CN110208804A - Transmitted waveform design method and target acquisition algorithm suitable for automobile collision avoidance radar - Google Patents
Transmitted waveform design method and target acquisition algorithm suitable for automobile collision avoidance radar Download PDFInfo
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- G—PHYSICS
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- 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
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Abstract
The invention discloses a kind of transmitted waveform design methods and target acquisition algorithm suitable for automobile collision avoidance radar, comprising the following steps: the system for determining radar emission signal is multi order linear frequency keying system；The parameter of transmitted waveform is determined according to given index, index has: radar emission frequency range, maximum detectable range, maximum probe speed, range resolution, range accuracy, rate accuracy and the detectable ratio of making an uproar of frequency domain minimum letter, the parameter for determining that a waveform needs have: modulating bandwidth, coherent processing interval, the quantity of LFSK signal, the starting frequency difference between the number of steps and LFSK signal of each LFSK signal；The echo data of transmitting signal is handled, the distance and speed of target are solved.Calculation amount of the present invention is moderate, and detection accuracy is improved on the basis of ranging is unambiguous, and effectively reduces detection blind area caused by transmitting-receiving leakage.
Description
Technical field
The invention belongs to radar information technical field, especially a kind of transmitted waveform suitable for automobile collision avoidance radar is designed
Method and target acquisition algorithm.
Background technique
In order to improve the security performance of car steering, traffic accident, advanced driving assistance system are reduced
(Advanced Driver Assistance System.ADAS) has become a hot topic of research, it can automatically analyze collected
Information judges whether there is security risk, and whether needs to issue corresponding brake signal to automobile, and automobile is made to possess collision
The ability of early warning or autonomous collision avoidance.
Millimetre-wave radar detection range is remote, precision is high, is a reliable selection of ADAS sensor.Current vehicle-mounted millimeter
Based on 24GHz and 77GHz, the backward auxiliary for being respectively used to automobile detects wave radar with front.It is existing in the selection of waveform
Anticollision Radar generally use linear frequency modulation continuous wave (Linear Frequency Modulated Continuous
Waveform.LFMCW), the system also having uses multiple frequency keying (Multiple Frequency Shift
Keying.MFSK) system, different transmitted waveforms bring different detection performance and processing complexity.
Modulation Continuous Wave Radar utilizes the coupling of different sweep frequency bands corresponding beat signal frequency solution distance and speed,
Structure is simple, transmission power is low, more advantageous when detecting close-in target.But it excluding false target, selecting correctly to match
To aspect, which comes with some shortcomings.Classical symmetric triangular linear frequency modulation continuous wave system can not carry out target pairing, more
It is not used generally when target；The linear frequency modulation continuous wave system for becoming chirp rate needs to solve multiple equations with clock synchronization in target
Group, algorithm is complex, and when destination number increases, and calculation amount and EMS memory occupation amount can grow exponentiallys；It introduces
The linear frequency modulation continuous wave system of point-frequency signal reduces the complexity of target pairing, but the accuracy matched also decreases；
If distance and speed that moving-target detection (Moving Targets Detection.MTD) solves target are used instead, although being omitted
The step of target is matched, but for the detection of high-speed target, it increases the cost of product to the more demanding of hardware.
Multiple frequency keying system does not have to carry out target pairing, it utilizes the corresponding beat signal frequency of each LFSK signal
With the coupling of phase difference solution distance, speed, the interference of false target entirely eliminated, and calculation amount is relatively small, in more mesh
There is advantage when mark detection.But the result of detection is heavily dependent on the estimation of phase difference, due to taking for phase difference itself
It is smaller to be worth range, so the small error of phase difference estimation also can in the case where signal-to-noise ratio is not high or correlative accumulation duration is shorter
Bring the more apparent decline apart from tachometric survey precision.
Summary of the invention
The purpose of the present invention is to provide a kind of transmitted waveform design method and target spies suitable for automobile collision avoidance radar
Method of determining and calculating, improves the precision of target acquisition under the premise of calculation amount is moderate, while reducing detection blind area caused by transmitting-receiving leakage.
