CN106646472B - SAR radio frequency interference suppressing method based on null tone cascade filtering - Google Patents
SAR radio frequency interference suppressing method based on null tone cascade filtering Download PDFInfo
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- CN106646472B CN106646472B CN201611260024.6A CN201611260024A CN106646472B CN 106646472 B CN106646472 B CN 106646472B CN 201611260024 A CN201611260024 A CN 201611260024A CN 106646472 B CN106646472 B CN 106646472B
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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
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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
-
- 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
- G01S7/023—Interference mitigation, e.g. reducing or avoiding non-intentional interference with other HF-transmitters, base station transmitters for mobile communication or other radar systems, e.g. using electro-magnetic interference [EMI] reduction techniques
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- Engineering & Computer Science (AREA)
- Remote Sensing (AREA)
- Radar, Positioning & Navigation (AREA)
- Physics & Mathematics (AREA)
- Computer Networks & Wireless Communication (AREA)
- General Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Signal Processing (AREA)
- Radar Systems Or Details Thereof (AREA)
Abstract
The present invention provides a kind of radio frequency interference suppressing method based on null tone cascade filtering.Technical solution includes the following steps: step 1: the DOA of RFI estimates.The DOA that RFI in reception signal is estimated using MUSIC algorithm, the steric direction vector of all RFI is determined according to DOA.Step 2: frequency domain filtering.Signal will be received and carry out FFT transform to frequency domain, isolate the frequency spectrum Support of RFI from reception signal using 3 δ diagnostic methods.Step 3: airspace filter.Radio frequency interference, which is calculated, by space filtering filters out interference.The loss of useful signal can be effectively reduced using the present invention, there is better interference suppressioning effect.
Description
Technical field
The invention belongs to the interleaving techniques field of space flight and microwave remote sensing, in particular to a kind of SAR (Synthetic
Aperture Radar, synthetic aperture radar) RFI (Radio Frequency Interference, radio frequency interference) in data
Suppressing method.
Background technique
It works and is easy in the SAR (Synthetic Aperture Radar, synthetic aperture radar) of low band by same
The interference of the television network, communication network and other civil equipment institute transmission of electromagnetic signals of frequency range, i.e., so-called RFI (Radio
Frequency Interference, radio frequency interference).The presence of RFI seriously affects the quality and interpretation and interpretation of image.Mesh
Preceding airspace filter method, " Zhu Feng, Zhang Youyi are to the modern electricity of the Study of Interference [J] of adaptive spatial filtering for the document that sees reference
Sub- technology, 2013,36 (11): 67~74 ".For Whole frequency band filtering, useful signal identical with the direction RFI is totally constrained,
While inhibiting RFI, useful signal is also suppressed.
It is proposed a kind of based on null tone cascade filter for this status according to the high power of radio frequency interference, narrow-band characteristic
The radio frequency interference suppressing method of wave.Before airspace filter, frequency domain filtering is carried out to signal is received, isolates the frequency where RFI
Band, then airspace filter is carried out for the frequency band where RFI.Compared to existing airspace filter method, mentioned method will be damaged herein
The useful signal of mistake is limited in the narrow-band where RFI, effectively reduces the loss of useful signal.
Summary of the invention
The purpose of the present invention is: a kind of radio frequency interference suppressing method based on null tone cascade filtering is proposed, it can be effective
Ground reduces the loss of useful signal, has better interference suppressioning effect.
The thinking of technical solution of the present invention is: first with MUSIC (Multiple Signal Classification,
Multiple signal classification) algorithm estimates the DOA (Direction of Arrival, direction of arrival) of RFI, then constructed according to DOA
The steric direction vector of RFI.Next signal will be received by FFT transform to frequency domain, according to the high power of radio frequency interference, narrow frequency
Band characteristic carries out frequency domain filtering to signal is received, isolates the frequency band where RFI.Finally, utilizing the steric direction vector of RFI
Spatial filter is constructed, for the band signal where RFI, is realized and is filtered using spatial filter.
The technical scheme is that: a kind of SAR radio frequency interference suppressing method based on null tone cascade filtering, it is assumed that x (t,
ηL) indicate SAR in slow moment ηLReception signal, wherein t indicates fast time, which is characterized in that includes the following steps:
Step 1: the DOA of RFI estimates:
Estimate to receive signal x (t, η using MUSIC algorithmL) in RFI DOA, determine that the space of all RFI is led according to DOA
To vector, remember that the steric direction vector of i-th of RFI is d (θi), i=1,2 ..., N, N indicate the number of RFI.
