CN107607943B - Height measurement method of delay Doppler radar altimeter based on interference phase assistance - Google Patents
Height measurement method of delay Doppler radar altimeter based on interference phase assistance Download PDFInfo
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Abstract
The invention discloses a delay Doppler radar altimeter height measurement method based on interference phase assistance, which solves the problems that the traditional algorithm is low in precision and resolution, and a double-antenna system is difficult to extract angle information of a ground unit due to the fact that positive and negative interference phases are subjected to incoherent superposition. The implementation steps are as follows: establishing a signal model of a delay Doppler radar altimeter based on interference phase assistance; echo signal processing: noise power estimation and detection threshold calculation; defining an interference window; extracting an interference phase angle, namely an included angle of the ground unit relative to the normal line of the antenna array; and (4) height calculation, namely estimating the height of the carrier according to the corresponding distances of all the distance units in the interference window and the included angles of the corresponding ground units relative to the normal line of the antenna array. The method effectively extracts the angle information of the ground unit through the three antennas, obviously improves the height measurement precision and the resolution of the radar altimeter, is stable and reliable, has low computation amount, and is used for the terrain matching of the interference Doppler radar altimeter.
Description
Technical Field
The invention belongs to the technical field of radars, and particularly relates to a height measurement method of a radar altimeter, in particular to a height measurement method of a delay Doppler radar altimeter based on interference phase assistance, which can be used for the height measurement of the radar altimeter based on terrain matching.
Background
When traditional radar altimeter is applied to terrain matching navigation, its main influence to terrain matching performance lies in: conventional radar altimeters have large ground footprints and the measured height is the average of the heights of all the grounds within the entire ground footprint (pulse limited or beam limited). Therefore, the traditional radar altimeter has low height measurement precision and ground resolution. This results in that a high positioning accuracy cannot be obtained in the matching positioning. However, the interference delay doppler radar altimeter system developed in the united states is only a dual-antenna system, and since echoes of equidistant ground units on the left and right sides of the flight path are overlapped in a distance unit, the dual-antenna system faces the problem of incoherent superposition of positive and negative interference phases, it is difficult to effectively extract angle information of the ground units, position information of the equidistant ground units on the left and right sides of the flight path cannot be distinguished, and the resolution of the vertical course of the radar altimeter cannot be improved.
Disclosure of Invention
The invention aims to provide a height measurement method with higher precision based on an interference phase assisted delay Doppler radar altimeter aiming at the problems of the method, so as to obtain the phases of the echoes of other ground units and improve the height measurement precision and resolution.
The invention relates to a delay Doppler radar altimeter height measurement method based on interference phase assistance, which is characterized by comprising the following steps based on a three-antenna system:
(1) establishing a radar altimeter echo signal model of a three-antenna system: the antenna of the interference delay Doppler radar altimeter is composed of 3 antennas distributed in a vertical track, the distance (the length of a base line) between the antennas is d, a pulse signal is transmitted to the ground through the antenna 1, the antennas 1, 2 and 3 all receive echoes from the ground, and the established echo signal models are s1(t)、s2(t) and s3(t), which are both time-dependent echo signals;
the processing of the echo signals is started and,
(2) determining a detection threshold: calculating the noise power of any one antenna to be used for calculating the detection threshold of the radar echo signal;
(3) an interference window is defined for the antenna 1: searching a peak point position higher than the detection threshold in the echo signal of the antenna 1 according to the detection threshold obtained by calculation, starting from a peak point position distance unit, searching to the front edge of the echo, dividing all distance units with signal amplitude values higher than the detection threshold into an interference window, and stopping searching when a distance unit with signal amplitude smaller than the detection threshold appears; all distance units, namely interference points, in the interference window can be used for radar height measurement;
(4) the interference windows of the antenna 2 and the antenna 3 are defined by taking the distance unit in the interference window of the antenna 1 as a standard;
(5) extraction of interference phase angle θ (n): calculating an included angle theta (n) of the corresponding ground unit relative to the normal line of the antenna 1 array by using the echo signal of the nth distance unit in the interference window of the three antennas;
(6) radar height measurement: and calculating the height of the radar according to the distances R from the ground units corresponding to all the distance units in the interference window to the radar and the included angles theta (n) between the ground units corresponding to the distance units and the array normal of the antenna 1, and then averaging all the calculated heights of the radar to obtain the height of the radar relative to the ground.
