PARIS Interferometric Processor Analysis and Experimental Results:   Theoretical Feasibility Analysis
  Several experimental results show that it is possible to extract useful phase information from reflected GPS signals over the oceans. In this work we begin the development of the theoretical background to account for these results and fully understand the phenomena involved. This information will then be used to define and carry out new experiments to evaluate the feasibility of using the phase from reflected GPS signals for altimetric purposes and the advantages of using interferometric combinations of the signals at different frequencies---the PIP concept.   We focus on the coherence properties of the signals, including the PIP interferometric combination of phases in the different frequencies. In this work we will concentrate on a static, 8 m high receiver (at least in regards to the simulations), and an infinitely removed static source. As the ocean moves, the received field will pick up a random phase. We want to understand the behavior of this phase, as the goal is to carry out altimetric measurements using phase ranging. We will also show that this random phase carries geophysical information (intuitively, the bigger the significant wave height, the larger the phase excursions). 
Giulio Ruffini i Fores, Francois Soulat