CN104977571A - Distance blur clutter suppression method based on pitch frequency diversity STAP - Google Patents

Abstract

The invention discloses a distance blur clutter suppression method based on pitch frequency diversity STAP. The method comprises the steps that down-conversion and matched filtering are sequentially carried out on a detected received signal to sequentially acquire the pitch-azimuth-time three-dimensional clutter snapshot model of each range gate, the pitch frequency expression of each range gate and the corresponding clutter compensation item; an appropriate clutter compensation item is used to separate distance blur clutters of different distance rings; due to the fact that pitch frequencies of different distance blur clutters are separated from each other, the distance blur clutter of each distance ring needs a filter with corresponding coefficients for filtering, and then all distance blur clutters are inhibited to solve the problem of distance blur; and finally, after the pitch distance blur clutters are separated, pitch frequency spectrum distribution and digital frequency periodicity are used to acquire the selection criteria of frequency increment. According to the invention, the freedom of a system and the operation complexity are not increased.

Description

Based on the range ambiguity clutter suppression method of pitching frequency diversity STAP

Technical field

The invention belongs to the Clutter Rejection Technique field of radar signal, in particular to a kind of range ambiguity clutter suppression method based on pitching frequency diversity STAP, namely based on pitching frequency diversity space-time adaptive process (Space-Time AdaptiveProcessing, STAP) range ambiguity clutter suppression method, is mainly applicable to separation and the suppression of the fuzzy clutter of Practical Project middle distance.

Background technology

In recent years, the Ground moving targets detection (Ground Moving Target Indication, GMTI) of airborne/spaceborne radar system attracts wide attention in each side such as urban transportation control and target following detections; For the application background of the strong clutter of airborne/spaceborne radar, under particularly there is the application background of ground unrest and interference, Chinese scholars proposes space-time adaptive process (STAP) algorithm and corresponding innovatory algorithm thereof, the starting point of these algorithms is based on 2 points: the first, can moving-target be detected in strong land clutter; The second, estimate the parameter obtaining target, as speed and exact position.Therefore, space-time adaptive process (STAP) algorithm and corresponding innovatory algorithm thereof by studying and combining hyperchannel and multipulse signal processing method, thus reach and target are identified from clutter with disturbing in the associating territory of spatial domain and time domain.

In the automatic detection of radar, usually need the covariance matrix estimating unknown clutter background, the auxiliary data not comprising target that in reality, in general and unknown clutter, unit under test is contiguous, the clutter covariance matrix of position is estimated, clutter covariance matrix realizes the indispensable condition of adaptive weight, and clutter covariance matrix is produced by the second training data of test cell usually, and several adjacent cells of unit under test in clutter are got rid of, prevent certainly disappearing mutually of target.

Traditional space-time adaptive process (STAP) algorithm generally adopts the mode being fixed weights in pitching dimension by after face battle array synthesis linear array, in azimuth dimension and time domain dimension, self-adaptive processing is with clutter reduction, i.e. Space time pattern (2D-STAP); But when there is array element error, the directional diagram of each row submatrix pitching dimension synthesis is different, if only in pitching to being fixed weights, clutter spectrum generation diffusion phenomena will be caused, and be difficult to eliminate the clutter with a large amount of range ambiguity completely.

On the high speed motion platforms such as airborne/spaceborne radar, the serious doppler ambiguity caused in order to avoid Doppler frequency propagation, during actual hollow, self-adaptive processing (STAP) algorithm adopts high pulse repetition frequency (High Pulse RepetitionFrequence usually, HPRF), high pulse repetition frequency (HPRF) is seriously fuzzy in distance, not fuzzy in speed, good to high-speed target detection perform, the more difficult acquisition of the secondary data of test cell can be made; Seriously, except positive side-looking radar, array radar can produce Range-dependent problem, independent same distribution (the Independent and IdenticallyDistributed of clutter cannot be met, IID) condition, except non-pre-published carries out corresponding pre-service, otherwise self-adaptive processing cannot be carried out.And the range ambiguity that high pulse repetition frequency (HPRF) brings usually can make the heterogeneity of clutter increasing; Such as, what first range ambiguity ring represented is land, and second range ambiguity ring may describe is sea level, the clutter like this with different statistic can superpose in distance, these complex situations produce mistake when can cause estimating clutter covariance matrix, and cause the performance serious degradation of space-time adaptive process (STAP) algorithm.Therefore, the serious range ambiguity problem that the high pulse repetition frequency (HPRF) in solution space-time adaptive process (STAP) algorithm causes just seems particularly important.

Summary of the invention

The object of the invention is to overcome above-mentioned the deficiencies in the prior art, propose a kind of range ambiguity clutter suppression method based on pitching frequency diversity space-time adaptive process (Space-Time Adaptive Processing, STAP).

Realization approach of the present invention is: assuming that use high pulse repetition frequency (HPRF) to alleviate pitching frequency diversity array (Frequency Diverse Array, during range ambiguity clutter process FDA) in radar system, the pitch channel of this radar system also have passed through Wave beam forming process; First after down coversion, matched filtering process being carried out successively to the Received signal strength detected, obtain the pitching-orientation of each range gate-time three-dimensional clutter snap model, the pitching frequency expression of each range gate and corresponding clutter compensation term successively, then suitable clutter compensation term is used to be separated by the fuzzy clutter of different distance of pitching frequency diversity array (Frequency DiverseArray, FDA) radar; Because the pitching frequency of the fuzzy clutter of different distance is separated from each other, after making each range ambiguity ring clutter need specific filter to carry out filtering process respectively, just can complete the suppression of each range ambiguity ring clutter, and then solve range ambiguity problem; Finally, after pitching range ambiguity clutter is separated, just can adopts distribution and the number periodicity frequently of pitching frequency spectrum, obtain the choice criteria of frequency increment, and the present invention can not increase the complexity of degree of freedom in system and computing.

In order to realize above-mentioned technical purpose, the present invention adopts following technical scheme to be achieved.

Based on a range ambiguity clutter suppression method of pitching frequency diversity STAP, it is characterized in that, comprise the following steps:

Step 1, sets up Air-borne Forward-looking battle array radar system, and this Air-borne Forward-looking battle array radar system is pitching frequency diversity array radar, and this pitching frequency diversity array radar is the capable N array structure of M, namely has M transmission channel, N number of receiving cable.

Step 2, suppose that every a line array element of pitching frequency diversity array radar launches orthogonal signal, the equivalent phase center of its orthogonal signal is the mid point of corresponding row; In all receiving cables of pitching frequency diversity array radar, after down coversion, matched filtering process are carried out successively to the Received signal strength detected, obtain pitching frequency diversity array radar m transmission channel and transmit and the echoed signal r of a kth pulse by the n-th receiving cable Received signal strength _{m, n, k}, wherein, m ∈ 1,2 ..., M}, n ∈ { 1,2 ..., N}, M represent the total number of transmission channel, and N represents the total number of receiving cable, and M, N is positive integer, umber of pulse k ∈ 1,2 ..., K}, K represent the total number of each coherent processing interval (CPI) period transponder pulse.

