Rapid Diplexer Design for High Isolation of Fundamental and 2 nd -Harmonic Spectrums

A novel diplexer is rapidly facilitated with integration of a hybrid coupler and two quarter wavelength short stubs, which enables high isolation of its fundamental and 2nd-harmonic spectrums while sustaining the original directionally-coupling operation characteristic. For practical validation, a microstrip diplexer ($\varepsilon_{\mathrm{r}}=3.66,\ \mathrm{h}=0.508\ \text{mm}$) operat...