CN103744078B - A kind of microwave based on different code speed random frequency hopping stares relevance imaging device - Google Patents

Abstract

The present invention discloses a kind of microwave based on different code speed random frequency hopping and stares relevance imaging device, comprise the control information that random radiation unit sends according to Master Control Unit generate microwave pulse signal and launch, microwave pulse signal forms the microwave radiation field of space-time bidimensional random character in target area, the scatter echo of target area observed object is received by receiving element, and scatter echo and microwave radiation field are carried out association process and obtain inversion chart as observed object by relevance imaging unit; The recurrence interval of the microwave pulse signal that each radiating antenna is launched is identical with pulse repetition rate, microwave pulse signal comprises multiple random frequency hopping subpulse, its frequency is Stochastic choice in bandwidth range, and the random frequency hopping subpulse frequency hopping code speed of the microwave pulse signal that different radiating antenna is launched is different and frequency hopping pattern is orthogonal.Launch at low bit rate, under the condition of low speed collection and lower bandwidth, achieve microwave from engineering and stare needed for relevance imaging, ideal space-time bidimensional random radiation field.

Description

A kind of microwave based on different code speed random frequency hopping stares relevance imaging device

Technical field

The present invention relates to radar imaging technology field, particularly relate to a kind of microwave based on different code speed random frequency hopping and stare relevance imaging device.

Background technology

Radar imagery (RadarImaging) technology is a leap in radar development history, it has expanded the function of the initial detection of radar (Detection) and range finding (Ranging), it occurs making radar can utilize the electromagnetic scattering information obtained, and obtains the panoramic radar image to scene.Although synthetic aperture radar (SAR) has high azimuth resolution, its revisiting period is long, under needing long-time (standard) to stare the scene of observation and imaging continuously, there is inevitable congenital inferior position; Traditional real aperture radar staring imaging, its angular resolution limits by actual antennas array aperture, limits its application in practice.

Relevance imaging is stared for microwave, desirable space-time bidimensional random radiation field realizes the condition precedent that above-mentioned microwave stares relevance imaging, when its random character shows as, the uncorrelated nature of empty bidimensional, that is: between the radiation field in observation area on any different resolution element, there is irrelevant feature, between the radiation field not in the same time in observation area, there is irrelevant feature.

The random character factor affecting space-time bidimensional random radiation field mainly comprises the form of radar array transponder pulse signal, bandwidth, code speed, and the far field amplitude-phase distribution etc. of emitting antenna under the spatial arrangement of emission array and different frequency.How under the engineering specifications of limited radar array scale, limited signal bandwidth, lower code speed, when structure random radiation relevance imaging radar array is to realize good, empty bidimensional random radiation field is still a unsolved technical barrier.

Summary of the invention

The object of the embodiment of the present invention is to provide a kind of microwave based on different code speed random frequency hopping and stares relevance imaging device, when realizing good, empty bidimensional random radiation field.

The object of the embodiment of the present invention is achieved through the following technical solutions:

Microwave based on different code speed random frequency hopping stares a relevance imaging device, comprises random radiation unit, Master Control Unit, receiving element, relevance imaging unit:

The control information that described random radiation unit sends according to described Master Control Unit generates microwave pulse signal and launches, described microwave pulse signal when target area is formed, the radiation field of empty bidimensional random character, in target area, the scatter echo of observed object is received by described receiving element, described scatter echo and described radiation field are carried out association process by described relevance imaging unit, obtain the inversion chart picture of observed object;

Wherein, the recurrence interval of the described microwave pulse signal that each radiating antenna is launched is identical with pulse repetition rate, described microwave pulse signal comprises multiple random frequency hopping subpulse, the frequency of described random frequency hopping subpulse is Stochastic choice in bandwidth range, and the random frequency hopping subpulse code speed of the described microwave pulse signal that different radiating antenna is launched is different and frequency hopping pattern is orthogonal.

The technical scheme provided as can be seen from the invention described above embodiment, microwave based on different code speed random frequency hopping stares relevance imaging device, under limited signal bandwidth and lower random frequency hopping code speed condition, when target area defines better, the radiation field of empty bidimensional random character, overcome existing random frequency hopping radar array produce the undesirable shortcoming of radiation field randomness, improve microwave radiation field time, empty bidimensional random character, reduce the redundancy of scatter echo sample, be beneficial to realize microwave and stare relevance imaging, obtain the high-resolution surmounting antenna aperture restriction.

Accompanying drawing explanation

In order to be illustrated more clearly in the technical scheme of the embodiment of the present invention, below the accompanying drawing used required in describing embodiment is briefly described, apparently, accompanying drawing in the following describes is only some embodiments of the present invention, for those of ordinary skill in the art, under the prerequisite not paying creative work, other accompanying drawings can also be obtained according to these accompanying drawings.

Fig. 1 is that the embodiment of the present invention stares relevance imaging device schematic diagram based on the microwave of different code speed random frequency hopping.

To be the embodiment of the present invention stare relevance imaging device based on the microwave of different code speed random frequency hopping to Fig. 2 specifically forms schematic diagram.

Fig. 3 is that the embodiment of the present invention stares relevance imaging device different code speed random frequency hopping pulse signal schematic diagram based on the microwave of different code speed random frequency hopping.

