CN111007490B - Sky wave over-the-horizon radar coordinate registration method based on buoy geographic information - Google Patents
Sky wave over-the-horizon radar coordinate registration method based on buoy geographic information Download PDFInfo
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- CN111007490B CN111007490B CN201911233450.4A CN201911233450A CN111007490B CN 111007490 B CN111007490 B CN 111007490B CN 201911233450 A CN201911233450 A CN 201911233450A CN 111007490 B CN111007490 B CN 111007490B
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- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
- G01S13/0218—Very long range radars, e.g. surface wave radar, over-the-horizon or ionospheric propagation systems
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- G—PHYSICS
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- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
- G01S13/0218—Very long range radars, e.g. surface wave radar, over-the-horizon or ionospheric propagation systems
- G01S2013/0227—OTH, Over-The-Horizon radar
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Abstract
The invention relates to a radar detection technology, in particular to a sky-wave over-the-horizon radar coordinate registration method based on buoy geographic information, which comprises the steps of receiving a detection signal returned by a buoy in an area where a target to be detected is located in open sea, and performing inversion to an ionosphere electron concentration structure model according to the received detection signal; the detection signal is a signal which returns to the short wave transmitting station after being reflected by the ionosphere reflection region, and the ionosphere reflection region is an ionosphere region which can radiate short waves to a region where a target to be detected is located; based on an ionized layer electronic concentration structure model obtained by inversion, tracking and calculating the size of a group path of an echo elevation angle and an echo azimuth angle received by a short wave transmitting station under radar working frequency by using a three-dimensional ray tracing method, and calculating the group path and the geodetic distance under different modes; and correcting the geodetic distance by using the coordinate information returned by the known high-frequency beacon. The ionosphere model constructed by the method is more accurate, and the positioning precision of the target can be further improved.
Description
Technical Field
The invention belongs to the technical field of radar detection, and particularly relates to a sky-wave over-the-horizon radar coordinate registration method based on buoy geographic information.
Background
The sky wave over-the-horizon radar observes a target by utilizing electric wave refraction in an ionized layer, but target echo time delay received by the radar represents virtual distance of the target from a radar station, namely the product of radar electric wave group time delay and light speed, so that in order to obtain the actual position of the radar target, the target group path group time delay and the ray azimuth angle need to be converted into geographic coordinates, namely, coordinates obtained by radar echo in a radar coordinate system need to be converted into the target position in the actual geographic coordinate system, and the process is called coordinate registration.
The sky wave over-the-horizon radar coordinate registration system provides support and guarantee for sky wave over-the-horizon radar target positioning, mode recognition and track connection by establishing a corresponding relation between a target echo signal and a real ground position of a target, and can be used as a functional module of a sky wave over-the-horizon radar frequency management system and combined with a radar target positioning and tracking processing system, so that the capacity and the precision of data processing of the sky wave over-the-horizon radar are improved.
At present, a coordinate registration method based on a spherical measurement model, which is published in the missile and rocket and guidance bulletin 2005, stage S5, "sky wave over-the-horizon radar coordinate registration method", hole sensitivity, king national macro and the like "is adopted for coordinate registration, but because disturbance of different modes and different degrees exists in an ionosphere, a situation that a plurality of group delays occur in one target is easily generated, and a radar cannot correctly judge a propagation mode of each echo after receiving a plurality of echoes, so that the work of coordinate registration and mode identification becomes difficult, and the registration accuracy is reduced. Therefore, the technical problem that the precision of coordinate registration of the sky-wave over-the-horizon radar is not high exists in the prior art.
Disclosure of Invention
The invention aims to provide a registration method of sky wave over-the-horizon radar coordinates based on buoy geographic information.
