| 摘要 |
An encoder is arranged to add a binary code bit to a block of a signal by selecting, 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. The spectral amplitude at each of the first and second code frequencies may be respectively modified to be a maximum in a first neighborhood of frequencies extending about the first code frequency and a minimum in a second neighborhood of frequencies extending about the second code frequency. Alternatively, the phase of a signal component at one of the first and second code frequencies may be changed relative to a reference signal component.
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