Patent ID: 6621881
Filing Date: 2003-09-16
Classification: H04H

Abstract:
A decoder arranged to decode a binary bit of a code from a block of a signal transmitted with a time-varying intensity comprising:a selector arranged to select, within the block, (i) a reference frequency within the signal bandwidth, (ii) a first code frequency at a first predetermined frequency offset from the reference frequency, and (iii) a second code frequency at a second predetermined frequency offset from the reference frequency; a detector arranged to detect a spectral amplitude within respective predetermined frequency neighborhoods of the first and the second code frequencies; and, a bit finder arranged to find the binary bit when one of the first and second code frequencies has a spectral amplitude associated therewith that is a maximum within its respective neighborhood and the other of the first and second code frequencies has a spectral amplitude associated therewith that is a minimum within its respective neighborhood.