In order to achieve the purpose, the invention adopts the technical scheme that: a sky wave over-the-horizon radar coordinate registration method based on buoy geographic information is applied to a two-way oblique return detection system, and the system comprises: a short wave transmitting station, a buoy located in the irradiation area; the method comprises the following specific steps:
step 1, receiving a detection signal returned by a buoy in an area where an object to be detected is located in the open sea, and performing an ionosphere electron concentration structure model according to the received detection signal; the detection signal is a signal which returns to the short wave transmitting station after being reflected by the ionosphere reflection region, and the ionosphere reflection region is an ionosphere region which can radiate short waves to a region where a target to be detected is located;
and 3, correcting the geodetic distance by using the coordinate information returned by the known high-frequency beacon.
In the above sky-wave over-the-horizon radar coordinate registration method based on buoy geographic information, the implementation of step 1 includes:
step 1.1, receiving a detection signal returned by a buoy in an area where an object to be detected is located in open sea;
step 1.1.1, a short wave transmitting station radiates short waves to an ionosphere reflection area;
step 1.1.2, a receiving antenna and a transponder in communication connection with the receiving antenna are arranged on the buoy, and after the transponder receives the short wave transmitted by the short wave transmitting station, the transponder transmits a detection signal to an ionosphere so that the detection signal reaches the short wave transmitting station through reflection of the ionosphere;
step 1.2, performing an ionosphere electron concentration structure model according to the received detection signal;
step 1.2.1, receiving a signal returned by a buoy in an area where an object to be detected is located in open sea, and acquiring a vertical ionogram of an ionosphere, an oblique ionogram of an ionosphere reflection area, ionosphere historical data and forecast data;
and 1.2.2, carrying out data assimilation on signals returned by the buoy, a vertical ionogram of an ionosphere, an oblique ionogram of an ionosphere reflection region, ionosphere historical data and forecast data by using a data assimilation method, and constructing an ionosphere electron concentration structure model according to the assimilated data.
In the above sky-wave over-the-horizon radar coordinate registration method based on the buoy geographic information, the implementation of step 2 includes:
step 2.1, the three-dimensional ray tracing method is used for tracking and calculating the group path size of the echo elevation angle and the echo azimuth angle received by the short wave transmitting station under the radar working frequency, and the method comprises the following steps:
using formulas
Ray tracing is carried out on the electric wave of the radar operating frequency to obtain the group path of the echo, wherein k is the wave number of the electric waveω is the angular frequency of the electric wave, c is the speed of light in vacuum, r is the wave vector, τ is the group path of the electric wave;
step 2.2, calculating the group path and the earth distance under different modes, comprising the following steps: by means of the formula (I) and (II),
calculating the geodetic distance and the corrected group path, wherein D is the geodetic distance and ReIs the radius of the earth, integral is an indefinite integral, theta is the angle of the earth's center on the earth, P' is the group path, s is the arc length on the ray path, and
R＝Re+ z, z is the height from the ground.
In the above sky-wave over-the-horizon radar coordinate registration method based on the buoy geographic information, the implementation of step 3 includes:
3.1, calculating the distance A between the self coordinate returned by the buoy and the coordinate of the short wave transmitting station, and carrying out difference processing on the distance A between the self coordinate and the coordinate of the short wave transmitting station and the coordinate of the geodetic distance D obtained in the step 2 to obtain an error;
and 3.2, correcting the geodetic distance by using the error obtained in the step 3.1 as a correction error.
And 3.3, obtaining target multipath echo signals in the target positioning and tracking process by the radar, and performing mode distribution according to echoes of different propagation modes of the target to give final ground coordinates and flight paths of the target.
The invention has the beneficial effects that: receiving a detection signal returned by a buoy in an area where an object to be detected is located in the open sea, and constructing a more accurate ionosphere electron concentration model according to the detection signal, wherein the model is closer to the current state of an ionosphere compared with a model constructed in the prior art; meanwhile, data fusion is carried out according to the oblique return data, the vertical measurement data and the oblique measurement data, and the advantages of various methods are fully utilized, so that the constructed ionosphere model is more accurate, and the positioning precision of the target can be improved.
