CN111913161A - Method for improving NLFM waveform radar target angle measurement precision - Google Patents
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Abstract
The invention discloses a method for improving the target angle measurement precision of an NLFM (non line of sight) waveform radar, which comprises the following steps: performing first pulse compression processing on the radar target echo signal to obtain a first pulse pressure echo signal; performing beam forming processing on the first pulse pressure echo signal to obtain a beam forming result; performing Doppler frequency shift processing on the beam forming result by using a Doppler filter to obtain a Doppler frequency estimated value; performing second pulse compression processing on the radar target echo signal according to the Doppler estimated value to obtain a second pulse pressure echo signal; and performing sum-difference beam phase comparison single pulse angle measurement on the second pulse pressure echo signal to obtain a radar target angle measurement. According to the method for improving the angle measurement precision of the NLFM waveform radar target, the Doppler frequency estimation of the radar target echo signal is utilized to design a completely matched pulse response filter, the pulse compression processing of the radar target echo signal is carried out, the loss of the signal-to-noise ratio of angle estimation data is reduced, and therefore the angle measurement precision is improved and the performance is stable.
Description
Technical Field
The invention belongs to the technical field of radar signal processing, and particularly relates to a method for improving the angle measurement precision of an NLFM (non line of sight) waveform radar target.
Background
Non-Linear Frequency Modulation (NLFM) signals can be directly matched and filtered without windowing, main lobe broadening and loss of signal-to-noise ratio caused by windowing are avoided, and general attention is paid to the radar field in recent years.
The target angle measurement precision of the radar is influenced by parameters, an estimation method and an antenna aperture of the system, and is inseparable from the signal-to-noise ratio of a target. Therefore, if the angle measurement precision is to be improved, the method can be completed by improving the signal to noise ratio. Zhaoyangbo et al, "a single pulse angle measurement method under a multiple target condition [ A ]. West Ann university of electronic technology, 2005,32 (3): 383-386, the conventional angle measurement method proposed in the article is to perform amplitude comparison (or phase comparison) method angle measurement on target data after detection channel signal processing (including pulse compression, beam forming, doppler filtering, etc.), and finally estimate the angle of the target.
However, this method has a signal-to-noise ratio loss due to the signal processing of its detection channel, for example, when the radar transmits NLFM waveform, the pulse response filter used for pulse compression does not take into account the doppler information of the target, and its output has a certain signal-to-noise ratio loss, so that the target angle measurement accuracy is affected.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a method for improving the angle measurement precision of an NLFM waveform radar target, which comprises the following steps:
step 1, performing first pulse compression processing on a radar target echo signal to obtain a first pulse pressure echo signal;
step 3, Doppler processing is carried out on the beam forming result by adopting a Doppler filter to obtain a Doppler frequency estimated value;
and 5, performing sum-difference beam phase comparison single pulse angle measurement on the second pulse pressure echo signal to obtain a radar target angle measurement.
In an embodiment of the present invention, the step 1 specifically includes:
step 1.1, radar target echo signals received by N array elements are obtained, wherein the radar target echo signals are expressed as follows:
S＝[S1,S2,...,SN]T；
wherein S represents a radar target echo signal, SiIndicating the radar target echo signal received by the ith array element, i is 1,2,3i＝[Sqr]M×R, wherein ,SqrRepresenting radar target echo signal SiThe R sampling point of the middle q pulse, M is the receiving pulse number of each array element, R is the sampling point number in the radar transmitting signal pulse width]TRepresenting a vector transpose;
step 1.2, obtaining a pulse compression weight coefficient according to the NLFM waveform transmitted by the radar, wherein the pulse compression weight coefficient is expressed as:
Y＝[F1,F2，...,FR]H；
wherein Y represents a pulse compression weight coefficient, FrAn R-th value representing a pulse compression weight coefficient, R1, 2,3, R, b]HRepresenting a vector conjugate transpose;
step 1.3, obtaining a first pulse pressure echo signal according to the radar target echo signal and the pulse compression weight coefficient, wherein the first pulse pressure echo signal is expressed as:
X＝[X1,X2,..,XN]T；
wherein X represents a first pulse pressure echo signal, Xi＝SiY denotes the first pulse pressure echo signal on the ith array element.
In an embodiment of the present invention, the beam combination result in step 2 is expressed as:
P＝aH(θ0)X；
where P denotes the beamforming result, a (θ)0)＝[1,exp(j2πdsinθ0/λ),...,exp(j2πd(N-1)sinθ0/λ)]TRepresenting weight vectors, exp representing an exponential power with e as the base, j representing an imaginary unit, d representing an array element spacing, θ0Indicating the detection beam direction.
