CN104122548A - Angle measuring method for mechanical-scanning meter-wave array radar - Google Patents

Abstract

The invention discloses an angle measuring method for a mechanical-scanning meter-wave array radar and mainly solves the problem of low accuracy in angle measuring of the scanning meter-wave array radar. The angle measuring method includes the steps of 1, subjecting an antenna array to receiving pulse echo signals of a radar; 2, calculating all research weight vectors of pulses; 3, with an optional pulse as a reference pulse, compensating the research weight vectors of other pulses; 4, constructing a cost function on the basis of the pulse echo signals and compensated research weight vectors; 5, performing beam scanning to the cost function to acquire an off-axis angle of a target ; 6, adding the target off-axis angle to a reference angle of the reference pulse to acquire an accurate angle of the target. The angle measuring method has the advantages of small angle measuring error, high accuracy and excellent robustness and is applied to accurate positioning and target tracking to the target by the mechanical-scanning meter-wave array radar.

Description

Machine is swept metric wave array radar angle-measuring method

Technical field

The invention belongs to Radar Technology field, particularly radar angle measurement method, can be used for machine and sweeps the angle measurement of metric wave array radar, can be used for target following and altitude measurement in VHF radar.

Background technology

Metre wave radar is because signal attenuation is little, and detection range is far away, has unique advantage at the aspect such as over-the-horizon detection, anti-electronic interferences, but simultaneously because the wavelength of metre wave radar is longer, wave beam is wider, makes its angle-resolved rate variance, and angle measurement accuracy is low.Mechanical scanning radar is because cost is low, realizes the factor such as simple always by people's widespread use.Mechanic scan radar angle-measuring method generally adopts maximum-signal method, but the precision of this method is poor, especially sweeps metre wave radar for machine.Because its electric size is less, wave beam is wider, and maximum-signal method angle measurement accuracy is not high.

Society often needs radar to have multi-functional characteristic now.In order to meet this demand, machine is swept and in metre wave radar, has just been occurred that machine sweeps the mode of sweeping that powers up, and the azimuth dimension of radar antenna not only can mechanical scanning but also can electric scanning.At this moment radar antenna often adopts array antenna, and is digital beam formation system.Here it is, and so-called machine is swept metric wave array radar.

Fourth aigret flies professor and provided digital beam forming technology in " Principles of Radar [M], publishing house of Xian Electronics Science and Technology University, 2002 " book.Digital beam forming technology refers to the aperture that utilizes array antenna, forms received beam by digital signal processing in the direction of expecting.Sampled data is done to weighted sum, can, by changing weights, make the different direction of beam position, and realize the scanning of wave beam.The metric wave array radar routine of angle-measuring method sweep to(for) this machine is first to utilize digital beam scan method to measure the off-axis angle of target and antenna normal direction by individual pulse signal, add the now angle of antenna normal direction and direct north, obtain the angle on target that individual pulse records, it is exactly angle on target that the angle that all pulses are recorded is averaged.

Although it is that machine is swept the mode of sweeping that powers up that machine is swept metric wave array radar, meet the multi-functional demand of radar, but the feature of not utilizing array antenna and mechanical scanning to combine completely while adopting conventional angle-measuring method angle measurement, make machine sweep metric wave array radar cannot to make full use of the resource of array hyperchannel and mechanical scanning in the time of mechanical scanning, cause its angle error large, still very low defect of angle measurement accuracy.

Summary of the invention

The deficiency that the object of the invention is to sweep for above-mentioned machine the conventional angle-measuring method of metric wave array radar, proposes a kind of machine and sweeps metric wave array radar angle-measuring method, to reduce the impact of noise on signal, reduces angle error, improves angle measurement accuracy.

Technical scheme of the present invention is achieved in that for achieving the above object

One, technical thought

Compensate by the right of search vector of machine being swept to metric wave array radar digital beam when scanning, by multiple impulse compensations of radar emission to same position.Utilize right of search vector and echoed signal after compensation, set up the cost function of an off-axis angle taking some pulses as benchmark, this cost function is carried out beam scanning and obtained the off-axis angle of target, utilize the off-axis angle reference angle corresponding with it of target to obtain the true angle of target.

