CN107688178A - A kind of sawtooth waveforms ranging and range rate method based on 77GHz millimetre-wave radars - Google Patents
A kind of sawtooth waveforms ranging and range rate method based on 77GHz millimetre-wave radars Download PDFInfo
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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
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- G01S13/583—Velocity or trajectory determination systems; Sense-of-movement determination systems using transmission of continuous unmodulated waves, amplitude-, frequency-, or phase-modulated waves and based upon the Doppler effect resulting from movement of targets
- G01S13/584—Velocity or trajectory determination systems; Sense-of-movement determination systems using transmission of continuous unmodulated waves, amplitude-, frequency-, or phase-modulated waves and based upon the Doppler effect resulting from movement of targets adapted for simultaneous range and velocity measurements
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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
- 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
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- G01S13/343—Systems for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated using transmission of continuous, frequency-modulated waves while heterodyning the received signal, or a signal derived therefrom, with a locally-generated signal related to the contemporaneously transmitted signal using sawtooth modulation
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Abstract
The invention provides a kind of sawtooth waveforms ranging and range rate method of 77GHz millimetre-wave radars, comprise the following steps：a.NtRoot transmitting antenna launches the continuous sawtooth waveforms transmission signal of identical frequency modulation and composition virtual array successively；b.NrRoot reception antenna receives the echo-signal of the transmission signal, forms virtual arrayWherein, Ns=fsT, Nsa1For transmit cycle；C. windowing FFT is carried out along fast time dimension to the reception signal of each transmit cycle, every antenna, obtainedNqFFTCounted for fast time dimension FFT；D. are carried out by slow time dimension FFT, is obtained for every reception antenna, the reception signal of different distance unitNsFFTCounted for slow time dimension FFT；E. to YVFFIt is each carry out phase compensation apart from speed unit, obtainF. beam forming is carried out apart from speed unit to all, obtainedG. CFAR CFAR detections are carried out to the data after beam forming, obtains CFAR detection result；And h. brings CFAR detection result into formula, speed v and distance parameter r are obtained.
Description
Technical Field
The invention relates to the field of antennas, in particular to a sawtooth wave distance and speed measurement method based on a 77GHz millimeter wave radar.
Background
Millimeter wave radar is widely applied to the field of traffic detection at present, and 77GHz millimeter wave radar has great advantages in volume, detection precision and detection distance, because a 77GHz radar microstrip antenna can easily realize narrow beams and high gain under a smaller antenna volume. Because of these characteristics, a 77 GHz-based millimeter wave radar will become a standard configuration for active security. At present, known mature 77GHz millimeter wave radar schemes are all from foreign suppliers, and the research on the aspects is less in China, whether colleges and universities or suppliers. At present, the research on radar algorithm by related companies and colleges in China mainly focuses on the research on a triangular wave scheme, and the following patents mainly exist:
1. a method for acquiring the number of multiple targets of a vehicle-mounted millimeter wave radar system (the patent application number is 201510875924.0) provides an algorithm for detecting the distance between multiple targets and the speed of a vehicle by adopting a radar with a variable-period triangular wave.
2. "a millimeter wave radar ranging system" (patent application No. 201520531100.7), a millimeter wave FMCW radar ranging system based on triangular waves is introduced.
3. "a method for estimating and classifying a motion state of a front object based on a vehicle-mounted millimeter wave radar" (patent application No. 201510085048.1), a method for estimating a motion state of a front object based on a vehicle-mounted millimeter wave radar is introduced, which is characterized in that: based on the lateral speed information of limited front object motion directly measured by the vehicle-mounted millimeter wave radar, a motion equation of the front object in the geodetic coordinate system is established, and the motion state of the front object is accurately estimated in real time by using the adaptive Kalman filtering estimation algorithm.
4. The multi-target detection method of the vehicle-mounted millimeter wave radar system (patent application number 201510874147.8) uses a frequency clustering algorithm to obtain a Doppler frequency matrix of a CW waveform echo signal and calculate a relative velocity matrix; and (3) obtaining frequency values of the up-down frequency sweep by using a frequency agglomeration algorithm in the FMCW up-down frequency sweep, and solving a speed matrix and a distance matrix of the target.
5. A multi-target detection device of a vehicle-mounted millimeter wave radar system (patent application number 201510875902.4) transmits a periodic FMCW and CW combined waveform, receives an echo signal, obtains frequency values of upper and lower frequency sweeps in the FMCW upper and lower frequency sweeps, and solves a speed matrix and a distance matrix of a target.
