CN103837867B - A kind of AIS of utilization information carries out the method for higher-frequency radar antenna channels correction - Google Patents

Abstract

The invention provides a kind of method that the AIS of utilization information carries out the correction of higher-frequency radar antenna channels, radar is utilized to cover a large amount of ship AIS information received in marine site and ship echo, by analyzing the signal relation that it responds on different passage, carry out the channel correcting of monopole crossed loops antenna.The present invention without any need for the artificial auxiliary source arranged, only needs easy AIS receiving equipment completely, is a kind of passive and convenient-to-running channel correcting method, and can be extended to other antenna form.Advantage of the present invention is: cost is low, without the need for complex apparatus a large amount of during source calibration; Use a large amount of and widely distributed watercraft AIS signals, the channel correcting value obtained has good precision and stablizes; Calculated amount is little, to the not requirement of dwi hastasana system, applied widely.

Description

A kind of AIS of utilization information carries out the method for higher-frequency radar antenna channels correction

Technical field

The present invention relates to a kind of method that the AIS of utilization information carries out the correction of higher-frequency radar antenna channels.

Background technology

High-frequency ground wave radar is operated in the high-frequency band of 3-30MHz, can realize the large-scale over-the-horizon detection in ocean, has been widely used at present detecting extra large state parameter, as flow velocity, the flow direction, wave high.Because high frequency signal wavelength is suitable with maneuvering target (as aircraft, naval vessel etc.) yardstick, larger scattering cross-section can be obtained, thus also have huge potentiality in detection hard goal.

The antenna of higher-frequency radar employing array or close-coupled, is formed by spatial beams or scanning direction technology is estimated target azimuth.Traditional array formula antenna has the features such as precision is high, convenient signal treatment, but has the shortcomings such as cost is high, erection inconvenience equally.Monopole crossed loops antenna is a kind of close-coupled antenna, and it is made up of a monopole antenna and two orthogonal electric small loop antennas, easy to manufacture, erection is convenient and functional.In the ideal case, the horizontal directivity pattern of monopole antenna is a circle, and the directional diagram of two rings is respectively sinusoidal, cosine curve, and the amplitude peak response of three antennas should be consistent, and phase response is then identical.

The principle of monopole crossed loops antenna direction finding utilizes target echo to realize, i.e. the method for " than width " three channel amplitude response differences, and this method requires very high to the ideal behavior of antenna channels.In practical operation, due to the effect of the many factors such as difference and surrounding enviroment impact of each receiving cable hardware itself, amplitude and the phase propetry of antenna three passages are easy to change, and away from desirable antenna performance, thus cause antenna channels mismatch.The direct result of Channel Mismatch brings significant error to direction finding exactly, causes very large difficulty to the subsequent treatment of radar data.This becomes the key factor that restriction monopole crossed loops antenna is promoted the use of, working properly for ensureing radar, correction process must be done to this Channel Mismatch phenomenon, make error little as far as possible: on the one hand, improve technique when hardware makes as far as possible and ensure that each passage is as far as possible consistent; On the other hand, software approach estimating channel mismatch parameter can be adopted, carry out receiving cable amplitude and phase correction.

Existing software channel antidote can be divided into active correction and passive correction two class.In active correction, needing manually to arrange auxiliary source, in distance antenna enough distance transmitted reference signal, estimating the Channel Mismatch parameter of antenna by measuring amplitude that this known signal outputs signal at each receiving cable and phase place.CODAR company of the U.S. measures antenna radiation pattern and namely adopts the method, needs equipment extra in a large number, operation inconvenience, and does not have long stability.Chinese patent CN101013147A, title " high-frequency chirp radar directional diagram measuring method " provides and a kind ofly adopts single-frequency continuation sinusoidal, utilizes time frequency analysis to obtain the method for antenna radiation pattern, the method greatly reduces compared with classic method measures cost used, but still needing extra signal source, operation is inconvenience comparatively.

