阅读说明：本技术 一种调频步进雷达的和差单脉冲测角方法 (Sum-difference monopulse angle measurement method of frequency modulation stepping radar ) 是由 陈希信 王洋 李坡 弓盼 张庆海 于 2020-12-07 设计创作，主要内容包括：本发明公开了一种调频步进雷达的和差单脉冲测角方法,包括以下步骤：1)获取调频步进雷达和差单脉冲测角的角敏函数；2)测量目标距离像中幅度大、相距远互不干扰的若干强散射中心的角度；3)对强散射中心的角度测量值进行加权平均,得到最终的目标角度。建立了调频步进雷达和差单脉冲测角的角敏函数计算公式；调频步进雷达在增加和差单脉冲测角功能后,能够对目标的方位角、俯仰角进行精确测量；高精度测角改善了雷达对运动目标的跟踪性能。(The invention discloses a sum-difference monopulse angle measurement method of a frequency modulation stepping radar, which comprises the following steps of: 1) acquiring an angle sensitive function of a frequency modulation stepping radar and a difference monopulse angle measurement; 2) measuring the angles of a plurality of strong scattering centers which have large amplitude and far distance in the target distance image and do not interfere with each other; 3) and carrying out weighted average on the angle measurement value of the strong scattering center to obtain a final target angle. Establishing an angle sensitive function calculation formula of a frequency modulation stepping radar and a difference monopulse angle measurement; after the frequency modulation stepping radar is added with the sum and difference monopulse angle measurement function, the azimuth angle and the pitch angle of a target can be accurately measured; the high-precision angle measurement improves the tracking performance of the radar to the moving target.)

1. A sum-difference monopulse angle measurement method of a frequency modulation stepping radar is characterized by comprising the following steps:

1) acquiring an angle sensitive function of a frequency modulation stepping radar and a difference monopulse angle measurement;

2) measuring the angles of a plurality of strong scattering centers which have large amplitude and far distance in the target distance image and do not interfere with each other;

3) and carrying out weighted average on the angle measurement value of the strong scattering center to obtain a final target angle.

2. A sum-difference monopulse angular measurement method of a frequency modulated step radar as claimed in claim 1, characterized by: the step 1) obtains an angle sensitive function of a frequency modulation stepping radar and a differential monopulse angle measurement, specifically,

1-1) setting the FM step radar to emit a frequency step linear FM coherent pulse string composed of K pulses, namely a frequency step LFM coherent pulse string, the pulse width is T, and the pulse repetition period is T_rThe carrier frequency of the 1 st pulse, i.e. the initial carrier frequency, is f₀The carrier frequency difference of two adjacent pulses, i.e. the frequency step amount is deltaf,

frequency stepping LFM coherent pulse train signal s transmitted by radar_t(t) is a group of,

in the formula: t is time, a_tThe rect () is a rectangular function for the amplitude of the transmitted signal, when-1/2 ≦ t ≦ 1/2, rect (t) 1, otherwise, rect (t) 0, u (·) is an LFM pulse signal, u (t) exp (j π γ t)²) T/2 ≦ T/2, γ ≦ B/T is the chirp rate of the LFM pulse signal, B is the bandwidth of the LFM pulse signal, j is the imaginary unit²＝-1；

1-2) the antenna array of the frequency modulation stepping radar is a uniform linear array consisting of N array elements, the distance between two adjacent array elements is d, if the distance is R₀CornerDegree theta_tA stationary point target is arranged, the radar emission signal meets the point target in the propagation process to generate an echo signal, the echo signal is received by the radar antenna array, and the echo signal s received by the nth array element_r′_n(t) is a group of,

in the formula: a is_rBeing amplitude of echo signal, t₀＝2R₀C is the two-way time delay of the echo signal received by the reference array element, c is the speed of light, tau_n＝ndsinθ_tAnd/c is the time delay of the echo signal received by the nth array element relative to the reference array element, wherein N is 0,1, the.

