CN104777467A - Target detection method based on frequency scan antenna - Google Patents

Abstract

The invention discloses a target detection method base on a frequency scan antenna. According to the target detection method, rapid target detection and angular super-resolution are realized through processing of raw echo data. The target detection method comprises specific steps as follows: an echo signal model is established; a raw echo signal is subjected to subspace average processing to obtain a signal matrix; an autocorrelation matrix of the obtained signal matrix is gained; the signal autocorrelation matrix is subjected to eigenvalue decomposition to obtain an eigenvalue and eigenvector space, and the eigenvector space is divided into signal subspace and noise subspace; the signal subspace and the noise subspace are orthogonalized, and an FS-MUSIC pseudo-spectrum is built; the pseudo-spectrum is subjected to spectral peak searching, and an angle corresponding to multiple maximum value points is found out and taken as the target echo direction. According to the method, the signals are not required to be received by the aid of arrays, all that is needed is to emit the signals by the frequency scan antenna and receive the signals by horns or waveguide ports, the processing is simple and fast, and the method is applicable to fast detection of multiple targets.

Description

Based on the object detection method of frequency scan antenna

Technical field

The present invention relates to Radar Signal Detection technical field, relate more specifically to a kind of object detection method based on frequency scan antenna.

Background technology

Target detection is the Important Problems of the association area such as radar, communication research always, and in such as cellphone subscriber's local positioning, WiFi network, many application scenarioss such as location Based service, radar target location, have widespread demand.Wherein Mutual coupling (DOA) is as an importance of target detection, receives much concern in recent years always.Major part Mutual coupling system all utilizes array antenna as receiver, the array signal MUSIC algorithm received carries out process and obtains, but this system wants raising resolution to need to increase element number of array, thus cause cost increase, power consumption increase, circuit structure complexity.

Frequency scan antenna is the class antenna of beam position with frequency change, wherein the main application scenarios of the frequency scan antenna of millimeter wave and Terahertz section has: for the Area Surveillance RADAR on battlefield, airport etc., to 2 dimensional region scanning imagery, one of them dimension utilizes the beam scanning of frequency control, and another dimension utilizes antenna to rotate; For the terrain detection radar of spacecraft safe landing, utilize the detection of frequency scan antenna realization to obstacles such as touchdown area rock, slopes; For Terahertz two-dimensional imaging, wherein orientation is to utilizing the frequency sweeping detection of a target.But these radars have a defect, are limited by beam angle in the resolution in frequency sweeping direction.The method improving frequency sweeping directional resolution normally increases antenna aperture to reduce antenna beamwidth, but this mode can bring the lifting of difficulty of processing, and the increase of design complexities, and many times due to the restriction of radar system entirety, the size of antenna can not be allowed very large.Therefore, improve frequency sweeping direction target resolution characteristic from algorithm, become problem demanding prompt solution.At present, there is not yet MUSIC algorithm application to based on frequency scan antenna systematic account.

Summary of the invention

In view of this, fundamental purpose of the present invention is to propose a kind of object detection method based on frequency scan antenna, to be detected fast and angle super-resolution by process raw radar data realize target.Method of the present invention does not need by array received, only needs frequency scan antenna to transmit, loudspeaker or waveguide port Received signal strength, is suitable for the quick detection of multiple target.The inventive method can be applied to terahertz imaging, Area Surveillance RADAR, Non-Destructive Testing, target and identify fast and the field such as tracking.

To achieve these goals, as one aspect of the present invention, the invention provides a kind of object detection method based on frequency scan antenna, comprise the following steps:

Step S1: set up echo signal model;

Step S2: carry out subspace average treatment to original echoed signals, obtains signal matrix;

Step S3: autocorrelation matrix is asked for the signal matrix obtained in step S2;

Step S4: Eigenvalues Decomposition is carried out to the signal autocorrelation matrix obtained in step S3, obtains eigenwert and characteristic vector space, and described characteristic vector space is divided into signal subspace and noise subspace;

Step S5: by the described signal subspace that obtains in step S4 and noise subspace orthogonal, and construct FS-MUSIC puppet spectrum;

Step S6: carry out spectrum peak search to step S5 gained puppet spectrum, finding out angle corresponding to multiple maximum point is exactly target echo direction.