Drawings
Fig. 1 is a schematic flow chart of a sky-wave over-the-horizon radar coordinate registration method based on buoy geographic information according to an embodiment of the present invention;
fig. 2 is a schematic diagram of ray tracing in a sky-wave over-the-horizon radar coordinate registration method based on buoy geographic information according to an embodiment of the present invention;
fig. 3 is a schematic flow chart of coordinate correction in a sky-wave over-the-horizon radar coordinate registration method based on buoy geographic information according to an embodiment of the present invention;
FIG. 4 is a diagram illustrating a conventional PD transformation;
fig. 5 is a schematic diagram of PD transformation in an sky-wave over-the-horizon radar coordinate registration method based on buoy geographic information according to an embodiment of the present invention.
Detailed Description
Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
The embodiment provides a sky wave over-the-horizon radar coordinate registration method based on buoy geographic information, which is applied to a two-way oblique return detection system, and the system comprises: a short wave transmitting station, a buoy located within an irradiation zone, the method comprising:
1) receiving a detection signal returned by a buoy in an area where an object to be detected is located in open sea, and performing inversion on an ionosphere electronic concentration structure model according to the detection signal, wherein the signal is a signal returned to a short wave transmitting station after being reflected by an ionosphere reflection area, and the ionosphere reflection area is an ionosphere area capable of radiating short waves to the area where the object to be detected is located;
2) based on the ionosphere electron concentration structure model obtained after inversion, the three-dimensional ray tracing method is utilized to track and calculate the size of the group path of the echo elevation angle and the echo azimuth angle received by the short wave transmitting station under the radar working frequency, and the group path and the geodetic distance under different modes are calculated;
3) and correcting the geodetic distance by using the coordinate information returned by the known high-frequency beacon.
And, receiving the signal returned by the buoy in the region of the target to be detected in the open sea comprises:
1.1 short wave transmitting station radiating short wave to ionosphere reflection region
And 1.2, the buoy is provided with a receiving antenna and a transponder in communication connection with the receiving antenna, and the transponder transmits a detection signal to the ionosphere after receiving the short wave transmitted by the short wave transmitting station so that the detection signal reaches the short wave transmitting station through reflection of the ionosphere.
And, the ionospheric electron concentration structure model is inverted from the signal, including:
1.3, receiving a signal returned by a buoy in an area where an object to be detected is located in open sea, and acquiring a vertical ionogram of an ionosphere, an oblique ionogram of an ionosphere reflection area, ionosphere historical data and forecast data;
and 1.4, carrying out data assimilation on a signal returned by the buoy, a vertical ionogram of an ionosphere, an oblique ionogram of an ionosphere reflection region, ionosphere historical data and forecast data by using a data assimilation method, and constructing an ionosphere electron concentration structure model according to the assimilated data.
And, utilize three-dimensional ray tracing method to trace and calculate the group path size of echo elevation angle and echo azimuth angle that the short wave transmitting station received under radar operating frequency, including:
by means of the formula (I) and (II),
performing ray tracing on the electric wave of the radar operating frequency to obtain a group path of an echo, wherein k is the wave number of the electric wave; omega is the angular frequency of the electric wave; c is the speed of light in vacuum; r is a wave vector; τ is a group path of the radio wave.
And, calculating the group path and geodetic distance in different modes, comprising: by means of the formula (I) and (II),
calculating the geodetic distance and the corrected group path, wherein D is the geodetic distance; reIs the radius of the earth; the integral number is an indefinite integral number; theta is the geocentric angle on the ground; p' is a group path; s is the arc length on the ray path, and
and R ═ Re+ z, z is the height from the ground.
And finally, carrying out mode distribution on target multipath echo signals obtained by the radar in the target positioning and tracking process according to echoes of different propagation modes of the target, and giving a final ground coordinate and track of the target.