Let the No. 0 array element be the reference array element, then tau₀＝0，

To echo signal s'_rn(t) performing mixing processing to obtain zero intermediate frequency signal s_rn(t)，

For array aperture transit time τ_N-1＝(N-1)dsinθ_tC, when the condition B < 1/τ is satisfied_N-1When, the formula (3) can be represented as,

in the formula: lambda [ alpha ]_kIs the wavelength of the k-th pulse, λ_k＝c/(f₀+kΔf)，k＝0,1,...,K-1，

Synthesizing echo signals on N array elements to obtain a target echo signal vector s_r(t)，

In the formula:φ_tk＝(2π/λ_k)dsinθ_tthe superscript T represents taking the transpose;

1-3) setting a pair target echo signal vector s_r(t) steering vector a for performing sum beamforming_ΣkSteering vector a for differential beamforming_ΔkIn order to realize the purpose,

a_Σk＝a_0k⊙ω_Σ,a_Δk＝a_0k⊙ω_Δ (6)

in the formula:φ_0k＝(2π/λ_k)dsinθ₀，θ₀pointing for sum beam forming, ω_ΣWindow function, ω, for sum beam forming_ΔA window function for the difference beamforming, which is a Hadamard product,

target echo signal vector s of the pair formula (5)_r(t) performing sum beam forming to obtain a sum beam signal s_Σ(t) is a group of,

in the formula: the superscript H denotes taking the conjugate transpose,

target echo signal vector s of the pair formula (5)_r(t) performing difference beam forming to obtain a difference beam signal s_Δ(t) is a group of,

1-4) summing the beam signal s of formula (7)_Σ(t) transforming to the frequency domain to obtain a first spectral signal S_Σ(f)，

In the formula: f is the frequency of the signal to be detected,is the frequency spectrum of the LFM signal,

the difference beam signal s of equation (8)_Δ(t) transforming to the frequency domain to obtain a second spectral signal S_Δ(f)，

In the formula:

according to the theory of matched filters, the frequency response function of the matched filter of the echo signal is U^*(f) When the upper symbol indicates the conjugate, the first spectrum signal of expression (9) is output as S 'after passing through the matched filter'_Σ(f)，

In the formula: a'_r＝a_rThe/gamma is the amplitude of the matched filter output signal,

the second spectrum signal of equation (10) is output as S 'after passing through a matched filter'_Δ(f)，

Performing inverse Fourier transform on equation (11) to realize coarse distance resolution with resolution c/(2B) to obtain a first signal s'_Σ(t)，

Performing inverse Fourier transform on equation (12) to realize coarse distance resolution with resolution c/(2B) to obtain a second signal s'_Δ(t)，

1-5) in order to realize the distance high resolution with the resolution of c/(2K delta f), the inverse Fourier transform is respectively executed on each distance coarse resolution unit of the formula (13) to obtain the sum beam high resolution range profile of the unit where the target is located

In the formula: theta is equal to theta_t-θ₀Is a target angle theta_tPointing theta with respect to the array and beam₀The deviation of (a) is determined,

respectively executing inverse Fourier transform on each range coarse resolution unit of the formula (14) to obtain a difference beam high-resolution range profile of the unit where the target is located

1-6) high resolution range profile for the sum beam in equation (15)Differential beam high resolution range profile in sum (16)Calculating the ratio of the two to obtain an angle sensitive function chi (theta),

3. a sum-difference monopulse angular measurement method of a frequency modulated step radar as claimed in claim 2, characterized in that: the step 2) is to measure the sum beam high-resolution range profile of the targetThe angles of a plurality of strong scattering centers with large medium amplitude and long distance without mutual interference are specifically,

2-1) after distance coarse resolution and high resolution processing, the frequency modulation stepping radar obtains high resolution range images of the target on both a sum wave beam channel and a difference wave beam channel, and then the high resolution range images of the sum wave beam channel are subjected to target detection to obtain a plurality of strong scattering centers of the target;

2-2) respectively calculating the ratio of the difference beam to the sum beam at a plurality of strong scattering centers, comparing the difference beam to the sum beam with an angle sensitive function, and measuring the deviation of the target azimuth angle or the pitch angle relative to the sum beam direction according to the relation between the angle sensitive function and the angle, and recording the deviation as { theta [ [ theta ] ]₁,θ₂,…,θ_LWhere L is the number of strong scattering centers.

