where f _c , B and T _c represent the carrier frequency, bandwidth and duration of the chirp signal, respectively.

Figure 2 shows the transmission signal waveform of the FMCW radar system. As shown in Figure 2, transmission by the transmitter 20 is repeated for L consecutive chirps. Then, the signal reflected by the target and received by the receiver 40 is multiplied by the transmitted signal to remove the carrier frequency component. The resulting intermediate frequency (IF) band signal can be expressed as a 2D exponential function as follows.

......(2)

Here, n and N represent the sampling index and sampling number within each chirp, and l and L represent the chirp index and number of chirps within each chirp. Additionally, R and v represent the distance and speed of the target, T _s represents the sampling period, c represents the speed of light, and ϕ represents the fixed phase component. This IF band signal has frequencies of 2BR/T _c c and 2v/λ along the n- and l-axes, respectively. Therefore, by applying the 2D Fourier transform to equation (2), the distance and speed of the target can be estimated.

Additionally, angle estimation can be achieved using a Uniform Linear Array (ULA) antenna system. Figure 3 shows the angle estimation of the target using the ULA antenna system (1 transmitting antenna, 8 receiving antennas). In the ULA antenna system 100 illustrated in FIG. 3, the antenna spacing of the plurality of receiving antennas (Rx1 - Rx8) is d, and is transmitted from one transmitting antenna (Tx1) and reflected by the target to receive the receiving antennas (Rx1 - When the wavelength and incidence angle of the received signal received through Rx8) are λ and θ, respectively, the phase difference (ω) between adjacent receiving antennas can be expressed as ω= 2π(d sinθ)/λ. This phase term ω can be integrated into equation (2) to create a three-dimensional IF band signal that can be expressed as:

......(3)

Here, p is the antenna index, and P is the number of receiving antennas (Rx1 - Rx8). This signal is commonly known as a radar data cube. By applying the Fourier transform to each dimension of the radar data cube, the target's range, speed, and angle can be estimated.

Figure 4 illustrates angle estimation using a MIMO ULA antenna system. In a MIMO radar system, multiple transmitting and receiving antennas arranged in a ULA form can be used to improve radar detection performance. For example, Figure 4 shows the MIMO ULA antenna configuration of a MIMO radar system with two transmit antennas (Tx1, Tx2) and four receive antennas (Rx1 - Rx4). Since the signal transmitted from the second transmitting antenna (Tx2) moves a distance of 4d sinθ compared to the signal transmitted from the first transmitting antenna (Tx1), the phase of the received signal transmitted from the second transmitting antenna (Tx2) is 1 The phase of the received signal transmitted from the transmitting antenna (Tx1) is higher by 2π(4d sinθ)/λ. As a result, the angle estimation performance of the antenna configuration shown in FIG. 4 is similar to that of the antenna configuration shown in FIG. 3. The main advantage of the MIMO antenna method is that the overall number of antenna elements can be reduced.

To get the most out of a MIMO antenna system, signals transmitted from different transmit antennas must be distinguished. For example, in the case of FIG. 4, it is necessary to distinguish in the received signal which signal component is transmitted from the first transmission antenna (Tx1) and which signal component is transmitted from the second transmission antenna (Tx2). To solve this problem, various multiplexing methods such as TDM, FDM, and CDM exist. Among these various technologies, BPSK is a method of modulating the phase of a transmission signal using a pre-assigned code. This code is specifically designed so that the transmitted signals are orthogonal to each other.

Figure 5 shows the transmitted signal of a BPSK-MIMO radar system using two transmit antennas. Signals (A) and (B) may be transmitted through the first and second transmission antennas, respectively. When code 1 is assigned to the chirp, the phase of the transmission signal is modulated to 0, which means that the signal represented by equation (4) below is transmitted.

......(4)

On the other hand, if a code of 0 is assigned to the chirp, the phase of the transmission signal is modulated by π and the signal in equation (5) below is transmitted.

......(5)

As shown in FIG. 5, when the first transmission antenna (Tx1) transmits with a code of 1111 and the second transmission antenna (Tx2) transmits with a code of 1010, the received signal with an odd index is r _odd (t) = r ₁ ( It can be expressed as t) + r ₂ (t), and the received signal of an even index can be expressed as r _even (t) = r ₁ (t) - r ₂ (t). Here, r ₁ (t) represents the signal component received from the first transmission antenna (Tx1), and r ₂ (t) represents the signal component received from the second transmission antenna (Tx2). Therefore, the received signal from each transmit antenna can be decomposed through the following decoding process.

