CN103033797B - Metrewave radar self-adaption frequency selection method based on spatial filtering - Google Patents

Abstract

The invention relates to a metrewave radar self-adaption frequency selection method based on spatial filtering. The metrewave radar self-adaption frequency selection method based on the spatial filtering carries out frequency subsection, digital beam formation and time domain fast fourier transform (FFT) algorithm process on metrewave radar according to the character that a metrewave radar similarly has a low-frequency stage, finally creates an optimum working frequency base through frequency spectrum comparison, and selects working frequency according to different requirements of users. The metrewave radar self-adaption frequency selection method based on the spatial filtering adopts a process procedure which is not preset with an optimum working frequency band, carries out demodulator band filter (DBF) spatial filtering process on data of all frequency bands, meanwhile takes the character that resonance scattering of a conventional target occurs in a metrewave frequency band into consideration, about criterions, selection of working frequency is carried out by creating the optimum working frequency base and combining the optimum working frequency base and a resonant frequency data base instead of using a criterion that output average power is minimum, and therefore the best detection performance of the metrewave radar is ensured. The metrewave radar self-adaption frequency selection method based on the spatial filtering is applicable to self-adaption and resisting external disturbance of the metrewave radar under complex electromagnetic environment.

Description

A kind of metre wave radar adaptive frequency selection method based on airspace filter

Technical field

The invention belongs to Radar Technology field, be specifically related to a kind of metre wave radar adaptive frequency selection method based on airspace filter.

Background technology

In radar electronic warfare, frequency domain antagonism is an importance.With regard to radar, except expansion frequency domain and capturing new frequency range, the prompt change technology of many proportions, can be divided into the conversion system of radar three kinds of random frequency conversion, regular frequency conversion (coding etc.) and self-adapting frequency conversions according to the regularity of distribution of Frequency point.

Random conversion system, due to the randomness of frequency transformation, can effectively resist arrowband spot jamming, large but the system of completely random frequency conversion realizes difficulty.Regular frequency conversion more easily realizes by contrast, but antijamming capability is not as random frequency conversion.No matter be random frequency conversion or regular frequency conversion, under the barrage jamming of high-power broadband, just can not effectively improve Studies of Radar Detection performance; And employing self-adapting frequency conversion carries out transmission frequency selection by interference analysis, can improve the detection performance of radar, improve antijamming capability.Document (Huang Hongxu, " radar frequency agility anti-jamming Performance Analysis and evaluation studies ", aerospace electron antagonism) analyze radar conversion system and the impact of frequency conversion speed on interference free performance, and the anti-three kinds of active suppressing interference performances of frequency agility technology are assessed.

Wider frequency conversion scope and higher frequency conversion speed are the jamproof most important condition of frequency agility technology, and radar is the jamproof key of radar self-adaption frequency conversion to the analysis of disturbing and transmission frequency selection technology.Because the power spectrum of undesired signal is generally inhomogeneous (jamming transmitter imperfection, disturb the factors such as the frequency response of emitting antenna is inhomogeneous, the multipath effect of radio wave propagation to cause), therefore, the analysis of disturbing is carried out at frequency spectrum conventionally, the frequency spectrum concave point of jammer or recessed differentiation are separated out, the frequency of operation of control radar is followed the tracks of in this frequency spectrum concave point Huo Ao district, thereby reaches jamproof object.General way is by each optional frequency, the signal receiving stand-down to be carried out to mixing in order, then, and collection analysis difference frequency signal, the interference size on more each frequency, the frequency of selection certain condition (as disturbed minimum).

Document (Tian Jiao, " radar self-adaption frequency control system Interference Detection research and implementation ", computing technique and robotization) according to above-mentioned principle design Interference Detection analysis circuit, and carried out simulating, verifying.But this method, in the situation that wider, the optional frequency of system relative bandwidth is too much, because proportion scanning can take a large amount of time, therefore cannot ensure higher frequency conversion speed, has the problem of Analysis interference real-time simultaneously.