4. A frequency modulated stepped radar sum and difference monopulse angle measurement method according to claim 3, characterised in that: the step 3) is to perform weighted average on the angle measurement value of the strong scattering center to obtain a final target angle, specifically,

for angle deviation value { theta₁,θ₂,...,θ_LCarry out weighted average and point with the sum beam at theta₀Add up to obtain the angle of the target

In the formula:is a weighted value of_lThe echo amplitude at the ith strong scattering center is 1, 2.

Technical Field

The invention relates to an angle measurement method of a frequency modulation stepping radar, in particular to a sum-difference monopulse angle measurement method of the frequency modulation stepping radar.

Background

The distance high resolution is the basis for realizing the functions of radar target imaging, classification and identification and the like, and according to the pulse compression theory, the bandwidth of a radar signal is generally required to be increased. The frequency modulation step signal is a wide band radar signal capable of realizing high resolution, which is composed of a string of coherent narrow band pulses with linearly hopping carrier frequencies, and each pulse is narrow band, so that the instantaneous bandwidth of the receiver and the sampling rate requirement of an analog-to-digital converter are reduced, and the wide band radar signal becomes a wide concerned wide band radar signal form.

Angle measurement is one of basic functions of modern radars, and sum-difference monopulse angle measurement is a commonly used angle measurement mode in radars, but deep research on frequency modulation stepping radars and difference monopulse angle measurement problems is not seen at present.

Disclosure of Invention

The invention aims to provide a sum and difference monopulse angle measurement method of a frequency modulation stepping radar, which establishes an angle sensitive function calculation formula of the sum and difference monopulse angle measurement of the frequency modulation stepping radar; after the frequency modulation stepping radar is added with the sum and difference monopulse angle measurement function, the azimuth angle and the pitch angle of a target can be accurately measured; the high-precision angle measurement improves the tracking performance of the radar to the moving target.

In order to achieve the above object, according to one aspect of the present invention, the present invention provides the following technical solutions:

a sum-difference monopulse angle measurement method of a frequency modulation stepping radar comprises the following steps:

1) acquiring an angle sensitive function of a frequency modulation stepping radar and a difference monopulse angle measurement;

2) measuring the angles of a plurality of strong scattering centers which have large amplitude and far distance in the target distance image and do not interfere with each other;

3) and carrying out weighted average on the angle measurement value of the strong scattering center to obtain a final target angle.

The invention is further configured to: the step 1) obtains an angle sensitive function of a frequency modulation stepping radar and a differential monopulse angle measurement, specifically,

1-1) setting the FM step radar to emit a frequency step linear FM coherent pulse string composed of K pulses, namely a frequency step LFM coherent pulse string, the pulse width is T, and the pulse repetition period is T_rThe carrier frequency of the 1 st pulse, i.e. the initial carrier frequency, is f₀The carrier frequency difference of two adjacent pulses, i.e. the frequency step amount is deltaf,

frequency stepping with radar transmissionLFM coherent pulse train signal s_t(t) is a group of,

in the formula: t is time, a_tThe rect () is a rectangular function for the amplitude of the transmitted signal, when-1/2 ≦ t ≦ 1/2, rect (t) 1, otherwise, rect (t) 0, u (·) is an LFM pulse signal, u (t) exp (j π γ t)²) T/2 ≦ T/2, γ ≦ B/T is the chirp rate of the LFM pulse signal, B is the bandwidth of the LFM pulse signal, j is the imaginary unit²＝-1；

