Abstract: A range determination apparatus for determining target range within a range depth of D and within a range bin error of e comprises a carrier frequency transmitter for transmitting a carrier frequency and a generator for generating at least two modulating signals having frequency f.sub.1 and f.sub.2, respectively. A modulation device, operative for at least two discrete frequencies for providing one of simultaneous or sequential modulated signals, is coupled to the carrier frequency transmitter for modulating the carrier. The two modulating frequencies and a common sub-multiple counting frequency are related such that f.sub.o =m.sub.1.sup.' f.sub.1 =m.sub.2.sup.' f.sub.2. A receiver is provided for receiving a reflected signal from the target and for producing a corresponding received electrical signal. A phase detection device is responsive to the modulating signals of the generator and the received signals for detecting the phase difference x.sub.1.sup.' and x.sub.2.sup.