CN103744078A - Microwave stare correlated imaging device capable of performing random frequency hopping based on different code speeds - Google Patents

Abstract

The invention discloses a microwave stare correlated imaging device capable of performing random frequency hopping based on different code speeds. A random radiation unit is used for generating and transmitting a microwave pulse signal according to control information transmitted by a main control unit, the microwave pulse signal forms a microwave radiation field having time-space two-dimensional random features in a target area, the scatter echo of an observation target in the target area is received by a receiving unit, and a correlated imaging device is used for correlating the scatter echo with a microwave radiation field to obtain an inversion image observation target; the microwave pulse signal transmitted by each radiation antenna is the same in the pulse period and the pulse repeating frequency, each microwave pulse signal comprises a plurality of random frequency hopping sub-pulses, a frequency point is selected randomly in a bandwidth range, microwave pulse signals transmitted by different radiation antennas are different in random frequency hopping sub-pulse frequency hopping code speed, and frequency hopping patterns are orthogonal. An ideal time-space two-dimensional random radiation field which is required by microwave stare correlated imaging is realized on the aspect of engineering under the conditions of low code speed transmission, low-speed acquisition and lower bandwidth.

Description

A kind of microwave based on the fast random frequency hopping of different code is stared relevance imaging device

Technical field

The present invention relates to radar imagery technical field, relate in particular to a kind of microwave based on the fast random frequency hopping of different code and stare relevance imaging device.

Background technology

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

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

The random character factor that affects the random radiation field of space-time bidimensional mainly comprises the form of radar array transponder pulse signal, bandwidth, code speed, and the far field amplitude-phase distribution of the spatial arrangement of emission array and the emitting antenna under different frequency etc.How under the engineering specifications of limited radar array scale, limited signal bandwidth, lower code speed, construct random radiation relevance imaging radar array when good to realize, the random radiation field of empty bidimensional 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 the fast random frequency hoppings of different code and stares relevance imaging device, realizes when good, the random radiation field of empty bidimensional.

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

Microwave based on the fast random frequency hopping of different code is stared a relevance imaging device, comprises random radiating element, Master Control Unit, receiving element, relevance imaging unit:

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

Wherein, the recurrence interval of the described microwave pulse signal of each radiating antenna transmitting is identical with pulse repetition rate, described microwave pulse signal comprises a plurality of random frequency hopping subpulses, the frequency of described random frequency hopping subpulse is random selection in bandwidth range, random frequency hopping subpulse code speed difference and the frequency hopping pattern quadrature of the described microwave pulse signal of different radiating antenna transmittings.

The technical scheme being provided by the invention described above embodiment can be found out, microwave based on the fast random frequency hopping of different code is stared relevance imaging device, under limited signal bandwidth and lower random frequency hopping code speed condition, in target area, formed when better, the radiation field of empty bidimensional random character, overcome existing random frequency hopping radar array and produce the undesirable shortcoming of radiation field randomness, improved microwave radiation field time, empty bidimensional random character, reduced the redundancy of scatter echo sample, be beneficial to realize microwave and stare relevance imaging, acquisition surmounts the high-resolution of 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 of required use during embodiment is described 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, do not paying under the prerequisite of creative work, can also obtain other accompanying drawings according to these accompanying drawings.

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

The microwave that Fig. 2 is the embodiment of the present invention based on the fast random frequency hoppings of different code is stared relevance imaging device and is specifically formed schematic diagram.

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

The microwave that Fig. 4 is the embodiment of the present invention based on the fast random frequency hoppings of different code is stared relevance imaging device microwave and is stared relevance imaging observation scene configuration schematic diagram.

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

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

The microwave that Fig. 7 is the embodiment of the present invention based on the fast random frequency hoppings of different code stare relevance imaging device at the subcode hop period of the fast random frequency hopping signals of different code within the scope of 34ns～46ns in random selection situation, at observed object t1 and the t2 random radiation field distribution figure schematic diagram of normalized microwave constantly.