Wherein, step S1 comprises:

Echoed signal is expressed as X=AS+U, wherein X=[x (f ₁), x (f ₂), x (f ₃) ..., x (f _n)] ^t, be that N*1 ties up echoed signal vector, each element in this vector is the signal of the different frequency received, x (f _n) referred to as x _n, n=1,2 ..., N;

A=[α (f, β ₁) α (f, β ₂) ... α (f, β _m)], be that N*M ties up array guiding matrix, each of wherein A is classified as an array steering vector;

α (f, β _m)=[a (f ₁, β _m) a (f ₂, β _m) ... a (f _n, β _m)] ^t, m=1,2..., M, wherein a (f _n, β _m) be frequency f _nlower β _mthe dual station directivity factor in direction;

S=[s (β ₁) s (β ₂) ... s (β _m)] ^t, be β _mthe backscattering coefficient of direction target, s (β _m) referred to as s _m, m=1,2 ..., M;

U=[u (f ₁) u (f ₂) ... u (f _n)] ^tfor the noise of different frequency, x (f _n) referred to as x _n, n=1,2 ..., N.

Wherein, the described dual station directivity factor a (f in step S1 _n, β _m) comprise amplitude or phase information.

Wherein, step S2 comprises:

Subspace average treatment is carried out to original echoed signals X: X=[x ^{{ 1}}x ^{{ 2}}... x ^{{ P}}],

Wherein:

x ^{1}＝[x ₁，x ₂，...，x _Q] ^T

x ^{2}＝[x ₂，x ₃，...，x _Q+1] ^T，

......

X ^{{ P}}=[x _p, x _p+1..., x _n] ^t, P is subspace number, P > D (setting D as target number), and Q is every sub spaces element number, and P+Q+1=M.

Wherein, step S3 comprises:

According to following formula, autocorrelation matrix is asked for the signal matrix obtained in step S2:

$R_{\mathrm{xx}}=\frac{1}{P}\underset{p=1}{\overset{P}{\mathrm{\Σ}}}{x}^{\left\{p\right\}}{x}^{\left\{p\right\}H};$

Wherein, P is subspace number, and H represents conjugate transpose.

Wherein, step S4 comprises:

Eigenvalues Decomposition is carried out to the described signal autocorrelation matrix obtained in step S3, obtains eigenwert and characteristic vector space wherein and λ ₁>=λ ₂>=...>=λ _q, eigenwert characteristic of correspondence vector space wherein for eigenvalue λ ₁(i=1,2 ..., Q) characteristic of correspondence vector;

Known target number is D, so only have a maximum D eigenwert relevant with signal, is denoted as signal characteristic value the same eigenwert relevant to noise is λ _n={ λ _d+1, λ _d+2..., λ _q;

Characteristic vector space is divided into signal subspace and noise subspace, wherein signal subspace ${\hat{E}}_S=\{{\hat{e}}_1,{\hat{e}}_2,...,{\hat{e}}_D\},$ Dimension is Q*D; Noise subspace ${\hat{E}}_N=\{{\hat{e}}_{D+1},{\hat{e}}_{D+2},...,{\hat{e}}_Q\},$ Dimension is Q* (Q-D).

Wherein, step S5 comprises:

Array steering vector in step S1 is denoted as more general form: α (f, β);

By the described signal subspace that obtains in step S4 and noise subspace orthogonal, it can thus be appreciated that array steering vector and noise subspace are also orthogonal, namely wherein ε is a very little number; And

Structure FS-MUSIC puppet spectrum:

$P_{\mathrm{FS}-\mathrm{MU}}\left(\mathrm{\β}\right)=\frac{\mathrm{\α}{(f,\mathrm{\β})}^H\mathrm{\α}(f,\mathrm{\β})}{\mathrm{\α}{(f,\mathrm{\β})}^H{\hat{E}}_N{\hat{E}}_N^H\mathrm{\α}(f,\mathrm{\β})};$

Wherein, β={ β ₁, β ₂..., β _m.

Wherein, the formula constructing FS-MUSIC puppet spectrum described in step S5 is the puppet spectrum formula with weighted type.

Wherein, also comprise after step S6:

Step S7: by transmission frequency and the scanning angle relation of frequency scanning antenna, the described multiple target echo directions obtained by step S6 are converted into multiple frequency; And

Step S8: the described multiple frequency obtained by step S7 and the signal extraction of neighbouring frequency band out, are carried out pulse compression, obtained the two dimensional image of target.

Wherein, described object detection method is applied to terahertz imaging, Area Surveillance RADAR, Non-Destructive Testing, target and identifies fast and tracking field.

Known based on technique scheme, method of the present invention has following beneficial effect: (1) this method utilizes the beam scanning characteristic of frequency scan antenna, realize target distance to orientation to two dimension differentiate; Relative to other target detection mode, there is the advantage that system is simple, cost is low, detection speed is fast; (2) the FS-MUSIC angle super-resolution algorithm utilizing the present invention to propose, can realize being less than the angle-resolved of 3dB beam angle; (3) utilize object detection method of the present invention, frequency-region signal corresponding for two crest angles in Fig. 3 extracted, carries out the two-dimensional position information that process of pulse-compression obtains target, as shown in Figure 4, two targets distance to orientation to all distinguishable.

