CN107976674A - The PRF systems of selection of dualbeam SAR obscured based on top optimization direction a kind of and system - Google Patents
The PRF systems of selection of dualbeam SAR obscured based on top optimization direction a kind of and system 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
- G01S13/88—Radar or analogous systems specially adapted for specific applications
- G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
- G01S13/90—Radar or analogous systems specially adapted for specific applications for mapping or imaging using synthetic aperture techniques, e.g. synthetic aperture radar [SAR] techniques
- G01S13/904—SAR modes
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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
- G01S13/88—Radar or analogous systems specially adapted for specific applications
- G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
- G01S13/90—Radar or analogous systems specially adapted for specific applications for mapping or imaging using synthetic aperture techniques, e.g. synthetic aperture radar [SAR] techniques
- G01S13/9004—SAR image acquisition techniques
- G01S13/9011—SAR image acquisition techniques with frequency domain processing of the SAR signals in azimuth
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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
- G01S13/88—Radar or analogous systems specially adapted for specific applications
- G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
- G01S13/90—Radar or analogous systems specially adapted for specific applications for mapping or imaging using synthetic aperture techniques, e.g. synthetic aperture radar [SAR] techniques
- G01S13/904—SAR modes
- G01S13/9041—Squint mode
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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
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
- G01S7/28—Details of pulse systems
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Abstract
PRF systems of selection and system the invention discloses a kind of dualbeam SAR obscured based on top optimization direction, can obtain suitable orientation Dual beamformation aperture radar (SAR) azimuth ambiguity degree computational methods by theory deduction and simulation analysis；By calculating the azimuth ambiguity degree of system under different pulse repetition (PRF), according to top optimization direction fuzziness selection principle, system PRF optimized parameters are obtained；The feasibility and correctness of this method are demonstrated by l-G simulation test.This method can effectively obtain the optimal result of key parameter PRF in the design of orientation dualbeam SAR system, it is the committed step for completing the design of orientation dualbeam SAR system, the present invention is by computer azimuth to dualbeam SAR system azimuth ambiguity degree, principle is obscured based on top optimization direction again, can effectively obtain system PRF optimized parameters.
Description
Technical field
PRF systems of selection and system the present invention relates to a kind of dualbeam SAR obscured based on top optimization direction, belong to microwave
Remotely sensed image technical field.
Background technology
Orientation Dual beamformation aperture radar (SAR) can repeatedly revisit target, possesses multi-angle observation, moves
The application models such as target detection, are one of developing direction of following SAR system.
The technical problem that orientation dualbeam SAR system is primarily present is：Orientation dualbeam SAR in system design,
The optimal value of system core parameter pulse recurrence frequency (PRF) is difficult to determine, it is necessary to successive ignition is designed, design time and
Design cost is higher.
The content of the invention
Present invention solves the technical problem that it is：In view of this, overcome the shortage of prior art, there is provided one kind is based on top optimization direction
The PRF systems of selection of fuzzy dualbeam SAR and system, by computer azimuth to dualbeam SAR system azimuth ambiguity degree, then base
Principle is obscured in top optimization direction, can effectively obtain system PRF optimized parameters.
The technical solution that the present invention solves is：A kind of PRF systems of selection of the dualbeam SAR obscured based on top optimization direction,
Step is as follows：
(1) according to orientation dualbeam SAR antenna radiation patterns, obtain azimuth ambiguity and position occur in Doppler domain, according to
There is position in Doppler domain in azimuth ambiguity, obtains the azimuth ambiguity degree of orientation dualbeam SAR；
(2) according to the azimuth ambiguity degree of the orientation dualbeam SAR of step (1), rolled over further according to sampling thheorem and frequency spectrum
Folded characteristic, formulates optimal PRF systems of selection, obtains optimal PRF, makes the azimuth ambiguity of a wave beam in dualbeam more
There is position and avoids another wave beam in general Le domain.
It is as follows to further include step (3)：
(3) orientation dualbeam SAR l-G simulation tests, the correctness of the PRF systems of selection of verification step (2) are passed through.
Position is occurred in Doppler domain according to azimuth ambiguity, obtains the azimuth ambiguity degree AASR of orientation dualbeam SAR, is walked
It is rapid as follows：
In formula, BaFor doppler bandwidth, BoffFor doppler centroid, G is antenna radiation pattern, and PRF repeats frequency for pulse
Rate, f are Doppler frequency, and i is non-zero integer.
