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BELL SYSTEM TECHNICAL JOURNAL 



equal power but of random phase. The signal generators e^A and e^s 

 are assumed to fade according to the equations shown beneath the 

 diagram. They represent the carrier amplitude but since fading is 

 assumed to be essentially non-selective in each branch they also repre- 



TIME.t — — ► 



6 



"14 



U) 



O 

 1 



TIME.t- 



CIRCUIT USED FOR ANALYSIS 

 OF DIVERSITY ACTION 



COMMON GAIN CONTROL 



IMPROVEMENT CURVES 

 POWER VOLTAGE 



AUTOMATIC GAIN 

 CONTROL LINK 



180° 

 ASYNCH. 



ejA = Vl + 2 X 0.8 COS (2tT t/T + e,) + (0.8)^ 

 esB= Vl + 2 X 0.8 COS (2lTt/T + Bj) + (O.B)* 



Fig. 38 — Graphical analysis of diversity action as it relates to signal-to-noise ratio. 



sent the side bands. This type of fading might result from inter- 

 ference between two waves of small relative delay whose amplitude 

 ratio is 0.8, such a pair being received by each branch. The auto- 

 matic gain control is assumed to be perfect; i.e., the audio output, £s, 

 is maintained constant. 



