Balanced-to-unbalanced power dividers for arbitrary power division ratios and for arbitrary real termination impedances

Novel balanced-to-unbalanced power divider (BUPD) is introduced for arbitrary power division ratios and for arbitrary real termination impedances. It consists of one 180° transmission-line section (TL), two different 90° TLs and one isolation circuit comprising two different resistances and two different 90° TLs. Due to the arbitrary termination impedances, the conventional ways for the even- and odd-mode excitation analyses are impossible, requiring a new design method. Under the assumption of the perfect isolation between two output ports, the BUPD can be divided into two, based on which the design formulas for the characteristic impedances of all the TLs can be successfully derived. Then, the scattering parameters are inversely derived, which is quite different from the conventional ways where the design formulas are derived based on the scattering parameters. For the verification of the suggested theory, one prototype for the power division ratio of 5 dB and for the termination impedances of 60, 40  and 50 Ω is tested. The measured frequency responses are in good agreement with the predicted ones.