Research And Design Of Composite Hybrid

In the communications industry, 3d B hybrid and directional couplers, as a power distribution and synthesis of passive components, have a very wide range of applications. Especially in today’s high-speed development of 3G and 4G networks, in order to achieve more input and output ports, the demand for the hybrids of more ports is the growing,while the technological requirements are also increasing. There are a lot of bridge implementations, such as coaxial, microstrip, stripline, rectangular waveguides and so on. However in order to carry a higher power and passive intermodulation, a more special stripline structure which medium is the air whose dielectric constant is 1 is used in the bridge and the directional couplers in this paper.As the hybrid of four input and four output designed in the paper is based on 3dB hybrid which is also a kind of directional coupler, parallel coupled-line directional coupler’s network ports are analyzed by odd-even mode analysis and the scattering matrix of obtained directional coupler are reversed at first. Then, based on the parallel coupled lines, asymmetric multi-section and symmetric multi-section 3dB hybrid working in 800-2500 MHz are designed. In the design of hybrids, they both achieve miniaturization of production by adopting varying pitched design approach and improve the isolation and VSWR by optimizing the length of the transition section and introducing compensating shunt capacitances in a number of cross-sections of coupled.In order to achieve miniaturization and convenience conductor processing, the design of 4x4 hybrid is chose to be based on the asymmetric 2-section by contrast. However, there are two problems in the design. Firstly, as the long length of the coupling conductor, the current method cannot support the entire conductor pieces at the same level. Secondly, due to the long length and much bend of the coupling conductor, the processing of the conductor is too difficult. Actually, for the first problem, it is solved by replacing the rods with the blocks and slotting at the bottom and the top of the cavity to fix the blocks. For the second problem, it is solved only by giving up the original conductor thickness and choosing a new size.In order to increase the awareness of the cavity directional coupler, in the end of this paper, several coupling directional couplers working in 800-2500 MHz are designed with shielded coupling structure. In the design of the directional coupler, three-dimensional model is built in HFSS to realize the parity mode impedance. While in order to achieve adjustability, it is usefule by using the side tuning screw.