CN108828580A - The two-way interference delay doppler altimeter landform spy of four antennas shows independent positioning method - Google Patents
The two-way interference delay doppler altimeter landform spy of four antennas shows independent positioning method Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- 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
- G01S13/06—Systems determining position data of a target
- G01S13/42—Simultaneous measurement of distance and other co-ordinates
Abstract
The invention discloses a kind of four antennas, two-way interference delay doppler altimeter landform spy shows independent positioning method, mainly solves the problems, such as that existing method altimetry precision and ground resolution are lower.Implementation step is：1) echo signal model of the two-way interference delay doppler altimeter of four antennas is established；2) echo-signal noise power and detection threshold are calculated；3) interference window delimited, the surface units that all amplitudes are higher than detection threshold are obtained；4) special aobvious point is chosen, the surface units of not aliasing are selected；5) extract interferometric phase, obtain surface units relative to the angle of aerial array normal and its with the angle in course；6) its three-dimensional coordinate is estimated relative to the angle of aerial array normal and its angle at the center in place Doppler channel and course according to aobvious point special in interference window.The present invention improves the altimetry precision and resolution ratio of radar altimeter, and the three-dimensional coordinate information provided is accurate, positioning when can use terrain match to target.
Description
Technical field
The present invention relates to Radar Technology field, in particular to a kind of two-way interference of four antennas postpones doppler altimeter landform
The aobvious independent positioning method of spy, positioning when can be used for terrain match to target.
Background technique
The main purposes of radar altimeter first is that be used for terrain match.And the altimetry precision and ground of conventional radar altimeter
Face resolution ratio is all lower, is unable to get higher positioning accuracy.
The airborne dual-antenna interference delay Doppler radar altimeter system of American R & D, is equipped with two vertical course lines point
The antenna of cloth also adds interference angle measurement ability except the ability of delay doppler processing.Since interferometric phase and ground dissipate
The angle that wave is emitted back towards relative to beauty's battle array is related, will be for Height Estimation of the raising based on echo frontier using interferometric phase information
Precision provides additional supplementary means.But the interference of American R & D delay Doppler radar altimeter system is only double antenna
System, since the echo-signal of the equidistant surface units at left and right sides of course line will overlap in a distance unit, this
Kind dual-antenna system is difficult to effectively extract the angle information of surface units, and the equidistant surface units at left and right sides of course line cannot be distinguished
Location information, and then influence radar altimeter perpendicular on the direction of course resolution ratio improve, cause matching position essence
It spends low, the matched demand of landform cannot be met.
Summary of the invention
It is an object of the invention in view of the above shortcomings of the prior art, propose that how general a kind of two-way interference delay of four antennas is
It strangles altimeter landform spy and shows independent positioning method, to improve the altimetry precision of radar altimeter and along the resolution ratio in course, Jin Erman
The demand of sufficient terrain match improves positioning accuracy when terrain match.
To achieve the above object, technical solution of the present invention includes as follows：
(1) signal model for establishing the two-way interference delay doppler altimeter of four antennas, i.e., first will be perpendicular to track direction
Three antennas equidistantly arrange, the spacing between antenna be da, then set up in the track negative side perpendicular to intermediate antenna
4th antenna, the 4th antenna are d with the distance between the intermediate antenna first placedc, the height on this four antenna distance ground
Degree is H meters, H>100, da>0, dc>0；
(2) signal, four days are emitted by the antenna perpendicular to the centre inside three antennas arranged on track direction
Line while receives echo-signal；
(3) to the noise power in echo-signalEstimated, and according to noise powerWith detection probability PfaIt calculates
Detection threshold UT；
(4) search is higher than detection threshold U in echo-signalTPeak point, since the distance unit of peak point position,
