Conventionally, coaxial cables are used as connectors in transmission of high frequency signals or connection of different electronic communication products. However, since the coaxial cable connector is larger and occupies much space, it is difficult to be applied to a small-sized portable electronic device (such as a phone). On the other hand, since the architecture of the coaxial cable connector is fixed and is not easy to be changed, it is difficult to be customized for various products. Moreover, the manufacturing cost of the coaxial cable connector is high.
In addition, a coplanar waveguide technology is another common conventional high frequency signal transmission technology. The coplanar waveguide technology has a feature that it includes a single plane of transmission lines, that means, a signal line and a grounding line are in the same plane, which makes electronic components connected to each other in series or parallel easily. Moreover, the coplanar waveguide technology makes electric characteristic of the electronic components not easily affected by the thickness of a dielectric plate. Consequently, the manufacturing cost of circuits is greatly reduced, and a circuit layout has more choices.