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

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

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

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

Embodiment

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

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

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

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

Wherein, the recurrence interval of the described microwave pulse signal of each radiating antenna transmitting is identical with pulse repetition rate, described microwave pulse signal comprises a plurality of random frequency hopping subpulses, the frequency of described random frequency hopping subpulse is random selection in bandwidth range, random frequency hopping subpulse code speed difference and the frequency hopping pattern quadrature of the described microwave pulse signal of different radiating antenna transmittings.

The technical scheme being provided by the invention described above embodiment can find out, the hop period of the random frequency hopping subpulse of the described microwave pulse signal of different radiating antennas transmittings is different, and subpulse frequency hopping code speed is different.The radiation field that described microwave pulse signal encourages by aerial array is in the irrelevant stack in target observation space, formed when better, the radiation field of empty bidimensional random character in target area.

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

Visible, the microwave of the embodiment of the present invention based on the fast random frequency hopping of different code stared relevance imaging device, realization is under Finite Array scale and limited signal bandwidth and lower random frequency hopping code speed condition, by launching the fast random frequency hopping pulse signal of different code, in target area, formed when better, the radiation field of empty bidimensional random character, overcome existing random frequency hopping radar array and produce the undesirable shortcoming of radiation field randomness, improved radiation field time, empty bidimensional random character.Receiver can adopt low speed ADC(Analog to Digital Converter, A-D converter) sampling, still obtain effective target scattering echo samples, reduced the redundancy of scatter echo sample.The target imaging effect obtaining is better, and resolution is higher, obtains the high-resolution that surmounts antenna aperture restriction.

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

The microwave of the embodiment of the present invention based on the fast random frequency hopping of different code stared relevance imaging device, can in bandwidth range, select at random the frequency of random frequency hopping subpulse, and bandwidth is generally less than 1GHz, but not strictly restriction.

The microwave of the embodiment of the present invention based on the fast random frequency hopping of different code stared in relevance imaging device, the fast selection mode of different code as a kind of random frequency hopping subpulse, between random radiating element, the fast difference of code can be selected at random in certain limit mutually, as selected the random frequency hopping subpulse code speed sizes values prime number (the fast scheme of relatively prime code) each other of the microwave pulse signal of different radiating antennas transmittings.

Exemplary, the fast scheme of relatively prime code, 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 the fast random frequency hopping of different code is stared relevance imaging device, comprises random radiating element 1, Master Control Unit 2, receiver 3, relevance imaging unit 4.Random radiating element can be for a plurality of, and number is N.

Particularly, Master Control Unit 2 can comprise that PLL (Phase Locked Loop, phaselocked loop) local oscillator 21, system clock 22, random frequency hopping are selected and code speed control system unit 23 and random signal control and sequential control subelement 24:

PLL local oscillator 21, for providing described random radiating element up-conversion and described receiving element down coversion required stable reference local oscillator carrier wave.

System clock 22, is used to described Master Control Unit, random radiating element and receiver 3 that the high-frequency stable reference clock signal that is derived from same constant-temperature crystal oscillator is provided.

Random frequency hopping is selected and code speed control system unit 23, for generation of DDS (Direct Digital Synthesizer, Direct Digital frequency synthesis) the baseband signal control word of controlling frequency hopping pattern and hop period.Corresponding, be appreciated that it can be baseband signal control word that Master Control Unit 2 sends to the control information of random radiating element 1.

