CN107783083B - Variable-period triangular wave and constant-frequency constant false alarm detection and data processing method - Google Patents
Variable-period triangular wave and constant-frequency constant false alarm detection and data processing method Download PDFInfo
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- CN107783083B CN107783083B CN201610728491.0A CN201610728491A CN107783083B CN 107783083 B CN107783083 B CN 107783083B CN 201610728491 A CN201610728491 A CN 201610728491A CN 107783083 B CN107783083 B CN 107783083B
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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
- 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
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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
- G01S13/06—Systems determining position data of a target
- G01S13/08—Systems for measuring distance only
- G01S13/32—Systems for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated
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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
- 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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Abstract
The method for detecting constant false alarm of variable-period triangular wave and constant-frequency system and processing data comprises the following steps of S1: d, removing direct current from time domain data of different antennas; s2: performing FFT (fast Fourier transform) on time domain data of different antennas, and performing frequency spectrum shift; s3: after the frequency spectrum is shifted, threshold detection is performed on data of one antenna, and the number of targets and position information of the targets in the frequency spectrum are recorded as S4: setting system parameters, namely system bandwidth B, working frequency f0, ranging range Rmin-Rmax, speed measuring range Vmin-Vmax, triangular wave period, triangular wave sampling rate fs and constant frequency wave sampling rate fs1, and FFT conversion point number N _ FFT; the distance value measured by the triangular wave with a smaller period is used as the distance of the measured target, and the speed measured by the constant frequency wave is used as the speed of the target, so that the distance resolution and the speed resolution of the system are optimal.
Description
Technical Field
The invention belongs to the field of constant false alarm detection and data processing, and particularly relates to a constant false alarm detection and data processing method with variable-period triangular waves and constant frequency.
Background
In modern radar signal processing, in order to improve the performance of the radar, the signal-to-noise ratio and the signal-to-interference ratio at the input end of a detector need to be improved, and the measures are to reduce the noise coefficient of a receiver and adopt various measures for suppressing clutter and resisting interference. Even with the above method, however, the detector input may still have residual components of noise, clutter and interference. Because the noise level inside the receiver slowly changes time due to the influence of analog devices, clutter and interference residuals are also time-varying and are distributed in a non-uniform space, various constant false alarm methods are still required to be adopted to ensure that the radar signal detection has the constant false alarm characteristic. The constant false alarm method is to use adaptive threshold to replace fixed threshold, and the adaptive threshold can be self-adaptively regulated according to the background noise, clutter and interference of detected point.
The existing constant false alarm detection algorithms are many, such as unit averaging, average selection of large, average selection of small, ordered statistics, clutter map method, etc., but they all have respective application ranges.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a constant false alarm detection and data processing method with variable-period triangular waves and constant-frequency systems, which can detect static and moving targets and measure angles of the static and moving targets. The static target angle measurement uses the upper frequency sweep frequency spectrum or the lower frequency sweep frequency spectrum of a plurality of antennas, the angle measurement is carried out on the constant frequency wave frequency spectrum obtained by a plurality of antennas for a moving target, the false alarm of the triangular wave angle measurement is higher for the moving target, the frequency spectrum is not as clean as the constant frequency, and therefore the angle measurement precision is effectively improved.
On one hand, the invention provides a method for detecting constant false alarm of variable-period triangular waves and constant-frequency systems and processing data, which comprises the following steps:
s1: d, removing direct current from time domain data of different antennas;
s2: performing FFT (fast Fourier transform) on time domain data of different antennas, and performing frequency spectrum shift;
s3: after the frequency spectrum is shifted, carrying out threshold detection on data of one antenna, and recording the number of targets and position information of the targets in the frequency spectrum;
s4: setting system parameters, namely system bandwidth B, working frequency f0, ranging range Rmin-Rmax, speed measuring range Vmin-Vmax, triangular wave period, triangular wave sampling rate fs and constant frequency wave sampling rate fs1, and FFT conversion point number N _ FFT;
and S5, carrying out target matching through the upper and lower sweep frequency parts of the triangular wave to obtain distance and speed information of a target, matching the distance and speed information with the target speed obtained by detection of the constant frequency wave part to obtain the required distance and speed of the target, and recording the position of the target in a frequency spectrum.
Further, the method further comprises:
s6, for the static target, according to the corresponding position of the target in the frequency spectrum of the frequency sweep on the triangular wave or the frequency sweep down part obtained in the step S5, and according to a phase comparison angle measurement, taking corresponding points of different antennas for angle measurement;
and for the moving target, according to the corresponding position of the target in the constant frequency wave part frequency spectrum obtained in the step S5, and according to the phase comparison angle measurement, taking the corresponding points of different antennas for angle measurement.
Further, the triangular wave has three periods, namely 2 × T1, 2 × T2 and 2 × T3.
