Study Compact Waveguide Directional Coupler

Directional coupler is widely used as a power divider. Over the past few years, due to the progress of the processing technology, makes the directional coupler become the irreplaceable component in a communication system. Directional coupler plays a different role in different circuit. For example, in the passive circuit, it is used as filter or matching network. In the active circuit, it is used as phase shifter, balanced amplifier, mixer circuit.Directional coupler is researched by domestic and overseas, it is the development of more mature in recent years. Among them, because of its small size, good performance, the advantages of easy processing, makes the microstrip line and stripline directional coupler with the swift and violent development, and they have various types, these type of coupler is relatively common. But this kind of coupler has an obvious flaw, that is to withstand the power of the generally low. Compared with the waveguide directional coupler, the waveguide directional coupler can work under high power, relatively wide frequency band becomes an obvious advantage of the latter, so that the latter is often selected to used in large power system. In the process of writing this paper, we are to learn the basic theory of the directional coupler for the premise, to analyze the specific waveguide directional coupler as the main content, and ultimately to achieve the purpose is to design a waveguide directional coupler is better than traditional one, so it can be widely used in the actual production.The common coupling forms of Directional coupler are the circular holes, elliptical holes and rectangular aperture coupling. For other forms of coupling research is less. To design a within the wide band, low insertion loss, stable coupling and high directivity waveguide coupler, requires that the coupling hole size compared with the wavelength is not too big. So for the round hole coupling of the directional coupler, it need a lot of holes, even if this does not necessarily can meet the design requirements. Again because of the distance between adjacent coupling hole is a quarter waveguide wavelength, so, this makes the design of the size of the coupler is very big, it can’t reach a wide range of practical application. If at high frequency, and the coupler has the characteristics of low insertion loss, only the cross slot coupling structure can meet the design requirements. So in this paper, based on the traditional theory of waveguide directional coupler, the unusual cross slot coupling structure on the market is used for our research design. At the same time, we use computer simulation software CST discuss model, discussing the model parameters change caused the change of the coupler performance, through the analysis and comparison. Finally, the optimal value of the parameter are selected in model, and the performance of the coupler is made to reach our design requirements: compact structure, wide working frequency band, low insertion loss, flat coupling, good directivity and so on.Any device design should be applied to the actual production in the life, and it can be detected. So finally we design this kind of double cross slot waveguide directional coupler for processing, through the physical test, it is proved that its performance is better than similar products. Therefore, we can conclude that this paper designed directional coupler can have very good market prospects for development.