JP7632514B2 - OBJECT DETECTION DEVICE, OBJECT DETECTION METHOD, AND PROGRAM - Google Patents

Description

The present invention relates to an object detection device, an object detection method, and a program.

There are object detection devices that use electromagnetic waves to detect target objects. Among these, those that use radio waves are called radar devices. In general, radar devices detect the presence of a target by emitting radio waves into space and receiving the signal reflected by the target object, and observe its position, movement, etc. The emitted radio waves are rectangular waves (pulses) with a certain width, and will be referred to as radio wave pulses below.

In a radar device that irradiates radio wave pulses, there are mainly two methods for estimating the speed of a target.
(1) Method using Doppler frequency (first method)
(2) Method using the distance measurement difference between up-chirp and down-chirp (second method)

The first method derives the speed of a target object from the Doppler frequency and the known transmission frequency and speed of light. The Doppler frequency is calculated by emitting multiple radio wave pulses, receiving multiple radio wave pulses reflected by the target object, and performing a Fourier transform on the received multiple radio wave pulses in the hit direction for each range bin. The advantage of the first method is its high accuracy. However, its disadvantage is that if the pulse repetition interval (PRI), which is the time interval between the emission of radio wave pulses, is long, ambiguity occurs in the amount of phase rotation between each hit, which in turn causes ambiguity in the estimated speed.

The second method obtains the speed of a target object using the difference between the distance measurement result obtained using an up-chirp radio pulse that is linearly frequency-modulated in the direction of increasing frequency and the distance measurement result obtained using a down-chirp radio pulse that is linearly frequency-modulated in the direction of decreasing frequency. When measuring distance using linear frequency modulation, the distance measurement result deviates from the true value due to the influence of Doppler shift. It is known that the direction of deviation is opposite for up-chirp and down-chirp. Using this, the difference between the distance measurement result of up-chirp and the distance measurement result of down-chirp is converted to the speed of the target. The advantage of the second method is that there is no ambiguity in the estimated speed. However, in the second method, it is necessary to match the distance measurement results of up-chirp and down-chirp for each target object before calculating the difference in the distance measurement results. However, when there are multiple target objects in close proximity, the matching is easily mistaken, and as a result, the disadvantage is that the accuracy of the distance measurement and the speed estimation is easily deteriorated.

Taking these factors into consideration, a speed estimation method that is free of ambiguity and has high accuracy is disclosed, for example, in Patent Document 1.

JP 2005-83867 A

The following analysis is provided by the present invention.

The method disclosed in Patent Document 1 combines the first and second methods described above, improving only the disadvantages of each while retaining the advantages of each. However, this method requires the target object to be detected twice, with each up chirp and down chirp. Compared to a method that detects a target only once with N hits, under the same observation time conditions, each up chirp and down chirp requires N/2 hits to detect the target, resulting in a deterioration of detection capability. On the other hand, under the same detection capability conditions, each up chirp and down chirp requires N hits to detect the target, requiring twice the observation time and consuming twice the radar's time resources.

Thus, in object detection devices such as radar devices that use radio wave pulses (pulse radar devices), there is a demand for highly accurate distance estimation (ranging) and speed estimation without ambiguity in distance and speed, without degrading detection capabilities or increasing the radar's resource consumption.

The present invention has been made in consideration of the above circumstances, and aims to provide a technology that enables efficient and highly accurate distance and speed estimation in an object detection device.

According to a first aspect of the present invention,
a transceiver unit that transmits a plurality of digitally code modulated transmission pulse signals to a target object moving relative to the device, receives the plurality of transmission pulse signals reflected by the target object, and generates a reception signal;
a calculation unit that performs signal processing on the received signal and detects the target object,
The calculation unit is
a pulse Doppler filter bank processing unit that performs Doppler shift correction to correct a Doppler shift of the received signal using each of a plurality of velocity candidates of the target object, and performs range walk correction and pulse compression on the received signal after the Doppler shift correction to generate a first output signal for each of the velocity candidates;
an array shape modification processor that modifies the first output signal so as to place velocity ambiguities in adjacent bins in a folding direction, and generates a second output signal;
a target detection processing unit for detecting the target object from the second output signal,
the transmitting/receiving unit performs the digital code modulation on the plurality of transmission pulse signals using a code sequence that differs for each transmission pulse;
The modulation method of the digital code modulation uses at least one of frequency modulation and phase modulation,
the pulse Doppler filter bank processing unit performs the Doppler shift correction , the range walk correction, and the pulse compression processing in parallel for each hit of the received signal, and then adds up the processing results of each hit to generate the first output signal ;
the Doppler shift correction is a correction for correcting a Doppler shift of the received signal by calculating a Doppler shift correction term for canceling an offset of a target Doppler frequency in the received signal,
The range walk correction is a correction that calculates a range walk correction term that cancels the movement of the target object between PRIs (Pulse Repetition Intervals) and corrects the range walk of the received signal after the Doppler shift correction and the phase change between the PRIs, and an object detection device is provided.