Step (2) is according to the azimuth ambiguity degree of the orientation dualbeam SAR of step (1), further according to sampling thheorem and frequency
Folding characteristic is composed, optimal PRF systems of selection is formulated, obtains optimal PRF, make the azimuth ambiguity of a wave beam in dualbeam
There is position in Doppler domain and avoid another wave beam, step is as follows：
(2.1) according to the azimuth ambiguity degree of orientation dualbeam SAR, the center frequency difference f of two wave beams is determinedc；
(2.2) to center frequency difference 2f before and after optimal pulse recurrence frequency PRF is elected asc1/ (n+0.5) when, n is
Positive integer, obtains PRF, and another beam center can be made farthest apart from main beam, brings the aliasing of minimum, such as following formula：
fcTo be front and rear to center frequency difference
Step (2) establishes orientation dualbeam satellite-borne SAR, and optimal PRF is obtained by simulation calculation, is calculated with step (2)
Obtained optimal PRF compares, if the optimal PRF that simulation calculation obtains optimal PRF with step (2) is calculated differs certain model
In enclosing, then it is correct that optimal PRF, which is calculated, in the optimal PRF systems of selection of determination step (2) selection, otherwise, it is determined that
The optimal PRF systems of selection of step (2) selection are incorrect.
A certain range is within 10Hz.
The PRF selection systems of dualbeam SAR obscured based on top optimization direction of the present invention a kind of, including：Determining module, PRF
Selecting module；
Determining module, according to orientation dualbeam SAR antenna radiation patterns, obtains azimuth ambiguity and position occurs in Doppler domain
Put, position is occurred in Doppler domain according to azimuth ambiguity, obtain the azimuth ambiguity degree of orientation dualbeam SAR, send to PRF and select
Module；
PRF selecting modules, according to the azimuth ambiguity degree of the reception orientation dualbeam SAR received from determining module, then root
According to sampling thheorem and spectrum folding characteristic, optimal PRF systems of selection are formulated, obtain optimal PRF, make one in dualbeam
There is position in Doppler domain and avoids another wave beam in the azimuth ambiguity of a wave beam.
Authentication module is further included, authentication module is verified in PRF selecting modules by orientation dualbeam SAR l-G simulation tests
PRF systems of selection correctness.
Position is occurred in Doppler domain according to azimuth ambiguity in determining module, obtains the orientation mould of orientation dualbeam SAR
Paste degree AASR, formula are as follows：
In formula, BaFor doppler bandwidth, BoffFor doppler centroid, G is antenna radiation pattern, and PRF repeats frequency for pulse
Rate, f are Doppler frequency, and i is non-zero integer.
PRF selecting modules are according to the azimuth ambiguity degree of orientation dualbeam SAR, further according to sampling thheorem and spectrum folding
Characteristic, formulates optimal PRF systems of selection, obtains optimal PRF, makes the azimuth ambiguity of a wave beam in dualbeam how general
There is position and avoids another wave beam in Le domain, specific as follows：
PRF selecting modules determine the center frequency difference of two wave beams according to the azimuth ambiguity degree of orientation dualbeam SAR
fc；To center frequency difference 2f before and after optimal pulse recurrence frequency PRF is elected asc1/ (n+0.5) when, n is positive integer, is obtained
PRF, can make another beam center farthest apart from main beam, bring the aliasing of minimum, such as following formula：
fcTo be front and rear to center frequency difference.
The present invention compared with prior art the advantages of be：
(1) present invention has derived the azimuth ambiguity computational methods of orientation dualbeam SAR, considered Doppler with
Width, doppler centroid, antenna radiation pattern, pulse recurrence frequency, Doppler frequency, it is proposed that top optimization direction fuzziness is chosen
Criterion so that it is more accurate that top optimization direction fuzziness is chosen, and improves precision.
(2) present invention can obtain suitable orientation Dual beamformation aperture radar by theory deduction and simulation analysis
(SAR) azimuth ambiguity degree computational methods；By calculating the azimuth ambiguity degree of system under different pulse repetition (PRF), according to
Top optimization direction fuzziness selection principle, obtains system PRF optimized parameters；By l-G simulation test demonstrate the feasibility of this method with
Correctness.