1-2) the antenna array of the frequency modulation stepping radar is a uniform linear array consisting of N array elements, the distance between two adjacent array elements is d, if the distance is R₀Angle theta_tA stationary point target is arranged, the radar emission signal meets the point target in the propagation process to generate a return signal, the return signal is received by the radar antenna array, and then the return signal s 'is received by the n array element'_rn(t) is a group of,

in the formula: a is_rBeing amplitude of echo signal, t₀＝2R₀C is the two-way time delay of the echo signal received by the reference array element, c is the speed of light, tau_n＝ndsinθ_tAnd/c is the time delay of the echo signal received by the nth array element relative to the reference array element, wherein N is 0,1, the.

Let the No. 0 array element be the reference array element, then tau₀＝0，

To echo signal s'_rn(t) performing mixing processing to obtain zero intermediate frequency signal s_rn(t)，

For array aperture transit time τ_N-1＝(N-1)dsinθ_tC, when the condition B < 1/τ is satisfied_N-1When, the formula (3) can be represented as,

in the formula: lambda [ alpha ]_kIs the wavelength of the k-th pulse, λ_k＝c/(f₀+kΔf)，k＝0,1,...,K-1，

Synthesizing echo signals on N array elements to obtain a target echo signal vector s_r(t)，

In the formula:φ_tk＝(2π/λ_k)dsinθ_tthe superscript T represents taking the transpose;

1-3) setting a pair target echo signal vector s_r(t) steering vector a for performing sum beamforming_ΣkSteering vector a for differential beamforming_ΔkIn order to realize the purpose,

a_Σk＝a_0k⊙ω_Σ,a_Δk＝a_0k⊙ω_Δ (6)

in the formula:φ_0k＝(2π/λ_k)dsinθ₀，θ₀pointing for sum beam forming, ω_ΣWindow function, ω, for sum beam forming_ΔA window function for the difference beamforming, which is a Hadamard product,

target echo signal vector s of the pair formula (5)_r(t) performing sum beam forming to obtain a sum beam signal s_Σ(t) is a group of,

in the formula: the superscript H denotes taking the conjugate transpose,

target echo signal vector s of the pair formula (5)_r(t) performing difference beam forming to obtain a difference beam signal s_Δ(t) is a group of,

1-4) summing the beam signal s of formula (7)_Σ(t) transforming to the frequency domain to obtain a first spectral signal S_Σ(f)，

In the formula: f is the frequency of the signal to be detected,is the frequency spectrum of the LFM signal,

the difference beam signal s of equation (8)_Δ(t) transforming to the frequency domain to obtain a second spectral signal S_Δ(f)，

In the formula:

according to the theory of matched filters, the frequency response function of the matched filter of the echo signal is U^*(f) When the upper symbol indicates the conjugate, the first spectrum signal of expression (9) is output as S 'after passing through the matched filter'_Σ(f)，

In the formula: a'_r＝a_rThe/gamma is the amplitude of the matched filter output signal,

the second spectrum signal of equation (10) is output as S 'after passing through a matched filter'_Δ(f)，

Performing inverse Fourier transform on equation (11) to realize coarse distance resolution with resolution c/(2B) to obtain a first signal s'_Σ(t)，

Performing inverse Fourier transform on equation (12) to realize coarse distance resolution with resolution c/(2B) to obtain a second signal s'_Δ(t)，

1-5) in order to realize the distance high resolution with the resolution of c/(2K delta f), the inverse Fourier transform is respectively executed on each distance coarse resolution unit of the formula (13) to obtain the sum beam high resolution range profile of the unit where the target is located

In the formula: theta is equal to theta_t-θ₀Is a target angle theta_tPointing theta with respect to the array and beam₀The deviation of (a) is determined,

respectively executing inverse Fourier transform on each range coarse resolution unit of the formula (14) to obtain a difference beam high-resolution range profile of the unit where the target is located

