Transdigitizer for relaying signals from global positioning system (GPS) satellites
Patent 4622557 Issued on November 11, 1986. Estimated Expiration Date: 
October 31, 2004. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
October 31, 2004. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent References 3126545 3241137 3378837 3384891 Quadraphase modulator Coded coherent transponder System for determining the location of an airborne vehicle to the earth using a satellite-base signal source Navigation system and method Patent #: 4445118 InventorAssigneeApplicationNo. 06/666784 filed on 10/31/1984US Classes:342/357.09, With transmission of location-indicative information to or from a remote station342/42RADAR TRANSPONDER SYSTEMExaminersPrimary: Blum, Theodore M.Assistant: Gregory, Bernarr E. Attorney, Agent or FirmInternational ClassesG01S 5/02 (20060101)G01S 5/00 (20060101) G01S 5/14 (20060101) AbstractThe reception, downconversion and retransmission of the 1575.42 MHz Global Positioning System (GPS) satellite signal is accomplished by the following. First, an RF stage comprising of an antenna, filter and preamplifier receiver, filters and amplifies the 1575.42 MHz signals. Following the RF stage, a converter stage, consisting of a bandpass filter, converts the GPS signal to a lower frequency. Then, an Intermediate Frequency (IF), comprising an IF amplifier, multiplier, bandpass filter and limiter further amplifies and filters the signals to remove the effects of the signals. A final downconverter converts the signal to a base band frequency and in a zero crossing detector the signal is amplified and 1 bit quantized. Finally, a local oscillator controls a frequency synthesizer to latch the signal from the zero crossing detector in a flip flop, which in turn is used to control a quadraphase monitor, whose signals are amplified and transmitted out the transmit antenna.Other References
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