CN101887120B - Method for measuring target azimuth by single-beam mechanical scanning radar - Google Patents

Abstract

The invention discloses a method for measuring a target azimuth by single-beam mechanical scanning radar, which relates to the technical field of radar and communication and solves the problems of low angle measurement precision and large operation amount of the conventional single-beam mechanical scanning radar. The method comprises the following steps of: acquiring echo signals by using the single-beam mechanical scanning radar, then performing phase coherence accumulation on the acquired echo signals to acquire a higher signal detection signal-to-noise ratio, taking an azimuth interval of any two echo pulses of a main lobe width of a radar antenna as two beams required for measuring an angle by the single-pulse technology after target information is detected, then calculating two-dimensional images, sum signal intensity and difference signal intensity of a target on two azimuths, and further calculating a sum-to-difference ratio k so as to acquire a target error deflection angle delta theta, wherein the target azimuth theta T is equal to theta i + theta k + delta theta. The method is suitable for radar angle measurement.

Description

A kind of method that is used for measuring target azimuth by single-beam mechanical scanning radar

Technical field

The present invention relates to radar, communication technique field, be specifically related to a kind of method that is used for measuring target azimuth by single-beam mechanical scanning radar.

Background technology

The single beam mechanical scanning radar is often used in detection channels, search radar and the all-round looking radar of New System imaging radar inverse synthetic aperture radar (ISAR), and its traditional angle-measuring method adopts amplitude of vibration method, comprises maximum-signal method, crosses thresholding detection method etc.Maximum-signal method is exactly an echo strength relatively one by one, gets wherein that the amplitude maximal value is the DOA estimation center, and this method realizes simple, but since near the wave beam maximal value smooth angle measurement accuracy also can reduce, make more also that one by one calculated amount significantly increases simultaneously; A kind of implementation method when crossing the thresholding detection method and be maximum-signal method and being used for automatic angle measurement; Its basic ideas are to utilize the symmetry of antenna; With echoed signal during above and below detection threshold the mean value in two orientation as the DOA estimation center; Have the big shortcoming of calculated amount equally, the randomness of noise also has considerable influence to check point simultaneously.

In the modern radar system, particularly under the ISAR detection channels pattern, accurate azimuth information will help the quick location of the antenna under the imaging pattern, the fast selecting of data segment, and the redundant data of minimizing driftlessness period is to improve the real-time of data processing.To the target following in later stage, the flight path extrapolation all is vital.But traditional single beam mechanical scanning radar angle measurement accuracy can not get improving always; Modern signal processing adopts orthogonal double channels to handle; After the coherent accumulation, can obtain the high s/n ratio echo, make monopulse method become possibility in the reconnaissance probe Application in Radar with higher angle measurement accuracy.

What monopulse technology adopted is while lobe method, and its most significant advantage is that its angle measurement accuracy is high, is widely used in phased-array radar at present, and the modern precision tracking radar.For the single beam mechanical scanning radar, monopulse technology can not directly be used, and needs suitable improvement.

Summary of the invention

In order to solve the problem that existing single beam mechanical scanning radar angle measurement accuracy is not high and operand is big, the invention provides a kind of method that is used for measuring target azimuth by single-beam mechanical scanning radar.

A kind of method that is used for measuring target azimuth by single-beam mechanical scanning radar of the present invention, it comprises the steps:

Step 1: utilize the single beam mechanical scanning radar to obtain echoed signal, and then carry out target detection;

Step 2: in the azimuth coverage that detects the target existence, getting azimuthal separation is radar antenna main lobe width 2 θ _kAny two echo-pulses as two required wave beams of monopulse technology angle measurement;

Step 3: be the center with the echo-pulse on two orientation of being got in the step 2 respectively, and P adjacent with each echo-pulse of being got respectively pulse carry out coherent accumulation, and the orientation values that defines one of them echo-pulse pulse place is θ _i, the orientation values at another echo-pulse place is θ _i+ 2 θ _k, obtaining orientation values then is θ _iThe time target surveyed two-dimensional image echo strength F (θ _i) and orientation values be θ _i+ 2 θ _kThe time target surveyed two-dimensional image echo strength F (θ _i+ 2 θ _k), wherein, P is a natural number;

Step 4: calculate target on said two position angles according to the two-dimensional image echo strength of target on two position angles that obtained with signal intensity F _Σ(θ)=F (θ _i)+F (θ _i+ 2 θ _k), difference signal intensity F _Δ(θ)=F (θ _i)-F (θ _i+ 2 θ _k) and and difference ratio

Step 5: utilize look-up table to search and differ from the pairing error of ratio k drift angle δ θ, obtain azimuth of target θ _T=θ _i+ θ _k+ δ θ.

