Coherent marine radar target enhancement technology based on Doppler processing
阅读说明：本技术 基于多普勒处理的相参航海雷达目标增强技术 (Coherent marine radar target enhancement technology based on Doppler processing ) 是由 胡晨曦 孙珂 贾成成 王艳军 于 2019-09-23 设计创作，主要内容包括：本发明一种基于多普勒处理的相参航海雷达目标增强技术,以相参接收机为基础,设计合理的信号处理流程,在不改变现有航海雷达的包括天线转速及脉冲重频的工作方式的前提下,利用数据缓存区,采用滑窗FFT的方法进行多普勒处理,形成一幅距离—多普勒二维图,并进行本船运动补偿以使静止目标位于零多普勒通道；然后进行自适应杂波抑制例如海杂波、雨杂波的动杂波；按照多普勒特征分别提取静止目标和运动目标并存储,最后利用双阈值检测和重叠双色图对静止和运动目标的回波图像进行分别调节和综合显示。本发明通过杂波自动抑制大幅度改善海杂波条件下的目标检测能力,并将高威胁的运动目标突出显示,充分发挥相参航海雷达的优越性能。(The invention relates to a coherent marine radar target enhancement technology based on Doppler processing, which is based on a coherent receiver, designs a reasonable signal processing flow, utilizes a data cache area to perform Doppler processing by adopting a sliding window FFT method on the premise of not changing the working mode of the conventional marine radar, including the antenna rotating speed and the pulse repetition frequency, forms a distance-Doppler two-dimensional graph, and performs ship motion compensation to enable a static target to be positioned in a zero Doppler channel; then, self-adaptive clutter suppression is carried out on dynamic clutter such as sea clutter and rain clutter; and finally, respectively adjusting and comprehensively displaying the echo images of the static target and the moving target by using double-threshold detection and an overlapped double-color image. The invention greatly improves the target detection capability under the sea clutter condition through clutter automatic suppression, highlights the high-threat moving target and fully exerts the superior performance of the coherent marine radar.)
1. A coherent marine radar target enhancement technology based on Doppler processing is characterized in that a coherent receiver is used as a basis, a reasonable signal processing flow is designed, Doppler processing is carried out by adopting a sliding window FFT method on the premise of not changing the working mode of the conventional marine radar including the antenna rotating speed and the pulse repetition frequency, a distance-Doppler two-dimensional graph is formed when data of each pulse arrives, and ship motion compensation is carried out to enable a static target to be located in a zero Doppler channel; then, estimating clutter characteristics by using a neighboring sector, carrying out self-adaptive clutter suppression, and respectively extracting and storing a static target and a moving target according to Doppler characteristics; finally, respectively adjusting and comprehensively displaying the echo images of the static and moving targets by using double-threshold detection and an overlapped double-color image; the signal processing flow specifically comprises the steps that radar radio frequency echo signals enter a coherent receiver after being received by an antenna, the radar radio frequency echo signals are amplified, down-converted and filtered by the coherent receiver to form intermediate frequency signals, the intermediate frequency signals are converted into digital signals through AD (analog-to-digital) and stored in a data cache region after being subjected to distance dimension processing including matched filtering; the buffer area stores a series of coherent pulse data including current pulse data for coherent processing, a group of Doppler filters are formed in each range gate, and a range-Doppler image is generated; then, a zero Doppler channel is corrected through the ship motion compensation module, and the clutter suppression module suppresses dynamic clutter such as sea clutter and rain clutter; and then extracting moving and static targets on the processed range-Doppler image, and respectively finishing the processing and fusion display of the moving and static targets on the comprehensive display module.
2. The doppler processing based coherent marine radar target enhancement technique of claim 1, wherein echo data for each pulse of the marine radar is processed in a range dimension including matched filtering and stored in a data cache module. The data buffer module stores echo data of N pulses in total, when the echo data of each pulse arrives, the data buffer module firstly updates the stored data in a first-in first-out mode, then rearranges and outputs the data, and packs and outputs the data corresponding to the same distance unit in the N pulses according to the sequence of the distance unit from near to far.
3. The doppler processing based target enhancement technique for coherent marine radar as claimed in claim 2, wherein the vessel motion compensation module calculates the doppler channel of the stationary target using the vessel heading, velocity and radar beam pointing direction and compensates in the range-doppler plot.
4. The Doppler processing based coherent marine radar target enhancement technique of claim 3, wherein a Doppler filter bank is used to perform coherent accumulation of data output from the data cache module and generate a "range-Doppler" map; the filter bank first performs weighting processing (such as Hanning window) on the data to reduce side lobes, then calculates the filter output corresponding to each Doppler channel using Fast Fourier Transform (FFT), and then performs linear detection
5. The Doppler processing based coherent marine radar target enhancement technique of claim 4, wherein the clutter suppression module estimates the energy distribution characteristics of clutter in the range and Doppler dimensions using neighboring sectors and performs adaptive suppression to facilitate target observation.