Two, performing step

According to above-mentioned technical thought, performing step of the present invention comprises as follows:

(1), when antenna scanning, at interval of a pulse of Δ θ transmitting, and will launch i pulse time, the angle of center of antenna normal and horizontal reference plane is as reference angle i=1,2 ..., L, L is the pulse number of launching altogether in a beam angle, Δ θ is the interval of adjacent two pulses;

(2) establish machine and sweep metric wave array radar antenna and have N array element, utilize this N array element to receive echoed signal, obtain the echoed signal X of i pulse _i;

(3) search angle ψ is set near the antenna normal direction of i pulse, according to search angle, ψ calculates right of search vector w _i(ψ):

w _i(ψ)＝[1,exp(j2πdsinψ/λ),...,exp(j2π(N-1)dsinψ/λ)] ^T，

Wherein, the span of search angle ψ is greater than half-power beam width, and exp represents the exponential depth taking e the end of as, and d is antenna spacing, and λ is signal wavelength, [] ^trepresent the non-conjugated transposition of vector;

(4) taking first pulse as reference pulse to weight vector w _i(ψ) compensate, after being compensated, the weight vector of i pulse is w _i(ψ+(i-1) Δ θ);

(5) according to the echoed signal X receiving _iwith the weight vector w after compensation _i(ψ+(i-1) Δ θ), builds cost function P (ψ):

$P\left(\mathrm{\ψ}\right)=\left|X_1^{H}w\left(\mathrm{\ψ}\right)\right|+\left|X_2^{H}w(\mathrm{\ψ}+\mathrm{\Δ\θ})\right|+...+\left|X_L^{H}w(\mathrm{\ψ}+(L-1)\mathrm{\Δ\θ})\right|,$ Wherein, i=1,2 ..., L, || represent delivery value, [] ^hrepresent conjugate transpose;

(6) within the scope of search angle ψ, cost function P (ψ) is carried out to beam scanning, obtain the off-axis angle θ of target in the time of first pulse of transmitting ₁, by off-axis angle θ ₁reference angle with first pulse be added, obtain the accurate angle Φ of target, wherein

The present invention compared with prior art has following advantage:

1) angle measurement accuracy is high

The output data of carrying out after beam scanning due to each pulse have a maximal value, angle corresponding to this maximal value is exactly the off-axis angle of target, conventional method is only that the angle measurement result of each pulse is accumulated, be equivalent to binary integration, cause snr loss, angle measurement accuracy decreases.And the present invention is due to weight vector is compensated, build a cost function, be equivalent to all pulse scanning functions to carry out non-coherent accumulation, increase signal to noise ratio (S/N ratio), thereby improved angle measurement accuracy.

2) operand is little

Conventional angle-measuring method is that each pulse needs survey to scan angle measurement, and then is averaging.The present invention will carry out angle measurement again after all pulse weighted sums, only need run-down just can obtain angle on target, has reduced operand.

Brief description of the drawings

Fig. 1 is realization flow figure of the present invention;

Fig. 2 is with the present invention and the square error comparison diagram of traditional beam sweeping method in the time of antenna alignment;

Fig. 3 is with the present invention and the square error comparison diagram of traditional beam sweeping method in the time of antenna misalignments.

Embodiment

With reference to Fig. 1, specific embodiment of the invention step is as follows:

Step 1, structure machine is swept metric wave array radar antenna model.

If machine is swept the uniform line-array that the antenna of metric wave array radar is made up of N array element, the array element distance d between any two adjacent array elements all equates, and the half of the wavelength X transmitting for metre wave radar, d=λ/2.

Step 2, utilizes machine to sweep metric wave array radar transponder pulse signal.

Machine is swept metric wave array radar taking surface level as with reference to 0 ° of angle, and machine is swept metric wave array radar in the time of antenna scanning, and at interval of a pulse of Δ θ transmitting, and will launch i pulse time, the angle of center of antenna normal and horizontal reference plane is as reference angle i=1,2 ..., L, L is the pulse number of launching altogether in a beam angle, Δ θ is the interval of adjacent two pulses.