Accompanying drawing explanation

Fig. 1 is the principle schematic of the object detection method based on frequency scan antenna of the present invention;

Fig. 2 is the process flow diagram of FS-MUSIC angle super-resolution algorithm of the present invention;

Fig. 3 is the result of FS-MUSIC algorithm of the present invention, beam angle-scanning angle figure;

Fig. 4 is the result of object detection method of the present invention, the two-dimensional position information schematic diagram of target.

Embodiment

For making the object, technical solutions and advantages of the present invention clearly understand, below in conjunction with specific embodiment, and with reference to accompanying drawing, the present invention is described in further detail.

The invention discloses a kind of FS-MUSIC angle super-resolution algorithm based on frequency scan antenna, the angle super-resolution that beam scanning direction is less than 3dB beam angle can be realized; Again on the one hand, the invention discloses a kind of object detection method based on frequency scan antenna, as shown in Figure 1, wave beam is at a scanning direction, can obtain target range to orientation to information, wherein orientation utilizes beam scanning function and the FS-MUSIC algorithm realization of frequency scan antenna to resolution, and distance adopts pulse compression technique to realize to resolution.

FS-MUSIC algorithm steps of the present invention is as follows:

Step S1: set up echo signal model.Echoed signal can be expressed as X=AS+U;

Wherein X=[x (f ₁), x (f ₂), x (f ₃) ..., x (f _n)] ^t, be that N*1 ties up echoed signal vector, each element in this vector is the signal of the different frequency received, x (f _n) referred to as x _n, n=1,2 ..., N;

A＝[α(f，β ₁)α(f，β ₂)...α(f，β _M)] (1)

A is that N*M ties up array guiding matrix, and each of wherein A is classified as an array steering vector;

α (f, β _m)=[a (f ₁, β _m) a (f ₂, β _m) ... a (f _n, β _m)] ^t, m=1,2..., M, wherein a (f _n, β _m) be frequency f _nlower β _mthe dual station directivity factor in direction;

S=[s (β ₁) s (β ₂) ... s (β _m)] ^t, be β _mthe backscattering coefficient of direction target, s (β _m) referred to as s _m, m=1,2 ..., M;

U=[u (f ₁) u (f ₂) ... u (f _n)] ^tfor the noise of different frequency, x (f _n) referred to as x _n, n=1,2 ..., N.

Step S2: subspace average treatment is carried out to original echoed signals X: x=[x ^{{ 1}}x ^{{ 2}}... x ^{{ p}}],

Wherein:

x ^{1}＝[x ₁，x ₂，...，x _Q] ^T，

x ^{2}＝[x ₂，x ₃，...，x _Q+1] ^T，

......

X ^{{ P}}=[x _p, x _p+1..., x _n] ^t, make P be subspace number.

Step S3: autocorrelation matrix is asked for the signal matrix obtained in step S2:

$R_{\mathrm{xx}}=\frac{1}{P}\underset{p=1}{\overset{P}{\mathrm{\Σ}}}{x}^{\left\{p\right\}}{x}^{\left\{p\right\}H}---\left(2\right)$

Wherein H represents conjugate transpose.

Step S4: Eigenvalues Decomposition is carried out to the signal autocorrelation matrix obtained in step S3, obtains eigenwert and characteristic vector space wherein and λ ₁>=λ ₂>=...>=λ _q, the descending characteristic of correspondence vector of eigenwert is suppose that known target number is D, so only have a maximum D eigenwert relevant with signal, be denoted as signal characteristic value ${\widehat{\mathrm{\λ}}}_S=\{{\mathrm{\λ}}_1,{\mathrm{\λ}}_2,...,{\mathrm{\λ}}_D\};$ The same eigenwert relevant to noise is ${\widehat{\mathrm{\λ}}}_N=\{{\mathrm{\λ}}_{D+1},{\mathrm{\λ}}_{D+2},...,{\mathrm{\λ}}_Q\}.$ Characteristic vector space is divided into signal subspace and noise subspace, wherein signal subspace is ${\hat{E}}_S=\{{\hat{e}}_1,{\hat{e}}_2,...,{\hat{e}}_D\},$ Dimension is Q*D; Noise subspace is ${\hat{E}}_N=\{{\hat{e}}_{D+1},{\hat{e}}_{D+2},...,{\hat{e}}_Q\},$ Dimension is Q* (Q-D).