6. The Doppler processing based coherent marine radar target enhancement technique according to claim 5, wherein the target extraction module detects the range-Doppler map after the ship motion compensation and clutter suppression, traverses each range cell, and extracts a zero-Doppler channel signal as a stationary target; and extracting a maximum value signal on a non-zero Doppler channel as a moving target.
7. The Doppler processing based coherent marine radar target enhancement technique of claim 6, wherein the integrated display processes and displays the moving and stationary target information obtained by the target extraction module. By setting independent adjustable detection threshold values for the moving target and the static target, the observation of the small target moving at high speed is not influenced while strong terrestrial echo is inhibited; and the moving target is highlighted on the radar interface in a target color separation display mode.
The technical field is as follows:
the invention relates to the technical field of radars, in particular to a coherent marine radar signal processing technology.
Background art:
the navigation radar is mainly used for detecting and tracking a marine target, assisting navigation and collision avoidance of a ship and guaranteeing navigation safety. With the increasingly complex navigation environment of the ship, the performance of the navigation radar, particularly the discovery capability of surrounding targets under the condition of sea clutter, is directly related to the navigation safety of the ship and the life safety of personnel on the ship. Since 2004, the International Maritime Organization (IMO) began to encourage the use of coherent radar to improve target detection capability under severe sea clutter conditions.
Coherent means that the initial phase between the radar transmitted pulses is deterministic, which is a prerequisite for using the doppler effect. In order to fully exert the superior performance of the coherent radar, the marine radar must design an adaptive signal processing algorithm to be combined with the coherent radar. The signal processing flow of the conventional pulse Doppler radar is as follows: the antenna beam dwells at a location during which a coherent burst of pulses is transmitted. For each train of coherent pulses, the coherent processing forms a set of doppler filters within each range gate, producing a range-doppler plot. The range-doppler cells are then detected to generate a set of target reports. And the beam performs grid type scanning in a designated space to form final target detection output. However, the marine radar in the prior art adopts a mechanical scanning antenna with a fixed rotating speed of 24 or 48r/min, and cannot perform beam dwell at a certain position, because of the requirement of distance range, the Pulse Repetition Frequency (PRF) is mostly 500 to 2000Hz, and the antenna beam is narrow (usually 0.8 ° or 1.3 °), and the azimuth scanning precision can be greatly reduced by directly performing coherent processing by taking N pulses as a group.
The sea clutter situations faced by the marine radar are complex and changeable, taking the sea clutter as an example, the distribution of sea clutter energy along the distance dimension and the Doppler dimension under different sea conditions, wind speeds, incident angles and other conditions is different, the literature records that the wave crests of the constant waves are at an angle of 120 degrees to the maximum extent according to the calculation of Stokes, and if more energy is supplied to the waves, for example, the waves start to be broken (wave burst) under the blowing of larger wind power, so that the clutter situations are more complex, and the clutter has anisotropy and is difficult to adopt an empirical formula. The marine radar needs to pay attention to stationary targets such as islands and buoys and moving targets such as ships and boats at the same time, and the radar can distinguish the two types of targets and adopt different processing modes after Doppler information is obtained. In addition, the coherent marine radar also needs to display the additionally acquired target doppler information to the user in a concise manner to assist in decision making.
The invention content is as follows:
the invention aims to provide a coherent marine radar which can distinguish two types of targets, namely a moving target and a static target, adopt different processing modes and display additionally acquired target Doppler information to a user in a concise mode to assist navigation decision.
The purpose of the invention is realized by the following technical scheme.
A coherent marine radar target enhancement technology based on Doppler processing is characterized in that a coherent receiver is used as a basis, a reasonable signal processing flow is designed, Doppler processing is carried out by adopting a sliding window FFT method on the premise of not changing the working mode of the conventional marine radar including the antenna rotating speed and the pulse repetition frequency, a distance-Doppler two-dimensional graph is formed when data of each pulse arrives, and ship motion compensation is carried out to enable a static target to be located in a zero Doppler channel; then, estimating clutter characteristics by using a neighboring sector, carrying out self-adaptive clutter suppression, and respectively extracting and storing a static target and a moving target according to Doppler characteristics; finally, respectively adjusting and comprehensively displaying the echo images of the static and moving targets by using double-threshold detection and an overlapped double-color image; the signal processing flow specifically comprises the steps that radar radio frequency echo signals enter a coherent receiver after being received by an antenna, the radar radio frequency echo signals are amplified, down-converted and filtered by the coherent receiver to form intermediate frequency signals, the intermediate frequency signals are converted into digital signals through AD (analog-to-digital) and stored in a data cache region after being subjected to distance dimension processing including matched filtering; the buffer area stores a series of coherent pulse data including current pulse data for coherent processing, a group of Doppler filters are formed in each range gate, and a range-Doppler image is generated; then, a zero Doppler channel is corrected through the ship motion compensation module, and the clutter suppression module suppresses dynamic clutter such as sea clutter and rain clutter; and then extracting moving and static targets on the processed range-Doppler image, and respectively finishing the processing and fusion display of the moving and static targets on the comprehensive display module.