Beneficial effect of the present invention is: the invention provides a kind of new method that is used for the angle measurement of single beam mechanical scanning radar based on monopulse technology; The present invention has introduced monopulse technology, has improved measuring accuracy; The present invention can choose two 2 θ of being separated by arbitrarily from a plurality of wave beams that detect target _kWave beam can constitute needed two wave beams of monopulse angle measurement; Handle more flexible when making angle measurement; And can obtain two corresponding position angles of wave beam through tabling look-up, and need be as maximum-signal method and Threshold detection method echo strength relatively one by one, obtain maximal value; The value that thresholding perhaps occurs being lower than could be confirmed the orientation, makes calculated amount little; Because the directional diagram top distortion that factor such as target fluctuation variation may cause, and cause measured value to depart from true bearing and produce the situation of angle error when the present invention has avoided the maximum-signal method angle measurement, utilize the monopulse technology angle measurement to have stability preferably.

Description of drawings

Fig. 1 is a kind of method flow diagram that is used for measuring target azimuth by single-beam mechanical scanning radar of the present invention; Fig. 2 is a while lobe method monopulse technology principle schematic; Fig. 3 is the course of work synoptic diagram of single beam mechanical scanning radar; Fig. 4 is antenna radiation pattern 2 θ of being separated by during with Gaussian approximation _kThe signal intensity synoptic diagram of two wave beams; Fig. 5 be antenna radiation pattern during with Gaussian approximation two wave beams with the signal intensity synoptic diagram, Fig. 6 is the difference signal intensity synoptic diagram of antenna radiation pattern two wave beams during with Gaussian approximation; Fig. 7 is antenna radiation pattern two wave beams and the numerical value synoptic diagram difference ratio k during with Gaussian approximation; Fig. 8 is the comparison synoptic diagram of angle measurement of the present invention and classic method angle measurement accuracy, and wherein, I represented thresholding detection method angle measurement result curve, and II representes monopulse technology angle measurement result curve of the present invention, and III representes maximum-signal method angle measurement result curve; Fig. 9 is that the antenna radiation pattern that genuine measured data is compared with wave beam Gaussian approximation data is lost at the top; Wherein, IV representes that the wave beam top loses genuine measured data result curve, the signal intensity maximum value position X (137.6426 of said curve IV; 1); V representes wave beam Gaussian approximation data result curve, the signal intensity maximum value position Y (137.7634,1) of said curve V.

Embodiment

Embodiment one: specify this embodiment according to Figure of description 1, the described a kind of method that is used for measuring target azimuth by single-beam mechanical scanning radar of this embodiment, it comprises the steps:

Step 1: utilize the single beam mechanical scanning radar to obtain echoed signal, and then carry out target detection;

Step 2: in the azimuth coverage that detects the target existence, getting azimuthal separation is radar antenna main lobe width 2 θ _kAny two echo-pulses as two required wave beams of monopulse technology angle measurement;

Step 3: be the center with the echo-pulse on two orientation of being got in the step 2 respectively, and P adjacent with each echo-pulse of being got respectively pulse carry out coherent accumulation, and the orientation values that defines one of them echo-pulse pulse place is θ _i, the orientation values at another echo-pulse place is θ _i+ 2 θ _k, obtaining orientation values then is θ _iThe time target surveyed two-dimensional image echo strength F (θ _i) and orientation values be θ _i+ 2 θ _kThe time target surveyed two-dimensional image echo strength F (θ _i+ 2 θ _k), wherein, P is a natural number;

Step 4: calculate target on said two position angles according to the two-dimensional image echo strength of target on two position angles that obtained with signal intensity F _Σ(θ)=F (θ _i)+F (θ _i+ 2 θ _k), difference signal intensity F _Δ(θ)=F (θ _i)-F (θ _i+ 2 θ _k) and and difference ratio

Step 5: utilize look-up table to search and differ from the pairing error of ratio k drift angle δ θ, obtain azimuth of target θ _T=θ _i+ θ _k+ δ θ.