Step 3, received pulse echoed signal.

Utilize the machine described in step 1 to sweep L pulse described in metre wave radar antenna model receiving step 2, obtain the echoed signal X of i pulse _i: X _i=S _i× a (θ _i)+n _i,

Wherein, S _irepresent the complex envelope information of i pulse signal, s ₀for initial complex amplitude, j represents imaginary unit, f _drepresent the Doppler frequency of target, v represents the radial velocity of target with respect to radar, f ₀the centre frequency that represents radar transmitted pulse signal, c represents the light velocity, t represents sampling interval;

A (θ _i) be the steering vector of i pulse:

A (θ _i)=[1, exp (j2 π dsin θ _i/ λ) ..., exp (j2 π (N-1) dsin θ _i/ λ)] ^t, θ _irepresent that target, with respect to the angle between antenna normal, is called off-axis angle, exp represents the exponential depth taking e the end of as, and d represents array element distance, λ representation signal wavelength, [] ^trepresent the non-conjugated transposition of vector;

N _irank, the N × 1 white Gaussian noise matrix that the average that represents i reception of impulse is 0, variance is 1.

Step 4, calculates right of search vector w _i(ψ).

Search angle ψ is set near the antenna normal direction of i pulse, and according to search angle, ψ calculates right of search vector w _i(ψ):

W _i(ψ)=[1, exp (j2 π dsin ψ/λ) ..., exp (j2 π (N-1) dsin ψ/λ)] ^t, wherein, the span of search angle ψ is greater than half-power beam width, and j represents imaginary unit, and d represents array element distance, λ representation signal wavelength, N is element number of array.

Step 5, to the weight vector w described in step 4 _i(ψ) compensate.

5a) determine weight vector w _i(ψ) offset: taking first pulse as reference, the value of being compensated is that an initial value is 0, and difference is the arithmetic progression of Δ θ, and the offset of other pulse weight vector is followed successively by 0, Δ θ, 2 Δ θ ..., (i-1) Δ θ;

5b) the weight vector w to i pulse _i(ψ) compensate: taking first pulse as reference, by step 5a) obtain offset (i-1) the Δ θ of i pulse, itself and former search angle ψ are added, search angle ψ+(i-1) Δ θ after being compensated, brings the search angle after compensation into weight vector w _i(ψ), obtain i the weight vector w after impulse compensation _i(ψ+(i-1) Δ θ).

Step 6, by the echoed signal X described in step 3 _iwith the weight vector w after compensation described in step 5 _i(ψ+(i-1) Δ θ) builds vertical cost function P (ψ).

6a) calculate the search mould value P after the compensation authority vector of each pulse _i(ψ):

wherein, i=1,2 ..., L, || represent delivery value, [] ^hrepresent conjugate transpose;

6b) by the search mould value P of each pulse _i(ψ) be added, obtain cost function P (ψ):

$P\left(\mathrm{\ψ}\right)=\underset{i}{\overset{L}{\mathrm{\Σ}}}{P}_i\left(\mathrm{\ψ}\right)=\left|X_1^{H}w\left(\mathrm{\ψ}\right)\right|+\left|X_2^{H}w(\mathrm{\ψ}+\mathrm{\Δ\θ})\right|+...+\left|X_L^{H}w(\mathrm{\ψ}+(L-1)\mathrm{\Δ\θ})\right|.$

Step 7, carries out beam scanning to cost function P (ψ), measures the off-axis angle of target.

Within the scope of search angle ψ, cost function P (ψ) is carried out to beam scanning, obtain angle corresponding to beam scanning maximal value, at the off-axis angle θ of first pulse position target ₁.

Step 8, the accurate angle of calculating target.