Passive bearing calibration does not need extra source, directly utilizes the echo information received to coordinate other priori estimating channel mismatch parameter.Compared to active correction, passive correction cost is low, easy and simple to handle, is the passage antidote be more suitable for.Chinese patent CN1566983A, title " a kind of method utilizing marine echo to carry out array channel calibration " and Chinese patent CN1847877A, title " a kind of method for correcting passive channels based on non-linear antenna array " gives two kinds and utilizes single angle of arrival marine echo to carry out the method for antenna channels correction, in early stage the developed array high-frequency ground wave radar of Wuhan University, obtain application.But these methods have the restriction of particular array shape, be not easily generalized to close-coupled antenna, and calculate slightly complicated, performance can not reach the level having source calibration; Chinese patent CN1804656A, title " a kind of method utilizing Ionospheric Echo to carry out higher-frequency radar aerial array channel correcting " provides a kind of method utilizing Ionospheric Echo to carry out antenna calibration, calculated amount is little and functional, but also exist ionospheric dependence, lack enough stability; Chinese patent CN102707270A, title " high-frequency ground wave radar relative antenna directional diagram automatic estimating method " gives a kind of method being calculated antenna radiation pattern by software, and the operand of the method is comparatively large, and practicality is still needed and further verified.

Comprehensive current existing passive bearing calibration, usual calculated amount more greatly and stable not, still lack be widely used, high performance passive bearing calibration.

This patent provides the new method that a kind of AIS of utilization information carries out the correction of higher-frequency radar antenna channels.Ship automatic identification system (AutomaticIdenficationSystem, AIS) is the new technology developed in the recent decade, identifies collision prevention between boats and ships and ship ship for boats and ships traffic control service.This standard was passed through in the conference of International Maritime Organization (IMO) in 1998, became the common standard of international ship overocean communications afterwards.AIS is based on time division multiple access (TDMA) (SOTDMA) Principle of Communication of self-organization, and marine ship utilizes the timing of VHF channel to broadcast the information of this ship to periphery.AIS information is divided into four classes: static information, multidate information, flight number relevant information, security related information.The information that the present invention mainly utilizes is position wherein, speed and temporal information.

Summary of the invention

For existing methodical limitation, the object of this invention is to provide a kind of method that the AIS of utilization information carries out the correction of higher-frequency radar antenna channels, utilize the AIS information that receives and ship echo, for high-frequency ground wave radar provides a kind of cheapness, accurately and can be applicable to the method for correcting passive channels of any antenna form.

Technical scheme of the present invention is:

A kind of AIS of utilization information carries out the method for higher-frequency radar antenna channels correction, by receive sea carry AIS transmitter ship AIS information and with radar detection to target echo match, division radar view is the angle grid in units of 1 degree, obtain the target of average each angle grid more than 10, then the target of coupling and its amplitude are weighted average treatment to carry out the correction of channel amplitude and phase value; Specifically comprise the following steps:

Step 1, on distance by radar-doppler spectral, three grades of algorithm of target detection based on CFAR CFAR are adopted to detect radar target point mark;

Step 2, the AIS data received are shown to range-Doppler spectrum on to polar coordinate transformation method the ship correspondence of carrying AIS transmitter by longitude and latitude;

Step 3, on distance by radar-doppler spectral, the point target that the ship and radar that carry AIS transmitter detect to be matched, from the longitude and latitude of the corresponding ship of AIS digital independent, calculate the angle of arrival of target relative to radar station;

Step 4, Statistics Division are in the target of same angle grid, average each angle grid accumulates more than 10 targets, by its echoed signal on two ring passages to the signal ratio amplitude weighting of monopole passage, thus obtain channel amplitude correction parameter and the phase correction parameters of this angle;

Step 5, comprehensive whole angular range, obtain the array manifold of antenna.

The specific implementation process of described step 1 is:

Adopt three grades of algorithm of target detection based on CFAR CFAR, the range Doppler spectrum of the radar data obtained in real time detects radar suspected target point mark, rejects the target of noise lower than 10dB.

