CN110412558B - Method for resolving speed ambiguity of vehicle-mounted FMCW radar based on TDM MIMO - Google Patents

Method for resolving speed ambiguity of vehicle-mounted FMCW radar based on TDM MIMO Download PDF

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CN110412558B
CN110412558B CN201910593641.5A CN201910593641A CN110412558B CN 110412558 B CN110412558 B CN 110412558B CN 201910593641 A CN201910593641 A CN 201910593641A CN 110412558 B CN110412558 B CN 110412558B
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mimo
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doppler
target
speed
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CN110412558A (en
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彭树生
卞亨通
吴礼
刘钧
肖芸
高辉
盛俊铭
毕业昆
彭立尧
李玉年
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Nanjing University of Science and Technology
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
    • G01S13/50—Systems of measurement based on relative movement of target
    • G01S13/58—Velocity or trajectory determination systems; Sense-of-movement determination systems
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/41—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section
    • G01S7/418—Theoretical aspects

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Abstract

The invention discloses a TDM MIMO-based speed ambiguity resolution method for an on-board FMCW radar, which comprises the following steps: constructing a multi-input multi-output (MIMO) antenna array; the transmitting antennas sequentially transmit FMCW waves until all transmitting antennas finish transmitting, namely an MIMO period; repeating the last step for MIMOnumA period of time; performing two-dimensional FFT on the obtained MIMO difference frequency signal, and calculating the distance and the fuzzy speed of a target; and then Doppler phase compensation and Doppler fuzzy compensation are carried out on the target to obtain the real speed of the target. The Doppler compensation factor is calculated through searching, so that the third-dimensional FFT has no residual phase; before the third-dimensional FFT, Doppler phase compensation and Doppler fuzzy compensation are carried out, the problem that the speed of the FMCW radar is fuzzy due to TDM MIMO is solved, the speed measurement range is improved, the accuracy of angle measurement is guaranteed, the high-angle resolution characteristic brought by MIMO is not lost, and the practicability of the technology in the field of automobile radars is greatly expanded.

Description

Method for resolving speed ambiguity of vehicle-mounted FMCW radar based on TDM MIMO
Technical Field
The invention belongs to the field of automotive radar application, and particularly relates to a method for resolving speed ambiguity of an on-board FMCW radar based on TDM MIMO.
Background
In the active safety driving technology of automobiles, millimeter wave radar gradually becomes an indispensable detection sensor with its all-weather and all-day obvious advantages, and has its own weaknesses, such as lower distance resolution and lower angle resolution, compared with laser radar. However, with the continuous progress of the technology and the increase of the computing power of the processing chip, the millimeter wave radar gradually develops towards the direction of high resolution.
The range resolution of FMCW radars can be achieved by increasing the bandwidth of the modulated signal, while the angular resolution requires an increase in the antenna aperture. The MIMO antenna array is an important technology considered to increase the antenna aperture, the MIMO radar mainly uses time division multiplexing, code division multiplexing and frequency division multiplexing, and the vehicle-mounted millimeter wave radar adopts the MIMO based on the TDM technology in consideration of the realization complexity, the hardware cost and the volume limitation.
Although MIMO based on TDM technology can increase antenna aperture and improve angular resolution, it has its own disadvantages, firstly, TDM itself reduces sampling rate at slow time, so that maximum unambiguous speed is inversely proportional to the number of transmitting antennas. Secondly, because the phase transformation quantity brought by the Doppler frequency of the moving target in different transmitting antenna switching time can be coupled to each receiving channel, the correct synthesis of the receiving antenna aperture is influenced, and therefore the angle measurement of the target outside the maximum unambiguous velocity range is incorrect.
Because the MIMO based on TDM technique has the disadvantage of reducing the maximum unambiguous velocity measurement range, which greatly limits the practicability, the prior method solves the problem, for example, the patent with application number 201810376216.6, named as "a velocity ambiguity resolving method based on MIMO automobile radar", which resolves the velocity ambiguity by calculating M × N third-dimensional FFT results of N receiving antennas of M transmitting antennas and analyzing the main-negative lobe ratio of each third-dimensional FFT result, so that the calculated amount is very large, and especially when the number of transmitting antennas and receiving antennas is too large, the practicability of the method will be greatly reduced.