The technical solution for realizing the aim of the invention is as follows: a kind of transmitted waveform design side suitable for automobile collision avoidance radar
Method, comprising the following steps:
Step 1, the system for determining radar emission signal is MS-LFSK system, and the MS-LFSK waveform of a cycle is swept from above
Frequency range and lower sweep frequency band are constituted, and each sweep frequency band is synthesized by several LFSK signals；
Step 2, determine that the parameter of transmitted waveform, index have according to given index: radar emission frequency range, maximum probe away from
From, maximum probe speed, range resolution, range accuracy, rate accuracy and the detectable ratio of making an uproar of frequency domain minimum letter, determine a week
The parameter that the waveform of phase needs has: modulating bandwidth, coherent processing interval, LFSK signal quantity, each LFSK signal stepping
Starting frequency difference between several and LFSK signal.
A kind of target acquisition algorithm suitable for automobile collision avoidance radar, comprising the following steps:
Step 1, the system for determining radar emission signal is MS-LFSK system, and the MS-LFSK waveform of a cycle is swept from above
Frequency range and lower sweep frequency band are constituted, and each sweep frequency band is synthesized by several LFSK signals；
Step 2, determine that the parameter of transmitted waveform, index have according to given index: radar emission frequency range, maximum probe away from
From, maximum probe speed, range resolution, range accuracy, rate accuracy and the detectable ratio of making an uproar of frequency domain minimum letter, determine a wave
Shape need parameter have: modulating bandwidth, coherent processing interval, the quantity of LFSK signal, the number of steps of each LFSK signal and
Starting frequency difference between LFSK signal；
Step 3, the echo data of transmitting signal is handled, solves the distance and speed of target: returned what is received
The case where wave signal is mixed with local oscillator, obtains Beat Signal, is sampled to it and is corresponded to LFSK signal according to echo data is to its weight
Row is FFT by frequency sweep cycle to the data after rearrangement and cyclic graph accumulates, and carries out OS-CFAR to obtained 2-d spectrum, obtains
The spectrum peak point arrived just corresponds to a target, can calculate the corresponding beat signal frequency of target according to peak coordinate, then
Peak point is calculated in the phase difference of adjacent LFSK signal, comprehensive beat signal frequency and phase difference by phase-frequency response, then
By the processing of ambiguity solution, so that it may solve the distance and speed of target.
Compared with prior art, the present invention its remarkable advantage are as follows: (1) present invention incorporates linear frequency modulation continuous wave system with
The advantages of multiple frequency keying system, and compensate for their deficiency；(2) when detecting target, the frequency of Beat Signal is utilized
It with fuzzy, the not interference of false target of phase difference solution distance and speed, does not need to do target pairing, therefore calculation amount is suitable
In；(3) transmitted waveform is composed of the multiple groups LFSK signal at different frequency interval, is significantly mentioned on the basis of apart from unambiguous
The high precision of ranging and range rate, it is more accurate to measure；(4) it when detecting target, is cooperated, is effectively reduced using upper and lower sweep frequency band
Detection blind area.
Detailed description of the invention
Fig. 1 is the overall schematic of MS-LFSK transmitted waveform.
Fig. 2 (a) is the upper sweep frequency band schematic diagram of MS-LFSK, and Fig. 2 (b) is sweep frequency band schematic diagram under MS-LFSK.
Fig. 3 is the relational graph of phase difference estimation error and range error caused by it in the present invention, wherein (a) is phase difference
The probability density schematic diagram of evaluated error is (b) the probability density schematic diagram of range error.
Fig. 4 is the signal processing flow figure for the above sweep frequency band of the present invention.
Fig. 5 is the schematic diagram of range ambiguity resolving of the present invention.
Fig. 6 is blind area schematic diagram of the invention, wherein (a) is the respective detection blind area schematic diagram of upper and lower sweep frequency band, (b) is
Blind area schematic diagram when MS-LFSK or more frequency sweep combined detection.
