CN103454629A - Sector-scan imaging method based on ultra wide band MIMO array - Google Patents

Abstract

The invention provides a sector-scan imaging method based on an ultra wide band MIMO array. M independent pulse signals are simultaneously transmitted in a single pulse through M transmitting array elements of the MIMO array, and the total bandwidth of M independent pulses is equal to the bandwidth of a single UWB pulse. An echo is received through a linear array, and echo moments corresponding to the different pulses are separated through matched filtering. The echo moments are processed, the UWB signal synthesis is conducted on the echo moments, and a final sector-scan image is obtained. The sector-scan imaging method based on the ultra wide band MIMO array has the high-direction and high-range resolution which is similar to the resolution obtained when a single large-bandwidth UWB signal is used, and the defects that the time consumed when the signal is transmitted through a step frequency imaging system is too long is overcome.

Description

A kind of fan sweeping formation method based on ultra broadband MIMO array

Technical field

The present invention relates to a kind of array image-forming method.

Background technology

The UWB signal that ultra broadband (Ultra-Wideband:UWB) imaging system has a large bandwidth by use obtain rise from and high azimuth resolution (Taylor J, Ultra-wideband radar technology, Boca Raton:CRC Press, 2001).Super-broadband tech is applied to array fan sweeping imaging field, can under the prerequisite that does not increase element number of array and array aperture, improves imaging resolution.Yet in actual use, the transmitting terminal of a lot of fan sweeping imaging systems can't directly be launched the UWB signal of large bandwidth.In addition, the limited bandwidth of fan sweeping imaging system receiving end processor, also be difficult to directly process the UWB signal of large bandwidth.For these shortcomings, Gill(Gill G, Detection of targets embedded in clutter using frequency step waveform, Proceedings of the1994International Symposium on Noise and Clutter Rejection in Radars and Imaging Sensors, Kawasaki, Japan, 1994:115) and Liu Xiaohong (Liu Xiaohong, the Digital Signal Analysis and Processing of high Range resolution imaging radar, Xian Electronics Science and Technology University's master thesis, 2006) etc. the people has carried out a series of research to step frequency (Stepped Frequency) system, point out that the step frequency system can utilize a plurality of pulses to synthesize the UWB signal of large bandwidth.But the emission of these pulses is not synchronously to carry out, but launches according to sequencing.For aliasing does not occur the echo between each pulse, the interval long enough between step frequency system requirements adjacent pulse.When target is kept in motion, in pulse, irradiate successively in the process of target, target has produced range migration, and this makes the step frequency system directly to moving target, to carry out imaging, and thing followed target travel compensation has also increased the complexity of algorithm greatly.

Summary of the invention

In order to overcome the long deficiency of signal transmission time of prior art step frequency system, a plurality of emission array elements that the invention provides a kind of MIMO of utilization array emission simultaneously in individual pulse covers the pulse signal of different frequency bands, processes echo component corresponding to the different pulses of separation at receiving end by matched filtering and by the fan sweeping formation method of its synthetic UWB signal.

The technical solution adopted for the present invention to solve the technical problems comprises the following steps:

1) setting is respectively M and N for emission array element and the reception element number of array of the MIMO array of fan sweeping imaging, and receiving array is N unit uniform straight line array;

2) the cross correlation function peak value of M pulse signal is less than or equal to 0.2 times of its autocorrelation peak, and total frequency span of pulse signal equals the bandwidth of single UWB pulse signal; Utilize M of MIMO array emission array element to launch M pulse signal in individual pulse simultaneously, complete the spatial sampling to target area in the individual pulse irradiation time, utilize N unit reception linear array to be gathered echo, the echo s on n array element _n(t) be the time domain stack of this M separate pulse signal after different delay and decay; After being collected echo, utilize individual the transmitting of M to carry out respectively the matched filtering processing to N the echo received on array element, obtain M group matched filtering output component;

3) the matched filtering output component is carried out to the UWB signal and synthesize, process is as follows:

(a) N matched filtering output component in every group carried out to wave beam formation, by regulating the beam position angle, make target area be covered by Q wave beam, obtain altogether Q the wave beam on angle and export; M group matched filtering output component is all carried out to identical multi-beam and process, obtain altogether MQ component, according to the beam position angle, be divided into the Q group, every group contains M and has the wave beam output component that same beam is pointed to angle;

(b) for the output of Q group wave beam, M component in every group sued for peace; During summation, M wave beam exported at the enterprising row alignment of time domain, then directly this M wave beam output addition obtained to single wave beam output, finally obtain Q the wave beam output formed by the UWB signal;

4) extract the intensity of this Q wave beam output, obtain two-dimentional fan sweeping intensity map.

