Sure-Fi signals can travel one mile through obstructions or more than 50 miles line-of-sight by using patented radio technology based on Chirp Modulation
. Chirp is a component of a radio signal where the actual signal increases and decreases in frequency, creating a pulse or chirp.
Nonlinear Chirp Scaling Algorithm (NCSA) can also deal with squint signal [1,13-16], however, NCSA is developed based on Chirp Scaling Algorithm (CSA), thus requires that the received echo signal must be in chirp modulation
. But in some situations the received signal does not hold the chirp modulation
, such as when dechirp-on-receive operation is applied in spotlight SAR  or Frequency Modulated Continous Wave (FMCW) SAR mode , NCSA will be completely disabled.