To be the embodiment of the present invention stare relevance imaging device microwave based on the microwave of different code speed random frequency hopping to Fig. 4 stares relevance imaging observation scene configuration schematic diagram.

Fig. 5 is that the embodiment of the present invention stares observed object backscattering coefficient distribution schematic diagram in relevance imaging device observation area based on the microwave of different code speed random frequency hopping.

Fig. 6 is that the embodiment of the present invention stares relevance imaging device each random radiation unit under transmitting same code speed random frequency hopping signal and different code speed random frequency hopping RST, the two scattering point O that observed object is closed on based on the microwave of different code speed random frequency hopping _p, O _qradiation field and the enantiomorphic relationship schematic diagram of transmitted waveform sampling time.

Fig. 7 is that the embodiment of the present invention stares the subcode hop period of relevance imaging device at different code speed random frequency hopping signal within the scope of 34ns ~ 46ns in Stochastic choice situation, at observed object t1 and t2 moment normalized microwave random radiation field pattern schematic diagram based on the microwave of different code speed random frequency hopping.

Fig. 8 is that the embodiment of the present invention stares relevance imaging device under same code speed random frequency hopping RST, microwave random radiation field spatial coherence and the simulation imaging result schematic diagram to Fig. 5 observed object based on the microwave of different code speed random frequency hopping.

Fig. 9 is that the embodiment of the present invention stares relevance imaging device under different code speed random frequency hopping RST (± 15% variation range), microwave random radiation field spatial coherence and the simulation imaging result schematic diagram to Fig. 5 observed object based on the microwave of different code speed random frequency hopping.

Figure 10 is that the embodiment of the present invention stares relevance imaging device each random radiation unit under the lower different code speed random frequency hopping signal of transmitting and high 10 times of same code speed random frequency hopping RST, observed object microwave random radiation field sample time correlation curve schematic diagram based on the microwave of different code speed random frequency hopping.

Figure 11 is that the embodiment of the present invention stares relevance imaging device under 10 times of same code speed random frequency hopping RSTs, microwave random radiation field spatial coherence and the simulation imaging result schematic diagram to Fig. 5 observed object based on the microwave of different code speed random frequency hopping.

Embodiment

Below in conjunction with the accompanying drawing in the embodiment of the present invention, be clearly and completely described the technical scheme in the embodiment of the present invention, obviously, described embodiment is only the present invention's part embodiment, instead of whole embodiments.Based on embodiments of the invention, those of ordinary skill in the art, not making the every other embodiment obtained under creative work prerequisite, belong to protection scope of the present invention.

Form the desirable random microwave radiation field of space-time bidimensional in target area based on the primary precondition realizing high-resolution microwave and stare relevance imaging, when its random character shows as, the uncorrelated nature of empty bidimensional, that is: between the radiation field in target area on any diverse location, there is irrelevant feature, between the radiation field of not target area in the same time, there is irrelevant feature.In engineering, under the pulse random signal form condition of Finite Array scale and finite bandwidth, comparatively low bit rate (≤100Mb/s), how design and implimentation microwave stares relevance imaging radar array to improve the random character of microwave radiation field space-time bidimensional is the key difficult problem that microwave stares the practical application of relevance imaging technological direction.

As shown in Figure 1, the embodiment of the present invention provides a kind of microwave based on different code speed random frequency hopping to stare relevance imaging device, comprises random radiation unit 1, Master Control Unit 2, receiving element 3, relevance imaging unit 4:

The control information that random radiation unit 1 sends according to Master Control Unit 2 generates microwave pulse signal and launches, described microwave pulse signal when target area is formed, the radiation field of empty bidimensional random character, in target area, the scatter echo of observed object is received by receiving element 3, described scatter echo and described radiation field are carried out association process by relevance imaging unit 4, obtain the inversion chart picture of observed object;

Wherein, the recurrence interval of the described microwave pulse signal that each radiating antenna is launched is identical with pulse repetition rate, described microwave pulse signal comprises multiple random frequency hopping subpulse, the frequency of described random frequency hopping subpulse is Stochastic choice in bandwidth range, and the random frequency hopping subpulse code speed of the described microwave pulse signal that different radiating antenna is launched is different and frequency hopping pattern is orthogonal.

The technical scheme provided as can be seen from the invention described above embodiment, the hop period of the random frequency hopping subpulse of the described microwave pulse signal that different radiating antenna is launched is different, and namely subpulse frequency hopping code speed is different.The radiation field that described microwave pulse signal is encouraged by aerial array in the irrelevant superposition in target observation space, when target area defines better, the radiation field of empty bidimensional random character.

And, microwave pulse signal is launched by aerial array, encouraged by aerial array and form microwave electromagnetic field (also can be called microwave random radiation field or random radiation field), target area is beam coverage area, formed after radiation field and observed object effect and be scattered back wave field, scatter echo is by single antenna reception.

Visible, the embodiment of the present invention stares relevance imaging device based on the microwave of different code speed random frequency hopping, realize under Finite Array scale and limited signal bandwidth and lower random frequency hopping code speed condition, by launching different code speed random frequency hopping pulse signal, when target area defines better, the radiation field of empty bidimensional random character, overcome existing random frequency hopping radar array produce the undesirable shortcoming of radiation field randomness, improve radiation field time, empty bidimensional random character.Receiver can adopt low speed ADC(AnalogtoDigitalConverter, A-D converter) sampling, still obtain effective target scattering echo samples, reduce the redundancy of scatter echo sample.The target imaging effect obtained is better, and resolution is higher, obtains the high-resolution surmounting antenna aperture restriction.