Embodiment two:, this embodiment is that in step 2, radar antenna is a receiving antenna in the embodiment one, said radar antenna main lobe width 2 θ to the further specifying of embodiment one _k=θ _0.5, wherein, θ _0.5Antenna half-power point main lobe width during for one way.

Embodiment three: this embodiment is that in step 2, radar antenna is a duplexer in the embodiment one, said radar antenna main lobe width to the further specifying of embodiment one

Wherein, θ _0.5Antenna half-power point main lobe width during for one way.

The implementation of present embodiment is based on the monopulse technology proposition, utilizes the coherent accumulation can obtain higher signal to noise ratio, with the convenient target information that detects.Fig. 2 is a while lobe method monopulse technology principle schematic, and what it adopted is two identical and partly overlapping each other wave beams, and wherein, OA is for waiting signal shaft, and counterparty's parallactic angle is θ ₀, OB and OC are respectively the antenna axis of two wave beams, they and etc. the angle between the signal shaft OA be θ _kThe pairing orientation angles of target is θ _tTransmit and echoed signal is modulated by two lobes simultaneously, when target appeared at the OA direction, echoed signal intensity equated; When target departs from the OA direction, will produce an error deviation angle, the position angle according to OA obtains position angle, target place again.The method of extraction error drift angle δ θ adopts and is poor than width of cloth method.

Can be approximated to the linear function of error drift angle with difference ratio

$\frac{F_{\mathrm{\Δ}}\left(\mathrm{\θ}\right)}{F_{\mathrm{\Σ}}\left(\mathrm{\θ}\right)}=\mathrm{l\δ\θ}---\left(1\right)$

Wherein, δ θ=θ _t-θ ₀Be the error drift angle; L is a scale-up factor, when θ δ is very little,

F (θ) is the antenna radiation pattern approximate function.

Fig. 3 is the principle of work synoptic diagram of single beam mechanical scanning radar, and hypothetical target is T, sweeps with the angular velocity omega ring, and establishing wave beam, to rotate to the position angle be θ _iThe time detect target because the low speed of target, antenna rotation rate is slow, rotating to the position angle through N stepping antenna is θ _I+NTarget T is left at the place.The position angle of the antenna present position after each antenna stepping therebetween is designated as θ _I+1, θ _I+2..., θ _I+N, the angle between diverse location is expressed as

To present embodiment, carry out theory analysis to improving certainty of measurement:

By the decision of Cramer-Rao boundary, when supposing that single target exists, radar carries out parameter estimation to the orientation to the highest measurement precision of radar (not having the partially effectively least estimated variance of estimator) in the interested time.When the form of estimator was the linear function of observation echo, its estimation variance was minimum.Based on the relevant derivation under radar assumed condition and the antenna radiation pattern modulating characteristic, the Cramer-Rao criterion can be written as

${\mathrm{\&sigma;}}_{\widehat{\mathrm{\&theta;}}}^2\&GreaterEqual;\frac{1}{\left({2/N}_0\right){\mathrm{<figure-callout\; id="2"\; label="K"\; filenames="HSA00000148929700032.png,HSA00000148929700041.png"\; state="\{\{state\}\}">K</figure-callout>}}^2\mathrm{NE}}=\frac{1}{{\mathrm{<figure-callout\; id="2"\; label="K"\; filenames="HSA00000148929700032.png,HSA00000148929700041.png"\; state="\{\{state\}\}">K</figure-callout>}}^2\mathrm{NR}}={\mathrm{\&sigma;}}_{\widehat{\mathrm{\&theta;}}\min }^2---\left(2\right)$

Wherein, E representes the echoed signal energy;

is defined as the output signal-to-noise ratio of matched filtering under the white noise, and

is defined as difference slope.Formula (2)

Show that the precision of DOA estimation is by echoed signal signal to noise ratio (S/N ratio) and the decision of antenna difference slope.The signal to noise ratio (S/N ratio) of echoed signal can realize through coherent accumulation, and the antenna difference slope often determines by antenna itself, for while lobe method, the antenna difference slope also with θ _kRelevant, θ _kTake into account angle measurement accuracy and signal to noise ratio (S/N ratio), because θ _kBig more, the antenna difference slope is big more, and precision is high more, but under the identical situation of emissive power, the echo signal to noise ratio (S/N ratio) can descend to some extent.Following analysis earlier θ when guaranteeing the maximum antenna difference slope _kValue.