Disclosure of Invention
The invention aims to provide a method for solving the speed ambiguity of an FMCW radar, which is caused by TDM MIMO, improves the speed measurement range, ensures the accuracy of angle measurement and simultaneously does not lose the high-angle resolution characteristic caused by MIMO.
The technical solution for realizing the purpose of the invention is as follows: a speed ambiguity solving method for a vehicle-mounted FMCW radar based on TDM MIMO comprises the following steps:
step 1, self-defining and constructing a multi-input multi-output MIMO antenna array, which comprises TnumRoot transmitting antenna, RnumRoot receiving antenna, wherein Tnum≥2、Rnum≥2；
Step 2, TnumThe modulation bandwidth of the root transmitting antenna is B and the modulation time is T from left to right in sequencecUntil all transmitting antennas finish transmitting FMCW wave, a MIMO period T is completedMIMO，TMIMO＝TnumTc(ii) a The transmitting antennas are numbered 0, 1num-1；
Step 3, repeating the step 2 to carry out MIMOnumIn each period, the echo signals obtained by the mth MIMO period, the nth transmitting antenna and the kth receiving antenna are recorded as s(m,n,k)Wherein m is more than or equal to 0 and less than MIMOnum,0≤n＜Tnum,0≤k＜Rnum；
Step 4, for each echo signal s(m,n,k)Down-conversion processing is carried out to convert the down-conversion into intermediate frequency signals, and discrete Data are obtained through intermediate frequency filtering, amplification and ADC (analog to digital converter) samplingadcThen num discrete datarangeFFTFFT conversion of points, obtaining the distance dimension FFT result of each echo signal, and recording as allRangeFFT(m,n,k)；
Step 5, aiming at each MIMO period, the allRangeFFT is carried out along the direction of the mth MIMO period(m,n,k)Go on numdopplerFFTPoint FFT conversion is carried out, a two-dimensional FFT result of the mth MIMO period is obtained and is marked as allDopplerrFFT(n,k)；
And 6, combining the two-dimensional FFT results of all the receiving channels aiming at each transmitting channel, and recording the result as hbDoppler(n)Then T is addednumEach hbDoppler(n)Merging, and recording the merged result as aveDoppllerFFT;
step 7, performing constant false alarm on aveDoppllerFFTDetecting, if there are q targets after the constant false alarm detection, each target is in all DoppllerFFT(n,k)In (2) the two-dimensional index number is denoted as Tn,k(rp,dp) P is more than or equal to 0 and less than q, wherein rpFor the index of the p-th object in the distance dimension FFT, dpFor the index of the p-th target in the velocity dimension, according to rpCalculating the fuzzy speed TB (doppler) of the p targetp) While recording the allDopplerrFFT(n,k)In two-dimensional index number Tn,k(rp,dp) I, Q two paths of complex data, denoted as IQ(n,k,p)；
Step 8, performing Doppler phase compensation on the pth target:
IQ(n,k,p)＝IQ(n,k,p)*δn
in the formula, deltanFor the nth transmit channel doppler phase compensation coefficient,
Figure BDA0002116913050000031
step 9, self-defining Doppler fuzzy compensation coefficient as
Figure BDA0002116913050000032
In solving for compensation coefficients
Figure BDA0002116913050000033
And combined with the fuzzy speed TB (doppler) of the p-th targetp) Finding the real speed T (doppler) of the targetp)；
And 10, repeating the steps 8 to 9 until accurate real speeds of all targets are obtained.
Compared with the prior art, the invention has the following remarkable advantages: 1) the method can make the maximum non-fuzzy speed in the original
Figure BDA0002116913050000034
On the basis of (2) to expand TnumIs multiplied by
Figure BDA0002116913050000035
Greatly expand the baseThe speed measurement range of the TDM MIMO vehicle-mounted FMCW radar is further greatly improved, and the practicability of the TDM MIMO vehicle-mounted FMCW radar in the field of automobile radars is further improved; 2) after Doppler phase compensation, residual phase can be eliminated through Doppler fuzzy compensation, and correct target angle information can be further solved; 3) by using search methods to find Doppler ambiguity compensation factors
Figure BDA0002116913050000036
The computational complexity can be reduced, and the practicability of the method is improved; 4) the method can ensure the high-angle resolution characteristic of the TDM MIMO vehicle-mounted FMCW radar while expanding the test range.