According to a second aspect of the present invention,
1. An object detection method executed by a computer of an object detection device, comprising:
a pulse Doppler filter bank processing step of performing Doppler shift correction for correcting a Doppler shift of a received signal in parallel for each hit of the received signal using each of a plurality of velocity candidates of the target object, performing range walk correction and pulse compression on the received signal after the Doppler shift correction , adding up the processing results of each hit after the Doppler shift correction , the range walk correction, and the pulse compression processing, and generating a first output signal for each of the velocity candidates;
a constellation reshaping step for reshaping the velocity candidates so as to place velocity ambiguities in adjacent bins in a folding direction, thereby generating a second output signal;
a target detection processing step of detecting the target object from the second output signal,
The target object moves relative to the object detection device,
The received signal is generated from a signal reflected by a target object of a plurality of transmission pulse signals transmitted to the target object,
the plurality of transmission pulse signals are digitally code-modulated using a different code sequence for each transmission pulse;
The modulation method of the digital code modulation uses at least one of frequency modulation and phase modulation ,
the Doppler shift correction is a correction for correcting a Doppler shift of the received signal by calculating a Doppler shift correction term for canceling an offset of a target Doppler frequency in the received signal,
The range walk correction is a correction that calculates a range walk correction term that cancels the movement of the target object between PRIs (Pulse Repetition Intervals) and corrects the range walk of the received signal after the Doppler shift correction and the phase change between the PRIs .

According to a third aspect of the present invention,
The object detection device's computer
a pulse Doppler filter bank processing procedure for performing Doppler shift correction for correcting a Doppler shift of a received signal in parallel for each hit of the received signal using each of a plurality of velocity candidates of the target object, performing range walk correction and pulse compression on the received signal after the Doppler shift correction , adding up the processing results of each hit after the Doppler shift correction , the range walk correction, and the pulse compression processing, and generating a first output signal for each of the velocity candidates;
a constellation shape modification step for modifying the velocity candidates to place velocity ambiguities in adjacent bins in a folding direction and generating a second output signal;
a target detection processing procedure for detecting the target object from the second output signal,
The target object moves relative to the object detection device,
The received signal is generated from a signal reflected by a target object of a plurality of transmission pulse signals transmitted to the target object,
the plurality of transmission pulse signals are digitally code-modulated using a different code sequence for each transmission pulse;
The modulation method of the digital code modulation uses at least one of frequency modulation and phase modulation ,
the Doppler shift correction is a correction for correcting a Doppler shift of the received signal by calculating a Doppler shift correction term for canceling an offset of a target Doppler frequency in the received signal,
The range walk correction is performed by calculating a range walk correction term that cancels the movement of the target object between PRIs (Pulse Repetition Intervals) and correcting the range walk of the received signal after the Doppler shift correction and the phase change between the PRIs .

These programs can be recorded on a computer-readable storage medium. The storage medium can be a non-transient medium such as a semiconductor memory, a hard disk, a magnetic recording medium, or an optical recording medium. The present invention can also be embodied as a computer program product.

According to the present invention, an object detection device can efficiently estimate distance and speed with high accuracy.

1A is a block diagram showing an example of the configuration of a radar device according to one embodiment of the present invention, FIG. 1B is a functional block diagram showing an example of the functional configuration of a calculation unit according to one embodiment of the present invention, and FIG. 1C is a hardware configuration diagram showing an example of the hardware configuration of a calculation unit according to one embodiment of the present invention. 2 is a block diagram showing an example of the configuration of a pulse Doppler filter bank processing unit according to an embodiment of the present invention; FIG. 1 is a block diagram showing an example of a configuration of a pulse Doppler filter module according to an embodiment of the present invention; FIG. 1A is an explanatory diagram for explaining an example of an image of a received signal after pulse Doppler filter bank processing in one embodiment of the present invention, and FIG. 1B is an explanatory diagram for explaining an example of an image of a signal after array shape changing processing in one embodiment of the present invention. FIG. 2 is a block diagram showing an example of a configuration of a target detection processing unit according to an embodiment of the present invention. 4 is a flowchart of an object detection process according to an embodiment of the present invention.

Below, an overview of one embodiment of the present invention (hereinafter referred to as this embodiment) will be described with reference to the drawings. Note that the reference symbols in the drawings are given for convenience as an example to aid understanding, and are not intended to limit the present invention to the illustrated form. Furthermore, the connection lines between blocks in the drawings and the like referred to in the following description include both bidirectional and unidirectional lines. Unidirectional arrows are used to diagrammatically indicate the flow of the main signal (data), and do not exclude bidirectionality.

In addition, although there are ports and interfaces at the input/output connection points of each block in the diagram, they are not shown. In the following explanation, "A and/or B" is used to mean A or B, or A and B.

One embodiment of the present invention will be described below with reference to the drawings.

The object detection device of this embodiment transmits multiple transmission signals in a predetermined direction and receives multiple reflected signals that are the result of the multiple transmission signals being reflected by a target object. Each transmission signal is a pulse signal obtained by cutting a carrier wave on which a baseband signal is superimposed, using a rectangular function of a predetermined width.

In the following, this embodiment will be described using an example in which the carrier wave is a radio wave, i.e., the object detection device is a radar device.

Figure 1 is a functional block diagram of a radar device 100 according to this embodiment. The radar device 100 detects the presence of a target object 900 using radio waves and measures the distance and estimates the speed. As shown in this figure, the radar device 100 includes a transmitting/receiving device (transmitting/receiving unit) 200 that transmits and receives radio waves, and a calculation unit 300 that estimates the position and speed of the target object 900 based on the received signal generated by the transmitting/receiving unit.

The transmitting/receiving unit 200 includes a transmitting device (transmitting unit) 210 that transmits radio waves, and a receiving device (receiving unit) 220 that generates a received signal from the radio waves reflected from the target object 900.