(3) present invention gives optimal PRF choosing methods, with reference to various aspects according to top optimization direction fuzziness Criterion of Selecting
Factor is so as to accurately determine optimal PRF.
(4) The present invention gives the optimal PRF computational methods of orientation dualbeam SAR, rolled over according to sampling thheorem and frequency spectrum
Folded characteristic, formulates optimal PRF systems of selection, can be counted in the case where considering the azimuth ambiguity degree of orientation dualbeam SAR
Calculation obtains optimal PRF.
(5) The present invention gives the optimal PRF verification experimental verifications methods of orientation dualbeam SAR, optimal PRF can be accurately determined
Correctness.
Brief description of the drawings
Fig. 1 is the flow chart of the present invention；
Fig. 2 is dualbeam SAR operating modes geometrical relationship figure of the present invention；
Fig. 3 is dualbeam SAR operating mode timing diagrams of the present invention；
Fig. 4 is orientation dualbeam SAR Doppler frequency domain schematic diagrames of the present invention；
Fig. 5 is system AASR curves under different PRF.
Embodiment
The present invention is described in further detail with specific embodiment below in conjunction with the accompanying drawings.
PRF systems of selection and system the invention discloses a kind of dualbeam SAR obscured based on top optimization direction, Neng Goutong
Cross theory deduction and simulation analysis obtain suitable orientation Dual beamformation aperture radar (SAR) azimuth ambiguity degree calculating side
Method；By calculating the azimuth ambiguity degree of system under different pulse repetition (PRF), chosen according to top optimization direction fuzziness former
Then, system PRF optimized parameters are obtained；The feasibility and correctness of this method are demonstrated by l-G simulation test.This method can have
Effect obtains the optimal result of key parameter PRF in the design of orientation dualbeam SAR system, is to complete orientation dualbeam SAR systems
The committed step for design of uniting, the present invention by computer azimuth to dualbeam SAR system azimuth ambiguity degree, then based on top optimization direction mould
Principle is pasted, can effectively obtain system PRF optimized parameters.
The present invention realizes a kind of PRF systems of selection of the dualbeam SAR obscured based on top optimization direction, as shown in Figure 1, the party
Method comprises the following steps：
Step 101：Computer azimuth is to dualbeam SAR azimuth ambiguity degree；
Specifically, attached drawing 2 gives the geometrical relationship figure of orientation dualbeam SAR antennas, orientation dualbeam SAR antennas
It is to produce former and later two symmetrical wave beams by antenna (usually graing lobe to be produced by phased array antenna, by the first graing lobe and main lobe tune
It is whole symmetrical), same target area can be made successively to be irradiated twice.When the system is operating, main lobe and the first graing lobe are utilized
To launch at the same time and receive pulse, two paths of signals is aliasing in a reception window during reception, as shown in Figure 3, wherein, Txn-1,
Txn, Txn+1Represent (n-1)th, n-th, (n+1)th pulse of transmitting, trRepresent receiving time.It is more due to forward and backward wave beam
General Le frequency is negative for one positive one, therefore can be separated two paths of signals using the method for bandpass filtering in Doppler frequency domain, and then
It is imaged respectively.The pattern is since there are two wave beams, another wave beam received signal is equivalent to fuzzy when a wave beam is imaged
Clutter, therefore azimuth ambiguity degree (AASR) calculation of system is different from tradition SAR, it is necessary to reanalyse calculating.Orientation mould
Paste is due to caused by the impulse sampling working system of synthetic aperture radar orientation.The orientation Doppler frequency of SAR echo signal
Spectrum is formed by the round trip directional diagram weighting of antenna, and orientation is sampled using pulse recurrence frequency (PRF).So it is higher than
The Doppler signal of pulse recurrence frequency will be folded within the process bandwidth of azimuth spectrum core after over-sampling, so that
The aliasing with main signal frequency spectrum is caused, forms azimuth ambiguity.Azimuth ambiguity degree is azimuth ambiguity energy and useful signal energy
The ratio of amount.
It is imaging signal energy to intersect net region in attached drawing 4, by PRF sampling aft antenna other secondary lobes (relative to preceding
To wave beam) signal that receives of position also can aliasing enter in imaging signal, form azimuth ambiguity signal.It can be seen from the figure that
If system PRF is relatively low, the very strong blurred signal that back beam receives can also be mixed into imaging signal, and deteriorate significantly imaging performance.