Fig. 7 is the comparison diagram that the detection accuracy of MS-LFSK of the present invention and LFMCW, MFSK change with input signal-to-noise ratio, wherein
(a), (b), (c), (d) are respectively the contrast schematic diagram of ranging mean value, the mean value that tests the speed, ranging standard deviation, the standard deviation that tests the speed.
Specific embodiment
The present invention proposes that a kind of transmitted waveform design method suitable for automobile collision avoidance radar and the generation waveform are corresponding
Target acquisition algorithm, mainly include waveform configuration design, waveform parameter design and signal processing design three steps, wherein before
Two steps are waveform design method step, and third step is that the mistake of target acquisition is carried out using designed transmitted waveform
Journey.The structure design of MS-LFSK transmitted waveform is as shown in Figure 1.
Step 1: the structure of design MS-LFSK transmitted waveform: the system for determining radar emission signal is MS-LFSK system,
The MS-LFSK waveform of a cycle is made of upper sweep frequency band and lower sweep frequency band, and each sweep frequency band is synthesized by several LFSK signals again；
The MS-LFSK waveform of a cycle of the present invention is made of upper sweep frequency band and lower sweep frequency band, as shown in Figure 1.On one
Sweep frequency band and a lower sweep frequency band collectively constitute a coherent processing period, each each free M LFSK signal alternating of sweep frequency band
It arranges.
Shown in upper sweep frequency band waveform such as Fig. 2 (a), it is by M LFSK signal Sm,nIt constitutes: each stepped frequency radar, such as
S1,N, have N step into wherein the duration of each stepping is TStep, the time interval between two steppings is (M-1) TStep,
Difference on the frequency is fIncr；Generally speaking with regard to this M stepped frequency radar, the initial time of each signal is than a upper signal lag
TStep, initial frequency is also than the reduction of a upper signalHave:
For stepping Sm,nCorresponding frequency.
The waveform of lower frequency sweep is the mirror symmetry form of upper frequency swept waveform, shown in waveform such as Fig. 2 (b).
Step 2: the ginseng of transmitted waveform the waveform parameter of design MS-LFSK transmitting signal: is determined according to given index
Number, index have: radar emission frequency range, maximum detectable range, maximum probe speed, range resolution, range accuracy, rate accuracy
With the detectable ratio of making an uproar of frequency domain minimum letter, the parameter for determining that a waveform needs has: modulating bandwidth B mutually considers and handles cycle TCPI, LFSK
The quantity M of signal, the starting frequency difference between number of steps N and the LFSK signal of each LFSK signal
By taking the upper frequency sweep for emitting signal as an example, modulating bandwidth is determined by range resolution Δ R, i.e.,
Wherein c is the light velocity；
Determine coherent processing cycle TCPIWhen, when being FFT, appearance distance door is walked about in order to prevent, it is desirable that is swept at one
In the frequency period, the maximum displacement of vehicle must not exceed range resolution Δ R, i.e.,
VmaxFor maximum detectable speed；
Acquire TCPIValue after, according to formulaIt can also obtain frequency sweep slope；
According to sampling thheorem, to the sample rate of each frequency keying signalThe maximum of beat signal frequency should be not less than
The difference of value and minimum value, i.e.,
Wherein RmaxIt is maximum detectable range, | Vmax| it is the absolute value of maximum probe speed, fd.maxIt is Doppler frequency
Maximum value, τmaxIt is the maximum value of echo time delay, λ is the wavelength for emitting signal.And arithmetic speed is improved in order to use FFT,
On the basis of above formula, the number of steps N of each LFSK signal should also meet:
log2(N)∈Z (5)
Z is integer；
Then, it can be obtained by the difference on the frequency f of adjacent stepping in a LFSK signal according to NIncrContinue with each stepping
Time TStep:
In MS-LFSK system, target corresponding beat signal frequency at different LFSK signals is identical, phase not
Together, using at target spectral line frequency and phase difference can solve the fuzzy of distance and speed.It is corresponding to two neighboring LFSK signal
Peak value spectral line at phaseWithIt makes the difference, obtains phase difference
With target distance R0Meet:
fbFor the beat signal frequency at target spectral line；
NoteEvaluated error beSmaller range accuracy is higher, its obedience is desired for 0, variance and is
Normal distribution, whereinMeet:
SNR is time domain signal-to-noise ratio, and (SNRN) just constitutes the frequency domain signal-to-noise ratio after Beat Signal matched filtering, and δ is beat
The true value of frequency and the error of measured value, δ meet | δ |≤0.5；
As shown in Fig. 3 (a), this is that phase difference estimation of the target at frequency domain minimum detectable signal to noise ratio, when δ=0.5 is missed
The probability density figure of difference, since phase difference estimation error is as the distribution that range error is obeyed, so the probability of range error
Density is similar with phase difference, as shown in Fig. 3 (b).