......(6)

......(7)

Meanwhile, detecting a target using a BPSK-MIMO radar system mainly involves estimating the target's range, velocity, and angle. In the BPSK-MIMO radar system, distance estimation is performed similarly to a typical FMCW radar system. However, when using traditional velocity and angle estimation methods, problems arise due to the Doppler-angle ambiguity of MIMO systems.

In FMCW radar systems, target velocity estimation is performed using the phase difference between several chirp signals. For example, in the existing FMCW radar system, as observed in Equations (2) and (3), the phase between adjacent chirps differs by 2π(2v/λ)T _c , and the speed is the difference between multiple chirp signals. It is estimated using phase increments. However, the signal received in the BPSK-MIMO radar system consists of multiple signal components from multiple transmit antennas, and the phase increment cannot be simply expressed as 2π(2v/λ)T _c . ........(8)

Equation (8) represents the received signal of the first receiving antenna (Rx1) when the antenna configuration as shown in FIG. 4 is set and the transmission signal is modulated as shown in FIG. 5. In equation (8), the first term represents a typical received signal with a phase increment of 2π(2v/λ)T _c . However, the second term includes a sign inversion, so the phase increases by 2π(2v/λ)T _c +π. As a result, when 2D Fourier transform is applied to the IF band signal, two peaks occur in the distance-speed detection result.

Simulations were performed using the previously mentioned antenna configuration, assuming three targets moving in the radar's field of view. Figure 6 shows the distance-speed estimation results from a simulation using a BPSK-MIMO radar system equipped with two transmit antennas. It shows the distance-speed estimation results obtained through this simulation. The simulation parameters were set as shown in Table 1 using existing automotive radar parameters. As a result, the maximum detectable velocity of ㅁλ/(4T _c ) = ㅁ19.48 m/s was obtained. Additionally, the SNR was set to 0dB, and the distance and speed of the targets were set to (30m, 12m/s), (50m, 4m/s), and (60m, -3m/s), respectively.

As can be seen in Figure 6, two peaks occur in the distance-velocity detection results for each target, resulting in Doppler ambiguity. This is because one peak is generated by the signal of the first transmission antenna (Tx1), and the other peak is generated by the signal of the second transmission antenna (Tx2). For example, in the case of a target located 30m away, a peak occurred at 12m/s due to the transmission signal from the first transmission antenna (Tx1), and another peak occurred due to the signal from the second transmission antenna (Tx2). Occurred at 12-19.48 = -7.48 m/s. Similar results were observed for the remaining targets, whose speeds were not uniquely determined. As a result, the maximum detectable speed was reduced by half, from 19.48 m/s to 9.74 m/s.

The previous results can be extended to BPSK-MIMO radar systems consisting of two or more transmit antennas. Figure 7 shows the distance-speed estimation results of a simulation using a BPSK-MIMO radar system with four transmit antennas instead of two transmit antennas. Except for the number of transmitting antennas, the radar system parameters and target information were set the same as in FIG. 6. Additionally, the phases of signals transmitted from the four transmit antennas were coded using the Hadamard coding method. This method uses four transmit antennas with codes of (1, 1, 1, 1), (1, 0, 1, 0), (1, 1, 0, 0), and (1, 0, 0, 1). send. And the received signals from each transmission antenna can be decomposed using orthogonality between codes.

As shown in Figure 7, four peaks occurred in the distance-velocity detection results for each target, and the maximum detectable speed was reduced to one fourth. In general, when multiplexing is performed by dividing time slots, the maximum detectable speed decreases by the number of transmission antennas. This significantly degrades speed estimation performance. This may be undesirable, especially in automotive applications where very fast detection speeds for targets are required. Therefore, in order to resolve Doppler ambiguity and maintain the maximum detectable speed for the target, the correspondence between the peak and the transmit antenna must be determined.

Next, the existing angle estimation method using the BPSK-MIMO radar system is as follows. In the MIMO radar system, as described above, the signal from each transmitting antenna must be distinguished when estimating the target angle. To this end, the decoding process of equations (6) and (7) can be applied to the signal received from the BPSK-MIMO radar system. However, when the target is a non-stationary target, the signals from each transmitting antenna cannot be properly distinguished due to the velocity-induced phase term. For example, when the decoding process is applied to the received signal shown in equation (8), the resulting signal is:

......(9)

......(10)

Due to the velocity-induced phase term 2π(2v/λ)T _c , unnecessary elements cannot be canceled out and signals from each transmit antenna cannot be properly distinguished.