Antenna radiation pattern adopts Gaussian function approximate, considers the transmitting-receiving round trip, and the normalization directivity function of antenna is written as

$F\left(\mathrm{\&theta;}\right)=e^{-2.78\frac{{\mathrm{\&theta;}}^2}{{\mathrm{\&theta;}}_{0.5}^2}}---\left(3\right)$

Wherein, θ _0.5Antenna main lobe width during for one way, then main lobe width does during round trip For guaranteeing the maximum antenna difference slope, require and beam signal intensity F _Σ(θ) at θ=θ ₀The place obtains maximum value, promptly need satisfy ${F_{\mathrm{\&Sigma;}}}^{\&prime;}\left(\mathrm{\&theta;}\right){|}_{\mathrm{\&theta;}={\mathrm{\&theta;}}_0}=0,{F_{\mathrm{\&Sigma;}}}^{\&prime;\&prime;}\left(\mathrm{\&theta;}\right){|}_{\mathrm{\&theta;}={\mathrm{\&theta;}}_0}<0,$ Ask under this condition $K_{\mathrm{Max}}=F_{\mathrm{\&Delta;}}^{\&prime;}\left(\mathrm{\&theta;}\right){|}_{\mathrm{\&theta;}={\mathrm{\&theta;}}_0}$ The time θ _kValue, have

${2\mathrm{\&theta;}}_k=\sqrt{\frac{{2\mathrm{\&theta;}}_{0.5}^2}{2.78}}\&ap;1.195\frac{{\mathrm{\&theta;}}_{0.5}}{\sqrt{2}}=1.195{\mathrm{\&theta;}}_{\mathrm{dual}0.5}---\left(4\right)$

Formula (4) Show that antenna is under the situation of transmitting-receiving round trip, the antenna difference slope was got maximal value when the angle between two wave beams was 1.2 times of round trip beam angle, had maximum angle measurement accuracy, and power attenuation this moment is about-4.43dB.

Take all factors into consideration in the above-mentioned implementation and get 2 θ _k=θ _0.5, taken into account signal to noise ratio (S/N ratio), obtained higher angle measurement accuracy theoretically.In the single beam mechanical scanning radar, angle measurement accuracy improvement is preferably arranged for traditional maximum-signal method angle measurement.

To this embodiment, carry out instance analysis:

Obtain the measured data of echoed signal according to the single beam mechanical scanning radar, said measured data amounts to 18 groups, is the example analysis with wherein data segment data3.Antenna one way main lobe width is θ _0.5=1.1 °, because antenna receiving-sending is shared, so the round trip main lobe width is θ _Dual0.5=0.778 °.Antenna radiation pattern is approximate with Gaussian function, and accumulation umber of pulse P gets 32.

At first echoed signal is carried out one dimension image distance tripping and contract, do the coherent accumulation, when detecting target, note its orientation values as the first wave beam θ with P=32 _i=61.6412 °, 2 θ at interval then _kObtaining another second wave beam orientation is θ _i+ 2 θ _k=62.4899 ° is the center with the pulse at place, 62.4899 ° of orientation, get backward forward respectively 16 totally 32 pulses do the coherent accumulation, read two orientation two-dimensional image echo strength F (θ respectively _i)=1.0691 * 10 ⁶, F (θ _i+ 2 θ _k)=3.0039 * 10 ⁵, then obtain and differ to compare 1 obtain target T and estimate that the orientation is θ through tabling look-up _T=62.3916 °.

Table 1 obtain during for Gaussian approximation with difference ratio k and corresponding error drift angle δ θ, get in the main lobe width-0.5 to 0.5 temporarily and whenever get one at a distance from 0.01, totally 101 numbers; In the practical application; If be taken as 0.001 at interval, will be 1000 numbers in the table then, if obtain littler at interval; Then possibly count more, but also more accurate.