To echo frontier and rear edge search, it is less than detection threshold U when there is signal amplitudeTDistance unit when stop search, then draw
Surely interfere window, which includes that all signal amplitude values are higher than detection threshold UTDistance unit；
(5) selection that special aobvious point is carried out in interference window, that is, select the surface units of not aliasing；
(6) corresponding n-th of the distance unit of center Doppler frequency in m Doppler channel is calculated by interference processing
Corresponding surface units are corresponding with the center Doppler frequency in m Doppler channel relative to the angle δ (m, n) in track direction
Angle theta (m, n) of the corresponding surface units of n-th of distance unit relative to aerial array normal：
δ (m, n)=arcsin { λ [angle (s4(m,n)·s1(m,n)*)]/2·2πdc,
θ (m, n)=arcsin { λ [angle (s3(m,n)·s1(m,n)*)-angle(s2(m,n)·s1(m,n)*)]/4π
da,
Wherein, s1(m,n)*The center Doppler frequency in the m Doppler channel received for first antenna 1 is corresponding
The conjugation of the echo-signal of n-th of distance unit, s2(m, n) is the center in the m Doppler channel that the second antenna 2 receives
The echo-signal of corresponding n-th of the distance unit of Doppler frequency, s3(m, n) is the m Doppler that third antenna 3 receives
The echo-signal of corresponding n-th of the distance unit of the center Doppler frequency in channel, s4(m, n) is what the 4th antenna 4 received
The echo-signal of corresponding n-th of the distance unit of the center Doppler frequency in m Doppler channel, n ∈ [K-P, K+Q] are indicated
The position number of the distance unit of the aobvious point of all landform spies in m Doppler channel, P be interfere window forward position to peak point away from
From unit number, Q is along the distance unit number for arriving peak point after interference window, and K is distance unit serial number where peak point, λ
To emit signal wavelength；
(7) according to the aobvious point of the landform spy in interference window relative to the angle theta (m, n) of aerial array normal and its relative to boat
The angle δ (m, n) in mark direction estimates the three-dimensional coordinate parameter H of the aobvious point of landform spym,n,Xm,n,Ym,n:
Wherein, Hm,nFor m Doppler channel corresponding n-th of the distance unit of center Doppler frequency correspondingly
Difference in height of the face unit relative to carrier aircraft platform, Xm,nCenter Doppler frequency for m Doppler channel is n-th corresponding
The corresponding surface units of distance unit are upwardly deviated from the vertical course coordinate in carrier aircraft ground course line, Y in vertical course sidem,nFor
Carrier aircraft uniform rectilinear is flat fly under conditions of, corresponding n-th of the distance unit pair of the center Doppler frequency in m Doppler channel
The surface units answered in the case where being upwardly deviated from radar altimeter along course side special aobvious point along course coordinate, B is signal bandwidth, and λ is
Emit signal wavelength, N is the umber of pulse for postponing doppler processing, FrFor pulse recurrence frequency, v is carrier aircraft speed.
The present invention has the advantage that compared with prior art：
1, horizontal and vertical angle-measuring capability of the present invention since four aerial arrays are utilized, can measure ground simultaneously
Face unit is relative to angle and surface units corresponding along track direction relative to angle corresponding to path in elevation direction
Degree, and then obtain the three-dimensional coordinate of the aobvious point of the spy；
2, the present invention shows independent positioning method, solution due to using the two-way interference delay doppler altimeter landform spy of four antennas
It has determined conventional radar altimeter altimetry precision and the low problem of spatial resolution.
Detailed description of the invention
Fig. 1 is implementation flow chart of the invention；
Fig. 2 is the schematic diagram of a scenario that present invention emulation uses；
Fig. 3 is the two-way interference delay doppler altimeter geometrical relationship figure of four antennas in the present invention；
Fig. 4 is that the two-way interference delay doppler altimeter landform spy of four antennas shows point location schematic diagram in the present invention；
Fig. 5 is that the interference window in the present invention delimit schematic diagram；
Fig. 6 is the simulation result diagram with the present invention under the conditions of hypsography is larger；
Fig. 7 is the simulation result diagram with the present invention under the conditions of hypsography is smaller.
Specific embodiment
It is referring to Fig.1, of the invention that the specific implementation steps are as follows：
Step 1, the echo signal model for establishing the two-way interference delay Doppler radar altimeter of four antennas.