Further, in the step S3, threshold detection is performed by using a method of detecting a cell average selected threshold, which specifically includes the following steps:
the first step, squaring the frequency spectrum after FFT to obtain power spectrum information;
secondly, setting system parameters: the method comprises the following steps of (1) calculating false alarm probability Pfa, lengths N _ qc and N _ hc of front and rear reference windows and length N _ pro of a protection window, calculating a minimum position kmin _ hp and a maximum position kmax _ hp corresponding to a constant frequency wave part detection point according to a speed measurement range, calculating minimum positions kmin _ up and kmin _ down and maximum positions kmax _ up and kmax _ down corresponding to a triangular wave part detection point according to a distance measurement and speed measurement range, and setting the light speed as c;
thirdly, judging whether the current detection point is greater than kmin and less than kmax for the constant frequency wave spectrum;
if the current detection point is not between kmin and kmax, no threshold detection is carried out;
if the current detection point is within kmin-kmax, averaging the data of the front window and the data of the rear window, then comparing, and selecting the data of the reference window with small average value to perform threshold detection;
multiplying the average value selected in the third step by a threshold factor to obtain a threshold value;
wherein, Bk is data in a selected reference window, L is the length of the reference window, β is a threshold factor, Pfa is the false alarm probability, and T _ mx is the calculated threshold value;
and fifthly, comparing the threshold value with the corresponding point of the power spectrum, and recording the positions and the number of the detection points exceeding the threshold.
Furthermore, the minimum detection point of the constant frequency wave in the second step is as follows:
kmin_hp＝N_FFT/2+Vmin*N_FFT*f0/(fs1*c)；
the maximum detection point positions are as follows:
kmax_hp＝N_FFT/2+Vmax*N_FFT*f0/(fs1*c)；
and respectively taking integer parts for kmin and kmax in the formula to obtain the required position number.
Furthermore, the period of the first triangular wave signal is 2 × T1, and the minimum detection point corresponding to the frequency sweep on the first triangular wave is:
kmin_up＝N_FFT/2-2*Rmax*B*N_FFT/(c*T1*fs)+2*f0*N_FFT*Vmin/(fs*c)
the maximum detection point position of the frequency sweep on the first triangular wave is as follows:
kmax_up＝N_FFT/2-2*Rmin*B*N_FFT/(c*T1*fs)+2*f0*N_FFT*Vmax/(fs*c)
the minimum detection point position of the frequency sweep under the first triangular wave is as follows:
kmin_down＝N_FFT/2+2*Rmin*B*N_FFT/(c*T1*fs)+2*f0*N_FFT*Vmin/(fs*c)
the maximum detection point position of the frequency sweep under the first triangular wave is as follows:
kmax_down＝N_FFT/2+2*Rmax*B*N_FFT/(c*T1*fs)+2*f0*N_FFT*Vmax/(fs*c)
and respectively carrying out rounding processing on the positions obtained above, and for the second triangular wave period 2 × T2 and the third triangular wave period 2 × T3, only changing the period T1 in the first triangular wave in the formula into T2 or T3 to obtain the maximum and minimum detection point positions corresponding to the up-down frequency sweep of the second and third triangular waves.
Further, the target pairing and data processing steps are as follows:
a: setting currently required system parameters according to the target number and the position information;
V_fb＝c*fs/(4*N_FFT*f0)
V_fb 1＝c*fs1/(2*N_FFT*f0)
R_fb 1＝c*T1*fs/(4*N_FFT*B)
R_fb 2＝c*T2*fs/(4*N_FFT*B)
R_fb 3＝c*T3*fs/(4*N_FFT*B)
k1min＝floor(R_min/R_fb1)
k1max＝floor(R_max/R_fb1)
k2min＝floor(R_min/R_fb2)
k2max＝floor(R_max/R_fb2)
k3min＝floor(R_min/R_fb3)
k3max＝floor(R_max/R_fb3)
wherein, V _ fb is the velocity resolution of the constant frequency wave part, V _ fb1 is the velocity resolution of the triangular wave part, and R _ fb1, R _ fb2 and R _ fb3 are the distance resolution of the triangular wave part, and k1min, k1max, k2min, k2max, k3min and k3max are the points corresponding to the maximum distance measurement and the minimum distance measurement of the three variable-period triangular wave respectively; wherein floor is an integer function;
b: performing displacement processing according to the position information obtained by the constant frequency wave part, calculating speed information to ensure that the speed corresponding to the object approaching is positive and the speed corresponding to the object far away is negative, and recording corresponding frequency spectrum position information;
c: the position difference of the same target in the up-down frequency sweeping is obtained according to the speed information V _ hp obtained by the position calculation of the constant frequency wave detection point, the sampling rate fs of the triangular wave and the FFT conversion point number:
k_wzc＝V_hp*4*f0*N_FFT/(c*fs)；
d: b, solving all targets with the upper and lower sweep frequency positions less than or equal to N according to the triangular wave frequency spectrum processed in the step B to obtain all possible distance and speed information of the static target;
resolving according to the difference in the step C and the triangular wave frequency spectrum processed in the step B to obtain all possible distance and speed information of the moving target, and recording corresponding frequency spectrum position information;
e: d, judging static target information obtained by resolving three triangular wave periods in the step D, and for a certain undetermined target, if the absolute value of R10-R30 is smaller than R _ cz13 and the absolute value of R20-R30 is smaller than R _ cz23, the static target at the distance of R30 is an effective target, and recording the position information of the upper and lower sweep frequency detection points of the triangular wave in the frequency spectrum, otherwise, the static target is a false target;
d, judging the moving target information obtained by periodically resolving three triangular waves in the step D, wherein the speed measured by the constant frequency wave part is V _ hp, and if the measured target meets the following conditions:
|V_hp-V1|≤V_cz1
|V_hp-V2|≤V_cz2
|V_hp-V3|≤V_cz3
|R1-R3|≤R_cz1
|R2-R3|≤R_cz2
the moving target is valid, the distance is R3, the speed is V _ hp, the position information of the detection point in the constant frequency wave frequency spectrum is recorded, and otherwise, the moving target is considered as a false target;
f: deleting the targets with the same distance and speed of the static target and the moving target obtained in the step E, finally obtaining the required target information, recording the corresponding frequency spectrum position information,
further, in step B, if k _ wz _ hp is the position number of the detection point before shifting the constant frequency spectrum, k _ wzyw _ hp is the position number of the detection point after shifting the constant frequency spectrum, and FFT transform point number is N _ FFT, then
k_wzyw_hp＝k_wz_hp-N_FFT/2-1
The speed is then:
V_hp＝k_wzyw_hp*fs1*c/(2*N_FFT*f0))
processing the position information of the frequency sweeping part on the triangular wave, so that for a static target, the frequency spectrum positions of the upper frequency sweeping and the lower frequency sweeping are both positioned on the same half axis of the frequency spectrum, and recording the corresponding frequency spectrum position information, wherein the specific processing is as follows:
assuming that k _ wz _ up1 is the position number of the detection point before the shift of the first triangular wave spectrum, and k _ wzyw _ up1 is the position number of the detection point after the shift of the first triangular wave spectrum, k _ wzyw _ up1 is N _ FFT-k _ wz _ up1-1
The position numbers k _ wzyw _ up2 and k _ wzyw _ up3 after the shift of the second and third triangular wave spectrums can be obtained by the same method.
