A Wideband 90^∘ Phase Shifting Element Applied in Quadrature Phase Filtering Power Divider

A wideband 90^∘ phase shifting element for application in the quadrature phase filtering power divider (QFPD) is presented in this letter. Instead of the complex calculation procedure of phase information between reference and main branch in traditional phase shifter design, this letter initially reveals the inherent property of 90^∘ phase difference between terminal open-and short-circuited transmission lines (TLs) by investigating their respective electric field distributions. Following this concept and conventional filtering design method, a new topology of QFPD is constructed. For demonstration, a design example of wideband QFPD is implemented and measured. Results show that the proposed wideband QFPD exhibits phase bandwidths of 69.24%, impedance bandwidths of 58.68%, and magnitude imbalances of less than 0.7 dB, together with better than 20 dB isolation performances.