510 



BELL SYSTEM TECIIXICAL JOi'RXAL 



pulse is inversely proportional to the signal bandwidth. The time available 

 for modulating the pulse position is equal to the channel time minus the 

 pulse duration. The combination of these factors leads to the PPM "slicer 



80 

 75 

 70 

 65 



_i 



LU 



5 55 



O 



lU 



O50 



z 



^45 





4-^ 



JiL 



Fig. 8 — Time allotments in pulse position modulation 



2f -■ 



J 



Nfr 





5 



65 5 



:2o| \ 1 — vj — h- 1 1 1 — I i j--^; ;:]^^ — t — 1 1 ^ 1 ""^° 



' ?^r^^~^^^^f^^ '' I 



^^^ ^ 90 0- 



-5 -==^ 95 > 



UJ 



O 



tOOuj 



10 20 40 60 60 100 200 400 600 1000 2000 4000 10,000 °- 



RADIO SIGNAL BANDWIDTH IN MEGACYCLES PER SECOND 



Fig. 9 — PPM-.\M; performance with respect to tiuctuation noise. Relations between 

 bandwidth, power, and audio signal-to-noisc ratio for 1000 4-kc channels. 



advantage" which, when applied to the r-/ pulse-to-noise ratio, gives the full 

 load audio tone-to-noise ratio in each channel. Details of this calculation 

 and others pertaining to various pulse systems are included in Appendix I\'. 



