Abstract
An analysis is made of the transformations a graded signal undergoes if it is first encoded as a train of identical impulses, and subsequently decoded into a graded signal again. The case treated is that of a sinusoidally modulated input signal. As a paradigm for the encoding stage we employ the I.P.F.M. (Integral Pulse Frequency Modulator). An exact solution for the times of occurrence of output impulses is offered. This solution permits us to treat some curious beat phenomena that are found if an I.P.F.M. is excited with a frequency that is in a nearly rational ratio to the steady state output frequency of the I.P.F.M. It is shown that an I.P.F.M. is a phase sensitive device. In order to avoid a phase sensitivity of the complete signal transmission link, we consider a group of encoders feeding their signals into the decoding stage. For such a group it is meaningful to talk about the momentaneous interpulse interval. We derive the interval histogram and the spectral decomposition of this momentaneous interval. It is shown that the spectrum is very different from the spectrum derived by Bayly (1968) of the output signal of a single I.P.F.M. Two extreme types of decoding mechanisms lead to different transfer functions for the complete signal transmission link, both of which are shown to be of some neurophysiological relevance.
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The authors are indebted to the Netherlands Organization for the Advancement of Pure Research for financial support of part of this investigation.
We thank Prof. Dr.M.A.Bouman for his critical remarks on the original manuscript.
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Koenderink, J.J., van Doorn, A.J. Event train decoders with many inputs, pulse density versus momentaneous frequency. Kybernetik 13, 215–222 (1973). https://doi.org/10.1007/BF00274886
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DOI: https://doi.org/10.1007/BF00274886