a system for measuring an rf input signal frequency includes a sampling optical pulse train with a frequency - dithered repetition - rate , and a sub - sampled analog link coupled to the optical pulse train whereby the rf input signal frequency is determined . this frequency dither imparts well - characterized modulation sidebands onto the input rf signal to be measured . by measuring the amplitude of these sidebands relative to the incoming aliased signal amplitude the frequency of the original signal is readily determined . the use of optical sampling dramatically increases the bandwidth over which the disambiguation technique is applied , and coarse disambiguation is achieved in a single acquisition .