Step 3, according to the echoed signal that step 2 obtains obtain pitching-orientation-time three-dimensional clutter snap model c of l range gate _l, and three-dimensional clutter snap model c thus _lobtain, when there is range ambiguity in pitching frequency diversity array radar, the pitching frequency expression of l range gate and corresponding clutter compensation term h _c(R _l), according to this clutter compensation term h _c(R _l) to the pitching-orientation of each range gate-time three-dimensional clutter snap model c _lafter compensating, obtain successively m transmission channel repay after clutter data expression formula clutter data expression formula after this compensation corresponding normalization pitching frequency wherein, K represents the total number of coherent processing interval (CPI) period transponder pulse, k ∈ 1,2 ..., K}, M represent the total number of transmission channel, m ∈ 1,2 ..., M}, N represent the total number of receiving cable, n ∈ { 1,2,, N}, each transponder pulse has L range gate, l ∈ 1,2 ..., L}.

Step 4, the normalization pitching frequency corresponding according to m transmission channel design ratio is pre--STAP wave filter, and utilize this pre--STAP wave filter to normalization pitching frequency in range ambiguity clutter be separated, then Wave beam forming is carried out to the output of pre--STAP wave filter, obtains Wave beam forming expression formula, and the removal of range ambiguity clutter is carried out to this Wave beam forming expression formula, complete the range ambiguity clutter recognition in rang ring; Wherein, pre--STAP number of filter is equal with range ambiguity number of rings order, namely in advance-STAP number of filter p ∈ 1,2 ..., N _a, N _arepresent the rang ring number that each clutter block contains, N _aalso pre--STAP number of filter is represented.

Beneficial effect of the present invention is: the range ambiguity clutter of its respective distances ring, by the characteristic of research pitching frequency diversity array (FDA) radar signal in pitching frequency domain, can be separated by (1); (2) after pitching frequency being compensated, just clutter can be used to compensate when range ambiguity clutter does not exist and mutually interferes, and then improve target detection performance, and obtain fuzzy parameter estimation; (3) because range ambiguity clutter can be separated by the present invention, the present invention is made also can to suppress non-homogeneous clutter; (4) the present invention is not only applicable to the forward sight battle array geometry scheme in case, is applicable to any array geometry scheme yet; (5) space-time adaptive process (STAP) method of use pitching frequency diversity array (FDA) radar of the present invention's proposition is different from traditional space-time adaptive process (STAP), and the present invention lays particular emphasis on the characteristic and then separation and suppression range ambiguity clutter of studying pitching frequency diversity array (FDA) radar.

Accompanying drawing explanation

Below in conjunction with the drawings and specific embodiments, this is described in further details.

Fig. 1 is the flow chart of steps that pitching frequency diversity array (FDA) radar carries out space-time adaptive process (STAP) and processes; Wherein, p is number of filter;

Fig. 2 (a) is airborne radar forward sight battle array geometry scheme illustraton of model selected by the present invention,

The array structure schematic diagram of Fig. 2 (b) pitching frequency diversity array (FDA) radar selected by the present invention;

Wherein, in three-dimensional system of coordinate x-y-z, pitching frequency diversity array (FDA) radar array is the capable N row of M, namely this radar array has M transmission channel, N number of receiving cable, array element distance is d, and podium level is H, and movement velocity is V, each coherent processing interval (CPI) period amounts to launches K pulse, and this pulse repetition rate is defined as f _r=1/T _r, each transponder pulse has L range gate, and each range gate is by N _athe clutter block composition of individual statistical iteration; Use same carrier frequency with a line array element, transmitting carrier frequency follows change, and carrier frequency is respectively f ₁, f ₂..., f _m, 1,2 ..., which transmission channel M represents respectively, T _rthe indicating impulse repetition period, R ₀to represent in pitching frequency diversity array (FDA) radar array the distance of first array element to q clutter block, q ∈ 1,2 ..., N _c, θ represents platform position angle, represent the platform angle of pitch;

Fig. 3 is the Wave beam forming process flow diagram of the n-th row Received signal strength in pitching frequency diversity array (FDA) radar;

Fig. 4 is the pitching curve of frequency distribution figure of pitching frequency diversity array (FDA) radar;

Fig. 5 (a) is the initial value scatter chart of the pitching frequency of pitching frequency diversity array (FDA) radar;

Fig. 5 (b) is the normalized value scatter chart of the pitching frequency of pitching frequency diversity array (FDA) radar;

Fig. 6 is the clutter data expression formula corresponding normalization pitching curve of frequency distribution figure after the present invention compensates;

Fig. 7 is the clutter spectrum and range ambiguity curve synoptic diagram that utilize the present invention when distance is respectively 6200m, 7000m, 10000m;

Fig. 8 (a) is for utilizing the present invention at the Space-time domain clutter spectrum schematic diagram of single range gate;

Fig. 8 (b) is for utilizing the present invention at the Space-time domain clutter spectrum schematic diagram of all range gate;

Fig. 9 is the clutter spectrum schematic diagram of traditional phased-array radar in pitching-distance domain;

Figure 10 (a) is pitching frequency diversity array (FDA) radar of the present invention pitching after pitching frequency compensation-distance domain clutter spectrum schematic diagram;

Figure 10 (b) is pitching frequency diversity array (FDA) radar of the present invention pitching after normalization pitching frequency compensation-distance domain clutter spectrum schematic diagram, wherein, horizontal ordinate is oblique distance, and unit is km, and ordinate is the normalization pitching frequency of m transmission channel;

The range ambiguity clutter spectrum schematic diagram that Figure 11 (a) is separated for pitching frequency diversity array (FDA) radar of the present invention 1st rang ring;

The range ambiguity clutter spectrum schematic diagram that the 2nd rang ring that Figure 11 (b) is pitching frequency diversity array (FDA) thunder of the present invention is separated;

The range ambiguity clutter spectrum schematic diagram that Figure 11 (c) is separated for pitching frequency diversity array (FDA) radar of the present invention 3rd rang ring;

The range ambiguity clutter spectrum schematic diagram that Figure 11 (d) is separated for pitching frequency diversity array (FDA) radar of the present invention 4th rang ring;

Figure 12 is the clutter spectrum schematic diagram after first rang ring including range ambiguity clutter utilizes the present invention to carry out clutter compensation.

Embodiment

With reference to Fig. 1, for pitching frequency diversity array (FDA) radar of the present invention carries out the flow chart of steps that space-time adaptive process (STAP) processes, should based on pitching frequency diversity space-time adaptive process (Space-Time Adaptive Processing, STAP) range ambiguity clutter suppression method, comprises the following steps:

Step 1, sets up Air-borne Forward-looking battle array radar system, and this Air-borne Forward-looking battle array radar system is pitching frequency diversity array radar, and this pitching frequency diversity array radar is the capable N array structure of M, namely has M transmission channel, N number of receiving cable.

