The Researchand Designofminiaturized High Power Waveguide Directional Coupler

The directional coupler is a very important device in the microwave measurement. When measuring high power microwave, a high power weak coupling of directional coupler is needed. The size of aperture is smaller with the weaker of the coupling. But if the aperture is too small, it will decrease the peak power of the directional coupler. We can solve the contradiction between weak coupling and high power in multi-stage coupling way.But the volumes of multi-stage directional couplers are usually big. To solve these problems, we put forward a new kind of high power, miniaturization, weak coupling of rectangular waveguide directional coupler. Mainly as follows:1. Rectangular waveguide directional couplerscouple the microwave power through the aperture on the common walls. So we study the theory of couplingaperture, and deduce the coupling formula. In order to increase the peak power, introduce the two-stage coupling way, and make sure what task each stage directional coupler should undertake. The task of coupling of the whole directional coupler is undertakenbythe first stage and the second stageof directional couplers, while directivity is only undertaken by the first stage directional coupler.2. Research of the scheme of the first stage directional coupler, the first stage directional coupler should be the multi-aperturesrectangularwaveguideto rectangular waveguide directional coupler. Deduce the circle apertures, elliptic aperturescoupling calculation formulas in detail and build models by CST software respectively. If the two kinds of aperture directional coupler want to achieve the same indicators, elliptic apertures need fewer by comparing with circle apertures. In order to realize miniaturization, we design the first stage waveguide to waveguidedirectional coupler which has double rows 6 elliptic apertures, of which coupling is-25 d B eventually.3. Research of the scheme of the second stage directional coupler, the second stage directional coupler should be rectangular waveguide to stripline which consists of one aperture. I introduce the diamond long narrow gap、narrow slot schemes,build models by CST software and get simulation results. Considering the peak power, manufacturing process, and miniaturization, we design the second stage rectangular waveguide to striplineone narrow slot directional coupler,of which coupling is-25 d B eventually.The auxiliary line of the second stage directional coupler is vertically connected with the standard coaxial N type connector. We test the second stage directional coupler and get the measuring results which satisfy with project indicators.4. Considering the restricted condition of the manufacture, we design the two-stage directional coupler,of which coupling is(-49.4—-50.5)d B, directivity is under-25 d B.Theoretically the peak power is exceed 3.5MW. The measured results of the new two-stage directional couplermeet the technical index.