Generally, the existing automotive radar basically uses a Frequency Modulated Continuous Wave (FMCW) radar, and the radar of the type has the main advantages of small radiation power, high ranging and speed measuring accuracy, relatively simple equipment, easiness in solid state design realization, good Electronic Countermeasure (ECM) and low interception probability (LPI) performance and the like. The working principle is that coherent mixing is carried out on a part of echo signals and transmitting signals to obtain difference frequency signals containing target distance and speed information, and then the difference frequency signals are processed and detected to obtain the distance and the speed of a target.
For speed measurement and distance measurement with FMCW chirp, there are generally two methods: triangular and sawtooth waves. The modulation mode of the triangular wave is generally called as slow FMCW, and this mode obtains both the distance and the speed of the target, but the wavelength is longer and the speed is slower, and the method is generally used for the traditional system with lower signal processing performance. The sawtooth wave has a short wavelength and high speed and anti-interference capability, although the distance and speed of a target object cannot be obtained simultaneously through one-time Fast Fourier Transform (FFT), the distance and speed of the object can be obtained through a two-dimensional FFT (fast Fourier transform) mode firstly and then through a speed measuring mode, with the increasing processing capability of a chip, the memory space is larger and larger, and sawtooth wave frequency modulation is a new fast FMCW modulation mode which is more and more widely adopted in recent years.
As described in the above patent solutions, the correlation algorithms are developed based on a triangular wave modulation method, and there is no mention of a sawtooth wave correlation algorithm.
Disclosure of Invention
Based on the defects of the prior art and the characteristics of a 77GHz millimeter wave radar, the invention provides a method for measuring the distance and the speed of a sawtooth wave radar transmitting signal based on multiple transmitting and multiple receiving antennas, which can simultaneously realize high-precision short-distance and long-distance multi-target distance and speed measurement.
The invention relates to a sawtooth wave distance and speed measurement method based on a 77GHz millimeter wave radar, which comprises the following steps:
a.Ntthe root transmitting antenna sequentially transmits the same frequency modulation continuous sawtooth wave transmitting signals to form a virtual array, and the plurality of transmitting antennas adopt different frequency sweep bandwidths and sawtooth wave numbers;
b.Nrthe root receiving antenna receives the echo signals of the transmitting signals, and the echo signals of the transmitting signals under different transmitting days received by the same receiving antenna in a transmitting period are combined to form a virtual arrayWherein N iss＝fsT，Nsa1Is a transmission period;
c. carrying out windowing FFT on the received signal of each antenna along the fast time dimension in each transmission period to obtainNqFFTFast time dimension FFT points;
d. carrying out slow time dimension FFT on the received signals of different distance units of each receiving antenna to obtainNsFFTThe number of FFT points in the slow time dimension;
e. for YVFFEach distance-velocity unit of (1) is subjected to phase compensation to obtain
f. Performing beam forming on all the distance-velocity units to obtain
g. Performing Constant False Alarm Rate (CFAR) detection on the data subjected to beam forming to obtain a constant false alarm rate detection result; and
h. substituting the constant false alarm detection result into the following formula (4) and formula (5) to obtain the velocity v and the distance parameter r
Wherein f is0The carrier center frequency is, mu is B/T is the sweep slope, B and T are the sweep bandwidth and the up sweep period, respectively, c is the electromagnetic wave freeThe propagation velocity of the space.
Preferably, in step a, of the plurality of transmitting antennas, the transmitting antenna for performing short-distance detection uses a high sweep bandwidth, and the transmitting antenna for performing long-distance detection uses a small sweep bandwidth.
Preferably, in step f, for the short-distance target signal, non-coherent accumulation may be performed on each distance-velocity unit signal of the receiving antenna after the two-dimensional FFT, so as to obtain an accumulation gain.
Preferably, in step g, the noise region and the clutter region are detected by CFAR with different criteria.
Preferably, step h further comprises measuring an angle parameter.
Preferably, after the step h, a velocity deblurring step is provided, which comprises a near-distance velocity deblurring step and a far-distance velocity deblurring step.
The invention has the following beneficial effects: the scheme of the invention can simultaneously realize high-precision short-distance and long-distance multi-target distance measurement and speed measurement, and through simulation test, the scheme of the invention keeps the detection error of the target at a quite low level.
Drawings
Fig. 1 is a time-frequency diagram of a sawtooth wave transmitting signal.
