| 摘要 |
In a multiple site radio frequency simulcasting R.F. transmission system, data provided via inter-site communications links (L1, L2, etc.) from a control point to the R.F. transmitter sites exhibits random time delay skew because multi-phase modems recover clock signals from an arbitrary one of multiple phases. The output data streams of the modems are temporarily stored at the sites in memory buffers for temporal alignment for simultaneous R.F. transmission. The memory buffers at each site are periodically resynchronised on a continual basis by a universal "resynch" circuit to maintain optimum simulcast system performance. A 9600 bps data clocking reference and a low frequency data "gating" (timing) signal required for performing a periodic "resynch" operation are derived separately from a common satellite reference signal acquired by using a GPS (global positioning satellite) receiver at each simulcast system site. A resynch operation is periodically performed on a continuing basis separately by each simulcast system site and the distributed multi-site broadcast data stream is aligned using the resynch reference tones derived from the received GPS signal. |