Step S5: array steering vector in step S1 is denoted as more general form: α (f, β).The signal subspace obtained in step S4 and noise subspace orthogonal, it can thus be appreciated that array steering vector and noise subspace are also orthogonal, namely wherein ε is a very little number.

Structure FS-MUSIC puppet spectrum:

$P_{\mathrm{FS}-\mathrm{MU}}\left(\mathrm{\β}\right)=\frac{\mathrm{\α}{(f,\mathrm{\β})}^H\mathrm{\α}(f,\mathrm{\β})}{\mathrm{\α}{(f,\mathrm{\β})}^H{\hat{E}}_N{\hat{E}}_N^H\mathrm{\α}(f,\mathrm{\β})}---\left(3\right);$

Wherein β={ β ₁, β ₂..., β _m.

Step S6: to step S5 gained puppet spectrum, carry out spectrum peak search, the angle finding out D maximum point corresponding is exactly target echo direction.

In above-mentioned algorithm, the dual station directivity factor a (f in step S1 _n, β _m) can be amplitude form, also can comprise phase information.

In step S5, pseudo-spectrum form is not limited to formula provided by the present invention, the puppet of weighted type can also be had to compose the multi-form puppets such as formula and compose formula.

The invention also discloses a kind of object detection method based on frequency scan antenna, step is as follows:

Step G1: by transmission frequency and the scanning angle relation of frequency scanning antenna, the D obtained by step S6 target echo direction, is converted into D frequency.

Step G2: D the frequency obtained by step G1 and the signal extraction of neighbouring frequency band out, are carried out pulse compression, obtained the two dimensional image of target.

Detect test through actual, method of the present invention has following advantage:

(1) this method utilizes the beam scanning characteristic of frequency scan antenna, realize target distance to orientation to two dimension differentiate; Relative to other target detection mode, there is the advantage that system is simple, cost is low, detection speed is fast.

(2) the FS-MUSIC angle super-resolution algorithm utilizing the present invention to propose, can realize being less than the angle-resolved of 3dB beam angle.Below by experiment, this algorithm is verified.Terahertz frequency sweeping target detection experiment parameter arranges as shown in table 1 below:

Table 1

Parameter type	Numerical value	Unit
			Bandwidth range	230～330	GHz
Beam-scanning angles	-36～-10	Degree
			3dB beam angle	2.2～2.5	Degree
Target range	1.57	m
			Target interval	1.6	Degree

Two angle on target intervals are less than 3dB beam angle, and directly receiving data cannot differentiate.Fig. 3 carries out with FS-MUSIC algorithm the result that processes, and can find that two targets are resolved out very clearly, angle intervals 1.78 °, error is allowing within the scope accepted.

(3) utilize object detection method of the present invention, frequency-region signal corresponding for two crest angles in Fig. 3 extracted, carries out the two-dimensional position information that process of pulse-compression obtains target, as shown in Figure 4, two targets distance to orientation to all distinguishable.

Above-described specific embodiment; object of the present invention, technical scheme and beneficial effect are further described; be understood that; the foregoing is only specific embodiments of the invention; be not limited to the present invention; within the spirit and principles in the present invention all, any amendment made, equivalent replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (10)

1., based on an object detection method for frequency scan antenna, comprise the following steps:

Step S1: set up echo signal model;

Step S2: carry out subspace average treatment to original echoed signals, obtains signal matrix:

Step S3: autocorrelation matrix is asked for the signal matrix obtained in step S2:

Step S4: Eigenvalues Decomposition is carried out to the signal autocorrelation matrix obtained in step S3, obtains eigenwert and characteristic vector space, and described characteristic vector space is divided into signal subspace and noise subspace;

Step S5: by the described signal subspace that obtains in step S4 and noise subspace orthogonal, and construct FS-MUSIC puppet spectrum:

Step S6: carry out spectrum peak search to step S5 gained puppet spectrum, finding out angle corresponding to multiple maximum point is exactly target echo direction.

2. the object detection method based on frequency scan antenna according to claim 1, wherein step S1 comprises:

Echoed signal is expressed as X=AS+U, wherein X=[x (f ₁), x (f ₂), x (f ₃) ..., x (f _n)] ^t, be that N*1 ties up echoed signal vector, each element in this vector is the signal of the different frequency received, x (f _n) referred to as x _n, n=1,2 ..., N;

A=[α (f, β ₁) α (f, β ₂) ... α (f, β _m)], be that N*M ties up array guiding matrix, each of wherein A is classified as an array steering vector;

α (f, β _m)=[a (f ₁, β _m) a (f ₂, β _m) ... a (f _n, β _m)] ^t, m=1,2 ..., M, wherein a (f _n, β _m) be frequency f _nlower β _mthe dual station directivity factor in direction;

S=[s (β ₁) s (β ₂) ... s (β _m)] ^t, be β _mthe backscattering coefficient of direction target, s (β _m) referred to as s _m, m=1,2 ..., M;

U=[u (f ₁) u (f ₂) ... u (f _n)] ^tfor the noise of different frequency, x (f _n) referred to as x _n, n=1,2 ..., N.