Fig. 2 is a design scheme of a sawtooth wave transmitting signal based on multiple antennas.
Fig. 3 is a design scheme of a sawtooth wave transmitting signal based on multiple antennas.
Fig. 4 is a three-dimensional graphical representation of a radar data block during a coherent processing interval.
FIG. 5 is an algorithm flow diagram of the present invention.
Fig. 6 is a schematic diagram of virtual array phase compensation.
Fig. 7 is a CFAR detection schematic.
Fig. 8 is a schematic view of the angle parameter.
Detailed Description
The invention is further illustrated by the following examples, which are intended only for a better understanding of the contents of the study of the invention and are not intended to limit the scope of the invention.
Referring first to FIG. 1, a time-frequency diagram of a sawtooth transmission signal will be described. As shown in fig. 1, the i (i ═ 1, 2.., N)Sa) And transmitting signals in a frequency sweep period:
where A is the amplitude of the transmitted signal, f0Is the carrier center frequency and is the carrier center frequency,for the initial phase, mu is B/T is the slope of the sweep frequency, B and T are the sweep frequency bandwidth and the up sweep frequency period, respectively, NsaIs the number of sawtooth waves in one coherent processing cycle.
Considering that at time t-0, there is a target in front of the radar at a distance r and a velocity v (the radial velocity of the target with respect to the radar, positive in the direction of approaching the radar), the signal is received:
in the formula, A0In order to receive the signal amplitude, tau is 2(r-vt)/c is the time delay caused by the distance between the target and the radar at the time t, c is the propagation speed of the electromagnetic wave in free space, and taud＝2rmaxAnd/c is the maximum delay.
Mixing and low-pass filtering the received signal and the transmitted signal to obtain an intermediate frequency signal:
the fast time dimension is FFT, resulting in frequencies for r and v as:
the FFT is performed on the slow time dimension, resulting in a frequency for v as:
the target speed v can be obtained from the above equation (5), and the distance r can be obtained by bringing v into equation (4).
The invention provides a sawtooth wave distance and speed measurement method of a 77GHz millimeter wave radar. Fig. 2 is a schematic diagram of a sawtooth wave transmission signal design scheme based on multiple antennas according to the present invention. The multiple transmitting antennas sequentially transmit the same frequency modulation continuous wave to form a virtual array with a larger receiving aperture, but the sampling rate of a slow time dimension is reduced, and the sweep period needs to be further reduced in order to keep the original unambiguous velocity measurement range.
Therefore, on the basis of the design of the multi-antenna transmitting mechanism, the invention utilizes different PRFs to solve the speed ambiguity, thereby reducing the algorithm complexity; and different sweep bandwidths and numbers of sawtooth waves are used. The short-distance detection needs higher distance resolution and adopts higher scanning bandwidth. Remote detection requires detection of a longer distance and a smaller scanning bandwidth. The multi-antenna transmission design of the present invention is formed as shown in fig. 3.
The present invention will be described below with reference to a sawtooth wave receiving signal apparatus based on multiple antennasAnd (6) calculating a scheme. Consider having NtRoot transmitting antenna, NrRoot receiving antenna, NtThe root transmitting antennas transmit the same frequency modulation continuous wave (one transmitting period) in turn and form a virtual array. The transmission period in a coherent processing time is Nsa1Then a three-dimensional graph of the received signal during a coherent processing time is shown in fig. 4.
As can be seen from the formula (3), in the i (i ═ 1., Nsa) Within a transmission period, the k (k 1.., N)r) The m (m 1, N) th reception of the receiving antennat) The echo complex signal of the transmission signal of the root transmitting antenna is:
its sampling signal is recorded asWherein N iss＝fsT, then one coherent processing interval, k (k 1.., N)r) The m (m 1.., N.) of the reception of the root reception antennat) The sampling signal of the transmission signal of the root transmitting antenna is:
combining echo signals of different transmitting antenna transmitting signals received by the same receiving antenna in a transmitting period to form a virtual arrayNo. (i) ═ 1.., Nsa) The received signal in each transmission period is:
the method of the present invention is described in detail below with reference to the algorithmic flow chart of the present invention of FIG. 5.
Step c, fast time dimension FFT
Performing a windowed FFT on the received signal along the fast time dimension toWithin a transmission period, the k (k 1.., N)r) Received signal of root receiving antennaFor example, the following steps are carried out:
in the formula, wqIs a window function of NSX 1 column vector, and symbol ⊙ represents the Hadamard product of the two vectors, i.e., the multiplication of corresponding elements, FFT (·) refers to the FFT operation on the signal.