1-6) high resolution range profile for the sum beam in equation (15)Differential beam high resolution range profile in sum (16)Calculating the ratio of the two to obtain an angle sensitive function chi (theta),

the invention is further configured to: the step 2) is to measure the sum beam high-resolution range profile of the targetThe angles of a plurality of strong scattering centers with large medium amplitude and long distance without mutual interference are specifically,

2-1) after distance coarse resolution and high resolution processing, the frequency modulation stepping radar obtains high resolution range images of the target on both a sum wave beam channel and a difference wave beam channel, and then the high resolution range images of the sum wave beam channel are subjected to target detection to obtain a plurality of strong scattering centers of the target;

2-2) respectively calculating the ratio of the difference beam to the sum beam at a plurality of strong scattering centers, comparing the difference beam to the sum beam with an angle sensitive function, and measuring the deviation of the target azimuth angle or the pitch angle relative to the sum beam direction according to the relation between the angle sensitive function and the angle, and recording the deviation as { theta [ [ theta ] ]₁,θ₂,...,θ_LWhere L is the number of strong scattering centers.

The invention is further configured to: the step 3) is to perform weighted average on the angle measurement value of the strong scattering center to obtain a final target angle, specifically,

for angle deviation value { theta₁,θ₂,...,θ_LCarry out weighted average and point with the sum beam at theta₀Add up to obtain the angle of the target

In the formula:is a weighted value of_lThe echo amplitude at the ith strong scattering center is 1, 2.

Compared with the prior art, the invention has the advantages that: (1) establishing an angle sensitive function calculation formula of a frequency modulation stepping radar and a difference monopulse angle measurement; (2) after the frequency modulation stepping radar is added with the sum and difference monopulse angle measurement function, the azimuth angle and the pitch angle of a target can be accurately measured; (3) the high-precision angle measurement improves the tracking performance of the radar to the moving target.

Drawings

FIG. 1 is a flow chart of a sum and difference monopulse angular measurement method of a frequency modulated stepped radar of the present invention;

FIG. 2 is a high resolution range profile of the sum and difference beam outputs of a sum and difference monopulse goniometry method of a frequency modulated stepped radar of the present invention;

FIG. 3 is a graph showing the relationship between the angle sensitive function and the target angle of the sum and difference monopulse angle measurement method of the frequency modulated stepped radar of the present invention.

Detailed Description

The invention is further described with reference to the accompanying drawings.

The invention provides a sum and difference monopulse angle measurement method of a frequency modulation stepping radar, which establishes an angle sensitive function calculation formula of the sum and difference monopulse angle measurement of the frequency modulation stepping radar; after the frequency modulation stepping radar is added with the sum and difference monopulse angle measurement function, the azimuth angle and the pitch angle of a target can be accurately measured; the high-precision angle measurement improves the tracking performance of the radar to the moving target.

A sum-difference monopulse angle measurement method of a frequency modulation stepping radar comprises the following steps:

1) acquiring an angle sensitive function of a frequency modulation stepping radar and a difference monopulse angle measurement;

in particular to a method for preparing a high-performance nano-silver alloy,

1-1) setting the FM step radar to emit a frequency step linear FM coherent pulse string composed of K pulses, namely a frequency step LFM coherent pulse string, the pulse width is T, and the pulse repetition period is T_rThe carrier frequency of the 1 st pulse, i.e. the initial carrier frequency, is f₀The carrier frequency difference of two adjacent pulses, i.e. the frequency step amount is deltaf,

frequency stepping LFM coherent pulse train signal s transmitted by radar_t(t) is a group of,

in the formula: t is time, a_tThe rect () is a rectangular function for the amplitude of the transmitted signal, when-1/2 ≦ t ≦ 1/2, rect (t) 1, otherwise, rect (t) 0, u (·) is an LFM pulse signal, u (t) exp (j π γ t)²) T/2 ≦ T/2, γ ≦ B/T is the chirp rate of the LFM pulse signal, B is the bandwidth of the LFM pulse signal, j is the imaginary unit²＝-1；

