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:
Mar. 14, 1989
Filed:
Oct. 31, 1985
Mark J Giubardo, Pepperill, MA (US);
Digital Marine Electronics Corporation, Acton, MA (US);
Abstract
Undesired, intefering narrow band received signals in a radio receiver are automatically cancelled by a cancellation system including a variable narrow band pass filter that separates a sample of the undersired signals from the total received signal, reverses phase of the sample and combines it with the total received signal, substantially cancelling the undesired signals therein. In a Loran-C receiver, desired beacon signals in the band 90 to 110 KHz are received aling with narrow band interfering (undesired) signals. During a 'cancel mode,' a narrow band of the total received signal is sampled by a variable narrow band pass filter and the narrow band sample is reversed in phase and then combined with the total received signal to cancel the undersired signals therein. The frequency of the variable narrow band pass filter is controlled by a pass filter control signal that is established during a 'search mode' as the control signal at which a high (or maximum) interference signal is detected in the pass filter output. During the cancel mode, that control signal sets the frequency of the variable narrow band pass filter causing the interfering signal to be cancelled. Thus, interference detection during the search mode is accomplished using the same variable, narrow band pass filter as used during the cancel mode to cancel the interference.