Method for calculating the properties of coupled-cavity slow-wave structures from their dimensions

Abstract

In the development of computer models of coupled-cavity travelling wave tubes, it is necessary to have some means of calculating the properties of the slow-wave structure. Direct calculation is difficult because of the complexity of the shapes involved. One possible method makes use of the equivalent circuit representation of the slow-wave structure. In the paper it is shown that the parameters of the equivalent circuit can be calculated from the dimensions of the structure. Once these parameters are known, it is very quick and easy to compute the phase change per cavity and the interaction impedance at any frequency. The results obtained by this method are compared with those of experiment and it is shown that useful accuracy can be obtained.

Analysis of Rectangular Folded-Waveguide Millimeter-Wave Slow-wave Structures using Conformal Transformations

“…Subsequently, from the TEM-wave consideration in the W-plane, the resonant wavelength of the structure is considered as twice the circuit length [11], and thus, at resonance, the lumped circuit inductance per period is expressed as:…”

“…Subsequently, using the expressions of inductance and capacitance per period of the structure, one can easily express the space-harmonic phase shift (β m ) and the interaction impedance (K) of the slow-wave structure following the approach of Carter and Liu [11] given as:…”

Improved equivalent circuit model of practical coupled‐cavity slow‐wave structures for TWTs

“…A slight variant of the Hughes structure, with staggered double slots and tapered or step-tapered ferrules, is used in wideband, high-gain tubes to improve bandwidth and impedance, and to reduce arcing problems. The space-harmonic CC-SWS has been analyzed using various techniques, such as transmission line theory [1], equivalent circuit model [2,3], modematching technique [4] and three-dimensional (3D) computer simulation codes [5][6][7][8]. However, to the best of our knowledge, an equivalent circuit model of a CC-SWS with staggered double slots and tapered or step-tapered ferrules is not available.…”

“…Equivalent circuit modeling of CC-SWS with single staggered slot and double in-line slots was reported by Curnow [2]. Carter and Shunkang [3] derived the equivalent circuit parameters of the coupled-cavity structure with cylindrical ferrules by its physical dimensions. Akhtar and Srivastava [9] attempted to treat a double-slot structure in the formulation of [3] by taking the slot angle as 4/3 times the angle of the single slot.…”

“…Carter and Shunkang [3] derived the equivalent circuit parameters of the coupled-cavity structure with cylindrical ferrules by its physical dimensions. Akhtar and Srivastava [9] attempted to treat a double-slot structure in the formulation of [3] by taking the slot angle as 4/3 times the angle of the single slot. But, the accuracy of results for the dispersion characteristics, as compared to results of 3-D MAFIA simulation for a C-band double-slot CC-SWS was only ϳ10%.…”