As a further step, the stationary target in step D is solved as follows:
assuming that the position of the upper sweep detection point of the first triangular wave is k _ wzyw _ up1 and the position of the lower sweep detection point is k _ wz _ down1, if k _ wzyw _ up1 and k _ wz _ down1 satisfy the following conditions:
|k_wz_down1-k_wzyw_up1|≤1
k_wz_down1+k_wzyw_up1≥N_FFT+2+k1min
k_wz_down1+k_wzyw_up1≤N_FFT+2+k1max
the target is a stationary target, and similarly, the stationary target can be measured by the second and third triangular waves, and the distance measured in the first period is R10, the distance measured in the second period is R20, and the distance measured in the third triangular wave is R30;
the moving object is solved as follows:
according to the position difference k _ wzc between the upper and lower frequency sweeps in the triangular wave, the position k _ wzyw _ up1 of the upper frequency sweep detection point on the first triangular wave and the position k _ wz _ down1 of the lower frequency sweep detection point satisfy the following conditions:
|k_wz_down1-k_wzyw_up1+k_wzc|≤1
k_wz_down1+k_wzyw_up1≥N_FFT+2+k1min
k_wz_down1+k_wzyw_up1≤N_FFT+2+k1max
the target is a moving target, and similarly, the moving target can be measured by the second and third triangular waves, the distance measured in the first period is R1, and the speed is V1; the distance measured in the second cycle is R2, speed V2; the third triangle wave measures distance R3, velocity V3.
As a further step, the phase ratio measurement angles in step S6 are:
setting an antenna spacing d _ jsjss and a working wavelength lambda, wherein one antenna signal frequency spectrum is sig _ fft1, the other signal frequency spectrum is sig _ fft2, and determining the positions k1 and k2 of the frequency spectrum of the target;
the tangent value xw1 of the signal phase at the position k1 in the frequency domain signal sig _ fft1 and the tangent value xw2 of the phase at the position k2 in the sig _ fft2 are respectively obtained:
xw1＝imag(sig_fft1(k1))/real(sig_fft1(k1))
xw2＝imag(sig_fft2(k2))/real(sig_fft1(k2))
the tangent of its phase difference value
xwc＝(xw1-xw2)/(1+xw1*xw2)
The camber value of the phase difference xwc _ rad is
xwc_rad＝atan(xwc)
The measured angle jd _ cs ═ asin (xwc _ rad ×/(2 × π × d _ jsjss)) × 180/π
Where λ c/f0, c 3.0 x 108m/s, and f0 is the center frequency of the radar.
Due to the adoption of the technical scheme, the invention can obtain the following technical effects:
1. the average selection of the utilization units is small, and the detection probability is high;
2. the defect of high false alarm rate caused by small average selection of units is effectively overcome by three triangular waves with different periods and a constant frequency modulation mode; so that the detection probability of the target is as high as possible and the false alarm probability is as low as possible.
3. The threshold detection is carried out on the effective frequency spectrum range by using the system parameters, so that the operation amount is effectively reduced.
4. The distance value measured by the triangular wave with a smaller period is used as the distance of the measured target, and the speed measured by the constant frequency wave is used as the speed of the target, so that the distance resolution and the speed resolution of the system are optimal.
5. Stationary and moving objects may be detected and angle-measured. The static target angle measurement uses the upper frequency sweep frequency spectrum or the lower frequency sweep frequency spectrum of a plurality of antennas, the angle measurement is carried out on the constant frequency wave frequency spectrum obtained by a plurality of antennas for a moving target, the false alarm of the triangular wave angle measurement is higher for the moving target, the frequency spectrum is not as clean as the constant frequency, and therefore the angle measurement precision is effectively improved.
Drawings
The invention has the following figures 3:
FIG. 1 is a flowchart of the entire data processing in example 1;
FIG. 2 is a flowchart of a method for detecting the average gating threshold of the unit in embodiment 2;
FIG. 3 is a flowchart of target pairing according to example 3.