1-2) the antenna array of the frequency modulation stepping radar is a uniform linear array consisting of N array elements, the distance between two adjacent array elements is d, if the distance is R₀Angle theta_tA stationary point target is arranged, the radar emission signal meets the point target in the propagation process to generate a return signal, the return signal is received by the radar antenna array, and then the return signal s 'is received by the n array element'_rn(t) is a group of,

in the formula: a is_rBeing amplitude of echo signal, t₀＝2R₀C is the two-way time delay of the echo signal received by the reference array element, c is the speed of light, tau_n＝ndsinθ_tAnd/c is the time delay of the echo signal received by the nth array element relative to the reference array element, wherein N is 0,1, the.

Let the No. 0 array element be the reference array element, then tau₀＝0，

For echo signal s_r′_n(t) performing mixing processing to obtain zero intermediate frequency signal s_rn(t)，

For array aperture transit time τ_N-1＝(N-1)dsinθ_tC, when the condition B < 1/τ is satisfied_N-1When, the formula (3) can be represented as,

in the formula: lambda [ alpha ]_kIs the wavelength of the k-th pulse, λ_k＝c/(f₀+kΔf)，k＝0,1,...,K-1，

Synthesizing echo signals on N array elements to obtain a target echo signal vector s_r(t)，

In the formula:φ_tk＝(2π/λ_k)dsinθ_tthe superscript T represents taking the transpose;

1-3) setting a pair target echo signal vector s_r(t) steering vector a for performing sum beamforming_ΣkSteering vector a for differential beamforming_ΔkIn order to realize the purpose,

a_Σk＝a_0k⊙ω_Σ,a_Δk＝a_0k⊙ω_Δ (6)

in the formula:φ_0k＝(2π/λ_k)dsinθ₀，θ₀pointing for sum beam forming, ω_ΣWindow function, ω, for sum beam forming_ΔA window function for the difference beamforming, which is a Hadamard product,

target echo signal vector s of the pair formula (5)_r(t) performing sum beam forming to obtain a sum beam signal s_Σ(t) is a group of,

in the formula: the superscript H denotes taking the conjugate transpose,

target echo signal vector s of the pair formula (5)_r(t) performing difference beam forming to obtain a difference beam signal s_Δ(t) is a group of,

1-4) summing the beam signal s of formula (7)_Σ(t) transforming to the frequency domain to obtain a first spectral signal S_Σ(f)，

In the formula: f is the frequency of the signal to be detected,is the frequency spectrum of the LFM signal,

the difference beam signal s of equation (8)_Δ(t) transforming to the frequency domain to obtain a second spectral signal S_Δ(f)，

In the formula:

according to the theory of matched filters, the frequency response function of the matched filter of the echo signal is U^*(f) When the upper symbol indicates the conjugate, the first spectrum signal of expression (9) is output as S 'after passing through the matched filter'_Σ(f)，

In the formula: a'_r＝a_rThe/gamma is the amplitude of the matched filter output signal,

the second spectrum signal of equation (10) is output as S 'after passing through a matched filter'_Δ(f)，

Performing inverse Fourier transform on equation (11) to realize coarse distance resolution with resolution c/(2B) to obtain a first signal s'_Σ(t)，

Performing inverse Fourier transform on equation (12) to realize coarse distance resolution with resolution c/(2B) to obtain a second signal s'_Δ(t)，

1-5) in order to achieve high resolution at a distance of c/(2K Δ f) resolution, each distance in equation (13) isRespectively executing inverse Fourier transform on the coarse resolution units to obtain sum-beam high-resolution range profiles of the units where the targets are located

In the formula: theta is equal to theta_t-θ₀Is a target angle theta_tPointing theta with respect to the array and beam₀The deviation of (a) is determined,

respectively executing inverse Fourier transform on each range coarse resolution unit of the formula (14) to obtain a difference beam high-resolution range profile of the unit where the target is located

