MAGNETRON AS GENERATOR OF CENTIMETER WAVES 



179 



the RF ikld changes little. Thus it is possible by api)lying DC potential 



differences between the anode segments to measure a negative resistance 



between them. As can be seen from the orbits of Fig. 6, magnetic fields 



considerably above the cut-off value are used. With magnetrons of this 



type, power output up to 100 watts at 600 mc/s at an efficiency of 25% has 



been attained.'' Oscillations of frequency as high as 1000 mc/s, (30 cm.) 



have been produced.^ Because a large number of orbital loops are required, 



eB 

 however, making co « — , this t\-pc of magnetron oscillator demands the 

 m 



+ 150 VOLTS 



+ 150 VOLTS 



ELECTRON 

 PATH 



+50 VOLTS 



Cb) 



Fig. 6. — Electron paths plotted by Kilgore for the negative resistance magnetron 

 oscillator, Type I. During the time the orbits shown are being executed, the cathode is at 

 zero potential and the anode segments at the potentials indicated. Lines of electric force 

 on an electron are plotted in this figure. The two orbits are those of electrons which start 

 initially toward opposite anode segments. It should be noted that in either case the elec- 

 tron is driven to the segment of lower potential against the RF field component. 



use of high magnetic field in the centimeter wave region and is thus less 

 desirable than other types. 



2.3 The Cyclotron Frequency Magnetron Oscillator— Type II: Not long 

 alter the invention of the DC magnetron, oscillations between anode and 

 cathode were found to occur near the cut-off value of magnetic field.^ 

 These were found to be strongest for wavelengths obeying a relation of 

 the form: 



X = 



constant 



B 



(9) 



« E. C. S. Megaw, Journ. I.E.E. (London) 72, 326 (1933). 

 9 A. Zacek, Cos. Pro. Pest. Math, a Fys. (Prague) 53, 578 (1924). 

 in Zeit. f. Hochfrequenz. 32, 172 (1928). 



A summary api^eared 