In an embodiment of the present invention, the step 3 specifically includes:
step 3.1, Doppler processing is carried out on the beam forming result by adopting a Doppler filter to obtain a plurality of amplitude response results;
and 3.2, finding a frequency point with the maximum corresponding amplitude from the plurality of amplitude response results, and obtaining the Doppler estimated value according to the frequency point.
In an embodiment of the present invention, the step 4 specifically includes:
step 4.1, performing pulse accumulation on the radar target echo signal according to the Doppler estimated value to obtain a pulse accumulation result, wherein the pulse accumulation result is expressed as:
G＝[G1,G2,...,GN]T；
wherein G represents the pulse accumulation result, Gi＝b(f′d)SiDenotes the pulse accumulation result of the i-th array element, b (f'd)＝[1,exp(j2πf′dtr),...,exp(j2πf′d((M-1)tr)]Pilot vector representing target, fd' denotes Doppler frequency estimate, trRepresenting a pulse repetition period;
and 4.2, updating the pulse compression weight coefficient according to the Doppler estimated value to obtain a new pulse compression coefficient, wherein the new pulse compression coefficient is expressed as:
Q＝Y⊙c(f′d)；
wherein Q represents a new pulse compression coefficient, c (f'd)＝[1,exp(-j2πf′dts),...,exp(-j2πf′d((R-1)ts)]TRepresenting the Doppler shift function, tsRepresenting adjacent sample pointsTime interval, ", indicates a Hadamard product;
and 4.3, obtaining a second pulse pressure echo signal according to the pulse accumulation result and the new pulse compression coefficient, wherein the second pulse pressure echo signal is expressed as:
Z＝[Z1,Z2,...,ZN]T；
wherein Z represents a second pulse pressure echo signal, Zi＝GiQ represents a second pulse pressure echo signal on the ith array element.
In an embodiment of the present invention, the step 5 specifically includes:
step 5.1, performing sum-difference beam phase single pulse angle measurement on the second pulse pressure echo signal to obtain measurement data, wherein the measurement data is represented as:
wherein K denotes measurement data, w2＝[1,exp(j2πdsinθ0/λ),...,exp(j2πd(N-1)sinθ0/λ)]TWeight vector, w, representing sum beam1＝[w2(1:N/2),-w2(N/2+1:N)]A weight vector representing the difference beam;
and 5.2, estimating and obtaining the radar target angle measurement according to the measurement data, wherein the radar target angle measurement is expressed as:
wherein ,
representing radar target angle measurement, | | | represents modulo, a (θ) ═ 1, exp (j2 π dsin θ/λ),. -, exp (j2 π d (N-1) sin θ/λ)]TThe steering vector of the antenna array element is shown, and theta represents the angle measurement range.
Compared with the prior art, the invention has the beneficial effects that:
according to the method for improving the angle measurement precision of the NLFM waveform radar target, the Doppler frequency estimation of the radar target echo signal is utilized to design a completely matched pulse response filter, the pulse compression processing of the radar target echo signal is carried out, the loss of the signal-to-noise ratio of angle estimation data is reduced, and therefore the angle measurement precision is improved and the performance is stable.
Drawings
Fig. 1 is a schematic flowchart of a method for improving NLFM waveform radar target angle measurement accuracy according to an embodiment of the present invention;
FIG. 2 is a diagram illustrating a comparison result of root mean square errors of angle measurement when a target angle changes between a conventional angle measurement method and the method provided by the embodiment of the invention;
FIG. 3 is a graph showing the comparison between the conventional pulse pressure result and the pulse pressure result of the method provided by the embodiment of the present invention;
fig. 4 is a partially enlarged schematic diagram of a comparison result between a conventional pulse pressure result and a pulse pressure result obtained by the method according to the embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to specific examples, but the embodiments of the present invention are not limited thereto.
Example one
Because the NLFM radar waveform is sensitive to Doppler frequency, the signal-to-noise ratio loss exists in the output of pulse compression, and the target detection and angle measurement performance of the radar are affected. Therefore, referring to fig. 1, fig. 1 is a schematic flow chart of a method for improving the angle measurement accuracy of an NLFM waveform radar target according to an embodiment of the present invention, and the method for improving the angle measurement accuracy of an NLFM waveform radar target according to an embodiment of the present invention includes the following steps:
step 1, performing first pulse compression processing on a radar target echo signal to obtain a first pulse pressure echo signal.