Particularly, with reference to Fig. 2, in three-dimensional system of coordinate x-y-z, pitching frequency diversity array (FDA) radar array is the capable N row of M, and namely this radar array has M transmission channel, N number of receiving cable, and array element distance is d, podium level is H, movement velocity is V, and each coherent processing interval (CPI) period amounts to launches K pulse, and this pulse repetition rate is defined as f _r=1/T _r, each transponder pulse has L range gate, and each range gate is by N _athe clutter block composition of individual statistical iteration; T _rthe indicating impulse repetition period, R ₀to represent in pitching frequency diversity array (FDA) radar array the distance of first array element to q clutter block, q ∈ 1,2 ..., N _c, θ represents platform position angle, represent the platform angle of pitch; Launch array element with a line and use same carrier frequency, transmitting carrier frequency follows change, and carrier frequency is respectively f ₁, f ₂..., f _m..., f _m, m ∈ 1,2 ..., M}, f _mrepresent m transmission channel carrier frequency, its computing formula is as follows:

f _m＝f ₀+(m-1)△f,m＝1,2,…,M (1)

Wherein, f ₀represent with reference to carrier frequency, setting f ₁=f ₀, △ f represents the frequency increment of pitching frequency diversity array radar, and △ f<<f ₀.

Step 2, suppose that every a line array element of pitching frequency diversity array radar launches orthogonal signal, the equivalent phase center of its orthogonal signal is the mid point of corresponding row; In all receiving cables of pitching frequency diversity array radar, after down coversion, matched filtering process are carried out successively to the Received signal strength detected, obtain pitching frequency diversity array radar m transmission channel and transmit and the echoed signal r of a kth pulse by the n-th receiving cable Received signal strength _{m, n, k}; Wherein, m ∈ 1,2 ..., M}, n ∈ { 1,2 ..., N}, M represent the total number of transmission channel, and N represents the total number of receiving cable, and M, N is positive integer, umber of pulse k ∈ 1,2 ..., K}, K represent the total number of each coherent processing interval (CPI) period transponder pulse;

Particularly, as shown in Figure 3, carry out Wave beam forming process to the n-th row Received signal strength in pitching frequency diversity array (FDA) radar, transmitting gain can be made like this to reach the level of traditional phased-array radar, and also removable wave beam receives; In other words, N number of equivalent phase center can be regarded as to lay respectively on each row mid point of N number of receiving cable.Therefore, this pitching frequency diversity array (FDA) radar arrangement can be counted as M transmission channel and N number of receiving cable.

Then, utilize pitching frequency diversity array (FDA) radar to transmit and receive signal; During this pitching frequency diversity array (FDA) radar emission signal, use same carrier frequency with a line array element, transmitting carrier frequency f ₁, f ₂..., f _m..., f _maccording to f _m=f ₀+ (m-1) △ f calculates respectively, m ∈ 1,2 ..., M}, f ₀represent with reference to carrier frequency; Setting f ₁=f ₀, variable m represents the capable transmission channel of m, and △ f represents the frequency increment of frequency diversity array radar, and △ f<<f ₀.

What the present invention supposed pitching frequency diversity array (FDA) radar emission is narrow band signal, and transmitting of its any two row array elements is mutually orthogonal, the array element choosing the upper left corner in pitching frequency diversity array (FDA) radar is reference array element; Because the land clutter of each range gate in pitching frequency diversity array (FDA) radar return signal is made up of the clutter summation of center of dispersal multiple in range gate, so transmitted by m transmission channel and the echoed signal r of a kth pulse by the n-th receiving cable Received signal strength _{m, n, k}can be expressed as:

$r_{m,n,k}=\underset{p=1}{\overset{N_a}{\&Sigma;}}\underset{q=1}{\overset{N_c}{\&Sigma;}}{\mathrm{\&xi;}}^{\{p,q\}}\exp \left\{-j2{\mathrm{\&pi;f}}_m\left({\mathrm{\&tau;}}_T^{\{p,q\}}+{\mathrm{\&tau;}}_R^{\{p,q\}}\right)\right\}\exp \{-j2{\mathrm{\&pi;f}}_d^{\left(m\right)}(k-1)T\}---\left(2\right)$

Wherein, each transponder pulse has L range gate, and each range gate is by N _cthe clutter block composition of individual statistical iteration, N _arepresent the rang ring number that each clutter block comprises, and p ∈ 1,2 ..., N _a, q ∈ 1,2 ..., N _c, N _a, N _cbe positive integer, K represents the total number of coherent processing interval (CPI) period transponder pulse, k ∈ 1,2 ..., K}, ξ ^{{ p, q}}represent radar scattering coefficient, represent the Doppler frequency of m transmission channel, and have v represents the movement velocity of pitching frequency diversity array (FDA) radar, and c represents the light velocity, and θ represents the position angle of pitching frequency diversity array (FDA) radar, represent the angle of pitch of pitching frequency diversity array (FDA) radar, f _mrepresent m transmission channel carrier frequency, m ∈ 1,2 ..., M}, M represent the total number of transmission channel and are positive integer; represent and launch time delay, represent receive time delay, and expression formula is expressed as follows respectively:

Wherein, d represents array element distance, R ₀to represent in pitching frequency diversity array (FDA) radar the distance of first array element to q clutter block.

Consider that pitching frequency diversity array (FDA) radar emission signal is only narrow band signal, can ignore subscript p, q}, after formula (3) is substituted into formula (2), obtain:

It should be noted that, formula (4) and the scattering coefficient in formula (3), be the exponential term in formula (2), and formula (3) and formula (4) comprise common exponential term j2 π (m-1).

Wherein, f _erepresent normalization pitching frequency, f _arepresent normalization orientation frequency, f _trepresent normalization Doppler frequency, and expression formula is respectively △ f _erepresent additional pitching frequency, △ f _aadditional party bit frequency, △ f _trepresent additional Doppler frequency, its expression formula is respectively with additional pitching frequency, each in additional party bit frequency and additional Doppler frequency these three is all caused by step frequency △ f; to depend in frequency diversity array radar the distance R of first array element to q clutter block ₀with the frequency increment △ f of frequency diversity array radar, therefore f _ralso frequency of distance is.

