CN105717494A - Design method for sea clutter inhibition curve of marine radar based on wavelet transformation - Google Patents

Abstract

The invention relates to a design method for a sea clutter inhibition curve of a marine radar based on wavelet transformation, and belongs to the technical field of signal processing of the marine navigation radar. Echo data of the radar in the measuring range is decomposed via discrete wavelet transformation, a high-frequency coefficient is zeroed, and a high-level approximate part is used to estimate power level of sea clutters. A corresponding adjustable sea clutter inhibition curve is calculated according to a range parameter and a sea clutter inhibition intensity parameter, and the estimated power level of the practical sea clutters is overlapped with the adjustable sea clutter inhibition curve to obtain a general sea clutter inhibition curve. The inhibition curve design method is highly adaptive to a traditional sea clutter inhibition method relied on statistical characteristics, it is not required to predict distribution which the power level of background clutters obeys in advance, the method has a good inhibition effect for near sea clutters, and the problem that sea clutters surrounding the circular center of a radar screen are hard to eliminate is overcome; and the design method is flexible to use, and includes different inhibition levels, so that a user can carry out sea clutter inhibition of different levels according to practical sea-condition information.

Description

A kind of marine radar ocean clutter cancellation curve design method based on wavelet transformation

Technical field

The invention belongs to marine navigation radar signal processing technology field, relate to a kind of marine radar ocean clutter cancellation curve design method based on wavelet transformation.

Background technology

In recent years, shipping industry is flourish, the development that matched boat-carrying electronic industry also rapidly pushes ahead vigorously.Ship-navigation radar goes to sea as ship for civil use one of equipment of indispensability, and its function quality direct relation the market competitiveness.The main standard weighing a radar is exactly weigh radar to the accurate of clutter recognition and effectiveness.Marine radar is mainly in operations offshore, and clutter mostlys come from wave, therefore how effectively sea clutter to be filtered, and is the problems always studied of people.

Traditional ocean clutter cancellation method is to adopt STC curve, and STC curve can increase receiver dynamic range on the one hand, and on the other hand, STC curve can also eliminate the shortcoming that near boats and ships, sea clutter intensity is high.People adopted theory of statistics to eliminate sea clutter later, but this method have to predict the statistical property of sea clutter in advance, such as Rayleigh distributed, logarithm normal distribution, Wei Buer distribution etc..When signal processing unit is determined and removed to process clutter with a certain model, once sea situation changes, false alarm rate will rise rapidly.In recent years, the Radar Products major part of major part coastal fisherman buying is external radar, such as Japan Furuno, Germany Atlas, in the middle-size and small-size radar receiver of these companies, major part adopts log IF amplifier, after linear envelope detection, send into base band process, although closely strong radar echo signal is had certain suppression by log IF amplifier, but echo-signal nearby is still high than signal intensity at a distance, if directly bringing detection judgement, can find radar screen is occupied by radar clutter near the range ring in the center of circle is substantially all, target and clutter cannot be told, even if adopting CFAR to process, effect is still not notable.

Summary of the invention

In view of this, it is an object of the invention to provide a kind of marine radar ocean clutter cancellation curve design method based on wavelet transformation, the method is without which kind of distribution Corpus--based Method Predicting Performance Characteristics sea clutter obeys, but utilize the multiple dimensioned resolution analysis characteristic of small echo that sea clutter is decomposed, with approximate part, sea clutter power level is estimated；The actual sea situation information of reaction that can be authentic and valid, can eliminate again the noise intensity nearby brought due to the distance problem problem higher than noise intensity at a distance；Moreover, the method is also configured to adjustable STC curve, according to different sea situations, effectively sea clutter is filtered in real time.

