Patent ID: 6504870
Filing Date: 2003-01-07
Classification: H04H

Abstract:
An encoder arranged to add a binary bit of a code to a block of a signal having an intensity varying within a predetermined signal bandwidth comprising:a selector arranged to select, within the block, (i) a reference frequency within the predetermined signal bandwidth, (ii) a first code frequency having a first predetermined offset from the reference frequency, and (iii) a second code frequency having a second predetermined offset from the reference frequency; a detector arranged to detect a spectral amplitude of the signal in a first neighborhood of frequencies extending about the first code frequency and in a second neighborhood of frequencies extending about the second code frequency; and, a bit inserter arranged to insert the binary bit by increasing the spectral amplitude at the first code frequency so as to render the spectral amplitude at the first code frequency a maximum in the first neighborhood of frequencies and by decreasing the spectral amplitude at the second code frequency so as to render the spectral amplitude at the second code frequency a minimum in the second neighborhood of frequencies.