Random signal is controlled 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, particularly, random radiating element 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, under control for the synchronous triggering signal in described random signal control and the transmission of sequential control subelement, utilization is from the DDS baseband signal control word that described random frequency hopping is selected and code speed control system unit receives, synthesize and the baseband waveform signal of exporting random frequency hopping subpulse to described frequency mixer subelement;

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

Bandpass filter subelement 13, is used to random frequency hopping radiofrequency signal to carry out filtering;

Radio-frequency (RF) power amplification subelement 14, carries out power amplification for random frequency hopping radiofrequency signal, and launches 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 receiving, 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, and the fast random frequency hopping base-band signal spectrum of different code of input is moved in the frequency range of local oscillator carrier wave; Bandpass filter subelement is used to the random frequency hopping radiofrequency signal of each random radiating element transmitting to carry out filtering, and the noise that filtering is unnecessary, improves signal to noise ratio (S/N ratio); Radio-frequency (RF) power amplification subelement, for the random frequency hopping pulse signal of different code speed is carried out to power amplification, makes it to meet the radiation power requirement of relevance imaging system, keeps the shape of microwave pulse signal simultaneously.

A plurality of radiating antennas form aerial array, aerial array can adopt intensive or sparse antenna array, aerial array configuration can be fixedly static state or random variation dynamic, can be evenly to arrange or non-homogeneous arranging, for under the excitation of described random frequency hopping microwave pulse signal, while forming in target area, the random radiation field of empty bidimensional.

Still, with reference to shown in figure 2, particularly, 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 receiving;

Echo acquirement subelement 33, for sampling to amplifying with filtered described scatter echo;

Embodiment of the present invention microwave is stared 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., for realizing, receives the amplification of scatter echo signal and the function of filtering, guarantees that receiver has sufficiently high gain and signal to noise ratio (S/N ratio).Echo acquirement subelement 33 can comprise that intermediate frequency amplifies, AD sampling module, for completing functions such as receiving the sampling of scatter echo signal and storage.And then the high-performance that receiving element is realized observed object scatter echo signal receives and sampling functions.

Still, with reference to shown in figure 2, particularly, relevance imaging unit can comprise that echo data is optimized subelement 41, radiation field is calculated subelement 42, association process subelement 43 and inversion chart picture and shown subelement 44:

Echo data is optimized subelement 41, for the described scatter echo data after sampling being carried out to de-redundancy and optimizing and select;

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 of the described scatter echo to after optimizing and 42 calculations of radiation field calculation subelement;

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

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

Radiation field calculation subelement can be stared the parameters such as relevance imaging apparatus system parameter, the fast random frequency hopping signal parameter of different code and aerial array configuration according to microwave, complete the calculation of observed object radiation field, specifically referring to hereinafter formula 2 descriptions.

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

Relevance imaging algorithm, associated such as the directly association of single order field intensity or high-order field intensity, meet optimization algorithm under the sparse condition of target and follow the trail of (BP), orthogonal matching pursuit (OMP), sparse Bayesian study (SBL) etc. as base.

Below in conjunction with formula, to the embodiment of the present invention, the microwave based on the fast random frequency hoppings of different code is stared relevance imaging device and is described, and as shown in Figure 3, transmitter 1 is launched respectively the microwave pulse signal of the fast random frequency hoppings of different code to transmitter N.I the random frequency hopping subpulse that radiating element is launched is at random expressed as:

$f({{\stackrel{\&RightArrow;}{r}}_i}^T,t)=\underset{m=1}{\overset{M}{\mathrm{\&Sigma;}}}\underset{k=1}{\overset{K}{\mathrm{\&Sigma;}}}\mathrm{rect}\left(\frac{t-{\mathrm{mT}}_t-\frac{2k+1}{2}{T}_{\mathrm{di}}}{T_{\mathrm{di}}}\right)\exp \{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA0000449919390000011.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}{f}_{i,\mathrm{mk}}(t-{\mathrm{mT}}_t-{\mathrm{kT}}_{\mathrm{di}})+{\mathrm{j\&theta;}}_{i,\mathrm{mk}}\}$ Formula 1

Wherein, i=0,1 ..., N-1, N is random radiating element quantity,

be the position of the radiating antenna phase center of i random radiating element, a complete recurrence interval is T _t, M recurrence interval, in the recurrence interval, have K random frequency hopping subpulse, T _dithe subpulse hop period that represents i random radiating element, f _{i, mk}be the frequency of i random radiating element k subpulse Frequency Hopping Signal within m recurrence interval, θ _{i, mk}for its first phase, t is the relevance imaging time, requires to guarantee that between all random radiating elements, subpulse frequency hopping pattern is mutually orthogonal here.

