The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jan. 21, 1997
Filed:
Jul. 17, 1995
Richard A Fitts, Monroe, CT (US);
Northrop Grumman Corporation, Los Angeles, CA (US);
Abstract
A communication system is provided for identifying the position of aircraft in a surveillance area. The communication system includes a dual-frequency interrogator which produces two signals at different frequencies. These signals are transmitted over a narrow beam, scanning antenna, the antenna being located within the surveillance area. A transponder is provided on the aircraft with an auxiliary antenna assembly tuned to a frequency equivalent to the difference between the dual frequencies. The transponder produces a signal containing aircraft identification information. A processing unit is co-located on the aircraft with the transponder to receive the two signals transmitted by the interrogator and produce a signal equivalent to the difference between those signals. The difference signal produced by the processing unit is coupled with the transponder and is used to identify the position of aircraft on the ground. A stationary antenna and receiver are tuned to the frequency of the transponder response and receive the transponder response. The stationary receiver transmits information to a position-estimating computer regarding the time of arrival of the aircraft signal. The position-estimating computer also receives information from the interrogator regarding the time of interrogation and the position of the antenna at the interrogation time. The position-estimating computer processes this information to identify the position of the aircraft on the airport surface.