380 



BELL SYSTEM TECHNICAL JOURNAL 



the single pulses shown on Fig. 3. This change of magnitude, of course, can 

 spoil the cancellation of the ten unmodulated components at some frequency- 

 like c -\- 2v just as effectively as rotating them did in the case of the pulse 

 position modulated wave, thus ])r<)during a sj)ectrum component at that 

 frequency. 



As an example, the case will be taken where the modulating function is a 



0.4 



3 



h. 0.2 



5 



^o.sr 



Q 



3 



5^0,4 



< 



liJ 0.3 

 > 



IC 2C 3C 4C 5C 6C 



FREQUENCY, f, IN TERMS OF C (WHERE C =^) 



Fig. 10 — Comparative sjiectra of square wave and single pulse. 



sinusoid of frequency v. Then the change in width with modulation is 

 given bv the formula 



^L 



— k sin vl. 



Since c = lOr, the successive subsidiary pulse trains will be modulated an 

 amount! — 1^ = ^sin( 1-k — las ;;/ lakes on the values from 1 to 10. Thus 

 the spectra of these subsidiary pulse trains with ])ulses of length 2(L + 