Because frequency increment is much smaller than transmitting with reference to carrier frequency, i.e. △ f < < f ₀, the △ f corresponding by formula (4) _awith △ f _titem simplifies, and can obtain:

$\frac{{\mathrm{\&Delta;f}}_a(M-1)}{f_a}=\frac{\mathrm{\&Delta;}f}{f_0}(M-1)<<1$

$\frac{{\mathrm{\&Delta;f}}_t(M-1)}{f_t}=\frac{\mathrm{\&Delta;}f}{f_0}(M-1)<<1---\left(5\right)$

Due to △ f < < f ₀, coupling terms can be left in the basket, and therefore formula (4) reduced form can be expressed as:

${\hat{r}}_{m,n,k}\&ap;\underset{p=1}{\overset{N_a}{\&Sigma;}}\underset{q=1}{\overset{N_c}{\&Sigma;}}\mathrm{\&xi;}\exp \left\{j2\mathrm{\&pi;}(f_R+f_e)(m-1)\right\}\exp \left\{j2{\mathrm{\&pi;\&Delta;f}}_e{(m-1)}^2\right\}\exp \left\{j2{\mathrm{\&pi;f}}_a(n-1)\right\}\exp \left\{j2{\mathrm{\&pi;f}}_t(k-1)\right\}---\left(6\right)$

Wherein, each transponder pulse has L range gate, and each range gate is by N _cthe clutter block composition of individual statistical iteration, N _arepresent the rang ring number that each clutter block comprises, and p ∈ 1,2 ..., N _a, q ∈ 1,2 ..., N _c, N _a, N _cbe positive integer, K represents the total number of coherent processing interim transponder pulse, k ∈ 1,2 ..., K}, ξ represent radar scattering coefficient, f _erepresent normalization pitching frequency, f _arepresent normalization orientation frequency, f _trepresent normalization Doppler frequency, △ f _erepresent additional pitching frequency, to depend in frequency diversity array radar the distance R of first array element to q clutter block ₀with the frequency increment △ f of frequency diversity array radar, therefore f _ralso frequency of distance is.

Like this, obtain pitching frequency diversity array (FDA) radar m transmission channel transmit and the echoed signal of a kth pulse by the n-th receiving cable Received signal strength through simplifying

Step 3, transmits according to pitching frequency diversity array radar m transmission channel and the echoed signal of a kth pulse by the n-th receiving cable Received signal strength obtain pitching-orientation-time three-dimensional clutter snap model c of l range gate _l, and three-dimensional clutter snap model c thus _lobtain, when there is range ambiguity in pitching frequency diversity array radar, the pitching frequency expression of l range gate and corresponding clutter compensation term h _c(R _l), according to this clutter compensation term h _c(R _l) to the pitching-orientation of each range gate-time three-dimensional clutter snap model c _lafter compensating, obtain the clutter data expression formula after compensation corresponding to m transmission channel successively clutter data expression formula after this compensation corresponding normalization pitching frequency wherein, K represents the total number of coherent processing interim transponder pulse, k ∈ 1,2 ..., K}, M represent the total number of transmission channel, m ∈ 1,2 ..., M}, N represent the total number of receiving cable, n ∈ { 1,2,, N}, each transponder pulse has L range gate, l ∈ 1,2 ..., L};

The specific implementation process of step 3 is:

Transmit according to pitching frequency diversity array radar m transmission channel and the echoed signal of a kth pulse by the n-th receiving cable Received signal strength obtain pitching-orientation-time three-dimensional clutter snap model c of l range gate _l:

$c_l=\underset{p=1}{\overset{N_a}{\&Sigma;}}\underset{q=1}{\overset{N_c}{\&Sigma;}}{\mathrm{\&xi;s}}_t\&CircleTimes;s_a\&CircleTimes;s_e---\left(7\right)$

Wherein, subscript l represents l range gate, and each range gate is by N _cthe clutter block composition of individual statistical iteration, N _arepresent the rang ring number that each clutter block comprises, each transponder pulse has L range gate, l ∈ 1,2 ..., L}, p ∈ 1,2 ..., N _a, q ∈ 1,2 ..., N _c, N _a, N _cbe positive integer, represent that Kronecker amasss, ξ represents radar scattering coefficient, s _trepresent steering vector correlation time, s _arepresent relative orientations arc steering vector, s _erepresent relevant pitching steering vector, the expression formula of these three vectors is as follows respectively:

s _t＝[1,exp{j2πf _t},…,exp{j2πf _t(K-1)}] ^T(8.a)

s _a＝[1,exp{j2πf _a},…,exp{j2πf _a(N-1)}] ^T(8.b)

s _e＝[1,exp{j2π(f _R+f _e)},…,exp{j2π(f _R+f _e)(M-1)}] ^T⊙[1,exp{j2π△f _e},…,exp{j2π△f _e(M-1) ²}] ^T(8.c)

Wherein, umber of pulse k ∈ 1,2 ..., K}, K represent the total number of coherent processing interval (CPI) period transponder pulse, m ∈ 1,2 ..., M}, M represent the total number of transmission channel, n ∈ 1,2 ..., N}, N represent the total number of receiving cable, and M, N are positive integer, f _erepresent normalization pitching frequency, f _arepresent normalization orientation frequency, f _trepresent normalization Doppler frequency, △ f _erepresent additional pitching frequency, f _rrepresent frequency of distance, ⊙ represents that Hadamard amasss.

Because frequency diversity array (FDA) radar receive channel exists carrier-frequency differences, there is slight difference in the snap data model that the snap data model in formula (7) and traditional 2D-STAP are produced, this species diversity can be used for alleviating the extra interference information of range ambiguity clutter.

Compared with traditional phased array pitching frequency spectrum, its clutter, at pitching frequency domain distribution wider range, therefore can be separated by the pitching frequency spectrum of frequency diversity array (FDA) radar from different rang rings, and pitch range is 0 ° ~ 90 °; And for traditional phased-array radar, pitching frequency f _e-PAonly depend on the angle of pitch namely

Wherein, λ ₀=c/f ₀represent reference wavelength, c represents the light velocity, f ₀represent that H represents podium level with reference to carrier frequency, due to so 0<f _e-PA<0.5; Because the usual value of normalization pitching frequency is [-0.5,0.5], so known traditional phased-array radar only occupies the positive axis of numerical frequency.

Fig. 4 is the pitching curve of frequency distribution figure of pitching frequency diversity array (FDA) radar, observation Fig. 4 is known, pitching frequency, along with the increase monotone increasing of range gate, is but the sine function about the angle of pitch, and the intensity of variation that therefore pitching frequency increases with distance is very slow; And at far region, the value of pitching frequency is very little and change is slow; Once the difference of pitching frequency diminishes, cannot be separated by the interference noise affecting range ambiguity with regard to causing in pitching frequency zones, the present invention processes under being used in frequency diversity array radar background thus, just range ambiguity clutter can be separated.

