1474 THE BELL SYSTEM TECHNICAL JOURNAL, NOVEMBER 1957 



An analysis of this point is given in Appendix I. It is concluded that 

 while there may be long range possibilities in baseband transmission, it 

 requires more study, and it will not be considered further in this paper. 



3.2.2 AM Carrier Transmission 



The simplest of this type is double sideband transmission, as illus- 

 trated by the full line of Fig. 5(b). 



A comparison of the susceptibility to noise of this arrangement, with 

 that of baseband transmission, is considered in the next section. 



A further consideration required is susceptibility to nonlinearity in 

 the facility. Second order modulation leads among other things to a recti- 

 fication of the signal back to baseband. This is indicated by the dotted 

 lines in Fig. 5(b). After such rectification of the signal by the facility, it 

 is impossible to separate any overlapping portions of the signal between 

 the baseband and lower sideband. Some o^'erlap is shown. This inter- 

 ference was first considered in telephotography^' and is known as "Ken- 

 dall effect." 



The possibility of Kendall effect may be eliminated insofar as second 

 order modulation is concerned by mo^'ing the carrier frequency high 



LJJ 



a 



D 



_l 

 Q- 



5 

 < 



X 



NOMINAL 



EFFECTIVE 



BAND 



(d) 



GUARD 

 BAND 



-^ SWING l«— 

 FREQUENCY — 



ROLL-OFF 



Fig. 5 — Spectra of signals with various modulations. 