Detailed Description
The technical solution of the present invention is further specifically described below by way of examples with reference to the accompanying drawings.
Example 1
On one hand, the invention provides a method for detecting constant false alarm of variable-period triangular waves and constant-frequency systems and processing data, which comprises the following steps:
s1: removing direct current from the time domain data of the antenna 1 and the antenna 2, namely subtracting a constant direct current value;
s2: the time domain data of the antenna 1 and the antenna 2 are subjected to FFT (fast Fourier transform) conversion and frequency spectrum shift, so that the cell average selection small threshold detection is convenient to carry out in the later stage, and the advantage of adopting the frequency spectrum shift is that targets can be contained in reference windows before and after a detection point as far as possible, and the threshold estimation value is more accurate;
s3: after the frequency spectrum is shifted, threshold detection is carried out on data of one antenna, and the number of targets and position information of the targets in the frequency spectrum are recorded: the constant frequency part k _ wz _ hp, the first triangular wave up-sweep frequency k _ wz _ up1, the first triangular wave down-sweep frequency k _ wz _ down1, the second triangular wave up-sweep frequency k _ wz _ up2, the second triangular wave down-sweep frequency k _ wz _ down2, the third triangular wave up-sweep frequency k _ wz _ up3 and the third triangular wave down-sweep frequency k _ wz _ down 3;
s4: setting system parameters, system bandwidth B; operating frequency f 0; the range of distance measurement Rmin-Rmax; the velocity measurement range is Vmin-Vmax; the triangular waves are three, and the periods of the three triangular waves are 2 × T1, 2 × T2 and 2 × T3 respectively; the sampling rate fs of the triangular wave, the sampling rate fs1 of the constant frequency wave and the number of FFT conversion points N _ FFT;
s5, carrying out target matching through the upper and lower sweep frequency parts of the triangular wave to obtain distance and speed information of a target, matching the distance and speed information with the target speed obtained by detection of the constant frequency wave part to obtain the required distance and speed of the target, and recording the position of the target in a frequency spectrum;
s6, for the static target, according to the corresponding position of the target in the frequency spectrum of the frequency sweep on the triangular wave or the frequency sweep down part obtained in the step S5, and according to a phase comparison angle measurement, taking corresponding points of different antennas for angle measurement;
and for the moving target, according to the corresponding position of the target in the constant frequency wave part frequency spectrum obtained in the step S5, and according to the phase comparison angle measurement, taking the corresponding points of different antennas for angle measurement.
The number of the antennas may be multiple, and only two antennas are illustrated in this embodiment.
Example 2
In this embodiment, the embodiment 1 is further limited, and the threshold detection in step S3 adopts a method of detecting a cell average selected small threshold, which includes the following specific steps:
the first step, squaring the frequency spectrum after FFT to obtain power spectrum information;
secondly, setting system parameters: the method comprises the following steps of (1) calculating false alarm probability Pfa, lengths N _ qc and N _ hc of front and rear reference windows and length N _ pro of a protection window, calculating a minimum position kmin _ hp and a maximum position kmax _ hp corresponding to a constant frequency wave part detection point according to a speed measurement range, calculating minimum positions kmin _ up and kmin _ down and maximum positions kmax _ up and kmax _ down corresponding to a triangular wave part detection point according to a distance measurement and speed measurement range, and setting the light speed as c;
the minimum detection point position of the constant frequency wave is as follows:
kmin_hp＝N_FFT/2+Vmin*N_FFT*f0/(fs1*c)；
the maximum detection point positions are as follows:
kmax_hp＝N_FFT/2+Vmax*N_FFT*f0/(fs1*c)；
respectively taking integer parts for kmin and kmax in the formula to obtain the required position number;
the first triangular wave signal period is 2 × T1, and the minimum detection point position corresponding to the frequency sweep on the first triangular wave is:
kmin_up＝N_FFT/2-2*Rmax*B*N_FFT/(c*T1*fs)+2*f0*N_FFT*Vmin/(fs*c)
the maximum detection point position of the frequency sweep on the first triangular wave is as follows:
kmax_up＝N_FFT/2-2*Rmin*B*N_FFT/(c*T1*fs)+2*f0*N_FFT*Vmax/(fs*c)
the minimum detection point position of the frequency sweep under the first triangular wave is as follows:
kmin_down＝N_FFT/2+2*Rmin*B*N_FFT/(c*T1*fs)+2*f0*N_FFT*Vmin/(fs*c)
the maximum detection point position of the frequency sweep under the first triangular wave is as follows:
kmax_down＝N_FFT/2+2*Rmax*B*N_FFT/(c*T1*fs)+2*f0*N_FFT*Vmax/(fs*c)
respectively carrying out rounding processing on the obtained positions, and for the second triangular wave period 2 × T2 and the third triangular wave period 2 × T3, only changing the period T1 in the first triangular wave in the formula into T2 or T3 to obtain the maximum and minimum detection point positions corresponding to the up-down frequency sweep of the second and third triangular waves;
thirdly, judging whether the current detection point is greater than kmin and less than kmax for the constant frequency wave spectrum;
if the current detection point is not between kmin and kmax, no threshold detection is carried out;
if the current detection point is within kmin-kmax, averaging the data of the front window and the data of the rear window, then comparing, and selecting the data of the reference window with small average value to perform threshold detection;
multiplying the average value selected in the third step by a threshold factor to obtain a threshold value;
wherein, Bk is data in a selected reference window, L is the length of the reference window, β is a threshold factor, Pfa is the false alarm probability, and T _ mx is the calculated threshold value;
and fifthly, comparing the threshold value with the corresponding point of the power spectrum, and recording the positions and the number of the detection points exceeding the threshold.