The invention has the beneficial effects as follows: the ultimate principle of institute of the present invention extracting method has been passed through theoretical derivation, embodiment has been passed through the checking of Computerized Numerical Simulation, its result shows: method of the present invention utilizes the MIMO array to launch the independent signal that a plurality of bandwidth are less in individual pulse simultaneously, carry out Combined Treatment by the signal less to these bandwidth, the final acquisition and high orientation and High Range Resolution like the UWB class signal that uses single large bandwidth, overcome in the step frequency imaging system shortcoming of the overlong time that transmits.

The accompanying drawing explanation

Fig. 1 is emission array element random arrangement, receives battle array for the MIMO array of uniform straight line array;

Fig. 2 is that emission array is that uniform straight line array, reception battle array are the MIMO array of uniform straight line array;

Fig. 3 is the flow process of key step in the present invention;

Fig. 4 processes the flow process that echo obtains high-resolution fan sweeping figure;

Fig. 5 is the frequency spectrum that 10 bandwidth are the LFM signal of 30kHz, and its total frequency span equals 300kHz;

Fig. 6 is the beam pattern of step frequency array and MIMO array, and array element is weighted to even weighting, and main lobe points to 0 °.Wherein, subgraph (a) is whole beam pattern, and subgraph (b) is partial enlarged drawing;

Fig. 7 (a) is the relative position of imaging array and target, is (b) distribution situation that target " Fur " is tieed up in azimuth dimension and distance;

Fig. 8 (a) is the fan sweeping imaging results of step frequency array, is (b) the fan sweeping imaging results of MIMO array in the present invention.

Embodiment

Below in conjunction with drawings and Examples, the present invention is further described, the present invention includes but be not limited only to following embodiment.

Main contents of the present invention have:

1. utilize M emission array element of MIMO array to launch M separate pulse signal in individual pulse simultaneously, as M the unequal continuous wave of centre frequency (Continuous Wave, CW) the separated linear frequency modulation of a pulse or M frequency band (Linear Frequency Modulation, LFM) pulse.This M separate pulse total bandwidth equates with the bandwidth of single UWB pulse.Utilize linear array to be received echo, and utilize matched filtering to process and isolate echo component corresponding to different pulses.Process respectively these echo component, and it is carried out to the UWB signal and synthesize, obtain final fan sweeping figure.

2. provided beam pattern (synthesizing) corresponding to method in the beam pattern (utilize a plurality of pulses synthetic) of step frequency array and the present invention by Computerized Numerical Simulation in individual pulse, with beam pattern, illustrated that the method in the present invention can obtain the azimuthal resolution identical with the step frequency array.

3. provided the fan sweeping imaging results of method in step frequency array and the present invention by Computerized Numerical Simulation, from imaging results, proved the present invention that method only utilizes individual pulse can obtain the step frequency array and use just getable fan sweeping imaging results of a plurality of pulses.

Technical scheme of the present invention can be divided into following 4 steps:

5) set emission array and the receiving array parameter for the MIMO array of fan sweeping imaging.Emission array element and reception element number of array are respectively M and N.Because transmitting in the present invention is separate, therefore emission battle array does not become directional wave beam at transmitting terminal, and MIMO array emission individual pulse can complete the spatial sampling to target area.In addition, this step is to the formation of emission battle array without specific (special) requirements, and the emission battle array can be uniform straight line array, can be non-homogeneous line array, can be also the random formation of array element random arrangement.For the ease of echo being carried out to the processing such as multi-beam formation, this step is made as N unit uniform straight line array by receiving array.

6) synchronized transmissions of M pulse signal, reception and matched filtering are processed.The cross correlation function peak value of these pulse signals need to be less than or equal to 0.2 times of its autocorrelation peak, and total frequency span of pulse signal equals the bandwidth of single UWB pulse signal.Because the cross correlation function between M pulse signal is very low, therefore can think that it is separate transmitting, thereby transmitting terminal is non-direction.Utilize M emission array element of MIMO array to launch these pulses in individual pulse simultaneously, therefore in the individual pulse irradiation time, just can complete the spatial sampling to target area.Utilize N unit to receive linear array echo is gathered, n(n=1,2 ..., N) the echo s on individual array element _n(t) can regard the time domain stack of this M separate pulse signal after different delay and decay as.After being collected echo, utilize individual the transmitting of M to carry out respectively the matched filtering processing to N the echo received on array element.With m(m=1,2 ..., M) individual transmitting as example, carry out the matched filtering processing with it to the echo on N array element, can obtain N the output component be comprised of m the echo transmitted.Therefore, M the common acquisition M group matched filtering output component that transmits.

