POTENTIAL ANALOGUE METHOD OF NETWORK SYNTHESIS 



329 



fication. The difficulty is readily resolved, however, if we note that the 

 charge on the shield is symmetric about the w-axis, and that the charges 

 on each half of the shield produce the same potential on the imaginary axis. 

 Hence the gain will be unchanged, if we use only the left half of the shield 

 and double the charge. 



Even if the shield is not symmetrical about the oj-axis we can still transfer 

 the positive charges on the right half of the plane to their mirror images 

 in the axis without changing the value of the potential on the axis. This 



REAL p 



(a) SYMMETRICAL 



REAL p 



.--^^ 



REAL p 



// 

 U 



-X— X 



(b) DISSYMMETRICAL '^'^"xJ^ 



REAL p 



Fig. 7 — Lumped charge distribution for a given contour; (a) symmetrical, (b) dis- 

 symmetrical. 



would give us a charge distribution over two separate contour branches, 

 as in Fig. 7, and would thus increase the network complexity. This explains 

 the desirabiUty of using the type of shield which is symmetrical relative 

 to each axis. 



So far we have considered conductors in the absence of external charges 

 (except at infinity). If the network is to have points of infinite loss at certain 

 finite frequencies we must have negative charges outside the shield. Fig. 8. 

 These charges alter the charge distribution on the shield, but the potential 