The transmitter 210 transmits a plurality of digitally code modulated radio wave pulses (transmission pulse signals) as transmission signals in a predetermined direction. In this embodiment, the transmitter 210 transmits the transmission pulse signal to a target object 900 that is moving relative to the radar device 100, which is the device itself.

・・・（１）
ただし、ｔ：送信パルスが圧縮される時間位置
ｔ_０：送信パルスが反射されたときの目標物体の距離相当時間
Ｖ：目標物体のレーダ方向速度
ｆ_ｃ：レーダの送信周波数（搬送波の周波数）
ＰＷ：送信パルスのパルス幅
τ：送信パルスの圧縮後パルス幅
ｃ：光速
なお、Ｖは、目標物体９００がレーダ装置１００から遠ざかる方向を＋としている。式（１）の第１項と第２項との間の演算子の±については、アップチャープの場合は＋となり、ダウンチャープの場合は－となる。 In general radar devices, linear frequency modulation such as chirp is often used for modulation. In this case, a technique called pulse compression is used to improve the S/N ratio and distance resolution by shortening the echo duration. The time position compressed by pulse compression is expressed by the following equation (1). In this equation, the second term on the right side represents the distance measurement error caused by the Doppler shift.

...(1)
where t: time position at which the transmission pulse is compressed t ₀ : time equivalent to the distance of the target object when the transmission pulse is reflected V: radar direction velocity of the target object f _c : radar transmission frequency (carrier frequency)
PW: pulse width of the transmission pulse τ: compressed pulse width of the transmission pulse c: speed of light Note that V is set to + in the direction in which the target object 900 moves away from the radar device 100. The ± operator between the first and second terms in equation (1) is + in the case of an up-chirp and - in the case of a down-chirp.

When measuring distance using a linearly frequency modulated transmission pulse signal, as described above, distance measurement errors due to Doppler shift may occur. Therefore, in this embodiment, a digital code modulation waveform is used, which is one of the waveforms known not to cause distance measurement errors due to Doppler shift.

The code sequence used for digital code modulation is a random code such as a Barker code or an M sequence to avoid ambiguity in the range direction. A different code sequence may be used for each transmission pulse to reduce range side lobes. The modulation method used is frequency modulation, phase modulation, or a combination thereof.

The receiver 220 receives the reflected signal (reflected pulse) from the target object 900, demodulates it, and generates a received signal. In demodulation, for example, a bandpass filter or the like is used to convert the frequency while removing unnecessary frequency components, and a baseband signal is extracted. The extracted baseband signal is then used as the received signal (received pulse).

[Calculation section]
The calculation unit 300 performs signal processing on the received signal to detect the target object 900. To this end, the calculation unit 300 includes a pulse Doppler filter bank processing unit 310, an array shape modification processing unit 320, and a target detection processing unit 330, as shown in FIG.

[Pulse Doppler filter bank processing unit]
The pulse Doppler filter bank processing unit 310 assumes a plurality of velocities of the target object 900 and corrects the Doppler shift of the received signal using each of the velocities, and then performs pulse compression processing on the corrected received signal.

As described above, in this embodiment, digital code modulation is applied to the carrier wave. With digital code modulation, as described above, no ranging error due to Doppler shift occurs. On the other hand, the digital code modulation waveform obtained by digital code modulation has a large Doppler loss. Doppler loss is the loss of pulse compression due to Doppler shift. With a digital code modulation waveform, even a small amount of Doppler shift causes a significant drop in peak level after pulse compression.

In this embodiment, this property is used in reverse. That is, in the pulse Doppler filter bank processing unit 310 of this embodiment, multiple velocity candidates are prepared as the velocity of the target object 900. Then, Doppler shift correction is performed using each velocity candidate. Since the correction target is a received signal obtained by digital code modulation, a large pulse compression gain can be obtained without a decrease in peak level only when Doppler shift correction is performed at a velocity close to the true velocity. As a result, a highly accurate velocity estimate can be obtained.

The pulse Doppler filter bank processing unit 310 performs multi-stage pulse Doppler filter processing on all hit received signals (all received pulses) using multiple assumed velocity candidates. Hereinafter, the number of hits is N (N is an integer equal to or greater than 1), and the number of assumed velocity candidates is L (L is an integer equal to or greater than 1).

As shown in FIG. 2, the pulse Doppler filter processing at each stage is performed by pulse Doppler filter modules 310m, the number of which is L, the number of assumed velocity candidates. Each pulse Doppler filter module 310m receives N received signals and one velocity as input, and performs pulse Doppler filter bank processing. Therefore, the PDF-processed received signal, which is the output of the pulse Doppler filter bank processing unit 310, is obtained for each of the number of pulse Doppler filter modules 310m, i.e., L velocity candidates.

The assumed speed candidates are determined in advance and stored in the calculation unit 300. At this time, the smaller the interval between the assumed speed candidates, the more accurate the speed estimation. However, this increases the number of pulse Doppler filter modules 310m to be prepared, and the scale of calculation increases. In addition, the maximum and minimum values of the assumed speed candidates are determined in advance from the maximum and minimum values of the assumed speed of the target object 900.

Here, the pulse Doppler filter module 310m will be described in detail. Each pulse Doppler filter module 310m receives the received signals of all hits (1 to N hits) and one velocity as input, performs Doppler shift correction, range walk correction, pulse compression (matched filter), and coherent integration, and outputs a signal with an improved signal-to-noise ratio. An example of a block diagram of the configuration of the pulse Doppler filter module 310m of this embodiment is shown in Figure 3.

