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US 4,072,950 AGranted
LF/MF navigation system
OwnerEric R. Swansoninventor
Life of this patent
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Abstract
A navigation aid comprises two transmitters transmitting signals in the LF/MF range (250 kilohertz-490 kilohertz) and a receiver indicator for receiving each of the transmitted signals, translating them to a common frequency, and indicating the phase difference at any given position. Frequency stablizing means are coupled to each transmitter to stabilize the frequency of each transmitted signal and to prevent the differential frequency error from exceeding a selected limit.
Claims12
Apparatus for a navigation system employing a hyperbolic phase grid, said apparatus comprising:
- a. means for transmitting a plurality of signals having different frequencies in the LF/MF range each of said signals being transmitted from a different and known location;
- b. receiver indicator means receiving a first and a second of said transmitted signals for translating said first signal from its transmitted frequency to a first frequency comprising the sum of a common frequency and a first residual frequency error, for translating said second signal from its transmitted frequency to a second frequency comprising the sum of said common frequency and a second residual frequency error, and for indicating the phase difference between said first and second signals, the quotient of the absolute value of the different between said first residual frequency error and said second residual frequency error and said common frequency not exceeding a selected limit.
Dependencies are inferred from the claim text.