The invention adopts a three-antenna system, solves the problem that a double-antenna system faces incoherent superposition of positive and negative interference phases, improves the angle measurement precision and further improves the measurement precision and the resolution.
Compared with the prior art, the invention has the following advantages:
1. the invention utilizes the transverse angle measurement capability of the receiving antenna array to measure the included angle of the ground unit relative to the normal line of the antenna array, thereby improving the height measurement precision;
2. because the three-antenna system is adopted, the problem that a double-antenna system faces incoherent superposition of positive and negative interference phases is solved, the angle measurement precision is improved, and the measurement precision and the resolution ratio are further improved;
3. compared with the traditional height measurement algorithm, the calculation amount is reduced;
drawings
FIG. 1 is a flow chart of an implementation of the present invention;
FIG. 2 is a diagram illustrating an arbitrary channel scenario in a three-antenna system according to the present invention;
FIG. 3 is a geometric relationship diagram of an interferometric delay Doppler altimeter;
FIG. 4 is a schematic of an interferometric phase assisted height estimation geometry;
FIG. 5 is a schematic illustration of an interference window delineation;
FIG. 6 is a graph of 1000m height simulation results;
FIG. 7 is a graph of 3000m height simulation results;
FIG. 8 is a graph of 6000m height simulation results;
Detailed Description
Example 1
In the conventional double-antenna interference delay Doppler radar altimeter system, because echoes of equidistant ground units on the left side and the right side of a flight path are overlapped in a distance unit, the double-antenna system faces the problem of incoherent superposition of positive interference phases and negative interference phases, the angle information of the ground units is difficult to effectively extract, the position information of the equidistant ground units on the left side and the right side of the flight path cannot be distinguished, and the vertical course resolution of the radar altimeter cannot be improved.
In addition, the traditional height measurement algorithm such as a half-power point method, a WSG method, a minimum mean square error fitting height estimation method and the like has low precision and large computation amount.
In view of the current situation, the present invention develops research and study, and provides a method for height measurement of a delay doppler radar altimeter based on interference phase assistance, referring to fig. 1, the present invention is based on a three-antenna system, wherein an antenna 1 is used for transmitting and receiving signals, and an antenna 2 and an antenna 3 are used for receiving signals, and taking a zero doppler frequency channel as an example, the method includes the following steps:
(1) establishing a radar altimeter echo signal model of a three-antenna system: the antenna of the interference delay Doppler radar altimeter is composed of 3 antennas distributed in a vertical track mode, and the distance between the antennasThat is, the length of the base line is d, the antenna 1 transmits pulse signals to the ground, the antennas 1, 2 and 3 all receive echoes from the ground, and the established echo signal models are s1(t)、s2(t) and s3(t), which are both time dependent echo signals.
The processing of the echo signals is started and,
(2) determining a detection threshold: and calculating the noise power of any one antenna to be used for calculating the detection threshold of the radar echo signal.
In order to define the detection threshold, it is necessary to calculate the noise power according to the output signal of the antenna 1, or the antenna 2, or the antenna 3, in this example, the output signal of the antenna 1 is selected to calculate the noise power, and then the detection threshold is determined according to the noise power.
(3) An interference window is defined for the antenna 1: according to the calculated detection threshold, searching the echo signal of the antenna 1 for a peak point position higher than the detection threshold, where the distance unit corresponding to the peak point is one edge of the interference window, referring to fig. 5, starting from the peak point position distance unit, searching toward the front edge of the echo, dividing all distance units with signal amplitude values higher than the detection threshold into the interference window, and stopping the search when a distance unit with signal amplitude smaller than the detection threshold appears, where the distance unit is the other edge of the interference window. All distance elements, i.e. interference points, within the interference window can be used for radar height measurement.
(4) The interference windows of the antennas 2 and 3 are each defined by the distance elements within the interference window of the antenna 1.