Shown in (8.c), pitching steering vector s _eform by two: Section 1 can regard that a narrow band signal adds a pitching frequency of equal value as, i.e. f _ewith f _rthe array of sum, Section 2 have employed the form of linear FM signal, and frequency modulation rate is △ f _e(m-1), so the pitching frequency f of m transmission channel _e-FDAm () can be written as:

f _e-FDA(m)＝f _R+f _e+△f _e(m-1) (10)

Wherein, f _erepresent normalized frequency, △ f _erepresent additional pitching frequency; Again because frequency increment is much smaller than reference frequency, the additional pitching frequency △ f in formula (10) Section 3 _eexpression formula can be shown as follows:

Due to additional pitching frequency △ f _eusual value is minimum, frequency increment △ f and reference carrier frequency f ₀ratio can 10 ^-3~ 10 ^-6between value, Section 3 can be ignored in formula (10), so the pitching frequency approximate expression of m transmission channel after simplifying can be:

As can be seen from formula (12), pitching frequency approximate expression be that existence additional distance relies on item, i.e. frequency of distance with the difference of traditional phased-array radar consider to there is range ambiguity situation, so the pitching frequency of p rang ring in m transmission channel, a l range gate can be expressed as:

${\tilde{f}}_{e-FDA}\left(m\right)\&ap;\frac{\mathrm{\&Delta;}f}{c}2(R_l+{\mathrm{pR}}_u)+\frac{d}{{\mathrm{\&lambda;}}_0}\frac{H}{R_0}=\frac{\mathrm{\&Delta;}f}{c}2R_l+\frac{\mathrm{\&Delta;}f}{c}2(p-1)R_u+\frac{d}{{\mathrm{\&lambda;}}_0}\frac{H}{R_0}---\left(13\right)$

Wherein, R is made ₀=R _l+ (p-1) R _u, R _lrepresent the non-fuzzy distance of l range gate, R _urepresent the fuzzy distance of l range gate, and R _u=c/2f _r, △ f represents frequency increment, λ ₀represent reference wavelength, c represents the light velocity, and H represents podium level, and d represents array element distance, f _rindicating impulse repetition frequency, N _arepresent the rang ring number of each clutter block, each transponder pulse has L range gate, l ∈ 1,2 ..., L}, p={1,2 ..., N _a; Frequency of distance f _rcan be decomposed into two: one for Range-dependent item, and another relies on rang ring number.

Fig. 5 is frequency diversity array (FDA) the radar pitching frequency distribution schematic diagram that formula (13) describes, the pitching frequency initial value scatter chart that Fig. 5 (a) is frequency diversity array (FDA) radar, the pitching frequency normalization Distribution value curve map that Fig. 5 (b) is pitching frequency diversity array (FDA) radar, is not difficult to find out that the pitching frequency of frequency diversity array (FDA) radar can with frequency of distance f _rlinear increase and significantly change.

Due to the non-fuzzy distance R of l range gate in frequency diversity array (FDA) radar echo signal _ldefinitely can obtain with frequency increment △ f, make in radar echo signal the clutter compensation term h of m transmission channel, a l range gate _c(R _l) following form can be expressed as:

$h_c\left(R_l\right)={\&lsqb;1,\exp \left\{j4\mathrm{\&pi;}\frac{\mathrm{\&Delta;}f}{c}{R}_l\right\},\mathrm{...},\left\{j4\mathrm{\&pi;}\frac{\mathrm{\&Delta;}f}{c}{R}_{l}m\right\},\mathrm{...},\exp \left\{j4\mathrm{\&pi;}\frac{\mathrm{\&Delta;}f}{c}{R}_l(M-1)\right\}\&rsqb;}^T---\left(14\right)$

Utilize this clutter compensation term h _c(R _l) to the pitching-orientation of each range gate in frequency diversity array (FDA) radar pulse-time three-dimensional snap model c _lafter compensating, the clutter data expression formula after being compensated

${\tilde{c}}_l=(I_{NK}\&CircleTimes;diag\{h_c\left(R_l\right)\left\}\right)c_l=\underset{p=1}{\overset{N_a}{\&Sigma;}}\underset{q=1}{\overset{N_c}{\&Sigma;}}{\mathrm{\&xi;s}}_t\&CircleTimes;s_a\&CircleTimes;\left(diag\right\{h_c\left(R_l\right)\left\}{s}_e\right)---\left(15\right)$

Wherein, c _lrepresent the pitching-orientation-time of each range gate three-dimensional snap model, each transponder pulse has L range gate, l ∈ 1,2 ..., L}, each range gate is by N _cthe clutter block composition of individual statistical iteration, N _arepresent the rang ring number that each clutter block comprises, p ∈ 1,2 ..., N _a, q ∈ 1,2 ..., N _c, N _a, N _cbe positive integer, s _trepresent steering vector correlation time, s _arepresent relative orientations arc steering vector, s _erepresent relevant pitching steering vector, ξ represents radar scattering coefficient, represent that Kronecker amasss, h _c(R _l) represent that the clutter compensation term of m transmission channel, a l range gate, diag{} represent and extract matrix diagonals element, I _nKrepresent that N × K ties up unit matrix.

So the clutter data expression formula after can being compensated corresponding normalization pitching frequency

${\hat{f}}_{e-FDA}\left(m\right)\&ap;\frac{\mathrm{\&Delta;}f}{c}2(p-1)R_u+\frac{d}{{\mathrm{\&lambda;}}_0}\frac{H}{R_0}=\frac{\mathrm{\&Delta;}f}{f_r}(p-1)+\frac{d}{{\mathrm{\&lambda;}}_0}\frac{H}{R_0}---\left(16\right)$

As can be seen from formula (16), the final normalization pitching frequency obtained be two sums, Section 1 is the object function of distance number of rings, and Section 2 is then the pitching frequency function of traditional phased-array radar; Wherein, R is made ₀=R _l+ (p-1) R _u, R _lrepresent the non-fuzzy distance of l range gate in radar echo signal, R _urepresent the fuzzy distance of l range gate in radar echo signal, and R _u=c/2f _r, △ f represents frequency increment, and c represents the light velocity, and H represents podium level, and d represents array element distance, f _rindicating impulse repetition frequency, each range gate is by N _cthe clutter block composition of individual statistical iteration, N _arepresent the rang ring number that each clutter block comprises, p ∈ 1,2 ..., N _a, q ∈ 1,2 ..., N _c, N _a, N _cbe positive integer, R ₀to represent in frequency diversity array (FDA) radar the distance of first array element to q clutter block, λ ₀represent reference wavelength, f _rrepresent frequency of distance.

Clutter data expression formula corresponding normalization pitching curve of frequency distribution figure after compensation as shown in Figure 6, owing to there is range ambiguity, can regard as and traditional pitching frequency f by the clutter data expression formula corresponding normalization pitching frequency distribution after compensation _e-FDAa distortion of (m); And traditional phased-array radar pitching frequency tape tolerance system, and be in the positive axis of normalized frequency, namely there is f _e-FDA(m) ∈ (0,0.5), but the pitching frequency of frequency diversity array (FDA) radar is distributed on whole normalization digital frequency space.Be not difficult to find out from Fig. 6, the spacing of the pitching frequency of different distance ring is comparatively large, and this is because the pitching frequency change of far region is less, and the 2nd ring in such as Fig. 6 is to the 4th ring, and its pitching frequency is all similar to constant on whole rang ring; Because pitching frequency can transform on the negative semiaxis of normalized frequency, i.e.-0.5<f<0, makes the range ambiguity clutter of pitching frequency field just can be separated.

