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Study on the jamming to synthetic aperture radar | Radar | Radio

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Study on the Jamming to Synthetic Aperture Radar Xianfeng Tian Guangyou Fang Institute of Electronics, Chinese Academy of Sciences, Beijing 100190, China 1. Introduction The history of synthetic aperture radar (SAR) may retrospect to 50's last century. The main purpose of SAR is to image the terrain of the detected area using microwave [1, 2]. It can work at all time and all weather; moreover it has ability to penetrating foliage. Owing to these features, it finds its way in many civil and milit
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  Study on the Jamming to Synthetic Aperture Radar Xianfeng Tian Guangyou FangInstitute of Electronics, Chinese Academy of Sciences, Beijing 100190, China 1. Introduction The history of synthetic aperture radar (SAR) may retrospect to 50's lastcentury. The main purpose of SAR is to image the terrain of the detected areausing microwave [1, 2]. It can work at all time and all weather; moreover ithas ability to penetrating foliage. Owing to these features, it finds its way inmany civil and military applications. The susceptibility of SAR system tointerference is of concern in both military and civil applications [1,2].Synthetic aperture radars play very important roles in the just passed war.How to protect keystone areas to avoid reconnaissance by opponent SAR  becomes key field for the study of ECM [2].The synthetic aperture radar has special features different from conventionalradar, such as high processing gain in range and cross-range, large antennaaperture achieved by movement of radar platform and much wider signal bandwidth [1, 3]. So studying on jamming to SAR is significant to war in thefuture. According to the relationship of noise interference and echo, there areseveral jamming types, such as, noise jamming, coherent jamming, partcoherent jamming and deceptive jamming [2]. This paper introduces a novelradar equation relating the effectiveness of SAR ECM jamming to the mainsystem parameters. Through analyzing the signal power of the video data(image data), it is found that deceptive jamming to SAR is a good method; andcoherent jamming is feasible. 2. SAR ECM Radar Equation An expression for a measure of the susceptibility of a SAR to jamming as afunction of system parameters is derived. It is shown to be a simplerelationship between average transmitted power of SAR, the jammer’sequivalent isotropic radiated power (EIRP), the incidence angle and thenormalized clutter backscatter. The assumption is made that the SAR followsthe conventional design constraints [3, 4, 5].The echo power that radar received is presented by:  22234 P(4)(4) t t t t r rs  PG A PG Gr r  σ σλ π π  = =  (1)  0 ; a gr   A A σ σ ρ ρ  = = ⋅ , r   ρ  is ground resolution. Taking into account system loss,loss gene ( S   K  ) is introduced. Equation(1) can be changed:  2320r03433 1P()2(4)2(4) t gr t t r  s gr aa s s s s  PG PRF  PG Gr T PRF T vr K r v K  σ λ ρ σλ λ σ ρ π π  ⋅ ⋅= ⋅ ⋅ ⋅ ⋅ =  (2)  The power intercepted by the radar is represented by:  2222 ()()4444  j j j j j j jr r rj a rj a j j j j  P G P G B B P G P G B B R R L L λ γ  λ θ θ π π π π γ   = ⋅ = ⋅    (3)  The noise single ratio (SNR) is presented by: 978-1-4244-2642-3/08/$25.00 ©2008 IEEE Authorized licensed use limited to: INDIAN INSTITUTE OF TECHNOLOGY MADRAS. Downloaded on May 28, 2009 at 22:35 from IEEE Xplore. Restrictions apply.   42r  4() rj j ja J S  s a jt t  j jf    P p G r G K K  P G P  LG RK  π θ σ γ   = = ⋅ ⋅ ⋅  (4)  The jamming equation is presented by:  2r 4 PEIRP=()4 r J j f  a j j S  j j a G K R K GG P K  L Gr  σ γ θ π  = ⋅ ⋅ ⋅  (5)   j j  PG is jamming power. r  P r  G is transmitter power.  j  R is the distance betweenradar and jammer. r  is the distance between radar and target; /  f j r   K B B = isreceiver bandwidth and jamming signal bandwidth. j  B is jamming barrage bandwidth. r   B is SAR chirp signal bandwidth. j  L is jammer loss.  j γ   is polarization loss. /() a a G G θ  is the ratio of SAR major lobe gain and minor lobes gain.Basic condition of valid jamming to SAR is /  J   J S K  ≥ , so jammer validworking range can be presented by:  24 ()()4 t t j t a J  j j j j f    PG R GG r K  L K  p G σ θ θ π γ   ≥ ⋅ ⋅  (6)  When jammer and target stand on same position, ()() a t  G G θ θ  = and least validtarget distance min t   R can be got:  214min ()4 t t jt J  j j j j f    PG R R K  p G L K  γ  σ π  ≥ ⋅  (7)  Least jamming power is presented by:  24min ()4EIRP t t j t j f  t  j J   PG R G K  R L K  σ θ π γ   ≥ ⋅  (8)    3. Jamming Energy Distributing Jamming power is a best way to scale jamming effect. It is better to attainsame jamming effect, if the jamming power is less. Jamming equation isdeduced from energy distribution at this chapter. The