And the short wave transmitting station and the responder in the buoy form a complete coherent system.
Furthermore, the object to be detected is located within a circular area centered on the buoy with a radius of 200 km.
Furthermore, the buoy sends ionosphere sounding signals in a frequency sweep manner.
And when the geodetic distance is corrected by utilizing the coordinate information returned by the known high-frequency beacon, a ground coordinate reference source such as ground and sea clutter information is also included so as to improve the coordinate registration accuracy.
In specific implementation, as shown in fig. 1, a registration method of sky-wave over-the-horizon radar coordinates based on buoy geographic information is applied to a two-way slant return detection system, and the system includes: a short wave transmitting station, a buoy located within an irradiation zone, the method comprising:
s101: the short wave transmitting station receives a detection signal returned by a buoy in an area where an object to be detected is located in open sea, and an ionosphere electronic concentration structure model is inverted according to the detection signal, wherein the signal is returned to the short wave transmitting station after being reflected by an ionosphere reflection area, and the ionosphere reflection area is an ionosphere area capable of radiating short waves to the area where the object to be detected is located.
1) Vertical measurement data: the method comprises the steps of vertically emitting sweep frequency high-frequency pulse waves from the ground upwards, obtaining the change of the ionospheric virtual height along with the frequency of each frequency point by measuring the time delay of a reflection echo from the ionospheric layer to a receiver, namely, the ionospheric vertical detection, and obtaining a detection result called as a frequency height map. Ionospheric probes for vertical incidence detection are often referred to simply as verticalmeters, sometimes also called altimeters. Then, according to the frequency height diagram obtained by vertical detection, by inverting the imaginary height integral equation,
to obtain an ionospheric electron concentration profile, wherein,
hνthe virtual height detected by the vertical measuring instrument; h isγIs the actual height of the reflection of the electric wave; the integral number is an indefinite integral number; n (h) is; epsilonoIs as follows; m iseIs as follows; omega is; e is a natural base number.
2) Oblique measurement data: the ionospheric electron concentration profile is obtained by inversion according to the oblique ionogram in the ionospheric reflection region, which is disclosed in "inversion of oblique ionogram and its instability research" published in 2003 in the 06 th phase, laugh et al. The specific process can be as follows: initial ionospheric parameters are set, e.g. critical frequency fcHeight r corresponding to maximum electron concentrationm(ii) a Bottom height r of ionized layerb(ii) a Then, according to the ionospheric parameters, the transcendental equation is solved by iteration method for the three selected frequencies, and the elevation angle beta of the radio wave ray from the transmitting station to the receiving station is obtained1、β2、β3. Then, by the elevation angle beta1、β2、β3Calculating a radio wave group path, and calculating an error Δ p 'from an observed value'1、Δp′2、Δp′3. Then, Δ f is calculatedc、Δrm、ΔrbFurther, the original ionospheric parameter is corrected to fc＝fc+Δfc、rm＝rm+Δrm、rb＝rb+Δrb. Repeating the steps until the error delta p'1、Δp′2、Δp′3And if the target position is smaller than the preset target position, obtaining an ionospheric oblique map according to the obtained ionospheric parameters.
3) And oblique data return: when radio waves transmitted by the transmitting end are obliquely projected to an ionosphere, the radio waves are reflected by the ionosphere to reach the earth surface in a far place, and a scattering effect is generated due to uneven and electrical non-uniform characteristics of the earth surface, so that a part of radio wave energy returns to a transmitting point along an original incident path and is reflected by the ionosphere and received by a receiver in the same position with the transmitter. This radio wave propagation process is called sky wave backscattering propagation. The method of detection using this mechanism is called ionospheric bias return detection, also known as sky wave backscatter detection or ground backscatter detection. The method of sounding using this mechanism is called ionospheric slant-return sounding.