Figure 8 shows angle estimation results for the case of a stationary target (A) and a non-stationary target (A). Referring to Figure 8, the angle was set to -20°, and the speed was set to 0 m/s and 15 m/s, respectively. As shown, the angle of the target was appropriately estimated when the target was stationary. The FFT method can be used for angle estimation. When using the FFT method, there may be some error in the estimated angle. Although more complex algorithms such as MUSIC or ESPRIT can be used to improve estimation accuracy, the FFT method is useful for fast calculations. However, when the target moves, a large error occurs in estimating the angle of the target.

To solve this problem, the phase of the received signal can be compensated to remove the velocity-induced phase term in the time domain or frequency domain. The target's speed was first estimated in the time domain and frequency domain, and then the phase of the received signal was compensated by -(2v/λ)T _c using the estimated speed value. However, this phase compensation method can cause large errors even if the estimated speed value is slightly different from the actual value. For example, if the velocity resolution is v _res , the velocity bins are divided into intervals of v _res and the estimated velocity may deviate from the actual value by v _res /2, regardless of noise. Velocity resolution can be defined as λ/(2LT _c ) in FMCW radar systems. Therefore, the compensated phase value is It can be offset by This value is Since it is of a similar order to , the target angle cannot be estimated with certainty even if phase compensation is applied.

Exemplary embodiments of the present invention provide a method for efficiently distinguishing received radar signals for each transmit antenna to solve the above-mentioned problems, especially Doppler-angle ambiguity, when estimating the speed and angle of a target. Below, the method is described in detail.

In order to distinguish the signal of each transmitting antenna, the inventors pay attention to the fact that the phase of the peak in the distance-velocity detection result of the received signal forms an arithmetic sequence as shown in FIG. 3. For example, as shown in FIG. 4, in a MIMO FMCW radar system in which two transmit antennas (Tx1, Tx2) and four receive antennas (Rx1 - Rx4) are provided in the form of a ULA, the first transmit antenna (Tx1) transmits and the second transmits. 1 When the phase (P _a1 ) value of the signal received at the receiving antenna (Rx1) is ϕ, the phases (P _a1 - P _a4 , P _b1 - P _b4 ) of the remaining received signals including this can be expressed as follows. .

Tx1 → Rx1 : P _a1 = ϕ

Tx1 → Rx2 : P _a2 = ϕ+ω

Tx1 → Rx3 : P _a3 = ϕ+2ω

Tx1 → Rx4 : P _a4 = ϕ+3ω

Tx2 → Rx1 : P _b1 = ϕ+4ω

Tx2 → Rx2 : P _b2 = ϕ+5ω

Tx2 → Rx3 : P _b3 = ϕ+6ω

Tx2 → Rx4 : P _b4 = ϕ+7ω ......(11)

These phase values form an arithmetic sequence. For example, in the above example, when the two phase sequences of peaks in the distance-velocity plane of the received signal transmitted and received from the two transmit antennas (Tx1, Tx2) form an arithmetic sequence, the preceding sub-phase sequence among the phase sequences The (former phase sequence) corresponds to signals transmitted from the first transmission antenna (Tx1), and the subsequent sub-phase sequence (latter phase sequence) corresponds to signals transmitted from the second transmission antenna (Tx2). Here, each sub-phase sequence is a sequence of phases equal to the number of receiving antennas. For example, when the received signal phase sequence [P _a1 P _a2 P _a3 P _a4 P _b1 P _b2 P _b3 P _b4 ] forms an arithmetic sequence, the preceding phase sequence [P _a1 P _a2 P _a3 P _a4 ] is the first transmitting antenna. Corresponds to signals transmitted from (Tx1), and the trailing phase sequence [P _b1 P _b2 P _b3 P _b4 ] corresponds to signals transmitted from the second transmit antenna (Tx2). If the phase sequence [P _b1 P _b2 P _b3 P _b4 P _a1 P _a2 P _a3 P _a4 ] forms an arithmetic sequence, then the preceding phase sequence (first sub-phase sequence) [P _b1 P _b2 P _b3 P _b4 ] is the first. 1 corresponds to the signals transmitted from the transmission antenna (Tx1), and the trailing phase sequence (second sub-phase sequence) [P _a1 P _a2 P _a3 P _a4 ] corresponds to the signals transmitted from the second transmission antenna (Tx2) do. The phase information of the received signals arranged in this arithmetic sequence can be used to determine the correspondence between the received signals and the transmitting antennas.

Figure 9 shows the overall procedure of applying a method for classifying received signals by transmission antenna according to an exemplary embodiment. This method can be performed using the MIMO FMCW radar system 10 shown in FIG. 1.

Referring to FIG. 9, first, in the MIMO FMCW radar system, the transmitter 20 can generate a radar signal to be transmitted and transmit it to the transmit antenna array 30 (S100). The transmitted radar signal may be, for example, a signal modulated using the PSK method, and as a representative example, it may be a signal modulated using the BPSK modulation method.