As shown in this figure, the pulse Doppler filter module 310m of this embodiment includes a Doppler shift correction unit 311, a range fast Fourier transform (FFT) unit 312, a range walk correction unit 313, a matched filter unit 314, a coherent integration unit 315, and a range inverse fast Fourier transform (IFFT) unit 316. In addition, the Doppler shift correction unit 311, the range fast Fourier transform (FFT) unit 312, the range walk correction unit 313, and the matched filter unit 314 are prepared for each received signal, that is, for the number of hits (N) of the received signal.

The Doppler shift correction unit 311 calculates the Doppler shift correction term and corrects the Doppler shift of the received signal.

The Doppler shift correction term is a term that cancels the offset of the target Doppler frequency in the received signal. The Doppler shift correction term is a function of the fast time. Note that the fast time is the elapsed time from the transmission time of the transmission pulse of each hit. In other words, it is the distance to the target object 900 converted into time. This Doppler shift correction term does not depend on the slow time. Therefore, the same value can be used in the slow time direction. Note that the slow time is the elapsed time from the transmission time of the transmission pulse of the first hit to the transmission time of the transmission pulse of each hit.

…（２）
ただし、j：虚数
ｆｄ_ｇｌｂ：グローバルドップラ周波数
ｔ_ｆ：ファストタイム
ここで、グローバルドップラ周波数ｆｄ_ｇｌｂは、以下の式（３）で表される。

…（３）
ただし、ｖ：当該パルスドップラフィルタモジュール３１０ｍに入力された目標物体９００の速度候補（速度１～速度Ｌのいずれか） The Doppler shift correction term Dsct is expressed by the following equation (2).

…(2)
where j is an imaginary number
fd _glb : Global Doppler frequency
t _f : fast time Here, the global Doppler frequency fd _glb is expressed by the following equation (3).

…(3)
where v is a candidate velocity of the target object 900 input to the pulse Doppler filter module 310m (any of velocities 1 to L)

The Doppler shift correction unit 311 corrects the Doppler shift by multiplying the received signal, which is a function of the fast time _tf , by the Doppler shift correction term expressed by the above equation (2).

The range walk correction unit 313 calculates a range walk correction term and corrects the range walk and phase change between hits in the received signal after Doppler shift correction. A range walk occurs when the target object 900 moves across multiple range bins during pulse integration processing when the moving speed of the target object 900 is high.

…（４）
ただし、ｆ_ｆ：ファストタイム周波数
ｔ_ｓ＝０、ＰＲＩ、２ＰＲＩ、・・・、（Ｎ－１）ＰＲＩ；スロータイム The range walk correction term Rwct is a term that cancels the movement of the target object 900 during a PRI (Pulse Repetition Interval), and is expressed by the following equation (4).

…(4)
where f _f is the fast-time frequency, t _s =0, PRI, 2PRI, ..., (N-1)PRI; slow-time

The matched filter unit 314 performs pulse compression (matched filter) processing on the received signal after range walk correction. Pulse compression (matched filter) is processing aimed at maximizing the signal-to-noise ratio and compressing the pulse width. In the frequency domain, the complex conjugate of the baseband waveform of the transmission signal is multiplied by the waveform after range walk correction. Note that although the pulse compression (matched filter) processing in this embodiment is performed by multiplication in the frequency domain, it may also be performed by convolution in the time (distance) domain.

The coherent integration unit 315 performs coherent integration on the processing results of each matched filter unit 314. Coherent integration is a process of simple addition in the slow time direction. In other words, the processing results of the matched filter unit 314 for each hit are added.

The range FFT unit 312 performs an FFT (range FFT) on the signal in the range (distance) direction. This converts the signal into a frequency domain signal. The range IFFT unit 316 performs an IFFT (range inverse FFT) on the signal in the range (distance) direction. This converts the signal into a time domain signal. During processing, the pulse Doppler filter module 310m of this embodiment performs FFT and IFFT on the signal (data) as appropriate depending on the subsequent processing, converting it in the frequency domain and time domain.

By the processing by each section of the pulse Doppler filter bank processing section 310, the received signal after PDF processing is expressed by a function having two arguments, the velocity candidate v (velocity 1 to velocity L) input to the pulse Doppler filter module 310m and the fast time _tf . In other words, the received signal after PDF processing is two-dimensional array data having two dimensions, the velocity candidate direction and the fast time direction.

[Array shape change processing section]
The array shape change processing unit 320 changes the PDF processed received signal expressed as two-dimensional array data into three-dimensional array data. Here, the true Doppler response is extracted by removing the frequency aliasing, i.e., ambiguity, that occurs when the Doppler frequency exceeds the Doppler frequency range (-PRF/2 to PRF/2). The pulse repetition frequency PRF is the reciprocal of the pulse repetition period PRI.

FIG. 4(a) shows an image of the change in velocity candidate direction when the fast time _tf is fixed to a certain value for the PDF processed received signal represented by the two-dimensional array data. As shown in this figure, the PDF processed received signal with a certain fast time _tf has strong ambiguity in the velocity candidate direction. When each velocity candidate v is converted to a global Doppler frequency fd _glb using the above formula (3), the ambiguity interval becomes the pulse repetition frequency PRF. If a peak search is performed on this data to detect the target object 900, the ambiguity will be erroneously detected.