As can be seen from equation (4), assuming that there is a target with a distance r and a velocity v, after performing FFT on the fast time dimension, the target spectrum peak position is:
since the sawtooth sweep period T is very small, fr,vAnd the value is approximately equal to 2 Br/cT. Thus, the fast time dimension may be equivalent to the distance dimension and the spectral cells may be equivalent to the distance cells.
Carrying out windowing FFT (fast Fourier transform) on the received signal of each antenna in each transmission period to obtainNqFFTThe number of FFT points in the fast time dimension.
Step d, performing slow time dimension FFT
For YVFA slow time dimension FFT is performed with the k (k 1.., N.) th time dimensionr) A receiving antenna, i.e., the l 1s) Data of a spectrum unitFor example, the following steps are carried out:
in the formula, wsIs a window function of NsaA column vector of x 1.
As can be seen from equation (5), assuming that there is a target with a distance r and a velocity v, after performing FFT on the fast time dimension, the target spectrum peak position is:
after the FFT in the slow time dimension, the position of the target spectrum peak is only related to the speed, so the slow time dimension can be regarded as the speed dimension. Carrying out slow time dimension FFT on the received signals of different distance units of each receiving antenna to obtainNsFFTThe number of FFT points in the slow time dimension.
Step e. virtual array phase compensation
Consider the combination of received signals over a transmit period to form Nt×NrWhen the antenna receives the array virtually to increase the array gain, because of the problem of target motion, phase compensation is needed to change the virtual array into a linear array with a known geometry, so that the beam forming achieves the ideal effect.
As shown in FIG. 6, assume Nt＝2，Nr4, there is a far field target with azimuth theta,at a distance d from the transmitting antenna 11At a distance d from the receiving antenna 12And assuming that the signal reflection angle is the same as the incident angle, the movement of the target in a triangular period does not cause angle change, and the relative speed of the target and the radar is not changed.
The relationship between the wave paths of different transmitting antennas and receiving antennas is shown in the following table:
as can be seen from the above table, in theory, the wave path difference between two adjacent antennas of the virtual array is dsin θ, so that the 2 × 4(2 transmitting and 4 receiving) array can be changed into a virtual 1 × 8 uniform linear array.
In practice, there is relative motion between the target and the radar, and the motion distance within one triangular period has negligible effect on the frequency of the intermediate frequency signal, but cannot have negligible effect on the path difference (phase), i.e. the path difference Δ b ≠ d sin θ between the virtual array receive antennas 4 and 5 is unknown and no longer a uniform linear array.
Assuming that only one target signal is present in one range-velocity unit, the compensation is designed as follows.
Consider the ith (i ═ 1.., N)qFFT) A distance dimension unit, i.e., the l (1), NsFFT) A target exists in each speed dimension unit, and a complex vector of a frequency spectrum unit where the target is located is taken:
taking outAndhas a phase ofAndobtaining a phase difference:
where α is the phase difference due to the antenna spacing and β is the phase difference due to the change in the target distance within a triangular time, the compensated phase is given by equations (14) and (15)
Although it is used forThere may be ambiguity of integer multiples of 2 pi without affecting the final result.
The phase compensated signals are:
wherein,
for YVFFEach distance-speed ofThe degree units are all subjected to phase compensation to obtain
Step f, non-adaptive beam forming
Suppose the beam center azimuth is θ0Considering the transmitting and receiving array structure of the system, the space domain steering vector is as follows:
the method can be used for the ith (i ═ 1.., N.)qFFT) A distance dimension unit, i.e., the l (1), NsFFT) N of velocity dimension unitt×NrCarrying out weighted summation on the array element signals of the virtual receiving antenna, wherein the output signals of the conventional non-adaptive wave beams are as follows:
in the formula, H represents conjugate transpose, and the window function w is NtNrX 1 column vector, data weight providing angular domain sidelobe suppression, steering vector as(θ0) Provide for the signal from theta0The maximum coherent accumulation of the direction signals carries out beam forming on all the distance-speed units to obtain
For a short-distance target signal, incoherent accumulation can be performed on each distance-speed unit signal of the receiving antenna after two-dimensional FFT to obtain accumulation gain, and meanwhile, the algorithm complexity is reduced as follows:
step g, CFAR detection is carried out
Constant False Alarm Rate (CFAR) detection is performed on the beamformed data, wherein CFARs of different criteria are used for noise and clutter areas.