By the off-axis angle θ in first pulse position target ₁reference angle with first pulse be added, obtain the accurate angle Φ of target, wherein

Effect of the present invention can be verified by following Computer Simulation:

One, simulated conditions

Simulated conditions 1,

If machine is swept the uniform line-array that the antenna of metric wave array radar is made up of 8 array elements, the beam angle of antenna is about 12 °, antenna is rotated scanning with the speed of 10s/r, and radar is every a pulse that frequency is 300MHz of 3ms transmitting, and antenna receives 25 pulse signals at every turn.Suppose that antenna normal aims at the mark, the true angle of target is 10 °, and the radial velocity of the relative radar of target is 50m/s, and its Doppler frequency can calculate as 100Hz.Array scanning angular range is-20 ° to 40 °, and get-5dB of signal to noise ratio (S/N ratio), to 10dB, carries out Monte Carlo Experiment 500 times.

Simulated conditions 2,

If machine is swept the uniform line-array that the antenna of metric wave array radar is made up of 8 array elements, the beam angle of antenna is about 12 °, antenna is rotated scanning with the speed of 10s/r, and radar is every a pulse that frequency is 300MHz of 3ms transmitting, and antenna receives 25 pulse signals at every turn.Suppose antenna normal misalignment target, center of antenna 4 pulses that depart from objectives.The true angle of target is 10 °, and the radial velocity of the relative radar of target is 50m/s, and its Doppler frequency can calculate as 100Hz.Array scanning angular range is-20 ° to 40 °, and get-5dB of signal to noise ratio (S/N ratio), to 10dB, carries out Monte Carlo Experiment 500 times.

Two, emulation content

Emulation 1, utilizes simulated conditions 1 to adopt the present invention and conventional beam sweeping method to carry out respectively angle measurement to target, can obtain the root-mean-square error curve that two kinds of methods change with signal to noise ratio (S/N ratio).As shown in Figure 2, in Fig. 2, horizontal ordinate is signal to noise ratio (S/N ratio), and unit is dB, and ordinate is root-mean-square error, and unit is degree.

As seen from Figure 2, in the time that center of antenna wave beam aims at the mark, the present invention is higher than conventional beam scanning arithmetic accuracy, and particularly, in the time that signal to noise ratio (S/N ratio) is low, effect is very obvious.Show that low noise impact can fall in the present invention, improve angle measurement accuracy.

Emulation 2, utilizes simulated conditions 2 to adopt the present invention and conventional beam sweeping method to carry out respectively angle measurement to target, can obtain the root-mean-square error curve of two kinds of methods, as shown in Figure 3, in Fig. 3, horizontal ordinate is signal to noise ratio (S/N ratio), and unit is dB, ordinate is root-mean-square error, and unit is degree.

As seen from Figure 3, in the time of center of antenna wave beam misalignment target, angle measurement accuracy of the present invention is still high than conventional beam scanning arithmetic accuracy, and effect is very obvious.Low noise impact still can fall in Fig. 3 explanation the present invention in the time of antenna misalignments target, improves angle measurement accuracy.

From the contrast of Fig. 3 and Fig. 2, the angle measurement accuracy of the inventive method in the time of the misalignment of center of antenna wave beam and when antenna alignment almost do not change, and whether visible the present invention is the same with conventional beam sweeping method all aims at the mark insensitive to antenna.

Claims (5)

1. machine is swept a metric wave array radar angle-measuring method, comprises the steps:

(1), when antenna scanning, at interval of a pulse of Δ θ transmitting, and will launch i pulse time, the angle of center of antenna normal and horizontal reference plane is as reference angle i=1,2 ..., L, L is the pulse number of launching altogether in a beam angle, Δ θ is the interval of adjacent two pulses;

(2) establish machine and sweep metric wave array radar antenna and have N array element, utilize this N array element to receive echoed signal, obtain the echoed signal X of i pulse _i;

(3) search angle ψ is set near the antenna normal direction of i pulse, according to search angle, ψ calculates right of search vector w _i(ψ):

w _i(ψ)＝[1,exp(j2πdsinψ/λ),...,exp(j2π(N-1)dsinψ/λ)] ^T，

Wherein, the span of search angle ψ is greater than half-power beam width, and exp represents the exponential depth taking e the end of as, and d is antenna spacing, and λ is signal wavelength, [] ^trepresent the non-conjugated transposition of vector;

(4) taking first pulse as reference pulse to weight vector w _i(ψ) compensate, after being compensated, the weight vector of i pulse is w _i(ψ+(i-1) Δ θ);