The present invention is described in further detail below with reference to the attached drawing figures.
Drawings
FIG. 1 is a flow chart of a method for resolving speed ambiguity of an on-board FMCW radar based on TDM MIMO according to the present invention.
Fig. 2 is a diagram of a MIMO antenna array according to the present invention.
Fig. 3 is a two-dimensional FFT graph of 12 channels in total for 4 transmissions and 4 receptions in embodiment 3 of the present invention, wherein (a) is a two-dimensional FFT result of a first transmit antenna and a first receive antenna; FIG. (b) shows two-dimensional FFT results of a first transmitting antenna and a second receiving antenna; FIG. (c) shows two-dimensional FFT results of the first transmitting antenna and the third receiving antenna; FIG. d shows two-dimensional FFT results of a first transmitting antenna and a fourth receiving antenna; FIG. e shows two-dimensional FFT results for the second transmitting antenna and the first receiving antenna; FIG. f shows two-dimensional FFT results for a second transmitting antenna and a second receiving antenna; FIG. g shows two-dimensional FFT results of a second transmitting antenna and a third receiving antenna; FIG. h shows two-dimensional FFT results of a second transmitting antenna and a fourth receiving antenna; FIG. (i) shows the two-dimensional FFT result of the third transmitting antenna and the first receiving antenna; FIG. j shows two-dimensional FFT results of a third transmitting antenna and a second receiving antenna; the graph (k) shows the two-dimensional FFT result of the third transmitting antenna and the third receiving antenna; fig. (l) shows two-dimensional FFT results for the first transmit antenna and the fourth receive antenna.
Fig. 4 is a two-dimensional FFT graph after channel merging is performed on 12 channels in the embodiment of the present invention.
FIG. 5 is a search in an embodiment of the present invention
Figure BDA0002116913050000041
There are two sets of FFT plots at the residual phase.
FIG. 6 is a search in an embodiment of the present invention
Figure BDA0002116913050000042
There are two sets of FFT plots at the residual phase.
FIG. 7 is a search in an embodiment of the present invention
Figure BDA0002116913050000043
Two sets of FFT plots in the absence of residual phase.
FIG. 8 is a final solution result diagram according to an embodiment of the present invention.
Detailed Description
With reference to fig. 1, the method for resolving speed ambiguity of an onboard FMCW radar based on TDM MIMO comprises the following steps:
step 1, custom-constructing a MIMO antenna array as shown in fig. 2, including TnumRoot transmitting antenna, RnumRoot receiving antenna, wherein Tnum≥2、Rnum≥2。
Step 2, TnumThe modulation bandwidth is B and the modulation time is T from left to right in turn from the transmitting antennacUntil all transmitting antennas finish transmitting FMCW wave, a MIMO period T is completedMIMO，TMIMO＝TnumTc(ii) a The transmitting antennas are numbered 0, 1num-1。
Step 3, repeating the step 2 to carry out MIMOnumIn each period, the echo signals obtained by the mth MIMO period, the nth transmitting antenna and the kth receiving antenna are recorded as s(m,n,k)Wherein m is more than or equal to 0 and less than MIMOnum,0≤n＜Tnum,0≤k＜Rnum。
Step 4, for each echo signal s(m,n,k)Down-conversion processing is carried out to convert the down-conversion signal into an intermediate frequency signal, and the intermediate frequency signal is filtered, amplified and ADC sampledObtain discrete DataadcThen num discrete datarangeFFTFFT conversion of points, obtaining the distance dimension FFT result of each echo signal, and recording as allRangeFFT(m,n,k)。
Step 5, aiming at each MIMO period, the allRangeFFT is carried out along the direction of the mth MIMO period(m,n,k)Go on numdopplerFFTFFT conversion of points to obtain the two-dimensional FFT result of the m-th MIMO period, which is marked as allDopplerrFFT(n,k)。
Step 6, aiming at each MIMO period, aiming at reducing the CFAR operation times and reducing the influence of target detection caused by the difference among channels, and aiming at each MIMO period, performing allRangeFFT along the direction of the mth MIMO period(m,n,k)To perform numdopplerFFTFFT conversion of points to obtain the two-dimensional FFT result of the m-th MIMO period, which is marked as allDopplerrFFT(n,k)。
