| 摘要 |
An encoder adds a binary code bit to a block of a signal by selecting a reference frequency within a predetermined bandwidth, a first code frequency having a first predetermined offset from the reference frequency, and a second code frequency having a second predetermined offset from the reference frequency. The spectral amplitude of the signal at the first code frequency is increased to render it a maximum in its neighborhood of frequencies, and the spectral amplitude of the signal at the second code frequency is decreased to render it a minimum in its neighborhood of frequencies. Alternatively, the phase of the portion of the signal at one of the first and second code frequencies whose spectral amplitude is smaller may be modified so as to differ from the phase of the reference signal component within a predetermined amount. A decoder decodes the binary bit.
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