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

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

$\begin{array}{c}\mathrm{\&Psi;}(\stackrel{\&RightArrow;}{r},t)=\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}\underset{t^{\&prime;}}{\&Integral;}G({{\stackrel{\&RightArrow;}{r}}_i}^T,t^{\&prime;},\stackrel{\&RightArrow;}{r},t)f({{\stackrel{\&RightArrow;}{r}}_i}^T,t^{\&prime;}){\mathrm{dt}}^{\&prime;}\\ =\underset{i=1}{\overset{\mathrm{<figure-callout\; id="1"\; label="N"\; filenames="HDA0000449919390000011.png,HDA0000449919390000042.png"\; state="\{\{state\}\}">N</figure-callout>}}{\mathrm{\&Sigma;}}}\frac{1}{4\mathrm{\&pi;}|\stackrel{\&RightArrow;}{r}-{{\stackrel{\&RightArrow;}{r}}_i}^T|}\underset{m=1}{\overset{M}{\mathrm{\&Sigma;}}}\underset{k=1}{\overset{K}{\mathrm{\&Sigma;}}}\left\{\begin{array}{c}\mathrm{rect}\left(\frac{t-\frac{|\stackrel{\&RightArrow;}{r}-{{\stackrel{\&RightArrow;}{r}}_i}^T|}{c}-{\mathrm{nT}}_t-\frac{2k+1}{2}{T}_{\mathrm{di}}}{T_{\mathrm{di}}}\right)*\\ \exp \{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA0000449919390000011.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}{f}_{i,\mathrm{mk}}(t-\frac{|\stackrel{\&RightArrow;}{r}-{{\stackrel{\&RightArrow;}{r}}_i}^T|}{c}-{\mathrm{mT}}_t-{\mathrm{kT}}_{\mathrm{di}})+{\mathrm{j\&theta;}}_{i,\mathrm{mk}}\}\end{array}\right.\end{array}$ Formula 2

Wherein,

the time domain Green function of Electromagnetic Field while being free space, i the random frequency hopping subpulse that random radiating element is launched

, there be K random frequency hopping subpulse M recurrence interval 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.

T in the same time not ₁, t ₂, in the S objective plane of target area

between the random radiation field at place, have irrelevant feature of time, its uncorrelated nature is expressed as:

$I({\mathrm{<figure-callout\; id="1"\; label="t"\; filenames="HDA0000449919390000011.png,HDA0000449919390000042.png"\; state="\{\{state\}\}">t</figure-callout>}}_1,t_2)=\underset{S}{\text{\&Integral;}}{\mathrm{\&Psi;}}^{*}(\stackrel{\&RightArrow;}{r},t_1)\mathrm{\&Psi;}(\stackrel{\&RightArrow;}{r},t_2)d\stackrel{\&RightArrow;}{r}$

If observed object

the backscattering coefficient at place is

the scatter echo that is coupled with observed object scattered information that receiver receives 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, the area that S is target area, is determined by transmitted antednna beam institute coverage.

It is visible,

all be coupling in the scatter echo signal receiving.

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

It will be understood by those skilled in the art that it is exactly that random radiation field based on known is extracted the information of target from receive echo that microwave is stared relevance imaging, 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, different relevance imaging algorithms are presented as different operators

.Relevance imaging algorithm, associated such as the directly association of single order field intensity or high-order field intensity, meet optimization algorithm under the sparse condition of target and follow the trail of (BP) algorithm, orthogonal matching pursuit (OMP) algorithm, sparse Bayesian study (SBL) etc. as base.