Under conditions of minimum detectable signal to noise ratio, suitable confidence interval (1- α) is selected to carry out the section of normal distribution
Estimation, obtains:
It is possible thereby to estimate the maximum value of phase difference estimation error under the conditions of minimum detectable signal to noise ratio
According toWith range accuracy στCalculate the minimum value of not fuzzy distance
When the not fuzzy distance of transmitting signal is not less thanWhen, it, which corresponds to the distance for solving and, just can satisfy ranging
The requirement of precision.
Maximum detectable range can not be chosen in the upper-bound theory of fuzzy distance, it is contemplated that the influence of noise is relaxed
Extremely:
Improve detection accuracy using the method for not fuzzy distance recursion in the present invention, need not obscured with halving method away from
From fromStart etc. to divide conductI.e.
Until not fuzzy distanceIt is less than
The difference of original frequency between each LFSK signalMeet following relationship:
It is smaller,It is bigger, it is just less susceptible to generate the fuzzy of ranging.
The number of bisection determines the number M of LFSK signal, has:
It is hereby achieved that each not fuzzy distanceAgain willNumerical value substitute into formula (14), so that it may acquire
So far, the upper frequency swept waveform of MS-LFSK signal can be determined according to above-mentioned each parameter, and lower frequency swept waveform is above to sweep
The mirror image of frequency, so the transmitted waveform parameter of lower frequency sweep can also be extrapolated.
Step 3: it designs the signal processing mode of MS-LFSK: the echo data of transmitting signal being handled, mesh is solved
Target distance and speed: the echo-signal received being mixed with local oscillator, obtains Beat Signal, is sampled to it and according to number of echoes
It is reset according to the case where corresponding LFSK signal, FFT is done by frequency sweep cycle to the data after rearrangement and cyclic graph accumulates, and to
The 2-d spectrum arrived carries out OS-CFAR, and obtained spectrum peak point just corresponds to a target, can be calculated according to peak coordinate
The corresponding beat signal frequency of target, then peak point is calculated in the phase difference of adjacent LFSK signal by phase-frequency response, it is comprehensive
Beat signal frequency and phase difference are closed, using the processing of ambiguity solution, so that it may solve the distance and speed of target.
In the upper sweep frequency band of MS-LFSK, the process of signal processing is as shown in Figure 4.Detailed process is as follows:
Sample Beat Signal.The echo-signal received is mixed with local oscillator, obtains Beat Signal, and in each TStep
Ending to Beat Signal sample, obtain the array of sampled result
Data rearrangement.By arrayThe two-dimensional array of M × N is rearranged by the value of M, i.e. every a line of two-dimensional array is corresponding
Be beat result that a complete stepped frequency radar is arranged by shooting sequence.
FFT and cyclic graph accumulate.FFT is individually done to every a line of two-dimensional array, obtains M frequency spectrum Wk[N], k=1,
2,...,M.By Wk[N] modulus does mould square and M row result correspondence is added later, the accumulation of execution cycle figure, i.e.,
Carry out the CFAR detection of spectral peak.Since target may be relatively more in actual environment, so using OS-CFAR.