The invention can make the moving and static targets obtain N times of coherent accumulation benefit (the improvement of non-coherent accumulation is similar to that of the non-coherent accumulationThe target detection capability under the sea clutter condition is greatly improved through clutter automatic suppression, the high-threat moving target is highlighted, and the superior performance of the coherent marine radar is fully exerted.
The method comprises the steps of carrying out mechanical circular scanning on the existing marine radar antenna at a fixed rotating speed, utilizing a coherent receiver, designing a reasonable signal processing flow, extracting target Doppler characteristics, achieving the purposes of suppressing clutter, improving small target observation performance and the like, and realizing the enhancement and the highlighting of targets on an operator interface by respectively carrying out independent processing and fusion display on moving targets and static targets.
According to the design idea, the coherent system marine radar can obtain higher signal accumulation gain and clutter suppression capability than the traditional non-coherent system, and the Doppler characteristic is utilized to realize the enhanced display of the target on an operator interface, so that the superior performance of the coherent system marine radar is fully exerted.
In the preferred scheme, the echo data of each pulse of the marine radar is stored in a data cache module after being subjected to distance dimension processing including matched filtering. The data buffer module stores echo data of N pulses in total, when the echo data of each pulse arrives, the data buffer module firstly updates the stored data in a first-in first-out mode, then rearranges and outputs the data, and packs and outputs the data corresponding to the same distance unit in the N pulses according to the sequence of the distance unit from near to far.
In the preferred scheme, the ship motion compensation module calculates the Doppler channel where the static target is located by utilizing the ship course, the speed and the radar beam direction, and compensates in the distance-Doppler image.
In the preferred scheme, a Doppler filter bank is used for realizing coherent accumulation of data output by a data cache module and generating a distance-Doppler image; the filter bank first weights the data (e.g., Hanning window) to reduce side lobes, then calculates the filter output for each Doppler channel using Fast Fourier Transform (FFT), and then performs linear detection
In the preferred scheme, the clutter suppression module estimates the energy distribution characteristics of clutter in the distance and Doppler dimensions by using the adjacent sectors and performs adaptive suppression, so that a target is convenient to observe.
In the preferred scheme, a target extraction module detects the range-Doppler image after the ship motion compensation and clutter suppression, traverses each range unit and extracts a zero Doppler channel signal as a static target; and extracting a maximum value signal on a non-zero Doppler channel as a moving target.
In the preferred scheme, the moving and static target information acquired by the target extraction module is processed and displayed in a comprehensive display mode. By setting independent adjustable detection threshold values for the moving target and the static target, the observation of the small target moving at high speed is not influenced while strong terrestrial echo is inhibited; and the moving target is highlighted on the radar interface in a target color separation display mode.
The invention has the beneficial effects that:
1. compensating the frequency shift caused by the relative radial velocity of the ship and the stationary target, so that the Doppler frequency shift detection of the moving target can be regarded as that the ship is relatively stationary and used as a reference system;
2. the Doppler filter bank is used for realizing coherent accumulation of data output by the data cache module and generating a distance-Doppler image;
3. a clutter suppression module is arranged to suppress dynamic clutter such as sea clutter and rain clutter, and the effect of suppressing the dynamic clutter is improved;
4. the target extraction module extracts a zero Doppler channel signal as a static target; extracting a maximum value signal on a non-zero Doppler channel as a moving target to achieve a clear Jingwei distinguishing effect;
5. setting independent adjustable detection threshold values for the moving target and the static target, and adopting a target color separation display mode to highlight the moving target on a radar interface;
6. the existing marine radar antenna is utilized to carry out mechanical circumference scanning device at a fixed rotating speed, so that the device can be quickly transformed and upgraded and has low transformation cost.
Description of the drawings:
FIG. 1 is a block diagram of a coherent marine radar target enhancement algorithm based on Doppler processing according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of an algorithm data structure;
FIG. 3 is a schematic diagram of relative velocity calculations;
FIG. 4 is a "range-Doppler" graph;
FIG. 5 is a schematic representation of a clutter suppression curve;
FIG. 6 is a schematic diagram showing comparison of clutter suppression effect;
FIG. 7 is a schematic view of a target extraction flow;
FIG. 8 is a schematic view of an integrated display process flow;
FIG. 9 is a schematic diagram of the final display effect;
fig. 10 is a schematic view showing the effect of the whole moving object.
In the figure, a
The specific implementation mode is as follows:
the embodiments of the present invention will be described in detail below with reference to the accompanying drawings: the present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiments.
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