A COUPLED RESONATOR REFLEX KLYSTRON 



723 



from resonance. Also, the frequency deviation required to bring about 

 a given change in susceptance is inversely proportional to both C and Q. 



2.3 Equivalent Circuit of Single Resonator Reflex Klystron 



We saw that the presence of a bunched electron stream between two 

 closely spaced grid planes gives rise to an electronic admittance the 

 properties of which were discussed earlier. Suppose we now let these 

 grids become part of a re-entrant cavity so that they form the boundaries 

 of the interaction space. This will make them elements of significance and 

 common to both the electron stream and the passive circuit admittance. 

 As far as the electron stream is concerned the grids become the terminals 

 across which the electronic admittance, Ye , is developed and in relation 

 to the resonant circuit they constitute the major portion of the effective 



Yg (SEE EQ. 2.t) 

 2 ! 2 



r 

 u 



-*-" r^ ^C 



NODES I AND 2 

 CORRESPOND TO 

 GRIDS BOUNDING 

 INTERACTION GAP 



Y (SEE EOS. 2.3 AND 2.4) 



Fig, 3. — Equivalent circuit of single resonator reflex klystron. 



shunt capacitance. Based on these remarks, it should be apparent that 

 a single-resonator reflex klystron may be represented by an equivalent 

 circuit consisting of a parallel combination of Ye , C, G, and L as shown 

 in Fig. 3. Furthermore, the expressions for Ye and Y as given by equa- 

 tions 2.1 and 2.4, respectively, show that these two quantities are inde- 

 pendent of each other. The electronic admittance, Fe , is a function of 

 the electron optics of the tube, while the passive circuit admittance, F, 

 is a function purely of cavity parameters, including the tightness of 

 coupling to the external load. 



2.4 Performance Analysis Based on Complex Admittance Plane Rep- 

 resentation 



The condition for oscillation applying to the equivalent reflex klystron 

 circuit requires the total admittance across nodes 1 and 2 of Fig. 3 to 

 equal zero, i.e.. 



r. + F = 0, 



2.5a 