Specifically, in this embodiment, a uniform linear array including N array elements is used to receive a radar target echo signal, and the radar target echo signal is subjected to pulse compression processing, where step 1 specifically includes step 1.1, step 1.2, and step 1.3:
and 1.1, obtaining radar target echo signals S received by the N array elements.
Specifically, in this embodiment, radar target echo signals are received for N array elements, and specifically the radar target echo signals are represented as:
S＝[S1,S2,...,SN]T；
wherein S represents a radar target echo signal, SiIndicating the radar target echo signal received by the ith array element, i is 1,2,3i＝[Sqr]M×R, wherein ,SqrRepresenting radar target echo signal SiThe R sampling point of the middle q pulse, M is the receiving pulse number of each array element, R is the sampling point number in the radar transmitting signal pulse width]TRepresenting a vector transposition.
And step 1.2, obtaining a pulse compression weight coefficient according to the NLFM waveform transmitted by the radar.
Specifically, the present embodiment considers that NLFM radar waveforms are sensitive to doppler frequency, and therefore constructs a pulse compression weight coefficient from the radar transmitted NLFM waveform, specifically expressed as:
Y＝[F1,F2，...,FR]H；
wherein Y represents a pulse compression weight coefficient, FrAn R-th value representing a pulse compression weight coefficient, R1, 2,3, R, b]HRepresenting the vector conjugate transpose.
It should be noted that, the pulse compression weight coefficients correspondingly set for different radar emission waveforms are different, and specifically set according to actual radar emission waveforms, the radar emission waveform of this embodiment is an NLFM waveform.
And step 1.3, obtaining a first pulse pressure echo signal according to the radar target echo signal and the pulse compression weight coefficient.
Specifically, in this embodiment, a first pulse pressure echo signal is calculated according to the radar target echo signal obtained in step 1.1 and the pulse compression weight coefficient obtained in step 1.2, and specifically, the first pulse pressure echo signal is expressed as:
X＝[X1,X2,..,XN]T；
wherein X represents a first pulse pressure echo signal, Xi＝SiY denotes the first pulse pressure echo signal on the ith array element, i ═ 1,2,3.
In the embodiment, when the first pulse pressure echo signal is calculated in step 1.3, the influence of doppler shift is not considered, and the processing is the same as that of the conventional angle measurement method.
And 2, carrying out beam synthesis processing on the first pulse pressure echo signal to obtain a beam synthesis result.
Specifically, in this embodiment, a beamforming process is performed on the first pulse pressure echo signal by using a preset weight vector, and a beamforming result is obtained, where specifically the beamforming result is expressed as:
P＝aH(θ0)X；
where P denotes the beamforming result, a (θ)0)＝[1,exp(j2πdsinθ0/λ),...,exp(j2πd(N-1)sinθ0/λ)]TRepresenting a preset weight vector, exp representing an exponential power with e as a base, j representing an imaginary unit, d representing an array element interval, and theta0Indicating the detection beam direction.
And 3, performing Doppler processing on the beam forming result by adopting a Doppler filter to obtain a Doppler frequency estimated value.
Specifically, in the conventional angle measurement method, because the pulse response filter of the pulse compression does not take the doppler information of the target into account, the output of the conventional angle measurement method has a certain signal-to-noise ratio loss, so that the angle measurement accuracy of the target is affected. Therefore, in this embodiment, based on the consideration of the doppler information, the radar target angle measurement is further performed, and step 3 specifically includes step 3.1 and step 3.2:
and 3.1, performing Doppler processing on the beam synthesis result by adopting a Doppler filter to obtain a plurality of amplitude response results.
Specifically, in the case of the beamforming result in the doppler processing according to this embodiment, because the doppler frequency is unknown, a plurality of doppler filters are required, the frequencies of the doppler filters corresponding to different doppler filters are different, and the doppler processing is performed on the beamforming result by using the plurality of doppler filters to obtain a plurality of amplitude response results.
And 3.2, finding a frequency point with the maximum corresponding amplitude from the plurality of amplitude response results, and obtaining a Doppler estimated value according to the frequency point.
Specifically, after the amplitude response results are obtained in step 3.1, the larger the amplitude is, the more the doppler filter is matched with the doppler frequency, so that the present embodiment finds a frequency point with the largest corresponding amplitude from the amplitude response results, and determines a doppler estimated value according to the frequency point, where the estimated value is the doppler estimated value to be used for determining the perfectly matched impulse response filter in the present embodiment.
