1. Field of the Invention
The present invention relates to a radio frequency (RF) coupler; in particular, to a tunable RF coupler and manufacturing method thereof.
2. Description of Related Art
In recently years, the popularization of the wireless communications product brings more convenience and digitization to people's life. With the increase in the demands of the market and the development of the manufacturing technique, the requirements of the integrated circuit design are changed. Especially in wireless communication field, the circuit designs of receiving port and emitting port would be greatly concerned.
Typically, the front-end module usually includes a RF coupler. A signal through the RF coupler would be received and processed by a back end circuit such as power detector. During the design process of the RF coupler, the appropriate simulations for the band and the coupling of the signal through the RF coupler would be made by the circuit designer, and the circuit layout is determined according to the results of the simulations. Subsequently, after the factory finishes the manufacture of the RF coupler, the RF coupler would be tested by the circuit designer to check whether the characteristics of the RF coupler satisfy the demands of the circuit designer. However, when the characteristics of the RF coupler do not satisfy the demands, for example, the coupling or the desired directivity is not achieved, the circuit designer needs to redesign the circuit layout of the RF coupler, and scrap the RF coupler with poor characteristics, which leads to waste of the resource.