The embodiment of the present invention stares relevance imaging application of installation in radar imaging technology based on the microwave of different code speed random frequency hopping, and the microwave that can be understood as different code speed random frequency hopping stares relevance imaging radar array.

The embodiment of the present invention stares relevance imaging device based on the microwave of different code speed random frequency hopping, can in bandwidth range the frequency of Stochastic choice random frequency hopping subpulse, bandwidth is generally less than 1GHz, but does not strictly limit.

The embodiment of the present invention is stared in relevance imaging device based on the microwave of different code speed random frequency hopping, as a kind of different code speed selection modes of random frequency hopping subpulse, between random radiation unit, mutual code speed difference can at certain limit Stochastic choice, the random frequency hopping subpulse code speed sizes values prime number (relatively prime code speed scheme) each other of the microwave pulse signal launched as selected different radiating antenna.

Exemplary, relatively prime code speed scheme, as 23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97 etc., but be not limited.

As shown in Figure 2, the microwave based on different code speed random frequency hopping stares relevance imaging device, comprises random radiation unit 1, Master Control Unit 2, receiver 3, relevance imaging unit 4.Random radiation unit can be multiple, and number is N.

Specifically, Master Control Unit 2 can comprise PLL (PhaseLockedLoop, phaselocked loop) local oscillator 21, system clock 22, random frequency hopping selects and code speed control subunit 23 and random signal control and sequential control subelement 24:

PLL local oscillator 21, for providing the stable reference local oscillator carrier wave needed for described random radiation unit up-conversion and described receiving element down coversion.

System clock 22, for for described Master Control Unit, random radiation unit and receiver 3 providing source are from the high-frequency stable reference clock signal of same constant-temperature crystal oscillator.

Random frequency hopping is selected and code speed control subunit 23, for generation of DDS (DirectDigitalSynthesizer, direct digital frequency synthesier) the baseband signal control word controlling frequency hopping pattern and hop period.Corresponding, be appreciated that Master Control Unit 2 sends to the control information of random radiation unit 1 can be baseband signal control word.

Random signal controls and sequential control subelement 24, for generation of steering order and the synchronous triggering signal of local oscillator carrier wave, random frequency hopping subpulse baseband signal waveform.

Still with reference to shown in figure 2, specifically, random radiation unit can comprise DDS subelement 11, frequency mixer subelement 12, bandpass filter subelement 13, radio-frequency (RF) power amplification subelement 14 and radiating antenna 15:

DDS subelement 11, for under the control of the synchronous triggering signal that described random signal controls and sequential control subelement sends, utilize from the DDS baseband signal control word that described random frequency hopping is selected and code speed control subunit receives, synthesize and export the baseband waveform signal of random frequency hopping subpulse to described frequency mixer subelement;

Frequency mixer subelement 12, for realizing up-conversion modulation, makes the base-band signal spectrum of input random frequency hopping subpulse move in the frequency range of local oscillator carrier wave, and exports random frequency hopping radiofrequency signal to described bandpass filter subelement;

Bandpass filter subelement 13, for carrying out filtering for random frequency hopping radiofrequency signal;

Radio-frequency (RF) power amplification subelement 14, carries out power amplification for random frequency hopping radiofrequency signal, and is launched by radiating antenna 15.

Visible, under the control of the synchronous triggering signal that DDS subelement sends at Master Control Unit, utilize the DDS baseband signal control word received, synthesize and export the baseband waveform signal of the fast random frequency hopping of satisfactory different code; Frequency mixer subelement is used for realizing up-conversion modulation, makes the different code speed random frequency hopping base-band signal spectrums of input move in the frequency range of local oscillator carrier wave; The random frequency hopping radiofrequency signal that bandpass filter subelement is used for for each random radiation unit is launched carries out filtering, the noise that filtering is unnecessary, improves signal to noise ratio (S/N ratio); Radio-frequency (RF) power amplification subelement is used for the random frequency hopping pulse signal of different code speed to carry out power amplification, makes it the radiated power requirements meeting relevance imaging system, keeps the shape of microwave pulse signal simultaneously.

Multiple radiating antenna forms aerial array, aerial array can adopt intensive or sparse antenna array, aerial array configuration can be that fixing static state or random variation are dynamic, can be evenly arrangement or non-homogeneous arrangement, for under the excitation of described random frequency hopping microwave pulse signal, when being formed in target area, empty bidimensional random radiation field.

Still with reference to shown in figure 2, specifically, receiving element can comprise receiving antenna 31, radio frequency subelement 32 and echo acquirement subelement 33:

Receiving antenna 31, for receiving the scatter echo of observed object;

Radio frequency subelement 32, for amplifying and filtering the described scatter echo received;

Echo acquirement subelement 33, for sampling to amplification and filtered described scatter echo;

Embodiment of the present invention microwave stares relevance imaging device, and receiving element can be receiver, concrete, can be single antenna single-channel receiver.