(5) Extraction of interference phase angle θ (n): and calculating the included angle theta (n) of the corresponding ground unit relative to the normal line of the antenna 1 array by using the echo signals of the nth distance unit in the interference windows of the three antennas. n belongs to a distance element within the interference window. In order to extract the interference phase angle, the invention reconstructs a new signal, namely the sum of the signals received by the antenna 2 and the antenna 3, thereby greatly reducing the operation amount and simultaneously improving the angle measurement precision.
(6) Radar height measurement: and calculating the height of the radar according to the distances R from the ground units corresponding to all the distance units in the interference window to the radar and the included angles theta (n) between the ground units corresponding to the distance units and the array normal of the antenna 1, and then averaging all the calculated heights of the radar to obtain the height of the radar relative to the ground.
The traditional radar altimeter has low measurement precision and resolution, and the double-antenna interference delay Doppler radar altimeter has the problem of incoherent superposition of positive and negative interference phases, so that the angle information of a ground unit is difficult to effectively extract.
The interference delay Doppler radar altimeter based on the three antennas solves the problem that a dual-antenna system cannot effectively acquire the angle information of the aliasing ground unit, can effectively acquire the angle information of the ground unit, and better improves the measurement precision and the spatial resolution of the radar altimeter. And measuring the included angle of the ground unit relative to the normal line of the antenna array by using the transverse angle measurement capability of the receiving antenna array.
Example 2
The interference phase assistance-based height measurement method for the altimeter of the delay doppler radar is the same as that in the embodiment 1, and in the step (1) of the invention, an echo signal model of the altimeter of the delay doppler radar based on the interference phase assistance is established:
referring to fig. 2, fig. 2 is a schematic diagram of an arbitrary channel scene in three antennas, three antennas with the same interval are arranged along the vertical heading direction, the antenna 1 transmits and receives signals, the antennas 2 and 3 are used for receiving signals,
echo signal model of antenna 1:
echo signal model of antenna 2:
echo signal model of antenna 3:
where c is the speed of light, λ is the wavelength, LPFor propagation attenuation, H is the carrier height, G (ρ, φ) is the polar coordinate ρ, φ corresponds to the antenna gain of the ground unit, σ (ρ, φ) is the polar coordinate ρ, φ corresponds to the ground unit area scattering coefficient, Pp(t) is the point target echo waveform, R1(rho, phi) is the distance from the antenna 1 to the ground unit corresponding to the polar coordinate rho and phi, d is the length of the base line, theta (rho, phi) is the polar coordinate rho, and the included angle between the ground unit corresponding to phi and the normal of the antenna 1.
The radar altimeter has the capability of transversely measuring angles by adopting a three-antenna system, and the radar altitude is calculated by measuring the included angle between the ground unit and the normal line of the antenna array. The calculation amount is greatly reduced due to the construction of a new signal, and the spatial resolution of the radar altimeter is improved due to the adoption of the Doppler sharpening technology during signal processing.
The invention utilizes the transverse angle measurement capability of the receiving antenna array to measure the included angle of the ground unit relative to the normal line of the antenna array, thereby improving the height measurement precision.
Example 3
The method for measuring height of the altimeter of the delay Doppler radar based on interference phase assistance is the same as the method for calculating the noise power of any antenna in the embodiment 1 and the step 2, wherein the noise power of the antenna 1 is used in the embodiment
For example, the following steps are carried out:
where N1 is the noise window starting distance unit number, M is the length of the noise window, s1Is the received signal of the antenna 1, l is the serial number of the distance unit in the noise window;
determining the threshold U of the subsequent detection according to the detection probabilityT：
In the formula PfaIs the detection probability.
Although the noise power is calculated by using the output signal of the antenna 1 in this example, in actual operation, the noise power may be calculated by using the output signal of the antenna 2 or the antenna 3, the calculation formula is the same as that of the antenna 1, and the noise power calculated by using the antenna 2 or the antenna 3 may also be used to calculate the detection threshold.