7) output of matched filtering is carried out to the UWB signal and synthesize, its process can be divided into following 2 parts:

(a) N matched filtering output component in every group carried out to wave beam formation, by regulating the beam position angle, make target area be covered by Q wave beam, obtain altogether Q the wave beam on angle and export.M group matched filtering output component is all carried out to identical multi-beam and process, obtain M group wave beam output (every group wave beam output corresponding different frequency bands), altogether obtain MQ component.All use same group of beam position angle owing to processing every group of matched filtering output, so MQ wave beam output can be divided into the Q group according to the beam position angle, every group contains M the wave beam output component with same beam sensing angle.

(b), for the output of Q group wave beam, M the component (being the identical wave beam output in beam position angle) in every group sued for peace.Need to, by M wave beam output at the enterprising row alignment of time domain, then directly this M wave beam output addition be obtained to single wave beam output during summation.Because the process of summation is synthesized M wave beam output corresponding to frequency band, be equivalent to utilize a plurality of signals than narrow-band to synthesize the UWB signal, finally obtain Q the wave beam output formed by the UWB signal.

8) extract the intensity of this Q wave beam output, obtain two-dimentional fan sweeping intensity map.

Below each step of the present invention is elaborated:

Correlation theory and particular content that step 1) relates generally to are as follows:

The emission element number of array of MIMO array is M, and its formation is unfixing, can be uniform straight line array, and non-homogeneous line array, can be also the array of random arrangement.Receiving battle array is N unit line array, and its array element distance is d _r.The MIMO array of emission array element random arrangement as shown in Figure 1.When emission array element is no more than the receiving array size to the ultimate range of receiving array geometry mid points, can regard this MIMO array as single base array.For fear of the repetition and loaded down with trivial details of narration, the situation that the emission battle array of below take is uniform straight line array is carried out the description problem as example.That is: emission battle array is M unit uniform straight line array, and array element distance is d _t.Emitting linear battle array and reception line array are parallel to each other, and distance between the two is less than or equal to the size of receiving array.This MIMO array as shown in Figure 2.

Step 2) related correlation theory and particular content are as follows:

The M of MIMO array emission array element launch the individual separate pulse signal of M in individual pulse, and the total bandwidth of M pulse signal equals the bandwidth of single UWB signal,

$B=\underset{m=1}{\overset{M}{\mathrm{\Σ}}}{B}_m---\left(1\right)$

Wherein, B _mbe m(m=1,2 ..., the M) bandwidth of individual pulse signal, the total bandwidth that B is M pulse signal is also the bandwidth of single UWB signal simultaneously.

The form of these pulse signals has multiple, as the unequal CW pulse of a group switching centre frequency or the separated LFM pulse of frequency band.Take the latter as example, and establishing M pulse signal is the separated LFM pulse of frequency band, its complex expression s _m(t) (t in parenthesis represents time domain) is:

$s_m=\left(t\right)=\frac{1}{\sqrt{T}}\mathrm{rect}\left(\frac{t}{T}\right)\exp \left[\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA0000375414300000023.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}(f_{m}t+\frac{1}{2}\frac{B_m}{T}{t}^2)\right]---\left(2\right)$

Wherein, rect () is rectangular window, f _mbe the initial frequency of m LFM pulse, T is pulse width (establishes all pulses and have equal pulse width).

If target is positioned at far field, it can be modeled as P desirable scattering point.M emission array element is launched M the LFM pulse designed simultaneously.Carry out echo acquirement by N unit linear array, n(n=1,2 ..., N) the signal x on individual reception array element _n(t) can regard as this M LFM pulse through different propagation attenuations and the time time domain stack delayed,

$x_n\left(t\right)=\underset{p=1}{\overset{P}{\mathrm{\&Sigma;}}}{\mathrm{\&sigma;}}_p\underset{m=1}{\overset{M}{\mathrm{\&Sigma;}}}{s}_m(t-{\mathrm{\&tau;}}_{\mathrm{tm}}^p-{\mathrm{\&tau;}}_{\mathrm{rn}}^p)+n\left(t\right)---\left(3\right)$

Wherein, σ _pbe p(p=1,2 ..., the P) scattering strength of individual scattering point, P is the scattering point number,

(m=1,2) are the time delay of m emission array element to p scattering point,

(n=1,2,, be N) time delay of p scattering point to n reception array element, n (t) represents noise item.

