A gesture detection system uses two radar tones to concurrently detect absolute distance and relative movement of a target object. A radar-based detection device alternates transmitting a first radar tone and a second radar tone via a radar-emitting device, and then captures a first return signal and a second return signal that are generated by the first radar tone and second radar tone reflecting off the target object. The radar-based detection device demodulates the return signals into a first set of quadrature signals and a second set of quadrature signals and, in some cases, generates a first set of digital samples and second set of digital samples from the respective quadrature signals. Various aspects process the first set of digital samples and second set of digital samples to concurrently identify absolute distance and relative movement and, at times, determine an in-the-air gesture performed by the target object.