For reaching above-mentioned purpose, the present invention provides following technical scheme:

A kind of marine radar ocean clutter cancellation curve design method based on wavelet transformation, comprises the following steps:

S1: admission current radar echo data, is generally the data in a distance unit, arranges according to range, only retains the data in range, and the data outside range are removed, to reduce operand；

S2: the radar return data of admission are carried out wavelet decomposition, and wavelet decomposition is divided into two parts, and a part is approximate part CA (i), and a part is detail section CD (i), and wherein i is Decomposition order；

S3: the detail section coefficient zero setting that will decompose, only retains high-rise approximate part, then rebuilds original radar return data with high-rise approximation coefficient；

S4: using the radar data after reconstruction as sea clutter background power estimated value, in this, as STC (i)；

S5: reading radar measuring range parameters, range changes along with the operation of radar operation personnel, when increasing range, the radar return data of intercepting increase；

S6: read current sea clutter inhibition strength parameter, when strengthening sea clutter suppression, intensive parameter can increase；In this method, ocean clutter cancellation intensive parameter scope is set to 0～100；

S7: obtain adjustable STC curve data, this STC curve data is for being previously stored in internal memory, and corresponding one of each ocean clutter cancellation intensity suppresses curve；

S8: superposed with adjustable ocean clutter cancellation curve stc (j) by ocean clutter cancellation curve stc (i) calculated under actual sea situation, as total ocean clutter cancellation curve.

Further, in described step S2, specifically comprising the following steps that of wavelet decomposition

S21: determine and decompose wavelet basis used: conventional wavelet basis has SymN, Haar, DBN, the wavelet basis suitable according to concrete signal behavior and numerical value, use DB10 small echo in this method；

S22: determine that choosing of Decomposition order i:i can not be excessive, can not be too small；Crossing conference causes computing complicated, and real-time is not enough；Too small meeting causes approximate part can not effectively represent clutter power level；The Decomposition order selected in this method is 5；

S23: echo data is carried out wavelet decomposition with known wavelet basis and Decomposition order, decomposing publicity is:

$\left\{\begin{array}{c}{\mathrm{CA}}_{i,k}=\underset{n=-\mathrm{\∞}}{\overset{\mathrm{\∞}}{\Σ}}{\mathrm{CA}}_{i-1,n}\×h_{n-2k}\\ {\mathrm{CD}}_{i,k}=\underset{n=-\mathrm{\∞}}{\overset{\mathrm{\∞}}{\Σ}}{\mathrm{CA}}_{i-1,n}\×g_{n-2k}\end{array}\right.$

Wherein, N is that signal sampling is counted, k=0,1, L, and N-1, h and g is low pass and high pass filter respectively, and they are mutually orthogonal.

Further, in described step S7, after obtaining measuring range parameters range and ocean clutter cancellation intensive parameter k, it is as follows that ocean clutter cancellation curve corresponding for each of which range points j asks for step:

S71: determining that the quantization N:N that counts is together decided on by range, sample rate, extraction yield, computing formula is:Wherein, range for choosing range, f_NyqFor sample rate, distance is distance element length, and M is extraction yield；Extraction yield be disposed to when wide range minimizing data volume, to alleviate the pressure of subsequent calculations；

S72: determine stepped intervals interval, computing formula isWherein start is the starting point of attenuation curve, and end is the terminating point of attenuation curve, and the quantization that N is in previous step is counted；

S73: calculating the minimum point in attenuation curve, and take absolute value, computing formula is:

${\mathrm{stc}}_{\min }=abs{\left(min\right(k\·{\log }_{10}\left(\frac{start}{start+(j-1)\·\mathrm{int}erval}\right)\left)\right)}_{j=1KN}$

Wherein, abs is for taking absolute value, and min is for taking minima, and k is ocean clutter cancellation intensity；

S74: according to different range points j, calculating corresponding standard pad value stc (j), specific formula for calculation is:

$stc\left(j\right)=k\·{\log }_{10}\left(\frac{start}{start+(j-1)\·\mathrm{int}erval}\right)+{\mathrm{stc}}_{min}$

Wherein, k is ocean clutter cancellation intensity.