The calculation formula that dualbeam SAR azimuth ambiguity degree (AASR) can be obtained by analysis is shown below：
In formula, BaFor doppler bandwidth, BoffFor doppler centroid, G is antenna radiation pattern, and PRF repeats frequency for pulse
Rate, f are Doppler frequency, and i is non-zero integer.
Step 102：According to top optimization direction fuzziness selection principle, system PRF optimized parameters are obtained；
According to the aliasing feature of frequency spectrum, it is front and rear to two groups of frequency spectrums by PRF be each on the frequency axis periodic extension, but adjacent
Forward direction frequency spectrum and the overlapping cases of backward frequency spectrum be also to be determined by PRF, if, PRF takes with forward direction frequency spectrum as reference
During value increase, it can be understood as backward frequency spectrum is along forward direction spectral roll, while the continuation cycle of two groups of frequency spectrums is with increase.When
It is front and rear to two groups of frequency spectrums be completely superposed when, aliasing can not separate completely, it is front and rear at this time to center frequency difference be PRF integral multiple；
When current backward two groups of frequency spectrum registrations are minimum, forward direction spectral centroid and adjacent two sections backward spectral centroids apart from it is equal when (
Forward direction frequency band and backward frequency band are evenly distributed on the frequency axis), it is front and rear at this time to add half to the integral multiple that center frequency difference is PRF
A PRF.Therefore, to center frequency difference 2f before and after PRF is elected ascAbout 1/ (n+0.5) when (n is positive integer), grid can be made
Valve centre distance main lobe center is farthest, brings the aliasing of minimum, is shown below.
Step 103：Pass through the feasibility and correctness of l-G simulation test verification method；
Emulated by a Spaceborne SAR System to verify above-mentioned theory.Rational Spaceborne SAR System parameter is built,
The computational methods provided by step 1 simulate system PRF during top optimization direction fuzziness, then the calculating provided by step 2
Criterion calculates system optimal PRF, compares the two result of calculations, if obtaining optimal PRF and step according to step 1 simulation calculation
The 2 optimal PRF being calculated are differed in a certain range, then the optimal PRF systems of selection that determination step 2 selects are calculated most
Excellent PRF is correct, otherwise, it is determined that the optimal PRF systems of selection that step 2 selects are incorrect.A certain range for 10Hz with
It is interior.
Below by a design example, the optimal PRF of orientation dualbeam SAR can be obtained by illustrating the method for the present invention.
One spaceborne orientation dualbeam SAR system of design is emulated to verify above-mentioned theory.Spaceborne orientation dualbeam SAR system
Parameter is as shown in the table：
1 Spaceborne SAR System simulation parameter of table
| Parameter | Value |
| Satellite orbit average height | 517km |
| Star ground relative velocity | 7462m/s |
| Centre frequency | 9.6GHz |
| The light velocity | 3.0×108m/s |
| Azimuth beam width | 0.39° |
| Dualbeam angle | 3.94° |
| PRF scopes | 4000Hz~12000Hz |
| Forward direction centre frequency | 18655Hz |
Optimal PRF is obtained by the optimal PRF selection criterions of step 2 and elects front and rear about 1/ (n+0.5) to center frequency difference as,
The optimal PRF that can then select is 10660Hz.Simulation analysis are carried out by step 1 computational methods, PRF is traveled through from 4000Hz
To 12000Hz, the AASR of system under different PRF is obtained as shown in Figure 5, abscissa is system PRF in attached drawing 5, and ordinate is
Azimuth ambiguity degree AASR.Periodically deviate and fold as can be seen that system AASR has.With the change of PRF, the first graing lobe and
Main lobe carries out relative translation, and the value height of AASR shakes.The maximum of AASR keeps stablizing in 0dB or so, it is reflected
Backward and forward direction round trip antenna radiation pattern uniformity, i.e., when main lobe and graing lobe are completely superposed, useful signal energy approximation is equal to
Fuzzy energy, it is 0dB to cause AASR.Minimum reduces with the increase of PRF, this is because backward and forward region how general
Strangling frequency spectrum can be separated by Doppler's bandpass filter, and with the increase of PRF, the fuzzy energy that anti-pleat is come in subtracts relatively
It is small, so the minimum of AASR can gradually be reduced with concussion.System obtain optimal AASR positions when PRF near 10650Hz,
It is consistent with step 2 theoretical calculation, emulation demonstrates the correctness of theory deduction.