Example 3
The complementary target pairing and data processing steps as in example 1 or 2 are as follows:
a: setting currently required system parameters according to the target number and the position information;
V_fb＝c*fs/(4*N_FFT*f0)
V_fb 1＝c*fs1/(2*N_FFT*f0)
R_fb 1＝c*T1*fs/(4*N_FFT*B)
R_fb 2＝c*T2*fs/(4*N_FFT*B)
R_fb 3＝c*T3*fs/(4*N_FFT*B)
k1min＝floor(R_min/R_fb1)
k1max＝floor(R_max/R_fb1)
k2min＝floor(R_min/R_fb2)
k2max＝floor(R_max/R_fb2)
k3min＝floor(R_min/R_fb3)
k3max＝floor(R_max/R_fb3)
wherein, V _ fb is the velocity resolution of the constant frequency wave part, V _ fb1 is the velocity resolution of the triangular wave part, R _ fb1, R _ fb2 and R _ fb3 are the distance resolution of the triangular wave part, and k1min, k1max, k2min, k2max, k3min and k3max are the points corresponding to the maximum distance measurement and the minimum distance measurement of the three variable-period triangular wave respectively; wherein floor is an integer function;
b: performing displacement processing according to the position information obtained by the constant frequency wave part, calculating speed information to ensure that the speed corresponding to the object approaching is positive and the speed corresponding to the object far away is negative, and recording corresponding frequency spectrum position information;
let k _ wz _ hp be the position number of the detection point before shifting the constant frequency wave spectrum, k _ wzyw _ hp be the position number of the detection point after shifting the constant frequency wave spectrum, and the FFT transform point number be N _ FFT, then
k_wzyw_hp＝k_wz_hp-N_FFT/2-1
The speed is then:
V_hp＝k_wzyw_hp*fs1*c/(2*N_FFT*f0))
processing the position information of the frequency sweeping part on the triangular wave, so that for a static target, the frequency spectrum positions of the upper frequency sweeping and the lower frequency sweeping are both positioned on the same half shaft of the frequency spectrum, namely a front half shaft or a rear half shaft, and recording the corresponding frequency spectrum position information, wherein the specific processing is as follows:
let k _ wz _ up1 be the position number of the detection point before the shift of the first triangular wave spectrum, and k _ wzyw _ up1 be the position number of the detection point after the shift of the first triangular wave spectrum, then
k_wzyw_up1＝N_FFT-k_wz_up1-1
Similarly, the position numbers k _ wzyw _ up2 and k _ wzyw _ up3 of the shifted second and third triangular wave spectrums can be obtained;
c: the position difference of the same target in the up-down frequency sweeping is obtained according to the speed information V _ hp obtained by the position calculation of the constant frequency wave detection point, the sampling rate fs of the triangular wave and the FFT conversion point number:
k_wzc＝V_hp*4*f0*N_FFT/(c*fs)；
d: b, solving all targets with the upper and lower sweep frequency positions less than or equal to 1 according to the triangular wave frequency spectrum processed in the step B to obtain all possible distance and speed information of the static target; the speed information is small and can be regarded as static, namely the speed is 0, and the corresponding frequency spectrum position information is recorded, and the static target is calculated as follows:
assuming that the position of the upper sweep detection point of the first triangular wave is k _ wzyw _ up1 and the position of the lower sweep detection point is k _ wz _ down1, if k _ wzyw _ up1 and k _ wz _ down1 satisfy the following conditions:
|k_wz_down1-k_wzyw_up1|≤1
k_wz_down1+k_wzyw_up1≥N_FFT+2+k1min
k_wz_down1+k_wzyw_up1≤N_FFT+2+k1max
the target is a stationary target, and similarly, the stationary target can be measured by the second and third triangular waves, and the distance measured in the first period is R10, the distance measured in the second period is R20, and the distance measured in the third triangular wave is R30;
resolving according to the difference in the step C and the triangular wave frequency spectrum processed in the step B to obtain all possible distance and speed information of the moving target, and recording corresponding frequency spectrum position information;
the moving object is solved as follows:
according to the position difference k _ wzc between the upper and lower frequency sweeps in the triangular wave, the position k _ wzyw _ up1 of the upper frequency sweep detection point on the first triangular wave and the position k _ wz _ down1 of the lower frequency sweep detection point satisfy the following conditions:
|k_wz_down1-k_wzyw_up1+k_wzc|≤1
k_wz_down1+k_wzyw_up1≥N_FFT+2+k1min
k_wz_down1+k_wzyw_up1≤N_FFT+2+k1max
the target is a moving target, and similarly, the moving target can be measured by the second and third triangular waves, the distance measured in the first period is R1, and the speed is V1; the distance measured in the second cycle is R2, speed V2; the third triangle wave measures distance R3, velocity V3.