The specific implementation process of described step 2 is:

Simple and easy AIS receiving trap commonplace is on the market used to receive marine AIS information of carrying AIS transmitter ship, obtain all speed, positional informations of carrying AIS transmitter ship in time period corresponding to radar play, reject wherein static ship, remaining ship is transformed on distance by radar-Doppler's two-dimensional spectrum to polar coordinate transformation method by longitude and latitude.

The specific implementation process of described step 3 is:

Find the combination of radar target and AIS object matching, when both differ within a distance element, two Doppler units, namely the match is successful, using the radar target after coupling as calibration source.

The specific implementation process of described step 4 is:

Be M angle grid by marine space division interested in radar view, the calibration source of known azimuth fallen into and arranges in angle grid, preserve the plural response of each calibration source at three passages, i.e. (X _1ij, X _2ij, X _3ij) form, wherein 1,2,3 represent monopole antenna and two rings, i represents angle grid sequence number, and j representative falls into the calibration source sequence number of this grid.

The specific implementation process of described step 5 is:

After average each position angle accumulates more than 10 calibration sources, to each distance grid in all calibration sources carry out width phase and signal amplitude weighted mean, obtain the passage amplitude and phase correction value in this direction, specific implementation step comprise:

For i-th grid, suppose there be Ni calibration source, be then reference channel with monopole antenna, the amplitude correction parameter finally obtained is:

$\hat{g}(i,k)=\frac{\underset{j=1}{\overset{N_i}{\mathrm{\Σ}}}\left(\right|X_{1\mathrm{ij}}|\·|X_{\mathrm{kij}}/X_{1\mathrm{ij}}\left|\right)}{\underset{j=1}{\overset{N_i}{\mathrm{\Σ}}}\left|X_{1\mathrm{ij}}\right|}$

Phase correction parameters is:

Wherein, i represents i-th angle grid, and k represents channel number, and j represents the calibration source sequence number of this angle grid, and Ni represents the calibration source sum of this angle grid;

The correction parameter of each angle grid is merged, obtains the antenna array stream shape of whole radar-covered area:

Wherein, M represents angle grid sum.

Innovative point of the present invention is: the bearing calibration first AIS information being incorporated into the whole array manifold of higher-frequency radar, a large amount of AIS information auxiliary under, the array manifold that precision is higher can be obtained.

Advantage of the present invention is: do not need extra signalization source, with low cost; Algorithm is easy, does not need as bearing calibration in the past, adopt complicated iteration optimization algorithm; Because coastland ship is numerous, calibration source is sufficient, the channel correcting parameter stability obtained and reliable; Calibration source from very large angular range, therefore can obtain corrected value to whole angular range grid respectively, instead of has to one group of corrected value to correct desired antenna characteristics; Bearing calibration without any restriction, can be transplanted to other antenna systems to antenna form completely.

Accompanying drawing explanation

Fig. 1 is the high-frequency ground wave radar fundamental diagram of the embodiment of the present invention in prior art.

Fig. 2 is the typical distance-Doppler spectrogram of the embodiment of the present invention in prior art.

Fig. 3 is monopole crossed loops antenna radiation pattern in prior art.

Fig. 4 is process flow diagram of the present invention.

Embodiment

Below in conjunction with accompanying drawing, more detailed explanation is done to the present invention.

