| 摘要 |
An apparatus for phase angle demodulation. The apparatus functions as a highly-linear angle-modulation demodulator and is particularly useful for seismic streamers comprising very-large arrays of optical hydrophones. The apparatus includes a demodulator and a processor in which the demodulator contains a signal input and a reference input. The apparatus is configured such that a phase modulated signal having a carrier frequency is connected to the signal input, and a reference signal is connected to the reference input. A difference frequency is defined as the non-zero difference in frequency between the reference signal frequency and the carrier frequency. The processor filters the output from the demodulator in order to separate the phase demodulated signal from the difference frequency.The phase modulated signal can be any form of angle modulated signal such as a Frequency Modulated ("FM") signal, a Phase Modulated ("PM") signal, or a Phase Generated Carrier ("PGC") signal. When demodulating a phase-generated calTier signal, it can be advantageous to combine the output from more than one demodulator each driven by a reference signal with different frequencies from each other. At least one of these reference frequencies is not harmonically related to the fundamental carrier frequency of the phase modulated signal. |
