1. Presented by,
B. Arthi
2012610031
Anna University, Chennai

2.  Airborne or spaceborne sidelooking radar system
 Flight path : To simulate extremely large antenna or aperture
 High - resolution remote sensing imagery
 Signal processing uses,
Magnitude
Phase
 After a number of cycles,
 The stored data is recombined
 High resolution image of the terrain is created

3.  SAR-processor stores all radar returned signals, for time




period T
Signal is reconstructed from antenna of length,
v·T
Where,
v is the platform speed
As LOS direction changes along radar platform trajectory,
 SA is produced by signal processing
 Effect of lengthening the antenna
Making T large makes the “synthetic aperture” large
Hence, the higher resolution

5.  The requirements are,
 Stable, full - coherent transmitter
 An efficient & powerful SAR - processor
 Exact knowledge of the flight path & the velocity of
the platform

6.  Cross - range resolution,
δcr = RθB
 Sequential generation of antenna aperture
 Sidelooking radar (SLR)
 Element spacing,
de = vTp = v / fp

7.  Conventional antenna beam width,
θB = kλ / D
 SA antenna beam width,
θS = kλ / 2Le
 Problem : Limits on the maximum effective length,
 Le ≤ RθB
 Unfocused SAR

8.  Solution :
 Phase correction at each “element”
Δφ = 2πx2 / λR
 Focused SAR
 Different correction for each range R
 Cross - range resolution,
δcr = RθS = D / 2
 Independent of Range
 Independent of frequency
 Depends on dimension, D

9.  Prf must be high enough to avoid,
 Angle ambiguities
 Image - foldover
 The resolution and the coverage can not be selected
independently
 Distance travelled by radar between pulse transmissions
should be less than λ / 2

10.  General form of radar eqn.,
 SAR radar equation,
 On further substitutions,

12.  Military reconnaissance
 Measurement of sea state & ocean wave conditions
 Geological & mineral explorations
 Surveillance & Targeting
 Ground Penetration
 Moving Target Indication
 Change Detection
 Environmental Monitoring

13.  SAR combines many viewing angles to,
 Effectively create a large aperture radar
 Resolution improves with,
 Bandwidth
Integration angle
 Good focus requires precise motion measurement
 Image interpretation requires,
 Training
 Practice