E: judging static target information obtained by resolving three triangular wave periods in the step D, if an absolute value of R10-R30 is smaller than R _ cz13 and an absolute value of R20-R30 is smaller than R _ cz23, regarding a certain target to be determined, the static target at the distance of R30 is an effective target, and recording position information of upper and lower sweep frequency detection points of the triangular wave in a frequency spectrum, otherwise, the target is a false target, wherein the R _ cz13 is 4m, and the R _ cz23 is 4m, and the value can be modified and limited according to actual conditions;
d, judging the moving target information obtained by periodically resolving three triangular waves in the step D, wherein the speed measured by the constant frequency wave part is V _ hp, and if the measured target meets the following conditions:
|V_hp-V1|≤V_cz1
|V_hp-V2|≤V_cz2
|V_hp-V3|≤V_cz3
|R1-R3|≤R_cz1
|R2-R3|≤R_cz2
the moving target is valid, the distance is R3, the speed is V _ hp, the position information of the detection point in the constant frequency wave frequency spectrum is recorded, and otherwise, the moving target is considered as a false target;
f: and E, deleting the targets with the same distance and speed as the static targets and the moving targets obtained in the step E, finally obtaining the required target information, and recording the corresponding frequency spectrum position information, wherein the deleting method of the same targets comprises the following steps:
the static targets and the moving targets can be firstly sorted from small to large according to the speed, the corresponding frequency spectrum position information is updated, then sorted from small to large according to the distance, the corresponding frequency spectrum position information is recorded, then the distance speed information of the current target and the distance speed information of the previous target are respectively judged, if the current target and the previous target are the same, the current target is deleted, the next target is continuously judged, and if the current target and the previous target are different, the current target and the previous target are judged to be an effective target.
Example 4
As a supplement to examples 1 or 2 or 3: the phase angle measurement process in step S6 is: setting an antenna spacing d _ jsjss, wherein the working wavelength is lambda, one antenna signal spectrum is sig _ fft1, the other signal spectrum is sig _ fft2, the position corresponding to the receiving antenna 1 is k1, and the position corresponding to the receiving antenna 2 is k 2;
the tangent value xw1 of the signal phase at the position k1 in the frequency domain signal sig _ fft1 and the tangent value xw2 of the phase at the position k2 in the sig _ fft2 are respectively obtained:
xw1＝imag(sig_fft1(k1))/real(sig_fft1(k1))
xw2＝imag(sig_fft2(k2))/real(sig_fft1(k2))
the tangent of its phase difference value
xwc＝(xw1-xw2)/(1+xw1*xw2)
The camber value of the phase difference xwc _ rad is
xwc_rad＝atan(xwc)
The measured angle jd _ cs ═ asin (xwc _ rad ×/(2 × π × d _ jsjss)) × 180/π
Where λ c/f0, c 3.0 x 108m/s, and f0 is the center frequency of the radar, and the angular position can be obtained.
According to the method and the device, the threshold detection is carried out on the effective frequency spectrum range by using the system parameters, so that the operation amount is effectively reduced. The corresponding position difference information of the speed value measured by the constant frequency wave in the triangular wave frequency spectrum is matched with the speed measured by the triangular wave, the position sum of the upper and lower sweep frequency detection points of the triangular wave is limited by the positions of the minimum and maximum detection points, and the calculation amount is effectively reduced.
The distance value measured by the triangular wave with a smaller period is used as the distance of the measured target, and the speed measured by the constant frequency wave is used as the speed of the target, so that the distance resolution and the speed resolution of the system are optimal. Stationary and moving objects may be detected and angle-measured. The static target angle measurement uses the upper frequency sweep frequency spectrum or the lower frequency sweep frequency spectrum of the two antennas, the angle measurement is carried out on the constant frequency wave frequency spectrum obtained by the two antennas for the moving target, the false alarm of the triangular wave angle measurement is higher for the moving target, the frequency spectrum is not as clean as the constant frequency, and therefore the angle measurement precision is effectively improved. For the combination of the same or similar targets in the target matching, firstly, sequencing the static targets and the moving targets from small to large according to the speed, updating the corresponding frequency spectrum position information, then sequencing from small to large according to the distance, recording the corresponding frequency spectrum position information, then respectively judging the distance speed information of the current target and the distance speed information of the previous target, if the current target and the moving targets are the same, deleting the current target, continuing to judge the next target, and if the current target and the moving targets are different, judging the current target and the moving target to be an effective target.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be able to cover the technical solutions and the inventive concepts of the present invention within the technical scope of the present invention.
