A.Yu. Miroshnichenko – Dr.Sc.(Eng), Associate Professor, 

Head of Departament «Electronic Instruments and system engineering», Yuri Gagarin State Technical University of Saratov E-mail: alexm2005@list.ru

V.A. Tsarev – Dr.Sc.(Eng), Professor, 

Department «Electronic Instruments and system engineering», Yuri Gagarin State Technical University of Saratov E-mail: tsarev_va@mail.ru

N.A. Akafyeva – Ph.D.(Eng), Associate Professor, 

Department «Electronic Instruments and system engineering», Yuri Gagarin State Technical University of Saratov

E-mail: akafieva_na@mail.ru

One of the relevant directions of development of the modern vacuum microwave devices is creation of the small-sized multi-beam klystrons (SMBK) working in a short-wave part of the microwave range. However during increase frequency, the output characteristics of SMBK such as frequency band, gain factor, an output power and efficiency are worsen as they directly depend on electrodynamic properties of resonators. Therefore, so-called, the photon crystal resonators known in foreign literature as Photonic Band Gaps structures (PBG) have investigated recently. New, useful properties (for example, increase a characteristic impedance and Q-factor, reduction of weight and dimensions) can be received in the double-gap photon crystal resonators due to introduction to a strip resonant element, located in the central area of defect, additional fractal elements like «Greek cross». Nowadays electrodynamic properties of such resonators, for using in MMBK, were practically not investigated. Results of a research of electrodynamic and electronic parameters of new double-gap fractal crystal resonators for the small-sized multi-beam klystrons working in C-, X-and Ku-frequency ranges are presented in this article. The interaction space of the resonator is located in the defect formed by a lattice of metal rod stock of round shape. They are established on rectangle perimeter. In a lengthwise direction the space of interaction is limited to side covers which are established from each other. The holes for a passage of a multi-beam electronic stream are executed in covers. In the central part of three-dimensional defect on the suspended dielectric substrate (executed from a dielectric with the relative inductivity ε=5.7), the central electrode with holes for a passage of 19 electron beams is placed. The resonator contains half-wave or quarter wave strip resonant line with fractal elements like «Greek cross» placed on a ceramic substrate. During the model operation for each of these options three designs of the resonator with the quasi-fractal resonant conductor of zero, first and second iteration were investigated. In this work the key electrodynamic and electronic parameters were determined also. The possibility of adjustment for the multiple resonant frequencies for the resonator with a quarter wave resonant strip conductors was studied. The practical recommendations were developed about the choice of optimum parameters of resonators designs which can be used when developing the small-sized multi-beam klystron devices working as amplifiers, generators or frequency multipliers.

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