TRANSMISSION LINES 



295 



itself arithmetically to that produced by the other sideband. It will 

 be noted that this desirable phase characteristic has been achieved 

 closely in the characteristics shown. If, in addition, the attenuation 



14 18 22 26 30 34 38 42 46 



FREQUENCY IN KILOCYCLES PER SECOND 



Fig. 6 — Transmission and phase characteristics of band filter. 



loss in the filter is adjusted so that the sum of the regular and vestigial 

 sideband amplitudes corresponding to the low music frequencies is 

 substantially constant and equal to the amplitude of the frequencies at 

 midband, the desired flat transmission characteristic is assured. 



As was noted previously, this action can be carried out only if the 

 phase angle of the receiving carrier is properly related to that of the 

 sideband frequencies and, in turn, to the carrier applied to the modu- 

 lator at the transmitting terminal. The curves shown in Fig. 7 



V) 



_i 



CQ 



LlJ 

 Q 

 2-4 



ai 

 o 



30 



100 



500 1000 5000 



FREQUENCY IN CYCLES PER SECOND 



10,000 20,000 



Fig. 7 — Over-all transmission characteristics as a function of the phase relation of 



the receiving carrier. 