…（５）
ここで、ｆｄ_ｌｃｌ（－ＰＲＦ／２～ＰＲＦ/２）：ローカルドップラ周波数
ｎ_ｗｒｐ：折り返し数(整数)
グローバルドップラ周波数ｆｄ_ｇｌｂをパルス繰り返し周波数ＰＲＦで除算したときの商が折り返し数、余りがローカルドップラ周波数である。 Therefore, the array shape modification processor 320 first converts each velocity candidate v into a global Doppler frequency fd _glb using the above formula (3). Then, the global Doppler frequency fd _glb is decomposed into a local Doppler frequency fd _lcl and a number of folds n _wrp as shown in the following formula (5).

…(5)
Here, fd _lcl (-PRF/2 to PRF/2): local Doppler frequency
_nwrp : number of folds (integer)
The quotient obtained by dividing the global Doppler frequency _{fd_glb} by the pulse repetition frequency PRF is the number of folds, and the remainder is the local Doppler frequency.

Using this result, the array shape change processing unit 320 transforms the PDF processed received signal into three-dimensional array data of local Doppler frequency fd _lcl , number of folds n _wrp , and fast time t _f , and outputs the transformed data to the target detection processing unit 330 as the array processed received signal (second output signal).

By decomposing the velocity candidate direction into the local Doppler frequency direction and the foldback direction, the ambiguity of the PRF interval of the velocity candidate direction is placed in adjacent bins in the foldback direction, as shown in Figure 4 (b). In other words, the bins of the velocity ambiguity that arise when the PRI is long are integrated as part of the main lobe. This makes it possible to avoid erroneous detection of ambiguity in the downstream target detection processing unit 330.

[Target detection processing section]
The target detection processing unit 330 detects the target object 900 from the array processed received signal. In this embodiment, the array processed received signal is subjected to predetermined signal processing such as a peak search to identify range bins equal to or greater than a threshold, and the distance to the target object 900 is calculated using the fast time of the range bin. The speed of the target object 900 is also calculated using the local Doppler frequency and number of folds of the range bin.

An example of a block diagram of the configuration of the target detection processing unit 330 is shown in FIG. 5. As shown in this figure, the target detection processing unit 330 includes a power conversion unit 331, a 3D peak search unit 332, a threshold processing unit 333, and a plot extraction unit 334.

…（６） The power conversion unit 331 converts the in-phase component (I; In Phase) and the quadrature component (Q; Quadrature Phase) of the post-arrangement processing received signal into power P by combining them according to the following equation (6).

…(6)

The 3D peak search unit 332 performs a peak search using a maximum value filter for each dimension of the array processed received signal, which is three-dimensional array data. The maximum value filter is a filter that sets the number of correlation range bins as a parameter in advance and outputs the maximum value in the range of the number of correlation range bins before and after a range bin of interest. For the data to be subjected to the peak search, the data after applying the maximum value filter is compared with the data before applying the filter, and peak data is extracted by extracting only range bins whose values match. At this time, the number of correlation range bins is set in consideration of the main lobe shape and side lobe shape so as to avoid erroneous detection.

The threshold processing unit 333 extracts only range bins that exceed a preset threshold (detection threshold: see Figure 4(a)) from the bins extracted by the 3D peak search unit 332.

…（７）

…（８）
ここで、Ｒ_ｅｓｔ：目標物体の距離の推定値
ｖ_ｅｓｔ：目標物体の速度の推定値 The plot extraction unit 334 calculates the estimated distance and velocity of the target object 900 from all the extracted range bins using the following formulas (7) and (8). Then, it outputs these calculated estimated values. Specifically, for the extracted bins, the fast time t _f is converted to distance using formula (7). In addition, the local Doppler frequency fd _lcl and the number of folds n _wrp are converted to velocity using formula (8).

…(7)

…(8)
Here, R _est : Estimated value of the distance of the target object V _est : Estimated value of the velocity of the target object

[Object detection processing]
6 is a flow chart showing the object detection process performed by the calculation unit 300 of the radar device 100 according to the present embodiment. This process is performed every time the calculation unit 300 receives a reception signal from the receiving unit 220.

First, the pulse Doppler filter bank processing unit 310 performs the above-mentioned pulse Doppler filter bank processing (step S1101). Here, first, a plurality of velocity candidates v of the target object 900 are prepared (velocity 1 to velocity L). Using each velocity candidate v, Doppler shift correction and range walk correction are performed on the received signal for each hit. Then, pulse compression (matched filter) processing is performed on the corrected received signal. After that, the received signals for each hit are added. As a result, a PDF-processed received signal expressed as a function with the fast time _tf and the velocity candidate v as parameters is obtained, and output to the array shape change processing unit 320.

Next, the array shape modification processing unit 320 performs an array shape modification process to decompose the arguments of the PDF processed received signal (step S1102). Here, the global Doppler frequency fd _glb for each velocity candidate v is decomposed into the number of folds n _wrp and the local Doppler frequency fd _lcl . The decomposed received signal is output to the target detection processing unit 330 as the array processed received signal.

Then, the target detection processing unit 330 performs object detection processing to identify the distance and speed of the target object 900 (step S1103). As described above, the received signal after array processing is converted to power, a peak search is performed, peak data is extracted, and only bins where the peak data exceeds a threshold are extracted to estimate the distance and speed.

[Hardware configuration]
The calculation unit 300 of the radar device 100 of this embodiment may be implemented, for example, by an integrated circuit (IC) dedicated to each process, an application specific integrated circuit (ASIC), a system on chip (SOC), a field programmable gate array (FPGA), etc. Also, it may be realized by a so-called general-purpose information processing device (computer).