Document (Su Hongtao, " sky-wave OTH radar frequency of operation point adaptively selected ", electronics and information journal) a kind of method that frequency spectrum resource utilization rate can be adaptive should be sky-wave OTH radar and select frequency of operation point that improves proposed, mainly utilize the part array element of receiving array to do broadband reception, then, the method forming with adaptive beam with certain frequency interval is analyzed disturbing, and chooses frequency optimum traffic point taking submatrix output average power minimum as criterion.But it sets in advance best effort frequency range, so just cannot ensure wider frequency conversion scope.

Summary of the invention

The technical matters solving

For fear of the deficiencies in the prior art part, the present invention proposes a kind of metre wave radar adaptive frequency selection method based on airspace filter, low for metre wave radar frequency range, absolute bandwidth is narrow but how feature that relative bandwidth is wider solves metre wave radar by the problem to the analysis select transmit frequency of disturbing.

Technical scheme

A metre wave radar adaptive frequency selection method based on airspace filter, is characterized in that step is as follows:

Step 1 frequency segmentation: stand-down M antenna channels distinguished simultaneously with F at radar _ssampling rate image data, then carries out digital filtering, and will receive division of signal is N frequency band; Described n digital filter transmission band scope is f _n,b～f _n,e, the data of m passage collection are output as after device after filtering

$y_{m,n}\left(l\right)=\underset{l_n=0}{\overset{L_n-1}{\mathrm{\Σ}}}{a}_n\left(l_n\right)x_m(l-l_n)$

Wherein: a _n(l _n) be according to the filter coefficient of free transmission range design, L _nrepresent the exponent number of wave filter;

Step 2 digital beam forms: the output of n digital filter divided and carried out DBF according to spatial domain,

$z_{p,n}\left(l\right)=\underset{m=1}{\overset{M}{\mathrm{\Σ}}}{w}_{m,n}^{*}\left({\mathrm{\θ}}_p\right)y_{m,n}\left(l\right)$

Wherein w _m,n(θ _p), m=1,2 ..., M represents that antenna array is at θ _pin direction, form wave beam f _{n, 0}the corresponding weights of frequency, f _{n, 0}∈ [f _n,b, f _n,e];

Non-self-adapting weights $w_{m,n}\left({\mathrm{\θ}}_p\right)=\exp [-j2\mathrm{\π}(m-1)\frac{d}{c}{f}_{n,0}{\sin \mathrm{\θ}}_p],$ Wherein d is array element distance; C is the light velocity;

Step 3 time domain FFT processes: extract z according to every D point _p,n(l) carry out the FFT that K is ordered

$Z_{p,n}\left(k\right)=\underset{l=0}{\overset{K-1}{\mathrm{\Σ}}}{z}_{p,n}\left(\mathrm{lD}\right)\exp (-j2\mathrm{\π}\frac{\mathrm{kl}}{K})$

Wherein D meets k=0,1 ..., K-1, | Z _p,n(k) | be used for being described in θ _pin direction, interference noise is in frequency $(i+\frac{k}{K})\frac{F_s}{D}\∈[f_{n,b},f_{n,e}]$ Amplitude spectrum, i=i _bor i _e, to round downwards;

Step 4, Frequency spectrum ratio, obtains the frequency of interference noise minimum: the output that FFT is processed compares, and obtains θ _pf in direction _n,e～f _n,bthe frequency of the interference noise minimum in frequency range, is designated as f _n,p;

If k ₀satisfy condition $\underset{k=0,...,K-1}{\min }E\left\{{\left|Z_{p,n}\left(k\right)\right|}^2\right\},$ ? $f_{n,p}=(i_0+\frac{k_0}{K})\frac{F_s}{D},$ Suppose k _b=[DKf _n,b/ F _s]-Ki _b, k _e=[DKf _n,e/ F _s]-Ki _e, [] is rounding of the formula of rounding up; Work as k _e> k ₀> k _btime, i ₀=i _b; Work as k ₀> k _b> k _etime, i ₀=i _b; Work as k ₀< k _e< k _btime, i ₀=i _e.