High-frequency ground wave radar principle of work as shown in Figure 1.High-frequency ground wave radar is made up of emitting antenna, receiving antenna array, transmitter, receiver etc. usually, usually transmitting-receiving location altogether.Transmitting radar antenna is length is the vertical whip antenna that radar wavelength 1/4 is grown, the outside radiated electromagnetic wave of omnidirectional.Electromagnetic wave is at sea propagated, and runs into the meetings such as the wave of special parameter, ship, island by Electromagnetic scattering, by radar receiver is received.Radar adopts linear frequency modulation system usually, in each frequency sweep cycle, complete transmitting, receive, carry out after demodulating received signal amplifying, filtering, mixing, sampling and fast time domain discrete Fourier transformation obtain distance spectrum data.These data are uploaded on PC by usb bus carries out subsequent treatment.By carrying out second time discrete Fourier transformation to the distance spectrum data of N number of frequency sweep cycle, realizing the separation of velocity information, obtaining distance-Doppler two-dimensional spectrum, therefrom can extract extra large state and target information.Strong echo main in range-Doppler spectrum is sea clutter and target echo, sometimes also there is Ionospheric Echo and Radio frequency interference (RFI) echo etc.Wherein sea clutter is the Bragg diffraction that the wave in specific wavelength special exercise direction causes, and is divided into strong single order peak and is distributed in the Second Order Continuous spectrum on its both sides.Target echo major part is distributed between two single order peaks, and Fig. 2 is typical distance by radar-Doppler's two-dimensional spectrum, and shown spectrogram is from monopole antenna, and the spectrogram of two rings is similar with it.

The ideal orientation figure of monopole crossed loops as shown in Figure 3, when there being echo signal incident from certain angle of arrival, can solve angle by the signal relation compared on three passages.But due to the impact of hardware and surrounding enviroment factor, the actual direction figure of antenna can depart from ideal situation, must make correction.If the mutual relationship of target three passage echoes in some angles in known reality, just can obtain the channel correcting value of this angle.

Key of the present invention is the angle information how determining a large amount of target correction source.Target on distance by radar-Doppler's two-dimensional spectrum can solve Distance geometry speed easily, but cannot directly know its arrival bearing.But interpolation AIS supplementary can provide required angle information.

Schematic flow sheet of the present invention is shown in Fig. 4, and concrete implementation step is as described below:

Step 1, adopt three grades of algorithm of target detection based on CFAR (CFAR), the range Doppler spectrum of radar data detects radar suspected target point mark, rejects the target that signal to noise ratio (S/N ratio) is lower.

Step 2, easy AIS receiving trap is used to receive marine vessel AIS information, obtain all ship speed, positional information in time period corresponding to radar play, reject static AIS ship, remaining AIS target is passed through the method migration of coordinate transform on distance by radar-Doppler's two-dimensional spectrum.

Step 3, find the combination of radar target and AIS object matching, when both differ within a distance element, two Doppler units, just calculation does that the match is successful, and the radar target after coupling can be used as calibration source.

Step 4, be M angle grid by marine space division interested in radar view, the calibration source of known azimuth is fallen in the angle grid of setting, reads from the range-Doppler spectrum of radar and preserve the plural response X of each calibration source in three antenna channels _1ij, X _2ij, X _3ij, wherein 1,2,3 represent monopole antenna and two rings, i represents angle grid sequence number, and j representative falls into the calibration source sequence number of this grid.

Step 5, accumulate a large amount of different azimuth calibration source after, statistical study is carried out to all calibration sources in each distance grid, obtains the passage amplitude and phase correction value in this direction.Specific practice is:

For i-th grid, suppose there is N _iindividual calibration source, be then reference channel with monopole antenna, the amplitude correction parameter finally obtained is:

$\hat{g}(i,k)=\frac{\underset{j=1}{\overset{N_i}{\mathrm{\Σ}}}\left(\right|X_{1\mathrm{ij}}|\·|X_{\mathrm{kij}}/X_{1\mathrm{ij}}\left|\right)}{\underset{j=1}{\overset{N_i}{\mathrm{\Σ}}}\left|X_{1\mathrm{ij}}\right|}$

Phase correction parameters is:

Wherein i represents i-th angle grid, and k represents channel number, and k=1 or 2 or 3, j represents the calibration source sequence number of this angle grid, and Ni represents the calibration source sum of this angle grid.

The correction parameter of each angle grid is merged, obtains the antenna array stream shape of whole radar-covered area:

Wherein M represents angle grid sum.