The embodiment can receive signals returned by the buoy in the region where the target to be detected is located in open sea; acquiring a vertical ionogram of an ionosphere, an oblique ionogram of an ionosphere reflection region, ionosphere historical data and forecast data; it should be emphasized that the above-mentioned process is the prior art, which is not described herein again, and the following description is only made on the process for acquiring the detection signal returned by the buoy in the area where the target to be detected is located, which is the ionosphere obliquely returned detection quasi-real-time data shown in fig. 1, as follows:
in order to ensure the accuracy, an object to be detected should be positioned in a circular area with the buoy as the center and the radius of 200 km; that is, the present embodiment can perform high-precision exploration only for the sea area within a 200km radius from the buoy. The short wave transmitting station and the responder in the buoy form a complete coherent system and adopt the same waveform design. The short wave transmitting station can radiate short waves to an ionosphere reflection area, the buoy is provided with a receiving antenna and a transponder in communication connection with the receiving antenna, and after the transponder receives the short waves transmitted by the short wave transmitting station, ionosphere detection signals are transmitted in a frequency sweeping mode, so that the detection signals reach the short wave transmitting station through ionosphere reflection.
The short wave transmitter receives the frequency sweep signal from the buoy, for example, after demodulating and low pass filtering the signal at one frequency, receives a signal rd(t) can be expressed as:
rd(t) is a received signal;
is an indefinite integral; h (t, τ) is a dual-time response function; τ is the relative time delay; r is detectionA range; u (t-tau) is a preset emission signal; t is the time at which the signal is transmitted.
Transmitting signal e (t) and receiving signal r of short wave transmitterd(t) performing a cross-correlation operation to obtain a cross-correlation operation result
And further the formula can be used,
a dual-time response function is calculated, wherein,
h(tc,tp) Is a double time response function; delta (t)p) Is a delta function; t is tcThe moment when the signal is transmitted out; t is tpThe time at which the signal is received.
In order to facilitate understanding of the derivation process of the calculation formula of the dual-time response function, the cross-correlation operation result is:
wherein, T0Is the correlation time; u (t-t)p) Is as follows; h (t, τ) is.
In the normal case, T0Less than the ionospheric channel's settling time, then the ionospheric channel can be considered a linear time-invariant system.
Thus, h (t, t)p)≈h(tc,tp)，h(t,tp) Is as follows.
Further, it is possible to prevent the occurrence of,
since the autocorrelation function of the modulated signal has a Dirac shape, then: cu,u(tp)＝δ(tp) Therefore, there are:
for linear time-varying systems, t is replaced by a variable tcA double time response function can be obtained. Therefore, as long as the pseudo-random sequence with good autocorrelation is adopted to modulate the transmitting carrier, each measurement can directly obtain the primary single-frequency full-path 'echo-distance function' of the ionospheric channel at a specific time t.
When a narrow-band radar is used, echo information of one frequency point can be observed on a full path only by one detection, and if a scattering function reflecting echo Doppler information or a p' -f curve graph under different detection frequencies is to be obtained, the detection can be completed by measuring on different frequency points for multiple times. For measuring the scattering function, only multiple measurements need to be completed on a single frequency point, and then fast Fourier operation is performed on the recorded channel impulse response data along a time axis. For measuring the p' -f function, each measurement is incremented or decremented by a certain step with respect to the adjacent measurement.
The distribution characteristics of the echo in time domain and frequency domain can be obtained through the ionospheric scattering function, so as to determine the time delay, multipath, Doppler shift and broadening information of the echo. The p '-f curve can be used for determining jump distance and the change of the jump distance along with time under different geophysical conditions, and can also be used for obtaining ionosphere structure information and high-frequency channel characteristic information, and the process of obtaining the ionosphere structure information and the high-frequency channel characteristic information according to the p' -f curve is the prior art.
In this embodiment, the reflected probe signal transmitted by the buoy is used as a receiving signal of the short wave transmitting station to replace a backscatter echo corresponding to the short wave signal transmitted by the short wave transmitting station; the electron density data is then read from the circuit diagram for the ramp back probe.
