| Owing to the advantages of low loss, nice anti-interference performance and large power capacity, traditional metal tube waveguides are wildly used in communication and radar systems. With the development of technologies and the change of demands, higher requirements of compactness, mobility and concealment are put forward for these systems. However, the volume and weight of waveguide are often in contradiction with these requirements, and may even become the bottleneck in the overall design in some cases. Naturally, the miniaturization technologies of waveguide are the key to resolve these problems. Nevertheless, the existing technologies mainly focus on changing of transmission characteristics of waveguide, and there are still problems when applied in some cases. Thus, based on a different idea which focuses on the improvement of the structure, a series of novel miniaturized folded waveguide power dividers are studied in this paper."Folded"refers to bending or cascading the branch waveguides, aiming at minimizing the stretching directions of the dividers, improving the space utilization efficiency, and further the miniaturization of the overall waveguide network. Practice shows that folded waveguide power dividers are effective miniaturization technologies, which are of great significance.The background and development of waveguide miniaturization technologies are first outlined. Some commonly used waveguide power dividers are then discussed. The analysis and design methods for power dividers including full wave analysis and equivalent circuit analysis are introduced. Based on variational method, an expression for the scattering parameters of a coupling slot with finite wall thickness in waveguides is derived. The equivalent circuits together with parameter extraction methods of coupling slot and E-step in waveguides are presented.Subsequently, a novel quasi one-dimensional waveguide H-Junction is proposed, which will significantly limit the structure of waveguide feeding network within a quasi one-dimensional direction and improve the space utilization efficiency to realize miniaturization. Considering the structure and equivalent circuit of H-Junction, E-steps are introduced which will extend the bandwidth of input matching up to 3 times as before. Based on variational method, the scattering parameters of coupling slot with finite wall thickness are obtained, and balanced incident waves are employed within the process for simplification. Combing equivalent circuit analysis and full wave analysis, a hybrid design method for H-Junction is presented, which can achieve precise results with less computation. Besides, a 1-to-4 and a 1-to-8 waveguide feeding network based on H-Junction are presented. Experimental results show that H-Junction, the 1-to-4 network and the 1-to-8 network can achieve a relative bandwidth of 14%, 12.6% and 8.4% , and a insertion loss of 0.25dB, 0.5dB and 0.65dB, respectively, which indicates fine performances.On the basis, H-Junction is applied to ridged waveguide power dividers and feeding networks. Besides, the U-N transformer, ridged-rectangular waveguide transformer, and ridged-waveguide-microstrip transformer are studied and verified by experiments. With these transformers, a 1-to-4 and a 1-to-16 ridged waveguide feeding network based on H-Junction are presented. Experimental results show that ridged waveguide H-Junction and the two feeding neitwork achieve a relative bandwidth of 13.3%, 13.3% and 9.1%, and a insertion loss of 0.35dB, 0.6dB and 0.9dB, respectively, which indicates fine performances.Finally, a novel low profile waveguide magic Tee is proposed. The magic Tee can be decomposed to an E-plane H-Junction and an H-plane folded T-Junction. The characteristics of H-plane folded T-Junction as well as the whole magic Tee are studied. Experimental results show that low profile magic Tee can achieve -20dB port matching as well as isolation within the working band. Based on the results, possible future improvements are given. |
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