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BELL SYSTEM TECHNICAL JOURNAL 



be discussed in some detail. From an analysis of this circuit it will be ex- 

 plained how the power which the magnetron delivers and the frequency at 

 which it oscillates depend upon the load attached to it. 



Consider now the equivalent circuit shown in Fig. 2, or as repeated in 

 Fig. 31 (a). Since the N cavities of which the magnetron resonator system 

 is composed are essentially in parallel for the tt mode, the C of the equivalent 



. 1 . 

 circuit is N times the capacitance and the -^ is ^ times the inductance of a 



single cavity. Ge is the shunt conductance representing the series resistance 



M 



1 O 1 



c 



D 



(0) 



IDEAL 

 •TRANSFORMER 



(b) 



(c) 



Fig. 31. — A diagram showing an equivalent RF circuit for the magnetron oscillator, (a), 

 and how this circuit may be reduced in two steps, {b) and (c), to a simpler form. 



in the copper walls of the resonator system, Lo , the inductance of the out- 

 put loop which is coupled by the mutual inductance, M, to the lumped in- 

 ductance of the equivalent resonating circuit. Z^ represents the impedance 

 of the load at the loop terminals. Thus it represents the load impedance 

 to which' the magnetron is attached, transformed through the output circuit 

 to the loop terminals. 



The first step in understanding the circuit of Fig. 31 (a) is to reduce it to 

 a simpler form. This is done in two steps as shown in Fig. 31. The induc- 

 tances L and Lo , with mutual inductance M between them, form a trans- 

 former through which the impedances in the secondary circuit, jcoLo and 