When the calculation unit 300 is realized by a general-purpose information processing device, as shown in FIG. 1(c), it includes, for example, a CPU (Central Processing Unit) 391, a main storage device (memory) 392, an auxiliary storage device 393, an input/output I/F 394, and an expansion I/F 395, which are interconnected by an internal bus.

The CPU 391, for example, loads a program stored in the auxiliary storage device 393 into the main storage device 392 and executes the program to realize the above-mentioned functions and to centrally control the entire calculation unit 300. Note that one or more processors such as an MPU (Micro Processing Unit) may be used instead of the CPU 391.

The main memory 392 is a memory such as a RAM (Random Access Memory). The main memory 392 is a work area used by the CPU 391 when processing programs executed by the calculation unit 300.

The auxiliary storage device 393 is, for example, a read only memory (ROM), a hard disk drive (HDD), or a solid state drive (SSD). The auxiliary storage device 393 stores various programs executed by the calculation unit 300. The auxiliary storage device 393 may include a storage medium such as a flexible disk, a hard disk, an optical disk, a CD-ROM, a CD-R, a magnetic tape, a non-volatile memory card, or a DVD.

The programs stored in the auxiliary storage device 393 can be provided as program products recorded on a non-transitory computer-readable storage medium. The auxiliary storage device 393 can be used to store various programs recorded on the non-transitory computer-readable storage medium for the medium to long term.

The input/output I/F 394 is an interface for inputting and outputting signals and data via wired or wireless communication. The calculation unit 300 of this embodiment receives a received signal from the receiving unit 220 via this input/output I/F 394. In addition, the distance and/or speed of the target object 900 may be output to an external device as a calculation result.

The expansion I/F 395 is an interface for connecting a display device, an input device, and the like. The display device is, for example, an LCD monitor. The input device is, for example, a device that accepts user operations such as a keyboard or a mouse. In this embodiment, for example, multiple speed candidates may be accepted via the input device. The multiple speed candidates may be stored in advance in the auxiliary storage device 393.

Each of the above-mentioned functions of the calculation unit 300 in this embodiment is realized by the CPU 391 loading a program stored in the auxiliary storage device 393 into the main storage device 392 and executing the program.

In addition, data used by the calculation unit 300 for processing may be stored in advance in the auxiliary storage device 393. In addition, data generated during processing is stored in the main storage device 392 or the auxiliary storage device 393.

The hardware configuration of the calculation unit 300 is not limited to this. It may also include hardware not shown.

In addition, the program that realizes each of the above functions of the calculation unit 300 of this embodiment can be recorded on a computer-readable storage medium. The storage medium can be a non-transient medium such as a semiconductor memory, a hard disk, a magnetic recording medium, or an optical recording medium. The present invention can also be embodied as a computer program product.

As described above, the radar device 100 of this embodiment uses digital code modulation for the transmission signal (radio wave pulse). This prevents distance ambiguity caused by Doppler shift. In other words, there is no distance measurement error, and accurate distance measurement can be achieved.

Furthermore, with digital code modulation, the pulse compression loss due to the Doppler shift is large. In this embodiment, the pulse Doppler filter bank processing unit 310 assumes multiple velocity candidates v for the target object 900 and corrects the Doppler shift due to each velocity candidate v. When correcting with a velocity candidate v close to the true velocity, the Doppler shift is almost completely corrected, so there is almost no loss due to pulse compression. As a result, a high signal value is obtained. On the other hand, with a velocity candidate v that differs from the true velocity, the Doppler shift cannot be completely corrected, resulting in a large pulse compression loss. As a result, the obtained signal value is small.

In addition, the pulse repetition period PRI is generally set to be greater than the time it takes for radio waves to travel back and forth to the maximum detection distance assumed by the radar. According to the radar device 100 of this embodiment, the array shape change process is used to integrate the velocity ambiguity bins as part of the main lobe. This makes it possible to avoid the velocity ambiguity that typically occurs when the PRI is long, i.e., when detecting a distant target object.

Furthermore, according to the radar device of this embodiment, the above is achieved by detecting the target object 900 once. Therefore, there is no need for multiple processes, and detection can be achieved efficiently with high accuracy. In other words, there is no degradation of detection capability or increase in resource consumption of the radar device 100.

Therefore, this embodiment allows for efficient and highly accurate distance and speed estimation.

<Modification 1>
In the above embodiment, an array shape change process is performed on the PDF processed received signal, signal processing is performed on the resulting array processed received signal, range bins that satisfy specified conditions are extracted, and the distance and speed of the target object 900 are estimated, but the speed estimation is not limited to this.

For example, the speed candidate that has the highest signal value among the PDF processed received signals of each speed candidate may be set as the speed of the target object 900. In this case, the array shape change process does not need to be performed.

<Modification 2>
In the above embodiment, the radar device 100 in which the carrier wave is a radio wave has been described as an example, but the carrier wave is not limited to a radio wave. For example, the carrier wave may be a light wave. When the carrier wave is a light wave, the object detection device is called a LADAR (Laser Detection and Ranging) device.

In the flowchart used in the above explanation, multiple steps (processes) are described in order, but the order in which each step is performed is not limited to the order described. For example, the order of the steps shown in the figure can be changed to the extent that does not interfere with the content, such as performing each process in parallel.

The programs stored in the auxiliary storage device 393 can also be provided as program products recorded on a non-transitory computer-readable storage medium. These can be used to store various programs recorded on a non-transitory computer-readable storage medium for the medium to long term.

