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Abstract

An improvement to the present system of Global Positioning System of satellites and ground stations, adding the capability of transmitting and receiving telecommand information, when required, to the current Navigation information. Three alternate embodiments are proposed. The first approach utilizes a spread-spectrum transmission of the command message, requiring few added components to the transmitter, and additional despread components to the receiver to extract the telecommand message. The second approach is simpler. Here the telecommand message is transmitted on a single frequency signal which is not modulated by a spreading code. The additional hardware in the receiver is a simple detector and demodulator. The third approach is based on redefining portions of the present GPS Navigation message to include telecommand information bits. No additional transmitter components are required, and only a command demultiplexer is added to the receiver. Advantages of the invention include a great reduction in required power, volume and weight of satellites and unmanned vehicles, as well as greater control and security of command signals.

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First Claim