Institute for Telecommunication Sciences
the research laboratory of the National Telecommunications and Information Administration

David Middleton; Arthur D. Spaulding

Abstract: The purposes of this study (and subsequent efforts) are several: (1), to extend earlier models of the FM reception process, to include as much II "realism" – i.e., non-ideality of both the linear and nonlinear elements of the typical FM receiver – as possible, and still retain analytical and computational feasibility; (2), to examine explicit cases of interference produced by one or more deterministic signals; and (3), with such specific examples, both to provide insights into the distortion effects generated by the nonlinear interactions of the various (desired and undesired) signals in the receiver and to present the analytical framework of the instantaneous outputs required in any (subsequent) fully statistical treatment, where now the interference (e.g., "noise") is noticeably nongaussian. In addition, these deterministic models may also provide useful structures for simulation studies. The instantaneous receiver outputs are obtained for the following receiver models, (A), and interference "scenarios", (B): for (A): (I) "superclippinq: and an ideal discriminator; (II), no limiting and ideal discriminator; III, "superclipping" and a non-ideal IV, no limiting and a non–ideal discriminator. For (B), with each (A), we consider explicitly the cases of: (i), one cochannel interfering signal; (ii), one adjacent channel interferer, and (iii), M symmetrical interferers (M = 1, 5). Also included are the mean and mean-square outputs. All the above are obtained here for idealized (i.e. sufficiently wide-band) RF-IF receiver stages, which are essentially linear under this condition. The results are illustrated with cases for selected, typical parameters of the combination of the interference-receiver structure. For other combinations, the appropriate computer programs are included in the Appendix.

Keywords: interference; FM reception; receiver models; multiple interferers; baseband output waveforms

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