Kontrollküsimused 5. osa kohta

Sidelobes of the SAR antenna

The speckle effect

Sinc function response for point targets

Because echoes of different objects are coherently added in random phase within a resolution cell resulting either constructive or destructive interference

Because there is always noise in the receiving SAR antenna due to non-ideal cooling (thermal noise)

Because of non-ideal timing of the neighboring echoes are received with variable time intervals causing the received focused signal to fluctuate

In order to achieve range resolution as different object echoes come from different distances, hence at different time and by splitting the signal in time, it is possible to achieve resolution in range

In order to achieve azimuth resolution as the echoes from different objects come in different phase thus forming a synthetic chirp, which is later correlated with another chirp to achieve sinc-like response

By exploiting the range dependent phase history of the recorded neighboring echoes in azimuth direction

By exploiting the azimuth dependent phase history of the recorded neighbouring echos in range direction

By synthetically building a large aperture antenna of small dipoles - a phased array

By building a large aperture antenna with a small footprint on ground

chirp - linear frequency modulated sinusoid

Gaussian impulse

impulse - Dirac delta

sinc function

Heaviside step function

Correlation and signal multiplication as it's frequency domain equivalent, FFT for transforming the signal to frequency domain and then back to time domain again

Fourier transform, taking the Fourier transform of a SAR image will focus the raw signal to a high resolution 2D image

Hamming filtering to suppress the sidelobes and enhance the main lobe of a point target response on a SAR image

False

True

True

False

da/2, where da is the antenna length in azimuth direction

(lambda*r0)/da, where lambda is the wavelength, r0 is distance to the object and da is the antenna length in azimuth direction

(theta_a*r0)/2, where theta_0 is the antenna beamwidth in azimuth and r0 is distance to the object