MAGNETRON AS GENERATOR OF CENTIMETER WAVES 239 



power contour the frequency of the magnetron varies linearly with Bi^ as 

 equation (37) indicates. Hence any constant frequency contour on the 

 diagram is obtainable from a neighboring contour of different frequency 

 through translation in the direction oi Bt by an amount given by equation 

 (37). The form of the contours of constant frequency depends upon the 

 interdependence of the electronic parameters Ge and Be . The fundamental 

 electronic performance as a function of load is specified by the conductance 

 Gs presented to the electrons at the anode slots, changes in load susceptance 

 being compensated for by frequency changes and hence susceptance changes 

 in the resonator. As Gl is varied Gg , Ge , and the output power must 

 vary as well. If Be is independent of these changes the constant frequency 

 contours will correspond to lines of constant Bl . Actually it is found that 

 Be does depend to some extent on Ge , resulting in the constant frequency 

 contours on the Gl — Bl plot being approximately straight lines inclined to 

 the constant Bl lines at a small angle a as shown in Fig. 32 (a). 



If the Gl — Bl plane is transformed to the reflection coefficient or r plane 

 on which the load characteristic is usually plotted, contours of constant 

 Gl or power become circles tangent to the circle p = 1 at the same point. 

 Constant Bl contours form the set of circles orthogonal to these. The 

 contour of constant frequency of Fig. 32 (a) transforms to a circle which 

 intersects all the contours of constant power at the angle a. 



Fig. 32 (b) is thus the form of the characteristic depicting the dependence 

 of magnetron performance on load, called the Rieke diagram, plotted for 

 that point in the equivalent circuit where the admittance looking out into 

 the load is Y l = Gl -\- JBl . Between this point and a point in the smooth 

 output line, with respect to which the load admittance is usually measured, 

 there is the series reactance Xo and the output circuit of the magnetron, 

 forming a transducer through which the reflection coefi&cient defining the 

 load admittance may be transformed by the expression (31). In under- 

 going such a transformation the contours of constant power and frequency 

 plotted on the r plane retain their general form although they may be ro- 

 tated and expanded or contracted. Thus the general form of the Rieke 

 diagram shown in Fig. 32 (b) should be the same as that experimentally 

 determined and plotted on a reflection coefiicient plane for a point in the 

 output line. Fig. 33 is such a Rieke diagram and its resemblance to that 

 of Fig. 32 (b) is apparent. 



9.3 Magnetron Circuit Parameters: The fact that the circuit theory of 

 the magnetron based on the simple equivalent circuit of Fig. 31 (a) explains 

 the nature of the Rieke diagram so well is ample justification for its use. 

 The parameters which specify the equivalent magnetron circuit may be 