And 4, performing secondary pulse compression processing on the radar target echo signal according to the Doppler estimated value to obtain a second pulse pressure echo signal.
Specifically, after determining the doppler estimation value according to step 3, a perfectly matched impulse response filter is generated by using the doppler estimation value, and step 4 specifically includes step 4.1, step 4.2, and step 4.3:
and 4.1, performing pulse accumulation on the radar target echo signal according to the Doppler estimated value to obtain a pulse accumulation result.
Specifically, in this embodiment, first, pulse accumulation is performed on a radar target echo signal through a doppler estimation value to obtain a pulse accumulation result, and specifically, the pulse accumulation result is expressed as:
G＝[G1,G2,...,GN]T；
wherein G represents the pulse accumulation result, Gi＝b(f′d)SiDenotes the pulse accumulation result of the i-th array element, b (f'd)＝[1,exp(j2πf′dtr),...,exp(j2πf′d((M-1)tr)]Pilot vector representing target, fd' denotes Doppler frequency estimate, trRepresenting the pulse repetition period.
And 4.2, updating the pulse compression weight coefficient according to the Doppler estimated value to obtain a new pulse compression coefficient.
Specifically, in this embodiment, according to the doppler estimation value, the pulse compression weight coefficient in step 1.2 is updated to obtain a new pulse compression coefficient, and specifically, the new pulse compression coefficient is represented as:
Q＝Y⊙c(f′d)；
wherein Q represents a new pulse compression coefficient, c (f'd)＝[1,exp(-j2πf′dts),...,exp(-j2πf′d((R-1)ts)]TRepresenting the Doppler shift function, tsThe time interval representing adjacent samples, indicates the Hadamard product.
And 4.3, obtaining a second pulse pressure echo signal according to the pulse accumulation result and the new pulse compression coefficient.
Specifically, in this embodiment, the radar target echo signal and the pulse compression coefficient are considered by the doppler frequency, respectively, to obtain a pulse accumulation result after the doppler frequency is considered and a new pulse compression coefficient, and then obtain a second pulse pressure echo signal according to the pulse accumulation result and the new pulse compression coefficient, where the second pulse pressure echo signal is specifically represented as:
Z＝[Z1,Z2,...,ZN]T；
wherein Z represents a second pulse pressure echo signal, Zi＝GiQ denotes the second pulse pressure echo signal on the ith array element, i ═ 1,2,3.
And 5, performing sum-difference beam phase comparison single pulse angle measurement on the second pulse pressure echo signal to obtain a radar target angle measurement.
Specifically, in step 4 of this embodiment, a second pulse compression is performed to obtain a second pulse pressure echo signal Z, and sum-difference beam phase single pulse angle measurement is performed on the second pulse pressure echo signal, where step 5 specifically includes step 5.1 and step 5.2:
and 5.1, performing sum-difference beam phase single pulse angle measurement on the second pulse pressure echo signal to obtain measurement data.
Specifically, in this embodiment, a sum-difference beam phase comparison single pulse angle measurement method is adopted to obtain measurement data corresponding to angle measurement, and specifically, the measurement data is expressed as:
wherein K denotes measurement data, w2＝[1,exp(j2πdsinθ0/λ),...,exp(j2πd(N-1)sinθ0/λ)]TWeight vector, w, representing sum beam1＝[w2(1:N/2),-w2(N/2+1:N)]Representing the weight vector of the difference beam.
And 5.2, estimating according to the measurement data to obtain the radar target angle measurement.
Specifically, a radar target angle measurement is estimated from the measurement data K, specifically expressed as:
wherein ,
representing radar target angle measurement, | | | represents modulo, a (θ) ═ 1, exp (j2 π dsin θ/λ),. -, exp (j2 π d (N-1) sin θ/λ)]TThe steering vector of the antenna array element is shown, and theta represents the angle measurement range.
According to the method for improving the NLFM waveform radar target angle measurement precision, the Doppler frequency of a radar target echo signal is estimated by utilizing output results which are subjected to pulse compression processing (Doppler information is not considered) and beam synthesis processing in sequence to obtain a Doppler frequency estimated value, then a pulse response filter which is completely matched with the Doppler frequency estimated value is generated by utilizing the Doppler frequency estimated value, the completely matched pulse response filter is adopted to perform pulse compression processing on an original radar target echo signal, and finally the radar target angle is measured by performing sum-difference phase monopulse angle measurement on data subjected to pulse compression processing.