power that jammer needsto transmit is analyzed at different jamming modes [6, 7].Suppose there is a ground distinguish cell x g   ρ ρ  × , one echo power  (,)  E m n is:  ( ) 22 ,(4) t x g t t  G A E m n K P t  R  ρ ρ σ π  = ⋅ Δ   (9)  At is effective receiving area; K is gain of receiver power, 2 4/ t  t  G A π λ  = , t  Δ issampling holding time. Equation(9) can be changed:  ( ) 2234 ,(4) t x g t  G E m n KP t  R  ρ ρ σλ π  = Δ  (10)  At one echo jamming power  (,)  j  E m n is presented by     ( ) 2 (),4  j t j j j j j f   j G A L E m n KP t  K  R θ γ  π  = ⋅ Δ  (11)  From equation(11) and equation(4),  J   K  of one echo is presented by:  22222 (,)()(4)(,)  j j j t j j jt f   j t x g  J   E m n P G A L R R E m nR G K  P K  θ γ  π  ρ ρ σλ  = = ⋅  (12)  Authorized licensed use limited to: INDIAN INSTITUTE OF TECHNOLOGY MADRAS. Downloaded on May 28, 2009 at 22:35 from IEEE Xplore. Restrictions apply.  () t j  A θ  is valid caliber at jammer direction. After imaging to echo data, NSR of video signal is presented by:  22222 (,)()(4)(,)  j j j j j t jr a r a f t  j J t x g   E m n L P G A J J J J RR E m n MN K M  K  N P  R G γ θ π  ρ ρ σλ  = = ⋅  (13)   Jr  is gain of jamming signal in range.  Ja is gain of jamming signal incross-range. MN  is energy gain; M B τ  = ⋅ is range gain; and /  N R PRF v θ  = ⋅Δ⋅ ,isazimuth gain. Now, the energy gain of SAR amounts to 60  70dB, so much asmore.From equation(13) and equation(8), EIRP can be get:  ( )( )( )( ) 222222222222222 EIRP(4)()//4()/24()sin  f av t x g j j j r at j f av t x g j j j r at j f jav t  j j r at  J  J  J  j  K MNP G R L J J R PRF A R K R v PRF BP G R L J J R R PRF A K R P G c y L J  K  K  K  J R R PRF v A  ρ ρ σλ γ  π τ θ θ ρ ρ σλ γ  π θ θ σλ γ  π θ α  ≥⋅ ⋅Δ=⋅Δ ⋅ ⋅ Δ=⋅ ⋅ ⋅ ⋅  (14)  ( ) 1//2/sin  x B c  ρ α  = ⋅ ; av  P  is average transmitter power. α  is angle of incidence; θ  Δ is beam width.  JaJr  is different, if jammer works in different modes. Active noise jamming belongs to barrage jamming. It put noise interference over the echoes of targets to diffuse target information. Noise jamming signal is not coherent toSAR echo, so 1  JaJr  = . Coherent jamming signal is mainly coherent to echo inrange, and  JaJr N  = . Deceptive jamming is coherent to echo in range andcross-range, and JaJr MN  = . Part-coherent jamming is intervenient, and 1 JaJr MN  < < . Fig1 shows the jamming effect of four modes. For the purpose isto express focusing and distributing of jamming energy, coordinate data hasnot actual meaning.In noise jamming mode, energy distributes averagely in video signal, and jammer power required can amount to 10 6 watt. So it is too difficulty to obtainvalid jamming effect. Deceptive jamming is a good mode, and the mainenergy focuses one spot. Parameters of SAR need to be reconnoitredaccurately. Coherent jamming or part Coherent jamming is easy to implement,and needs not too large power, and energy focuses some area. Jamming effectis similar to noise jamming in jammed region. 4. Conclusion The paper manly relates jamming power and jamming effect of four  jamming modes. Jamming equation associating with the SAR and jammer  parameters is got. Jammer’s working distance is got through analyzing the jamming equation. Characteristic of four jamming modes is analyzed throughthe gain of video signal. Deceptive jamming is a preferred mode, if SAR  parameters can be acquired accurately. Coherent jamming or part-Coherent isan important mode. References Authorized licensed use limited to: INDIAN INSTITUTE OF TECHNOLOGY MADRAS. Downloaded on May 28, 2009 at 22:35 from IEEE Xplore. Restrictions apply.  [1] J C Curlander, R N Mcdonough. Synthetic aperture radar systems andsignal processing. John Wiley & Sons, Inc, 1991.[2] Walter W.Gog. “Synthetic-aperture Radar and Electronic Warfare”.Artech House, 1993. Boston London.[3] Christopher J C. “Some system considerations for electronic counter measures to synthetic aperture radar”. Radar, IEEE Colloquium onElectronic Warfare Systems, 1991, vol8.pp 1-7.   [4] Per Hyberg, “Assessment of Modern Coherent Jamming Methods againstSynthetic Aperture Radar”. European Conference on Synthetic ApertureRadar, 1998.5 pp.391 - 394   [5] K Dumper eta1, “Spaceborne Synthetic Aperture Radar and NoiseJamming ”, Radar. 1997.10, pp. 411-414.[6] Zheng Shenghua, Xu Dazhuan, Jin Xueming. “Study on active jammingto synthetic aperture radar”. International conference on computationalelectromagnetic and its applications proceedings, 2004. 403-406.[7] Wang Shengli, Yu Li, Ni Jinlin, “A Study on the Active DeceptionJamming to SAR”. ActaElectronica Siniea. 2003,31(12):pp.1900-1902. Figure Fig1: Numeric Simulation Result of Four Jamming Modes   Authorized licensed use limited to: INDIAN INSTITUTE OF TECHNOLOGY MADRAS. Downloaded on May 28, 2009 at 22:35 from IEEE Xplore. Restrictions apply.
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