at slightly different frequencies. It is not clear at this time, if this effect could seriously affect beam efficiency. Preliminary attempts at modeling this effect have led to completely opposite results. One model indicates that, in the presence of doppler shift, the separation between the receiver and transmitter must be accounted for and leads to unacceptable beam degradation or severe restrictions on structural motion. An alternate model indicates that only the motion relative to the reference conjugation module needs to be accounted for and leads to virtually no beam degradation and liberal restrictions on structural motion. Continuing studies on this subject are being pursued by others. Another potential problem is the need for isolation of the uplinked referenced signal and the downlinked power beam. It appears sufficient isolation can be achieved by such methods as polarization discrimination and/or the use of affect pilot tones and frequency discrimination. However, this should be verified experimentally. In addition there will be a need for compensating the non-zero phase insertions of components and subsystems. In particular the distribution of the centrally received reference frequency, Wo, to each of the conjugation modules is critical. It is easily shown that any phase error introduced during reference frequency insertion at the local modules appears in the output of those modules with its magnitude doubled. Fortunately, reference frequency distribution has successfully been accomplished over large apertures in systems designed for radio astronomy. In particular it has been demonstrated (reference 13) that reference distribution can be accomplished with coaxial cables having electronic
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