Under table 1 Gaussian approximation with difference ratio k and corresponding error drift angle δ θ

With regard to this embodiment the advantage in this embodiment is described one by one below:

Because in practical engineering application, be spaced apart 2 θ _kTwo wave beams choose arbitrarily, so the dirigibility in order to verify that this is technological, 2 θ of in the antenna main lobe width, being separated by arbitrarily _kThe processing of two wave beams all result preferably can be arranged, we can be at θ _iThe basis on add that 0.1 ° of a little stepping (can suitably select according to the main lobe width of antenna) obtains corresponding orientation, is assumed to be θ _I+x, repeating step one to five draws center, the target azimuth θ of this moment _T2According to this, obtain the orientation θ of other stepped intervals _T3, θ _T4, θ _T5

At last above-mentioned to target T DOA estimation θ _T, θ _T2, θ _T3The basis on ask statistical average, as the estimation orient core θ of final goal T _T, and make comparisons with other estimated values.

Each time measured value in the table 2 target T main lobe width

Ask its statistical average to obtain the orient core estimated values theta according to table 2 _A=62.4241 °, by Table

Can find out wherein to differ and also have only 0.02 °, therefore can find out to handle to have obtained angle measurement accuracy preferably with the average maximum.

Obtaining its orient core respectively for the identical step of other The data is:

Utilize maximum-signal method respectively, cross the thresholding detection method and obtain corresponding orient core,, can do as drawing a conclusion by Fig. 8 like Fig. 8:

1. with respect to monopulse technology and maximum-signal method, cross the thresholding detection method and receive the influence of target fluctuation bigger, so the monopulse technology angle measurement has stability preferably.

2. maximum-signal method and monopulse technology have suitable precision, but have better superiority for the target monopulse technology of directional diagram top irregularity.Give an example wherein to differ maximum data17, as shown in Figure 9, because the distortion of directional diagram top; Maximal value receives the influence of factors such as noise, target fluctuation and has departed from the center, target azimuth, and maximum-signal method angle measurement result is 137.7634 °, and the monopulse technology result is 137.6480 °; Associative list 3 each time stepping estimated values; With respect to estimating that the center maximum error also only has 0.0245 °, obviously improved the accuracy in orientation, stability obviously improves.

Table 3Data17 each stepping estimated value in main lobe width

Claims (3)

1. a method that is used for measuring target azimuth by single-beam mechanical scanning radar is characterized in that it comprises the steps:

Step 1: utilize the single beam mechanical scanning radar to obtain echoed signal, and then carry out target detection;

Step 2: in the azimuth coverage that detects the target existence, getting azimuthal separation is radar antenna main lobe width 2 θ _kAny two echo-pulses as two required wave beams of monopulse technology angle measurement;

Step 3: be the center with the echo-pulse on two orientation of being got in the step 2 respectively, and P adjacent with each echo-pulse of being got respectively pulse carry out coherent accumulation, and the orientation values that defines one of them echo-pulse place is θ _i, the orientation values at another echo-pulse place is θ _i+ 2 θ _k, obtaining orientation values then is θ _iThe time target surveyed two-dimensional image echo strength F (θ _i) and orientation values be θ _i+ 2 θ _kThe time target surveyed two-dimensional image echo strength F (θ _i+ 2 θ _k), wherein, P is a natural number;

Step 4: calculate target on said two position angles according to the two-dimensional image echo strength of target on two position angles that obtained with signal intensity F _∑(θ)=F (θ _i)+F (θ _i+ 2 θ _k), difference signal intensity F _Δ(θ)=F (θ _i)-F (θ _i+ 2 θ _k) and and difference ratio

Step 5: utilize look-up table to search and differ from the pairing error of ratio k drift angle δ θ, obtain azimuth of target θ _T=θ _i+ θ _k+ δ θ.

2. a kind of method that is used for measuring target azimuth by single-beam mechanical scanning radar according to claim 1 is characterized in that in step 2 radar antenna is a receiving antenna, said radar antenna main lobe width 2 θ _k=θ _0.5, wherein, θ _0.5Antenna main lobe width during for one way.

3. a kind of method that is used for measuring target azimuth by single-beam mechanical scanning radar according to claim 1 is characterized in that in step 2 radar antenna is a duplexer, said radar antenna main lobe width

Wherein, θ _0.5Antenna main lobe width during for one way.

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