Systems and methods for analyzing a characteristic of a transmitter, a receiver, or a propagation channel are disclosed. At least one receiver signal resulting from at least one transmitter signal that has propagated through a propagation channel can be obtained. A first signal pair can be formed from a first receiver signal and a first transmitter signal, or from first and second receiver signals obtained from spatially-separated receiver antennas, or from first and second receiver signals which are attributable to different transmitter signals. Amplitude and phase information of a plurality of frequency components for each signal in the first signal pair can be determined. A set of comparison values for the first signal pair can be determined by comparing respective frequency component phases or respective frequency component amplitudes. A characteristic of the set of comparison values can then be analyzed.