A TRI-BAND IMPEDANCE TRANSFORMER USING STUBBED COUPLING LINE

In this paper, a compact tri-band impedance transformer by utilizing stubbed coupling line for matching a load at three arbitrary frequencies is proposed. The transformer is composed of two parts, and each part is constructed from parallel-coupled transmission lines. Two structures with different configurations of the proposed transformer have been given and analyzed. Then, the close-form equations for the transformer parameters are derived analytically, and the corresponding analytical design approach is verified by numerical examples. To certify the validity of design formulas, an impedance transformer is fabricated and measured at 0.9/1.8/3.2 GHz. Good experimental performances at each frequency are obtained, which are in good agreement with the simulated results.