Siw Transition
Microstrip, Stripline, and CPW Design
Iulian Rosu, YO3DAC / VA3IUL, http://www.qsl.net/va3iul
In the first years of microwave development the Rectangular Waveguide become the dominant waveguide structure largely because high-quality components could be designed using it. One of the main issues was its narrow bandwidth due to the cut-off frequency characteristic. Later, researchers try to find components that could provide greater bandwidth and possible miniaturization, and therefore they examined other waveguide types. Ridge Waveguide offered a step in that direction, having one or more longitudinal internal ridges that serve primarily to increase transmission bandwidth by lowering the cut-off frequency. Coaxial Line was very suitable, since it possessed a dominant mode with zero cut-off frequency, providing two important characteristics: very wide bandwidth, and the capability of miniaturization. The lack of a longitudinal component of field, made it more difficult to create components using it, although various novel suggestions were put forth. In addition, those components would be expensive to fabricate. In an attempt to overcome these fabrication difficulties, the center conductor of the coaxial line was flattened into a strip and the outer conductor was changed into a rectangular box, and then fitted with connectors for use with regular coaxial line. At about the same time, Robert M. Barrett when working for the Air Force Cambridge Research Center in 1950s took a much bolder step. He removed the side walls altogether, and extended the top and bottom walls sideways. The result was called strip transmission line, or Stripline. Like coaxial cable, Stripline it is non-dispersive, and has no cut-off frequency. Different methods were used to support the center strip, but in all cases the region between the two outer plates was filled with only one single medium, either dielectric material or air. A modification that emerged almost in the same time involved
Iulian Rosu, YO3DAC / VA3IUL, http://www.qsl.net/va3iul
In the first years of microwave development the Rectangular Waveguide become the dominant waveguide structure largely because high-quality components could be designed using it. One of the main issues was its narrow bandwidth due to the cut-off frequency characteristic. Later, researchers try to find components that could provide greater bandwidth and possible miniaturization, and therefore they examined other waveguide types. Ridge Waveguide offered a step in that direction, having one or more longitudinal internal ridges that serve primarily to increase transmission bandwidth by lowering the cut-off frequency. Coaxial Line was very suitable, since it possessed a dominant mode with zero cut-off frequency, providing two important characteristics: very wide bandwidth, and the capability of miniaturization. The lack of a longitudinal component of field, made it more difficult to create components using it, although various novel suggestions were put forth. In addition, those components would be expensive to fabricate. In an attempt to overcome these fabrication difficulties, the center conductor of the coaxial line was flattened into a strip and the outer conductor was changed into a rectangular box, and then fitted with connectors for use with regular coaxial line. At about the same time, Robert M. Barrett when working for the Air Force Cambridge Research Center in 1950s took a much bolder step. He removed the side walls altogether, and extended the top and bottom walls sideways. The result was called strip transmission line, or Stripline. Like coaxial cable, Stripline it is non-dispersive, and has no cut-off frequency. Different methods were used to support the center strip, but in all cases the region between the two outer plates was filled with only one single medium, either dielectric material or air. A modification that emerged almost in the same time involved
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