(5) according to the echoed signal X receiving _iwith the weight vector w after compensation _i(ψ+(i-1) Δ θ), builds cost function P (ψ):

$P\left(\mathrm{\ψ}\right)=\left|X_1^{H}w\left(\mathrm{\ψ}\right)\right|+\left|X_2^{H}w(\mathrm{\ψ}+\mathrm{\Δ\θ})\right|+...+\left|X_L^{H}w(\mathrm{\ψ}+(L-1)\mathrm{\Δ\θ})\right|,$ Wherein, i=1,2 ..., L, || represent delivery value, [] ^hrepresent conjugate transpose;

(6) within the scope of search angle ψ, cost function P (ψ) is carried out to beam scanning, obtain the off-axis angle θ of target in the time of first pulse of transmitting ₁, by off-axis angle θ ₁reference angle with first pulse be added, obtain the accurate angle Φ of target, wherein

2. sweep metric wave array radar angle-measuring method according to the machine described in claims 1, it is characterized in that, set N array element in described step (2), adopt uniform line-array, be that array element distance d between any two adjacent array elements all equates, and the half of the wavelength X transmitting for metre wave radar, d=λ/2.

3. sweep metric wave array radar angle-measuring method according to the machine described in claims 1, it is characterized in that, the echoed signal X of i pulse of described step (2) _i, its expression is:

X _i＝S _i×a(θ _i)+n _i，i＝1,2,...,L，

Wherein, S _irepresent the complex envelope information of i pulse signal, s ₀for initial complex amplitude, j represents imaginary unit, f _drepresent the Doppler frequency of target, v represents the radial velocity of target with respect to radar, f ₀the centre frequency that represents radar emission signal, c represents the light velocity, t represents sampling interval;

A (θ _i) be the steering vector of i pulse:

A (θ _i)=[1, exp (j2 π dsin θ _i/ λ) ..., exp (j2 π (N-1) dsin θ _i/ λ)] ^t, θ _irepresent that target, with respect to the angle between antenna normal, is called off-axis angle, exp represents the exponential depth taking e the end of as, and d represents array element distance, λ representation signal wavelength, [] ^trepresent the non-conjugated transposition of vector;

N _irank, the N × 1 white Gaussian noise matrix that the average that represents i reception of impulse is 0, variance is 1.

4. machine according to claim 1 is swept metric wave array radar angle-measuring method, it is characterized in that, in described step (4) taking first pulse as reference pulse to weight vector w _i(ψ) compensate, carry out as follows:

4a) determine the offset of weight vector: taking first pulse as reference, the value of being compensated is that an initial value is 0, and difference is the arithmetic progression of Δ θ, and the offset of every subpulse is followed successively by 0, Δ θ, 2 Δ θ ..., (i-1) Δ θ;

4b) weight vector is compensated: taking first pulse as reference, utilize the offset obtaining that the right of search vector of each pulse is normalized to first pulse weight vector position, obtain i the weight vector w after impulse compensation _i(ψ+(i-1) Δ θ).

5. machine according to claim 1 is swept metric wave array radar angle-measuring method, it is characterized in that, step (5) described according to the echoed signal X receiving _iwith the weight vector w after compensation _i(ψ+(i-1) Δ θ), builds cost function P (ψ), carries out as follows:

5a) calculate the search mould value P after the compensation authority vector of each pulse _i(ψ):

wherein, i=1,2 ..., L, || represent delivery value, [] ^hrepresent conjugate transpose.

5b) by the search mould value P of each pulse _i(ψ) be added, obtain cost function P (ψ):

$P\left(\mathrm{\ψ}\right)=\underset{i}{\overset{L}{\mathrm{\Σ}}}{P}_i\left(\mathrm{\ψ}\right)=\left|X_1^{H}w\left(\mathrm{\ψ}\right)\right|+\left|X_2^{H}w(\mathrm{\ψ}+\mathrm{\Δ\θ})\right|+...+\left|X_L^{H}w(\mathrm{\ψ}+(L-1)\mathrm{\Δ\θ})\right|.$