Impulse Response Function h with m the corresponding matched filter that transmits _m(t) can be expressed as

$h_m\left(t\right)={\left[s_m(T-t)\right]}^c---\left(4\right)$

Wherein, [] ^cconjugation is got in representative.With M matched filter, N the echo received on array element carried out to matched filtering, can obtain MN output.Wherein (m-1) N+n output can be expressed as y _{(m-1) N+n}(t), its expression formula is

$y_{(m-1)N+n}\left(t\right)=x_n\left(t\right)*h_m\left(t\right)---\left(5\right)$

Wherein convolution is asked in the * representative.

When ignoring the Doppler shift of echo, matched filtering is processed to be equivalent to signal is asked to relevant.Therefore, the output of matched filter can be regarded as the time domain stack of the autocorrelation function that transmits and cross correlation function, and formula (5) can be rewritten as

$y_{(m-1)N+n}\left(t\right)=\underset{p=1}{\overset{P}{\mathrm{\&Sigma;}}}{\mathrm{\&sigma;}}_p[R_m(t-{\mathrm{\&tau;}}_{\mathrm{tm}}^p-{\mathrm{\&tau;}}_{\mathrm{rn}}^p-T)+\underset{i\&NotEqual;m}{\overset{M}{\underset{i=1}{\mathrm{\&Sigma;}}}}{R}_{m,i}(t-{\mathrm{\&tau;}}_{\mathrm{ti}}^p-{\mathrm{\&tau;}}_{\mathrm{rn}}^i-T)]+n\left(t\right)*h_m\left(t\right)---\left(6\right)$

Wherein, R _m(t) be m exomonental autocorrelation function, R _m,i(t) be the cross correlation function between m transponder pulse and other pulses, the meaning of i is the same with m, is the numbering of emission array element.

When auto-correlation and the cross correlation function of pulse signal meets following formula:

$\frac{\max \left[R_{m,i}\left(t\right)\right]}{\max \left[R_m\left(t\right)\right]}\&le;0.2---\left(7\right)$

Can think between pulse it is separate.Wherein, max[] represent maximizing.In addition, the relevant output when transponder pulse and noise meets

$\frac{\max [n\left(t\right)*h_m\left(t\right)]}{\max \left[R_m\left(t\right)\right]}\&le;0.2---\left(8\right)$

Can think between transponder pulse and noise it is incoherent.Thereby, after the relevant output that neglects the simple crosscorrelation item and transmit to noise, formula (6) can be reduced to the output that only comprises the autocorrelation function item:

$y_{(m-1)N+n}\left(t\right)=\underset{p=1}{\overset{P}{\mathrm{\&Sigma;}}}{\mathrm{\&sigma;}}_p{R}_m(t-{\mathrm{\&tau;}}_{\mathrm{tm}}^p-{\mathrm{\&tau;}}_{\mathrm{rn}}^p-T)---\left(9\right)$

From formula (9), MN matched filtering output can be reduced to MN the stack of autocorrelation function after different delay.This MN matched filtering output can be divided into according to transmitting the M group, and every group comprises N matched filtering output.

Correlation theory and particular content that step 3) relates to are as follows:

(a) matched filtering output is carried out to wave beam formation

N matched filtering output component in every group carried out to wave beam formation, by regulating the beam position angle, make target area be covered by Q wave beam, obtain altogether Q the wave beam on angle and export.Form example with the time delay wave beam, the N in the m group matched filtering output is processed, its expression formula is:

$B_q^m\left(t\right)\text{=}\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{A}_{(m-1)N+n}^q\underset{p=1}{\overset{P}{\mathrm{\&Sigma;}}}{\mathrm{\&sigma;}}_p{R}_m(t-{\mathrm{\&tau;}}_{\mathrm{tm}}^p-{\mathrm{\&tau;}}_{\mathrm{rn}}^p-T+{\mathrm{\&tau;}}_{(m-1)N+n}^q)---\left(10\right)$

Wherein,

q the wave beam output that representative transmits corresponding with m,

be the amplitude weighting under q wave beam,

be q the delay volume that wave beam is corresponding.