The PRF selection systems of dualbeam SAR obscured based on top optimization direction of the present invention a kind of, including：Determining module,
PRF selecting modules；
Determining module, according to orientation dualbeam SAR antenna radiation patterns, obtains azimuth ambiguity and position occurs in Doppler domain
Put, position is occurred in Doppler domain according to azimuth ambiguity, obtain the azimuth ambiguity degree of orientation dualbeam SAR, send to PRF and select
Module；
PRF selecting modules, according to the azimuth ambiguity degree of the reception orientation dualbeam SAR received from determining module, then root
According to sampling thheorem and spectrum folding characteristic, optimal PRF systems of selection are formulated, obtain optimal PRF, make one in dualbeam
There is position in Doppler domain and avoids another wave beam in the azimuth ambiguity of a wave beam.
Authentication module is further included, authentication module is verified in PRF selecting modules by orientation dualbeam SAR l-G simulation tests
PRF systems of selection correctness.
Position is occurred in Doppler domain according to azimuth ambiguity in determining module, obtains the orientation mould of orientation dualbeam SAR
Paste degree AASR, formula are as follows：
In formula, BaFor doppler bandwidth, BoffFor doppler centroid, G is antenna radiation pattern, and PRF repeats frequency for pulse
Rate, f are Doppler frequency, and i is non-zero integer.
PRF selecting modules are according to the azimuth ambiguity degree of orientation dualbeam SAR, further according to sampling thheorem and spectrum folding
Characteristic, formulates optimal PRF systems of selection, obtains optimal PRF, makes the azimuth ambiguity of a wave beam in dualbeam how general
There is position and avoids another wave beam in Le domain, specific as follows：
PRF selecting modules determine the center frequency difference of two wave beams according to the azimuth ambiguity degree of orientation dualbeam SAR
fc；To center frequency difference 2f before and after optimal pulse recurrence frequency PRF is elected asc1/ (n+0.5) when, n is positive integer, is obtained
PRF, can make another beam center farthest apart from main beam, bring the aliasing of minimum, such as following formula：
fcTo be front and rear to center frequency difference.
Authentication module is by orientation dualbeam SAR l-G simulation tests, the correctness of the PRF systems of selection of verification step (2),
It is specific as follows：
Orientation dualbeam satellite-borne SAR is established, optimal PRF is obtained by simulation calculation, is calculated most with step (2)
Excellent PRF compares, if the optimal PRF that simulation calculation obtains optimal PRF with step (2) is calculated is differed in a certain range,
It is correct that optimal PRF, which is calculated, in the optimal PRF systems of selection of determination step (2) selection, otherwise, it is determined that step (2)
The optimal PRF systems of selection of selection are incorrect.
The present invention can obtain suitable orientation Dual beamformation aperture radar by theory deduction and simulation analysis
(SAR) azimuth ambiguity degree computational methods；By calculating the azimuth ambiguity degree of system under different pulse repetition (PRF), according to
Top optimization direction fuzziness selection principle, obtains system PRF optimized parameters；By l-G simulation test demonstrate the feasibility of this method with
Correctness.And the present invention has derived the azimuth ambiguity computational methods of orientation dualbeam SAR, considered Doppler with
Width, doppler centroid, antenna radiation pattern, pulse recurrence frequency, Doppler frequency, it is proposed that top optimization direction fuzziness is chosen
Criterion so that it is more accurate that top optimization direction fuzziness is chosen, and improves precision.
It above are only presently preferred embodiments of the present invention and institute's application technology principle.It will be appreciated by those skilled in the art that this hair
It is bright to be not limited to preferred embodiment described here, various significantly change, again can be carried out for a person skilled in the art
Adjustment and replacement are without departing from protection scope of the present invention.Therefore, although the present invention has been carried out by above example compared with
For detailed description, but the present invention is not limited only to above example, without departing from the inventive concept, can be with
Including other more equivalent embodiments, and the scope of the present invention is determined by scope of the appended claims.