In order to illustrate the effectiveness of the method for improving the target angle measurement precision of the NLFM waveform radar, the method is verified by the following computer simulation:
1. simulation conditions
In simulation, the bandwidth B of a radar transmission signal is 2MHz, and the pulse transmission time width T isp300 mus, target doppler frequency fd10kHz, 10N of array elements of the radar antenna, 0.05m of wavelength λ and 0.025m of array element spacing d, a sum-difference beam phase monopulse angle measurement method is adopted, a sum beam points to 0 DEG, a signal-to-noise ratio SNR of a single array element is 10dB, and a sampling frequency fs10MHz, Doppler frequency estimate f 'of target'dMonte carlo experiments 1000 times 10.01 kHz.
2. Emulated content
Fig. 2 is a schematic diagram showing a comparison result of root mean square errors of angle measurement when a target angle changes according to a conventional angle measurement method and a method provided by an embodiment of the present invention, and a change curve diagram of angle measurement accuracy when the target angle changes according to the conventional angle measurement method and the method of the present invention is obtained through simulation under the above conditions, as shown in fig. 2, wherein an abscissa is the target angle and an ordinate is the root mean square error of the angle. As can be seen from fig. 2, the root mean square error of the conventional angle measurement method and the angle measurement method of the present invention varies with the angle of the target. The target angle root mean square error of the present invention is smaller. Fig. 2 can fully illustrate that the method of the present invention has higher angle measurement accuracy and more stable performance, and can actually improve the angle measurement accuracy of the NLFM waveform.
Fig. 3 and 4 show a comparison result between a conventional pulse pressure result and a pulse pressure result obtained by the method according to the embodiment of the present invention, fig. 3 shows a schematic diagram of a comparison result between a conventional pulse pressure result and a pulse pressure result obtained by the method according to the embodiment of the present invention, and fig. 4 shows a schematic diagram of a local enlargement of a comparison result between a conventional pulse pressure result and a pulse pressure result obtained by the method according to the embodiment of the present invention, wherein the NLFM pulse compression output result of the beam and the target angle of 0 ° are selected by using the above conditions, as shown in fig. 3, wherein the abscissa is a distance unit (unit is one) and the ordinate is an output signal amplitude value (normalized according. As can be seen from fig. 3, there are 5999 points from the range bin; FIG. 4 is an enlarged view of a portion of FIG. 3, and it can be seen from FIG. 4 that the pulse compression output of the conventional goniometric method exhibits a spectral shift and a peak power drop, which does not occur with the pulse compression output of the inventive method; as further shown in fig. 4, the pulse compression result of the conventional angle measurement method has a direct influence on the angle estimation result due to the reduction of the signal-to-noise ratio; however, the method compensates the Doppler frequency, the signal-to-noise ratio of the matched filter designed by considering the Doppler frequency is improved, and the angle measurement precision is further improved. Therefore, the method has obvious advantages.
In summary, in the method for improving the angle measurement accuracy of the NLFM waveform radar target provided in this embodiment, a perfectly matched impulse response filter is designed by using the doppler frequency estimation of the radar target echo signal, and the pulse compression processing of the radar target echo signal is performed to reduce the loss of the signal-to-noise ratio of the angle estimation data, so that the angle measurement accuracy is improved and the performance is stable.
The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and it is not intended that the invention be limited to these specific details. For those skilled in the art to which the invention pertains, several simple deductions or substitutions can be made without departing from the spirit of the invention, and all shall be considered as belonging to the protection scope of the invention.
Claims (6)
1. A method for improving the target angle measurement precision of an NLFM waveform radar is characterized by comprising the following steps:
step 1, performing first pulse compression processing on a radar target echo signal to obtain a first pulse pressure echo signal;
step 2, performing beam forming processing on the first pulse pressure echo signal to obtain a beam forming result;
step 3, Doppler processing is carried out on the beam forming result by adopting a Doppler filter to obtain a Doppler frequency estimated value;
step 4, performing second pulse compression processing on the radar target echo signal according to the Doppler estimated value to obtain a second pulse pressure echo signal;
and 5, performing sum-difference beam phase comparison single pulse angle measurement on the second pulse pressure echo signal to obtain a radar target angle measurement.