Example 4
The interference phase assistance-based height measurement method of the altimeter of the delay doppler radar is the same as that of the embodiment 1-3, wherein the extraction of the interference phase angle in the step (5) is carried out according to the following method:
(5.1) output ground echo signals of the antennas 1, 2 and 3 in the interference window are respectively recorded as:
s1(N2-P+1),s1(N2-P+2),…,s1(N2)；
s2(N2-P+1),s2(N2-P+2),…,s2(N2)；
s3(N2-P+1),s3(N2-P+2),…,s3(N2)；
where N is2The position of the peak point is shown, and P is the number of distance units in the interference window;
(5.2) nth (N ∈ [ N ]2-P+1,N2]) The angle θ (n) of the corresponding ground element of the range cell with respect to the antenna array normal is calculated by:
when extracting the interference phase angle, because the conjugate phase multiplication is adopted in the prior art, the calculation amount is large, the invention constructs a new signal, namely the sum of the echo signals of the antenna 2 and the antenna 3, and then the new signal is subjected to ratio processing with the echo signal of the antenna 1, so that the calculation amount is greatly reduced, and the angle measurement precision is also high.
Example 5
The method for height measurement of the delay doppler radar altimeter based on interference phase assistance is the same as that in the embodiment 1-4, wherein in the step (6), the distances R from the ground units corresponding to all the distance units to the radar and the included angles theta (n) between the ground units corresponding to the distance units and the array normal of the antenna 1 are calculated, and the method is carried out as follows:
averaging all the calculated radar heights to obtain the height of the radar relative to the ground:
in the formula, n is the serial number of the distance unit in the interference window, c is the speed of light, and B is the signal bandwidth.
All the distance units in the interference window can be used for calculating the height of the radar, so that the distance units in the interference window are fully utilized, and the height measurement precision is greatly improved.
Example 6
The height measurement method of the delay Doppler radar altimeter based on the interference phase assistance is the same as the embodiments 1-5,
(1) establishing an echo signal model of a delay Doppler radar altimeter based on interference phase assistance;
the processing of the echo signals is started and,
(2) calculating the noise power estimate and detection threshold of antenna 1: for subsequent detection, windowing is needed to estimate the noise power at a position far away from the front edge of the echo before the height measurement process is performed. Assume a noise window starting distance element number of N1 and a noise window length of M, s1For the received signal of antenna 1, l is the number of the distance unit in the noise window, then the noise power is:
the threshold for subsequent detection can be determined from the detection probability:
wherein P isfaIs the detection probability.
(3) Defining an interference window: the position of the peak point above the detection threshold is searched in the echo signal. Then, starting from the distance unit of the peak point position, searching towards the front edge of the echo, dividing all distance units with signal amplitude values higher than the detection threshold into an interference window, and stopping searching when the distance units with signal amplitude values smaller than the detection threshold appear.
(4) Extraction of interference phase θ (n): and calculating the included angle theta (n) of the corresponding ground unit of the nth distance unit relative to the normal line of the antenna array.
(5) Radar height measurement: estimating the height of the carrier according to the correspondence and the distance of all distance units in the interference window and the included angle of the corresponding ground unit relative to the normal line of the antenna array:
the three-antenna interference delay Doppler radar altimeter can effectively solve the problem of incoherent superposition of positive and negative interference phases in a double-antenna system, effectively extracts the angle information of the ground unit, has higher altimetry precision and lower computation amount compared with the traditional altimetry method, and improves the resolution of the vertical course of the radar altimeter.
