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Experiments on the Timing of Regenerative Repeaters

01 November 1958

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Three other papers 1 · 2 · 3 appearing in this issue of the Bell System Technical Journal discuss and analyze the timing of regenerative repeaters. It is the purpose of this paper to describe some experiments performed on repeaters of the same general type to determine their performance in the presence of random noise. Although our interest is largely in microwave systems, the repeaters for such systems are relatively complicated and expensive. Thus, it is impractical to build a long chain of them expressly for experimental purposes. The recovered timing information is at baseband frequency in a carrier system as well as in a baseband system. For these reasons, we built a chain of baseband repeaters to simulate, as nearly as possible, the microwave repeaters of interest. A pulse-repetition frequency of 10 mc was chosen. T h e experiments had two objectives: first, to determine the effects of noise in producing pulse errors through its action on the timing circuit and second, to determine the effects of noise in producing time or phase deviations of signal pulses, as discussed in Refs. 1, 2 and 3. From these results, we hope to determine w h a t characteristics the timing circuits must have in order to meet the over-all system requirements. T h e experiments concern only self-timed repeaters. It was found that, with a fixed pulse pattern and the simple timing circuits employed, the number of errors produced by the effects of noise upon timing was negligibly small in comparison to the number produced by other effects of noise.