2. The method for improving NLFM waveform radar target angle measurement accuracy according to claim 1, wherein the step 1 specifically comprises:
step 1.1, radar target echo signals received by N array elements are obtained, wherein the radar target echo signals are expressed as follows:
S＝[S1,S2,...,SN]T；
wherein S represents a radar target echo signal, SiIndicating the radar target echo signal received by the ith array element, i is 1,2,3i＝[Sqr]M×R, wherein ,SqrRepresenting radar target echo signal SiThe R sampling point of the middle q pulse, M is the receiving pulse number of each array element, R is the sampling point number in the radar transmitting signal pulse width]TRepresenting a vector transpose;
step 1.2, obtaining a pulse compression weight coefficient according to the NLFM waveform transmitted by the radar, wherein the pulse compression weight coefficient is expressed as:
Y＝[F1,F2，...,FR]H；
wherein Y represents a pulse compression weight coefficient, FrAn R-th value representing a pulse compression weight coefficient, R1, 2,3, R, b]HRepresenting a vector conjugate transpose;
step 1.3, obtaining a first pulse pressure echo signal according to the radar target echo signal and the pulse compression weight coefficient, wherein the first pulse pressure echo signal is expressed as:
X＝[X1,X2,..,XN]T；
wherein X represents a first pulse pressure echo signal, Xi＝SiY denotes the first pulse pressure echo signal on the ith array element.
3. The method for improving the angle measurement accuracy of the NLFM waveform radar target according to claim 2, wherein the beam combination result in the step 2 is expressed as:
P＝aH(θ0)X；
where P denotes the beamforming result, a (θ)0)＝[1,exp(j2πdsinθ0/λ),...,exp(j2πd(N-1)sinθ0/λ)]TRepresenting weight vectors, exp representing an exponential power with e as the base, j representing an imaginary unit, d representing an array element spacing, θ0Indicating the detection beam direction.
4. The method for improving NLFM waveform radar target angle measurement accuracy according to claim 3, wherein the step 3 specifically comprises:
step 3.1, Doppler processing is carried out on the beam forming result by adopting a Doppler filter to obtain a plurality of amplitude response results;
and 3.2, finding a frequency point with the maximum corresponding amplitude from the plurality of amplitude response results, and obtaining the Doppler estimated value according to the frequency point.
5. The method for improving NLFM waveform radar target angle measurement accuracy according to claim 4, wherein the step 4 specifically comprises:
step 4.1, performing pulse accumulation on the radar target echo signal according to the Doppler estimated value to obtain a pulse accumulation result, wherein the pulse accumulation result is expressed as:
G＝[G1,G2,...,GN]T；
wherein G represents the pulse accumulation result, Gi＝b(f′d)SiDenotes the pulse accumulation result of the i-th array element, b (f'd)＝[1,exp(j2πf′dtr),...,exp(j2πf′d((M-1)tr)]Pilot vector representing target, fd' denotes Doppler frequency estimate, trRepresenting a pulse repetition period;
and 4.2, updating the pulse compression weight coefficient according to the Doppler estimated value to obtain a new pulse compression coefficient, wherein the new pulse compression coefficient is expressed as:
Q＝Y⊙c(f′d)；
wherein Q represents a new pulse compression coefficient, c (f'd)＝[1,exp(-j2πf′dts),...,exp(-j2πf′d((R-1)ts)]TRepresenting the Doppler shift function, tsTime intervals indicating adjacent sample points, which indicates a Hadamard product;
and 4.3, obtaining a second pulse pressure echo signal according to the pulse accumulation result and the new pulse compression coefficient, wherein the second pulse pressure echo signal is expressed as:
Z＝[Z1,Z2,...,ZN]T；
wherein Z represents a second pulse pressure echo signal, Zi＝GiQ represents a second pulse pressure echo signal on the ith array element.
6. The method for improving NLFM waveform radar target angle measurement accuracy according to claim 5, wherein the step 5 specifically comprises:
step 5.1, performing sum-difference beam phase single pulse angle measurement on the second pulse pressure echo signal to obtain measurement data, wherein the measurement data is represented as:
wherein K denotes measurement data, w2＝[1,exp(j2πdsinθ0/λ),...,exp(j2πd(N-1)sinθ0/λ)]TWeight vector, w, representing sum beam1＝[w2(1:N/2),-w2(N/2+1:N)]A weight vector representing the difference beam;
and 5.2, estimating and obtaining the radar target angle measurement according to the measurement data, wherein the radar target angle measurement is expressed as:
wherein ,
representing radar target angle measurement, | | | represents modulo, a (θ) ═ 1, exp (j2 π dsin θ/λ),. -, exp (j2 π d (N-1) sin θ/λ)]TThe steering vector of the antenna array element is shown, and theta represents the angle measurement range.
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