Title: Self learning monitor for VLF wave propagation

Abstract: A monitor for notifying a vehicle using VLF navigation of an abnormal conion of VLF wave propagation. Sensing means, including an antenna, oscillator, IF mixer, and phase tracker is provided to periodically sense changes in the phase angle of a VLF wave received by the monitor, and to couple a succession of values of an updating quantity into a data processing means, each value corresponding to a sensed amount of phase change. The data processing means learns what comprises a normal condition of VLF wave propagation by averaging successive values of the updating quantity, and provides notice of an abnormal condition whenever a received value of the updating quantity varies from the previously computed average by an amount in excess of a preselected criterion.

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Inventors: Swanson, Eric R. (San Diego, CA, US)

Application Number: 695614
Filing Date: 1976-06-14
Publication_date: 1977-07-26
Assignee: The United States of America as represented by the Secretary of the Navy (Washington, DC)
Primary Class(es): 701/207 702/199
Other Classes:
US Patent Ref:

2767914	Oct, 1956	Merrill et al.	235/151.
3151237	Sep, 1964	Hrabak	235/151.
3464549	Sep, 1969	Armbruster	235/151.
3549875	Dec, 1970	Goldman et al.	235/151.
3936828	Feb, 1976	Muesse et al.	235/151.

Other Refs:
Primary Examiner: Ruggiero, Joseph F.
Assistant Examiner:
Attorney: Sciascia; R. S., Rubens; G. J.