The transmitted radar signal may be reflected by targets existing within the viewing angle range and received through the receiving antenna array 50 of the MIMO FMCW radar system 10. After the received signals undergo predetermined signal processing, processing to extract phase information of each received signal may be performed (S200).

In step S200, the receiving unit 40 of the MIMO FMCW radar system 10 receives each received signal from the receiving antenna array 50 and receives a transmitted signal from the transmitting unit 20. To obtain a cos channel (I channel) signal, the received signal and the transmitted signal are multiplied in the first mixer 41, the high frequency signal included in the multiplied signal is removed by the first LPF 44, and then the first ADC ( 46) is used to convert it into a digital signal. To obtain a sin channel (Q channel) signal, the transmission signal provided from the transmitter 20 is phase-shifted by 90 degrees and then multiplied by the received signal in the second mixer 43. The high frequency signal included in the multiplied signal is removed by the second LPF (45) and then converted into a digital signal using the second ADC (47). Through this signal processing, a cos channel (I channel) signal and a sin channel (Q channel) signal can be obtained from the receiving unit 40 and provided to the digital signal processing unit 60. The digital signal processing unit 60 can perform various digital signal processing (windowing, filtering, FFT, etc.) on the signals that have passed through the first and second ADCs 46 and 47. The received signal processed in this way is provided to the distance/speed estimator 70, and the phase information of each received signal can be extracted.

Figure 10 shows a process of estimating the speed and angle of the target by dividing received signals by transmission antenna through signal processing using the processing device 90 according to an exemplary embodiment of the present invention.

Referring to FIG. 10, in order to extract phase information of radar reception signals received through the reception antenna array 50 and subjected to predetermined signal processing in the reception unit 40, a 2D signal is first applied to the IF band signal received from each reception antenna. FFT can be applied (S210). Through this process, for example, due to the characteristics of BPSK modulation, it is possible to obtain distance-velocity detection results in which each target is duplicated (i.e., a ghost target is detected in addition to the actual target of each target).

Then, for example, the constant false alarm rate (CFAR) algorithm can be applied to extract the distance-velocity peak value corresponding to each target and the phase information of the peak value. For example, as a result of phase extraction of distance-velocity peak values using the CFAR algorithm, the first receiving antenna (Rx1), the second receiving antenna (Rx2), the third receiving antenna (Rx3), and the fourth receiving antenna (Rx4) are The phase information of each distance-velocity peak value may be [P _a1 , P _b1 ], [P _a2 , P _b2 ], [P _a3 , P _b3 ], and [P _a4 , P _b4 ]. The phase information of the extracted peak value may be recorded in a storage means (S220).

Then, the phase values of the extracted distance-velocity peaks can be arranged to form an arithmetic sequence (S230). The eight phase values of Equation (10), that is, the phase values (P _a1 - P _a4 , P _b1 - P _b4 ) of the extracted distance-velocity peaks, are arranged to form an arithmetic sequence (S230). In the above example, the combination of _phase values extracted from the signals received through the first to fourth receiving antennas (Rx1 - Rx4) is [P _a1 P _a2 P _a3 P _a4 P b1 P _b2 P _b3 P _b4 ] and [ P _b1 P _b2 P _b3 P _b4 P _a1 P _a2 P _a3 P _a4 ] may exist. Among these, only one combination can form an arithmetic sequence.

Once the phase value sequence arranged to form an arithmetic sequence is obtained, the received signals received through the receive antenna array 50 can be distinguished for each transmit antenna based on the phase value sequence arranged as an arithmetic sequence (S300). In other words, it is possible to determine which distance-velocity peak corresponds to which transmit antenna. In particular, the first sub-phase sequence corresponds to the signal from the first transmit antenna, the second sub-phase sequence corresponds to the signal from the second transmit antenna, and so on for the third and subsequent sub-phase sequences. It must belong to signals from the following transmitting antennas. Here, each sub-phase sequence is a sequence of phases equal to the number of receiving antennas. That is, when there are N transmitting antennas (N is a natural number of 2 or more), the kth (where k is a natural number from 1 to N) phase sequence corresponds to a signal from the kth transmitting antenna (Txk). Using this relationship, the peak corresponding to the actual target and the peak corresponding to the ghost target can be determined, and ultimately the received signals can be distinguished for each transmitting antenna. For example, if the phase sequence [P _a1 P _a2 P _a3 P _a4 P _b1 P _b2 P _b3 P _b4 ] forms an arithmetic sequence, the four preceding phases [P _a1 P _a2 P _a3 P _a4 ], that is, the first sub-phase The sequence represents the phases of four received signals transmitted from the first transmitting antenna (Tx1) and received through the first to fourth receiving antennas (Rx1 - Rx4), and the following four phases [P _b1 P _b2 P _b3 P _b4 ] That is, the second sub-phase sequence represents the phases of four received signals transmitted from the second transmitting antenna (Tx2) and received through the first to fourth receiving antennas (Rx1 - Rx4). Here, when the wavelength and incident angle of the received signal are λ and θ, respectively, the phase difference (ω) between adjacent antennas is am.