Solve the corresponding frequency of spectral peak and phase.Assuming that being p more than the detection unit where the spectral peak of thresholding, then corresponding
Difference frequency fb(p) it can be determined by following formula:
The corresponding phase of the spectral peakAre as follows:
The phase difference of so two neighboring spectral peak are as follows:
Solve fuzzy distanceAccording to known parameterfb(p) andIt is solved by following formula fuzzy
Distance
K=1,2 ..., M-1
In above formula,Value withReduction and it is gradually accurate but also increasingly fuzzyyer, so also needing
It adjusts the distance ambiguity solution, schematic diagram such as Fig. 5.Use R0Indicate the distance of target eventually detected, firstValue be assigned to
R0, when then calculating k from 2 to M-1Find the q for meeting following formulak(p):
And new result iteration is given to R0, i.e.,
K=M-1 is iterated to always, the target range R finally measured0。
Solve the speed of target.By R0It substitutes into following formula and obtains the speed V of target0:
So far, the calculating to target range and speed, the data processing method of lower sweep frequency band are completed in upper sweep frequency band
It is consistent with upper frequency sweep.
In addition in systems in practice, it is bistatic due to the antenna of continuous wave radar and works always, so connects
Transmitting signal can also be received while receiving target echo signal by receiving antenna, then will generate the zero of interference after mixed
Frequency signal, this may flood the target echo signal near zero-frequency, detection blind area be formed, such as Fig. 6 (a).It can be with by schematic diagram
Find out, the detection blind area overwhelming majority of upper and lower sweep frequency band is not overlapped, therefore upper and lower sweep frequency band combined detection is utilized in MS-LFSK
Target can detect target separate in script blind area in upper sweep frequency band, detect approaching in script blind area in lower sweep frequency band
Target, to reduce detection blind area, as shown in Fig. 6 (b).
The following describes the present invention in detail with reference to examples.
Embodiment
In the present embodiment, the racon of setting is as shown in table 1:
Table 1
Parameter according to the MS-LFSK waveform of These parameters design is as shown in table 2.
Table 2
In addition, we devise LFMCW's and MFSK under identical index in order to compare the performance of various transmitted waveforms
Waveform parameter.
For becoming chirp rate LFMCW, the transmitted waveform parameter under the system is as shown in table 3:
Table 3
Transmitted waveform parameter under MFSK system is as shown in table 4:
Table 4
Fig. 7 is the simulation result of matlab, and it is 30m that a distance, which is arranged, and speed is the simple target of 10m/s, by frequency domain
Signal-to-noise ratio value between 15dB to 40dB does 1000 Monte Carlo Experiments every ranging and range rate of the 1dB to 3 kinds of waveforms, and
Study the mean value and standard deviation of distance and speed that they are acquired.
In figure, * indicates to become the Effect on Detecting of chirp rate LFMCW, and the detection result of+expression MFSK signal, o is featured
Detection result under MS-LFSK system.
When noise is relatively high it can be seen from Fig. 7 (a), Fig. 7 (b), 3 kinds of waveforms can accurately ranging and range rate；And when frequency
When domain signal-to-noise ratio is lower than 20dB, relatively large deviation occurs for the measurement mean value for becoming chirp rate LFMCW, and MFSK signal cannot be surveyed correctly
Amount, on the contrary, the measurement result of MS-LFSK waveform is still very accurate.
When noise is relatively high it can be seen from Fig. 7 (c), Fig. 7 (d), the precision of 3 kinds of waveform ranging and range rates is relatively high；And
When frequency domain signal-to-noise ratio is lower than 19dB, there is significant decline in the ranging and range rate precision for becoming chirp rate LFMCW；When frequency domain noise
When than being lower than 24dB, the measurement accuracy of MFSK signal is not just up to standard.And in the change procedure of frequency domain signal-to-noise ratio, MS-LFSK
The measurement accuracy of waveform is very high always.
In summary, it is measured in terms of the accuracy of detection and precision two, when the decline of frequency domain signal-to-noise ratio, modified tone frequency
The detection performance of slope LFMCW is remarkably decreased, and MFSK system shows more obvious in terms of degradation, on the contrary, in frequency domain
During signal-to-noise ratio changes, the Effect on Detecting of MS-LFSK waveform is fine always.
