 Using the air traffic control illuminator, the receiver used pulse compression filtering of a chirp signal, which provided processing gain along with the ability to separate closely spaced targets.This also implemented a moving target indicator that suppressed clutter, but it was recognized that an MTI signal would not be available in a noncooperative environment.They concluded their work demonstrated feasible convergence of PCR and TDOA, using a shipborne R-ESM system with communications among the receivers, such that the processed signal is an interferometric process.