A COUPLED RESONATOR REFLEX KLYSTRON 



721 



V is increased from zero to some finite value, a process actually occurring 

 in a reflex klystron during the build-up of oscillations. The amplitude 

 of Ye will then be of the form 2Ji{x)/x and will decrease according to the 

 Bessel function plot of Fig. 2. 



For an infinitesimal or zero RF gap voltage the electronic admittance, 

 now referred to as "small-signal" electronic admittance, Yes , may be 

 derived from equation (2.1) as. 



Ye\ 



^ 7. 



2F„ ^' 



(2.2) 



When presented in the complex admittance (i.e., g-h) plane, expression 

 (2.2) assumes the form of a geometric spiral as shown in Fig. 4. Each 

 point on the spiral corresponds to a particular value of d and, since 6 

 is a function of the repeller voltage only, to a particular value of Vr . 

 We also note that for some values of the conductance component of 

 Yes is negative while for others it is positive. Thus, there is the possi- 

 bility of generation of RF energy for values of Yes adjusted by means of 

 the repeller voltage to fall on the left-hand half of the admittance spiral 

 while energy is absorbed for values of Yes having a positive conductance 

 component. As the RF gap voltage, V, builds up from zero to its final 

 value the magnitude of the electronic admittance shrinks along a radius 



Fig. 2. Bessel function plot showing the relative variation of the amplitude 

 of the electronic admittance (ordinate) as a function of RF gap voltage (abscissa) 

 i with repeller drift angle held constant. 