The frequency f that the Frequency spectrum ratio that step 4 is carried out obtains more afterwards _n,p, according to direction θ _pwith frequency band f _n,b～f _n,eset up frequency optimum traffic storehouse:

Frequency optimum traffic storehouse

Then, according to user's requirement, the position θ different to spatial domain _p, select one or more suitable radar transmitter frequencies.

Beneficial effect

A kind of metre wave radar adaptive frequency selection method based on airspace filter that the present invention proposes, in view of metre wave radar has the feature compared with low-frequency range equally, comprise frequency segmentation, digital beam forms, and time domain FFT processes, finally, by Frequency spectrum ratio, set up frequency optimum traffic storehouse, require to select frequency of operation according to user's difference, the present invention adopts the treatment scheme of not preset best effort frequency range, and the data of all frequency ranges are all carried out to the processing of DBF airspace filter; Consider the characteristic of conventional target at meter wave band Resonance scattering simultaneously, on criterion, do not select frequency of operation taking output average power minimum as criterion, but set up frequency optimum traffic storehouse, carry out frequency selection in conjunction with resonance frequency database, thereby ensure the detection performance of radar the best.The method is applicable to the self-adapting frequency conversion antagonism external disturbance of metre wave radar under complex electromagnetic environment.

The present invention compared with prior art, has the following advantages:

1, because do not need local oscillator frequency conversion, can within the relatively short time, complete interference noise level analysis, therefore, real-time is better, and can allow self-adapting frequency conversion speed faster.

The frequency range of 2, having carried out before wave beam forms is to a certain degree divided, and it is basically identical that the system that ensured receives the directional diagram that the signal of different frequency in bandwidth forms; Compare frequency range and divide carry out again wave beam formation completely, can significantly not increase the complexity of hardware.

3, by setting up frequency optimum traffic storehouse, can provide the selection that frequency diversity radar frequency span is larger, thereby have better antijamming capability.

Because need directly to gather radiofrequency signal, this method is more suitable for the digital radar in low-frequency range.

Brief description of the drawings

Fig. 1 is the process flow diagram of the invention process process

Fig. 2 is the system chart that the present invention realizes

Fig. 3 is the schematic diagram of digital filter of the present invention

Fig. 4 is the schematic diagram of even linear array DBF of the present invention

Fig. 5 is simulation result figure of the present invention.

Embodiment

Now in conjunction with the embodiments, the invention will be further described for accompanying drawing:

Stand-down M antenna channels distinguished simultaneously with F at radar _ssampling rate image data, by digital filter bank, is divided into N section by reception bandwidth; Respectively each digital filter output is carried out to digital beam formation processing, ensure that P the wave beam forming covers whole spatial domain; The FFT processing that K is ordered is done in output after digital beam is formed, by the frequency of frequency spectrum alternative interference noise amplitude minimum; Last according to the orientation of formed wave beam, set up frequency optimum traffic storehouse.System chart as shown in Figure 2, is used x _m(l) (l=0,1,2 ...) represent m(m=1,2 ..., M) and the data of individual antenna channels through gathering after LNA.

With reference to Fig. 1, it is process flow diagram of the invention process.Its specific implementation process is as follows:

First, each antenna channels is sampled through the radar return signal of low noise amplifier; Second step, carries out the narrow bandpass digital filtering of different passbands to sampled signal; The 3rd step, carries out digital beam formation to signal after filtering according to band limits; The 4th step, processes the frequency spectrum that obtains wave beam and form rear signal by FFT; The 4th step, by Frequency spectrum ratio, calculates the frequency of operation of local optimum according to formula 6; The 5th step, sets up frequency optimum traffic storehouse, requires to select radar frequency of operation according to user.