Simple declaration, receiving antenna 31 receives for the high-gain of observation area target scattering echoed signal.Radio frequency subelement 32 can comprise low noise amplifier, low-converter, bandpass filter etc., receiving the amplification of scatter echo signal and the function of filtering, ensureing that receiver has sufficiently high gain and signal to noise ratio (S/N ratio) for realizing.Echo acquirement subelement 33 can comprise that intermediate frequency amplifies, AD sampling module, for completing the functions such as the sampling that receives scatter echo signal and storage.And then the high-performance that receiving element realizes observed object scatter echo signal receives and sampling functions.

Still with reference to shown in figure 2, specifically, relevance imaging unit can comprise echo data optimization subelement 41, radiation field calculation subelement 42, association process subelement 43 and inversion chart picture display subelement 44:

Echo data optimizes subelement 41, for carrying out de-redundancy and optimum choice to the described scatter echo data after sampling;

Radiation field calculation subelement 42, for calculating the radiation field of target area;

Association process subelement 43, carries out association process for the radiation field calculated the described scatter echo after optimization and radiation field calculation subelement 42;

Inversion chart picture display subelement 44, exports for the reconstruct of realize target image and the image of inverting.

Simple declaration, echo data is optimized subelement and is carried out de-redundancy and optimum choice to receiving a large amount of scatter echo data gathered, and improves the association process validity of scatter echo data.Here, in order to obtain abundant orthogonal radiation field sample, the scatter echo signal received receiver carries out high-speed sampling and obtains enough echo datas.Consider it is not that the radiation field of any two different sampling instants has good orthogonality, namely there is a large amount of redundancies in sampled data, therefore, need be optimized, selects it, reduces redundancy and the process complexity of data.

Radiation field calculation subelement can stare relevance imaging apparatus system parameter, the different code speed parameter such as random frequency hopping signal parameter and aerial array configuration according to microwave, completes the calculation of observed object radiation field, specifically describes see hereinafter formula 2.

Association process subelement utilizes relevance imaging algorithm, carries out association process to the radiation field sample of the scatter echo data received and known calculation, extracts the different information of radiation field distribution, for the decoupling zero of target information, and the scattering coefficient distribution of inverting target.And then relevance imaging unit realizes the scatter echo of reception and the radiation field information that calculation obtains to carry out the imaging results that association process obtains observed object.

Relevance imaging algorithm, (BP), orthogonal matching pursuit (OMP), management loading (SBL) etc. are followed the trail of in the such as directly association of single order field intensity or the association of high-order field intensity, optimization algorithm such as the base met under target sparse condition.

Stare relevance imaging device to the embodiment of the present invention based on the microwave of different code speed random frequency hopping below in conjunction with formula to be described, as shown in Figure 3, transmitter 1 to transmitter N launches the microwave pulse signal of different code speed random frequency hopping respectively.The random frequency hopping subpulse that i-th random radiation unit is launched is expressed as:

$f({{\stackrel{\→}{r}}_i}^T,t)=\underset{m=1}{\overset{M}{\mathrm{\Σ}}}\underset{k=1}{\overset{K}{\mathrm{\Σ}}}\mathrm{rect}\left(\frac{t-{\mathrm{mT}}_t-\frac{2k+1}{2}{T}_{\mathrm{di}}}{T_{\mathrm{di}}}\right)\exp \{j2\mathrm{\π}{f}_{i,\mathrm{mk}}(t-{\mathrm{mT}}_t-{\mathrm{kT}}_{\mathrm{di}})+{\mathrm{j\θ}}_{i,\mathrm{mk}}\}$ Formula 1

Wherein, i=0,1 ..., N-1, N are random radiation element number, be the position of the radiating antenna phase center of i-th random radiation unit, complete recurrence interval is T _t, M recurrence interval, have K random frequency hopping subpulse in the recurrence interval, T _direpresent the subpulse hop period of i-th random radiation unit, f _{i, mk}be the frequency of i-th random radiation unit kth subpulse Frequency Hopping Signal within m recurrence interval, θ _{i, mk}for its first phase, t is the relevance imaging time, requires here to ensure that between all random radiation unit, subpulse frequency hopping pattern is mutually orthogonal.

Visible, the T between any radiating element _diall different, namely their subpulse frequency hopping code speed is different, frequency hopping pattern is orthogonal.Exemplary, as f _1,11with f _{i, 11}hop period is different; f _1,11with f _{i, 11}frequency hopping pattern is orthogonal.

According to the rule of electromagnetic fiele at spatial, in described target area the space-time bidimensional random radiation field at place can be expressed as:

$\begin{array}{c}\mathrm{\Ψ}(\stackrel{\→}{r},t)=\underset{i=1}{\overset{N}{\mathrm{\Σ}}}\underset{t^{\′}}{\∫}G({{\stackrel{\→}{r}}_i}^T,t^{\′},\stackrel{\→}{r},t)f({{\stackrel{\→}{r}}_i}^T,t^{\′}){\mathrm{dt}}^{\′}\\ =\underset{i=1}{\overset{N}{\mathrm{\Σ}}}\frac{1}{4\mathrm{\π}|\stackrel{\→}{r}-{{\stackrel{\→}{r}}_i}^T|}\underset{m=1}{\overset{M}{\mathrm{\Σ}}}\underset{k=1}{\overset{K}{\mathrm{\Σ}}}\left\{\begin{array}{c}\mathrm{rect}\left(\frac{t-\frac{|\stackrel{\→}{r}-{{\stackrel{\→}{r}}_i}^T|}{c}-{\mathrm{nT}}_t-\frac{2k+1}{2}{T}_{\mathrm{di}}}{T_{\mathrm{di}}}\right)*\\ \exp \{j2\mathrm{\π}{f}_{i,\mathrm{mk}}(t-\frac{|\stackrel{\→}{r}-{{\stackrel{\→}{r}}_i}^T|}{c}-{\mathrm{mT}}_t-{\mathrm{kT}}_{\mathrm{di}})+{\mathrm{j\θ}}_{i,\mathrm{mk}}\}\end{array}\right.\end{array}$ Formula 2

Wherein, the transient free-surface Green function of free space electromagnetic fiele, the random frequency hopping subpulse that i-th random radiation unit is launched m recurrence interval, have K random frequency hopping subpulse in the recurrence interval, t is the relevance imaging time, and t ' is the x time of random frequency hopping signal, and c is the light velocity, c=3 × 10 ⁸m/ second;

Synchronization t, in target area the random radiation field at place has the irrelevant feature in space, and its uncorrelated nature is expressed as:

$I({\stackrel{\&RightArrow;}{r}}_1,{\stackrel{\&RightArrow;}{r}}_2,t)=<{\mathrm{\&Psi;}}^{*}({\stackrel{\&RightArrow;}{r}}_1,t)\mathrm{\&Psi;}({\stackrel{\&RightArrow;}{r}}_2,t)>$

Wherein, ensemble average <> represents inner product operation, () ^*represent conjugate transpose.

Not t in the same time ₁, t ₂, in the S objective plane of target area have time irrelevant feature between the random radiation field at place, its uncorrelated nature is expressed as:

$I(t_1,t_2)=\underset{S}{\text{\&Integral;}}{\mathrm{\&Psi;}}^{*}(\stackrel{\&RightArrow;}{r},t_1)\mathrm{\&Psi;}(\stackrel{\&RightArrow;}{r},t_2)d\stackrel{\&RightArrow;}{r}$

If observed object the backscattering coefficient at place is the scatter echo of observed object scattered information that what receiver received be coupled with can be expressed as follows:

$\mathrm{rec}({\stackrel{\&RightArrow;}{r}}^R,t)=\underset{S}{\&Integral;}\frac{\mathrm{\&Psi;}(\stackrel{\&RightArrow;}{r},t-\frac{|{\stackrel{\&RightArrow;}{r}}^R-\stackrel{\&RightArrow;}{r}|}{c})}{4\mathrm{\&pi;}|{\stackrel{\&RightArrow;}{r}}^R-\stackrel{\&RightArrow;}{r}|}\&CenterDot;\mathrm{\&sigma;}\left(\stackrel{\&RightArrow;}{r}\right)\mathrm{dS}$

Wherein, for the position of receiving element antenna phase center, for observed object the backscattering coefficient at place, c is the light velocity, c=3 × 10 ⁸m/ second, S is the area of target area, is determined by transmitted antednna beam institute coverage.

It is visible, all be coupling in the scatter echo signal received.

Receiver obtains the data of not scattered field echoed signal in the same time in the mode that A/D samples, and radiation field calculation subelement obtains correspondence not space-time bidimensional random radiation field in the same time by the synchronous mode calculated.

It will be understood by those skilled in the art that microwave stares relevance imaging is exactly the information extracting target based on known random radiation field from reception echo, obtains the inverting value of target scattering coefficient the corresponding inverse Problem of elect magnetic field, association process method can be expressed as:

formula 3

Wherein, for the operator of relevance imaging algorithm, namely different relevance imaging algorithms is presented as different operators .Relevance imaging algorithm, (BP) algorithm, orthogonal matching pursuit (OMP) algorithm, management loading (SBL) etc. are followed the trail of in the such as directly association of single order field intensity or the association of high-order field intensity, optimization algorithm such as the base met under target sparse condition.

It will be understood by those skilled in the art that association process obtains the inverting value of target scattering coefficient process, therefore not to repeat here.

Comprehensive foregoing description, the embodiment of the present invention stares relevance imaging device based on the microwave of different code speed random frequency hopping, under lower transmitter code speed, achieves microwave stare needed for relevance imaging, ideal space-time bidimensional random radiation field from engineering.

Receiver can adopt low speed ADC Sampling techniques, still obtains effective target scattering echo samples, reduces the redundancy between sample.

Compared with traditional same code speed random frequency hopping relevance imaging radar array, the target imaging effect obtained is better, and resolution is higher, and imaging radar equipment cost reduces.

The embodiment of the present invention stares relevance imaging device, target observation scene graph, antenna platform height z based on the microwave of different code speed random frequency hopping as shown in Figure 4 ₀=120m, θ=45 °, angle of squint, the size of target area (imaging region) is 24m × 24m, lattice point number 80 × 80, and size is 0.3m × 0.3m, and its backscattering coefficient distribution situation as shown in Figure 5.