Claims (7)
1. a kind of transmitted waveform design method suitable for automobile collision avoidance radar, which comprises the following steps:
Step 1, the system for determining radar emission signal is MS-LFSK system, and the MS-LFSK waveform of a cycle is by upper sweep frequency band
It is constituted with lower sweep frequency band, each sweep frequency band is synthesized by several LFSK signals；
Step 2, determine that the parameter of transmitted waveform, index have according to given index: radar emission frequency range, maximum detectable range,
Maximum probe speed, range resolution, range accuracy, rate accuracy and the detectable ratio of making an uproar of frequency domain minimum letter, determine a cycle
Waveform need parameter have: modulating bandwidth, coherent processing interval, the quantity of LFSK signal, the number of steps of each LFSK signal
And the starting frequency difference between LFSK signal.
2. being suitable for the transmitted waveform design method of automobile collision avoidance radar according to claim 1, which is characterized in that step 1
Specifically:
The MS-LFSK waveform of a cycle is made of upper sweep frequency band and lower sweep frequency band, a upper sweep frequency band and a lower sweep frequency band
Collectively constitute a coherent processing cycle TCPI, each each free M LFSK signal of sweep frequency band is alternately arranged；
Upper sweep frequency band is by M LFSK signal Sm,nConstitute: each stepped frequency radar has N step into wherein each stepping is held
The continuous time is TStep, the time interval between two steppings is (M-1) TStep, difference on the frequency fIncr；The initial time of each signal
All than a upper signal lag TStep, initial frequency is also than the reduction of a upper signalHave:
For stepping Sm,nCorresponding frequency；
The waveform of lower frequency sweep is the mirror symmetry form of upper frequency swept waveform.
3. special according to claim 1 suitable for the transmitted waveform of automobile collision avoidance radar and corresponding target acquisition algorithm
Sign is, step 2 method particularly includes:
It is as follows firstly the need of the transmitted waveform parameter known: modulating bandwidth B, coherent processing cycle TCPI, the quantity M of LFSK signal,
Starting frequency difference between the number of steps N of each LFSK signal and each LFSK signal
By taking the upper frequency sweep for emitting signal as an example, modulating bandwidth is determined by range resolution Δ R, i.e.,
Wherein c is the light velocity；
Determine coherent processing cycle TCPIWhen, in a frequency sweep cycle, the maximum displacement of vehicle must not exceed range resolution Δ
R, i.e.,
VmaxFor maximum detectable speed；
Acquire TCPIValue after, according to formulaFrequency sweep slope can be obtained；
According to sampling thheorem, to the sample rate of each frequency keying signalShould not less than beat signal frequency maximum value with
The difference of minimum value, i.e.,
Wherein RmaxIt is maximum detectable range, | Vmax| it is the absolute value of maximum detectable speed, fd.maxIt is Doppler frequency
Maximum value, τmaxIt is the maximum value of echo time delay, λ is the wavelength for emitting signal；On the basis of above formula, each LFSK signal
Number of steps N should also meet:
log2(N)∈Z (5)
Z is integer；
Then, the difference on the frequency f of adjacent stepping in a LFSK signal can be obtained according to NIncrWith each stepping duration
TStep:
To phase at the corresponding peak value spectral line of two neighboring LFSK signalWithIt makes the difference, obtains phase difference
With target distance R0Meet:
fbFor corresponding beat signal frequency at target spectral line；
Evaluated error beIts obedience is desired for 0, variance and isNormal distribution, whereinMeet:
SNR is time domain signal-to-noise ratio, and (SNRN) constitutes the frequency domain signal-to-noise ratio after Beat Signal matched filtering, and δ is that difference frequency is true
The error of real value and measured value, δ meet | δ |≤0.5；
Under conditions of minimum detectable signal to noise ratio, selects confidence interval (1- α) to carry out the interval estimation of normal distribution, obtains:
Thus the maximum value of phase difference estimation error under the conditions of minimum detectable signal to noise ratio is estimated
According toWith range accuracy στCalculate the minimum value of not fuzzy distance
Solve the upper limit of not fuzzy distance
Using halving method will not fuzzy distance fromStart etc. to divide conductI.e.