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 microwave of the embodiment of the present invention based on the fast random frequency hopping of different code stared relevance imaging device, under lower transmitter code speed, realized microwave stare the random radiation field of required, the comparatively desirable space-time bidimensional of relevance imaging from engineering.

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

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

The microwave of the embodiment of the present invention based on the fast random frequency hopping of different code stared relevance imaging device, target observation scene graph, antenna platform height z 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, size is 0.3m * 0.3m, its backscattering coefficient distribution situation is 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 of d () between representing at 2.

When the random frequency hopping pulse signal of each radiating element transmitting same code speed, subpulse hop period is T _d, without loss of generality, establish 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, same sampling instant O _p, O _qthe value stack in the same time that respectively transmits not of two scattering point place radiation field correspondences, corresponding relation is as shown in Fig. 6 (a); Due to Ο _p, Ο _qdistance is enough little, and 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 frequency hopping pulse 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 the fast random frequency hopping signal of each different code of radiating element transmitting, each radiating element subpulse hop period T _dinot identical, Ο while sampling _p, Ο _qvalue constantly likely falls into different hop periods, directly causes Ο _p, Ο _qthe radiation field distribution of 2 has produced difference, and this is Ο _p, Ο _qthe resolution of 2 provides possibility, and therefore, the formed microwave radiation field of radar array based on the fast random frequency hoppings of different code possesses better space-time random character, the super-resolution imaging of realize target.

In order illustrating, to the present invention is based on the validity that the microwave of the fast random frequency hoppings of different code is stared relevance imaging radar array, in following emulation, to relate to three kinds of signal forms:

Signal 1: each radiating element transmitting 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, guarantees the orthogonality of all radiating element random frequency hopping patterns.Sort signal form is as reference, for the superiority that illustrates that the present invention designs.

Signal 2: the microwave of the embodiment of the present invention based on the fast random frequency hoppings of different code stared the form that transmits in relevance imaging device, i.e. fast random frequency hopping signals of each different code of radiating element transmitting, 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 _din (being 34ns～46ns) scope, select, preferably a kind of relatively prime code is fast, guarantees 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 is than being 10%, subpulse hop period guarantee the orthogonality of all radiating element random frequency hopping patterns.

When each radiating element transmits 2 time, object space neither in the same time the normalized microwave field distribution of t1, t2 respectively as shown in Fig. 7 (a) and 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, while meeting, the characteristic of the random radiation field of empty bidimensional, the validity of signal 2 has been described.

When each radiating element transmits respectively 1 and during signal form 2, scatter echo sampling period T _s=T _d=40ns, sampling number all gets 6400, obtains respectively the temporal and spatial correlations characteristic of the random radiation field of microwave in target observation region as Fig. 8 (a) with 9(a); Utilize the corresponding random radiation field sample constantly that 6400 scatter echo data and radiation field calculation module obtains to carry out above-mentioned relevance imaging processing, obtain respectively object inversion imaging results as Fig. 8 (b) and 9(b).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 in target area, the random radiation field otherness of any two points is larger, cross correlation is less, and in imaging, the resolution characteristic of 2 is stronger, thereby, inverting image ratio Fig. 8 (b) in Fig. 9 (b) is more clear, and contrast is stronger.

When each radiating element is launched 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 has provided respectively and has launched in the signal 3 of 10 times of code speed and 2 situations that transmit the random radiation field of each sampling instant and the center sampling time correlation linearity curve between radiation field constantly, can find out, both correlativitys are substantially approximate, but relevance values is higher in Figure 10 (b) circle, the larger redundancy of existence in the scatter echo data of transmitted at high speed, two-forty sampling be described.Through the sampled data to above-mentioned bulk redundancy, be optimized, after correlativity choosing choosing, pick out 6400 echo samples, the corresponding constantly random radiation field correlation properties that obtain and association process inversion chart picture thereof are as shown in figure 11.Visible, to compare with 2 situations that transmit, it is sharp-pointed that its random radiation field correlation properties almost have peak value equally, the character that peripheral region is smooth, inversion imaging result is also very approaching, clear compared with Fig. 8 (b) equally.

