| 摘要 |
A low cost RF link is implemented by summing a wideband amplitude noise dither signal with a band limited RF signal. The summed signal is then amplitude limited. The output of the limiter can be applied directly to the digital fiber optic transmitter. At the remote end of the link, the original signal can be recovered by removing the noise dither signal. This can easily be accomplished with a narrow band filter centered on the original signal. This system uses the same optical fiber transmitters and receivers as the traditional system, but eliminates the need for the ADCs, DACs and parallel/serial format conversion hardware. Adding amplitude dither to the signal mitigates the intermodulation distortion that would normally be associated with the non-linear operation of amplitude limiting. In this way, multiple narrow band signals can be transmitted down a single fiber using digital fiber optic transmitters and receivers without distortion due to intermodulation. The technique of the invention has application in commercial systems requiring low cost transmission of analog narrow band voice or data signals over a digital fiber optic link. The inherent EMI/RFI immunity of optical fiber would make this especially attractive for industrial applications.
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