A more complete and detailed example is provided below, which further illustrates the present invention,
example 7
The method for height measurement of the altimeter of the delay Doppler radar based on the interference phase assistance is the same as the embodiments 1-6, referring to fig. 1, and the implementation scheme of the invention comprises the following steps:
referring to FIG. 3, FIG. 3 is a geometric diagram of an interferometric delay Doppler altimeter with three equally spaced antennas positioned along the vertical heading, antenna 1 transmitting and receiving signals and antennas 2 and 3 receiving signals, assuming that the radar altimeter is used for delay Doppler altimeterThe number of pulses to be processed is N and the pulse repetition frequency is Frλ is wavelength, height of the carrier is H, speed of the carrier is vaThe base length is d, and under the assumption of flat ground, the range of the ground band corresponding to the nth Doppler channel is assumed to be yn～yn+1See the Doppler channel, y, shaded in FIG. 2nAnd yn+1Can be expressed as:
for height estimation, the best choice is to select the signal output by the Doppler channel No. N/2 (zero Doppler frequency) for processing. For the sake of no loss of generality, taking the signal output from the N/2+1 th doppler channel adjacent to the zero doppler channel as an example, referring to fig. 4, the lower shaded portion of fig. 4 is the doppler channel,
since the following approximate relationship exists near zero doppler frequency:
for the convenience of analysis, it is assumed that the ground scattering units are only distributed on the center line of the ground strip, i.e. the straight line on which point A, B in fig. 4 is located, A, B is two ground units symmetric about the flight path, and the center line coordinates corresponding to the N/2+1 th doppler channel are:
respectively carrying out down-conversion, pulse compression and delay Doppler processing on the echo received by the antenna,
echo signal model of antenna 1:
echo signal model of antenna 2:
echo signal model of antenna 3:
c is the speed of light, λ is the wavelength, LPFor propagation attenuation, H is the height of the aircraft, g (x) is the antenna gain of the ground unit corresponding to the coordinate x, σ (x) is the scattering coefficient of the ground unit area corresponding to the coordinate x, d is the length of the base line, and θ (x) is the angle between the ground unit corresponding to the coordinate x and the normal of the antenna 1. For the same scattering unit on the ground, the output signals of the antennas 2 and 3 will have two more interference phase terms than the output signal of the antenna 1: e.g. of the type-j2πdsinθ(x)/λAnd ej2πdsinθ(x)/λ. The slope distance corresponding to the ith distance unit after discrete sampling of the echo signal is assumed to be RiIf the interference phase of a certain range element of the echo signal at three antennas can be calculated, the angle θ (x) between the ground element corresponding to the range element and the antenna array can be calculated, and then the height of the radar can be calculated from the slant distance R between the antenna and the ground element and the angle θ (x) between the ground element and the antenna array:
referring to fig. 4, for two ground units a and B symmetrical about the course, whose distances to the radar altimeter are equal, their echoes will be superimposed into the same range unit. The ground units a and B are at equal angles to the antenna normal and opposite signs. Assume that the complex scattering coefficients of ground units A and B are
And
thus, its output on the three antennas can be simplified as:
to extract the interference phase, a new signal is constructed as follows:
then, ratio processing is carried out:
in this case, the interference phase angle 2 pi d sin theta (x)/lambda can be extracted, so that the included angle of the ground unit relative to the normal line of the antenna array can be estimated, and the height of the carrier can be recovered by the skew distance.
Compared with the traditional altimetry algorithm, the invention has the advantage of reduced computation amount.
Processing the echo signals, comprising the steps of:
and 2, noise power estimation and detection threshold calculation. For subsequent detection, windowing is needed to estimate the noise power far away from the leading edge of the echo before the height estimation process is performed. Assuming that the window start distance element number is N1 and the length is M, the noise power is:
the threshold for subsequent detection can be determined from the detection probability:
in the formula PfaIs the detection probability.
And step 3, referring to fig. 5, searching the position of the peak point higher than the detection threshold in the echo signal. Assume that the distance cell number at which the peak point is located is N2. Then, starting from distance cell number N2, a search is performed towards the front edge of the echo, all distance cells with signal amplitude values above the detection threshold are scribed into the interference window, and the search is stopped when a distance cell with signal amplitude values below the detection threshold is present.
And 4, extracting an interference phase angle. Referring to fig. 5, the ground echo signals output by the antennas 1, 2, and 3 in the interference window are respectively expressed as:
s1(N2-P+1),s1(N2-P+2),…,s1(N2)；s2(N2-P+1),s2(N2-P+2),…,s2(N2)；s3(N2-P+1),s3(N2-P+2),…,s3(N2) Where P is the number of range cells in the interference window, see FIG. 4, the nth (N ∈ [ N ]2-P+1,N2]) The angle of the corresponding ground element of the range cell relative to the antenna array normal is calculated by:
in fig. 4, since the ground units are symmetrical along the course, the angles a and B are equal in magnitude and opposite in sign with respect to the antenna normal, the present invention uses only the value of the phase angle.
And 5, measuring the height of the radar. Estimating the height of the carrier according to the correspondence and the distance of all distance units in the interference window and the included angle of the corresponding ground unit relative to the normal line of the antenna array:
where n is the number of the range bin, c is the speed of light, and B is the signal bandwidth.