Further, for preventing the frequency of pitching frequency field from cannot the situation of the fuzzy clutter of separating distance occur to occurring fuzzy, according to the distribution of pitching frequency spectrum and number periodicity frequently, the ratio of frequency increment and pulse repetition rate (PRF) can be utilized z is integral part, and υ is fraction part, usually chooses integral part z as parameter, obtains the choice criteria of frequency increment, and provide parameter z selection criterion.

In step 3, the clutter data expression formula after compensation corresponding normalization pitching frequency can be regarded as traditional pitching frequency f _e-PAa distortion, because numerical frequency has periodically, the pitching frequency in formula (16) may occur fuzzy, and can be converted into normalizing value vector, therefore the pitching frequency of different distance ring clutter may be overlapping, namely in formula (16) the result fuzzy clutter that will cause adjusting the distance be separated.

Suppose that the ratio of frequency increment △ f and pulse repetition rate (PRF) is made up of two parts, i.e. nonnegative integer portion and fractional part, expression formula can be expressed as:

$\frac{\mathrm{\&Delta;}f}{f_r}=z+\mathrm{\&upsi;}---\left(17\right)$

Wherein, z is integral part, and υ is fraction part.

So, the normalization pitching frequency simplified expression that m transmission channel is corresponding the normalization pitching frequency approximate expression that m transmission channel is corresponding can be converted into

${\stackrel{\&OverBar;}{f}}_{e-FDA}\left(m\right)=\frac{N}{f_r}(p-1)+\frac{d}{{\mathrm{\&lambda;}}_0}\frac{H}{R_0}=(z+\mathrm{\&upsi;})(p-1)+\mathrm{\&alpha;}=z(p-1)+\mathrm{\&upsi;}(p-1)+\mathrm{\&alpha;},p=1,2,...,N_a---\left(18\right)$

Wherein, make and Section 1 z (p-1) perseverance is integer, p represents distance number of rings, and d represents array element distance, and H represents podium level, R ₀represent the distance of the 1st array element to q clutter block of frequency diversity array (FDA) radar, λ ₀represent reference wavelength.

In traditional phased-array radar, first range ambiguity ring of radar echo signal middle distance door can occupy the overwhelming majority of pitching frequency field positive axis, and the pitching frequency of all the other range ambiguity rings is all close to 0, and the pitching frequency of first rang ring of this radar echo signal middle distance door known cannot convert in pitching frequency domain; Therefore, in order to the clutter in separating distance fuzzy ring, other pitching frequency beyond first range ambiguity ring pitching frequency of frequency diversity array (FDA) radar pulse signal middle distance door can be met inequality below

$0.5\&le;{\stackrel{\&OverBar;}{f}}_{e-FDA}\left(m\right)-\&lsqb;{\stackrel{\&OverBar;}{f}}_{e-FDA}\left(m\right)\&rsqb;<1---\left(19\right)$

Wherein, [] represents rounding operation, represent normalization pitching frequency.

Again because numerical frequency has periodically, namely interval (0.5,1) is equivalent to interval (-0.5,0), and α is approximately 0, and therefore expression formula (20) can be expressed as again:

0.5≤υ(p-1)-[υ(p-1)]<1,p＝2,3,…,N _a(20)

Can obtain

0.5≤υ<1,p＝2

0.5≤2υ-[2υ]<1,p＝3

0.5≤3υ-[3υ]<1,p＝4 (21)

.

.

.

0.5≤(N _a-1)υ-[(N _a-1)υ]<1,p＝N _a

Final fraction part υ can be written as:

$\frac{N_a-1.5}{N_a-1}\&le;\mathrm{\&upsi;}<1---\left(22\right)$

Convolution (17), to formula (22), can obtain

△f＝(z+υ)f _r(23)

From formula (23), given pulse repetition rate (PRF) can try to achieve step frequency; Generally integral part z can choose any nonnegative integer, but in order to ensure the independence of land clutter carrier frequency, pulse repetition rate should much smaller than reference carrier frequency.Therefore, if without particular case, the value of z should be 0.

Step 4, the normalization pitching frequency corresponding according to m transmission channel design ratio is pre--STAP wave filter, and utilize this pre--STAP wave filter to normalization pitching frequency in range ambiguity clutter be separated, then Wave beam forming is carried out to the output of pre--STAP wave filter, obtains Wave beam forming expression formula, and the removal of range ambiguity clutter is carried out to this Wave beam forming expression formula, complete the range ambiguity clutter recognition in rang ring; Wherein, pre--STAP number of filter is equal with range ambiguity number of rings order, namely in advance-STAP number of filter p ∈ 1,2 ..., N _a, N _arepresent the rang ring number that each clutter block contains, N _aalso pre--STAP number of filter is represented.

Specific implementation process is: in order to isolate normalization pitching frequency corresponding to m transmission channel in pitching frequency field in range ambiguity clutter, need in pitching to the pre--STAP wave filter of design one group, because range ambiguity number of rings is identical with wave filter number, then the pitching of this pre--STAP wave filter to coefficient is therefore according to this N _aindividual wave filter pitching, just can the clutter data expression formula after compensation to coefficient be transformed to snap when NK ties up empty, obtain the output expression formula of the pre--STAP wave filter of m transmission channel

${\hat{c}}_i\left(m\right)={(I_{NK}\&CircleTimes;g_p)}^H(I_{NK}\&CircleTimes;diag\{h_c\left(R_l\right)\left\}\right)c_l=\underset{p=1}{\overset{N_a}{\&Sigma;}}\underset{q=1}{\overset{N_c}{\&Sigma;}}{\mathrm{\&xi;}}^{\{p,q\}}\left(g_p^{H}diag\right\{h_c\left(R_i\right)\left\}{s}_e\right)(s_t\&CircleTimes;s_s)---\left(24\right)$

Wherein, I _nKrepresentation unit matrix, N _arepresent the range ambiguity number of rings that each clutter block contains, N _aalso represent pre--STAP number of filter, each range gate is by N _cthe clutter block composition of individual statistical iteration, p ∈ 1,2 ..., N _a, q ∈ 1,2 ..., N _c, N _a, N _cbe positive integer, s _trepresent steering vector correlation time, s _arepresent relative orientations arc steering vector, s _erepresent relevant pitching steering vector, () ^hrepresent conjugate transpose, represent that Kronecker amasss, ξ ^{{ p, q}}represent radar scattering coefficient, h _c(R _l) represent that the compensation term of l range gate, diag{} represent and extract matrix diagonals element.