Claims (6)

1. the method utilizing AIS information to carry out the correction of higher-frequency radar antenna channels, it is characterized in that: by receive sea carry AIS transmitter ship AIS information and with radar detection to target echo match, division radar view is the angle grid in units of 1 degree, obtain the target of average each angle grid more than 10, then the target of coupling and its amplitude are weighted average treatment to carry out the correction of channel amplitude and phase value; Specifically comprise the following steps:

Step 1, on distance by radar-doppler spectral, three grades of algorithm of target detection based on CFAR CFAR are adopted to detect radar target point mark;

Step 2, the AIS data received are shown to range-Doppler spectrum on to polar coordinate transformation method the ship correspondence of carrying AIS transmitter by longitude and latitude;

Step 3, on distance by radar-doppler spectral, the point target that the ship and radar that carry AIS transmitter detect to be matched, from the longitude and latitude of the corresponding ship of AIS digital independent, calculate the angle of arrival of target relative to radar station;

Step 4, Statistics Division are in the target of same angle grid, average each angle grid accumulates more than 10 targets, by its echoed signal on two ring passages to the signal ratio amplitude weighting of monopole passage, thus obtain channel amplitude correction parameter and the phase correction parameters of this angle;

Step 5, comprehensive whole angular range, obtain the array manifold of antenna.

2. a kind of AIS of utilization information according to claim 1 carries out the method for higher-frequency radar antenna channels correction, it is characterized in that: the specific implementation process of described step 1 is:

Adopt three grades of algorithm of target detection based on CFAR CFAR, the range Doppler spectrum of the radar data obtained in real time detects radar suspected target point mark, rejects the target of noise lower than 10dB.

3. a kind of AIS of utilization information according to claim 2 carries out the method for higher-frequency radar antenna channels correction, it is characterized in that: the specific implementation process of described step 2 is:

AIS receiving trap is used to receive marine AIS information of carrying AIS transmitter ship, obtain all speed, positional informations of carrying AIS transmitter ship in time period corresponding to radar play, reject wherein static ship, remaining ship is transformed on distance by radar-Doppler's two-dimensional spectrum to polar coordinate transformation method by longitude and latitude.

4. a kind of AIS of utilization information according to claim 3 carries out the method for higher-frequency radar antenna channels correction, it is characterized in that: the specific implementation process of described step 3 is:

Find the combination of radar target and AIS object matching, when both differ a distance element, two Doppler

Within unit, namely the match is successful, using the radar target after coupling as calibration source.

5. a kind of AIS of utilization information according to claim 4 carries out the method for higher-frequency radar antenna channels correction, it is characterized in that: the specific implementation process of described step 4 is:

Be M angle grid by marine space division interested in radar view, the calibration source of known azimuth fallen in set angle grid, distance-Doppler figure reads and preserves the plural response X of each calibration source at three passages _1ij, X _2ij, X _3ij, wherein 1,2,3 represent channel number, i represents angle grid sequence number, and j representative falls into the calibration source sequence number of this grid.

6. a kind of AIS of utilization information according to claim 5 carries out the method for higher-frequency radar antenna channels correction, it is characterized in that: the specific implementation process of described step 5 is:

Average each angle grid carries out width phase and signal amplitude weighted mean to all calibration sources in each angle grid after accumulating more than 10 calibration sources, obtains channel amplitude correction parameter and the phase correction parameters of this angle grid; Specific implementation step comprises:

For i-th grid, suppose there be Ni calibration source, be then reference channel with monopole antenna, the amplitude correction parameter finally obtained is:

$\hat{g}(i,k)=\frac{\underset{j=1}{\overset{N_i}{\Σ}}\left(\right|X_{1ij}|\·|X_{kij}/X_{1ij}\left|\right)}{\underset{j=1}{\overset{N_i}{\Σ}}\left|X_{1ij}\right|}$

Phase correction parameters is:

Wherein, i represents angle grid sequence number, and k represents channel number, and j representative falls into the calibration source sequence number of this grid, and Ni represents the calibration source sum of this angle grid;

The correction parameter of each angle grid is merged, obtains the antenna array stream shape of whole radar-covered area:

Wherein, M represents angle grid sum.