Based on the above principle, the signals received through the receiving antenna array 50 are classified into signals for each transmitting antenna, and then a speed and angle estimation algorithm is applied to the received signals classified for each transmitting antenna to identify each target. Estimated information about speed and angle can be calculated (S400). Since it is possible to know which transmitting antenna the signal received at each receiving antenna is from, the so-called Doppler angle ambiguity in speed and angle estimation is resolved and accurate estimation can be made.

Figure 11 shows simulated distance-velocity estimation results using two transmit antennas and four receive antennas according to an exemplary embodiment of the present invention: (A) is a three-dimensional view, and (B) is a top-down view. It is a two-dimensional diagram.

Referring to FIG. 11, two transmitting antennas (Tx1, Tx2) and four receiving antennas (Rx1 - Rx4) were used in the simulation, and the simulation parameters were set according to Table 1. To prove that the proposed method can be applied when there are multiple targets in the same range bin, the distance, speed, and angle of the two targets are (30m, -15m/s, 20°) and (30m, 8m/s, -12°), respectively. The phase of the distance-velocity peak obtained using the CFAR algorithm is shown in the figure. In the received signals of the receiving antennas (Rx1 - Rx4), two peaks occurred for each target as shown, resulting in a total of four distance-velocity peaks. Since Doppler ambiguity results in another peak shifted by half the maximum detectable velocity, (distance, velocity) = (30m, -15m/s) and (30m, 4.48m/s) are due to the first target. , (distance, speed) = (30m, -11.48m/s) and (30m, 8m/s) are due to the secondary target. Therefore, the Doppler ambiguity of the two targets can be resolved independently.

First, check whether the actual speed of the first target is -15m/s or 4.48m/s. The phase sequence corresponding to the peak position (30m, -15m/s) is P _a = [40.23° 101.43° 166.01° -134.15°], and the phase sequence corresponding to the peak position (30m, 4.48m/s) is P _b = [-72.99° -10.48° 51.01° 110.53°]. By arranging these two topological sequences, we can see that the cascaded sequence [P _a P _b ]=[40.23° 101.43° 166.01° -134.15° -72.99° -10.48° 51.01° 110.53°] forms a substantial arithmetic sequence. You can see that Therefore, it can be determined that P _a corresponds to the signal of the first transmission antenna (Tx1) and P _b corresponds to the signal of the second transmission antenna (Tx2). Additionally, the signal of the first transmission antenna (Tx1) is a normal FMCW signal, and the signal of the second transmission antenna (Tx2) is a sign-inverted FMCW signal. Therefore, it can be concluded that -15m/s represents the actual speed of the target, and 4.48m/s corresponds to a ghost target due to sign inversion of the second transmitting antenna (Tx2). By distinguishing the signal from each transmit antenna in this way, Doppler ambiguity was resolved and the target's velocity was uniquely determined without halving the maximum detection rate.

Next, the same process is repeated to determine whether the actual speed of the second target is -11.48 m/s or 8 m/s. The phase sequence corresponding to the peak position (30 m, -11.48 m/s) is P _c = [3.26° -34.72° -75.04° -111.81°], and the phase sequence corresponding to the peak position (30 m, 4.48 m/s) was P _d = [152.18° 112.91° 75.75° 40.42°]. Since the cascade sequence [P _d P _c ] forms an arithmetic sequence, it can be determined that the phase sequence P _d corresponds to the signal of the first transmitting antenna (Tx1), and the actual speed of the target is 8 m/s.

Figure 12 shows the unwrapped phase values of eight virtual antennas corresponding to the phase sequences [P _a P _b ] and [P _d P _c ]. To prevent discontinuity by making the difference between consecutive phase values less than 180°, the phase values were not wrapped (unwrap). It is clear from the figure that a correctly cascaded phase sequence forms an arithmetic sequence.

Angle estimation can also be performed simultaneously using an arrayed phase sequence. The angle of each target can be estimated by applying fast Fourier transform to the phase sequence for each target. Because the signals from each transmit antenna are separated, there are no problems such as moving targets or phase compensation. For example, the angle of the first target corresponding to (30m, -15m/s) can be estimated by applying FFT to the phase sequence [P _a P _b ]. Similarly, FFT can be applied to the phase sequence [P _c P _d ] to estimate the angle of the second target corresponding to (30 m, 8 m/s).