Process one group of matched filtering output and can obtain Q wave beam output, M group matched filtering output obtains MQ wave beam output altogether.All use same group of beam position angle owing to processing every group of matched filtering output, so MQ wave beam output can be divided into the Q group according to the beam position angle, every group contains M the wave beam output component with same beam sensing angle.

(b) to wave beam, output is synthesized, and obtains the UWB signal

For the output of Q group wave beam, M the component (being the identical wave beam output in beam position angle) in every group sued for peace.To the output of MQ wave beam according to orientation angle be concerned with summation (be about to MQ wave beam export in the identical wave beam in beam position angle export sued for peace), obtain a final Q wave beam, its expression formula is:

$B_q\left(t\right)=\underset{m=1}{\overset{M}{\mathrm{\&Sigma;}}}{B}_q^m\left(t\right)---\left(11\right)$

Wherein, B _q(t) be q(q=1,2 ..., Q) the final output of individual wave beam.According to formula (11), can find out, summation process is synthesized M wave beam output corresponding to LFM pulse.Because this M LFM pulse covers different frequency band ranges, and its total frequency band equals the frequency band of single UWB pulse.Therefore the summation process of formula (11) is equivalent to synthetic UWB signal, obtains Q the wave beam output be comprised of the UWB signal.

Correlation theory and particular content that step 4) relates to are as follows:

Extract the intensity of this Q UWB wave beam output, obtain the fan sweeping figure of target.In the present invention so that amplitude output is taken absolute value into example, that is:

$I_q\left(t\right)=\left|B_q\left(t\right)\right|---\left(12\right)$

As shown in Figure 3, the flow process that echo is processed to obtain fan sweeping figure as shown in Figure 4 for key step flow process of the present invention.

The fan sweeping imaging process under water of take typically is example, provides embodiment of the present invention.Embodiment is verified respectively the validity of institute's extracting method the present invention from the result of beam pattern and fan sweeping imaging.

Suppose to transmit into sound wave, its underwater velocity of propagation is 1500 meter per seconds.The MIMO array has 10 emission array elements and 24 reception array elements.10 emission array element half-wavelengths corresponding according to the 50kHz signal are that spacing forms the uniform line array, and 24 receive array element to take half-wavelength corresponding to 100kHz signal be that spacing forms the uniform line array.Emission line array and reception linear array are parallel to each other, and distance between the two equals to launch the spacing of array element.This type MIMO array as shown in Figure 2.

(1). the contrast of array beams figure

If 10 of the MIMO array emission array element (in emulation, the individual pulse width is made as 4 milliseconds) LFM pulses that transmitted bandwidth is 30kHz in individual pulse in the present invention simultaneously, the frequency band range of 10 LFM pulses is respectively 100kHz-130kHz, 130kHz-160kHz, 160kHz-190kHz, 190kHz-220kHz, 220kHz-250kHz, 250kHz-280kHz, 280kHz-310kHz, 310kHz-340kHz, 340kHz-370kHz and 370kHz-400kHz.The frequency spectrum of these 10 LFM pulses as shown in Figure 5.Beam pattern corresponding with each frequency band in the present invention can obtain like this: the frequency band of 30kHz is divided into to 31 frequencies according to the step-length of 1kHz, by the beam pattern coherence stack on these 31 frequencies, obtains beam pattern corresponding to 30kHz frequency band.Finally, by the stack of the beam pattern on 10 frequency bands, obtain the beam pattern of MIMO array in the present invention.

In order to be contrasted, establishing the step frequency array is 1 24 array of receiving, and receives battle array identical with the reception battle array of MIMO array.Its single emission array element is divided and is launched respectively 10 LFM pulse signals for 10 times.The beam pattern of step frequency array can obtain like this: be step-length by the frequency span of 100kHz-400kHz according to 1kHz, be divided into 301 frequencies, by the stack of the beam pattern on these 301 frequencies, obtain the beam pattern of step frequency array.

After the stack of the beam pattern by a plurality of frequencies, in the beam pattern of step frequency array and the present invention, the beam pattern of MIMO array as shown in Figure 6.By Fig. 6 (a), can be found out, the beam pattern of step frequency array is almost identical with the beam pattern of MIMO array.The partial enlarged drawing that Fig. 6 (b) is both beam patterns, therefrom can find out, although there are some fine differences in beam pattern, its main lobe width and the first side lobe levels are identical.Beam pattern in comparison diagram 6 can find out, the method in the present invention can obtain the beam pattern almost identical with the step frequency array, and the main lobe width of beam pattern and side lobe levels all equate.