4) History and forecast data: the ionosphere historical data refers to historical data accumulated by observing the ionosphere, and the ionosphere forecast data refers to prediction data of the structure of the ionosphere in a set period in the future according to the ionosphere historical data, and the data are obtained by the prior art.
5) And carrying out data assimilation by utilizing a vertical ionogram of an ionosphere, an oblique ionogram of an ionosphere reflection region, ionosphere historical data and forecast data by using a data assimilation method, and constructing an ionosphere electron concentration structure model according to the assimilated data.
The electronic concentration data obtained in the previous steps can be subjected to data assimilation processing by using a variational method, a Kalman filter or a heuristic optimization algorithm.
S102: based on the ionosphere electron concentration structure model obtained after inversion, the three-dimensional ray tracing method is utilized to track and calculate the size of the group path of the echo elevation angle and the echo azimuth angle received by the short wave transmitting station under the radar working frequency, and the group path and the geodetic distance under different modes are calculated.
Fig. 2 is a schematic view of ray tracing in a sky-wave over-the-horizon radar coordinate registration method based on buoy geographic information according to this embodiment; as shown in fig. 2, a formula may be utilized,
As shown in fig. 2, the information of the group path P and the great circle distance D of each ray can be obtained by the three-dimensional ray tracing algorithm using the effect diagram of ray tracing of a certain frequency using the above formula, so that the group path information of the beacon and the target can be obtained from the ionosphere and radar detection results, and as long as the regional ionosphere is accurate enough, the more accurate great distance D corresponding to the group path P can be obtained using ray tracing. In fig. 2, the abscissa is the geodetic distance, the ordinate is the height, and the units are km.
The information may then be used, using a formula,
calculating a geodetic distance and a corrected group path, wherein,
d is the distance to the ground; reIs the radius of the earth; is-Determining an integral; theta is the geocentric angle on the ground; p' is a group path; s is the arc length on the ray path, and
R＝Re+ z, z is the height from the ground.
And calculating the group path distance and the ground path distance of the characteristic rays at a certain azimuth angle and elevation angle by using ray tracing, and calculating a conversion coefficient table and an azimuth angle calculation coefficient of a corresponding mode.
S103: and correcting the geodetic distance by using the coordinate information returned by the known high-frequency beacon.
As shown in fig. 3, the distance a between the buoy and the short wave transmitting station is calculated according to the coordinates of the buoy and the coordinates of the short wave transmitting station, and then the distance a between the buoy and the short wave transmitting station is subjected to subtraction processing with the earth distance D obtained in step S102, so as to obtain an error.
This error is then used as a correction error for correcting the geodetic distance obtained with the method of the present embodiment.
FIG. 4 is a diagram illustrating a conventional PD transformation; fig. 5 is a schematic diagram of PD transformation in an sky-wave over-the-horizon radar coordinate registration method based on buoy geographic information according to this embodiment; as shown in fig. 4 and 5, the abscissa is the earth distance (Ground Range), the ordinate is the slope distance (Slant Range), fig. 4 and 5 are schematic diagrams of single-frequency single-mode PD transform in the ionosphere background, and an "x" in fig. 5 indicates a PD transform correction value given according to the actual geographic position of the transponder on the buoy and the echo delay at the operating frequency.
When the method is applied, the detection signal returned by the buoy in the region of the target to be detected in the open sea is constructed, and a more accurate ionosphere electron concentration model is constructed according to the detection signal, so that the model is closer to the current state of the ionosphere compared with the model constructed in the prior art; meanwhile, data fusion is carried out according to the oblique return data, the vertical measurement data and the oblique measurement data, and the advantages of various methods are fully utilized, so that the constructed ionosphere model is more accurate, and the positioning precision of the target can be improved.
