Abstract: A signal processing apparatus for providing electrical frequency measurements of input signals. In one embodiment, a power splitter divides an RF input signal into first and second input signals. An RF channelizer having a filter bank receives the first input signal and determines a coarse frequency measurement. An optical modulator modulates an optical carrier signal with the second input signal, and a beam splitter divides the modulated carrier signal into a plurality of optical signals that each feed into one of a plurality of optical frequency discriminators (“OFD”). Each OFD uses a fiber optic delay line and spatial domain sampling techniques to extract a phase measurement. An ambiguity resolver receives the phase measurement from each OFD and determines a single, absolute phase measurement, which is translated to a fine frequency measurement. A frequency encoder combines the coarse and fine frequency measurements to produce a final frequency measurement having increased resolution.