Digital Marine Electronics Corporation

Other

Mark J Giubardo

Sheldon B Michaels

Jeffrey Scott Morris

A scanning receiver channel identification apparatus and method comprising a scanning receiver, means for generating annunciations to be associated with the channels to which the scanning receiver is tuned, means for associating annunciations with the channels to which the scanning receiver is tuned, and means for incorporating the annunciations into the detected output of the scanning receiver for the purpose of overcoming the limitations imposed by conventional alphanumeric displays of the channel to which the receiver is tuned.

Scanner with audible identification of tuned channel

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.

Radio receiver with automatic interference cancellation

Undesired, interfering narrow band received signals in a Loran-C receiver are automatically rejected and the resulting distortion of the received Loran beacon signals caused by this rejection is automatically compensated for. The received Loran-C beacon signals in the band 90 to 110 KHz are fed through a narrow band, variable reject filter that rejects the undesired signal and is controlled by a feedback circuit in response to an interference detector in the receiver, so that the reject filter is automatically set at the interfering signal, rejecting it. Meanwhile, distortion of the received Loran beacon signals caused by the rejection is compensated for by an automatic circuit that varies a delay and add circuit in the Loran receiver to compensate for the distortion.

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Chelmsford, MA, United States of America

Mark J Giubardo