The CFAR detection calculation amount of all distance-speed units is large, whether the amplitude value of the distance unit is an area peak value or not is judged before CFAR detection, and therefore useless signal processing can be avoided.
The CFAR detection schematic is shown in fig. 7.
In FIG. 7, the input cell signal is Zc＝Z⊙Z*And the symbol denotes the conjugate of the vector. Will ZcAnd comparing the value of each distance-speed unit with a threshold value, and if the value is greater than the threshold value, determining that the target exists at the point.
Because the speed of the radar is known a priori, the speed units where the stationary clutter of different distance units in the interested range are located can be obtained through calculation, the two-dimensional plane is divided into a noise area and a clutter area, and different CFAR (constant false alarm rate) criteria are respectively utilized for target detection.
CFAR for noise region
Respectively calculating the mean values of the distance dimension and the speed dimension reference unit data to obtain the noise power estimation values of the distance dimension and the speed dimensionAndtake a smaller valueAs an estimate of the noise power.
CFAR for clutter region
Respectively calculating the average value of distance dimension and speed dimension left and right (up and down) reference unit data, and taking the larger value as the distanceClutter power estimation in both the dimension and the velocity dimensionAndthen take the larger valueAs clutter power estimates.
Step h, estimating speed and distance parameters
And (5) carrying the constant false alarm detection result into the formula (4) and the formula (5) to obtain the speed and distance parameters.
About an angle parameter
The phase method angle measurement utilizes phase differences among echo signals received by a plurality of antennas to measure the angle.
As shown in fig. 8, assuming that there is a far zone object in the θ direction, the reflection by the object reaching the reception point is approximately a plane wave. Because the distance between the two antennas is d, the received signals generate phase difference due to the existence of the wave path difference Delta R
And measuring the phase difference to determine the target direction theta.
The phase method has good angle measurement performance and small calculation amount under the condition of high signal-to-noise ratio. However, in the case of low signal-to-noise ratio, the angle measurement performance is poor, and the angle information of more than two targets cannot be distinguished.
The basic principle of the spatial spectrum estimation method is that a spectral peak searching mode is adopted, and spatial steering vectors of different angles are used for carrying out beam forming on signals. And when the energy after beam forming is maximum, the angle corresponding to the guide vector is the angle estimation value of the target.
And according to the constant false alarm detection result, taking out a corresponding frequency spectrum complex vector in the two-dimensional FFT data, solving the covariance of the frequency spectrum complex vector, performing spectral peak search, and estimating a target angle.
Estimating the angle by adopting a spatial spectrum estimation method:
in the formula, the guide vectorSearching the maximum value of the module value according to a certain angle interval (determined by the angle measurement precision requirement), and calculating the corresponding angle.
The spatial spectrum estimation method has the advantages that under the condition of low signal-to-noise ratio, certain angle measurement performance can be kept, and meanwhile, angle information above two targets can be distinguished. But the amount of calculation is large compared to the phase comparison method.
Resolving velocity ambiguities for multiple PRFs
Considering the presence of a target in front of the radar with velocity v and doppler shift fdThe frequency of sweep repetition of the radar is fTWhen the doppler shift is greater than 1/T, there is ambiguity in the doppler frequency measurement according to the sampling theorem, and the actual doppler frequency can be expressed as follows:
in the formula,m is an integer for the apparent doppler shift.
For ambiguity resolution, radars usually employ multiple frequencies (f)T1,fT2,...,fTN) Working squareThe repeated frequency is selected to be relatively prime in a certain frequency unit, and the frequency is normalized, and the unambiguous Doppler frequency range is the least common multiple of the frequency
For actual Doppler shift of fdThe apparent doppler frequencies corresponding to different repetition frequencies are respectively:then there should be:
the specific speed ambiguity resolution step is as follows:
(1) obtaining the distance of the target according to the data 1And fuzzy speedThe unambiguous velocity measurement range is 0-Vu(the negative value is not considered temporarily), the system fuzzy speed measurement range is 0-VmaxThen the target possible speed is:
wherein,to round down.
