ELECTRIC WAVE-FILTERS 



307 



ters are m = .7230 and ;;/' = .4134; the reason for this particular set 

 of vakies will be explained later. The transfer constant is the same as 

 that of an J/-type of parameter equal to the product mm' = .2989. 

 With other values of /;/ and ;;/' the image impedances Wik{m, m') and 

 W-ik{m, m'), which in the transmitting bands are pure resistances if 

 dissipation is neglected, can be given a variety of characteristics as is 

 apparent from their formulas. In fact their physical possibilities can 







WJ'^^ mitinBy 



zm(t-rnJV -r , 



Wouf^''^') 



zmii-Trv^) ^ih mO'TTV^) ^zh 



-o-/V\A^ 



mrrv-y 

 z ^?h 



M,(m) 



hK, 



ZTmn^ih 



Kjrn,7rv) 



TfFi 



''^zh 



Fig. 8— Mid-half sections of ilfilf'-type wave-filters. 



then be described by the following statement. In the range from 

 [/a,- = to — 1 the characteristic corresponding to the positive ratio 

 y = Wu{m, m')JR = R/W2k{'m, m') may have no maximum or mini- 

 mum, one maximum, or one maximum and one minimum; at Uk = 0, 

 y = I and at Uk = -1,3' = 0. All of these structures which have 

 the same value of the product g = mm', have the same transfer 

 constant. Thus, it is possible to keep the transfer constant fixed and 

 vary the image impedances. 



No structures of any higher order will be worked out here in detail 

 since for all practical purposes the .l/M'-types just considered will be 