Step 7, performing constant false alarm rate detection on the aveDoppllerFFT, wherein if q targets exist after the constant false alarm rate detection, each target is in the allDoppllerFFT(n,k)In (2) the two-dimensional index number is denoted as Tn,k(rp,dp) P is more than or equal to 0 and less than q, wherein rpFor the index of the p-th object in the distance dimension FFT, dpFor the index of the p-th target in the velocity dimension, according to rpCalculating the fuzzy speed TB (doppler) of the p-th targetp) While recording the allDopplerrFFT(n,k)In two-dimensional index number Tn,k(rp,dp) I, Q two paths of complex data, denoted as IQ(n,k,p)。
Step 8, due to TnumThe transmitting antenna has time T in two successive echo receptionsMIMOTime delay of, at time T, Doppler frequency generated by moving objectsMIMOThis will cause a phase amount δ, which needs to be compensated for doppler phase before FFT in the third dimension along the transmit path, otherwise it will cause the FFT in the third dimension to be incorrect, resulting in incorrect angle estimation. Doppler phase compensation is carried out on the p target:
IQ(n,k,p)＝IQ(n,k,p)*δn
in the formula, deltanIs the n-thThe Doppler phase compensation coefficient of the transmitting channel,
Figure BDA0002116913050000051
step 9, self-defining Doppler fuzzy compensation coefficient as
Figure BDA0002116913050000052
In solving for compensation coefficients
Figure BDA0002116913050000053
And combined with the fuzzy speed TB (doppler) of the p-th targetp) Determining the true speed T (doppler) of the targetp)。
And 10, repeating the steps 8 to 9 until accurate real speeds of all targets are obtained.
Further, in the MIMO antenna array in step 1, a distance between two adjacent transmitting antennas is d 12 lambda, the distance between two adjacent receiving antennas is d2And λ is the wavelength.
Further, step 9 of solving the compensation coefficient
Figure BDA0002116913050000055
And combined with the fuzzy speed TB (doppler) of the p-th targetp) Determining the true speed T (doppler) of the targetp) The method specifically comprises the following steps:
step 9-1, order IQFp＝IQ(0,k,p)For IQFpGo on numDOAPoint FFT, finding the position of the maximum value and recording as lFDOA；
Step 9-2, order
Figure BDA0002116913050000054
To IQSpGo on numDOAPoint FFT, finding the position of the maximum value and recording as lADOA(ii) a If there is a residual phase, it will result inFDOA≠lADOATherefore, it is possible to judge lFDOAIn lADOAJudging whether the phases are equal or not;
step 9-3, pair
Figure BDA0002116913050000061
From 0 to Tnum-1 search, repeating step 9-2 until lFDOA＝＝lADOAWhen the third-dimension FFT has no residual phase, the final Doppler fuzzy factor is obtained
Figure BDA0002116913050000062
Step 9-4, combining the final Doppler ambiguity factor
Figure BDA0002116913050000063
And fuzzy speed TB (doppler)p) Determining the true speed T (doppler) of the targetp) Comprises the following steps:
Figure BDA0002116913050000064
furthermore, the method of the invention not only can obtain the real speed of the target, but also can obtain the accurate angle and distance information of the target, thereby obtaining the complete target information:
step 11, solving according to step 9
Figure BDA0002116913050000065
Corresponding Doppler fuzzy compensation coefficient
Figure BDA0002116913050000066
Solving accurate angle information of the pth target;
step 12, according to rpCalculating the distance TB (range) of the p-th targetp) The formula used is:
TB(rangep)＝rp×rr
in the formula, rrIs the distance corresponding to the distance from the door;
and (5) repeating the steps 8-9 and the steps 11-12 to obtain accurate angle information and distance information of all targets.
Further preferably, step 11 specifically is:
order to
Figure BDA0002116913050000067
For IQApTo perform numDOAAnd point FFT, namely accurate angle information of the p-th target can be solved by combining the existing angle solving method.
