This letter presents novel composite dual-transmission lines. The proposed line consists of one direct series line and two identical transmission lines connected by a series lumped capacitor. The line is analyzed with an even-odd mode analysis method to have simple closed-form design equations. From the design equations, it is also observed that one can maintain a more realizable value of the impedance of the lines and achieve a good amount of miniaturization by adjusting only the lumped capacitor. To verify this technique, a 74.6% miniaturized Gysel power divider (GPD) is designed at 0.95 GHz compared to reference GPD. The physical size of the proposed GPD is 60 mm × 32 mm (equivalently 0.25λg × 0.13λg, λg is guided wavelength line). Moreover, two transmission zeros (TZs) are obtained near passband which improved the out-of-band performance.
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