QUASI-OPTICAL TECHNIQUES FOR SIMULTANEOUS RECEPTION OF MULTIPLE MILLIMETER SIGNALS

摘要

This final report summarizes the results of a 16-month exploratory development program, which was initiated to investigate Quasi-Optical Techniques for Simultaneous Reception of Multiple Millimeter Signals, from widely separated sources. The program has theoretically demonstrated the feasibility of receiving 60-GHz signals, with high antenna gain, over a conical 18-degree field of view without time sharing. This is accomplished by combining a quasi-optical multibeam antenna with adaptive IF switching and combining networks. A 'pin chushion' of 1500 narrow overlapping beams, covering the required field of view, is generated by an optical system with an array of feeds in the focal plane. Each feed is connected to a separate receiver front-end, which may be constructed from low-cost integrated circuits. Each front-end contains a mixer, an IF amplifier, and its associated monitoring circuit. Based upon the monitored outputs, only those channels containing active signals are combined in a common output. a high signal-to-noise ratio (SNR) is maintained, since the maximum number of beams to be combined in a practical system is small compared to the total number of beams. The new approach provides important advantages over the more conventional communications techniques which require time-sharing, user coordination, and rapid beam steering.