Design of Wideband Filtering Power Divider with Compact Size and High Isolation

Abstract

A compact wideband filtering power divider (FPD) with high isolation is designed based on a microstrip line (MSL) and coplanar waveguide (CPW) hybrid structure. By virtue of the broadside coupling, a three-port filtering network is wisely constructed with three parallel microstrip feeding lines and one CPW quarter-wavelength resonator. Then, to achieve the port-to-port isolation, a lumped resistor is loaded between the two ends of the output feeding lines. To explain the working principles of filtering and isolation, the even-/odd-mode analysis method is adopted. For demonstration, a prototype of wideband FPD operating at 2 GHz with a 3-dB fractional bandwidth of 100% is designed, fabricated and tested. Final circuit dimension is only 0.2 9λgXO.07λg, where λg is the guided wavelength at the center frequency. Measured results indicate that the proposed wideband FPD has achieved 18-dB return loss and 21-dB in-band isolation.