Claims (6)
1. The constant false alarm detection and data processing method of the variable-period triangular wave and constant-frequency system is characterized by comprising the following steps of:
s1: d, removing direct current from time domain data of different antennas;
s2: performing FFT (fast Fourier transform) on time domain data of different antennas, and performing frequency spectrum shift;
s3: after the frequency spectrum is shifted, carrying out threshold detection on data of one antenna, and recording the number of targets and position information of the targets in the frequency spectrum;
s4: setting system parameters, namely system bandwidth B, working frequency f0, ranging range Rmin-Rmax, speed measuring range Vmin-Vmax, triangular wave period, triangular wave sampling rate fs and constant frequency wave sampling rate fs1, and FFT conversion point number N _ FFT;
s5, carrying out target matching through the upper and lower sweep frequency parts of the triangular wave to obtain distance and speed information of a target, matching the distance and speed information with the target speed obtained by detection of the constant frequency wave part to obtain the required distance and speed of the target, and recording the position of the target in a frequency spectrum;
s6, for the static target, according to the corresponding position of the target in the frequency spectrum of the frequency sweep on the triangular wave or the frequency sweep down part obtained in the step S5, and according to a phase comparison angle measurement, taking corresponding points of different antennas for angle measurement;
for the moving target, according to the corresponding position of the target in the constant frequency wave partial frequency spectrum obtained in the step S5 and according to the phase comparison angle measurement, taking the corresponding points of different antennas for angle measurement;
the triangular waves are three, and the periods of the three triangular waves are 2 × T1, 2 × T2 and 2 × T3 respectively;
in the step S3, threshold detection is performed by using a method of cell average selection threshold detection, and the method specifically includes the following steps:
the first step, squaring the frequency spectrum after FFT to obtain power spectrum information;
secondly, setting system parameters: the method comprises the following steps of (1) calculating false alarm probability Pfa, lengths N _ qc and N _ hc of front and rear reference windows and length N _ pro of a protection window, calculating a minimum position kmin _ hp and a maximum position kmax _ hp corresponding to a constant frequency wave part detection point according to a speed measurement range, calculating minimum positions kmin _ up and kmin _ down and maximum positions kmax _ up and kmax _ down corresponding to a triangular wave part detection point according to a distance measurement and speed measurement range, and setting the light speed as c;
thirdly, judging whether the current detection point is greater than kmin and less than kmax for the constant frequency wave spectrum;
if the current detection point is not between kmin and kmax, no threshold detection is carried out;
if the current detection point is within kmin-kmax, averaging the data of the front window and the data of the rear window, then comparing, and selecting the data of the reference window with small average value to perform threshold detection;
multiplying the average value selected in the third step by a threshold factor to obtain a threshold value;
wherein, Bk is data in a selected reference window, L is the length of the reference window, β is a threshold factor, Pfa is the false alarm probability, and T _ mx is the calculated threshold value;
comparing the threshold value with the corresponding point of the power spectrum, and recording the positions and the number of the detection points exceeding the threshold;
the minimum detection point position of the constant frequency wave in the second step is as follows:
kmin_hp＝N_FFT/2+Vmin*N_FFT*f0/(fs1*c)；
the maximum detection point positions are as follows:
kmax_hp＝N_FFT/2+Vmax*N_FFT*f0/(fs1*c)；
and respectively taking integer parts for kmin and kmax in the formula to obtain the required position number.
2. The method according to claim 1, wherein the first triangular wave signal period in the second step is 2 × T1,
the minimum detection point position corresponding to the frequency sweep on the first triangular wave is as follows:
kmin_up＝N_FFT/2-2*Rmax*B*N_FFT/(c*T1*fs)+2*f0*N_FFT*Vmin/(fs*c)
the maximum detection point position of the frequency sweep on the first triangular wave is as follows:
kmax_up＝N_FFT/2-2*Rmin*B*N_FFT/(c*T1*fs)+2*f0*N_FFT*Vmax/(fs*c)
the minimum detection point position of the frequency sweep under the first triangular wave is as follows:
kmin_down＝N_FFT/2+2*Rmin*B*N_FFT/(c*T1*fs)+2*f0*N_FFT*Vmin/(fs*c)
the maximum detection point position of the frequency sweep under the first triangular wave is as follows:
kmax_down＝N_FFT/2+2*Rmax*B*N_FFT/(c*T1*fs)+2*f0*N_FFT*Vmax/(fs*c)
and respectively carrying out rounding processing on the positions obtained above, and for the second triangular wave period 2 × T2 and the third triangular wave period 2 × T3, only changing the period T1 in the first triangular wave in the formula into T2 or T3 to obtain the maximum and minimum detection point positions corresponding to the up-down frequency sweep of the second and third triangular waves.
3. The method for detecting constant false alarm rate of variable-period triangular wave and constant-frequency system according to claim 1, wherein the target matching and data processing steps are as follows:
a: setting currently required system parameters according to the target number and the position information;
V_fb＝c*fs/(4*N_FFT*f0)
V_fb 1＝c*fs1/(2*N_FFT*f0)
R_fb 1＝c*T1*fs/(4*N_FFT*B)
R_fb 2＝c*T2*fs/(4*N_FFT*B)
R_fb 3＝c*T3*fs/(4*N_FFT*B)
k1min＝floor(R_min/R_fb1)
k1max＝floor(R_max/R_fb1)
k2min＝floor(R_min/R_fb2)
k2max＝floor(R_max/R_fb2)
k3min＝floor(R_min/R_fb3)
k3max＝floor(R_max/R_fb3)
wherein, V _ fb is the velocity resolution of the constant frequency wave part, V _ fb1 is the velocity resolution of the triangular wave part, and R _ fb1, R _ fb2 and R _ fb3 are the distance resolution of the triangular wave part, and k1min, k1max, k2min, k2max, k3min and k3max are the points corresponding to the maximum distance measurement and the minimum distance measurement of the three variable-period triangular wave respectively; wherein floor is an integer function;
b: performing displacement processing according to the position information obtained by the constant frequency wave part, calculating speed information to ensure that the speed corresponding to the object approaching is positive and the speed corresponding to the object far away is negative, and recording corresponding frequency spectrum position information;
c: the position difference of the same target in the up-down frequency sweeping is obtained according to the speed information V _ hp obtained by the position calculation of the constant frequency wave detection point, the sampling rate fs of the triangular wave and the FFT conversion point number:
k_wzc＝V_hp*4*f0*N_FFT/(c*fs)；
d: b, solving all targets with the upper and lower sweep frequency positions less than or equal to N according to the triangular wave frequency spectrum processed in the step B to obtain all possible distance and speed information of the static target;
resolving according to the position difference in the step C and the triangular wave frequency spectrum processed in the step B to obtain all possible distance and speed information of the moving target, and recording corresponding frequency spectrum position information;
e: d, judging static target information obtained by resolving three triangular wave periods in the step D, and for a certain undetermined target, if the absolute value of R10-R30 is smaller than R _ cz13 and the absolute value of R20-R30 is smaller than R _ cz23, the static target at the distance of R30 is an effective target, and recording the position information of the upper and lower sweep frequency detection points of the triangular wave in the frequency spectrum, otherwise, the static target is a false target;
d, judging the moving target information obtained by periodically resolving three triangular waves in the step D, wherein the speed measured by the constant frequency wave part is V _ hp, and if the measured target meets the following conditions:
|V_hp-V1|≤V_cz1
|V_hp-V2|≤V_cz2
|V_hp-V3|≤V_cz3
|R1-R3|≤R_cz1
|R2-R3|≤R_cz2
the moving target is valid, the distance is R3, the speed is V _ hp, the position information of the detection point in the constant frequency wave frequency spectrum is recorded, and otherwise, the moving target is considered as a false target;
f: and E, deleting the targets with the same distance and speed of the static target and the moving target obtained in the step E, finally obtaining the required target information, and recording the corresponding frequency spectrum position information.