The present invention will be described in further detail with reference to examples.
Examples
In the simulation of the embodiment, the maximum unambiguous velocity measurement range of the radar before the radar is used is +/-16.2338 m/s, the maximum distance measurement range is 75m, the maximum angle measurement is +/-90 degrees, three target point data are generated, the distance of a target 0 is 10m, the speed is 45m/s, and the angle is-15 degrees; the distance of the target 1 is 20m, the speed is-17 m/s, the angle is 20 degrees, the distance of the target 2 is 30m, the speed is 5m/s, the angle is 15 degrees, and the signal-to-noise ratios of the three targets are all 10 dB.
The invention discloses a TDM MIMO-based speed ambiguity resolution method for a vehicle-mounted FMCW radar, which comprises the following processes:
1. the customized construction of a MIMO antenna array is shown in fig. 2, and includes TnumRoot transmitting antenna, RnumRoot receiving antenna, wherein Tnum≥2、RnumNot less than 2. The distance between two adjacent transmitting antennas is d 12 lambda, the distance between two adjacent receiving antennas is d2λ is the wavelength, and λ is 3.95mm, T selected in this examplenum＝3，Rnum＝4。
2、TnumSequentially transmitting modulation bandwidth B from left to right by 3 transmitting antennas, and modulation time Tc＝20e-6s FMCW wave, and completing a MIMO period T until all transmitting antennas finish transmitting FMCW waveMIMO，TMIMO＝TnumTc(ii) a Numbering the transmitting antennas as 0, 1, 2, R in the transmitting ordernumSimultaneously receiving the target generated by different transmitting antennas by 4 receiving antennasAn echo signal.
3. Repeat procedure 2 above for MIMOnumObtaining 3 × 4 paths of antenna receiving data in each MIMO period, and recording echo signals obtained by the mth MIMO period, the nth transmitting antenna and the kth receiving antenna as s(m,n,k)Wherein m is more than or equal to 0 and less than MIMOnum,0≤n＜Tnum,0≤k＜Rnum。
4. For each echo signal s(m,n,k)Down-conversion processing is carried out to convert the down-conversion into intermediate frequency signals, and discrete Data are obtained through intermediate frequency filtering, amplification and ADC (analog to digital converter) samplingadcThen num discrete datarangeFFTFFT conversion of points, obtaining the distance dimension FFT result of each echo signal, and recording as allRangeFFT(m,n,k)As shown in fig. 3.
5. For each MIMO period, an allRangeFFT is paired along the direction of the m-th MIMO period(m,n,k)Go on numdopplerFFTFFT conversion of points to obtain the two-dimensional FFT result of the m-th MIMO period, which is marked as allDopplerrFFT(n,k)。
6. In order to reduce the CFAR operation times and reduce the influence of target detection caused by the difference among channels, aiming at each transmitting channel, the two-dimensional FFT results of all receiving channels are combined and recorded as hbDoppler(n)Then T is addednumEach hbDoppler(n)And merging, and recording the merged result as aveDopplerFFT, as shown in fig. 4.
7. Performing constant false alarm rate detection on ave Doppler FFT, wherein if q targets exist after the constant false alarm rate detection, each target is in all Doppler FFT(n,k)In (2) the two-dimensional index number is denoted as Tn,k(rp,dp) P is more than or equal to 0 and less than q, wherein rpFor the index of the p-th object in the distance dimension FFT, dpFor the index of the p-th target in the velocity dimension, according to rpCalculating the fuzzy speed TB (doppler) of the p-th targetp) While recording the allDopplerrFFT(n,k)In two dimensions index number Tn,k(rp,dp) I, Q two paths of complex data, denoted as IQ(n,k,p)(ii) a In this example, q is 3.
