Fig. 1

a (Left) original range spectrum with its center frequency f ₀ and bandwidth B _w . (Right) corresponding base-banded SLC data from a point target at R. Here, T and τ indicate the pulse length and the delay time 2R/c from a target, respectively; c is the speed-of-light. The sinc function is defined as sinc(x) = sin(πx)/πx. b (Left) bandpass-filtered range spectrum with a new higher central frequency f _H and bandwidth B ^H _w . (Right) corresponding bandpass SLC data from a point target at R. T _H indicates the reduced pulse length. c (Left) base-banded range spectrum with a new higher central frequency f _H and bandwidth B ^H _w . (Right) corresponding base-banded SLC data from a point target at R with new center frequency f _H