Visible, the microwave that the present invention is based on the fast random frequency hopping of different code is stared relevance imaging radar array under the condition of low speed transmitting, low speed collection, can obtain same radiation field random character preferably under 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 embodiment preferably, but protection scope of the present invention is not limited to this, is anyly familiar with in technical scope that those skilled in the art disclose in the present invention; the variation that can expect easily or replacement, within all should being encompassed in 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 (10)

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

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

Wherein, the recurrence interval of the described microwave pulse signal of each radiating antenna transmitting is identical with pulse repetition rate, described microwave pulse signal comprises a plurality of random frequency hopping subpulses, the frequency of described random frequency hopping subpulse is random selection in bandwidth range, random frequency hopping subpulse code speed difference and the frequency hopping pattern quadrature of the described microwave pulse signal of different radiating antenna transmittings.

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

3. the microwave based on the fast random frequency hopping of different code according to claim 1 is stared relevance imaging device, it is characterized in that, described i the random frequency hopping subpulse that radiating element is launched is at random expressed as:

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

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

4. the microwave based on the fast random frequency hopping of different code according to claim 3 is stared relevance imaging device, it is characterized in that, in target area

place time, the random radiation field of empty bidimensional is expressed as:

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

Wherein,

the time domain Green function of Electromagnetic Field while being free space, 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 between the random radiation field at place, have the irrelevant feature in space, its uncorrelated nature is expressed as:

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

T in the same time not ₁, t ₂, in the S objective plane of target area

between the random radiation field at place, have irrelevant feature of time, its uncorrelated nature is expressed as:

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

5. the microwave based on the fast random frequency hopping of different code according to claim 4 is stared relevance imaging device, it is characterized in that, the scatter echo that is coupled with observed object scattered information that described receiver receives is expressed as:

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

Wherein,

position for receiving element antenna phase center

for observed object

the backscattering coefficient at place, c is the light velocity, the area that S is target area.

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

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 sparse Bayesian study.

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

Described PLL phaselocked loop local oscillator, for providing described random radiating element up-conversion and described receiving element down coversion required stable reference local oscillator carrier wave;

Described system clock, is used to described Master Control Unit, random radiating element and receiver that the high-frequency stable reference clock signal that is derived from same constant-temperature crystal oscillator is provided;

Described random frequency hopping is selected and code speed control system unit, for generation of the Direct Digital frequency synthesis DDS baseband signal control word of controlling frequency hopping pattern and hop period;

Described random signal is controlled 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.

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

Described DDS subelement, under control for the synchronous triggering signal in described random signal control and the transmission of sequential control subelement, utilization is from the DDS baseband signal control word that described random frequency hopping is selected and code speed control system unit receives, synthesize and the baseband waveform signal of exporting random frequency hopping subpulse to described frequency mixer subelement;

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

Described bandpass filter subelement, is used to random frequency hopping radiofrequency signal to carry out filtering;

Described radio-frequency (RF) power amplification subelement, is used to random frequency hopping radiofrequency signal to carry out power amplification, and launches by radiating antenna.

9. the microwave based on the fast random frequency hopping of different code according to claim 8 is stared relevance imaging device, it is characterized in that, described radiating antenna forms intensive or sparse antenna array, and described aerial array is for evenly arranging or non-homogeneous arranging.

10. microwave according to claim 9 is stared 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 receiving;

Echo acquirement subelement, for sampling to amplifying with filtered described scatter echo;

Relevance imaging unit comprises that echo data is optimized subelement, radiation field is calculated subelement, association process subelement and inversion chart picture and shown subelement:

Echo data is optimized subelement, for the described scatter echo data after sampling being carried out to de-redundancy and optimizing and select;

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

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

Inversion chart picture shows subelement, for the reconstruct of realize target image and the output of the image of inverting.

Images