Until not fuzzy distanceIt is less than
The difference of original frequency between each LFSK signalMeet following relationship:
The number of bisection determines the number M of LFSK signal, has:
This makes it possible to obtain each not fuzzy distancesAgain willNumerical value substitute into formula (14), acquire
Determine that the upper frequency swept waveform of MS-LFSK signal, lower frequency swept waveform are the mirror image of upper frequency sweep according to above-mentioned each parameter.
4. a kind of target acquisition algorithm suitable for automobile collision avoidance radar, which comprises the following steps:
Step 1, the system for determining radar emission signal is MS-LFSK system, and the MS-LFSK waveform of a cycle is by upper sweep frequency band
It is constituted with lower sweep frequency band, each sweep frequency band is synthesized by several LFSK signals；
Step 2, determine that the parameter of transmitted waveform, index have according to given index: radar emission frequency range, maximum detectable range,
Maximum probe speed, range resolution, range accuracy, rate accuracy and the detectable ratio of making an uproar of frequency domain minimum letter, determine a cycle
Waveform need parameter have: modulating bandwidth, coherent processing interval, the quantity of LFSK signal, the number of steps of each LFSK signal
And the starting frequency difference between LFSK signal；
Step 3, the echo data of transmitting signal is handled, solves the distance and speed of target: the echo received is believed
The case where number being mixed with local oscillator, obtain Beat Signal, sample to it and correspond to LFSK signal according to echo data resets it, right
Data after rearrangement are FFT by frequency sweep cycle and cyclic graph accumulates, and carry out OS-CFAR to obtained 2-d spectrum, obtain
Spectrum peak point corresponds to a target, calculates the corresponding beat signal frequency of target according to peak coordinate, then by phase-frequency response
Phase difference of the peak point at adjacent LFSK signal, comprehensive beat signal frequency and phase difference is calculated, using ambiguity solution
Processing, solve the distance and speed of target.
5. the target acquisition algorithm according to claim 4 suitable for automobile collision avoidance radar, which is characterized in that step 1 tool
Body are as follows:
The MS-LFSK waveform of a cycle is made of upper sweep frequency band and lower sweep frequency band, a upper sweep frequency band and a lower sweep frequency band
Collectively constitute a coherent processing cycle TCPI, each each free M LFSK signal of sweep frequency band is alternately arranged；
Upper sweep frequency band is by M LFSK signal Sm,nConstitute: each stepped frequency radar has N step into wherein each stepping is held
The continuous time is TStep, the time interval between two steppings is (M-1) TStep, difference on the frequency fIncr；With regard to this M frequency stepping letter
Number generally speaking, the initial time of each signal is than a upper signal lag TStep, initial frequency is also than a upper signal
ReduceHave:
For stepping Sm,nCorresponding frequency；
The waveform of lower frequency sweep is the mirror symmetry form of upper frequency swept waveform.
6. the target acquisition algorithm according to claim 4 suitable for automobile collision avoidance radar, which is characterized in that step 2 tool
Body are as follows:
It is as follows firstly the need of the transmitted waveform parameter known: modulating bandwidth B, coherent processing cycle TCPI, the quantity M of LFSK signal,
Starting frequency difference between the number of steps N of each LFSK signal and each LFSK signal
By taking the upper frequency sweep for emitting signal as an example, modulating bandwidth is determined by range resolution Δ R, i.e.,
Wherein c is the light velocity；
Determine coherent processing cycle TCPIWhen, in a frequency sweep cycle, the maximum displacement of vehicle must not exceed range resolution Δ
R, i.e.,
VmaxFor maximum detectable speed；
Acquire TCPIValue after, according to formulaFrequency sweep slope can be obtained；
According to sampling thheorem, to the sample rate of each frequency keying signalShould not less than beat signal frequency maximum value with
The difference of minimum value, i.e.,
Wherein RmaxIt is maximum detectable range, | Vmax| it is the absolute value of maximum detectable speed, fd.maxIt is Doppler frequency
Maximum value, τmaxIt is the maximum value of echo time delay, λ is the wavelength for emitting signal；On the basis of above formula, each LFSK signal
Number of steps N should also meet:
log2(N)∈Z (5)
Z is integer；
Then, the difference on the frequency f of adjacent stepping in a LFSK signal can be obtained according to NIncrWith each stepping duration
TStep:
To phase at the corresponding peak value spectral line of two neighboring LFSK signalWithIt makes the difference, obtains phase difference
With target distance R0Meet:
fbFor corresponding beat signal frequency at target spectral line；
Evaluated error beIts obedience is desired for 0, variance and isNormal distribution, whereinMeet:
SNR is time domain signal-to-noise ratio, and (SNRN) constitutes the frequency domain signal-to-noise ratio after Beat Signal matched filtering, and δ is that difference frequency is true
The error of real value and measured value, δ meet | δ |≤0.5；
Under conditions of minimum detectable signal to noise ratio, selects confidence interval (1- α) to carry out the interval estimation of normal distribution, obtains:
Thus the maximum value of phase difference estimation error under the conditions of minimum detectable signal to noise ratio is estimated
According toWith range accuracy στCalculate the minimum value of not fuzzy distance
Solve the upper limit of not fuzzy distance
Using halving method will not fuzzy distance fromStart etc. to divide conductI.e.