Figure 13 shows the results of estimating the angles of the first and second targets by applying FFT to the phase sequence arranged in an arithmetic sequence.

Referring to FIG. 13, the angles of the first and second targets were estimated to be 20° and -12°. It can be seen that this estimated angle exactly matches the actual angles of the first and second targets.

Additionally, the performance of the proposed method was analyzed by varying the SNR. Figure 14 shows the unwrapped phase values of eight virtual antennas for various SNRs. When the SNR is 0dB, the unwrapped phase forms a straight line, indicating that the phase sequence forms an arithmetic progression. Even when the SNR was -20 dB, which was much lower than the SNR in real scenarios, the non-wrapping phase values showed similar results. On the other hand, when the SNR was -40dB and the target angle was not accurately estimated, a large error occurred.

The present invention can be expanded and applied even when the number of transmission antennas is three or more. For this purpose, a general PSK (Phase-Shift Keying) modulation method can be used, which modulates the phase of the transmitted signal according to the number of transmission antennas. Below, for convenience, a three transmit antenna system is used as an example, but the results can be extended to any number of transmit antennas.

Figure 15 shows the transmission signal of a 3-PSK MIMO radar system using three transmit antennas.

Referring to FIG. 15, when codes of 1, 2, and 3 are assigned to the chirp, the phases of the transmission signal are modulated to 0, 2π/3, and 4π/3, respectively. each. In other words, the signals below are used.

......(12)

......(13)

......(14)

As shown in FIG. 15, the first transmission antenna (Tx1) transmits with a code of 111111, the second transmission antenna (Tx2) transmits with a code of 123123, and the third transmission antenna (Tx3) transmits with a code of 132132. Send. In this case, the received signal can be expressed as equation (15) below.

......(15)

The first term corresponds to a signal transmitted from the first transmitting antenna (Tx1) whose phase increases by 2π(2v/λ)T _c . In addition, the second and third terms correspond to signals transmitted from the second transmission antenna (Tx2) and the third transmission antenna (Tx3), respectively, and the phases are 2π(2v/λ) T _c +2π/3 and 2π (2v/λ)T _c +4π/3 each increases. As a result, when 2D FFT is applied to the IF band signal, three distance-velocity peaks occur in the distance-velocity detection result. One peak corresponds to the actual speed of the target, and the remaining two peaks correspond to ghost targets whose speeds have moved by 1/3 and 2/3 of the maximum detectable speed.

Figure 16 shows range-velocity estimation results simulated using a 3-PSK MIMO radar system with three transmit antennas and four receive antennas according to an exemplary embodiment of the present invention: (A) is a three-dimensional diagram; , (B) is a two-dimensional diagram viewed from above.

Referring to Figure 16, a method for resolving Doppler-angle ambiguity is shown. Assuming there are three transmitting antennas and four receiving antennas, the transmitted signal was modulated as shown in FIG. 15. Additionally, the target's distance, speed, and angle were set to (50m, 14m/s, 15°). As shown in Figure 16, three peaks occurred in the distance-velocity plane due to the characteristics of 3-PSK modulation. To determine which transmitting antenna each of the three peaks corresponded to, an arithmetic sequence check was performed on the obtained phase values. The phase sequence corresponding to the peak location (50 m, -11.97 m/s) was P _a = [-44.54° 2.21° 47.86° 94.98°], and the phase sequence corresponding to the peak location (50 m, 1.01 m/s) was P a _b = [140.71° -172.53° -125.80° -79.10°], and the phase sequence corresponding to the peak position (50 m, 14 m/s) was P _c = [128.34° 174.43° -138.15° -91.51°]. By arranging these three phase sequences P _a , P _b , and P _c , we can see that the cascade phase sequence [P _a P _b P _c ] forms an arithmetic sequence. Therefore, it can be concluded that P _a , P _b , and P _c correspond to signals transmitted from the first transmission antenna (Tx1), the second transmission antenna (Tx2), and the third transmission antenna (Tx3). Since the signal of the first transmitting antenna (Tx1) is a general FMCW signal whose phase increases by 2π(2v/λ)T _c , the actual speed of the target can be estimated to be 14m/s.

Additionally, angle estimation of the target can be performed in a manner similar to FIG. 13 by applying FFT to the phase sequence [P _c P _a P _b ]. Therefore, the method according to an exemplary embodiment of the present invention can be effectively applied to a three-transmission antenna system using the 3-PSK modulation method to resolve Doppler-angle ambiguity. The method of the present invention can be expanded and applied even when the number of transmission antennas is four or more. In other words, in general terms, the method of the present invention can be applied to an N-PSK MIMO radar system (where N is a natural number of 2 or more) to accurately and effectively estimate the distance, speed, and angle to targets while resolving Doppler-angle ambiguity. You can.

