The usual definition of phase conjugation includes only the case co’ = co. Our definition is generalized in order to emphasize that co’ = co is neither necessary nor desirable; retrodirectivity holds in either case provided only that the propagation medium is non-dispersive, and to’ = co is usually to be avoided because of input-output isolation problems. An ARA can also function as a receiving (i.e., tracking) array. It is easy to show how a single PCC at each element can be used for both functions, receiving as well as transmitting, simultaneously, with little additional equipment. Specific examples will be given in our discussion of PCC’s below. B. Applications Although not a new idea (the concept was first proposed by W. E. Morrow in 1958 [1], ARA’s have yet to be applied practically. A number of experimental systems were built in the early sixties [2], [3], but the ARA activity visible in the literature has been sparse in recent years. ARA’s would seem, however, to fit quite naturally into space communication systems requiring highly directive spacecraft antennas. In the following we outline just three of the many possible ARA space applications. Solar Power Satellite Much of the current interest in ARA’s is centered about its possible application to the Solar Power Satellite (SPS) concept of Glaser [4] and Brown [5]. The SPS would be placed in a geosynchronous orbit. Several gigawatts of microwave power, generated by and converted from the de output of huge solar cell panels, would be transmitted to a rectifying antenna ("rectenna”) on the Earth’s surface. The SPS-rectenna range would be 36,000 km, the rectenna diameter 7.4 km, and the frequency S-band (A w 12.5 cm). These parameters plus stringent sidelobe
RkJQdWJsaXNoZXIy MTU5NjU0Mg==