COUPLED HELICES 



175 



5.0 



7a 



2.0 2.5 3.0 



/Oo <3 COT ^, 



3.5 



4.0 



4.5 



5.0 



Fig. 4.1.4 — The radial propagation constants associated with the transverse 

 and longitudinal modes on coupled coaxial sheath helices given as a function of 

 /3oa cot yp\ when 6/a = 2.0. 



III. COMPLETE POWER TRANSFER 



For coupled heli.x applications we require the coupled helix parame- 

 ters to be adjusted so that RF power fed into one helix alone will set up 

 the transverse and longitudinal modes equal in amplitude. For this 

 condition the power from the outer helix will transfer completely to the 

 inner helix. The total current density can be written as the sum of the 

 current in the longitudinal mode and the transverse mode. Thus for the 

 inner helix we have 



-i&li 



J a = Jate-'''' + Jate 



.-J^<2 



(35) 



