. The Bell System technical journal . 40 50 60 70 MODULATION IN PER CENT Fig. 8—Spectrum of pulse position modulated wave for case where the carrier frequencyC is 10 times the signal frequency v. quite equal in the two cases. In fact comparable upper and lower side-bands in the case of the pulse modulated wave shown on Fig. 8 are not 376 BELL SYSTEM TECHNICAL JOURNAL equal in absolute magnitude to each other. This lack of symmetry is dueto the fact that c is ()nl\ 10 limes 115 3 8 2 8 4 PEAK PHASE SHIFT IN RADIANS Fig. 9—Spectrum of phase modulated wave cos {ct + k sin vt) as function of p
. The Bell System technical journal . 40 50 60 70 MODULATION IN PER CENT Fig. 8—Spectrum of pulse position modulated wave for case where the carrier frequencyC is 10 times the signal frequency v. quite equal in the two cases. In fact comparable upper and lower side-bands in the case of the pulse modulated wave shown on Fig. 8 are not 376 BELL SYSTEM TECHNICAL JOURNAL equal in absolute magnitude to each other. This lack of symmetry is dueto the fact that c is ()nl\ 10 limes 115 3 8 2 8 4 PEAK PHASE SHIFT IN RADIANS Fig. 9—Spectrum of phase modulated wave cos {ct + k sin vt) as function of peak phaseshift k for values of ^ up to tt radians. One way of proving this is to go through the process of computing thec — V term in this pulse modulated wave just as ihc c-\-v term was computed SPECTRUM ANALYSIS OF WAVES 377 earlier. Since the frequency c— Iis 10% less thane, the unmodulated patternof the 10 subsidiary components, as shown on Fig. 7C, is the mirror image ofthat for c + ^ in 7A, for the first component is now 360° less 10% or 324°,and subsequent components are each retarded 36° with respect to the pre-vious one. When the pulse train is modulated the effect is similar to thecase for c -\- v and, for the same per cent modulation, the Vector patternof Fig. 7D is formed. The resultant in this case differs from that of 7Bin sign as well as in magnitude. The difference in sign comes from the factthat, since component 1 in 7A corresponds to componen
Size: 1364px × 1833px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1920, booksubjecttechnology, bookyear1
