For those interested in the nature of magnetron strapping,

the following information can be of significance




Cavities, pi-mode, B-mode, For the eight-cavity magnetron the n = 4 mode is the pi-mode and has the electric-field pattern in the interaction space is the pi-mode and has the electric-field pattern in the interaction space (space between cathode and the anode where the electrons and fields interact), The pattern of the next-simpler mode (n = 3) of eight-cavity magnetron is shown..., The n = 0 mode is not employed in a resonant-cavity magnetron because the fields of this mode do not enter the individual anode cavities, and thus the cavities do not control the frequency of the mode, ...two component modes are present simultaneously and the resultant pattern may take a variety of forms depending upon the relative amplitudes of the components, For example, for the n = 1 mode.. the pattern is rotated 90 deg if different pairs of anode segments operate in parallel..., An undesired mode causes interference with pi-mode operation if its frequency is very nearly equal to the frequency of the pi-mode, The field in the interaction space is consequently distorted from the pi-mode..., The impedance presented to the interaction space depends upon the ratio of the width of segments between adjacent cavities to the width of the cavity slots and this ratio must be kept reasonably low, Thus a large number of small cavities is required with the result that undesired modes occur at frequencies very near that of the pi-mode, Four methods of strapping....., Embedding the straps in the block-partially isolates the straps from the interaction space and thus minimizes the distortion in the interaction-field pattern caused by the presence of the straps..., The way in which straps influence magnetron operation may be explained in terms of additinal reactive elements they introduce into the resonator system.. because each strap can carry conduction current between the segments joined.. the strap has the effect of connecting the two segments through an inductance, Since a displacement current can also flow between a strap and a segment it passes over.. each strap is coupled to a segment through a shunt capacitance, In the pi-mode each strap joins segments that are at the same voltage so that only the shunt capacitance is important....., The combined effect of strap inductance and capacitance is to reduce the resonator inductance to increase its capacitance slightly.. with the net result of an increase in the lower order mode frequencies, As a result of strapping therefore the resonant frequencies of all modes are shifted in a manner that increases the separation between pi/mode frequency and the frequencies of all other modes, The extent to which strapping increases the frequency separation of the modes depends upon the strapping system used, Unwanted modes may be further suppressed by introducing an asymmetry into the strapping system.., In the absence of strap breaks degenerate modes may assume any angular position about the resonator axis.. because these modes normally take up a position that yields least coupling to the output circuit... strong oscillations in the modes are possible..


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