With reference to Fig. 2, it is the system chart that the present invention realizes, and specific practice is as follows:

1), with reference to Fig. 3, it is the schematic diagram of digital filter of the present invention.Realize the frequency segmentation that receives bandwidth by digital filter bank, the exponent number of n digital filter is L _n, the coefficient of wave filter is and 1 to require the free transmission range of wave filter be f _n,b～f _n,e, the data of m passage collection are output as after device after filtering so

$y_{m,n}\left(l\right)=\underset{l_n=0}{\overset{L_n-1}{\mathrm{\&Sigma;}}}{a}_n\left(l_n\right)x_m(l-l_n)---\left(7\right)$

2), with reference to Fig. 4, it is the schematic diagram of even linear array DBF of the present invention.To the output of n digital filter, with f _{n, 0}∈ [f _n,b, f _n,e] be reference frequency, divide and carry out respectively digital beam formation according to spatial domain, at θ _pthe weights that form wave beam in direction are

$w_{m,n}\left({\mathrm{\&theta;}}_p\right)=\exp [-j2\mathrm{\&pi;}(m-1)\frac{d}{c}{f}_{n,0}{\sin \mathrm{\&theta;}}_p],m=\mathrm{1,2},...,M---\left(8\right)$

Wherein d is array element distance; C is the light velocity.Wave beam is output as after forming

$z_{p,n}\left(l\right)=\underset{m=1}{\overset{M}{\mathrm{\&Sigma;}}}{w}_{m,n}^{*}\left({\mathrm{\&theta;}}_p\right)y_{m,n}\left(l\right)---\left(9\right)$

3) to z _p,n(l) extract according to every D point, D meets then carry out the FFT that K is ordered, obtain θ _pinterference noise in direction is at f _n,b～f _n,efrequency spectrum in scope

$Z_{p,n}\left(k\right)=\underset{l=0}{\overset{K-1}{\mathrm{\&Sigma;}}}{z}_{p,n}\left(\mathrm{lD}\right)\exp (-j2\mathrm{\&pi;}\frac{\mathrm{kl}}{K}),k=\mathrm{0,1},...,K-1---\left(10\right)$

4) according to certain criterion, as output minimum criteria, frequency spectrum is compared, be met the k of condition ₀, calculate corresponding frequency f _n,p.Suppose to round downwards; k _b=[DKf _n,b/ F _s]-K, k _e=[DKf _n,e/ F _s]-Ki _e, [] is rounding of the formula of rounding up.K ₀meet

$\underset{k=0,...,K-1}{\min }E\left\{{\left|Z_{p,n}\left(k\right)\right|}^2\right\}---\left(11\right)$

So corresponding θ _pf in direction _n,e～f _n,bthe frequency of the interference noise minimum in frequency range is

$f_{n,p}=(i_0+\frac{k_0}{K})\frac{F_s}{D}---\left(12\right)$

Work as k _e> k ₀> k _btime, i ₀=i _b; Work as k ₀> k _b> k _etime, i ₀=i _b; Work as k ₀< k _e< k _btime, i ₀=i _e.

5) frequency f Frequency spectrum ratio being obtained _n,p, according to direction θ _pwith frequency band f _n,b～f _n,eset up frequency optimum traffic storehouse, as shown in the table.

Table 1 frequency optimum traffic storehouse

Finally according to user's requirement, the position θ different to spatial domain _p, select one or more suitable radar transmitter frequencies.

With reference to Fig. 5, it is the simulation result figure that the present invention carries out adaptive frequency selection under disturbed condition.For receiving 2 × 8 railway digital echoed signals that bandwidth is 50-80MHz, be divided into 30 sections according to the frequency interval of 1MHz, and 120° space, orientation is divided into 9 regions, array element distance 2m.The frequency distribution situation that in figure, horizontal line representation space disturbs, "+" represents the optimum frequency that each frequency band is selected, " * " represents the frequency of selecting from frequency optimum traffic storehouse according to output minimum principle.As can be seen from the figure the frequency of operation of, selecting in each orientation has all been avoided interference.