Claims (10)
1. a kind of PRF systems of selection of the dualbeam SAR obscured based on top optimization direction, it is characterised in that step is as follows：
(1) according to orientation dualbeam SAR antenna radiation patterns, obtain azimuth ambiguity and position occur in Doppler domain, according to orientation
Obscure and position occur in Doppler domain, obtain the azimuth ambiguity degree of orientation dualbeam SAR；
(2) it is special further according to sampling thheorem and spectrum folding according to the azimuth ambiguity degree of the orientation dualbeam SAR of step (1)
Property, formulates optimal PRF systems of selection, obtains optimal PRF, makes the azimuth ambiguity of a wave beam in dualbeam in Doppler
There is position and avoids another wave beam in domain.
2. the PRF systems of selection of dualbeam SAR obscured based on top optimization direction according to claim 1 a kind of, its feature
It is：It is as follows to further include step (3)：
(3) orientation dualbeam SAR l-G simulation tests, the correctness of the PRF systems of selection of verification step (2) are passed through.
3. the PRF systems of selection of dualbeam SAR obscured based on top optimization direction according to claim 1 a kind of, its feature
It is：Position is occurred in Doppler domain according to azimuth ambiguity, obtains the azimuth ambiguity degree AASR of orientation dualbeam SAR, formula
It is as follows：
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In formula, BaFor doppler bandwidth, BoffFor doppler centroid, G is antenna radiation pattern, and PRF is pulse recurrence frequency, f
For Doppler frequency, i is non-zero integer.
4. the PRF systems of selection of dualbeam SAR obscured based on top optimization direction according to claim 1 a kind of, its feature
It is：Step (2) is rolled over according to the azimuth ambiguity degree of the orientation dualbeam SAR of step (1) further according to sampling thheorem and frequency spectrum
Folded characteristic, formulates optimal PRF systems of selection, obtains optimal PRF, makes the azimuth ambiguity of a wave beam in dualbeam more
There is position and avoids another wave beam in general Le domain, and step is as follows：
(2.1) according to the azimuth ambiguity degree of orientation dualbeam SAR, the center frequency difference f of two wave beams is determinedc；
(2.2) to center frequency difference 2f before and after optimal pulse recurrence frequency PRF is elected asc1/ (n+0.5) when, n is just whole
Number, obtains PRF, another beam center can be made farthest apart from main beam, brings the aliasing of minimum, such as following formula：
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fcTo be front and rear to center frequency difference.
5. the PRF systems of selection of dualbeam SAR obscured based on top optimization direction according to claim 2 a kind of, its feature
It is：Step (3) passes through orientation dualbeam SAR l-G simulation tests, the correctness of the PRF systems of selection of verification step (2), step
It is as follows：
Orientation dualbeam satellite-borne SAR is established, optimal PRF is obtained by simulation calculation, is calculated with step (2) optimal
PRF compares, if the optimal PRF that simulation calculation obtains optimal PRF with step (2) is calculated is differed in a certain range, sentences
It is correct to determine the optimal PRF systems of selection that step (2) selects optimal PRF is calculated, otherwise, it is determined that step (2) is selected
The optimal PRF systems of selection selected are incorrect.
6. the PRF systems of selection of dualbeam SAR obscured based on top optimization direction according to claim 5 a kind of, its feature
It is：A certain range is within 10Hz.
A kind of 7. PRF selection systems of dualbeam SAR obscured based on top optimization direction, it is characterised in that including：Determining module,
PRF selecting modules；
Determining module, according to orientation dualbeam SAR antenna radiation patterns, obtains azimuth ambiguity and position, root occurs in Doppler domain
There is position in Doppler domain according to azimuth ambiguity, obtain the azimuth ambiguity degree of orientation dualbeam SAR, send to PRF selecting modules；
PRF selecting modules, according to the azimuth ambiguity degree of the reception orientation dualbeam SAR received from determining module, further according to adopting
Sample theorem and spectrum folding characteristic, formulate optimal PRF systems of selection, obtain optimal PRF, make a ripple in dualbeam
There is position in Doppler domain and avoids another wave beam in the azimuth ambiguity of beam.
8. the PRF selection systems of dualbeam SAR obscured based on top optimization direction according to claim 7 a kind of, its feature
It is：Authentication module is further included, authentication module is verified in PRF selecting modules by orientation dualbeam SAR l-G simulation tests
The correctness of PRF systems of selection.