3. the object detection method based on frequency scan antenna according to claim 2, the described dual station directivity factor a (f wherein in step S1 _n, β _m) comprise amplitude or phase information.

4. the object detection method based on frequency scan antenna according to claim 2, wherein step S2 comprises:

Subspace average treatment is carried out to original echoed signals X: X=[x ^{{ 1}}x ^{{ 2}}x ^{{ P}}],

Wherein:

x ^{1}＝[x ₁，x ₂，…，x _Q] ^T，

x ^{2}＝[x ₂，x ₃，…，x _Q+1] ^T，

……

X ^{{ P}}=[x _p, x _p+1..., x _n] ^t, P is subspace number, P > D (setting D as target number), and Q is every sub spaces element number, and P+Q+1=M.

5. the object detection method based on frequency scan antenna according to claim 4, wherein step S3 comprises:

According to following formula, autocorrelation matrix is asked for the signal matrix obtained in step S2:

$R_{\mathrm{xx}}=\frac{1}{P}\underset{p=1}{\overset{P}{\mathrm{\Σ}}}{x}^{\left\{p\right\}}{x}^{\left\{p\right\}H};$

Wherein, P is subspace number, and H represents conjugate transpose.

6. the object detection method based on frequency scan antenna according to claim 5, wherein step S4 comprises:

Eigenvalues Decomposition is carried out to the described signal autocorrelation matrix obtained in step S3, obtains eigenwert and characteristic vector space wherein and λ ₁>=λ ₂>=...>=λ _q, eigenwert characteristic of correspondence vector space wherein for eigenvalue λ _i(i=1,2 ..., Q) and characteristic of correspondence vector;

Known target number is D, so only have a maximum D eigenwert relevant with signal, is denoted as signal characteristic value the same eigenwert relevant to noise is ${\widehat{\mathrm{\λ}}}_N=\{{\mathrm{\λ}}_{D+1},{\mathrm{\λ}}_{D+2},...,{\mathrm{\λ}}_Q\};$

Characteristic vector space is divided into signal subspace and noise subspace, wherein signal subspace ${\hat{E}}_S=\{{\hat{e}}_1,{\hat{e}}_2,...,{\hat{e}}_D\},$ Dimension is Q*D; Noise subspace ${\hat{E}}_N=\{{\hat{e}}_{D+1},{\hat{e}}_{D+2},...,{\hat{e}}_Q\},$ Dimension is Q* (Q-D).

7. the object detection method based on frequency scan antenna according to claim 6, wherein step S5 comprises:

Array steering vector in step S1 is denoted as more general form: α (f, β);

By the described signal subspace that obtains in step S4 and noise subspace orthogonal, it can thus be appreciated that array steering vector and noise subspace are also orthogonal, namely wherein ε is a very little number; And

Structure FS-MUSIC puppet spectrum:

$P_{\mathrm{FS}-\mathrm{MU}}\left(\mathrm{\β}\right)=\frac{\mathrm{\α}{(f,\mathrm{\β})}^H\mathrm{\α}(f,\mathrm{\β})}{\mathrm{\α}{(f,\mathrm{\β})}^H{\hat{E}}_N\widehat{E_N^H}\mathrm{\α}(f,\mathrm{\β})};$

Wherein, β={ β ₁, β ₂..., β _m.

8. the object detection method based on frequency scan antenna according to claim 7, the formula wherein constructing FS-MUSIC puppet spectrum described in step S5 is the puppet spectrum formula with weighted type.

9. the object detection method based on frequency scan antenna according to claim 7, wherein also comprises after step S6:

Step S7: by transmission frequency and the scanning angle relation of frequency scanning antenna, the described multiple target echo directions obtained by step S6 are converted into multiple frequency; And

Step S8: the described multiple frequency obtained by step S7 and the signal extraction of neighbouring frequency band out, are carried out pulse compression, obtained the two dimensional image of target.

10. the object detection method based on frequency scan antenna according to claim 1, wherein said object detection method is applied to terahertz imaging, Area Surveillance RADAR, Non-Destructive Testing, target and identifies fast and tracking field.