Transponder for a moving vehicle tracking system
First Claim
1. In a moving vehicle tracking system, a transponder mounted on the moving vehicle for receiving tracking signals transmitted thereto from a base station and for retransmitting coherent reply signals to the base station, said transponder comprising:
- (a) a plurality of receivers each having a separate antenna affixed to the vehicle in spaced relation from the other antennas, each receiver providing, upon reception of a tracking signal, an output signal at a predetermined frequency and a phase determined by the path length from the base station to the specific receiver antenna;
(b) combiner means coupled to each of said receivers for receiving the output signals therefrom and combining the output signals into a single continuous control signal at the predetermined frequency and a phase determined by the output signals applied to said combiner means; and
(c) a transmitter coupled to said combiner means for receiving said control signal and retransmitting to the base station a reply signal coherent with the received tracking signal.
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Accused Products
Abstract
In a Doppler (frequency shift) spacecraft tracking system, a transponder mounted on the spacecraft including, two or more, receivers connected to spaced-apart antennas for receiving an RF tracking signal transmitted from a ground based station regardless of the attitude, or position, of the spacecraft. The intermediate frequency (IF) signals from the receivers are combined to provide a continuous third IF signal at the proper frequency and at a phase dependent upon the signals received, which third signal is utilized to control a transmitter for retransmitting coherent reply carrier frequency signals to the ground based station.
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Citations
5 Claims
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1. In a moving vehicle tracking system, a transponder mounted on the moving vehicle for receiving tracking signals transmitted thereto from a base station and for retransmitting coherent reply signals to the base station, said transponder comprising:
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(a) a plurality of receivers each having a separate antenna affixed to the vehicle in spaced relation from the other antennas, each receiver providing, upon reception of a tracking signal, an output signal at a predetermined frequency and a phase determined by the path length from the base station to the specific receiver antenna; (b) combiner means coupled to each of said receivers for receiving the output signals therefrom and combining the output signals into a single continuous control signal at the predetermined frequency and a phase determined by the output signals applied to said combiner means; and (c) a transmitter coupled to said combiner means for receiving said control signal and retransmitting to the base station a reply signal coherent with the received tracking signal. - View Dependent Claims (2, 3)
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4. In a moving vehicle tracking system having a transponder mounted on the moving vehicle for receiving tracking signals transmitted thereto from a base station and for retransmitting coherent reply signals to the base station, a method of providing coherent reply signals comprising the steps of:
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(a) receiving a transmitted tracking signal with first and second receivers, each receiver providing an output signal at a specific frequency and a phase determined by the path length from the receiver to the base station; (b) combining the output signals from the receivers to provide a continuous control signal at the specific frequency and at a phase dependent upon the output signals present; and (c) utilizing the continuous control signal to control a transmitter for transmitting coherent reply signals. - View Dependent Claims (5)
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Specification