Abstract: An equivalent time pulse-echo radar or other pulse-echo system employs a transmit reference sampler collocated with the transmitter to provide a transmit reference pulse, which initiates a pulse width modulated (PWM) pulse. A receive sampler connected to a receive antenna provides an echo-detection pulse that terminates the PWM pulse, such that the width of the PWM pulse indicates target range. The transmit reference sampler and the receive sampler are driven from a common clock such that transmit-receive timing offset drift precisely cancels on a picosecond scale, thereby enabling sub-mm range accuracy with common, low-cost circuit elements. The radar further includes automatically referenced pulse detectors that are responsive to either the magnitude or the phase of the sampler outputs. The radar can be used for precision tank level measurements, robotics, or automotive ranging applications.