A method of detecting an object is disclosed, comprising generating a transmission signal by generating a carrier signal and digitally modulating the carrier signal with a transmission modulation signal, and transmitting the transmission signal. A reflected signal is received, the reflected signal having been reflected from the object, and demodulated to extract a received modulation signal. The received modulation signal is correlated with the transmission modulation signal and a range of the object is determined from the correlation of the received modulation signal and the transmission modulation signal.