Step 2: frequency domain filtering:
Signal x (t, η will be receivedL) FFT transform is carried out to frequency domain, it obtains receiving frequency domain signal X (f, ηL)；
Frequency spectrum Support X (f ', η ' of RFI are isolated from reception signal using 3 δ diagnostic methodsL),
Wherein, 0≤η 'L≤ Δ η, 0≤f '≤BS, Δ η is to receive signal x (t, ηL) in there are the slow times of radio frequency interference
Width, BSTo receive signal x (t, ηL) in radio frequency interference bandwidth；
Step 3: airspace filter:
Radio frequency interference r (f ', η ' are calculated using following formulaL'):
Wherein DH(θi) it be steric direction vector is d (θi) frequency domain complex conjugate vector；
Again from frequency domain signal X (f, ηL) in subtract radio frequency interference r (f ', η 'L), obtain the reception inhibited through radio frequency interference letter
Number.
Following technical effect can use to obtain using the present invention:
SAR radio frequency interference suppressing method proposed by the present invention based on null tone cascade filtering, the frequency domain that RFI is utilized are special
Property, first to signal progress frequency domain filtering is received, isolate the frequency band where RFI.Then, the steric direction vector of RFI is utilized
Spatial filter is constructed, for the band signal where RFI, is realized and is filtered using spatial filter.The present invention can will lose
Useful signal be limited in the narrow-band where RFI, be effectively reduced the loss of useful signal, improve the matter of image
Amount.
Detailed description of the invention
Fig. 1 is the principle flow chart of SAR radio frequency interference suppressing method provided by the invention；
Fig. 2 is the imaging results of point target used in emulation experiment；
Fig. 3 is the imaging results that point target after radio frequency interference is added to Fig. 2；
Fig. 4 is using existing airspace filter method to imaging results after Fig. 3 progress AF panel；
Fig. 5 is to use the method invented provide herein to imaging results after Fig. 3 progress AF panel；
Fig. 6 is the imaging results of measured data used in emulation experiment；
Fig. 7 is the imaging results that data after radio frequency interference are added to Fig. 6；
Fig. 8 is to carry out the imaging results after AF panel to Fig. 7 using existing airspace filter method；
Fig. 9 is to carry out the imaging results after AF panel to Fig. 7 using method provided by the invention.
Specific embodiment
Fig. 1 is the principle flow chart of suppression method for satellite-borne SAR radio-frequency interference provided by the invention.In order to original of the invention
Reason is described in detail, and is illustrated below from theory deduction angle:
Assuming that x (t, ηL) indicate SAR in slow moment ηLReception signal, receive signal x (t, ηL) it can be expressed as following shape
Formula:
Wherein, sk(t,ηL) fast time t antenna array is corresponded in slow moment ηLK-th of the useful signal received, φk
It is the DOA of k-th of useful signal, d (φk) be k-th of useful signal steric direction vector, K is the number of useful signal, this
Variable, which calculates, to be needed, and is not required to estimate when being filtered below.ri(t,ηL) fast time t antenna array is corresponded in slow moment ηLIt connects
I-th of the RFI, θ receivediIt is the DOA of i-th of RFI, d (θi) be i-th of RFI steric direction vector, N is the number of RFI.
By x (t, ηL) FFT transform is carried out to frequency domain, such as following formula:
Wherein DH(θi) it be steric direction vector is d (θi) frequency domain complex conjugate vector.
According to the frequency spectrum characteristic of RFI, the frequency spectrum Support of RFI is isolated from reception signal using 3 δ diagnostic methods.RFI's
Frequency spectrum Support is following form:
Wherein, 0≤η 'L≤ Δ η, 0≤f '≤BS, Δ η is that there are the slow time width of radio frequency interference, B in reception signalS
For the bandwidth for receiving radio frequency interference in signal.
Using the frequency domain complex conjugate vector of RFI steric direction vector as spatial filter, frequency spectrum Support where from RFI
RFI is extracted, such as following formula:
Further, the RFI form extracted is as follows:
Steric direction vector has following correlation:
Further, the RFI obtained is following form:
From the above equation, we can see that working as φk≠θiWhen, φ is worked as in no useful signal lossk=θiWhen, the useful signal of loss is Sk
(f ', η '), but the useful signal lost has been limited to 0≤f '≤BSIt is complete compared to existing airspace filter method in range
Frequency band loss, is effectively promoted the interference free performance of system.
