| 摘要 |
A synchronizer (10) for frequency division multiple access signals (FDMA) permits synchronization on board a communications satellite without feedback to a multitude of ground-based user stations. Fourier transform processors (12, 13) sample the FDMA signal at half the FDMA baud rate and provide a series of pulses. Frequency translators (14, 15) frequency translate each pulse to frequency align across channels the content of one respective complete symbol segment to be isolated by bandpass filters (16, 17). A demodulator 18 provides a synchronized time division multiplexed output. Two channels alternately sample the FDMA signal to obtain full decoding. A synchronization processor (20) is provided to ensure that the pulses undergo appropriate frequency translations. The synchronization processor detects TDM pulse amplitudes (at 22) and compares them (at 24) to obtain a discriminate which sets a translation frequency (at 26) for each FDMA channel. A frequency synthesizer (28) outputs this translation frequency with a dither superimposed thereon. This forms a phase lock loop for attaining and maintaining a proper translation frequency for each channel.
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