Referring to Fig. 3, present example shares 4 antennas, wherein first antenna 1, and the second antenna 2 and third antenna 3 are along vertical
Equivalent single course direction equidistantly arranges, and is followed successively by third antenna 3 from the negative semiaxis of x-axis to positive axis direction, first antenna 1, and second day
Line 2, the spacing between these three antennas are denoted as da, da>0, then the 4th is set up in the track negative side perpendicular to first antenna 1
Antenna 4, the distance between the 4th antenna 4 and first antenna 1 are dc, dc>0, the height on this four antenna distance ground is H meters, H>
100, A points are any one surface units on ground, and the distance of first antenna 1 to A point is R1, second antenna 2 to A point
Distance is R2, the distance of third antenna 3 to A point is R3, the distance of the 4th antenna 4 to A point is R4, aerial array normal and A
The angle of point is θ, and coordinate origin is ρ at a distance from A point, and y-axis and the angle of A point are φ, sends pulse letter by first antenna 1
Number, ground echo signal is received by first antenna, 1, second antenna 2, third antenna 3 and the 4th antenna 4 jointly；
The signal model that four antennas receive the two-way interference delay doppler altimeter of ground echo signal respectively indicates
It is as follows：
Wherein, s1It (t) is the output signal of first antenna 1, λ is wavelength, LPFor propagation attenuation, H is carrier aircraft height, and h is
The height of surface units, x, y are respectively the transverse and longitudinal coordinate for the surface units that coordinate is (x, y), TPFor echo-signal pulsewidth, G (x,
It y) is the antenna gain of coordinate (x, y) corresponding surface units, σ (x, y) is coordinate x, y corresponding ground unit area scattering system
Number, s2It (t) is the output signal of second antenna 2, daThe spacing being perpendicular between three antennas of track direction arrangement, θ
(x, y) is angle of coordinate (x, y) the corresponding surface units relative to aerial array normal, s3It (t) is the defeated of third antenna
Signal out, s4It (t) is the output signal of the 4th antenna, δ (x, y) is coordinate (x, y) corresponding surface units and track direction
Angle, dcIt is two antenna spacing on track direction.
From echo signal model as can be seen that for the same scattering unit on ground, the output of the second antenna 2
Signal has more an interferometric phase item compared to first antenna 1The output signal of third antenna 3 is compared first day
Line 1 has more an interferometric phase item：The output signal of third antenna 3 has more one compared to first antenna 1 and does
Relate to phase term：
Referring to Fig. 4, if it is possible to calculate some distance unit in echo-signal and then may be used in the interferometric phase of four antennas
To calculate angle δ of the surface units relative to the angle theta (x, y) of aerial array normal and the surface units and track direction
(x, y) can calculate the three-dimensional coordinate H, X, Y of the aobvious point of landform spy by θ (x, y) and δ (x, y), wherein H is the ground
Difference in height of the unit relative to carrier aircraft platform, X are upwardly deviated from hanging down for carrier aircraft ground course line in vertical course side for the surface units
Equivalent single course coordinate, Y are under conditions of carrier aircraft uniform rectilinear is flat winged, which is being upwardly deviated from radar altitude along course side
Special aobvious point along course coordinate under table.
Step 2 handles echo-signal.
For coordinate estimation, optimal selection is that the signal of N/2 Doppler channel output is selected to handle, more
General Le channel is the resolution cell formed after postponing doppler processing, but in order to without loss of generality and convenient for analysis, sheet
Example assumes ground scatter list by taking the signal that the m Doppler channel adjacent with N/2 Doppler channel exports as an example
Member is distributed only over corresponding to m Doppler channel on equal Doppler curves, is realized as follows：
(2a) noise powerEstimation：
It is needed before carrying out Height Estimation processing first in the place windowing estimating noise power far from echo frontierThis is made an uproar
Acoustical powerIt is calculated as follows：
Wherein, N1The starting distance unit number of window is estimated for noise, M is length；
(2b) calculates detection threshold UT：
Wherein, PfaFor be according to specific application scenarios be arranged detection probability.