The beneficial effects of the present invention is: 1) adaptability is good: tradition ocean clutter cancellation scheme needs suppose that sea clutter obeys certain distribution (rayleigh distributed, logarithm normal distribution, Wei Buer distribution, k distribution), then takes specific method to filter sea clutter again.Directly take wavelet transformation to decompose herein, predict sea clutter background power level with wavelet transformation approximate part, be from concrete sea situation, directly obtain sea clutter background power information, there is well adapting to property.2) filtration result is good: present invention border sea situation factually of digging up the roots is extracted outside sea clutter background power information, is additionally provided with the curve of different inhibition strength, time specifically used, according to demand, can effectively adjust inhibition strength, as far as possible effectively sea clutter be filtered.

Accompanying drawing explanation

In order to make the purpose of the present invention, technical scheme and beneficial effect clearly, the present invention provides drawings described below to illustrate:

Fig. 1 is the flow chart of the method for the invention；

Fig. 2 is wavelet function feedback schematic diagram；

Fig. 3 is raw radar data figure after wavelet decomposition, and the upper left corner the first width figure is approximate part coefficient pattern, and all the other 5 width are detail section figure under the different number of plies；

Fig. 4 is adjustable ocean clutter cancellation curve chart；

Fig. 5 is original echo image and background clutter power level estimated value comparison diagram, and upper figure is original echo image, and figure below is background clutter power level estimated value；

Fig. 6 is ocean clutter cancellation intensity when being 0, the design sketch of actual measurement gained；

Fig. 7 is ocean clutter cancellation intensity when being 20, the design sketch of actual measurement gained；

Fig. 8 is ocean clutter cancellation intensity when being 60, the design sketch of actual measurement gained；

Fig. 9 is ocean clutter cancellation intensity when being 80, the design sketch of actual measurement gained.

Detailed description of the invention

Below in conjunction with accompanying drawing, the preferred embodiments of the present invention are described in detail.

Fig. 1 is the flow chart of the method for the invention, as it can be seen, this method comprises the following steps:

S1: admission current radar echo data, is generally the data in a distance unit, arranges according to range, only retains the data in range, and the data outside range are removed, to reduce operand；

S2: the radar return data of admission are carried out wavelet decomposition, and wavelet decomposition is divided into two parts, and a part is approximate part CA (i), and a part is detail section CD (i), and wherein i is Decomposition order；

S3: the detail section coefficient zero setting that will decompose, only retains high-rise approximate part, then rebuilds original radar return data with high-rise approximation coefficient；

S4: using the radar data after reconstruction as sea clutter background power estimated value, in this, as STC (i)；

S5: reading radar measuring range parameters, range changes along with the operation of radar operation personnel, when increasing range, the radar return data of intercepting increase；

S6: read current sea clutter inhibition strength parameter, when strengthening sea clutter suppression, intensive parameter can increase；In this method, ocean clutter cancellation intensive parameter scope is set to 0～100；

S7: obtain adjustable STC curve data, this STC curve data is for being previously stored in internal memory, and corresponding one of each ocean clutter cancellation intensity suppresses curve；

S8: superposed with adjustable ocean clutter cancellation curve stc (j) by ocean clutter cancellation curve stc (i) calculated under actual sea situation, as total ocean clutter cancellation curve.

Fig. 2 is wavelet function feedback schematic diagram, in the present embodiment, in described step S2, and specifically comprising the following steps that of wavelet decomposition

S21: determine and decompose wavelet basis used: conventional wavelet basis has SymN, Haar, DBN, the wavelet basis suitable according to concrete signal behavior and numerical value, use DB10 small echo in this method；

S22: determine that choosing of Decomposition order i:i can not be excessive, can not be too small；Crossing conference causes computing complicated, and real-time is not enough；Too small meeting causes approximate part can not effectively represent clutter power level；The Decomposition order selected in this method is 5；

S23: echo data is carried out wavelet decomposition with known wavelet basis and Decomposition order, decomposing publicity is:

$\left\{\begin{array}{c}{\mathrm{CA}}_{i,k}=\underset{n=-\mathrm{\∞}}{\overset{\mathrm{\∞}}{\Σ}}{\mathrm{CA}}_{i-1,n}\×h_{n-2k}\\ {\mathrm{CD}}_{i,k}=\underset{n=-\mathrm{\∞}}{\overset{\mathrm{\∞}}{\Σ}}{\mathrm{CA}}_{i-1,n}\×g_{n-2k}\end{array}\right.$

Wherein, N is that signal sampling is counted, k=0,1, L, and N-1, h and g is low pass and high pass filter respectively, and they are mutually orthogonal.Fig. 3 is raw radar data figure after wavelet decomposition, and the upper left corner the first width figure is approximate part coefficient pattern, and all the other 5 width are detail section figure under the different number of plies.

In described step S7, after obtaining measuring range parameters range and ocean clutter cancellation intensive parameter k, it is as follows that ocean clutter cancellation curve corresponding for each of which range points j asks for step:

S71: determining that the quantization N:N that counts is together decided on by range, sample rate, extraction yield, computing formula is:Wherein, range for choosing range, f_NyqFor sample rate, distance is distance element length, and M is extraction yield；Extraction yield be disposed to when wide range minimizing data volume, to alleviate the pressure of subsequent calculations；

S72: determine stepped intervals interval, computing formula isWherein start is the starting point of attenuation curve, and end is the terminating point of attenuation curve, and the quantization that N is in previous step is counted；

S73: calculating the minimum point in attenuation curve, and take absolute value, computing formula is:

${\mathrm{stc}}_{\min }=abs{\left(min\right(k\·{\log }_{10}\left(\frac{start}{start+(j-1)\·\mathrm{int}erval}\right)\left)\right)}_{j=1KN}$

Wherein, abs is for taking absolute value, and min is for taking minima, and k is ocean clutter cancellation intensity；

S74: according to different range points j, calculating corresponding standard pad value stc (j), specific formula for calculation is:

$stc\left(j\right)=k\·{\log }_{10}\left(\frac{start}{start+(j-1)\·\mathrm{int}erval}\right)+{\mathrm{stc}}_{min}$

Wherein, k is ocean clutter cancellation intensity.Fig. 4 is adjustable ocean clutter cancellation curve chart.

As it is shown in figure 5, be the radar return data that in this example, in 0.5 nautical mile of range, reality obtains shown in upper figure, figure below is the sea clutter background power estimated value estimated through context of methods.

As shown in Figure 6, being the design sketch herein when Practical Project is verified, this figure ocean clutter cancellation intensity is 0, namely processes without sea clutter suppression, as can be seen from the figure substantially can not be resolved target near boats and ships.

As it is shown in fig. 7, in this figure, ocean clutter cancellation intensity is 20, it can be seen that the sea clutter near boats and ships obtains a degree of suppression.

As shown in Figure 8, in this figure, ocean clutter cancellation intensity is 60, it can be seen that the sea clutter image major part in range is filtered out.

As it is shown in figure 9, ocean clutter cancellation intensity is 80 in this figure, it can be seen that the sea clutter image in range is substantially filtered out totally, target is high-visible.

What finally illustrate is, preferred embodiment above is only in order to illustrate technical scheme and unrestricted, although the present invention being described in detail by above preferred embodiment, but skilled artisan would appreciate that, in the form and details it can be made various change, without departing from claims of the present invention limited range.