According to vmCalculating to obtain a DFT twiddle factor:
(2) performing fast time dimension FFT on the data 2 to obtainAccording to the target distanceCalculating to obtain a unit of distance of the targetObtaining slow time complex vector of distance unit where target is located
(3) Calculating to obtain a target speed:
the sawtooth wave distance and speed measurement method based on the 77GHz millimeter wave radar is subjected to simulation test, and the detection errors of targets (single targets or multiple targets) are all kept at a quite low numerical level, including a target distance false detection rate, a target distance average error, a target speed false detection rate, a target speed average error, a target angle false detection rate, a target angle average error and the like. For example, in the case of a single target, the single target distance false detection rate is zero, the single target distance error is between 0.05m and 0.15m, the single target speed false detection rate is zero, and the single target speed error is between 0.04 and 0.08 m/s; under the condition of multiple targets, the distance error of the multiple targets is between 0.04 and 0.08m, and the speed error is between 0.04 and 0.08 m/s. In addition, in the case of multiple targets, the false alarm rate and the false alarm rate are substantially zero. Wherein, the false alarm rate is defined as follows: probability of detecting a false target. Defining the false alarm rate: probability that the preset target is not detected. And when the target distance error is larger than 1m or the speed error is larger than 1m/s or the angle error is larger than 2 degrees, the missing detection is determined.
It will be apparent to those skilled in the art that the above embodiments are merely illustrative of the present invention and are not to be construed as limiting the present invention, and that changes and modifications to the above described embodiments may be made within the spirit and scope of the present invention as defined in the appended claims.
Claims (6)
1. A sawtooth wave distance and speed measurement method based on a 77GHz millimeter wave radar is characterized by comprising the following steps:
a.Ntthe root transmitting antenna sequentially transmits the same frequency modulation continuous sawtooth wave transmitting signals to form a virtual array, and the plurality of transmitting antennas adopt different frequency sweep bandwidths and sawtooth wave numbers;
b.Nrthe receiving antennas receive the echo signals of the transmitting signals, and the echo signals of the transmitting signals under different transmitting days received by the same receiving antenna in a transmitting period are combined to formInto a virtual arrayWherein N iss＝fsT，Nsa1Is a transmission period;
c. carrying out windowing FFT on the received signal of each antenna along the fast time dimension in each transmission period to obtainNqFFTFast time dimension FFT points;
d. carrying out slow time dimension FFT on the received signals of different distance units of each receiving antenna to obtainNsFFTThe number of FFT points in the slow time dimension;
e. for YVFFEach distance-velocity unit of (1) is subjected to phase compensation to obtain
f. Performing beam forming on all the distance-velocity units to obtain
g. Performing Constant False Alarm Rate (CFAR) detection on the data subjected to beam forming to obtain a constant false alarm rate detection result; and
h. substituting the constant false alarm detection result into the following formula (4) and formula (5) to obtain the velocity v and the distance parameter r
<mrow> <msub> <mi>f</mi> <mrow> <mi>r</mi> <mo>,</mo> <mi>v</mi> </mrow> </msub> <mo>=</mo> <mfrac> <mrow> <mn>2</mn> <mi>&mu;</mi> <mi>r</mi> </mrow> <mi>c</mi> </mfrac> <mo>-</mo> <mfrac> <mrow> <mn>2</mn> <mi>v</mi> </mrow> <mi>c</mi> </mfrac> <msub> <mi>f</mi> <mn>0</mn> </msub> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>4</mn> <mo>)</mo> </mrow> </mrow>
<mrow> <msub> <mi>f</mi> <mi>v</mi> </msub> <mo>=</mo> <mo>-</mo> <mfrac> <mrow> <mn>2</mn> <mi>v</mi> </mrow> <mi>c</mi> </mfrac> <msub> <mi>f</mi> <mn>0</mn> </msub> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>5</mn> <mo>)</mo> </mrow> </mrow>
Wherein f is0And mu is the carrier center frequency, B/T is the sweep slope, B and T are the sweep bandwidth and the upper sweep period, respectively, and c is the propagation speed of the electromagnetic wave in the free space.
2. The method of claim 1, wherein in step a, the transmitting antenna for short-distance detection uses a high sweep bandwidth and the transmitting antenna for long-distance detection uses a small sweep bandwidth.
3. The method of claim 1, wherein in step f, for the close-range target signal, the two-dimensional FFT-processed distance-velocity unit signals of the receiving antenna are non-coherently accumulated to obtain an accumulation gain.
4. The method of claim 1 wherein in step g, the noise region and clutter region are detected using CFARs with different criteria.
5. The method of claim 1, wherein step h further comprises taking a measurement of an angular parameter.
6. The method of claim 1, wherein after step h, there is a velocity deblurring step, comprising a near-range velocity deblurring step and a far-range velocity deblurring step.
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