The properties of the local coupling impedance that determines the efficiency of the electron–wave interaction in periodic slow-wave structures are investigated. This impedance is determined (i) through the characteristics of the electromagnetic field in a slow-wave structure and (ii) through the parameters of a two-port chain simulating the structure. The continuous behavior of the local coupling impedance in the passbands of slow-wave structures, at the boundaries of the passbands, and beyond the passbands is confirmed with the help of a waveguide–resonator model.
The transmission of а complex signal through nonlinear structures (semiconductor diodes, high-power transistor amplifiers, microwave vacuum amplifiers, ets.) is investigated by means of quasi-stationary method, and functional models of devices are applied. The models use the quasi-stationary method of analysis of multifrequency signal transformation. Certain properties and peculiarities that are exhibited by nonlinear devices and that induce so-called spectrum multiplexing, i.e., formation of combination components, including those observed within the basic spectrum, are considered. The possibilities of spectrum multiplexing in nonlinear elements with a polynomial quadratic, cubic, or more complicated characteristic are discussed.
A design of a band-stop frequency-selective surface based on a planar mushroom-shaped metamaterial with an electronically tunable stopband has been proposed and investigated. The results of numerical simulation and experimental measurements of the parameters of a finite section of the metamaterial with mounted varicaps are presented. These results illustrate the shift of the structure stopband occurring simultaneously with a change in the capacitance of the lumped elements. Frequency dependences of the inherent dielectric parameters have been obtained. They indicate the presence of negative values of the effective permittivity and effective permeability of the proposed structure and the presence of the surface impedance that significantly exceeds the free-space characteristic impedance and is frequency-tunable.
Methods for extension of the rejection band of microwave devices on the basis of planar modified mushroomshaped metamaterials comprising either twolayered topological structures with frequencyselec tive surfaces or multilayer bulk structures with intermediate layers containing splitring resonators are pro posed. Computer simulation of such devices, clearly demonstrating a two to sixfold extension of the rejec tion band is performed. Experimental results confirming the results of numerical simulation are presented.
A numerical simulator of the interaction processes in helical traveling-wave tubes is developed on the basis of the method of large particles in the 1D approximation with the use of the calculation methods developed previously. The output characteristics (frequency dependences of the output power and gain factor) of high-power traveling wave tubes based on helical slow-wave structures for operation in the C and Ku wave bands are studied theoretically and experimentally. It is shown that the results of numerical simulation are in satisfactory agreement with experimental data.
The electrodynamic characteristics of the helical slow-wave structure of a high-power pulse traveling-wave tube operating in the centimeter wavelength range are calculated by means of the solution of the dispersion equation and simulation. Special attention is focused on the effect of a helix wire profile on the electrodynamic characteristics of the system. The results of the theoretical study are compared with the experimental data.
A linear theory of the discrete interaction of electron beams and electromagnetic waves in slow-wave structures (SWS) is developed. The theory is based on the finite_difference equations of SWS excitation.The local coupling impedance entering these equations characterizes the field intensity excited by the electron beam in interaction gaps and has a finite value at SWS cutoff frequencies. The theory uniformly describes the electron–wave interaction in SWS passbands and stopbands without using equivalent circuits, a circumstance that allows considering the processes in the vicinity of cutoff frequencies and switching from the Cerenkov mechanism of interaction in a traveling wave tube to the klystron mechanism when passing to SWS stopbands. The features of the equations of the discrete electron–wave interaction in pseudoperiodic SWSs are analyzed.
The effect of space charge on the decisions of the previous universal characteristic equation of electron waves, respectively, and the gain in the traveling-wave tubes (TWT) with periodic slow-wave system (SWS). The main attention is paid to the features of the gain of the electron waves in comparison with the results of the theory of J. Pierce is valid only for the TWT with "smooth" SWS.
The self-excitation of electron generators based on the flows of nonlinear excited oscillators obtained by a centrifugal electrostatic focusing is analyzed. The possibility of the master–slave synchronization of the generators is demonstrated. It is shown that the mutual synchronization leads to the narrowing of the spectral line.
The finitedifference theory of excitation of periodic waveguides is used to derive the characteris tic equation for electron waves formed during interaction of an electron beam with forward and counter propagating electromagnetic waves of periodic waveguides (slowwave structures). The derived characteristic equation describes interaction of electrons and waves in passbands and stopbands of periodic waveguides and contains known solutions for “smooth” slowwave structures and resonator slowwave structures near cutoff frequencies as particular cases. Several analytical solutions allowing comparison of amplification and propa gation properties of electron waves inside and at the edges of passbands and stopbands of periodic waveguides are found.