THEORETICAL FUNDAMENTALS OF PULSE TRANSMISSION 



767 



structure departures a(w) in the transmission characteristic and luMice 

 the coefficients Oi , 02 ■ ■ • a,,, • • • will l)c small. 



In the above representation .lo(w) can also he refi;arded as th(> ampli- 

 tude characteristic of a terminal network or as the frequency spectrum 

 of a pulse applied to a transmission system witfi an amplitude charact- 

 teristic /(oj) = 1 + «(co). 



In a Fourier series analysis of the deviation in the amplitude charac- 

 teristic, the fimdamental period of the amplitude variation would be 

 selected so that there is one complete cycle betAveen — coi and a;i , the 

 cutoff frequency, in which case ojit = tt or 



r 

 T = — 



COi 



This is the interval between pulse echoes when the amphtude charac- 

 teristic is represented by (8.01). It is identical with the interval ri given 

 by (3.02) at which pulses can be transmitted without mutual interfer- 

 ence with a constant amphtude transmission frequency characteristic. 



A/Aq = i + oc(a») 



Aq = NOMINAL OR IDEAL 

 CHARACTERISTIC 



: ACTUAL CHARACTERISTIC 



FREQUENCY ^^MAX 



(a) TRANSMISSION FREQUENCY CHARACTERISTIC 



^-Pq = NOMINAL OR IDEAL 

 ^^" IMPULSE CHARACTERISTIC 



* --P = ACTUAL IMPULSE CHARACTERISTIC 



TIME 



AP= P-Po'' 

 (b) IMPULSE TRANSMISSION CHARACTERISTIC 



Fig. 30 — Fine structure imperfections in transmission frequency cliaracteristic 

 and resultant i)rolongation of impulse characteristic. 



