Patent ID: 6763106
Filing Date: 2004-07-13
Classification: H04M

Abstract:
A signal detector for detecting at least a first signal having a first frequency and a first minimum duration, comprising:a transform unit adapted to receive a plurality of frames of time domain input samples including a first frame of time domain input samples at a sampling frequency and generate at least a first frequency energy value for the first frame based on at least a first subset of the time domain input samples, the first subset of the first frame having a width of less than about one half of the first minimum duration, wherein the transform unit is further configured to and generate a plurality of frequency energy values corresponding to the plurality of frames; and an energy level threshold unit adapted to compare the first frequency energy value to a threshold energy value to determine the presence of the first signal, wherein the energy level threshold unit is adapted to provide a frame detection indicator based on the comparison of the first frequency energy value and the threshold energy value, the frame detection indicator designating a detection in response to the first frequency energy value being greater than the threshold energy value and a non-detection in response to the first frequency energy value being less than the threshold energy value, the energy level threshold unit being further adapted to compare the plurality of frequency energy value to the threshold energy value to determine a plurality frame detection indicators; a guard time check unit adapted to receive the plurality of frame detection indicators and provide a valid detection indicator in response to at least two consecutive frame detection indicators designating detection and the guard time check unit is adapted to provide the valid detection indicator in response to at least three consecutive frame detection indicators designating non-detection prior to the at least two consecutive flame detection indicators designating detection.