Claims (3)

1. the marine radar ocean clutter cancellation curve design method based on wavelet transformation, it is characterised in that: comprise the following steps:

S1: admission current radar echo data, is generally the data in a distance unit, arranges according to range, only retains the data in range, and the data outside range are removed, to reduce operand；

S2: the radar return data of admission are carried out wavelet decomposition, and wavelet decomposition is divided into two parts, and a part is approximate part CA (i), and a part is detail section CD (i), and wherein i is Decomposition order；

S3: the detail section coefficient zero setting that will decompose, only retains high-rise approximate part, then rebuilds original radar return data with high-rise approximation coefficient；

S4: using the radar data after reconstruction as sea clutter background power estimated value, in this, as STC (i)；

S5: reading radar measuring range parameters, range changes along with the operation of radar operation personnel, when increasing range, the radar return data of intercepting increase；

S6: read current sea clutter inhibition strength parameter, when strengthening sea clutter suppression, intensive parameter can increase；In this method, ocean clutter cancellation intensive parameter scope is set to 0～100；

S7: obtain adjustable STC curve data, this STC curve data is for being previously stored in internal memory, and corresponding one of each ocean clutter cancellation intensity suppresses curve；

S8: superposed with adjustable ocean clutter cancellation curve stc (j) by ocean clutter cancellation curve stc (i) calculated under actual sea situation, as total ocean clutter cancellation curve.

2. a kind of marine radar ocean clutter cancellation curve design method based on wavelet transformation according to claim 1, it is characterised in that: in described step S2, specifically comprising the following steps that of wavelet decomposition

S21: determine and decompose wavelet basis used: conventional wavelet basis has SymN, Haar, DBN, the wavelet basis suitable according to concrete signal behavior and numerical value, use DB10 small echo in this method；

S22: determine that choosing of Decomposition order i:i can not be excessive, can not be too small；Crossing conference causes computing complicated, and real-time is not enough；Too small meeting causes approximate part can not effectively represent clutter power level；The Decomposition order selected in this method is 5；

S23: echo data is carried out wavelet decomposition with known wavelet basis and Decomposition order, decomposing publicity is:

$\left\{\begin{array}{c}{\mathrm{CA}}_{i,k}=\underset{n=-\mathrm{\∞}}{\overset{\mathrm{\∞}}{\Σ}}{\mathrm{CA}}_{i-1,n}\×h_{n-2k}\\ {\mathrm{CD}}_{i,k}=\underset{n=-\mathrm{\∞}}{\overset{\mathrm{\∞}}{\Σ}}{\mathrm{CA}}_{i-1,n}\×g_{n-2k}\end{array}\right.$

Wherein, N is that signal sampling is counted, k=0,1, L, and N-1, h and g is low pass and high pass filter respectively, and they are mutually orthogonal.

3. a kind of marine radar ocean clutter cancellation curve design method based on wavelet transformation according to claim 2, it is characterized in that: in described step S7, after obtaining measuring range parameters range and ocean clutter cancellation intensive parameter k, it is as follows that ocean clutter cancellation curve corresponding for each of which range points j asks for step:

S71: determining that the quantization N:N that counts is together decided on by range, sample rate, extraction yield, computing formula is:Wherein, range for choosing range, f_NyqFor sample rate, distance is distance element length, and M is extraction yield；Extraction yield be disposed to when wide range minimizing data volume, to alleviate the pressure of subsequent calculations；

S72: determine stepped intervals interval, computing formula isWherein start is the starting point of attenuation curve, and end is the terminating point of attenuation curve, and the quantization that N is in previous step is counted；

S73: calculating the minimum point in attenuation curve, and take absolute value, computing formula is:

${\mathrm{stc}}_{\min }=ads{\left(\min \right(k\·{\log }_{10}\left(\frac{start}{start+(j-1)\·\mathrm{int}erval}\right)\left)\right)}_{j=1KN}$

Wherein, abs is for taking absolute value, and min is for taking minima, and k is ocean clutter cancellation intensity；

S74: according to different range points j, calculating corresponding standard pad value stc (j), specific formula for calculation is:

$stc\left(j\right)=k\·{\log }_{10}\left(\frac{start}{start+(j-1)\·\mathrm{int}erval}\right)+{\mathrm{stc}}_{\min }$

Wherein, k is ocean clutter cancellation intensity.