High Directivity Microstrip Couplers for Impedance Transforming

The paper describes the design method and simulations of high directivity planar couplers for impedance transforming. Presented coulers are realized in microstrip line technology. The basic idea is making a coupling between two diffrent imepdance transmission lines at two points only. The coupling is realized by capacitors soldered to the beginning and the end of lines. The proposed couplers have narrow bandwidth and several levels of coupling and have been designded at frequencies 1.3 GHz and 3.0 GHz.