Precision pointing of the receiving antenna is not necessary to the operation of the SSPS and inhomogeneities in the propagation path are not significant. Any deviation of the microwave beam beyond allowable limits would preclude acquisition of the pilot signal. Without the signal, the coherence of the microwave beam would be lost, the energy dissipated, and the beam spread out so the microwave power density would approach communication signal levels. This phase-control approach would assure that the beam could not be directed either accidentally or deliberately towards any other location but the receiving antenna. This inherent fail-safe feature of the microwave transmission system is backed up by the operation of the switching devices, which would open-circuit the solar cell arrays to interrupt the power supply to the microwave generators. e. Microwave Rectification The receiving antenna is designed tQ intercept, collect, and rectify the microwave beam into de which can then be fed into a high-voltage de transmission network or converted into 60-Hz ac. Half-wave dipoles distributed throughout the receiving antenna capture the microwave power and deliver it to solid-state microwave rectifiers (26). Schottky barrier diodes have already been demonstrated to have a 80% microwave rectification efficiency at 5W of power output. With improved circuits and diodes, a recreation efficiency of about 90% will be achievable. The diodes combined with circuit elements which act as half-wave dipoles are uniformly distributed throughout the receiving antenna, so the microwave beam intercepted in a local region of the receiving antenna is immediately converted into de. The collection and rectification of microwaves with a receiving antenna based on this principle has the advantages that the receiving antenna is fixed and does not have to be pointed precisely at the transmitting antenna. Thus, the mechanical tolerance in the construction of the receiving antenna can be relaxed. Furthermore, the illumination distribution of the incoming microwave radiation need not be matched to the radiation pattern of the receiving antenna; therefore, a distorted incoming wavefront caused by non-uniform atmospheric conditions across the antenna will not reduce efficiency. The amount of microwave power that is received in local regions of the receiving antenna can be matched to the power-handling capability of the solid-state diode microwave rectifiers. Any heat resulting from inefficient rectification in the diode circuits can be convected by the ambient air in the local region of the receiving antenna with atmospheric heating similar to that over urban areas. Only about 10% of the incoming microwave beam would be lost as waste heat. The low thermal pollution achievable by this process of rectification cannot be equaled in any known thermodynamic conversion process. The rectifying elements in the receiving antenna can be exposed to local weather conditions. The antenna can be designed so that sunlight would still reach the land beneath it, with only a fraction lost due to shadowing. Thus the land could be put to productive use.
RkJQdWJsaXNoZXIy MTU5NjU0Mg==