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BELL SYSTEM TECHNICAL JOURNAL 



oscillates as a self excited oscillator whenever the DC voltage is applied. 

 The energy available at the output circuit may be connected, as in a radar 

 set, to an antenna or, as in a laboratory experimental setup, may be absorbed 

 in a column of water. 



1.2 Analogy to Other Oscillators: In its fundamental aspects, the mag- 

 netron oscillator is not unlike other and perhaps more familiar oscillators. 

 In particular, instructive analogies may be drawn between the magnetron 

 oscillator, the velocity variation oscillator, and the simple triode oscillator. 

 In Fig. 2 is depicted schematically the parallelisms between these types of 

 oscillators and a simplified equivalent lumped constant circuit. 



In the triode of Fig. 2(a), as in the gap of the second cavity of the velocity 

 variation tube of Fig. 2(b) and in the interaction space of the magnetron 



Fig. 1. — A schematic diagram designed to show the principal component parts of a 

 centimeter wave magnetron oscillator. The resonator system and output circuit each 

 represents one of several types used in magnetron construction. 



oscillator of Fig. 2(c), electrons are driven against RF fields set up by the 

 resonator or "tank circuit," to which they give up energy absorbed from the 

 primary DC source. In each type of oscillator there is operative a mecha- 

 nism of "bunching" which allows electrons to interact with the RF field 

 primarily when the interaction will result in energy transfer to the RF field. 

 In the triode oscillator this is accomplished by the grid, whose RF potential 

 is supplied by the "tank circuit" in proper phase with respect to the RF 

 potential on the anode. In the velocity variation oscillator, bunching is 

 accomplished by variation of the electron velocities in the gap oi the first 

 cavity, followed by drift through the intervening space to the second gap. 

 The first cavity is driven in proper phase by a feed back line from the second 

 cavity. In the magnetron oscillator, as is to be described in detail later, 

 electron interaction with the RF fields is such as to group the electrons into 