(2). the contrast of fan sweeping imaging results

In completeer UWB array and the present invention, after the beam pattern of MIMO array, then utilize MIMO array in UWB array and the present invention to carry out the fan sweeping imaging.It specifically is implemented as follows:

1) setting array, transmit and the parameter of target:

Keep array parameter and the transmission signal parameters of step frequency array and MIMO array constant.The reception battle array of step frequency array is positioned on the x axle and centered by true origin.MIMO array present position as shown in Figure 2.No matter be step frequency array or MIMO array, its single pulsewidth transmitted is 4 milliseconds.

Target forms three letters " Fur ", and scattering coefficient is 1.The scattering strength of other scattering points of target area is made as 0.05.Relative position under three-dimensional system of coordinate of imaging array and target, the distribution situation of target on azimuth dimension and distance dimension are as shown in Figure 7.

2) carry out two-dimentional fan sweeping imaging:

At transmitting terminal, the single emission array element of step frequency array is divided and is launched respectively 10 bandwidth LFM pulse for 10 times, and obtains the fan sweeping figure of target according to the Echo Processing process of step frequency system.In the present invention, 10 of the MIMO array emission array elements are launched 10 LFM pulses within the launch time of individual pulse simultaneously, according to the flow processing echo of Fig. 3 and Fig. 4, obtain the fan sweeping imaging results.

Signal to noise ratio (S/N ratio) on two array received array element all is made as 4dB, and institute's plus noise is white Gaussian noise.Receiving end adopts time delay wave beam formation processing, and the amplitude weighting value on all array element is 1.While extracting the intensity of each wave beam output, be all to take absolute value and get final product according to time series.The fan sweeping imaging results of step frequency array and MIMO array as shown in Figure 8.In Fig. 8, the fan sweeping imaging results that subgraph (a) is the step frequency array, the fan sweeping imaging results that subgraph (b) is the MIMO array.From imaging results, can find out, MIMO array and step frequency array in the present invention have almost identical imaging results, and namely both azimuthal resolutions and range resolution equate.

According to embodiment, can think: a plurality of emission array element in the MIMO array of utilizing proposed in the present invention is launched the fan sweeping formation method that the signal that covers different frequency bands synthesizes the UWB signal simultaneously, can effectively avoid in the step frequency system the transmitting shortcoming of overlong time, can obtain the fan sweeping figure with high orientation and High Range Resolution in the cycle at individual pulse.

Claims (1)

1. the fan sweeping formation method based on ultra broadband MIMO array, is characterized in that comprising the steps:

1) setting is respectively M and N for emission array element and the reception element number of array of the MIMO array of fan sweeping imaging, and receiving array is N unit uniform straight line array;

2) the cross correlation function peak value of M pulse signal is less than or equal to 0.2 times of its autocorrelation peak, and total frequency span of pulse signal equals the bandwidth of single UWB pulse signal; Utilize M of MIMO array emission array element to launch M pulse signal in individual pulse simultaneously, complete the spatial sampling to target area in the individual pulse irradiation time, utilize N unit reception linear array to be gathered echo, the echo s on n array element _n(t) be the time domain stack of this M separate pulse signal after different delay and decay; After being collected echo, utilize individual the transmitting of M to carry out respectively the matched filtering processing to N the echo received on array element, obtain M group matched filtering output component;

3) the matched filtering output component is carried out to the UWB signal and synthesize, process is as follows:

(a) N matched filtering output component in every group carried out to wave beam formation, by regulating the beam position angle, make target area be covered by Q wave beam, obtain altogether Q the wave beam on angle and export; M group matched filtering output component is all carried out to identical multi-beam and process, obtain altogether MQ component, according to the beam position angle, be divided into the Q group, every group contains M and has the wave beam output component that same beam is pointed to angle;

(b) for the output of Q group wave beam, M component in every group sued for peace; During summation, M wave beam exported at the enterprising row alignment of time domain, then directly this M wave beam output addition obtained to single wave beam output, finally obtain Q the wave beam output formed by the UWB signal;

4) extract the intensity of this Q wave beam output, obtain two-dimentional fan sweeping intensity map.

Images