Since the signal of the channel N/2+1 is processed in this example, there will be an additional value, ync. When taking the zero doppler frequency channel, the term is zero.
The invention can be further verified by the following simulation.
Example 8
The height measurement method of the delay Doppler radar altimeter based on the interference phase assistance is the same as the embodiments 1-7,
an experimental scene is as follows:
the simulation scenario of the present invention is shown in fig. 2, which includes: 3 antennas, namely antenna 1, antenna 2 and antenna 3; radar simulation parameters: the speed is 150m/s, the power is 2w, the antenna gain is 26dB, the frequency is 6GHz, the pulse width is 100MHz, the DBS pulse number is 16, and the base length is 0.08 m.
Experimental contents and results:
TABLE 1, 1000m Condition altitude estimation accuracy
It can be seen from table 1 that the measurement accuracy obtained by the interferometric phase-aiding method of the present invention is highest at low heights.
Example 9
The height measurement method of the delay Doppler radar altimeter based on interference phase assistance is the same as the embodiments 1-7, and the simulation conditions and the contents are the same as the embodiment 8.
TABLE 2, 3000m Condition height estimation accuracy
It can be seen from table 2 that the measurement accuracy obtained by the interferometric phase-aiding method of the present invention is highest at medium-high conditions.
Example 10
The height measurement method of the delay Doppler radar altimeter based on interference phase assistance is the same as the embodiments 1-7, and the simulation conditions and the contents are the same as the embodiment 8.
TABLE 3, 6000m Condition altitude estimation accuracy
As can be seen from table 3, the measurement accuracy obtained by the interferometric phase assist method of the present invention is the highest under high-degree conditions, but the fitting accuracy of the minimum mean square error is also improved, but the computation amount is too large.
In conclusion, the simulation results show that the precision of the phase-assisted height estimation method based on three-antenna interference is optimal at different heights, and the operand is smaller than the minimum mean square error fitting method. The accuracy of the minimum mean square error is slightly lower than that of the interference phase assist method, but the minimum mean square error is far lower than that of the WSG method and the half-power point method in the medium-high height, the operation amount is large, and the system equipment amount is less than that of the interference phase assist method because only one antenna is needed. The WSG method and the half-power point method can approach the interference phase assist method and the minimum mean square error fitting method only with accuracy under a low altitude condition.
In short, the invention discloses a delay Doppler radar altimeter height measurement method based on interference phase assistance, which mainly solves the problems that the traditional algorithm is low in height measurement precision and resolution, and a double-antenna system faces incoherent superposition of positive and negative interference phases, so that angle information of a ground unit is difficult to effectively extract. The method comprises the following implementation steps: firstly, establishing a signal model of a delay Doppler radar altimeter based on interference phase assistance; secondly, processing the echo signals, which mainly comprises the following steps: 1) calculating noise power estimation and detection threshold; 2) an interference window is defined, and all ground distance units with amplitude values higher than a detection threshold are obtained; 3) extracting interference phases to obtain an included angle theta (n) of the ground unit relative to the normal line of the antenna array; 4) and estimating the height of the carrier according to the correspondence and the distance of all the distance units in the interference window and the included angle of the corresponding ground unit relative to the normal line of the antenna array. The method can effectively solve the problem that the angle information of the ground unit is difficult to effectively extract due to the incoherent superposition of positive and negative interference phases of a double-antenna system, can obviously improve the height measurement precision of the radar altimeter and the performance of the altimeter, reduces the operation amount compared with the traditional height measurement algorithm, and is used for the terrain matching of the interference Doppler radar altimeter.
The foregoing description is only an example of the present invention and is not intended to limit the invention, so that it will be apparent to those skilled in the art that various changes and modifications in form and detail may be made therein without departing from the spirit and scope of the invention.