The above simulation results could also be confirmed through actual experiments using the FMCW radar sensor. The FMCW radar sensor used in the experiment supports MIMO mode with two transmitting antennas and four receiving antennas, and BPSK modulation can be applied to the transmitted signal. A cascade phase sequence of peaks in the distance-velocity plane measured for both stationary and moving targets formed an arithmetic sequence, and the arithmetic sequence was used to estimate the target's speed and angle without reducing the maximum detectable speed. It was confirmed that the value exactly matched the actual speed and angle. Therefore, the method of distinguishing the signal of each transmitting antenna by modulating the phase of the transmitted signal and arranging the phase of the received signal according to the present invention can estimate a clear speed and angle of the target while resolving Doppler angle ambiguity, and as a result, MIMO The performance of the radar system can be improved.

As explained above, in the BPSK-MIMO FMCW radar system, the distance and speed values corresponding to each target are duplicated as many as the number of transmitting antennas and are detected as ghost targets, resulting in Doppler-angle ambiguity. The method proposed by the present invention solves this problem. You can. In other words, based on the new recognition that the phase values of signals corresponding to the same target in the distance-velocity detection results of each receiving antenna must have the form of an arithmetic sequence, Doppler ambiguity can be resolved by correctly aligning the phase values derived from each target. Even when using multiple transmit antennas, the maximum detectable speed can be maintained using the method according to the present invention, and inaccuracy in angle estimation due to target movement can also be resolved. It was confirmed that the method according to the present invention shows excellent performance using both simulation data and measurement data.

The method according to the embodiment of the present invention described above may be implemented in the form of program instructions that can be executed through the processing device 90 and recorded on a computer-readable medium. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks, and magnetic tapes, optical media such as CD-ROMs and DVDs, and magnetic media such as floptical disks. -Includes optical media (magneto-optical media) and hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, flash memory, etc.

The method and system according to the present invention can be used in radar systems using MIMO antennas. In particular, it can be used to improve target speed and angle estimation performance in MIMO-based FMCW radar systems.

Although the embodiments have been described with limited drawings as described above, those skilled in the art can make various modifications and changes to the present invention without departing from the spirit and scope of the present invention as set forth in the following patent claims. You will understand that it is possible. For example, the described techniques are performed in a different order than the described method, and/or components of the described system, structure, device, circuit, etc. are combined or combined in a different form than the described method, or other components are used. Alternatively, appropriate results may be achieved even if substituted or substituted by an equivalent. Therefore, other implementations, other embodiments, and equivalents to the claims also fall within the scope of the claims described below.

10: BPSK-MIMO FMCW radar system
20: Transmitting unit 30: Transmitting antenna
40: Receiving unit 50: Receiving antenna
60: Digital signal processing unit 70: Distance/speed estimation unit
80: angle estimation unit 90: processing device

Claims (19)

