A scheme is disclosed whereby an antenna array is automatically directed by a simple intermodulation of signal components. In reception, each array element feeds a pilot signal and the modulated signal to a third‐order mixer wherein the phase associated with the signal in that element is automatically cancelled. This allows in‐phase addition of the contributions from the many elements irrespective of the array shape or the direction of the incoming signal. For transmission, a pilot signal received from the distant receiver location provides by intermodulation a phase compensation to the signal radiated from each transmitting element so as to automatically direct the radiated signal to the distant receiver. There are no significant restrictions as to the shape of the array or the frequencies used. The scheme lends itself to multiple‐element, low‐power circuitry and may be used in either space or terrestrial systems to give a high repeater directivity without requiring stabilized platforms or control of antenna orientation. An experimental verification of the basic principle is described.
The availability of coherent sources producing usable amounts of power in the optical frequency range has stimulated considerable research in optical communications. Devices such as oscillators, modulators, detectors, and ancillary apparatus having desirable characteristics exist and are being used to design and build prototype terminals. Two possible media are being studied and means are being sought to improve their performance. They are 1) through-the atmosphere propagation and 2) enclosed media with appropriate focusing and directing elements. Experimental optical transmission systems can readily be assembled with information capacities in a single RF channel comparable to those of microwave radio or millimeter waveguide. Such optical systems are not yet competitive for high reliability common carrier service because 1) long-distance transmission techniques of adequate reliability have not yet been advanced, and 2) optical repeater components are not yet competitive with their lower frequency counterparts. Some features characteristic of optical transmission systems are reviewed in this paper, along with a brief indication of the state-of-the-art for major components.
Microwave branching filters are required as integral parts of multi‐channel microwave radio relay systems. These filters must have characteristics which are difficult to attain if one attempts to extend familiar lower frequency techniques to the microwave region. A novel network configuration, through which currently anticipated requirements can be met without excessive difficulty, is described in this paper. In this configuration individual constant resistance channel dropping units are formed of appropriate assemblies of two hybrid circuits, two band reflection filters and two quarter wavelengths of line. An assembly of N channel dropping units in cascade then forms an N channel constant resistance branching network. The mechanical and electrical characteristics of a practical five channel branching filter of this type are described. As a result of experience with this prototype filter it can be stated with some safety that these requirements can be fulfilled with a network of this type. Experimentally observed impedance, insertion loss and phase characteristics were fully satisfactory. In addition the circuit appears to be flexible enough both electrically and mechanically to fulfill the various types of systems needs which may be encountered at branch points or when channels must be added or interchanged.
A preliminary study of a domestic satellite system is reported. Since the objective was to determine what might ultimately be possible, no attempt is made to relate system capacity to estimated needs; rather an effort has been made to conceive a system to carry the greatest possible amount of traffic. By making full use of modern rocket technology including the Saturn V class propulsion systems, highly directive multibeam antennas operating in the range from 15 to 40 GHz, interference resistant modulation methods, highly stabilized synchronous repeater platforms, and integrated solid state microwave repeater electronics, a very large communication capacity is obtained. For example, using 50 ground stations and 50 satellites operating in bands at 20 and 30 GHz, each 4 GHz wide, a total of 100 million voice circuits, or equivalent, can be provided.
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