Microwave time delay spectroscopic methods and apparatus for remote interrogation of biological targets

Microwave time delay spectroscopic apparatus for remote interrogation of a biological target, comprising means for generating a microwave signal which varies in frequency from a first frequency to a second frequency in a predetermined time period, means for dividing said signal into first and second propagation signals, a test channel through which said first propagation signal is propagated, said test channel comprising a transmitting antenna for transmitting said first propagation signal through the target, and a receiving antenna for receiving said first propagation signal transmitted through the target, a reference channel through which said second propagation signal is propagated, said reference channel providing a fixed time delay of propagation therethrough, means for detecting and mixing said first and second propagation signals following propagation thereof through said test and reference channels, respectively, to produce a time delay spectrum wherein the frequency of each spectral line represents the instantaneous difference in frequencies of the detected propagation signals.