As electronics and information technologies advance rapidly, various communication and information products have been developed to meet daily requirements. For communication products, flange-mount SMA connectors are extensively used in the input/output ports of high-frequency components all over the world, and employed in the transitions between coaxial cables and planar transmission lines to facilitate the testing of the circuits assembled on the planar transmission lines.
Another application is related to system integration, which requires interconnections between different transmission lines, such as interconnections between a coaxial cable and a microstrip line, a coaxial cable and a coplanar waveguide, a coaxial cable and a waveguide, and a waveguide and a microstrip line. Among them, the interconnection between a coaxial cable and a microstrip line is the most common transition. To achieve successful signal transmission between these two transmission lines with minimum insertion loss, designs of their transitions become very important.
With reference to FIGS. 1A and 1B for the schematic views of a conventional flange-mount SMA connector and a transition between a coaxial cable and a microstrip line using this connector, respectively, the conventional flange-mount SMA connector 100 is a coaxial connector, which comprises an outer conductor 111, a mounting wall 120, a center conductor 130, and a dielectric material 122. The transition is mainly used for high-frequency testing setups or the input/output ports of high-frequency devices for signal transmission between a coaxial cable (not shown in the figure) and a microstrip line 140. In the design for the conventional transition, the center conductor 130 of the conventional flange-mount SMA connector 100 is connected to a signal line 142 on the substrate 143 of a microstrip line 140, and then the outer conductor 111, the mounting wall 120, and the ground plane 141 underneath the substrate 143 of the microstrip line 140 are electrically connected to achieve signal transmission between the two transmission lines.
With reference to FIGS. 2A and 2B for the electromagnetic field distributions in a coaxial cable and a microstrip line, respectively, their electromagnetic field distributions are different, which introduces insertion loss at the transition of these two transmission lines, and it becomes more severe as frequency increases. Thus, the 1-dB passband of the conventional transition is limited.
Therefore, the goal of the present invention is to provide a connector to reduce the insertion loss caused by the change of the electromagnetic field distributions of the two transmission lines at their transition.