(2c) delimit interference window:
Referring to Fig. 5, the specific implementation of this step is：Firstly, search is higher than the peak point of detection threshold in echo-signal
Position, it is assumed that distance unit serial number K where peak point is searched to echo frontier and rear edge respectively that is, since K distance unit
Rope is less than detection threshold U when there is signal amplitudeTDistance unit when stop search；Then interference window, the interference window packet delimited
All signal amplitude values are included higher than detection threshold UTDistance unit, it is assumed here that P be interfere window forward position to peak point distance
Unit number, Q arrive the distance unit number of peak point for edge after interference window；
(2d) chooses landform spy from interference window and shows point：
The condition that the echo-signal of the aobvious point of (2d1) building landform spy should meet：
Assuming that σAIt is the echo-signal amplitude of A point,It is the phase of the echo-signal of A point, w1It is received for first antenna
The noise signal arrived, w2For the noise signal that second antenna receives, w3It, will for the noise signal that third antenna receives
The output of first antenna 1, the second antenna 2 and third antenna 3 is reduced to：
Wherein,That is w1,w2,w3Gaussian distributed, N are the symbols of Gaussian Profile,It is
Noise power；
According to echo model, when considering that noise exists, the aobvious echo-signal put of landform spy should meet the following conditions：
(1) Amplitude Ratio criterion：
Define the average statistical of the second antenna 2 and the amplitude output signal ratio of third antenna 3And root-mean-square deviationIt is expressed as：
Wherein, SNR is signal-to-noise ratio, and SNR is unknown in practice, needs to be estimated according to echo-signal；
In view of the presence of the system non-ideal factor of various complexity in practice, it is assumed that the second antenna 2 and third antenna 3
The average statistical of the Amplitude Ratio of output signalApproximate Gaussian distributed, in this way | s3|/|s2| value just have
95.4% probability is fallen inWithin this section, accordingly, it is possible to be sentenced using Signal to Noise Ratio (SNR)
Whether the echo of the distance unit is the aobvious thresholding put of landform spy calmly；
By the Amplitude Ratio of signalReleasing amplitude criterion with the relationship of the section upper limit is：
(2) interference phase difference criterion：
By the Interference phase angle of 2 output signal of the second antennaWith the interference phase of 3 output signal of third antenna
Parallactic angleApproximate representation is：
Wherein,Due to
And w2Multiple Gauss distribution is obeyed, so the w being made of it12,w13Also Gaussian distributed, i.e.,Cause
The Interference phase angle of this 2 output signal of the second antennaWith the Interference phase angle of 3 output signal of third antennaThe sum of be：
angle(s2·s1 *)+angle(s3·s1 *)=imag (w12+w13)/σA
Due toSo the sum of two interferometric phases Gaussian distributed and its
Variance is：Therefore under noise conditions, the value of the sum of two interferometric phases has 95.4% probability to fall
Within this section [- 4/SNR, 4/SNR], the echo for determining the distance unit can be thus calculated using Signal to Noise Ratio (SNR)
It whether is the aobvious thresholding put of landform spy；
By the Interference phase angle of 2 output signal of the second antennaWith the interference phase of 3 output signal of third antenna
Parallactic angleThe sum of relationship with the section upper limit, releasing interference phase difference criterion is：
(2d2) derives criterion when practical application：
The aobvious point condition of the spy derived by (2d1) obtains corresponding for the center Doppler frequency in m Doppler channel
Two criterions of echo-signal of n-th of distance unit be：
Amplitude Ratio criterion：
Amplitude criterion：
Wherein, s1(m, n) is that the center Doppler frequency in the m Doppler channel that first antenna 1 receives is corresponding
The echo-signal of n-th of distance unit, s2(m, n) is the center Doppler in the m Doppler channel that the second antenna 2 receives
The echo-signal of corresponding n-th of the distance unit of frequency, s3(m, n) is the m Doppler channel that third antenna 3 receives
The echo-signal of corresponding n-th of the distance unit of center Doppler frequency, SNR (m) is the interference window in m Doppler channel
The average signal-to-noise ratio of interior all distance unit, SNR (m) can be calculate by the following formula：
(2d3) chooses landform spy and shows point：
Two conditions obtained according to (2d2) it is corresponding to the center Doppler frequency in m Doppler channel n-th away from