In addition, when the prior art performs the oblique return detection, the ionosphere state corresponding to the detection signal transmitted by the short wave transmitting station when being reflected by the ionosphere may be different from the ionosphere state corresponding to the oblique return signal when being reflected by the ionosphere, so that an error exists between the reconstructed ionosphere and the actual ionosphere.
S104: and finally, obtaining target multipath echo signals by the radar in the target positioning and tracking process, and performing mode distribution according to echoes of different propagation modes of the target to give a final ground coordinate of the target.
When the geodetic distance is corrected by utilizing the coordinate information returned by the known high-frequency beacon, ground coordinate reference sources such as ground and sea clutter information are also included, so that the coordinate registration accuracy is improved.
The embodiment also provides a sky wave over-the-horizon radar coordinate distribution system based on buoy geographic information, and the system comprises: short wave transmitting station, buoy located in irradiation area:
a short wave transmitting station configured to:
receiving signals returned by a buoy in an area where an object to be detected is located in open sea, and performing ionosphere quasi-real-time parameter and structure according to the signals, wherein the signals are signals returned to a short wave transmitting station after being reflected by an ionosphere reflection area, and the ionosphere reflection area is an ionosphere area capable of radiating short waves to the area where the object to be detected is located;
based on the real-time parameters and the structure of the ionized layer obtained after inversion, tracking and calculating the size of a group path of an echo elevation angle and an echo azimuth angle received by a short wave transmitting station under the radar working frequency by using a three-dimensional ray tracing method, and calculating the group path and the geodetic distance under different modes;
and thirdly, correcting the geodetic distance by using the coordinate information returned by the known high-frequency beacon.
When the method is applied, a detection signal returned by a buoy in an area where an object to be detected is located in open sea is received, and a more accurate ionosphere electron concentration model is established according to the detection signal, so that the model is closer to the current state of an ionosphere compared with a model established in the prior art; meanwhile, data fusion is carried out according to the oblique return data, the vertical measurement data and the oblique measurement data, and the advantages of various methods are fully utilized, so that the constructed ionosphere model is more accurate, and the positioning precision of the target can be improved.
It should be understood that parts of the specification not set forth in detail are well within the prior art.
Although specific embodiments of the present invention have been described above with reference to the accompanying drawings, it will be appreciated by those skilled in the art that these are merely illustrative and that various changes or modifications may be made to these embodiments without departing from the principles and spirit of the invention. The scope of the invention is only limited by the appended claims.
Claims (1)
1. A sky wave over-the-horizon radar coordinate registration method based on buoy geographic information is characterized in that the method is applied to a two-way oblique return detection system, and the system comprises: a short wave transmitting station, a buoy located in the irradiation area; the method uses the reflected detection signal transmitted by the buoy as the receiving signal of the short wave transmitting station to replace the backscattering echo corresponding to the short wave signal transmitted by the short wave transmitting station; then reading out electron concentration data from the ionization diagram of the ramp-back detection; the method comprises the following specific steps:
step 1, receiving a detection signal returned by a buoy in an area where an object to be detected is located in the open sea, and performing an ionosphere electron concentration structure model according to the received detection signal; the detection signal is a signal which returns to the short wave transmitting station after being reflected by the ionosphere reflection region, and the ionosphere reflection region is an ionosphere region which can radiate short waves to a region where a target to be detected is located;
the acquisition of the detection signal returned by the buoy in the area where the target to be detected is located comprises the following steps:
the target to be detected is positioned in a circular area which takes the buoy as the center and has the radius of 200 km; the short wave transmitting station and the responder in the buoy form a full coherent system and adopt the same waveform design; the short wave transmitting station radiates short waves to an ionosphere reflection area, the buoy is provided with a receiving antenna and a transponder in communication connection with the receiving antenna, and after the transponder receives the short waves transmitted by the short wave transmitting station, ionosphere detection signals are transmitted in a frequency sweeping mode to enable the detection signals to reach the short wave transmitting station through ionosphere reflection;
the short wave transmitting station receives the sweep frequency signal from the buoy, wherein a signal with a frequency is received after demodulation and low-pass filteringd(t) is expressed as:
wherein r isd(t) is a received signal;
is an indefinite integral; h (t, τ) is a dual-time response function; τ is the relative time delay; r is a detection range; u (t-tau) is a preset emission signal; t is the moment when the signal is transmitted;
transmitting signal e (t) and receiving signal r of short wave transmitting stationd(t) performing a cross-correlation operation to obtain a cross-correlation operation result
And then the formula is used for further utilizing,
calculating a double time response function, wherein h (t)c,tp) Is a double time response function; delta (t)p) Is a delta function; t is tcThe moment when the signal is transmitted out; t is tpIs the time at which the signal is received;
the result of the cross-correlation operation is:
wherein, T0Is the correlation time; t is0The stability time of the ionosphere channel is shorter than that of the ionosphere channel, and the ionosphere channel is a linear time-invariant system;
thus, h (t, t)p)≈h(tc,tp)，h(t,tp) Comprises the following steps:
further, it is possible to prevent the occurrence of,
the autocorrelation function of the modulated signal has a Dirac shape, then: cu,u(tp)＝δ(tp) (ii) a To obtain
For linear time-varying systems, t is replaced by a variable tcObtaining a double-time response function; modulating a transmitting carrier wave by using the single-frequency full-path echo-distance measuring method, and directly obtaining a single-frequency full-path echo-distance function of an ionosphere channel at a specific time t by measuring each time;
step 2, based on the ionized layer electronic concentration structure model obtained by inversion, utilizing a three-dimensional ray tracing method to track and calculate the size of a group path of an echo elevation angle and an echo azimuth angle received by a short wave transmitting station under the radar working frequency, and calculating the group path and the geodetic distance under different modes; the method comprises the following steps: inverting an ionosphere electron concentration structure model according to the received detection signal;
receiving a signal returned by a buoy in an area where an object to be detected in the open sea is located, and acquiring a vertical ionogram of an ionosphere, an oblique ionogram of an ionosphere reflection area, ionosphere historical data and forecast data;
carrying out data assimilation on signals returned by the buoy, a vertical ionogram of an ionosphere, an oblique ionogram of an ionosphere reflection region, ionosphere historical data and forecast data by using a data assimilation method, and constructing an ionosphere electronic concentration structure model according to the assimilated data;
the method for tracking and calculating the group path size of the echo elevation angle and the echo azimuth angle received by the short wave transmitting station under the radar working frequency by using the three-dimensional ray tracing method comprises the following steps:
using formulas
Performing ray tracing on the electric wave of the radar operating frequency to obtain a group path of an echo, wherein k is the wave number of the electric wave, omega is the angular frequency of the electric wave, c is the speed of light in vacuum, r is a wave vector, and tau is the group path of the electric wave;
calculating group paths and geodetic distances in different modes; by means of the formula (I) and (II),
calculating the geodetic distance and the corrected group path, wherein D is the geodetic distance and ReIs the radius of the earth, integral is an indefinite integral, theta is the angle of the earth's center on the earth, P' is the group path, s is the arc length on the ray path, and
R＝Re+ z, z is the height from the ground;
step 3, correcting the geodetic distance by using coordinate information returned by the known high-frequency beacon;
calculating the distance A between the buoy and the short wave transmitting station according to the self coordinate returned by the buoy and the coordinate of the short wave transmitting station, and performing difference processing on the distance A between the buoy and the earth distance D obtained in the step 2 to obtain an error;
correcting the ground distance by taking the obtained error as a correction error;
and (3) carrying out mode distribution on target multipath echo signals obtained by the radar in the target positioning and tracking process according to echoes of different propagation modes of the target, and giving a final ground coordinate and a final track of the target.
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