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BKI.L SVSTK.H fKC/IMCAL JOURNAL 



pulse of the same amplitude. The time per pulse is taken to be T" and the 

 duration of the pulse at half height is T'. If T" is put equal to T the ratio 

 of the PPM bandwidth to the PCM bandwidth is T/T'. The time shift 



A) 



b VALUES 



(including o) 



MAXIMUM PEAK INTER- 

 FERENCE (INCLUDING 

 3-DECIBEL ALLOWANCE] 

 1 



2V2(b-t} 



INTERFERENCE slopE=A 

 SLOPE OF PULSE ' 2T' 



CASE 2 



INTERFERENCE = 



2V2 (b-i) 



INTERFERENCE=0.353 (9 DB) 



<y= 



2T' 



2 7r-V2 ( b - 1 ) 



T"=T'(2^f) 



s- 



2T' X 0.353 

 77 



T' 



VF^r 



r"=T'[=.^ 



ND 

 MAKE THEM EQUAL, THE BANDWIDTH RATIOS BECOME 



7T 

 IF WE TAKE THE TIME PER PULSE TO BE T AND T" AND 



3,^(^ 

 Fig. 18 — Comparison of cjuanlized PAM with quantized PPM. 



produced by peak interference is represented by d. Our system is marginal 

 when the smallest quantized step produces a shift of 2-\/2 8. The peak time 

 shift produced by a signal is then (b — l)2\/2 5. Two cases are considered. 

 In one the PPM system operates in the presence of the same peak inter- 

 ference as in the PCM case. The bandwidth ratio is 2.64. The other case 