Echo-signal from unit is judged, if the echo-signal meets the Amplitude Ratio condition and interference phase difference item of (2d2) simultaneously
Part, then the echo-signal is referred to as that landform spy shows point, if not satisfied, then the echo-signal is referred to as that non-landform spy shows point；
The corresponding ground of corresponding n-th of the distance unit of center Doppler frequency in (2e) calculating m Doppler channel
Unit is relative to the angle theta (m, n) of aerial array normal and the center Doppler frequency corresponding n-th in m Doppler channel
Angle δ (m, n) of the corresponding surface units of a distance unit relative to track direction：
θ (m, n)=arcsin { λ [angle (s3(m,n)·s1(m,n)*)-angle(s2(m,n)·s1(m,n)*]/4π
da,
δ (m, n)=arcsin { λ [angle (s4(m,n)·s1(m,n)*)]/2·2πdc,
Wherein, s4(m, n) is that the center Doppler frequency in the m Doppler channel that the 4th antenna 4 receives is corresponding
The echo-signal of n-th of distance unit, n ∈ [K-P, K+Q] indicate the distance of the aobvious point of all landform spies in m Doppler channel
The position number of unit, P are the distance unit numbers for interfering window forward position to arrive peak point, and Q is after interference window along arriving peak point
Distance unit number, K are distance unit serial numbers where peak point；
The estimation of (2f) three-dimensional coordinate：
Angle according to the oblique distance R of the aobvious point of the landform spy in interference window and the aobvious point of landform spy relative to aerial array normal
θ (m, n) and its angle δ (m, n) relative to track direction estimates the three-dimensional coordinate parameter H of the aobvious point of landform spym,n,Xm,n,
Ym,n, complete the positioning of point aobvious to landform spy：
Wherein, Hm,nFor m Doppler channel corresponding n-th of the distance unit of center Doppler frequency correspondingly
Difference in height of the face unit relative to carrier aircraft platform；Xm,nCenter Doppler frequency for m Doppler channel is n-th corresponding
The corresponding surface units of distance unit are upwardly deviated from the vertical course coordinate in carrier aircraft ground course line in vertical course side；Ym,nFor
Carrier aircraft uniform rectilinear is flat fly under conditions of, corresponding n-th of the distance unit pair of the center Doppler frequency in m Doppler channel
The surface units answered in the case where being upwardly deviated from radar altimeter along course side special aobvious point along course coordinate.
The present invention can be by emulating further verifying.
1, experiment condition
Simulating scenes of the present invention are as shown in Figure 2 comprising：4 antennas；
Radar simulation parameter：Speed 250m/s, power 2w, antenna gain 26dB, frequency 6GHz, pulsewidth 50MHz, DBS arteries and veins
Rush number 128, baseline length 0.08m, carrier aircraft height 3000m.
2, experiment content and result：
High emulation is surveyed under experiment 1, big rise and fall orographic condition.
This example has selected the output in N/2 Doppler channel, makes respectively to N/2 Doppler multi-channel output signal
It is more with conventional half power points Height Estimation method, least mean-square error fitting Height Estimation method and the two-way interference delay of four antennas
General Le altimeter landform spy shows independent positioning method and handles, obtained simulation estimate result such as Fig. 6, wherein：
Fig. 6 (a) is topographic map；
Fig. 6 (b) is the obtained result for carrying out simulated measurement to Fig. 6 (a) using conventional half power points Height Estimation method
Figure；
Fig. 6 (c) is to be fitted Height Estimation method using least mean-square error to carry out the knot that simulated measurement obtains to Fig. 6 (a)
Fruit figure；
Fig. 6 (d) is to postpone doppler altimeter landform spy using the two-way interference of four antennas to show independent positioning method to Fig. 6 (a)
Carry out the result figure that simulated measurement obtains；
Estimate that root-mean-square error can more above-mentioned existing two methods and measurement essence of the invention by computed altitude
Degree, the results are shown in Table 1；
Table 1
| Algorithm | Half power points | Least mean-square error fitting | Two-way interferometry |
| Height Estimation root-mean-square error [m] | 46.6302 | 35.2037 | 0.9845 |
It can be obtained from Fig. 6 and table 1：Under big rise and fall orographic condition, the two-way interference of four antennas postpones doppler altimeter
Localization method altimetry precision and along the direction of course and the resolution ratio in vertical course direction has pole relative to conventional method
Big raising.