8. Doppler phase compensation is carried out on the p target:
IQ(n,k,p)＝IQ(n,k,p)*δn
in the formula, deltanFor the nth transmit channel doppler phase compensation coefficient,
Figure BDA0002116913050000081
9. the self-defined Doppler fuzzy compensation coefficient is
Figure BDA0002116913050000082
In solving for compensation coefficients
Figure BDA0002116913050000083
And combined with the fuzzy speed TB (doppler) of the p-th targetp) Determining the true speed T (doppler) of the targetp) The method specifically comprises the following steps:
9-1 order IQFp＝IQ(0,k,p)For IQFpGo on numDOAPoint FFT, finding the position of the maximum value and recording as lFDOA；
9-2, order
Figure BDA0002116913050000084
To IQSpGo on numDOAPoint FFT, the position where the maximum value is searched is marked as lADOA；
If it is
Figure BDA0002116913050000085
Incorrect selection will result in residual phase in the second set of FFT, resulting in lFDOA≠lADOAIf, as shown in FIGS. 5 and 6, the
Figure BDA0002116913050000086
If the selection is correct, there is no residual phase in the second FFT result, so that lFDOA＝＝lADOAAs shown in fig. 7;
9-3, pair
Figure BDA0002116913050000087
From 0 to Tnum-1 search is performed, repeating the above 9-2 until lFDOA＝＝lADOAFrom which the final Doppler ambiguity factor is obtained
Figure BDA0002116913050000088
9-4, combining the resulting Doppler ambiguity factor
Figure BDA0002116913050000089
And fuzzy speed TB (doppler)p) Determining the true speed T (doppler) of the targetp) Comprises the following steps:
Figure BDA00021169130500000810
10. solving according to 9 above
Figure BDA00021169130500000811
Corresponding Doppler fuzzy compensation coefficient
Figure BDA00021169130500000812
Solving the accurate angle information of the pth target, specifically:
order to
Figure BDA00021169130500000813
For IQApGo on numDOAAnd point FFT is combined with the existing angle solving method, so that accurate angle information of the p-th target can be solved.
11. According to rpCalculating the distance TB (range) of the p-th targetp) The formula used is:
TB(rangep)＝rp×rr
in the formula, rrIs the corresponding distance from the door.
Repeating the above-mentioned process 8-11, the true speed, accurate angle information and distance information of all targets can be obtained, the measurement result of this embodiment is shown in fig. 8, and it can be seen from the figure that the target information detected by the method of the present invention is consistent with the set target information, and there is only a few errors, so that the method of the present invention can solve the speed ambiguity and has a good effect.
In conclusion, the Doppler compensation factor is searched and calculated, so that the third-dimensional FFT has no residual phase; before the third-dimensional FFT, Doppler phase compensation is carried out, and Doppler fuzzy compensation is also carried out, so that the problem of speed fuzzy of the FMCW radar caused by TDM MIMO is solved, the speed measurement range is improved, the accuracy of angle measurement is guaranteed, the high-angle resolution characteristic brought by MIMO is not lost, and the practicability of the technology in the field of automobile radars is greatly expanded.

Claims (5)

1. A method for resolving speed ambiguity of an on-board FMCW radar based on TDM MIMO is characterized by comprising the following steps:
step 1, self-defining and constructing a multi-input multi-output MIMO antenna array, which comprises TnumRoot transmitting antenna, RnumRoot receiving antenna, wherein Tnum≥2、Rnum≥2；
Step 2, TnumThe modulation bandwidth is B and the modulation time is T from left to right in turn from the transmitting antennacUntil all transmitting antennas finish transmitting FMCW wave, one MIMO period T is finishedMIMO，TMIMO＝TnumTc(ii) a The transmitting antennas are numbered 0, 1num-1；
Step 3, repeating the step 2 to carry out MIMOnumIn each period, the echo signals obtained by the mth MIMO period, the nth transmitting antenna and the kth receiving antenna are recorded as s(m,n,k)Wherein m is more than or equal to 0 and less than MIMOnum,0≤n＜Tnum,0≤k＜Rnum；
Step 4, for each echo signal s(m,n,k)Down-conversion processing is carried out to convert the down-conversion into intermediate frequency signals, and discrete Data are obtained through intermediate frequency filtering, amplification and ADC (analog to digital converter) samplingadcThen num discrete datarangeFFTFFT conversion of points, obtaining the distance dimension FFT result of each echo signal, and recording as allRangeFFT(m,n,k)；
