1. Range-wavenumber representation of SAR Signal
santhosh

2. SAR Signal (processing)
Two dimensional (energy spread in range and azimuth)
Goal : to focus into single pixel.
Range dimension- spread – duration of chirp transmitted.
Azimuth dimension- spread- duration of synthetic aperture

3. . Range variation zero-Doppler position distance X-axis
Range variation causes phase variation in received signal as a function of azimuth
Fig.: © DLR

4. Formation of the Azimuth Chirp Signal

5. Demodulated baseband SAR signal
includes R-4 and target RCS factors
transmit waveform amplitude
antenna gain variation over synthetic aperture
range-dependent phase component
quadratic phase term due to transmitted chirp waveform

6. Chirp transmitted
Delayed received signal
Demodulated base band signal
Range Fourier Transform- POSP
Azimuth Fourier Transform – 2d frequency domain – POSP
Approximation (linearization) of phase
Range – Inverse Fourier transform – range – Doppler domain

7. (After Secondary Range Compression)
RDA
Range FFT on raw data – matched filter(pulse compression)- azimuth FFT –secondary range compression – Range IFFT (range –Doppler domain) – RCM in Doppler domain by sinc interpolation (depends on absolute Doppler)- azimuth compression filter – azimuth IFFT
2D Fourier Domain (3 targets)
Range Doppler Domain
(After Secondary Range Compression)
Raw Data (single target)

8. CSA
Azimuth FFT (range – Doppler domain) – chirp scaling – range FFT- range compression(+ range/azimuth decoupling) – bulk RCM – range IFFT (range- Doppler domain) – azimuth compression & phase correction – azimuth IFFT
After range IFFT
Range –Doppler domain