High emulation is surveyed under the conditions of experiment 2, the shape smaller that rises and falls.
This example has selected the output in N/2 Doppler channel, makes respectively to N/2 Doppler multi-channel output signal
It is more with conventional half power points Height Estimation method, least mean-square error fitting Height Estimation method and the two-way interference delay of four antennas
General Le altimeter landform spy shows independent positioning method and handles, obtained simulation estimate result such as Fig. 7, wherein：
Fig. 7 (a) is topographic map；
Fig. 7 (b) is the obtained result for carrying out simulated measurement to Fig. 7 (a) using conventional half power points Height Estimation method
Figure；
Fig. 7 (c) is to be fitted Height Estimation method using least mean-square error to carry out obtaining for simulated measurement to Fig. 7 (a)
Result figure；
Fig. 7 (d) is to postpone doppler altimeter landform spy using the two-way interference of four antennas to show independent positioning method to Fig. 7 (a)
Carry out the obtained result figure of simulated measurement；
Estimate that root-mean-square error can more above-mentioned existing two methods and measurement essence of the invention by computed altitude
Degree, the results are shown in Table 2：
Table 2
| Algorithm | Half power points | Least mean-square error fitting | Interferometry |
| Height Estimation root-mean-square error [m] | 5.1735 | 2.8391 | 1.902 |
It can be obtained from Fig. 7 and table 2：Under the lesser orographic condition that rises and falls, the two-way interference of four antennas postpones Doppler's height
The altimetry precision of the localization method of table and the resolution ratio along the direction of course with vertically course direction have relative to conventional method
Greatly improve.
Claims (5)
1. a kind of two-way interference delay doppler altimeter landform spy of four antennas shows independent positioning method, including：
(1) signal model for establishing the two-way interference delay doppler altimeter of four antennas, i.e., first will be perpendicular to the three of track direction
A antenna equidistantly arranges, and the spacing between antenna is da, then in the track negative side perpendicular to intermediate antenna set up the 4th
A antenna, the 4th antenna are d with the distance between the intermediate antenna first placedc, the height on this four antenna distance ground is H
Rice, H>100, da>0, dc>0；
(2) signal is emitted by the antenna perpendicular to the centre inside three antennas arranged on track direction, four antennas are same
When receives echo-signal；
(3) to the noise power in echo-signalEstimated, and according to noise powerWith detection probability PfaCalculate detection
Thresholding UT；
(4) search is higher than detection threshold U in echo-signalTPeak point, since the distance unit of peak point position, to return
Wavefront and rear edge search, are less than detection threshold U when there is signal amplitudeTDistance unit when stop search, then delimit dry
Window is related to, which includes that all signal amplitude values are higher than detection threshold UTDistance unit；
(5) selection that special aobvious point is carried out in interference window, that is, select the surface units of not aliasing；
(6) corresponding n-th of the distance unit of center Doppler frequency for calculating m Doppler channel by interference processing is corresponding
Surface units relative to the angle δ (m, n) in track direction and the center Doppler frequency in m Doppler channel corresponding
Angle theta (m, n) of the corresponding surface units of n distance unit relative to aerial array normal：
δ (m, n)=arcsin { λ [angle (s4(m,n)·s1(m,n)*)]/2·2πdc,
θ (m, n)=arcsin { λ [angle (s3(m,n)·s1(m,n)*)-angle(s2(m,n)·s1(m,n)*)]/4πda,
Wherein, s1(m,n)*The center Doppler frequency in the m Doppler channel received for first antenna 1 is n-th corresponding
The conjugation of the echo-signal of distance unit, s2(m, n) is that how general the center in the m Doppler channel that the second antenna 2 receives is
Strangle the echo-signal of corresponding n-th of the distance unit of frequency, s3(m, n) is the m Doppler channel that third antenna 3 receives
Corresponding n-th of the distance unit of center Doppler frequency echo-signal, s4(m, n) is No. m that the 4th antenna 4 receives
The echo-signal of corresponding n-th of the distance unit of the center Doppler frequency in Doppler channel, n ∈ [K-P, K+Q] indicate No. m
The position number of the distance unit of the aobvious point of all landform spies in Doppler channel, P is to interfere window forward position to the distance list of peak point
