Properties of Helical and Serpentine Slow-Wave Systems Containing Dielectric Holders

Abstract

The helical and serpentine structures, containing periodical inhomogeneities, caused by dielectric holders, are considered in order to reveal the influence of the inhomogeneities on the properties of the structures at high frequencies. The method of multiconductor lines is used for analysis of the systems. The proposed models of the systems consist of segments of the shielded multiconductor line, containing one row of conductors and one conductor in the period of the structure. Capacitive inhomogeneities are modeled by lumped capacitances. Dispersion equations and expressions for the input impedance of the systems are derived. They are used for calculations of retardation factor and input impedance versus frequency. It is shown, that periodical inhomogeneities decrease the pass band of the helical and serpentine systems. The inhomogeneous systems obtain properties of the rejection filter in the high frequency region. The inhomogeneous helical system obtains properties of the rejection filter, when the phase difference angle θ between the voltages or currents on the neighbor helical wires approaches π . The width of the stop-band depends on the ratio of the capacitances, modeling inhomogeneities, and the distance between them. It is important that there is possibility to decrease and to move the stop-band to almost twice higher frequency range when mentioned ratios become 1. In the case of the traveling-wave deflection systems, the stop-band is higher than the upper limit of the pass-band of the traveling-wave cathode ray tube. On the other hand, designers of the super-wide-band traveling-wave deflection systems and traveling wave cathode ray tubes must take into account revealed influence of the periodic inhomogeneities on the properties of the slow-wave structures. It is possible to improve properties of the deflection systems using two or more uniform holders with the same distance between them instead of one. The influence of the periodical capacitive inhomogeneities on the properties of the serpentine systems is different. The first stop-band appears in the lower frequency range (when θ ≅ π / 2 ), and it is impossible to avoid it by decreasing the distance between the capacitances, modeling holders. The position of the stop-band depends on the period of the serpentine conductor 2h . Ill. 8, bibl. 13 (In Lithuanian, summaries in Lithuanian, English, Russian).