Although each embodiment of the present invention has been described above, the present invention is not limited to the above-mentioned embodiments, and further modifications, substitutions, and adjustments can be made without departing from the basic technical concept of the present invention. For example, the network configurations and the configurations of each element shown in each drawing are examples to aid in understanding the present invention, and the present invention is not limited to the configurations shown in these drawings.

Finally, preferred embodiments of the present invention will be summarized.
(Appendix 1)
a transceiver unit that transmits a plurality of digitally code modulated transmission pulse signals to a target object moving relative to the device, receives the plurality of transmission pulse signals reflected by the target object, and generates a reception signal;
a calculation unit that performs signal processing on the received signal and detects the target object,
The calculation unit is
a pulse Doppler filter bank processing unit that performs Doppler shift correction to correct a Doppler shift of the received signal using each of a plurality of velocity candidates of the target object, performs pulse compression on the received signal after the Doppler shift correction, and generates a first output signal for each of the velocity candidates;
an array shape modification processor that modifies the first output signal so as to place velocity ambiguities in adjacent bins in a folding direction, and generates a second output signal;
a target detection processing unit that detects the target object from the second output signal.
(Appendix 2)
In the object detection device according to claim 1,
It is desirable that the pulse Doppler filter bank processing unit performs the Doppler shift correction and the pulse compression for each hit of the received signal, and then performs integration to generate the first output signal.
(Appendix 3)
In the object detection device according to claim 1 or 2,
The array shape change processing unit includes:
It is preferable to modify the first output signal by decomposing a global Doppler frequency due to each of the velocity candidates into a quotient, which is a fold, and a local Doppler frequency, which is a remainder, when the global Doppler frequency due to each of the velocity candidates is divided by a pulse repetition frequency (PRF).
(Appendix 4)
In the object detection device according to claim 3,
It is preferable that the target detection processing unit calculates the velocity of the target object from the dimensions of the local Doppler frequency and the repetition rate of the second output signal having a signal value equal to or greater than a predetermined threshold value.
(Appendix 5)
In the object detection device according to any one of Supplementary Note 1 to 4,
the first output signal and the second output signal are signals having a dimension in a fast time direction which is an elapsed time from a time when a transmission signal corresponding to each transmission pulse signal was transmitted,
It is desirable that the target detection processing unit calculates the distance to the target object from a signal in the fast time direction dimension of the second output signal having a signal value equal to or greater than a predetermined threshold value.
(Appendix 6)
In the object detection device according to any one of Supplementary Note 1 to 5,
The carrier wave on which the transmission pulse signal is superimposed is preferably an electric wave.
(Appendix 7)
1. An object detection method executed by a computer of an object detection device, comprising:
a pulse Doppler filter bank processing step of performing Doppler shift correction for correcting a Doppler shift of a received signal using each of a plurality of velocity candidates of the target object, performing pulse compression on the received signal after the Doppler shift correction, and generating a first output signal for each of the velocity candidates;
a constellation reshaping step for reshaping the velocity candidates so as to place velocity ambiguities in adjacent bins in a folding direction, thereby generating a second output signal;
a target detection processing step of detecting the target object from the second output signal,
The target object moves relative to the object detection device,
The object detection method, wherein the received signal is generated from a signal reflected by the target object after a plurality of digitally code modulated transmission pulse signals are transmitted to the target object.
(Appendix 8)
The object detection device's computer
a pulse Doppler filter bank processing procedure for performing a Doppler shift correction for correcting a Doppler shift of a received signal generated from a signal reflected by a target object of a plurality of digitally code-modulated transmission pulse signals transmitted to the target object using each of a plurality of velocity candidates of the target object moving relative to the object detection device, performing pulse compression on the received signal after the Doppler shift correction, and generating a first output signal for each of the velocity candidates;
a constellation shape modification step for modifying the velocity candidates to place velocity ambiguities in adjacent bins in a folding direction and generating a second output signal;
a target detection processing procedure for detecting the target object from the second output signal;
In addition, each of the forms of Supplementary Notes 7-8 can be expanded into the forms of Supplementary Notes 2-6, similar to Supplementary Note 1.

The disclosures of the above patent documents and the like are incorporated herein by reference. Within the framework of the entire disclosure of the present invention (including the scope of the claims), and further based on the basic technical ideas, modifications and adjustments of the embodiments and variants are possible. Furthermore, within the framework of the disclosure of the present invention, various combinations and selections of the various disclosed elements (including each element of each claim, each element of each embodiment or variant, each element of each drawing, etc.) are possible. In other words, the present invention naturally includes various modifications and corrections that a person skilled in the art would be able to make in accordance with the entire disclosure, including the scope of the claims, and the technical ideas. In particular, with regard to the numerical ranges described in this document, any numerical value or subrange included within the range should be interpreted as being specifically described, even if not otherwise specified.