Consider in target area very close to two position Ο _p=(x _p, y _p, 0), Ο _q=(x _q, y _q, 0), as shown in two black circles in Fig. 4, can think that each radiating element is very little to the time-delay deviation of these two positions, that is:

$\max \left\{\frac{|d({{\stackrel{\&RightArrow;}{r}}_i}^T,O_p)-d({{\stackrel{\&RightArrow;}{r}}_i}^T,O_q)|}{c}\right\}<<T_d(i=\mathrm{1,2},...N)$

Wherein, the Euclidean distance between d () expression 2.

When each radiating element launches the random frequency hopping pulse signal of same code speed, subpulse hop period is T _d, without loss of generality, if scatter echo signal sampling period T _s=T _d; Due to O _p, O _qthe time delay of two radiation field space, scattering point places is different, then same sampling instant O _p, O _qtwo scattering point place radiation fields correspondences respectively transmit not value superposition in the same time, and corresponding relation is as shown in Fig. 6 (a); Due to Ο _p, Ο _qdistance is enough little, then each array element is to Ο _p, Ο _qselecting time all drop on a hop period T _din, cause Ο _p, Ο _q2 under the effect of this jump frequency coding signal, the quantized value of its radiation field is all identical, and the radiation field distribution of 2 is almost consistent, therefore cannot differentiate.As shown in Fig. 6 (b), when each radiating element launches different code speed random frequency hopping signal, each radiating element subpulse hop period T _dinot identical, then Ο during sampling _p, Ο _qthe value moment then likely falls into different hop periods, directly causes Ο _p, Ο _qthe radiation field distribution of 2 creates difference, and this is Ο _p, Ο _qthe resolution of 2 provides possibility, and therefore, the microwave radiation field that the radar array based on different code speed random frequency hopping is formed possesses better space-time random character, the super-resolution imaging of realize target.

In order to illustrate that the microwave that the present invention is based on different code speed random frequency hopping stares the validity of relevance imaging radar array, below relate to three kinds of signal forms in emulation:

Signal 1: each radiating element launches same code speed random frequency hopping signal, signal carrier frequency f ₀=10G, signal bandwidth is 1GHz, recurrence interval T _t=2.4 μ s, dutycycle is 10%, subpulse hop period T _d=40ns, ensures the orthogonality of all radiating element random frequency hopping patterns.This signal form as reference, in order to the superiority that the present invention designs is described.

Signal 2: the embodiment of the present invention stares in relevance imaging device based on the microwave of different code speed random frequency hopping the form that transmits, namely each radiating element launches different code speed random frequency hopping signal, signal carrier frequency f ₀=10G, signal bandwidth is 1GHz, recurrence interval T _t=2.4 μ s, dutycycle is 10%, subpulse hop period T _diat (1-15%) T _d~ (1+15%) T _dselect in (i.e. 34ns ~ 46ns) scope, preferred a kind of relatively prime code speed, ensures the orthogonality of all radiating element random frequency hopping patterns.

Signal 3:10 speed same code speed random frequency hopping signal, signal carrier frequency f ₀=10G, signal bandwidth is 1GHz, recurrence interval T _t=2.4 μ s, work than being 10%, subpulse hop period ensure the orthogonality of all radiating element random frequency hopping patterns.

When each radiating element transmit 2 time, object space neither in the same time the normalized microwave field distribution of t1, t2 respectively as shown in Fig. 7 (a) He Fig. 7 (b), obviously, not only the microwave field distribution of synchronization observed object diverse location possesses good space random character, and objective plane microwave field distribution does not in the same time possess good time random character, when meeting, the characteristic of empty bidimensional random radiation field, describe the validity of signal 2.

When each radiating element transmits 1 and signal form 2 respectively, scatter echo sampling period T _s=T _d=40ns, sampling number all gets 6400, then obtain the temporal and spatial correlations characteristic of microwave random radiation field in target observation region respectively as Fig. 8 (a) and 9(a) shown in; The random radiation field sample in the corresponding moment utilizing 6400 scatter echo data and radiation field algorithm module to obtain carries out above-mentioned relevance imaging process, obtains object inversion imaging results respectively as Fig. 8 (b) and 9(b) shown in.Obviously, comparison diagram 8 and Fig. 9, can find: during the form 2 that transmits, the correlation peak of its random radiation field correlation properties is more sharp-pointed, and peak value peripheral region is also more smooth, illustrate that the random radiation field otherness of any two points in target area is larger, cross correlation is less, and in imaging, the resolution characteristic of 2 is stronger, thus, inverting image ratio Fig. 8 (b) in Fig. 9 (b) is more clear, and contrast is stronger.

When each radiating element launches the signal form 3 of 10 speed same code speed random frequency hopping signals, scatter echo is sampled as 10 speed samplings, and the cycle gets obtain 64000 sampled datas; Figure 10 sets forth the time correlation linearity curve in the signal 3 of transmitting 10 times of code speed and 2 situations that transmit between each sampling instant random radiation field and center sampling moment radiation field, can find out, both correlativitys are substantially approximate, but in Figure 10 (b) circle, relevance values is higher, illustrates in the scatter echo data that transmitted at high speed, two-forty are sampled to there is larger redundancy.Through being optimized the sampled data of above-mentioned bulk redundancy, correlativity choosing choosing after, pick out 6400 echo samples, the corresponding moment random radiation field correlation properties obtained and association process inversion chart picture thereof are as shown in figure 11.Visible, compared with 2 situations that transmit, it is sharp-pointed that its random radiation field correlation properties almost have peak value equally, and the character that peripheral region is smooth, also closely, equally comparatively Fig. 8 (b) is clear for inversion imaging result.