Fig. 2~Fig. 5 is to carry out point target the simulation experiment result.Fig. 2 is original point target received signal imaging results, from figure
As can be seen that point target focusing effect is good as in.Fig. 3 is the imaging results added radio frequency interference in Fig. 2 and be followed by the collection of letters number,
It can be seen that point target has been disturbed signal annihilation.The original image of Fig. 2 and Fig. 3 is color image, and it is right after grayscale image to be changed to
Than unobvious.Fig. 4 is to carry out the imaging results after AF panel to Fig. 3 using existing airspace filter method, can from image
Out, interference focuses good, but detailed information is destroyed.Fig. 5 be using method provided by the invention carry out AF panel after at
As result, it can be seen that point target focuses well, and interferes residual less.
Fig. 6~Fig. 9 is the result for carrying out Area Objects emulation experiment.Emulation experiment has chosen a glitch-free airborne X wave
Section triple channel SAR measured data.
Fig. 6 is the imaging results of initial data used in emulation experiment.It can be seen from the figure that image clearly, comparison
Degree is high.Fig. 7 is the imaging results that data after radio frequency interference are added to Fig. 6.It can be seen from the figure that due to the presence of interference, figure
Picture target information is capped, picture contrast decline.Fig. 8 is that existing airspace filter method carries out the imaging after AF panel to Fig. 7
As a result, picture quality gets a promotion after AF panel, but the contrast of image declines, and light and shade region occurs, detailed information is not
Obviously.Fig. 9 is to carry out the imaging results after AF panel to Fig. 7 using method provided by the invention, after AF panel, image matter
Amount is obviously improved, and detailed information restores more obvious, and picture contrast is significantly improved.
The above emulation experiment illustrates that the method for the present invention can effectively make up existing method in terms of AF panel not
Foot effectively promotes the SAR image quality after AF panel.
Claims (1)
1. a kind of SAR radio frequency interference suppressing method based on null tone cascade filtering, SAR refer to synthetic aperture radar, it is assumed that x (t,
ηL) indicate SAR in slow moment ηLReception signal, wherein t indicates fast time, which is characterized in that includes the following steps:
Step 1: radio frequency interference DOA estimates:
Using MUSIC algorithm estimation SAR in slow moment ηLReception signal x (t, ηL) in radio frequency interference DOA, according to DOA determine
The steric direction vector of all radio frequency interferences, the steric direction vector of i-th of radio frequency interference of note are d (θi), i=1,2 ..., N, N
Indicate the number of radio frequency interference；Wherein, DOA refers to direction of arrival；
Step 2: frequency domain filtering
By x (t, ηL) Fast Fourier Transform (FFT) is carried out to frequency domain, it obtains receiving frequency domain signal X (f, ηL)；
Frequency spectrum Support X (f ', η ' of radio frequency interference are isolated from reception signal using 3 δ diagnostic methodsL),
Wherein, 0≤η 'L≤ Δ η, 0≤f '≤BS, Δ η is to receive signal x (t, ηL) in there are the slow time width of radio frequency interference,
BSTo receive signal x (t, ηL) in radio frequency interference bandwidth；
Step 3: airspace filter
Radio Frequency Interfere r (f ', η ' are calculated using following formulaL):
Wherein DH(θi) it be steric direction vector is d (θi) frequency domain complex conjugate vector；
Again from frequency domain signal X (f, ηL) in subtract Radio Frequency Interfere r (f ', η 'L), obtain the reception inhibited through radio frequency interference letter
Number.
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2004097451A1 (en) * | 2003-04-25 | 2004-11-11 | Telefonaktiebolaget Lm Ericsson (Publ) | Rfi suppression in sar |
| CN103675768A (en) * | 2013-12-17 | 2014-03-26 | 中国人民解放军国防科学技术大学 | Suppression method for satellite-borne SAR radio-frequency interference |
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Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2004097451A1 (en) * | 2003-04-25 | 2004-11-11 | Telefonaktiebolaget Lm Ericsson (Publ) | Rfi suppression in sar |
| CN103675768A (en) * | 2013-12-17 | 2014-03-26 | 中国人民解放军国防科学技术大学 | Suppression method for satellite-borne SAR radio-frequency interference |
Non-Patent Citations (3)
| Title |
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| RFI suppression in ultra-wideband SAR systems using LMS filters in frequency domain;X.Luo et al.;《ELECTRONICS LETTERS》;20010215;第37卷(第4期);全文 |
| 基于联合滤波的SAR射频干扰抑制方法;吴鹏 等;《雷达科学与技术》;20160630;第14卷(第3期);全文 |
| 对自适应空域滤波的干扰研究;朱峰，张友益;《现代电子技术》;20130601;第36卷(第11期);全文 |
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