100: radar device,
200: transmitting/receiving unit, 210: transmitting unit, 220: receiving unit,
300: calculation unit,
310: Pulse Doppler filter bank processing unit, 310m: Pulse Doppler filter module, 311: Doppler shift correction unit, 312: Range FFT unit, 313: Range walk correction unit, 314: Matched filter unit, 315: Coherent integration unit, 316: Range IFFT unit,
320: array shape change processing unit,
330: target detection processing unit, 331: power conversion unit, 332: 3D peak search unit, 333: threshold processing unit, 334: plot extraction unit,
391: CPU, 392: main storage device, 393: auxiliary storage device, 394: input/output I/F, 395: expansion I/F,
900: target object,
Dsct: Doppler shift correction term, PRI: pulse repetition period, Rwct: range walk correction term, fd _glb : global Doppler frequency, fd _lcl : local Doppler frequency, n _wrp : number of folds, t _f : fast time

Claims (7)

a transceiver unit that transmits a plurality of digitally code modulated transmission pulse signals to a target object moving relative to the device, receives the plurality of transmission pulse signals reflected by the target object, and generates a reception signal;
a calculation unit that performs signal processing on the received signal and detects the target object,
The calculation unit is
a pulse Doppler filter bank processing unit that performs Doppler shift correction to correct a Doppler shift of the received signal using each of a plurality of velocity candidates of the target object, and performs range walk correction and pulse compression on the received signal after the Doppler shift correction to generate a first output signal for each of the velocity candidates;
an array shape modification processor that modifies the first output signal so as to place velocity ambiguities in adjacent bins in a folding direction, and generates a second output signal;
a target detection processing unit for detecting the target object from the second output signal,
the transmitting/receiving unit performs the digital code modulation on the plurality of transmission pulse signals using a code sequence that differs for each transmission pulse;
The modulation method of the digital code modulation uses at least one of frequency modulation and phase modulation,
the pulse Doppler filter bank processing unit performs the Doppler shift correction , the range walk correction, and the pulse compression processing in parallel for each hit of the received signal, and then adds up the processing results of each hit to generate the first output signal ;
the Doppler shift correction is a correction for correcting a Doppler shift of the received signal by calculating a Doppler shift correction term for canceling an offset of a target Doppler frequency in the received signal,
The range walk correction is a correction that calculates a range walk correction term that cancels movement of the target object between PRIs (Pulse Repetition Intervals) and corrects the range walk of the received signal after the Doppler shift correction and a phase change between the PRIs . 2. The object detection device according to claim 1,
The array shape change processing unit includes:
An object detection device that transforms the first output signal by decomposing a global Doppler frequency due to each of the velocity candidates into a number of folds, which is a quotient when the global Doppler frequency is divided by a pulse repetition frequency (PRF), and a local Doppler frequency, which is a remainder. 3. The object detection device according to claim 2,
The object detection device, wherein the target detection processing unit calculates a velocity of the target object from the local Doppler frequency and the foldback direction dimension of the second output signal having a signal value equal to or greater than a predetermined threshold. 2. The object detection device according to claim 1,
the first output signal and the second output signal are signals having a dimension in a fast time direction which is an elapsed time from a time when a transmission signal corresponding to each transmission pulse signal was transmitted,
The object detection device, wherein the target detection processing unit calculates the distance to the target object from a signal in the fast time direction dimension of the second output signal having a signal value equal to or greater than a predetermined threshold. 2. The object detection device according to claim 1,
An object detection device in which the carrier wave on which the transmission pulse signal is superimposed is an electric wave. 1. An object detection method executed by a computer of an object detection device, comprising:
a pulse Doppler filter bank processing step of performing Doppler shift correction for correcting a Doppler shift of a received signal in parallel for each hit of the received signal using each of a plurality of velocity candidates of the target object, performing range walk correction and pulse compression on the received signal after the Doppler shift correction , adding up the processing results of each hit after the Doppler shift correction , the range walk correction, and the pulse compression processing, and generating a first output signal for each of the velocity candidates;
a constellation reshaping step for reshaping the velocity candidates so as to place velocity ambiguities in adjacent bins in a folding direction, thereby generating a second output signal;
a target detection processing step of detecting the target object from the second output signal,
The target object moves relative to the object detection device,
The received signal is generated from a signal reflected by a target object of a plurality of transmission pulse signals transmitted to the target object,
the plurality of transmission pulse signals are digitally code-modulated using a different code sequence for each transmission pulse;
The modulation method of the digital code modulation uses at least one of frequency modulation and phase modulation ,
the Doppler shift correction is a correction for correcting a Doppler shift of the received signal by calculating a Doppler shift correction term for canceling an offset of a target Doppler frequency in the received signal,
The object detection method, wherein the range walk correction is a correction for calculating a range walk correction term that cancels movement of the target object between PRIs (Pulse Repetition Intervals) and correcting the range walk of the received signal after the Doppler shift correction and a phase change between the PRIs . The object detection device's computer
a pulse Doppler filter bank processing procedure for performing Doppler shift correction for correcting a Doppler shift of a received signal in parallel for each hit of the received signal using each of a plurality of velocity candidates of the target object, performing range walk correction and pulse compression on the received signal after the Doppler shift correction , adding up the processing results of each hit after the Doppler shift correction , the range walk correction, and the pulse compression processing, and generating a first output signal for each of the velocity candidates;
a constellation shape modification step for modifying the velocity candidates to place velocity ambiguities in adjacent bins in a folding direction and generating a second output signal;
a target detection processing procedure for detecting the target object from the second output signal,
The target object moves relative to the object detection device,
The received signal is generated from a signal reflected by a target object of a plurality of transmission pulse signals transmitted to the target object,
the plurality of transmission pulse signals are digitally code-modulated using a different code sequence for each transmission pulse;
The modulation method of the digital code modulation uses at least one of frequency modulation and phase modulation ,
the Doppler shift correction is a correction for correcting a Doppler shift of the received signal by calculating a Doppler shift correction term for canceling an offset of a target Doppler frequency in the received signal,
The range walk correction is a correction that calculates a range walk correction term that cancels the movement of the target object between PRIs (Pulse Repetition Intervals) and corrects the range walk of the received signal after the Doppler shift correction and the phase change between the PRIs .

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