Research And Design Of The Novel Broadband High Power Waveguide Directional Coupler Based On S-Band

Directional couplers are widely used in many fields which are related to microwave. The development of technology is putting higher requirements for directional couplers with broadband and higher power capacity. Waveguide structure, with its large power capacity and simple processing process, has become the basis structure of high power directional couplers. At the same time, the ridge waveguide, with its broad dominant band and higher cutoff wavelength, has become one of the effective methods to improve the working bandwidth of the couplers. In this article, in consideration of the high power capacity and the working bandwidth, three different kinds of directional couplers, each of which consists of two different transmission lines are studied and designed in S-Band. The main work of this paper can be summarized as followings:1. The structures, types, bandwidth and capacity of directional couplers are researched; The properties of different waveguide structures, such as the Rectangular waveguide, the Single-Ridged waveguide, the Single T-Septum waveguide and the Circular-Ridge waveguide have been briefly analyzed; The key parameters and the design principle of directional couplers have been studied.2. The Rectangular-Ridged waveguide directional coupler in which the coupling area lays on the broad side has been designed. Two kinds of auxiliary transmission lines, respectively, the Single-Ridged waveguide and the STSG (Single T-septum Guide) are used in the design. The distance between the coupling hole and waveguide wall, the different holes shapes (square holes, triangle holes, round holes) and the parameters of the T-Septum can greatly affect the coupling coefficient and the directivity of the couplers. The square holes are proved to have higher bandwidth than the other two kinds of holes and different T-septum parameters will affect the coupling flatness and coupling value. The new designed directional couplers are proved to have broader bandwidth than the traditional ones.3. The Rectangular-Circular ridged waveguide directional coupler in which the coupling area lays on the narrow side has been designed. The number and location of the additional ridges in the circular waveguide have large effect on the coupling coefficient. What’s more, four kinds of different holes distributions, namely, the Equivalent Round Hole distribution, the Chebyshev Hole Distribution, the Equivalent Square Hole distribution and the Equidifferent Square Hole distribution are studied. Different hole distribution will lead to different coupling property.4. The power capacity of the directional couplers mentioned above is evaluated when the maximum input power is 60KW.