Then to the output expression formula of the pre--STAP wave filter of this group carry out Wave beam forming, obtain Wave beam forming expression formula range ambiguity clutter now in p rang ring just can be removed, p ∈ 1,2 ..., N _a, thus reach the object carrying out being subject to the impact of range ambiguity ring when clutter compensates.Pre--STAP the process that the present invention proposes can be used for the fuzzy clutter of separating distance, and then completes clutter according to Range-dependent noise performance again and compensate; It is noted herein that the non-stationary and pitching frequency of Range-dependent clutter has nothing to do, but closely offset can be even more serious from Dependence Problem, this is also similar to the characteristic of pitching frequency.

Effect of the present invention can be further illustrated by following simulation result:

(1) simulated conditions

Emulation experiment parameter is provided by table 1.

Emulation experiment parameter list

(2) content is emulated

Emulation experiment 1: the forward sight geometry scheme choosing traditional phased-array radar here, its clutter spectrum is symmetrical in empty time zone, and Range-dependent, and Fig. 7 is expressed as clutter spectrum when detection oblique distance is respectively 6200m, 7000m, 10000m and fuzzy distance curve; Owing to there is Range-dependent, do not meet independent same distribution (IID) condition, when making frequency diversity array (FDA) radar not have range ambiguity, just can compensate clutter; For frequency diversity array (FDA) radar that there is range ambiguity clutter, the clutter of different distributions feature can superpose, and traditional clutter is compensated and lost efficacy; As seen from Figure 7, the Range-dependent problem of first rang ring is very serious, and the situation of all the other rang rings is better a little, and the clutter of first rang ring compensates the impact that will be subject to all the other rang ring clutters.

Fig. 8 (a) is for utilizing the present invention at the Space-time domain clutter spectrum schematic diagram of single range gate, and Fig. 8 (b) is for utilizing the present invention at the Space-time domain clutter spectrum schematic diagram of all range gate;

Found out by Fig. 8 (a), the clutter spectrum of single rang ring is separated obviously with all the other rang ring clutter spectrum, and the clutter of the 2nd, 3,4 rang rings is approximate overlapping; Fig. 8 (b) represents the Space-time domain clutter spectrum distribution of all range gate, and range ambiguity clutter almost account for the whole of whole normalization Doppler frequency-horizontal spatial frequency territory right half part, target detection performance sharp-decay; When platform rapid movement, the range ambiguity of clutter and doppler ambiguity can conflict, mutually so must consider emphatically the range ambiguity problem of clutter under high impulse repetition radar system.

Emulation experiment 2: Fig. 9 is the clutter spectrum schematic diagram of traditional phased-array radar in pitching-distance domain, and Figure 10 (a) is pitching frequency diversity array (FDA) radar of the present invention pitching after pitching frequency compensation-distance domain clutter spectrum schematic diagram; Figure 10 (b) is pitching frequency diversity array (FDA) radar of the present invention pitching after normalization pitching frequency compensation-distance domain clutter spectrum schematic diagram.

For traditional phased-array radar, the positive half that the pitching frequency domain of clutter only accounts for numerical frequency principal value interval is divided, and in the first fuzzy distance region, the angle of pitch with oblique distance change rapidly, therefore, the pitching frequency change in the first fuzzy distance region is very fast, second and third, the pitching frequency change in four fuzzy distance regions is slow; In addition, second and third, the angle of pitch in four fuzzy distance regions all close to 0 °, pitching frequency is also all close to 0; Because the pitching frequency of range ambiguity region (particularly second and third, four fuzzy distance regions) is too close each other, therefore, traditional phased-array radar is made to be difficult to carry out the fuzzy clutter of separating distance by Wave beam forming in the vertical direction; The carrier aircraft height chosen is 6000m, so when detecting oblique distance and being less than 6000m, the first fuzzy distance region does not have clutter.

And in frequency diversity array (FDA) radar, the difference of pitching clutter spectrum distribution is very large, this is caused by frequency diversity, e.g., from pitching frequency approximate expression in can find out, the pitching frequency change of all detection oblique distances is obvious, and pitching frequency is relevant to oblique distance, as can be seen from Figure 10 (a), the pitching frequency of the 2nd, 3,4 rang rings is similar to linear increase with the increase of detection oblique distance, in the present invention, range ambiguity clutter can be separated according to the range unit of setting, but this also needs a large amount of pitching wave filters, once parameter change, wave filter just needs to redesign, Figure 10 (b) shows, after pitch compensation the 2nd, 3, the pitching frequency spectrum of 4 rang rings is less with the change of detection oblique distance, and unique difference of the clutter distribution of Fig. 9 and Figure 10 (b), be the frequency change caused by range ambiguity number of rings, therefore use wave filter just clutter can be separated in pitching district, for example, fuzzy for correlation distance clutter just can be separated by 4 bandpass filter.

The range ambiguity clutter spectrum schematic diagram that Figure 11 (a) is separated for pitching frequency diversity array (FDA) radar of the present invention 1st rang ring; The range ambiguity clutter spectrum schematic diagram that the 2nd rang ring that Figure 11 (b) is pitching frequency diversity array (FDA) thunder of the present invention is separated; The range ambiguity clutter spectrum schematic diagram that Figure 11 (c) is separated for pitching frequency diversity array (FDA) radar of the present invention 3rd rang ring; The range ambiguity clutter spectrum schematic diagram that Figure 11 (d) is separated for pitching frequency diversity array (FDA) radar of the present invention 4th rang ring;

As can be seen from 11 (a) ~ Figure 11 (d), the clutter of each rang ring is successfully separated, and the clutter of the 1st rang ring has serious distance dependencies, and does not meet independent same distribution (IID) condition; And the 2nd, 3,4 rang rings are then approximate respectively meets independent same distribution (IID) condition, so can directly carry out space-time adaptive process (STAP).

Figure 12 is the clutter spectrum schematic diagram after first rang ring including range ambiguity clutter utilizes the present invention to carry out clutter compensation, in fig. 12, carry out clutter compensation to including the 1st rang ring after range ambiguity clutter, after clutter compensates, Space-time domain clutter just can be separated.Therefore, target detection can be done to the rang ring isolating range ambiguity clutter each time, and estimate the non-fuzzy parameter of its this target.

In sum, Simulation experiments validate correctness of the present invention, validity and reliability.

Obviously, those skilled in the art can carry out various change and modification to the present invention and not depart from the spirit and scope of the present invention; Like this, if these amendments of the present invention and modification belong within the scope of the claims in the present invention and equivalent technologies thereof, then the present invention is also intended to comprise these change and modification.