Until not fuzzy distanceIt is less than
The difference of original frequency between each LFSK signalMeet following relationship:
The number of bisection determines the number M of LFSK signal, has:
This makes it possible to obtain each not fuzzy distancesAgain willNumerical value substitute into formula (14), acquire
Determine that the upper frequency swept waveform of MS-LFSK signal, lower frequency swept waveform are the mirror image of upper frequency sweep according to above-mentioned each parameter.
7. the target acquisition algorithm according to claim 4 suitable for automobile collision avoidance radar, which is characterized in that step 3 tool
Body are as follows:
Sample Beat Signal；The echo-signal received is mixed with local oscillation signal, obtains Beat Signal, and in each TStep
Ending to Beat Signal sample, obtain the array of sampled result
Data rearrangement；By arrayThe two-dimensional array of M × N is rearranged by the value of M, i.e. every a line of two-dimensional array is corresponding to be
One complete stepped frequency radar presses the beat result of shooting sequence arrangement；
FFT and cyclic graph accumulate；FFT is individually done to every a line of two-dimensional array, obtains M frequency spectrum Wk[N], k=1,2 ..., M；
By Wk[N] modulus does mould square and M row result correspondence is added later, the accumulation of execution cycle figure, i.e.,
Carry out the CFAR detection of spectral peak；
Solve the corresponding frequency of spectral peak and phase；Assuming that being p more than the detection unit where the spectral peak of thresholding, then corresponding difference
Beat frequency fb(p) it can be determined by following formula:
The corresponding phase of the spectral peakAre as follows:
The phase difference of two neighboring spectral peak are as follows:
Solve fuzzy distanceAccording to known parameterfb(p) andFuzzy distance is solved by following formula
Solve not fuzzy distance；Use R0Indicate the distance of target eventually detected, firstValue be assigned to R0, then
When calculating k from 2 to M-1Find the q for meeting following formulak(p):
And by new result iteration to R0, i.e.,
K=M-1 is iterated to always, the target range R finally measured0。
Solve the speed of target；By R0It substitutes into following formula and obtains the speed V of target0:
So far, complete the calculating to target range and speed in upper sweep frequency band, the data processing method of lower sweep frequency band with it is upper
Frequency sweep is consistent.
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| WO2022247593A1 (en) * | 2021-05-28 | 2022-12-01 | 华为技术有限公司 | Distance measurement method and apparatus |
| CN113759327A (en) * | 2021-09-29 | 2021-12-07 | 桂林长海发展有限责任公司 | Interference method and system for linear frequency modulation continuous wave radar and electronic equipment |
| CN113759327B (en) * | 2021-09-29 | 2024-05-14 | 桂林长海发展有限责任公司 | Interference method, system and electronic equipment for linear frequency modulation continuous wave radar |
| CN114217288A (en) * | 2022-02-22 | 2022-03-22 | 湖南纳雷科技有限公司 | Method and system for synchronizing high coherence between chips of echo signals of radar |
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