1-6) high resolution range profile for the sum beam in equation (15)Differential beam high resolution range profile in sum (16)Calculating the ratio of the two to obtain an angle sensitive function chi (theta),

2) measuring the angles of a plurality of strong scattering centers which have large amplitude and far distance in the target distance image and do not interfere with each other;

in particular to a method for preparing a high-performance nano-silver alloy,

2-1) after distance coarse resolution and high resolution processing, the frequency modulation stepping radar obtains high resolution range images of the target on both a sum wave beam channel and a difference wave beam channel, and then the high resolution range images of the sum wave beam channel are subjected to target detection to obtain a plurality of strong scattering centers of the target;

2-2) respectively calculating the ratio of the difference beam to the sum beam at a plurality of strong scattering centers, comparing the difference beam to the sum beam with an angle sensitive function, and measuring the deviation of the target azimuth angle or the pitch angle relative to the sum beam direction according to the relation between the angle sensitive function and the angle, and recording the deviation as { theta [ [ theta ] ]₁,θ₂,...,θ_LWhere L is the number of strong scattering centers.

3) Carrying out weighted average on the angle measurement value of the strong scattering center to obtain a final target angle;

in particular to a method for preparing a high-performance nano-silver alloy,

for angle deviation value { theta₁,θ₂,...,θ_LCarry out weighted average and point with the sum beam at theta₀Add up to obtain the angle of the target

In the formula:is a weighted value of_lThe echo amplitude at the ith strong scattering center is 1, 2.

It should be noted that, since the angle-sensitive function of equation (17) is derived for a single scattering center, for a plurality of scattering centers in the target range image, to avoid mutual interference, a strong scattering center with a large amplitude and a long distance should be selected, and the azimuth angle or the elevation angle thereof is measured and weighted-averaged.

The sum and difference monopulse angle measurement method of the frequency modulation stepping radar is adopted for simulation, and the performance of the angle measurement method is verified through a simulation example.

The array antenna provided with the radar is a uniform linear array consisting of 50 array elements, the spacing of the array elements is half of the wavelength corresponding to the frequency modulation stepping central frequency point, the sum beam direction is the array normal direction, and the sum beam and the difference beam form a Taylor window and a Berris window which respectively adopt-35 dB. The frequency stepping coherent pulse train comprises 32 LFM pulses, the time width of the LFM pulses is 10 mus, the bandwidth is 25MHz, the frequency stepping amount between the pulses is 25MHz, and the radar initial carrier frequency is 1 GHz. Assuming a stationary extended range target, containing 3 scattering centers, all at 1 amplitude, at distances of 1000-0.75m, 1000m, 1000+0.75m, respectively, the target direction is directed 1 off the beam.

Firstly, sum and difference wave beam forming is carried out on a simulation echo pulse train, then, conventional matched filtering pulse pressure is carried out on each LFM pulse to realize coarse distance resolution, finally, inverse Fourier transform is carried out on a coarse resolution unit where a target is located to obtain a high resolution range profile of the target, as shown in figure 2, the range profiles of the sum wave beam and the difference wave beam in the graph are basically the same, and only 3 peak values of the difference wave beam are lower. Taking these 3 peak points, the ratio of the difference beam to the sum beam is calculated, respectively, as shown by the circles in fig. 3. The solid line in fig. 3 represents the relationship of the angle sensitive function to the target angle.

From fig. 3, the angles of 3 scattering center points can be obtained, and then they are subjected to angle weighted average processing according to equation (18), so that the target angle is 1.02 ° and is close to the true angle 1 °, that is, the measurement error is not large, and this result shows that: the angle sensitive function theoretically deduced in the invention is correct; secondly, angle measurement errors are caused by mutual interference of 3 scattering center echoes in the distance image, and in order to avoid mutual interference, strong scattering centers with large amplitude and long distance in the target distance image are actually selected to measure angles.

The foregoing illustrates and describes the principles, general features, and advantages of the present invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.