| 摘要 |
Methods for digitally demodulating a complex modulation for transmitting different parameters, comprising baseband filtering (201) of the input signal, and complex demodulation (202) of a first subcarrier at frequency Fp to obtain a correction signal after squaring (207), whereafter the input signal is demodulated around a frequency which is exactly twice the first demodulation frequency in order to obtain output signals having a frequency error relative to 2Fp, and said frequency error is corrected by multiplication (213) by the previously obtained frequency correction signal. The signal thereby corrected is then filtered (214, 215) at a frequency under 1 Hz to obtain a signal providing the phase error at frequency 0, i.e. that of the subcarrier at 2Fp, and allowing phase correction of the previously frequency-corrected signals to obtain two complementary signals which are transmitted by quadrature modulation around frequency 2Fp. Said methods allow demodulation of omnidirectional and bipolar signals from an underwater monitoring buoy.
|
