by a Closely Spaced FM Interference

A new method for the estlmatlon of the parameters of a she slgnal corrupted by a strong FM Interference 1s presented. The method conslsts of two stages. In the Brst stage, whlch Is a novel one, an FM lnterference 1s transformed lnto a harmonlc wave wlth known frequency by uslng a speclal tlme-warplng technlque. Tlils harmonic lnterference 1s then rejected ln the transformed tlme domaln by a tlme-lnvarlant Constralned Notch Fllter. The tlme-warplng 1s lmplemented uslng non-unlform sampllng obtalned by utlllzlng a Phase Locked Loop (PLL) technlque. It 1s shown that such processlng results In a OdB Slgnal to Interference Ratlo at the output (SR0) Independently of the Slgnal to Interference Ratlo at the input (SIR,) (for negative values In dl3). The second stage lnvolves parameter estlmatlon, where a Constralned Adaptlve Notch Fllter Is used for the enhancement of a slgnal under analysls.