October 1989 | NTIA Technical Report TR-89-250
Power Spectral Densities for Selected Digital Phase–Continuous MFSK Emissions
Martin Nesenbergs; Darren L. Smith; L. Thomas Jones
Abstract: This report is a brief outline and a catalog o full power spectral densities for certain M–ary frequency shift keying waveforms. Spectral equations are displayed in graphical form for easy visualization . The spectra pertain to real signals centered on their carrier frequencies. The selected waveforms are all phase–continuous with no symbol–to–symbol overlap. The number of keying waveforms, M, varies from 2 to 8. The modulation index, k, is typically 2, and only occasionally assumes values of 1 and 4. In all 11 cases considered one encounters discrete line spectra. The relative power contained in the discrete spectrum turns out to be 1/M for regular square waveforms with no dependence between successive symbols and somewhat larger for the other cases considered here. The asymptotic behavior of the continuous spectral component agrees with the theoretical predictions for very large frequency deviations. Specific waveform shapes include square (or rectangular) pulses, sine–pulses, raised cosine pulses, and squared raised cosine pulses. The concluding sections of the report cover two special systems of recent practical interest . They are the M=4 and k=2, alternating frequency, format of Rockwell/Collins and the M=8, k=2, scheme developed by MITRE and Harris Corporations.
Keywords: asymptotics; continuous and line spectra; M-ary frequency shift keying (MFSK); phase-continuous waveforms; spectral densities
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Disclaimer: Certain commercial equipment, components, and software may be identified in this report to specify adequately the technical aspects of the reported results. In no case does such identification imply recommendation or endorsement by the National Telecommunications and Information Administration, nor does it imply that the equipment or software identified is necessarily the best available for the particular application or uses.