Claims (5)

1., based on a range ambiguity clutter suppression method of pitching frequency diversity STAP, it is characterized in that, comprise the following steps:

Step 1, sets up Air-borne Forward-looking battle array radar system, and this Air-borne Forward-looking battle array radar system is pitching frequency diversity array radar, and this pitching frequency diversity array radar is the array structure of the capable N row of M, namely has M transmission channel, N number of receiving cable;

Step 2, suppose that every a line array element of pitching frequency diversity array radar launches orthogonal signal, the equivalent phase center of its orthogonal signal is the mid point of corresponding row; In all receiving cables of pitching frequency diversity array radar, after down coversion, matched filtering process are carried out successively to the Received signal strength detected, obtain pitching frequency diversity array radar m transmission channel and transmit and the echoed signal r of a kth pulse by the n-th receiving cable Received signal strength _{m, n, k}; Wherein, m ∈ 1,2 ..., M}, n ∈ 1,2 ..., N}, M represent the total number of transmission channel, and N represents the total number of receiving cable, and M, N are positive integer, umber of pulse k ∈ 1,2 ..., K}, K represent the total number of each coherent processing interim transponder pulse;

Step 3, transmits according to pitching frequency diversity array radar m transmission channel and the echoed signal of a kth pulse by the n-th receiving cable Received signal strength obtain pitching-orientation-time three-dimensional clutter snap model c of l range gate _l, and three-dimensional clutter snap model c thus _lobtain, when there is range ambiguity in pitching frequency diversity array radar, the pitching frequency expression of l range gate and corresponding clutter compensation term h _c(R _l), according to this clutter compensation term h _c(R _l) to the pitching-orientation of each range gate-time three-dimensional clutter snap model c _lafter compensating, obtain the clutter data expression formula after compensation corresponding to m transmission channel successively clutter data expression formula after this compensation corresponding normalization pitching frequency wherein, K represents the total number of coherent processing interim transponder pulse, k ∈ 1,2 ..., K}, M represent the total number of transmission channel, m ∈ 1,2 ..., M}, N represent the total number of receiving cable, n ∈ { 1,2,, N}, each transponder pulse has L range gate, l ∈ 1,2 ..., L};

Step 4, the normalization pitching frequency corresponding according to m transmission channel design ratio is pre--STAP wave filter, and utilize this pre--STAP wave filter to normalization pitching frequency in range ambiguity clutter be separated, then Wave beam forming is carried out to the output of pre--STAP wave filter, obtains Wave beam forming expression formula, and the removal of range ambiguity clutter is carried out to this Wave beam forming expression formula, complete the range ambiguity clutter recognition in rang ring; Wherein, pre--STAP number of filter is equal with range ambiguity number of rings order, namely in advance-STAP number of filter p ∈ 1,2 ..., N _a, N _arepresent the rang ring number that each clutter block contains, N _aalso pre--STAP number of filter is represented.

2. the range ambiguity clutter suppression method based on pitching frequency diversity STAP according to claim 1, it is characterized in that, in described step 2, pitching frequency diversity array radar m transmission channel transmits and the echoed signal r of a kth pulse by the n-th receiving cable Received signal strength _{m, n, k}adopt its reduced form

${\hat{r}}_{m,n,k}\&ap;\underset{p=1}{\overset{N_a}{\mathrm{\&Sigma;}}}\underset{q=1}{\overset{N_c}{\mathrm{\&Sigma;}}}\mathrm{\&xi;}\exp \left\{j2\mathrm{\&pi;}(f_R+f_e)(m-1)\right\}\exp \left\{j2{\mathrm{\&pi;\&Delta;f}}_e{(m-1)}^2\right\}\exp \left\{j2{\mathrm{\&pi;\&Delta;f}}_a(n-1)\right\}\exp \left\{j2{\mathrm{\&pi;\&Delta;f}}_t(k-1)\right\}$

Wherein, each transponder pulse has L range gate, and each range gate is by N _cthe clutter block composition of individual statistical iteration, N _arepresent the rang ring number that each clutter block comprises, and p ∈ 1,2 ..., N _a, q ∈ 1,2 ..., N _c, N _a, N _cbe positive integer, K represents the total number of coherent processing interim transponder pulse, k ∈ 1,2 ..., K}, ξ represent radar scattering coefficient, f _erepresent normalization pitching frequency, f _arepresent normalization orientation frequency, f _trepresent normalization Doppler frequency, △ f _erepresent additional pitching frequency, to depend in frequency diversity array radar the distance R of first array element to q clutter block ₀with the frequency increment △ f of frequency diversity array radar, c represents the light velocity, f _rfor frequency of distance.

3. the range ambiguity clutter suppression method based on pitching frequency diversity STAP according to claim 1, is characterized in that, in described step 3, and the normalization pitching frequency simplified expression that m transmission channel is corresponding for

${\hat{f}}_{e-FDA}\left(m\right)\&ap;\frac{\mathrm{\&Delta;}f}{c}2(p-1)R_u+\frac{d}{L_0}\frac{H}{R_0}=\frac{\mathrm{\&Delta;}f}{f_r}(p-1)+\frac{d}{{\mathrm{\&lambda;}}_0}\frac{H}{R_0}$

Wherein, R is made ₀=R _l+ (p-1) R _u, R _lrepresent the non-fuzzy distance of l range gate, R _urepresent the fuzzy distance of l range gate, and R _u=c/2f _r, △ f represents frequency increment, λ ₀represent reference wavelength, c represents the light velocity, and H represents podium level, and d represents array element distance, f _rindicating impulse repetition frequency, N _arepresent the rang ring number of each clutter block, each transponder pulse has L range gate, l ∈ 1,2 ..., L}, p={1,2 ..., N _a.

4. the range ambiguity clutter suppression method based on pitching frequency diversity STAP according to claim 3, is characterized in that, described frequency increment △ f and pulse repetition rate f _rin pass be: z is integer portion, and v is fractional part, and the value of z is 0.

5. the range ambiguity clutter suppression method based on pitching frequency diversity STAP according to claim 1, is characterized in that, in described step 4, and the output expression formula of the pre--STAP wave filter of m transmission channel

${\hat{c}}_l\left(m\right)\&ap;{(I_{NK}\&CircleTimes;g_p)}^H(I_{NK}\&CircleTimes;diag\{h_c\left(R_l\right)\left\}\right)c_l\underset{p=1}{\overset{N_a}{\mathrm{\&Sigma;}}}\underset{q=1}{\overset{N_c}{\mathrm{\&Sigma;}}}{\mathrm{\&xi;}}^{\{p,q\}}\left(g_p^{H}diag\right\{h_c\left(R_l\right)\left\}{s}_e\right)(s_t\&CircleTimes;s_s)$

Wherein, I _nKrepresentation unit matrix, N _arepresent the range ambiguity number of rings that each clutter block contains, N _aalso represent pre--STAP number of filter, each range gate is by N _cthe clutter block composition of individual statistical iteration, p ∈ 1,2 ..., N _a, q ∈ 1,2 ..., N _c, N _a, N _cbe positive integer, s _trepresent steering vector correlation time, s _arepresent relative orientations arc steering vector, s _erepresent relevant pitching steering vector, () ^hrepresent conjugate transpose, represent that Kronecker amasss, ξ ^{{ p, q}}represent radar scattering coefficient, h _c(R _l) represent that the compensation term of l range gate, diag{} represent and extract matrix diagonals element.