In a target detection method using a MIMO radar system,
Simultaneously receiving a radar transmission signal transmitted through a plurality of transmitting antennas reflected by a target and returning a signal through a plurality of receiving antennas;
finding a peak in the distance-velocity detection result of each received signal through predetermined signal processing on the received signals from each of the plurality of receiving antennas and extracting phase information of the corresponding peak; and
Arranging the phase values of the distance-velocity peaks extracted from the received signals of all the plurality of receiving antennas to form an arithmetic sequence and classifying the received signals for each transmitting antenna based on the phase value sequence arranged in the arithmetic sequence. A target detection method based on phase information of a MIMO radar signal, comprising: The method of claim 1, wherein the step of extracting the phase information includes the intermediate frequency (IF) band signal of the cos channel (I channel) and the intermediate frequency (IF) of the sin channel (Q channel) obtained through signal processing of the received signal. Obtaining distance-velocity detection results for each target by applying a two-dimensional fast Fourier transform (2D FFT) to the band signal; And applying a constant false alarm rate (CFAR) algorithm to the distance-speed detection result to extract distance-velocity peaks corresponding to each target and phase values of the peaks. A target detection method based on phase information of MIMO radar signals. The method of claim 1, wherein the radar transmission signal is a signal modulated using PSK modulation. The method of claim 1, wherein the plurality of transmitting antennas and the plurality of receiving antennas are antenna arrays arranged in a ULA form. The method of claim 1, wherein in the step of classifying each transmission antenna, when there are two transmission antennas, the preceding sub-phase sequence among the phase sequences of the distance-velocity peaks forming an arithmetic sequence is the first transmission antenna. corresponds to signals transmitted from the second transmit antenna, and a latter phase sequence is determined to correspond to signals transmitted from the second transmit antenna, where each sub-phase sequence has a number of phases equal to the number of receive antennas. A target detection method based on phase information of a MIMO radar signal, characterized in that it is a sequence of. The method of claim 1, wherein in the step of classifying each transmission antenna, if there are N transmission antennas (where N is a natural number of 3 or more), the kth phase sequence of distance-velocity peaks forming an arithmetic sequence (where , k is a natural number from 1 to N) The sub-phase sequence is determined to correspond to signals transmitted from the kth transmitting antenna, where each sub-phase sequence is a sequence of phases with the same number of phases as the number of receiving antennas. A target detection method based on phase information of MIMO radar signals. The phase of the MIMO radar signal according to claim 1, further comprising calculating estimated information about the speed and angle of each target using the received signal divided for each transmit antenna after the step of classifying. Information-based target detection method. The method of claim 7, wherein the angle of each target is estimated by applying fast Fourier transform to the phase sequence for each target. The method of claim 1, wherein the radar transmission signal is a chirp signal whose frequency increases with time. a plurality of transmitting antennas;
a plurality of receiving antennas;
a transmitter configured to generate a radar transmission signal and transmit it wirelessly through the plurality of transmission antennas;
An intermediate frequency (IF) band signal of the cos channel (I channel) using the received signal reflected by the target in front and received through the plurality of receiving antennas, the transmitted signal, and a 90-degree phase-shifted signal of the transmitted signal. A receiver configured to generate intermediate frequency (IF) band signals of the and sin channels (Q channels);
a digital signal processor configured to perform filtering and fast Fourier transform (FFT) processing on the intermediate frequency band signal of the cos channel (I channel) and the intermediate frequency band signal of the sin channel (Q channel); and
Process of detecting distance-velocity peaks and extracting the phase value of each peak using the signal processed by the digital signal processor, arranging the extracted phase values to form an arithmetic sequence, and based on the sequence of phase values arranged as an arithmetic sequence. It is configured to perform processing to determine the correspondence between received signals and each transmitting antenna, classify the received signal by transmitting antenna, and estimate the distance and speed of the target using the received signal classified for each transmitting antenna. A target detection system based on phase information of a MIMO radar signal, comprising a distance/speed estimator. The method of claim 10, wherein the distance/speed estimator applies a constant false alarm rate (CFAR) algorithm to the signal processed by the fast Fourier transform (FFT) in the digital signal processor to determine the distance-speed corresponding to each target. A target detection system based on phase information of a MIMO radar signal, characterized in that it is configured to extract peaks and phase values of the peaks. The method of claim 10, wherein, when there are two transmitting antennas, the preceding sub-phase sequence (former phase sequence) of the phase sequences of the distance-velocity peaks forming an arithmetic sequence is transmitted from the first transmitting antenna. corresponding to the signals, and is configured to determine that a later sub-phase sequence corresponds to signals transmitted from the second transmit antenna, where each sub-phase sequence has a number of phases equal to the number of receive antennas. A target detection system based on phase information of MIMO radar signals, characterized in that the sequence. The method of claim 10, wherein, when there are N transmitting antennas (N is a natural number of 3 or more), the kth phase sequence of distance-velocity peaks forming an arithmetic sequence (where k starts from 1) up to N natural numbers) is configured to determine the sub-phase sequence corresponding to signals transmitted from the kth transmit antenna, where each sub-phase sequence is a sequence of phases with a number equal to the number of receive antennas. Target detection system based on phase information of radar signals. 11. The phase information of the MIMO radar signal according to claim 10, further comprising an angle estimation unit configured to calculate the angle information of each target by applying a predetermined angle estimation algorithm using received signals separated for each transmission antenna. based target detection system. The target detection system according to claim 14, wherein the angle estimation unit is configured to estimate the angle of each target by applying a fast Fourier transform to the phase sequence of each target. The target detection system based on phase information of a MIMO radar signal according to claim 10, wherein the plurality of transmitting antennas and the plurality of receiving antennas are antenna arrays arranged in a ULA form. The target detection system based on phase information of a MIMO radar signal according to claim 10, wherein the radar transmission signal is a chirp signal whose frequency increases with time. A computer-executable program stored in a computer-readable recording medium to perform the target detection method based on phase information of a MIMO radar signal according to any one of claims 1 to 9. A computer-readable recording medium on which a computer program for performing the target detection method based on phase information of a MIMO radar signal according to any one of claims 1 to 9 is recorded.