9. the PRF selection systems of dualbeam SAR obscured based on top optimization direction according to claim 7 a kind of, its feature
It is：Position is occurred in Doppler domain according to azimuth ambiguity in determining module, obtains the azimuth ambiguity degree of orientation dualbeam SAR
AASR, formula are as follows：
<mrow>
<mi>A</mi>
<mi>A</mi>
<mi>S</mi>
<mi>R</mi>
<mo>=</mo>
<mfrac>
<mrow>
<munder>
<mo>&Sigma;</mo>
<mrow>
<mi>i</mi>
<mo>&NotEqual;</mo>
<mn>0</mn>
</mrow>
</munder>
<msubsup>
<mo>&Integral;</mo>
<mrow>
<mo>-</mo>
<msub>
<mi>B</mi>
<mi>a</mi>
</msub>
<mo>/</mo>
<mn>2</mn>
<mo>+</mo>
<msub>
<mi>B</mi>
<mrow>
<mi>o</mi>
<mi>f</mi>
<mi>f</mi>
</mrow>
</msub>
</mrow>
<mrow>
<msub>
<mi>B</mi>
<mi>a</mi>
</msub>
<mo>/</mo>
<mn>2</mn>
<mo>+</mo>
<msub>
<mi>B</mi>
<mrow>
<mi>o</mi>
<mi>f</mi>
<mi>f</mi>
</mrow>
</msub>
</mrow>
</msubsup>
<mi>G</mi>
<mrow>
<mo>(</mo>
<mi>f</mi>
<mo>+</mo>
<mi>i</mi>
<mo>&CenterDot;</mo>
<mi>P</mi>
<mi>R</mi>
<mi>F</mi>
<mo>)</mo>
</mrow>
<mi>d</mi>
<mi>f</mi>
</mrow>
<mrow>
<msubsup>
<mo>&Integral;</mo>
<mrow>
<mo>-</mo>
<msub>
<mi>B</mi>
<mi>a</mi>
</msub>
<mo>/</mo>
<mn>2</mn>
<mo>+</mo>
<msub>
<mi>B</mi>
<mrow>
<mi>o</mi>
<mi>f</mi>
<mi>f</mi>
</mrow>
</msub>
</mrow>
<mrow>
<msub>
<mi>B</mi>
<mi>a</mi>
</msub>
<mo>/</mo>
<mn>2</mn>
<mo>+</mo>
<msub>
<mi>B</mi>
<mrow>
<mi>o</mi>
<mi>f</mi>
<mi>f</mi>
</mrow>
</msub>
</mrow>
</msubsup>
<mi>G</mi>
<mrow>
<mo>(</mo>
<mi>f</mi>
<mo>)</mo>
</mrow>
<mi>d</mi>
<mi>f</mi>
</mrow>
</mfrac>
</mrow>
In formula, BaFor doppler bandwidth, BoffFor doppler centroid, G is antenna radiation pattern, and PRF is pulse recurrence frequency, f
For Doppler frequency, i is non-zero integer.
10. the PRF selection systems of dualbeam SAR obscured based on top optimization direction according to claim 7 a kind of, its feature
It is：PRF selecting modules are special further according to sampling thheorem and spectrum folding according to the azimuth ambiguity degree of orientation dualbeam SAR
Property, formulates optimal PRF systems of selection, obtains optimal PRF, makes the azimuth ambiguity of a wave beam in dualbeam in Doppler
There is position and avoids another wave beam in domain, specific as follows：
PRF selecting modules determine the center frequency difference f of two wave beams according to the azimuth ambiguity degree of orientation dualbeam SARc；When most
Excellent pulse recurrence frequency PRF elects as front and rear to center frequency difference 2fc1/ (n+0.5) when, n is positive integer, obtains PRF, can
So that another beam center is farthest apart from main beam, the aliasing of minimum, such as following formula are brought：
<mrow>
<mi>P</mi>
<mi>R</mi>
<mi>F</mi>
<mo>=</mo>
<mfrac>
<mrow>
<mn>2</mn>
<mo>&CenterDot;</mo>
<msub>
<mi>f</mi>
<mi>c</mi>
</msub>
</mrow>
<mrow>
<mi>n</mi>
<mo>+</mo>
<mn>0.5</mn>
</mrow>
</mfrac>
<mo>-</mo>
<mo>-</mo>
<mo>-</mo>
<mrow>
<mo>(</mo>
<mn>2</mn>
<mo>)</mo>
</mrow>
</mrow>
fcTo be front and rear to center frequency difference.
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