Claims (2)

1. the metre wave radar adaptive frequency selection method based on airspace filter, is characterized in that step is as follows:

Step 1 frequency segmentation: stand-down M antenna channels distinguished simultaneously with F at radar _ssampling rate image data, then carries out digital filtering, and will receive division of signal is N frequency band; Described n digital filter transmission band scope is f _n,b～f _n,e, the data of m passage collection are output as after device after filtering

$y_{m,n}\left(l\right)=\underset{l_n=0}{\overset{L_n-1}{\mathrm{\&Sigma;}}}{a}_n\left(l_n\right)x_m(l-l_n)$

Wherein: a _n(l _n) be according to the filter coefficient of free transmission range design, L _nrepresent the exponent number of wave filter, x _m(l) (l=0,1,2 ...) represent m(m=1,2 ..., M) and the data of individual antenna channels through gathering after LNA;

Step 2 digital beam forms: the output of n digital filter divided and carried out DBF according to spatial domain,

$z_{p,n}\left(l\right)=\underset{m=1}{\overset{M}{\mathrm{\&Sigma;}}}{w}_{m,n}^{*}\left({\mathrm{\&theta;}}_p\right)y_{m,n}\left(l\right)$

Wherein w _m,n(θ _p), m=1,2 ..., M represents that antenna array is at θ _pin direction, form wave beam f _{n, 0}the corresponding weights of frequency, f _{n, 0}∈ [f _n,b, f _n,e];

Non-self-adapting weights $w_{m,n}\left({\mathrm{\&theta;}}_p\right)=\exp [-j2\mathrm{\&pi;}(m-1)\frac{d}{c}{f}_{n,0}{\sin \mathrm{\&theta;}}_p],$ Wherein d is array element distance; C is the light velocity; Step 3 time domain FFT processes: extract z according to every D point _p,n(l) carry out the FFT that K is ordered

$Z_{p,n}\left(k\right)=\underset{l=0}{\overset{K-1}{\mathrm{\&Sigma;}}}{z}_{p,n}\left(\mathrm{lD}\right)\exp (-j2\mathrm{\&pi;}\frac{\mathrm{kl}}{K})$

Wherein D meets k=0,1 ..., K-1, | Z _p,n(k) | be used for being described in θ _pin direction, interference noise is in frequency $(i+\frac{k}{K})\frac{F_s}{D}\&Element;[f_{n,b},f_{n,e}]$ Amplitude spectrum, i=i _bor i _e, to round downwards;

Step 4, Frequency spectrum ratio, obtains the frequency of interference noise minimum: the output that FFT is processed compares, and obtains θ _pf in direction _n,e～f _n,bthe frequency of the interference noise minimum in frequency range, is designated as f _n,p;

If k ₀satisfy condition $\underset{k=0,...,K-1}{\min }E\left\{{\left|Z_{p,n}\left(k\right)\right|}^2\right\},$ ? $f_{n,p}=(i_0+\frac{k_0}{K})\frac{F_s}{D},$ Suppose k _b=[DKf _n,b/ F _s]-Ki _b, k _e=[DKf _n,e/ F _s]-Ki _e, [] is rounding of the formula of rounding up; Work as k _e> k ₀> k _btime, i ₀=i _b; Work as k ₀> k _b> k _etime, i ₀=i _b; Work as k ₀< k _e< k _btime, i ₀=i _e.

2. the metre wave radar adaptive frequency selection method based on airspace filter according to claim 1, is characterized in that: the frequency f that the Frequency spectrum ratio that step 4 is carried out obtains more afterwards _n,p, according to direction θ _pwith frequency band f _n,b～f _n,eset up frequency optimum traffic storehouse:

Frequency optimum traffic storehouse

Then, according to user's requirement, the position θ different to spatial domain _p, select one or more suitable radar transmitter frequencies.