Step 5, aiming at each MIMO period, the allRangeFFT is carried out along the direction of the mth MIMO period(m,n,k)Go on numdopplerFFTFFT conversion of points to obtain the two-dimensional FFT result of the m-th MIMO period, which is marked as allDopplerrFFT(n,k)；
And 6, combining the two-dimensional FFT results of all the receiving channels aiming at each transmitting channel, and recording the result as hbDoppler(n)Then T is addednumEach hbDoppler(n)Merging, and recording the merged result as aveDoppllerFFT;
step 7, performing constant false alarm rate detection on the aveDoppllerFFT, wherein if q targets exist after the constant false alarm rate detection, each target is in the allDoppllerFFT(n,k)In (2) the two-dimensional index number is denoted as Tn,k(rp,dp) P is more than or equal to 0 and less than q, wherein rpFor the index of the p-th object in the distance dimension FFT, dpFor the index of the p-th target in the velocity dimension, according to rpCalculating the fuzzy speed TB (doppler) of the p-th targetp) While recording the allDopplerrFFT(n,k)In two-dimensional index number Tn,k(rp,dp) I, Q two paths of complex data, denoted as IQ(n,k,p)；
Step 8, performing Doppler phase compensation on the pth target:
IQ(n,k,p)＝IQ(n,k,p)*δn
in the formula, deltanFor the nth transmit channel doppler phase compensation coefficient,
Figure FDA0002116913040000021
step 9, self-defining Doppler fuzzy compensation coefficient as
Figure FDA0002116913040000022
In solving for compensation coefficients
Figure FDA0002116913040000023
And combined with the fuzzy speed TB (doppler) of the p-th targetp) Determining the true speed T (doppler) of the targetp)；
And 10, repeating the steps 8 to 9 until accurate real speeds of all targets are obtained.
2. The method for resolving speed ambiguity of FMCW radar in vehicle based on TDM MIMO as claimed in claim 1, wherein the MIMO antenna array of step 1 has two adjacent transmitting antennas spaced apart by a distance d12 lambda, the distance between two adjacent receiving antennas is d2And λ is the wavelength.
3. The TDM MIMO based method for resolving vehicle FMCW radar speed ambiguity based on claim 1, wherein the step 9 of resolving the compensation coefficients
Figure FDA0002116913040000024
And combined with the fuzzy speed TB (doppler) of the p-th targetp) Determining the true speed T (doppler) of the targetp) The method specifically comprises the following steps:
step 9-1, order IQFp＝IQ(0,k,p)For IQFpGo on numDOAPoint FFT, finding the position of the maximum value and recording as lFDOA；
Step 9-2, order
Figure FDA0002116913040000025
To IQSpGo on numDOAPoint FFT, finding the position of the maximum value and recording as lADOA；
Step 9-3, pair
Figure FDA0002116913040000026
From 0 to Tnum-1 performing a search, repeating the stepsStep 9-2, up to lFDOA＝＝lADOAFrom which the final Doppler ambiguity factor is obtained
Figure FDA0002116913040000027
Step 9-4, combining the final Doppler ambiguity factor
Figure FDA0002116913040000028
And fuzzy speed TB (doppler)p) Determining the true speed T (doppler) of the targetp) Comprises the following steps:
Figure FDA0002116913040000031
4. the TDM MIMO-based speed ambiguity resolution on-board FMCW radar of claim 1, further comprising obtaining angle and distance information of the target, and further obtaining complete target information:
step 11, solving according to step 9
Figure FDA0002116913040000032
Corresponding Doppler fuzzy compensation coefficient
Figure FDA0002116913040000033
Solving accurate angle information of the pth target;
step 12, according to rpCalculating the distance TB (range) of the p-th targetp) The formula used is:
TB(rangep)＝rp×rr
in the formula, rrIs the distance corresponding to the distance from the door;
and (6) repeating the steps 8-9 and the steps 11-12 to obtain accurate angle information and distance information of all targets.
5. The TDM MIMO based speed ambiguity resolution method for vehicle FMCW radar according to claim 4, wherein step 11 specifically comprises:
order to
Figure FDA0002116913040000034
For IQApGo on numDOAAnd point FFT, namely accurate angle information of the p-th target can be solved by combining the existing angle solving method.
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