Claims (2)
1. A height measurement method of a delay Doppler radar altimeter based on interference phase assistance is characterized in that the method is based on a three-antenna system and comprises the following steps:
(1) establishing a radar altimeter echo signal model of a three-antenna system: the antenna of the interference delay Doppler radar altimeter is composed of 3 antennas with vertical tracks, the distance between the antennas, namely the length of a base line, is d, a pulse signal is transmitted to the ground by the antenna 1, and the antennas 1, 2,3 all receiving the echo from the ground, the built echo signal models are respectively s1(t)、s2(t) and s3(t), which are both time-dependent echo signals;
establishing an echo signal model of a delay Doppler radar altimeter based on interference phase assistance:
echo signal model of antenna 1:
echo signal model of antenna 2:
echo signal model of antenna 3:
where c is the speed of light, λ is the wavelength, LPFor propagation attenuation, H is the carrier height, G (ρ, φ) is the polar coordinate ρ, φ corresponds to the antenna gain of the ground unit, σ (ρ, φ) is the polar coordinate ρ, φ corresponds to the ground unit area scattering coefficient, Pp(t) is the point target echo waveform, R1(rho, phi) is the distance from the antenna 1 to the polar coordinate rho, the ground unit corresponding to phi, d is the length of the base line, theta (rho, phi) is the polar coordinate rho, and the included angle between the ground unit corresponding to phi and the normal of the antenna 1;
the processing of the echo signals is started and,
(2) determining a detection threshold: calculating the noise power of any one antenna to be used for calculating the detection threshold of the radar echo signal;
(3) an interference window is defined for the antenna 1: searching a peak point position higher than the detection threshold in the echo signal of the antenna 1 according to the detection threshold obtained by calculation, starting from a peak point position distance unit, searching to the front edge of the echo, dividing all distance units with signal amplitude values higher than the detection threshold into an interference window, stopping searching when the distance units with signal amplitude smaller than the detection threshold appear, and using all distance units, namely interference points, in the interference window for radar height measurement;
(4) the interference windows of the antenna 2 and the antenna 3 are defined by taking the distance unit in the interference window of the antenna 1 as a standard;
(5) extraction of interference phase angle θ (n): calculating an included angle theta (n) of the corresponding ground unit relative to the normal line of the antenna 1 array by using the echo signal of the nth distance unit in the interference window of the three antennas; the extraction of the interference phase angle is carried out according to the following method:
(5.1) output ground echo signals of the antennas 1, 2 and 3 in the interference window are respectively recorded as:
s1(N2-P+1),s1(N2-P+2),…,s1(N2)；
s2(N2-P+1),s2(N2-P+2),…,s2(N2)；
s3(N2-P+1),s3(N2-P+2),…,s3(N2)，
where N is2The position of the peak point is shown, and P is the number of distance units in the interference window;
(5.2) angle θ (N) of corresponding ground element of nth range element with respect to antenna array normal, where N ∈ [ N2-P+1,N2]The angle θ (n) is calculated by:
(6) radar height measurement: calculating the height of the radar according to the distance R from the ground unit corresponding to all the distance units in the interference window to the radar and the included angle theta (n) between the ground unit corresponding to the distance unit and the array normal of the antenna 1,
calculating the radar height according to the following method:
averaging all the calculated radar heights to obtain the height of the radar relative to the ground:
in the formula, n is the serial number of the distance unit in the interference window, c is the light speed, and B is the signal bandwidth;
and then averaging all the calculated radar heights to obtain the height of the radar relative to the ground.
2. The method for height measurement by using the altimeter of the interferometric phase-assisted delay-Doppler radar according to claim 1, wherein the noise power of the antenna 1 is calculated from the noise power of any one of the antennas in the step (2)
Where N1 is the noise window starting distance unit number, M is the length of the noise window, s1Is the received signal of the antenna 1, l is the serial number of the distance unit in the noise window;
determining the threshold U of the subsequent detection according to the detection probabilityT：
In the formula PfaIs the detection probability.
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| CN112558055B (en) * | 2020-11-13 | 2023-11-17 | 中国电子科技集团公司电子科学研究院 | Target positioning method, target positioning device, GMTI system and readable storage medium |
| CN112558497B (en) * | 2020-12-01 | 2022-06-10 | 中国人民解放军火箭军工程大学 | Anti-interference digital simulation method and system for radar altimeter |
| CN113093187B (en) * | 2021-03-31 | 2023-07-21 | 中国人民解放军国防科技大学 | Road information-assisted CSAR ground moving target tracking method |
| CN114609633B (en) * | 2022-03-17 | 2023-09-01 | 电子科技大学 | SAR height measurement method by circumferential beam focusing mode interference |
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