Visible, the microwave that the present invention is based on different code speed random frequency hopping stares relevance imaging radar array under the condition of low speed transmitting, low speed collection, same radiation field random character preferably under can obtaining 10 times of code speed, transmitted at high speed, high speed acquisition condition, inverting high-resolution imaging, is lowered into picture system cost and complexity.

The above; be only the present invention's preferably embodiment, but protection scope of the present invention is not limited thereto, is anyly familiar with those skilled in the art in the technical scope that the present invention discloses; the change that can expect easily or replacement, all should be encompassed within protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection domain of claims.

Claims (9)

1. the microwave based on different code speed random frequency hopping stares a relevance imaging device, it is characterized in that, comprises random radiation unit, Master Control Unit, receiving element, relevance imaging unit:

The control information that described random radiation unit sends according to described Master Control Unit generates microwave pulse signal and launches, described microwave pulse signal when target area is formed, the radiation field of empty bidimensional random character, in target area, the scatter echo of observed object is received by described receiving element, described scatter echo and described radiation field are carried out association process by described relevance imaging unit, obtain the inversion chart picture of observed object;

Wherein, the recurrence interval of the described microwave pulse signal that each radiating antenna is launched is identical with pulse repetition rate, described microwave pulse signal comprises multiple random frequency hopping subpulse, the frequency of described random frequency hopping subpulse is Stochastic choice in bandwidth range, and the random frequency hopping subpulse code speed of the described microwave pulse signal that different radiating antenna is launched is different and frequency hopping pattern is orthogonal;

The random frequency hopping subpulse that described i-th random radiation unit is launched is expressed as:

$f({{\stackrel{\&RightArrow;}{r}}_i}^T,t)=\underset{m=1}{\overset{M}{\&Sigma;}}\underset{k=1}{\overset{K}{\&Sigma;}}rect\left(\frac{t-{\mathrm{mT}}_t-\frac{2k+1}{2}{T}_{di}}{T_{di}}\right)\exp \{j2{\mathrm{\&pi;f}}_{i,mk}(t-{\mathrm{mT}}_t-{\mathrm{kT}}_{di})+{\mathrm{j\&theta;}}_{i,mk}\}$

Wherein, i=0,1 ..., N-1, N are random radiation element number, be the position of the radiating antenna phase center of i-th random radiation unit, complete recurrence interval is T _t, M recurrence interval, have K random frequency hopping subpulse in a pulse, T _direpresent the subpulse hop period of i-th random radiation unit, f _{i, mk}be the frequency of i-th random radiation unit kth subpulse Frequency Hopping Signal within m recurrence interval, θ _{i, mk}for its first phase, t is the relevance imaging time.

2. the microwave based on different code speed random frequency hopping according to claim 1 stares relevance imaging device, it is characterized in that, the random frequency hopping subpulse code speed sizes values prime number each other of the described microwave pulse signal that different radiating antenna is launched.

3. the microwave based on different code speed random frequency hopping according to claim 1 stares relevance imaging device, it is characterized in that, in target area place time, empty bidimensional random radiation field is expressed as:

$\begin{array}{c}\mathrm{\&Psi;}(\stackrel{\&RightArrow;}{r},t)=\underset{i=1}{\overset{N}{\&Sigma;}}\underset{t^{\&prime;}}{\&Integral;}G({{\stackrel{\&RightArrow;}{r}}_i}^T,t^{\&prime;},\stackrel{\&RightArrow;}{r},t)f({{\stackrel{\&RightArrow;}{r}}_i}^T,t^{\&prime;}){\mathrm{dt}}^{\&prime;}\\ =\underset{i=1}{\overset{N}{\&Sigma;}}\frac{1}{4\mathrm{\&pi;}|\stackrel{\&RightArrow;}{r}-{{\stackrel{\&RightArrow;}{r}}_i}^T|}\underset{m=1}{\overset{M}{\&Sigma;}}\underset{k=1}{\overset{K}{\&Sigma;}}\left\{\begin{array}{c}rect\left(\frac{t-\frac{|\stackrel{\&RightArrow;}{r}-{{\stackrel{\&RightArrow;}{r}}_i}^T|}{c}-{\mathrm{mT}}_t-\frac{2k+1}{2}{T}_{di}}{T_{di}}\right)*\\ \exp \{j2{\mathrm{\&pi;f}}_{i,mk}(t-\frac{|\stackrel{\&RightArrow;}{r}-{{\stackrel{\&RightArrow;}{r}}_i}^T|}{c}-{\mathrm{mT}}_t-{\mathrm{kT}}_{di})+{\mathrm{j\&theta;}}_{i,mk}\}\end{array}\right\}\end{array}$

Wherein, be the transient free-surface Green function of free space electromagnetic fiele, t is the relevance imaging time, and t ' is the x time of random frequency hopping radiofrequency signal, and c is the light velocity;

Synchronization t, in target area have the irrelevant feature in space between the random radiation field at place, its uncorrelated nature is expressed as:

$I({\stackrel{\&RightArrow;}{r}}_1,{\stackrel{\&RightArrow;}{r}}_2,t)=<{\mathrm{\&Psi;}}^{*}({\stackrel{\&RightArrow;}{r}}_1,t)\mathrm{\&Psi;}({\stackrel{\&RightArrow;}{r}}_2,t)>;$

Not t in the same time ₁, t ₂, in the S objective plane of target area have time irrelevant feature between the random radiation field at place, its uncorrelated nature is expressed as:

$I(t_1,t_2)=\underset{S}{\&Integral;}{\mathrm{\&Psi;}}^{*}(\stackrel{\&RightArrow;}{r},t_1)\mathrm{\&Psi;}(\stackrel{\&RightArrow;}{r},t_2)d\stackrel{\&RightArrow;}{r}.$

4. the microwave based on different code speed random frequency hopping according to claim 3 stares relevance imaging device, it is characterized in that, the scatter echo of observed object scattered information that what described receiving element received be coupled with is expressed as:

$rec({\stackrel{\&RightArrow;}{r}}^R,t)=\underset{S}{\&Integral;}\frac{\mathrm{\&Psi;}(\stackrel{\&RightArrow;}{r},t-\frac{|{\stackrel{\&RightArrow;}{r}}^R-\stackrel{\&RightArrow;}{r}|}{c})}{4\mathrm{\&pi;}|{\stackrel{\&RightArrow;}{r}}^R-\stackrel{\&RightArrow;}{r}|}\&CenterDot;\mathrm{\&sigma;}\left(\stackrel{\&RightArrow;}{r}\right)dS$

Wherein, for the position of receiving element antenna phase center, for observed object the backscattering coefficient at place, c is the light velocity, and S is the area of target area.

5. microwave according to claim 4 stares relevance imaging device, it is characterized in that, the relevance imaging algorithmic notation that described scatter echo and described radiation field carry out association process is by described relevance imaging unit:

Wherein, for the operator of relevance imaging algorithm, relevance imaging algorithm comprises: directly single order field intensity association, the association of high-order field intensity, base tracing algorithm, orthogonal matching pursuit algorithm or management loading.

6. stare relevance imaging device according to the described microwave based on different code speed random frequency hopping arbitrary in claim 1-5, it is characterized in that, described Master Control Unit comprises PLL local oscillator, system clock, random frequency hopping selection and code speed control subunit and random signal controls and sequential control subelement:

Described PLL local oscillator, for providing the stable reference local oscillator carrier wave needed for described random radiation unit up-conversion and described receiving element down coversion;

Described system clock, for for described Master Control Unit, random radiation unit and receiving element providing source are from the high-frequency stable reference clock signal of same constant-temperature crystal oscillator;

Described random frequency hopping is selected and code speed control subunit, for generation of the direct digital frequency synthesier DDS baseband signal control word controlling frequency hopping pattern and hop period;

Described random signal controls and sequential control subelement, for generation of steering order and the synchronous triggering signal of local oscillator carrier wave, random frequency hopping subpulse baseband signal waveform.

7. the microwave based on different code speed random frequency hopping according to claim 6 stares relevance imaging device, it is characterized in that, described random radiation unit comprises DDS subelement, frequency mixer subelement, bandpass filter subelement, radio-frequency (RF) power amplification subelement and radiating antenna:

Described DDS subelement, for under the control of the synchronous triggering signal that described random signal controls and sequential control subelement sends, utilize from the DDS baseband signal control word that described random frequency hopping is selected and code speed control subunit receives, synthesize and export the baseband waveform signal of random frequency hopping subpulse to described frequency mixer subelement;

Described frequency mixer subelement, for realizing up-conversion modulation, makes the base-band signal spectrum of input random frequency hopping subpulse move in the frequency range of local oscillator carrier wave, and exports random frequency hopping radiofrequency signal to described bandpass filter subelement;

Described bandpass filter subelement, for carrying out filtering for random frequency hopping radiofrequency signal;

Described radio-frequency (RF) power amplification subelement, for carrying out power amplification for random frequency hopping radiofrequency signal, and is launched by radiating antenna.

8. the microwave based on different code speed random frequency hopping according to claim 7 stares relevance imaging device, and it is characterized in that, described radiating antenna forms intensive or sparse antenna array, and described aerial array is evenly arrangement or non-homogeneous arrangement.

9. microwave according to claim 8 stares relevance imaging device, it is characterized in that, described receiving element comprises receiving antenna, radio frequency subelement and echo acquirement subelement:

Receiving antenna, for receiving scatter echo;

Radio frequency subelement, for amplifying and filtering the described scatter echo received;

Echo acquirement subelement, for sampling to amplification and filtered described scatter echo;

Relevance imaging unit comprises echo data and optimizes subelement, radiation field calculation subelement, association process subelement and inversion chart picture display subelement:

Echo data optimizes subelement, for carrying out de-redundancy and optimum choice to the described scatter echo data after sampling;

Radiation field calculation subelement, for calculating the radiation field of target area;

Association process subelement, for carrying out association process to the radiation field of the described scatter echo after optimization and the calculation of radiation field calculation subelement;

Inversion chart picture display subelement, exports for the reconstruct of realize target image and the image of inverting.