A radar system that can block false echoes includes: a local oscillator configured to generate a chirp signal comprising a plurality of chirps, each having a corresponding envelope; a transmitter configured to transmit a signal corresponding to the chirp signal; and a modulation circuit configured to modulate the transmitted signal by regulating a magnitude of one or more portions of the chirp envelopes in a predetermined pattern such that the radar system can discern false echoes which do not match the pattern.