First number, Q are along the distance unit number for arriving peak point after interference window, and K is distance unit serial number where peak point, and λ is hair
Penetrate signal wavelength；
(7) according to the aobvious point of the landform spy in interference window relative to the angle theta (m, n) of aerial array normal and its relative to track side
To angle δ (m, n), estimate the three-dimensional coordinate parameter H of the aobvious point of landform spym,n,Xm,n,Ym,n:
Wherein, Hm,nIt is single for the corresponding ground of corresponding n-th of the distance unit of center Doppler frequency in m Doppler channel
Difference in height of the member relative to carrier aircraft platform, Xm,nFor corresponding n-th of the distance of center Doppler frequency in m Doppler channel
The corresponding surface units of unit are upwardly deviated from the vertical course coordinate in carrier aircraft ground course line, Y in vertical course sidem,nFor in carrier aircraft
Uniform rectilinear is flat fly under conditions of, corresponding n-th of the distance unit of the center Doppler frequency in m Doppler channel is corresponding
Surface units in the case where being upwardly deviated from radar altimeter along course side special aobvious point along course coordinate, B is signal bandwidth, and λ is transmitting
Signal wavelength, N are the umber of pulse for postponing doppler processing, FrFor pulse recurrence frequency, v is carrier aircraft speed.
2. according to the method described in claim 1, wherein the two-way interference of four antennas described in step (1) postpones Doppler's height
The signal model of table, is expressed as follows：
Wherein, s1It (t) is the output signal of first antenna 1, λ is wavelength, LPFor propagation attenuation, H is carrier aircraft height, and h is ground
The height of unit, x, y are respectively the transverse and longitudinal coordinate for the surface units that coordinate is (x, y), TPFor echo-signal pulsewidth, G (x, y) is
The antenna gain of the corresponding surface units of coordinate (x, y), σ (x, y) be coordinate x, the corresponding ground unit area scattering coefficient of y,
s2It (t) is the output signal of second antenna 2, daThe spacing being perpendicular between three antennas of track direction arrangement, s3(t)
For the output signal of third antenna, s4It (t) is the output signal of the 4th antenna, dcIt is two antennas on track direction
Spacing.
3. according to the method described in claim 1, wherein noise power in the step (3)Estimation and detection threshold UT's
It calculates, carries out as follows：
Wherein, N1It is interference window window starting distance unit number, M is the length of noise estimation window, PfaIt is according to specific
The detection probability of application scenarios setting.
4. according to the method described in claim 1, wherein selecting the ground of not aliasing single in interference window in the step (5)
Member carries out as follows：
(5a) assumes σAIt is the echo-signal amplitude of A point,It is the phase of the echo-signal of A point, w1It is received for first antenna 1
The noise signal arrived, w2For the noise signal that second antenna 2 receives, w3For the noise signal that third antenna 3 receives,
The signal model established in step (1) is reduced to：
Wherein, s1For the echo-signal that simplified first antenna receives, s2Simplified second antenna receives
Echo-signal, s3The echo-signal that simplified third antenna receives,That is w1,w2,w3It obeys
Gaussian Profile, N are the symbols of Gaussian Profile,It is noise power；
(5b) according to echo model, in the presence of considering noise, the echo signal amplitude ratio of the aobvious point of setting landform spy is sentenced
Other condition and interference phase difference criterion：
Amplitude Ratio criterion：
Interference phase difference criterion：
WhereinFor s1The conjugated signal of (m, n), SNR (m) are all distances in the interference window in m Doppler channel
The average signal-to-noise ratio of unit, P are the distance unit numbers for interfering window forward position to arrive peak point, and Q is after interference window along arriving peak point
Distance unit number, K is distance unit serial number where peak point；
(5c) judge three antennas in each distance unit output signal whether and meanwhile meet two conditions in (3b2), if
Meet, then the surface units are that landform spy shows point, and otherwise, which cannot be chosen for landform spy and show point.
5. according to the method described in claim 4, wherein in the interference window in m Doppler channel all distance unit it is flat
Equal Signal to Noise Ratio (SNR) (m), is calculate by the following formula：
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