4. The method according to claim 3, wherein in step B, k _ wz _ hp is the position number of the detection point before the frequency spectrum shift of the constant frequency wave, k _ wzyw _ hp is the position number of the detection point after the frequency spectrum shift of the constant frequency wave, and FFT transform point is N _ FFT, then
k_wzyw_hp＝k_wz_hp-N_FFT/2-1
The speed is then:
V_hp＝k_wzyw_hp*fs1*c/(2*N_FFT*f0))
processing the position information of the frequency sweeping part on the triangular wave, so that for a static target, the frequency spectrum positions of the upper frequency sweeping and the lower frequency sweeping are both positioned on the same half axis of the frequency spectrum, and recording the corresponding frequency spectrum position information, wherein the specific processing is as follows:
let k _ wz _ up1 be the position number of the detection point before the shift of the first triangular wave spectrum, and k _ wzyw _ up1 be the position number of the detection point after the shift of the first triangular wave spectrum, then
k_wzyw_up1＝N_FFT-k_wz_up1-1
The position numbers k _ wzyw _ up2 and k _ wzyw _ up3 after the shift of the second and third triangular wave spectrums can be obtained by the same method.
5. The method for detecting constant false alarm rate of variable-period triangular wave and constant-frequency system according to claim 3, wherein the stationary target in step D is calculated as follows:
assuming that the position of the upper sweep detection point of the first triangular wave is k _ wzyw _ up1 and the position of the lower sweep detection point is k _ wz _ down1, if k _ wzyw _ up1 and k _ wz _ down1 satisfy the following conditions:
|k_wz_down1-k_wzyw_up1|≤1
k_wz_down1+k_wzyw_up1≥N_FFT+2+k1min
k_wz_down1+k_wzyw_up1≤N_FFT+2+k1max
the target is a stationary target, and similarly, the stationary target can be measured by the second and third triangular waves, and the distance measured in the first period is R10, the distance measured in the second period is R20, and the distance measured in the third triangular wave is R30;
the moving object is solved as follows:
according to the position difference k _ wzc between the upper and lower frequency sweeps in the triangular wave, the position k _ wzyw _ up1 of the upper frequency sweep detection point on the first triangular wave and the position k _ wz _ down1 of the lower frequency sweep detection point satisfy the following conditions:
|k_wz_down1-k_wzyw_up1+k_wzc|≤1
k_wz_down1+k_wzyw_up1≥N_FFT+2+k1min
k_wz_down1+k_wzyw_up1≤N_FFT+2+k1max
the target is a moving target, and similarly, the moving target can be measured by the second and third triangular waves, the distance measured in the first period is R1, and the speed is V1; the distance measured in the second cycle is R2, speed V2; the third triangle wave measures distance R3, velocity V3.
6. The method for detecting constant false alarm rate with variable-period triangular wave and constant-frequency system according to claim 1, wherein the phase ratio measurement angles in step S6 are:
setting an antenna spacing d _ jsjss and a working wavelength lambda, wherein one antenna signal frequency spectrum is sig _ fft1, the other signal frequency spectrum is sig _ fft2, and determining the positions k1 and k2 of the frequency spectrum of the target; the tangent value xw1 of the signal phase at the position k1 in the frequency domain signal sig _ fft1 and the tangent value xw2 of the phase at the position k2 in the sig _ fft2 are respectively obtained:
xw1＝imag(sig_fft1(k1))/real(sig_fft1(k1))
xw2＝imag(sig_fft2(k2))/real(sig_fft1(k2))
the tangent of its phase difference value
xwc＝(xw1-xw2)/(1+xw1*xw2)
The camber value of the phase difference xwc _ rad is
xwc_rad＝a tan(xwc)
The measured angle jd _ cs ═ asin (xwc _ rad ×/(2 × π × d _ jsjss)) × 180/π
Where λ c/f0, c 3.0 x 108m/s, and f0 is the center frequency of the radar.
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