Abstract: Sub-sampled signals are compared to determine time delay, calibration of delay elements, and other precise time domain measurements, based on properties of aliased signals produced by the sub-sampling. In one embodiment, flip-flops sub-sample an input signal and a delayed signal. A counter measures time delay between edges in the sub-sampled input and sub-sampled delayed signal. The time delay is determined and averaged over a measurement window, and then scaled to determine an amount of delay of the delayed signal. Means to calibrate a delay element inside a measurement device (e.g., Bit Error Ratio Tester), utilizing sub-sampling techniques to achieve precise measurements very quickly and without the need for factory calibration.